JP4200568B2 - Electronic device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic device and a method for manufacturing the same, and more particularly, an electronic device having improved adhesion by preventing oxidation of metal wiring when a silicon nitride insulating film is formed on an easily oxidizable metal wiring, and the same It relates to a manufacturing method.
[0002]
[Prior art]
As the degree of integration of semiconductor devices such as ULSI (Ultra Large Scale Integrated Circuits) increases, it is necessary to reduce the wiring width and wiring pitch. The reduction of the wiring width and the wiring pitch simultaneously increases the aspect ratio of the wiring cross section and the aspect ratio of the space between the wirings. As a result, the burden is concentrated on etching technology that processes fine, high-aspect ratio wiring, and technology that embeds fine, high-aspect-ratio inter-wiring spaces with an interlayer insulating layer. It is causing an increase.
[0003]
At the same time as miniaturization, in order to meet the demands for low power consumption and high operating speed of various semiconductor devices including high-speed logic semiconductor devices, in addition to interlayer dielectric film materials with low dielectric constant, The selection of a low-resistance electrode wiring material and its process technology are becoming increasingly important as elemental technologies. This is also an important problem in various high-frequency fine electronic devices other than semiconductor devices.
[0004]
Conventionally, aluminum-based metals such as Al—Si and Al—Si—Cu having a relatively low resistance have been used as electrode wiring materials for semiconductor devices and the like. However, as a next-generation electrode wiring material, Cu having a smaller specific resistance than Al and excellent in electromigration and stress migration resistance is considered promising. The specific resistance of Cu is 1.72 μΩ-cm, which is about 60% of the specific resistance of Al 2.7 μΩ-cm. As the Cu film forming method, in addition to the sputtering method, the CVD (Chemical Vapor Deposition) method and the like, an electrolytic plating method can also be applied.
[0005]
As a low dielectric constant interlayer insulating film, conventional SiO ₂ SiOF in which fluorine is introduced into (relative dielectric constant 4) is known. SiOF is SiO ₂ By terminating the Si—O—Si bond constituting the structure with F atoms, the density thereof is reduced, and the polarizability of the Si—F bond and the O—F bond is low. ₂ A lower dielectric constant is achieved. This SiOF has the same film formation and etching process as conventional SiOF. ₂ Since it is similar to the above, it can be easily adopted in the current manufacturing apparatus. Moreover, since it is an inorganic material, it is excellent also in heat resistance. However, the relative dielectric constant of SiOF is only about 3.7 to 3.2.
[0006]
An organic insulating film material containing carbon atoms is also known as a low dielectric constant interlayer insulating layer. That is, organic SOG (Spin On Glass), polyaryl ether, polyimide, polyparaxylylene (trade name Parylene), benzocyclobutene, polynaphthalene, etc., organic polymers having a relative dielectric constant of about 2.5 to 3.5 Material. Since these materials contain carbon atoms, the density thereof is reduced, and the low dielectric constant is achieved by reducing the polarizability of the molecules (monomers) themselves. Moreover, a certain degree of heat resistance is obtained by introducing a siloxane bond, an imide bond, or a benzene ring or a naphthalene ring.
[0007]
A fluorocarbon polymer in which fluorine atoms are further introduced into these hydrocarbon-based organic materials has a relative dielectric constant of about 1.5 to 2.5, which can further reduce the dielectric constant and improve heat resistance. As such an organic material of a fluororesin, perfluoro group-containing polyimide, fluorinated polyaryl ether, Teflon (trade name), flare (trade name), and the like are known. These organic low dielectric constant materials are introduced in, for example, “Nikkei Microdevice” magazine, July 1995, pages 105-112.
[0008]
The organic low dielectric constant interlayer insulating film is significantly different in film quality from the conventional silicon oxide interlayer insulating film. In particular, an organic low dielectric constant interlayer insulating film having a relative dielectric constant of 2.5 or less, which is being studied for introduction into a semiconductor device having a minimum design rule of 0.18 μm, is required to have improved adhesion to the underlying layer.
