JP3779277B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing method and a plasma processing apparatus, and more particularly to a dry etching process in which a raw material gas in a gas phase is converted into plasma and the surface of a semiconductor material is processed by physical or chemical reaction of activated particles. It relates to plasma processing.
[0002]
[Prior art]
With the recent miniaturization of semiconductor elements, multilayer wiring layers and three-dimensional element structures are progressing. Accordingly, it is considered that the processing of the insulating film used for maintaining the electrical insulation between the wiring and the elements becomes more and more important. In the etching of this silicon oxide film, which is an insulating film, CF _Four , C ₂ F ₈ Perfluorocarbon gas (PFC) and CH ₂ F ₂ , CHF _Three Hydrofluorocarbon gas (HFC) such as has been used. This is because a gas containing carbon is indispensable for breaking the Si—O bond of the silicon oxide film and generating a volatile compound.
[0003]
In recent years, however, environmental problems on a global scale have been highlighted. However, the PFC and HFC described above are easy to absorb infrared rays and have a long life in the atmosphere of over 3000 years. The impact is so great that it is expected that their use will be limited or difficult to obtain in the future.
[0004]
In PFC and HFC gas plasma, F and CF ₁ , CF ₂ , CF _Three Fluorocarbon radicals and ions are present. Etching of silicon oxide film is a mechanism in which these active species (radicals) adhere to the reaction surface of silicon oxide film, and volatiles are generated by chemical reaction under a pseudo high temperature state by the energy of ions incident on the silicon oxide film. Proceed with Therefore, in order to obtain good etching characteristics, it is necessary to control the active species incident on the sample and the energy and density of ions incident on the sample. Control of the density and active species of ions in the plasma is controlled by the plasma generation mechanism of these etching apparatuses.
[0005]
Moreover, as a method for generating active species in a reaction vessel, for example, JP-A-7-74147 describes that the inside of a reaction vessel is composed of a carbon-based material, and this carbon component is supplied into plasma and etched. Has been.
[0006]
In Japanese Patent Laid-Open No. 4-363302, the reaction vessel is made of ceramics to prevent a decrease in etching action due to active species on the sample, and a heater is provided on the outer periphery of the reaction vessel so that plasma is applied to the ceramic reaction vessel. It describes reducing thermal shock.
[0007]
On the other hand, when PFC or HFC gas plasma is used, the fluorocarbon-based or carbon-based polymer adheres to the reaction chamber wall as the sample processing proceeds. As described in Japanese Patent Application Laid-Open No. 5-62936 as a method for removing the deposit, an electrode which is insulated from the outer wall of the reaction chamber and divided into a plurality of portions is installed on the inner surface of the reaction chamber, and an electrode for plasma generation There is known a method of performing plasma cleaning by sequentially applying a high-frequency voltage between the two. JP-A-1-231320, JP-A-1-231321, and JP-A-1-231322 describe a plasma cleaning method by applying a voltage to an electrode insulated from the outer wall of a reaction chamber. ing.
[0008]
[Problems to be solved by the invention]
However, even if plasma cleaning is performed as in the conventional example, deposits are present on the reaction chamber wall before cleaning. Since fluorine in the plasma reacts with the adhesion layer on the inner wall of the reaction chamber, the fluorine density in the plasma gradually decreases and the proportion of carbon in the plasma increases. That is, as the adhesion to the reaction chamber wall progresses, the radical composition changes, which causes a change over time in that the etching characteristics change, which is a serious problem.
[0009]
On the other hand, the etching apparatus can be classified into a capacitive coupling type, an ECR (electron cyclotron resonance) type, an ICP (inductive coupling) type, a surface wave excitation type, and the like according to a plasma generation mechanism. In the capacitively coupled device, a sample is placed on the lower electrode, and plasma generation control and sample incident energy control are attempted by applying different frequencies and voltages to the upper electrode and lower electrode by two voltage application mechanisms. Because of its structure, these cannot be controlled independently. The active species control in this apparatus is considered to be performed by carbon or silicon used for the electrode, but there is no control parameter for this. Therefore, the control by the two upper and lower power sources must perform three controls: ion density, energy control of ions incident on the sample, and control of active species, and a range of various parameters (processes) for obtaining good etching characteristics. There is a problem that it is difficult to obtain stable etching conditions. Here, the parameters that determine the etching characteristics include, for example, high-frequency power, μ-wave power, gas flow rate, gas pressure, and gas composition supplied between the electrode plates in the plasma generation mechanism. In the incident ion energy control, there are a waveform, frequency, power, and the like of an applied voltage.
[0010]
On the other hand, plasma generation methods other than the capacitive coupling type can control the plasma generation control independently of the energy control of ions incident on the sample, but the mechanism for controlling the active species depends on the plasma generation control. This also has the problem that the process window is narrow. Specifically, when SAC (Self Align Contact) silicon oxide film processing is performed with a high-density plasma etching apparatus such as ECR, the trade-off between etching stop at the hole bottom and silicon nitride film scraping becomes a problem. ing. Further, when etching with high selectivity is performed using high-density plasma, a microloading phenomenon in which the etching rate decreases as the hole diameter decreases and a reverse microloading phenomenon occur, which is a problem. Further, when metal processing of a laminated film such as TiN and Al is performed with these apparatuses, there is a problem that a local abnormal side etching shape (notching) can be formed at the boundary between different materials such as TiN and Al.
[0011]
Further, in the method described in JP-A-7-74147, it is difficult to perform desired etching because the appropriate amount of active species cannot be controlled. In the method described in JP-A-4-363211, there is a problem that active species cannot be generated in the reaction vessel.
[0012]
[Means for Solving the Problems]
The above object is achieved by generating an amount of active species necessary for etching in a region where the plasma is in contact.
[0013]
Specific description will be given below. In the etching of the silicon oxide film and silicon nitride film on the sample, for example, a gas containing fluorine is introduced into the reaction chamber and maintained in a low gas pressure state such as 0.3 Pa-200 Pa, and μ wave or RF wave This gas is discharged by the input power of, and plasma is generated. Then, a direct current or a high frequency voltage is applied to a carbon-containing solid placed in a region in contact with plasma to release a desired amount of carbon, and fluorine radicals in the plasma are converted into CF, CF ₂ , CF _Three , C ₂ F _Four Etch the sample by converting it to fluorocarbon radicals.
[0014]
Moreover, if a gas containing fluorine and not carbon is introduced as a gas to be introduced into the reaction chamber, and the fluorine-containing gas and solid carbon are reacted in the reaction chamber, a silicon oxide film or silicon is used without using PFC or HFC. A nitride film or the like can be selectively etched. That is, when a plasma of fluorine gas not containing carbon is generated and fluorine atom ions are reacted with solid carbon newly installed in the reaction chamber, CF _Four , CF ₂ , CF _Three , C ₂ F _Four Of carbon and fluorine. The active species molecules which are these compounds can be directly generated from the dissociation of the PFC gas conventionally, and the silicon oxide film can be etched by the generated active species molecules. The feature of the present invention is that in the etching of the silicon oxide film and the silicon nitride film, the active species necessary for the etching is not directly supplied from the PFC or HFC gas, but is converted and generated by reaction with the solid in the plasma processing chamber. By this method, even when PFC and HFC gas are restricted and prohibited from being used, it is possible to generate active species necessary for etching and perform etching while maintaining the conventional selectivity.
[0015]
On the other hand, with respect to the problem of improving the selection ratio and the process margin during the SAC processing, the CF that is an etchant of the silicon oxide film is used. ₂ This can be achieved by single seeding. On the other hand, the active species control material is carbon, and this is arranged on the plasma boundary surface, thereby reducing the fluorine in the plasma to 1/2, compared to the case where aluminum is used as the active species control material, CF ₁ , CF ₂ , CF _Three Has been found to be able to increase by 5, 10 and 2 times respectively. The results are shown in FIG. FIG. 2 shows Al, SiO as active species control materials. ₂ , CF when C is used _Four Fluorine and CF in plasma ₂ It is the result of having measured. This result shows that when aluminum is used as the active species control material, there is no reaction with fluorine, so the fluorine density is large, but when carbon is used, the fluorine density is halved compared to aluminum. This is because carbon in the active species control material reacts with fluorine in the plasma, and CF ₂ It is conceivable that a conversion reaction such as an increase occurs. At this time, CF ₁ , CF ₂ It was also confirmed that it increased. The active species control material is SiO ₂ Then, like fluorine in plasma, CF ₁ , CF ₂ , CF _Three Decreased, CF ₁ , CF ₂ , CF _Three And SiO of active species control material ₂ Indicates that there is a chemical reaction. In this way, the active species composition in the plasma can be changed by providing an active species control material that causes a chemical reaction with the active species in the plasma and volatilizes the product in the plasma region. Even if silicon or silicon carbide is used as the active species material, SiF ₂ The chemical reaction which produces | generates volatile matters, such as this, occurred, and the fluorine in plasma could be reduced.
[0016]
Furthermore, it was confirmed that the single species of the active species was promoted by installing a voltage application mechanism in the active species control material and applying a voltage in parallel with the sample processing. Figure 3 shows CF _Four CF when a negative DC voltage is applied to a carbon active species control material in a gas plasma ₁ , CF ₂ , CF _Three It is the result of having measured the radical density of. As the applied voltage increases, CF _Three Decreased, CF ₂ Is newly found to increase. This phenomenon is caused by an ion assist reaction on the active species control material. Utilizing this effect, the fluorine in the plasma is converted into CF. ₂ By using plasma that has been converted into a single species of active species, the reaction product volatilizes on the silicon oxide film and etching proceeds, but the etching stops because of the residue on the silicon nitride film Etching becomes possible, and the problem of the shoulder shaving of the nitride film due to the lowering of the selection ratio can be solved. Also, compared to the conventional etching mechanism based on the balance between carbon and fluorine, CF has a lower coefficient of adhesion to the etching side surface than carbon. ₂ It was confirmed that it is possible to suppress the microloading and reverse microloading phenomenon.
[0017]
In addition, when etching samples with significantly different etching rates, the active species control material is the same element as the material to be etched or a compound containing at least one element that is the same as the material to be etched. By controlling the voltage applied to the material over time or monitoring and consuming / releasing the radicals that are the active species control material, local abnormal shapes such as those occurring between different materials could be suppressed.
[0018]
Furthermore, the problem of local shape anomalies between different materials in metal etching can be solved by reducing the variation of the etchant. That is, the problem can be solved by using the active species control material as the material to be etched and controlling the active species density according to the etching time or the active species monitoring result.
[0019]
On the other hand, it is possible to suppress changes in etching characteristics over time by removing deposits on the surface in contact with plasma. That is, deposits attached to the plasma contact surface could be automatically removed by arranging the active species control material so as to surround the plasma and processing the sample while applying a voltage from the outside. In addition, the effect of improving the throughput by applying a voltage during sample processing was also obtained. Where C _Four F ₈ 1.5 mTorr, μ-wave power 200 W, C _Four F ₈ FIG. 5 shows the results of measuring the thickness of the deposited layer with a step gauge when an arbitrary voltage is applied to an aluminum plate placed on the surface in contact with the plasma. Although the deposit depends on the plasma density, it is possible to suppress the change in etching characteristics over time because the deposited film does not adhere by applying an appropriate voltage to the plasma interface.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
FIG. 1 is a side view of an etching apparatus equipped with the present invention, which uses ECR plasma, which is a method for generating a plasma using the interaction between a magnetic field and an electromagnetic wave. The reaction chamber 104 includes a microwave introduction window 103, a vacuum exhaust device 108, and a gas introduction pipe 109, and a sample stage 107 for installing a sample 106 is provided therein. The plasma generation mechanism includes a microwave oscillator 101, a waveguide 102, and an electromagnet 105. The sample stage 107 is connected to an RF power source 110 for accelerating ions incident on the sample 106. The RF power source 110 oscillates a radio wave having a frequency of several hundred kHz to several tens of MHz. The ions accelerated by the radio waves are incident on the sample 106, thereby promoting the etching reaction.
[0021]
The gas is introduced into the reaction chamber 104 through the gas introduction pipe 109, and plasma 113 is generated. In particular, when performing oxide film etching, fluorocarbon gas plasma is used. In this plasma, fluorine or CF generated by dissociation is used. ₁ , CF ₂ , CF _Three Active species such as exist. Here, when the fluorine is excessive in the plasma, for example, in the SAC processing, since both the nitride film and the oxide film are etched, it becomes difficult to perform selective etching. Therefore, in order to perform selective etching of SAC processing, it is a necessary condition to reduce fluorine in plasma. The apparatus has an active species control material 112 including a material that newly controls the active species. The active species control material 112 is temperature controlled by a heater 116, a cooling pipe 117, and a temperature control circuit 121. The temperature is monitored by a temperature monitor 114. The temperature control will be described in the fifth embodiment. In addition, this apparatus can monitor the plasma state with an emission spectrometer provided with a feedback circuit.
[0022]
It was newly confirmed that the conversion reaction can be further promoted by applying a voltage to the active species control material 112. As means for applying a voltage to the active species control material 112, an insulator 111 is installed between the active species control material 112 and the reaction chamber 104, and a voltage application circuit 115 including a blocking capacitor 117 and an AC power source 119 is provided. . Here, the blocking capacitor serves to block the direct current from the plasma, and Vdc is generated by the blocking capacitor, so that ions can be effectively accelerated. The voltage application circuit 115 may be a direct current power source if the material of the alternating current power source 119, the pulse power source, and the active species control material is a conductor. As the insulator 111, it is preferable to use alumina or silicon nitride that can withstand a temperature of about 400 ° C. Needless to say, it is not necessary to install the insulator 111 when no voltage is applied.
[0023]
When an insulator such as quartz or silicon nitride is used as the active species control material 112, a conductive plate 401 is inserted between the active species control material 112 and the insulator 111 as shown in FIG. The voltage introduction efficiency is better when the voltage application circuit 115 is connected to the conductive plate 401.
[0024]
Figure 3 shows CF _Four CF when a negative DC voltage is applied to the carbon active species control material 112 in a gas plasma. ₁ , CF ₂ , CF _Three It is the result of having measured the radical density of. As the applied voltage increases, CF _Three Decreased, CF ₂ Is newly found to increase. This is because an ion-assisted reaction occurs in which ions are incident on a state where a fluorocarbon-based adhesion layer is formed on the active species control material, and a local pseudo-high temperature state is created by the energy to promote a chemical reaction. Due to that.
[0025]
In general, it is known that a chemical reaction product under a high temperature condition is likely to generate an unstable molecule at room temperature where the number of bonded atoms is small. For example, chlorine atoms adsorbed on a silicon substrate are converted into SiCl by chemical reaction with the underlying Si at a substrate temperature of 600 ° C. ₂ It is known that SiCl is produced at 900 ° C. Therefore, under the ion energy obtained in this experiment, CF ₂ It is assumed that is easily generated stably. That is, if carbon is used as the active species control material 112 in a fluorocarbon gas plasma and an ion assist reaction by applying a voltage is used, F and CF in the plasma are used. _Three CF ₂ This indicates that the active species in the plasma can be controlled.
[0026]
Further, the lower limit of the frequency of the high frequency voltage that can be applied to the active species control material is determined by the density of the plasma used. The plasma density used for etching is 10 ¹¹ -10 ¹² Piece / cm ^Three The saturation ion current density I at that time _e 10 ^-2 -10 ^-Four A / cm ² Degree. In general, when applying a high frequency to an electrode in plasma, approximately I _e / (CV) or higher frequency is required. This relational expression is derived qualitatively from the fact that the voltage change of the electrode dropped by the voltage application mechanism needs to change faster than the change of the amount of ions flowing in so as to cancel it. Here, C is a capacitance per unit area of about 10 ^-11 About Farad, V is the applied voltage, about 10 ² It is about a bolt. Therefore, in the above plasma used for etching, the frequency of the high frequency that can be applied must be 100 kHz or more. Regarding the upper limit value, the frequency at which ions can follow the voltage change and have an ion assist reaction effect was about 100 MHz. At this time, if a pulse power source and a DC power source are used as the voltage application circuit 115, the ion energy incident on the active species control material can be monochromatic, and the conversion reaction path can be unified. Selective generation of active species can be performed more efficiently. If the active species control material to be used is an insulator, the above effect can be obtained only by a pulse voltage. However, if it is a conductor, it is preferable to apply a DC voltage from the viewpoint of apparatus cost. Further, the frequency of the pulse used at this time varies depending on the electrostatic capacity of the system to which the voltage is applied. However, if the system has a capacity of about several tens of nF, 100 kHz or more is necessary.