[0009]
There is a method called Damascene or Dual Damascene as a process when these low-resistance electrode wiring materials are applied to a highly integrated semiconductor device or the like, preferably in combination with an interlayer insulating film having a low dielectric constant. These are technologies in which metal wiring materials are embedded in wiring grooves or wiring holes and wiring holes formed in advance in the interlayer insulating film by reflow sputtering or electrolytic plating, and the surface is flattened by CMP (Chemical mechanical polishing). It is. The Damascene or Dual Damascene process does not require high-aspect-ratio wiring to be patterned by etching, and the space between the wirings need not be filled with an interlayer insulating film. Therefore, this process contributes to the reduction rate of the number of manufacturing steps as the wiring aspect ratio increases and the number of wiring layers increases.
[0010]
[Problems to be solved by the invention]
The problem in the process of forming oxidizable metal wiring such as Cu, including Damascene or Dual Damascene processes, is that the wiring resistance value increases due to oxidation when the insulating film is formed on the metal wiring, and the adhesion to the insulating film It is a problem of decline in sex. In particular, since Cu wiring does not form a passive film, the progress of oxidation cannot be prevented. Therefore, in the step of forming the insulating film on the metal wiring, it is necessary to prevent the underlying metal wiring from being oxidized as much as possible, and also after the insulating film is formed, it is necessary to consider the oxidation by oxygen passing through the insulating film. .
[0011]
When an insulating film is formed on a metal wiring by a CVD (Chemical Vapor Deposition) method, the temperature of the substrate to be processed is usually set to 200 ° C. or higher. The oxidation reaction rate of the metal wiring in this temperature range is 10 times the normal temperature. It is very easy to oxidize. The ultimate vacuum of the dry pump attached to a normal CVD apparatus is 1 × 10 ^-3 It is about Torr. Assuming that 20% of oxygen is contained in the atmosphere, the partial pressure ratio remains at 1 × 10 ^-3 When evacuated to Torr, the oxygen concentration is about 260 ppb. Thus, even if it becomes trace oxygen concentration, the progress of oxidation of Cu wiring cannot be prevented at 200 ° C. or higher. In the case of a sputtering apparatus, the displacement is large and the ultimate vacuum is 1 × 10. ^-7 A cryopump that is equal to or lower than Torr can be used, and at this degree of vacuum, the oxygen concentration is low, and oxidation of the metal wiring can be prevented. However, in a CVD apparatus, a cryopump cannot be used because of a reaction gas or a side reaction product.
[0012]
As described above, the formation of the insulating film by the CVD method on the easily oxidizable metal wiring such as Cu is inconvenient to introduce the oxygen gas to form the silicon oxide insulating film, and does not use the oxygen gas. Care must also be taken when forming the silicon nitride insulating film.
[0013]
The present invention has been made in view of such problems of the prior art. That is, an object of the present invention is to provide a method capable of preventing oxidation of metal wiring and deterioration of adhesion when forming a silicon nitride insulating film on an easily oxidizable metal wiring such as Cu.
[0014]
Another object of the present invention is to provide an electronic device such as a highly reliable highly integrated semiconductor device having a low resistance wiring manufactured by such a method.
[0015]
[Means for Solving the Problems]
In order to achieve the above-described problem, the method for manufacturing an electronic device according to the present invention forms a silicon nitride insulating film on a metal wiring embedded in a wiring groove formed in a low dielectric constant insulating film by a vapor deposition method. A method of manufacturing an electronic device having a process, in contact with the metal wiring, ₃ N ₄ Forming a Si-rich lower silicon nitride insulating film with a Si stoichiometric composition, and being in contact with the lower silicon nitride insulating film and being N-rich and more chemical than the lower silicon nitride insulating composition amount And a step of forming an upper silicon nitride insulating film having a theoretical composition.
[0016]
Another method of manufacturing an electronic device according to the present invention is an electronic device having a step of forming a silicon nitride insulating film by vapor phase growth on a metal wiring buried in a wiring groove formed in a low dielectric constant insulating film. A manufacturing method, in contact with this metal wiring, Si ₃ N ₄ Forming a lower silicon nitride insulating film rich in Si than the stoichiometric composition, and in contact with the lower silicon nitride insulating film, the composition of the lower silicon nitride insulating film gradually increases N toward the film surface. Rich, chemical on the outermost layer amount And a step of forming an upper silicon nitride insulating film close to the theoretical composition.