[0027]
In the present invention, not only the fluorocarbon gas plasma but also a carbon-based gas or an organic resist as a mask is used to cause an ion-assisted reaction on the deposit on the active species control material 112 for etching. It is possible to convert it into an active species effective for removal.
[0028]
(Example 2)
An embodiment in which silicon oxide film etching is performed without using PFC or HFC gas will be described below. In the present embodiment of the ECR type microwave discharge plasma as shown in FIG. 1, no electrode facing the wafer is provided. Therefore, since the electrode facing the wafer cannot be made of carbon, in principle, etching using a gas not containing carbon is difficult.
[0029]
However, as a result of the active species control material 112 being SiC, the introduced gas is Ar and SF. ₆ The gas was allowed to flow into the reaction chamber 104 as a gas containing no carbon. This total gas flow is set to 20-300 sccm and SF ₆ Was varied from 1 to 10 sccm. The discharge pressure was set to 0.1-5 Pa. This introduced gas was turned into plasma and reacted with SiC to generate active species necessary for etching.
[0030]
In the wafer, a silicon oxide film was formed as a film to be etched, and the etching mask was made of photoresist. This photoresist used was a fine pattern formed by lithography. Further, a silicon nitride film and a silicon film were used as an underlayer for the oxide film.
[0031]
Under the condition that the etching rate of the SiC plate is 50 nm / min to 600 nm / min, the etching rate of the oxide film changes from 400 nm / min to 2000 nm / min, and the etching rate of the resist film changes from 500 nm / min to 80 nm / min. did. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be increased. The etching rate of the silicon film also changed in the same manner as the resist. In order to most selectively etch the silicon nitride film, it is necessary to increase the etching rate of the SiC wall electrode. That is, with an etch rate of SiC 250 nm / min, the etch rate of the oxide film was 1000 nm / min, the etch rate of the silicon nitride film was 70 nm / min, and the selectivity of the silicon nitride film was 14.2.
[0032]
In this state, the effect of the temperature of the wall electrode and the wafer electrode was changed from −60 ° C. to 250 ° C., and the effect on the etching was examined. As a result, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible. A particularly preferred temperature was 0 ° C. or higher. The selectivity of the silicon nitride film with respect to the SiC temperature of 200 ° C. was 5. As for the electrode on the wall surface, deposition of a substance is likely to occur at a low temperature. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, when a plasma of a gas not containing carbon is used, carbon is contained in the surface of the solid in contact with the plasma to generate an etching reaction of the solid, and the temperature of the solid is set to 0 ° C. or more in particular. As a result, it was clarified that the silicon oxide film can be etched at a high etching rate, and the effectiveness of the present invention was confirmed.
[0033]
As an example of a gas containing no carbon, here Ar and SF ₆ However, other inert gases Ne, Kr, and Xe may be used. In the case of a gas containing fluorine, SF is used. ₆ Is not good because it has a high global warming potential and a long lifetime, but it has the advantage of requiring very little consumption. SF ₆ Except for F ₂ , HF, XeF ₂ , PF _Three , BF _Three , NF _Three , SiF _Four , Fluoride chloride ClF, ClF _Three , Fluorine bromide BrF, BrF _Three , BrF _Five , Fluorine iodide IF _Five It is effective.
[0034]
Besides SiC, pyrolytic graphite plate, organic resin film, SiCN, diamond plate, Al _Four C _Three It has been found that any carbon-containing material such as boron carbide may be used. Similarly, the active species necessary for etching could be formed even in the structure in which these carbides were formed on the surface of other materials.
[0035]
Example 3
An example in which the same material as the material to be treated is used as the active species control material will be described. Use of such a material is effective in improving an abnormal shape that occurs when a laminated structure in which a sample is formed of a different material is etched in the same plasma. For example, FIG. 4A shows SiO used for metal wiring processing in chlorine plasma. ₂ This is an etching shape when the laminated structure of the resist 301, TiN304, Al303, and TiN304 formed on 305 is etched by a conventional ECR plasma etching apparatus. Thus, in the conventional apparatus, the Al portion (notching portion) 302 that forms a boundary with the TiN 304 is abnormally shaved.
[0036]
FIG. 4B shows the change in the chlorine concentration in the plasma at this time. This graph shows that the chlorine concentration 307 in the notching portion suddenly decreases from a state where the chlorine density 306 at the time of TiN etching is large, and then changes to a state of a stable chlorine concentration 308 at the time of Al etching. This indicates that an abnormal shape occurs because the chlorine density in the plasma is excessive at the notching portion 302.
[0037]
Therefore, if Al is used as the active species control material 112 when performing this etching, the chlorine radical density 309 (FIG. 4 (b)) in which chlorine is consumed by Al on the wall surface during TiN304 etching can be obtained. Even if the etching layer changes to Al, rapid fluctuations in chlorine radicals can be suppressed. This is shown in FIG. In other words, it is considered that excessive active species stay when the active species are transferred to different layers between different materials. Therefore, when etching a layer that consumes less active species in etching the sample, a voltage is applied to the active species control material and the etchant is consumed by the active species control material, thereby stabilizing the amount of active species incident on the sample. It was possible to reduce the variation of the etchant.
[0038]
In addition, by using the same material as the mask material for the active species control material, changes in the amount of oxygen and carbon in the plasma generated from the etched mask material can be reduced, so that it is also stable in time. A sidewall protective film can be formed, and an etched shape without the undercut portion 310 (FIG. 4A) can be obtained.
[0039]
The present invention is applicable to other laminated structures, specifically, a resist-polysilicon laminated structure, SiO ₂ -Si _Three N _Four Structure, Al-W-Al structure, TiN-AlCu-TiN-Ti structure, TiN-Cu-TiN structure, SiO ₂ Mask-Pt structure, Polysilicon-SiO ₂ In such a case, polysilicon, Si, etc. are used as active species control materials. _Three N _Four , W, Al, Cu, Pt, SiO ₂ It was confirmed that it should be used. In addition, if an active species control material containing the same material as the sample material is used, the effect of the present invention is certain, but another material whose reaction rate with the etchant proceeds at the same rate as the material to be processed is used. Even if applied, there is an effect.
[0040]
At this time, the variation rate of the etchant between different materials is about the area ratio between the etching surface and the active species control material. The surface of the sample to be processed when etching is made up of a mask part and a material part to be processed. By making the area of the plasma boundary part of the active species control material larger than the area of the small part, the active species It was possible to suppress the rate of change.
[0041]
(Example 4)
An example of a method and mechanism for applying a voltage to the active species control material will be described. In the case where a high frequency is applied to the active species control material, if the area thereof is approximately the same as the area of the portion where the plasma potential is determined, the plasma potential 602 varies following the applied voltage 601 as shown in FIG. A phenomenon occurs. When the following phenomenon of the plasma potential 602 occurs, the sheath voltage between the plasma and the active species control material becomes 603, and the self-bias voltage 604 that is the direct current component is not applied. Since it becomes impossible to control the ion incident energy to the surface, a method for avoiding this is required. The policy of this method is to reduce the area of the active species control material to which the voltage is applied relative to the area of the portion where the plasma potential is determined, or increase the frequency to be applied and the amount of ions flowing in one cycle. A method of reducing or increasing the capacity of the blocking capacitor 118 is effective. For this purpose, a method of dividing the active species control material 112 into a plurality of mutually isolated blocks is preferable. This method is effective in avoiding the plasma potential following phenomenon because the total amount of ion current incident from the plasma during voltage application is reduced.
[0042]
An effective example is shown in FIG. FIG. 8 is a schematic diagram of the operation of the voltage application circuit in which the active species control material is divided into three blocks 802, 803, and 804 that are insulated from each other by the insulator 111 and the relay circuit 801 is incorporated. The area ratio between the block portion to which voltage is applied by the relay circuit 801 and the portion that determines the plasma potential (in this case, the ground potential) can be further reduced. At this time, the same effect can be obtained by using a plurality of small-area active species control materials.
[0043]
The operation of the relay circuit 801 when a high frequency voltage is applied to the active species control material divided into three at the timing shown in FIG. 7 is performed using time 1 in FIG. 8A and time 2 in FIG. 8B. I will explain. First, at time 1, the block a802 is connected to the high frequency power source 119, and the other blocks are grounded. Next, at time 2, the block b803 is connected to the high frequency power supply 119, and the other blocks are shown to be grounded. Similarly, at time 3, the block c804 is connected to the high frequency power supply 119, and the others are grounded. In this way, it is possible to efficiently prevent fluctuations in plasma potential by applying a voltage to a plurality of blocks sequentially and grounding blocks other than the voltage applied. In addition, although it divided | segmented into three here, if it is two or more, the same effect will be acquired.
[0044]
However, although the method of FIG. 8 is good enough to expect the effect of only removing the deposits, from the viewpoint of active species control, it is conceivable that the control efficiency decreases as the area decreases. Therefore, as shown in FIG. 9A, instead of the high frequency power supply 119, a multiphase high frequency power supply circuit 901 is connected, and high frequency having different phases is applied to each of the block a802, block b803, and block c804 divided into three blocks. By simultaneously applying (since block 802 a sine wave 902 having an initial phase of 0 °, block b803 having a sine wave 903 having an initial phase of 120 °, and block c804 having a sine wave 904 having an initial phase of 240 °), FIG. The plasma potential 602 as shown in FIG. In addition, since the voltage can be applied to a plurality of blocks at the same time, the active species control efficiency is improved as compared with the method of FIG. 8, and the deposit removal efficiency is improved. In order to implement this method, a plurality of high-frequency power sources having different phases may be used. It goes without saying that the same effect can be obtained by applying different frequencies to the divided blocks in order to control the energy of incident ions to the active species control material.
[0045]
(Example 5)
An embodiment in which a temperature control mechanism is installed in the active species control material will be described with reference to FIG. The active species control in the present invention includes a method that utilizes the difference in stable products depending on the temperature under the progress of the chemical reaction and a method that controls the macroscopic temperature of the active species control material, both of which are effective. By keeping the temperature of the active species control material 112 constant regardless of the heating from the plasma during the operation of the apparatus, the desorptions of chemical species such as oxygen, water, and hydrogen from the active species control material 112 and the chemical reaction generation efficiency are always maintained. Can be constant. Examples of the means for keeping the temperature of the active species control material constant include a heater 116 as a heating means, a cooling pipe 117 as a cooling means, and a temperature monitor 114 as a temperature detection means. The temperature control circuit 121 adjusts the temperature of the heater 116 and the cooling pipe 117 based on the above. In this case, means such as an infrared lamp may be used as the heating means, and liquid nitrogen, water, or oil may be used as the cooling means.
[0046]
(Example 6)
Example of a mechanism for detecting the amount of active species in plasma and the amount deposited on the active species control material 112 and controlling the voltage and frequency applied to the active species control material according to the plasma state and sample processing state Will be described. In the figure, 111 is an insulator, and 114 is a reaction chamber. First, FIG. 10 shows an embodiment provided with means for detecting the amount of active species control material deposited and the amount of sputtering. As a spatter amount detection means, a substance 1003 constituting an active species control material is vapor-deposited on a part of the quartz oscillator film thickness probe 1001, and a part of the substance 1003 is connected to a high-frequency power source 119 via a blocking capacitor 118. The structure is such that the same voltage as that of the active species control material 112 can be applied. Then, the amount adhering to or scraping off during the operation of the apparatus is captured by the change in the vibration frequency of the crystal, and the amount corresponding to the change in the vibration frequency is fed back to the voltage application circuit 115 by the feedback circuit 1002. By controlling the applied voltage and frequency so as to obtain an appropriate amount of cutting, the life of the active species control material 112 can be extended, and it is possible to cope with plasma conditions that change every moment.
[0047]
Further, as means for detecting a change in the amount of active species in the plasma, the emission spectrum 120 of FIG. 1 is installed, and an electric circuit for controlling the voltage applied to the active species control material is provided based on the increase or decrease of the detection result. As a result, the active species in the plasma can always be kept constant in real time.
[0048]
FIG. 17 shows a high-frequency voltage applied according to the sample processing time and a frequency control mechanism. In order to perform time control, a control program is prepared in addition to the time control computer 1701, and the voltage and frequency applied to the active species control material 112 are temporally changed based on the programmed time sequence. The digital signal corresponding to the voltage value and frequency from the control computer 1701 is converted into those analog voltages by the D / A converter 1702 and input to the voltage application circuit 115 to be applied to the active species control material 112, and Change the frequency. In this method, there are few mechanisms added to the reaction chamber, and arbitrary time control can be performed outside the reaction chamber. In other words, if the etching rate associated with sample processing and the film thickness of the material to be processed are known, the voltage value and frequency value associated with the processing time can be set freely by the program and realized at a relatively low cost. There is an advantage that you can. In order to realize the embodiment as described above, the voltage application mechanism 115 has a function capable of changing the voltage value or frequency applied to the active species control material 112 by an external input voltage or the like. is required.
[0049]
(Example 7)
An embodiment in which the voltage of the direct current component (self-bias voltage) applied to the active species control material is set to −20 V or less will be described. First, in order to accelerate ions having a positive charge, it is necessary to apply at least a negative bias, that is, a voltage of 0 V or less. At this time, it is presumed that the chemical reaction region by the ion-assisted reaction is almost proportional to the range of incident ions. For example, it is known that the range R (Å) of Ar ions having energy E (eV) of 1000 eV or less has a relationship of R = 0.08 × E. At this time, it is necessary that at least one molecule participating in the reaction exists in the reaction region. Among the materials of the assumed active species mechanism, since the Si—O bond of quartz having a small interatomic distance is 1.62 Å, ion conversion requires at least 20 eV when performing active species conversion. Therefore, active species control can be advanced efficiently by setting the voltage applied to the active species control material to -20 V or less.
[0050]
(Example 8)
An embodiment in which the voltage of the direct current component (self-bias voltage) applied to the active species control material is set to −50 V or more will be described. FIG. 5 shows the CCR using an ECR plasma apparatus. _Four F ₈ It is the result of having measured the thickness of the deposit | attachment of Al surface when a Al sample was installed in gas plasma and the alternating voltage of 800 kHz was applied with the level difference meter. From this result, under conditions of 1.5 mTorr and μW power of 200 W, a surface is obtained in which the self-bias voltage, which is the DC component of the sheath voltage, is −45 V, no deposits adhere, and the underlying Al is not etched. I understand that In consideration of the error in the surface roughness of the Al sample used for the measurement, it is considered that there are conditions under which the active species control material is not etched when the applied voltage is set to −50 V or more. Further, such a voltage varies depending on the sputter threshold voltage unique to the attached active species, the amount of active species incident on the active species control material from the plasma, and the plasma density. It is also possible to adjust using.
[0051]
Therefore, when the applied voltage is between 0V and -50V, there is a voltage that can sputter only carbon-based deposits. By applying this voltage during sample processing, the effect of controlling the active species can be achieved simultaneously with the plasma boundary. Since deposits on the surface can be removed, oxygen cleaning can be shortened or omitted, leading to an improvement in total throughput. At this time, it is also conceivable to perform the sample processing time and the voltage application time to the active species control material at different timings. Further, by introducing a cleaning gas (oxygen, argon, etc.) with the above apparatus, the plasma interface can be cleaned by the same method as described above.
[0052]
Example 9
Taking an example of silicon oxide film etching in a UHF wave plasma etching apparatus using a magnetic field, an effective method of using a gas according to the present invention will be described with reference to FIG. In this example, ClF is used as the gas not containing carbon. _Three Is used. Ne, Ar, Kr, and Xe were mixed as an inert gas. For gases containing fluorine, SF ₆ , NF _Three Although it has a high global warming potential and a long lifetime, it is not desirable, but it has the advantage of requiring very little consumption, but ClF _Three Had the same effect.
[0053]
In this embodiment, the UHF wave radiation antenna 71 is opposed to the wafer, and the material thereof is a pyrolytic graphite plate. The pyrolytic graphite plate is made of organic resin film, SiCN, diamond plate, Al in addition to SiC. _Four C _Three It has been found that any carbon-containing material such as boron carbide may be used. In addition, a structure in which these carbides are formed on the surface is also effective. When a low-path filter was installed outside the UHF wave radiating antenna 71 and an RF power supply was installed, the counter electrode structure was formed, and the generated particles were efficiently incident on the sample, and the effect of active species control could be increased.
[0054]
The total gas flow rate was set to 50-500 sccm, and SF6 was varied from 1-10 sccm. The discharge pressure was set to 0.5-5 Pa. The UHF wave is transmitted from the plasma discharge UHF wave power source 74 through the coaxial cable 79 and input from the radiation antenna 71 to generate plasma. The lower wafer electrode 107 was supplied with rf electric power 110 for accelerating ions in the plasma. The distance between the upper and lower electrodes was set to 10-200 mm, and a mechanism capable of applying rf power 119 to the pyrolytic graphite plate as the active species control material 112 was provided. Reference numeral 78 in the figure denotes a magnet. As the material for the wall surface, SiC surface-treated as a substance containing carbon was used. When power is supplied to this SiC, the SiC is etched by the plasma.
[0055]
In the wafer, similarly, a silicon oxide film is formed as a film to be etched, and the etching mask is made of photoresist. A photolithographic resist having a fine pattern formed thereon was used. Further, a silicon nitride film and a silicon film were used as an underlayer for the oxide film.
[0056]
When the oxide film is etched under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode is 50 nm / min to 600 nm / min, the etching rate of the oxide film changes from 400 nm / min to 1400 nm / min, and the etching rate of the resist film Changed from 600 nm / min to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be increased. The etching rate of the silicon film also changed in the same manner as the resist. In order to most selectively etch the silicon nitride film, it is necessary to increase the etching rate of the SiC wall electrode.
[0057]
In this state, the temperature effect of the upper and lower electrodes and the wall surface electrode was changed from −60 ° C. to 250 ° C., and the effect on the etching was examined. As a result, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible. A particularly preferred temperature was 0 ° C. or higher. The temperature of the upper electrode was one of the factors determining the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it can be used by setting a predetermined etching rate within the above temperature range. As for the electrode on the wall surface, deposition of a substance is likely to occur at a low temperature. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, ClF is used as a gas not containing carbon. _Three When silicon is used, carbon is contained in the solid surface in contact with the plasma to generate an etching reaction of the solid, and the temperature of the solid is controlled from −60 ° C. to 250 ° C., thereby highly etching the silicon oxide film. It was revealed that etching can be performed at a speed, and the effectiveness of the present invention was confirmed.
[0058]
(Example 10)
FIG. 14 shows an embodiment of the present invention using surface wave excitation type plasma as a plasma generator. Electromagnetic waves from the waveguide 1402 give plasma energy through the dielectric 1401 to generate plasma. Other mechanisms and effects are the same as when the ECR type is used as the plasma generation mechanism.
[0059]
(Example 11)
An example in which carbon is used as the material of the active species control material and SAC processing is performed by applying the present invention will be described. FIG. 16A shows the structure of the sample before performing SAC processing. A gate electrode 1504 made of polysilicon is formed on a silicon substrate 1505. The SAC process is an oxide film process that forms a contact hole by etching the oxide film 1502 using the nitride film 1503 as a stopper layer, and is a promising method when forming a contact hole in a DRAM of 256M or later. Reference numeral 1501 denotes a resist. There is no concept of active species control or its mechanism cannot be controlled independently, for example, using a magnetic field microwave high-density plasma etching apparatus, _Four F ₈ When etching is performed under the conditions of 5 mTorr and microwave power 1100 W, as shown in FIG. 16B, the shoulder portion of the nitride film is scraped off to generate 1506, which indicates that the insulation of the polysilicon gate 1504 cannot be maintained. A trade-off that etching stop 1507 occurred at the bottom of the contact hole as shown in c) occurred, and the process window for good selective etching was narrow.
[0060]
By applying the present invention, the deposited film composition important for the etching reaction of the oxide film can be made suitable for selective etching. In other words, CF that is suitable for selective etching is reduced by reducing fluorine etching of both oxide and nitride films in the plasma. ₂ Therefore, deposits remain on the nitride film to suppress shoulder shaving, and a favorable surface reaction that promotes etching on the oxide film can be promoted. Therefore, when SAC processing is performed using this method, a good etching shape as shown in FIG. 16 (d) can be obtained.
[0061]
(Example 12)
An embodiment in which a silicon oxide film is etched by introducing a gas not containing carbon into a compound with a parallel plate etching apparatus will be described with reference to FIG. In this embodiment, a pyrolytic graphite plate is used for the electrode 1202 facing the wafer 106. As an example of the gas not containing carbon, the discharge gas is Ar and SF. ₆ The mixed gas was used. This mixed gas was supplied from above through the gas introduction hole of the pyrolytic graphite plate. The total gas flow rate is set to 100-500 sccm and SF ₆ Was varied from 1 to 10 sccm. The discharge pressure was set to 1 to 5 Pa. An rf power 1201 is applied to the upper electrode to generate plasma. The lower electrode 107 was supplied with rf power 110 for accelerating ions in the plasma. The distance between the upper and lower electrodes was varied from 5 to 50 mm.
[0062]
As the wafer, a resist, a silicon oxide film, a silicon film, and a silicon nitride film were used. Here, the silicon oxide film was etched using the photoresist as a mask.
[0063]
When the etching rate of the pyrolytic graphite plate of the upper electrode is changed from 100 nm / min to 1000 nm / min, the etching rate of the oxide film is changed from 500 nm / min to 2000 nm / min, and the etching rate of the resist film is It changed from 800 nm / min to 90 nm / min. The etching rate of the resist can be adjusted by the etching rate of the pyrolytic graphite plate, and the selectivity can be kept large. The etching rate of the silicon film also changed in the same manner as the resist. Accordingly, it has been found that the etching rate of the pyrolytic graphite plate needs to be increased by 100 nm / min or more in order to most selectively etch the silicon oxide film. That is, from this example, the silicon oxide film can be etched at a high etching rate with a gas containing no carbon, and the effectiveness of the present invention was confirmed.
[0064]
(Example 13)
In this embodiment, an example of etching using the apparatus in which the third electrode 112 is installed in the vicinity of the wall surface of the plasma processing chamber in the parallel plate type plasma processing apparatus as in Embodiment 12 will be described with reference to FIG. To do. When the surface-treated SiC 112 is used as the third electrode and electric power 119 is applied to the SiC, the SiC is etched by the plasma. The temperature of SiC 112 is adjusted by a heater 116 and a cooling pipe 117. Other than that is the same as Example 12.
[0065]
Under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode 1202 is from 100 nm / min to 400 nm / min, power 119 is applied to the SiC 112, and the resist, silicon oxide film, silicon on the wafer according to the etching rate of the SiC wall electrode Changes in the etching rate of the film and the silicon nitride film were measured. As a result, as the etching rate of the SiC electrode increased, the etching rate of the oxide film changed from 500 nm / min to 1500 nm / min, and the etching rate of the resist film changed from 300 nm / min to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be kept large. The etching rate of the silicon film also changed in the same manner as the resist. It has been found that the etching rate of the SiC wall electrode needs to be increased in order to most selectively etch the silicon nitride film. In other words, from this example, when a plasma of a gas that does not contain carbon is used, the silicon oxide film is etched at a high etching rate by containing carbon on the solid surface that comes into contact with the plasma and generating an etching reaction of this solid. It was clarified that it was possible to confirm the effectiveness of the present invention.
[0066]
There are several effective means for applying power to the wall of the plasma processing chamber. One of them was a method in which the wall surface was divided into several parts and operated with different bias powers. Second, there is an effect even if the wafer bias power supply is shared between the wafer and the wall surface by changing the phase of the power.
[0067]
Even in a very narrow situation where the distance between the upper and lower electrodes is 30 mm or less, the wall surface bias application method was effective.
[0068]
In order to control the etching rate of the wall surface electrode with high accuracy, it is necessary to control the waveform and frequency of the bias power on the wall surface, and the ion energy distribution can be set to be small and uniformly etched.
[0069]
(Example 14)
The silicon oxide film etching with a parallel plate etching apparatus using a magnetic field will be described with reference to FIG. In this embodiment, a pyrolytic graphite plate is used for the electrode 1202 facing the wafer 106. The discharge gas is Ar and SF ₆ The mixed gas was used. This mixed gas was supplied from above through the gas introduction hole of the pyrolytic graphite plate. The total gas flow rate is set to 20-500sccm and SF ₆ Was varied from 1 to 10 sccm. The discharge pressure was set to 0.1-5 Pa. The distance between the upper and lower electrodes was set to 10 to 200 mm. A surface-treated SiC 112 was used in the vicinity of the wall surface. When power is supplied to this SiC, the SiC is etched by the plasma. Other than that is the same as Example 12.
[0070]
Under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode is 50 nm / min to 600 nm / min, power is applied to SiC, and the resist, silicon oxide film, silicon film, silicon on the wafer according to the etching rate of this SiC electrode Changes in the etching rate of the nitride film were measured. As a result, as the etching rate of the SiC wall electrode increased, the etching rate of the oxide film changed from 400 nm / min to 1600 nm / min, and the etching rate of the resist film changed from 500 nm / min to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity can be kept large. The etching rate of the silicon film also changed in the same manner as the resist. It has been found that the etching rate of the SiC wall electrode needs to be increased in order to most selectively etch the silicon nitride film. In other words, from this example, when a plasma of a gas that does not contain carbon is used, the silicon oxide film is etched at a high etching rate by containing carbon on the solid surface that comes into contact with the plasma and generating an etching reaction of this solid. It was clarified that it was possible to confirm the effectiveness of the present invention.
[0071]
As in Example 2, there were some effective means for applying power to the wall surface of the plasma processing chamber. One of them was a method in which the wall surface was divided into several parts and operated with different bias powers. Second, there is an effect even if the wafer bias power supply is shared between the wafer and the wall surface by changing the phase of the power. The wall surface bias application method was effective even in a very narrow situation where the distance between the upper and lower electrodes was 30 mm or less, but it was particularly effective under the condition where the electrode distance exceeded 30 mm.
[0072]
(Example 15)
In the present embodiment, a method for etching while controlling the temperature of the electrode by further providing a temperature adjusting mechanism 48 in the embodiment 14 will be described with reference to FIG.
[0073]
The effect of the temperature on the upper and lower electrodes and the electrode on the wall surface was changed from -60 ° C. to 250 ° C. to examine the effect on the etching. As a result, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible. A particularly preferred temperature was 0 ° C. or higher. The temperature of the upper electrode was one of the factors determining the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it can be used by setting a predetermined etching rate within the above temperature range. As for the electrode on the wall surface, deposition of a substance is likely to occur at a low temperature. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, when a plasma of a gas not containing carbon is used, carbon is contained in the solid surface in contact with the plasma to generate an etching reaction of the solid, and the temperature of the solid is changed from −60 ° C. to 250 ° C. It was confirmed that the silicon oxide film can be etched at a high etching rate by controlling the above.
[0074]
(Example 16)
The silicon oxide film etching in the inductively coupled rf wave discharge etching apparatus according to the present invention will be described with reference to FIG. The wafer 106 is placed on a wafer table 107 that also serves as a bias high-frequency application lower electrode, and the wafer table 107 is connected to a bias high-frequency power source 110. In this embodiment, unlike Embodiments 12 to 15, an electrode facing the wafer is not installed, and an insulating window 51 is arranged. SiC was used as the active species control material 112 in the vicinity of the wall surface. A bias application power source 119 is connected to the SiC. As in Example 14, the total gas flow rate is set to 20 to 500 sccm, and SF is set. ₆ Was varied from 1 to 10 sccm. The discharge pressure was set to 0.3 to 5 Pa. The rf power was supplied from a plasma discharge high frequency power supply 54 to an antenna formed on the coil in the discharge part of the plasma processing chamber, and plasma was generated in the discharge window plate 58 or discharge tube made of alumina or quartz.
[0075]
The other conditions are the same as in Example 14. As a result, similarly to Example 4, the etching rate of the resist could be adjusted by the etching rate of the SiC wall surface electrode, and the selection ratio could be kept large. The etching rate of the silicon film also changed in the same manner as the resist. It has been found that the etching rate of the SiC wall electrode needs to be increased in order to most selectively etch the silicon nitride film.
[0076]
Further, as in Example 15, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible.
[0077]
(Example 17)
The silicon oxide film etching in the UHF wave plasma etching apparatus not using a magnetic field according to the present invention will be described with reference to FIG. In this embodiment, a pyrolytic graphite plate is used as the electrode 71 facing the wafer.
[0078]
The introduced gas is SF ₆ As a mixed gas of Ar and Ar, the total gas flow rate is set to 50 to 500 sccm, SF ₆ Was varied from 1 to 10 sccm. The discharge pressure was set to 0.5 to 5 Pa. The distance between the upper and lower electrodes was set to 10 to 200 mm. A surface-treated SiC 76 was used as the active species control mechanism in the vicinity of the wall surface of the plasma processing chamber. When power is supplied to this SiC, the SiC is etched by the plasma.
[0079]
The wafer used was a silicon nitride film, silicon film, silicon oxide film and photoresist formed on a substrate.
[0080]
The etching rate of the oxide film changes from 400 nm / min to 1400 nm / min under the condition that the etching rate of the pyrolytic graphite plate of the upper electrode is 50 nm / min to 600 nm / min, and the etching rate of the resist film changes from 600 nm / min. It changed to 60 nm / min. That is, the etching rate of the resist can be adjusted by the etching rate of the SiC wall electrode, and the selectivity is increased. The etching rate of the silicon film also changed in the same manner as the resist. In order to most selectively etch the silicon nitride film, it is necessary to increase the etching rate of the SiC wall electrode.
[0081]
Further, as in Example 15, it was found that the silicon oxide film can be selectively etched with respect to the silicon nitride film by setting the temperature of the wafer electrode as high as possible.
[0082]
(Example 18)
Taking an example of silicon oxide film etching in a UHF wave plasma etching apparatus using a magnetic field, an effective method of using a gas according to the present invention will be described with reference to FIG. In this example, ClF is used as the gas not containing carbon. _Three Is used. Ne, Ar, Kr, and Xe were mixed as an inert gas. As with fluorine-containing gas, ClF _Three Is not good because it has a high global warming potential and a long lifetime, but it has the advantage of requiring very little consumption. Other conditions are the same as in Example 17.
[0083]
As a result, ClF _Three Even in the case where is used, the same effect as in Example 17, that is, the effect that the silicon oxide film can be etched at a high etching rate by controlling the temperature of the active species control material from −60 ° C. to 250 ° C. was obtained.
[0084]
(Example 19)
Inductively coupled high frequency discharge plasma etching equipment with ClF _Three In addition, the silicon oxide film was etched using a gas containing a small amount of carbon as an etching gas.
[0085]
In this example, since the inductive coupling type is used, an electrode facing the wafer is not installed, but as a result of using SiC for the electrode 112 (FIG. 13) in the vicinity of the wall surface, the effect of the present invention was recognized. However, it is quite difficult to selectively etch the silicon oxide film with respect to the silicon nitride film. The present embodiment is a method for compensating for this. As the gas containing carbon, in addition to C, a gas containing any of H, F, and Cl may be used.
[0086]
The total gas flow rate is set to 20-500 sccm and ClF _Three Was varied from 0 to 10 sccm. Chloroform was used for a small amount of additive gas. The amount introduced is ClF. _Three It was set so as not to exceed. The discharge pressure was set to 0.3 to 5 Pa. The rf power was supplied to the antenna formed on the coil in the discharge part of the plasma processing chamber, and plasma was generated in a discharge window plate or discharge tube made of alumina or quartz. The wafer electrode was supplied with rf power for accelerating ions in the plasma.
[0087]
The wafer used was a silicon nitride film, silicon film, silicon oxide film, and photoresist formed on a substrate.
[0088]
Assuming that the SiC etching rate is 50 nm / min to 600 nm / min, the oxide film etching rate changes from 400 nm / min to 1600 nm / min, and the resist film etching rate changes from 500 nm / min to 60 nm / min. did. The etching rate of the silicon nitride film is 40 to 200 nm / min, and it is clear that the addition of chloroform improves the selectivity by 20% or more, and the effect of adding a small amount of gas is large. This is an example where the effectiveness is further utilized. That is, by adding a small amount of gas containing carbon, the etching rate of the resist can be adjusted, and the selectivity is increased. This carbon-containing gas is effective when it is flowed at 1% or less, preferably about 0.4 to 0.8% of the total gas flow rate. That is, in this embodiment, the above-described effect is obtained when a gas containing carbon is flowed at 5 sccm or less. The etching rate of the silicon film also changed in the same manner as the resist. The etching of the silicon nitride film could be selectively performed very effectively.
[0089]
In this state, the temperature effect of the upper and lower electrodes and the wall surface electrode was changed from −60 ° C. to 250 ° C., and the effect on the etching was examined. As a result, the temperature of the wafer electrode is about 10 ° C. at which the silicon oxide film can be selectively etched with respect to the silicon nitride film when the carbon-containing gas is added compared to when the carbon-containing gas is not added. It turned out that it may be low. A particularly preferable temperature was −10 ° C. or higher. The temperature of the upper electrode was one of the factors determining the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it can be used by setting a predetermined etching rate within the above temperature range. As for the electrode on the wall surface, deposition of a substance is likely to occur at a low temperature. However, like the upper electrode, it is one of the factors that determine the etching rate of the electrode surface. Therefore, it is necessary to keep the temperature as constant as possible. In addition, the higher the temperature, the higher the etching rate, and the lower the temperature, the lower the efficiency of the active species conversion reaction by the upper electrode. Therefore, it was possible to set and use a predetermined etching rate within the above temperature range. That is, from this example, ClF is used as a gas not containing carbon. _Three As a gas containing carbon, in addition to C, when a gas containing any one of H, F, and Cl is added, carbon is added to the solid surface in contact with the plasma. By generating a solid etching reaction and controlling the temperature of the solid from −60 ° C. to 240 ° C., it can be clarified that the silicon oxide film can be etched at a high etching rate and a high selectivity. Was confirmed.
[0090]
(Example 20)
The effective use of the gas according to the present invention will be described by taking silicon oxide film etching in an inductively coupled high frequency discharge plasma etching apparatus as an example. In this embodiment, ClF is used as an etching gas. _Three In addition, a gas containing oxygen, for example O ₂ Is used. At the same time, as in Example 19, a gas containing a trace amount of carbon may be used. Any of Ne, Ar, Kr, and Xe was mixed as an inert gas. For gases containing fluorine, OF ₆ , NF _Three , ClF _Three Can also be used. The important point of this embodiment is that O ₂ , CO, CO ₂ , NO, NO ₂ , H ₂ O or the like can be used.
[0091]
In this example, as a result of using pyrolytic graphite as an electrode in the vicinity of the wall surface, the effect of the present invention was recognized. However, it is quite difficult to selectively etch the silicon oxide film with respect to the silicon nitride film. The present embodiment is a method for compensating for this. As the gas containing carbon, in addition to C, a gas containing any of H, F, and Cl may be used.
[0092]
The total gas flow rate is set to 20-500 sccm and ClF _Three Was varied from 1 to 10 sccm. For trace amounts of additive gas, O ₂ It was used. The amount introduced is ClF. _Three It was set so as not to exceed. The discharge pressure was set to 0.3 to 5 Pa. The rf power was supplied to the antenna formed on the coil in the discharge part of the plasma processing chamber, and plasma was generated in a discharge window plate or discharge tube made of alumina or quartz. The wafer electrode was supplied with rf power for accelerating ions in the plasma. In this embodiment, unlike the previous examples, as a result of this etching reaction, CO, CO ₂ , C _Three O ₂ , C _Five O ₂ A carbon oxide gas such as is formed. As a result, it becomes extremely effective to selectively etch the silicon oxide film with respect to the silicon nitride film, and the effectiveness of the present invention can be further enhanced.
[0093]
The wafer used was a silicon nitride film, silicon film, silicon oxide film, and photoresist formed on a substrate.
[0094]
The etching rate of the oxide film changes from 400 nm / min to 1600 nm / min under the condition that the etching rate of graphite of the upper electrode is 50 nm / min to 600 nm / min, and the etching rate of the resist film changes from 500 nm / min to 60 nm / min. Changed. Further, the etching rate of the silicon nitride film is 30 to 150 nm / min, and the selectivity is improved by 15% or more by adding oxygen, and it is clear that the effect of adding a small amount of gas is large, and the effectiveness of the present invention is further improved. It was an example to be utilized. That is, by adding a small amount of a gas containing oxygen, the etching rate of the resist can be adjusted, and the selectivity is increased. The etching rate of the silicon film also changed in the same manner as the resist. The etching of the silicon nitride film could be selectively performed very effectively.
[0095]
In the above-described embodiment, pyrolytic graphite and SiC are used as the carbon-containing material, but in addition, organic resin film, SiCN, diamond plate, Al _Four C _Three Any carbon-containing material such as boron carbide may be used. In addition, a structure in which these carbides are formed on the surface is also effective.
[0096]
In the above-described embodiments, Ar is used as a gas not containing carbon, but other inert gases Ne, Kr, and Xe may be used.
[0097]
In the above-described embodiment, the gas containing fluorine is SF. ₆ And ClF _Three However, although it has a high global warming potential and a long lifetime, it has the advantage of requiring very little consumption. Other than these, F ₂ , HF, XeF ₂ , PF _Three , BF _Three , NF _Three , SiF _Four , Fluoride chloride ClF, bromofluoride BrF, BrF _Three , BrF _Five , Fluorine iodide IF _Five It may be.
[0098]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0099]
Without using PFC or HFC gas, it is possible to generate active species necessary for etching and to etch the silicon oxide film while maintaining the conventional selectivity.
[0100]
In the silicon oxide film process, fluorine in the plasma is converted into CF. ₂ By using plasma that has been converted into a single species of active species, the reaction product volatilizes on the silicon oxide film and etching proceeds, but the etching stops because of the residue on the silicon nitride film Etching can be performed, and the problem of shoulder shaving of the nitride film due to the lowering of the selection ratio and the expansion of the process margin can be solved.
[0101]
In addition, the change of active species between different materials during metal etching can be kept constant, and local shape abnormality can be suppressed.
[0102]
Since the deposits on the plasma boundary surface can be removed, the change with time can be suppressed, and stable and good etching characteristics can be obtained with high throughput and long term.
[Brief description of the drawings]
FIG. 1 is a view showing a cross section of a plasma etching apparatus equipped with an active species control material according to Example 1 of the present invention.
[Fig. 2] Al, SiO as active species control material ₂ , CF when C is used _Four Fluorine and CF in plasma ₂ It is a figure which shows a density.
FIG. 3 CF _Four CF when a negative DC voltage is applied to a carbon active species control material in a gas plasma ₁ , CF ₂ , CF _Three It is a figure which shows the change of the radical density of.
FIG. 4 is a diagram showing the shape of a resist-TiN-Al-TiN stacked structure when etching is performed with a conventional ECR plasma etching apparatus and the change in chlorine concentration in the plasma at that time.
FIG. 5 C _Four F ₈ It is a figure which shows the thickness of the deposition layer at the time of applying a voltage to the aluminum plate installed in the surface which contact | connects plasma.
FIG. 6 is a waveform diagram of a plasma potential, an applied voltage, a plasma sheath voltage, and a self-bias voltage when the area of the active species control material is approximately the same as the area of the portion that determines the plasma potential.
FIG. 7 is a diagram illustrating an example of timing for applying a voltage to each block when the active species control material is divided into three.
FIG. 8 is a schematic diagram of the operation of a voltage application circuit incorporating a relay circuit when the active species control material is divided into three.
FIG. 9 is a configuration diagram in the case where a multi-phase power supply circuit is connected, and a waveform diagram of a plasma potential, each applied voltage, each plasma sheath voltage, and a self-bias voltage.
FIG. 10 is a diagram showing an embodiment of a means for detecting the amount of adhesion to the active species control material or the amount of sputtering.
FIG. 11 is a schematic view of an ECR type UHF wave plasma etching apparatus using a gas composition and active species control material according to the present invention.
FIG. 12 is a cross-sectional view of an etching apparatus in which a capacitively coupled plasma is applied to a plasma generation mechanism and the present invention is mounted.
FIG. 13 is a cross-sectional view of an etching apparatus in which inductively coupled plasma is applied to a plasma generation mechanism and the present invention is mounted.
FIG. 14 is a sectional view of an etching apparatus in which surface wave excitation type plasma is applied to a plasma generation mechanism and the present invention is mounted.
FIG. 15 is a sectional view of an etching apparatus in which a magnetic field parallel plate plasma is applied to the plasma generation mechanism and the present invention is mounted.
FIG. 16 is a diagram showing a sample structure before performing SAC processing by oxide film etching, a diagram showing a shoulder shaving state during SAC processing in the conventional method, a diagram showing an etching stop state during SAC processing in the conventional method, and the present invention. It is a figure showing the etching shape at the time of performing SAC processing in the case of using.
FIG. 17 is a diagram illustrating a high-frequency voltage applied according to a sample processing time and a frequency control mechanism.
FIG. 18 is a diagram showing that a conductive plate is inserted between an active species control material and an insulator, and a voltage application circuit is connected to the conductive plate.
FIG. 19 is a cross-sectional view of an etching apparatus in which a magnetic field parallel plate plasma is applied to a plasma generation mechanism and the present invention is mounted.
FIG. 20 is a cross-sectional view of an etching apparatus in which parallel plate plasma is applied to the plasma generation mechanism and the present invention is mounted.
FIG. 21 is a diagram showing a processing shape when TiN—Al—TiN metal wiring processing is performed by applying the present invention;
[Explanation of symbols]
48: Temperature control mechanism, 51: Upper window, 54: High frequency power supply, 58: Coiled antenna, 71: Upper electrode, 74: UHF wave power supply, 78 ... Magnet, 79 ... Coaxial cable, 101 ... Microwave oscillator, 102 ... Waveguide, 103 ... Microwave introduction window, 104 ... Reaction chamber, 105 ... Electromagnet, 106 ... Sample, 107 ... Sample stand, 108 ... Vacuum exhaust device, 109 ... Gas introduction tube, 110 ... RF power supply, 111 ... Insulator 112 ... Active species control material, 113 ... Plasma, 114 ... Temperature monitor, 115 ... Voltage application circuit, 116 ... Heater, 117 ... Cooling tube, 118 ... Blocking capacitor, 119 ... AC power supply, 120 ... Light emission provided with feedback circuit Spectrometer 121 ... Temperature control circuit 301 ... Resist 302 ... Notch part 303 ... Aluminum 304 ... Nitriding Tan, 305 ... SiO ₂ 306: Chlorine concentration at the time of titanium nitride etching (when an abnormal shape occurs), 307 ... Chlorine density at the notching portion, 308 ... Stable chlorine concentration at the time of aluminum etching, 309 ... Chlorine density at the time of titanium nitride etching (application of the present invention) 310) undercut portion, 401 ... conductive plate, 601 ... applied voltage, 602 ... plasma potential, 603 ... sheath voltage, 604 ... self-bias voltage, 801 ... relay circuit, 802 ... block a, 803 ... block b, 804: Block c, 901: Multi-phase high-frequency power supply circuit, 902: Sine wave with initial phase of 0 degrees, 903: Sine wave with initial phase of 120 degrees, 904: Sine wave with initial phase of 240 degrees, 905: Sheath to block a Voltage, 906... Sheath voltage to block b, 907... Sheath voltage to block c, 1001. Thickness gauge probe, 1002 ... feedback circuit, 1003 ... substance constituting active species control material, 1201 ... high frequency power supply, 1202 ... grounding counter electrode, 1401 ... dielectric, 1402 ... waveguide, 1501 ... resist, 1502 ... oxide film , 1503, nitride film, 1504, polysilicon gate, 1505, silicon substrate, 1506, nitride shoulder shaving portion, 1507, etching stop portion, 1701, time control computer, 1702, D / A converter.

Claims (15)

Forming a silicon oxide film or a silicon nitride film on the substrate;
Forming a resist film having a predetermined pattern on the silicon oxide film or silicon nitride film;
Installing the substrate on which the resist film is formed on a table in a processing chamber;
Introducing a compound gas containing fluorine as a constituent element and not carbon as a constituent element into the processing chamber;
Converting the compound gas into plasma;
Reacting the plasmatized compound gas with carbon prepared in the processing chamber to form chemical species that contribute to etching;
And a step of etching the silicon oxide film or the silicon nitride film with the chemical species. The method according to claim 1, wherein the carbon is solid carbon. 3. The method of manufacturing a semiconductor device according to claim 2 , wherein the temperature of the solid carbon is controlled. The method of manufacturing a semiconductor device according to claim 3, wherein the temperature is controlled in a range of −60 ° C. to + 250 ° C. 5. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the temperature is controlled in the range of 0.degree. C. to + 250.degree. 3. The method of manufacturing a semiconductor device according to claim 2 , wherein electric power is input to the solid carbon. 7. The method of manufacturing a semiconductor device according to claim 6, wherein the electric power is controlled to obtain a desired etching rate of the solid carbon. 7. The method of manufacturing a semiconductor device according to claim 6 , wherein there are a plurality of solid carbons, and a predetermined power is supplied to each of the plurality of carbons. The plasma method according to claim 1, wherein a is formed by a synergistic action between the high frequency and the magnetic field in the UHF band. The gas containing fluorine but not carbon is SF ₆ , ClF ₃ , F ₂ , HF, XeF ₂ , PF ₃ , BF ₃ , NF ₃ , SiF ₄ , ClF, BrF, BrF ₃ , BrF ₅ , IF _5. the method according to claim 1, wherein the containing either. Forming a silicon oxide film or a silicon nitride film on the substrate;
Forming a resist film having a predetermined pattern on the silicon oxide film or silicon nitride film;
Installing the substrate on which the resist film is formed in a processing chamber;
Introducing a gas containing fluorine as a constituent element and not carbon as a constituent element into the processing chamber;
Converting the gas into plasma by applying high-frequency power to solid carbon installed in the processing chamber;
Reacting the plasma gas with the carbon to form chemical species that contribute to etching;
Supplying power to accelerate the ions in the plasma to the substrate;
And a step of etching the silicon oxide film or the silicon nitride film with the chemical species. Forming a silicon oxide film or a silicon nitride film on the substrate;
Forming a resist film having a predetermined pattern on the silicon oxide film or silicon nitride film;
Installing the substrate on which the resist film is formed on a table in a processing chamber;
Introducing a gas containing oxygen into the processing chamber and a compound gas containing fluorine as a constituent element and not carbon as a constituent element;
Converting the compound gas into plasma;
Reacting the plasmatized compound gas with carbon prepared in the processing chamber to form chemical species that contribute to etching;
And a step of etching the silicon oxide film or the silicon nitride film with the chemical species. Forming a silicon oxide film or a silicon nitride film on the substrate;
Forming a resist film having a predetermined pattern on the silicon oxide film or silicon nitride film;
Installing the substrate on which the resist film is formed on a table in a processing chamber;
Introducing a gas containing fluorine into the processing chamber and a gas containing carbon at a flow rate of 1% or less of the total flow rate of the gas introduced into the processing chamber;
Converting the gas into plasma;
Reacting the plasma gas with carbon prepared in the processing chamber to form chemical species that contribute to etching;
And a step of etching the silicon oxide film or the silicon nitride film with the chemical species. 14. The method of manufacturing a semiconductor device according to claim 13 , wherein the flow rate of the gas containing carbon is 0.4% or more and 0.8% or less of the total flow rate. Installing a substrate on which a silicon oxide film or a silicon nitride film is formed on a table in a processing chamber;
Introducing an inert gas, a gas containing fluorine, and a gas containing a smaller amount of carbon than the gas containing fluorine into the processing chamber;
Converting the gas into plasma;
A step of reacting the plasma gas with carbon prepared in the processing chamber to form chemical species necessary for etching, and etching the silicon oxide film or silicon nitride film. Manufacturing method.

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