[0017]
In any method of manufacturing an electronic device, in the step of forming this silicon nitride insulating film by vapor deposition,
It is desirable to form it while controlling the oxygen concentration in the vapor deposition chamber to 100 ppb (parts per billion) or less.
[0018]
Furthermore, prior to the step of forming this silicon nitride insulating film by vapor deposition,
It is desirable to reverse-sputter the underlying metal wiring surface in a non-oxidizing reduced pressure atmosphere. Non-oxidizing reduced-pressure atmosphere is H ₂ Or a reduced pressure atmosphere of a reducing gas such as Ar or an inert gas such as Ar.
[0019]
Furthermore, following the step of forming this silicon nitride insulating film by vapor deposition,
Reverse sputtering of the formed silicon nitride insulating film surface,
Thereafter, it is desirable to further form an insulating film in contact with the silicon nitride insulating film.
The reverse sputtering process at any stage is performed by a silicon nitride insulating film using an apparatus capable of high-pressure plasma CVD of 1 to 10 mTorr, such as an ECR plasma CVD apparatus, an ICP-CVD apparatus, or a helicon wave plasma CVD apparatus. However, this is not always necessary because the residual oxygen concentration is low. Conversely, when a silicon nitride insulating film is formed using a parallel plate type plasma CVD apparatus, the residual oxygen concentration is relatively high, and therefore it is desirable to perform reverse sputtering treatment. In this case, it is more desirable to perform reverse sputtering after purging the inside of the chamber with an inert gas such as nitrogen.
[0020]
Next, an electronic device according to the present invention is an electronic device having a silicon nitride insulating film on a metal wiring buried in a wiring groove formed in a low dielectric constant insulating film, and is in contact with the metal wiring. ₃ N ₄ The lower silicon nitride insulating film that is richer in Si than the stoichiometric composition, and the lower silicon nitride insulating film in contact with the lower silicon nitride insulating film is N richer and more chemical. amount It has an upper silicon nitride insulating film close to the theoretical composition.
[0021]
Another electronic device according to the present invention is an electronic device having a silicon nitride insulating film on a metal wiring embedded in a wiring groove formed in a low dielectric constant insulating film, and is in contact with the metal wiring. ₃ N ₄ From the composition of the lower silicon nitride insulating film rich in Si than the stoichiometric composition and the lower silicon nitride insulating film in contact with the lower silicon nitride insulating film, the outermost silicon layer gradually becomes N rich toward the film surface. In chemistry amount It has an upper silicon nitride insulating film close to the theoretical composition.
[0022]
In any electronic device, the thickness of the silicon nitride insulating film is desirably 30 nm or more and 150 nm or less, and more desirably 50 nm or more and 100 nm or less.
[0023]
In any electronic device, it is desirable to further have an insulating film in contact with the silicon nitride insulating film.
[0024]
Examples of the electronic device targeted by the present invention include a highly integrated semiconductor device using an easily oxidizable metal wiring such as Cu, a thin film magnetic head device, a thin film coil, a thin film inductor, or a micromachine.
[0025]
(Function)
A silicon nitride insulating film is employed as the insulating film formed on the metal wiring, and oxygen is eliminated from the film forming atmosphere as much as possible to prevent oxidation of the metal wiring. At this time, by using a turbo molecular pump as a vacuum pump attached to the film forming apparatus, oxidation of the metal wiring can be more effectively prevented. The ultimate vacuum of the turbo molecular pump is 1 × 10 ^-6 The oxygen concentration is less than Torr, and theoretically can be 1 ppb or less.
[0026]
Even if a silicon nitride insulating film is formed at such a low oxygen concentration, there is still a possibility that the metal wiring is oxidized. In this case, if a silicon nitride insulating film is formed after removing the oxide film on the surface of the metal wiring by reverse sputtering using a film forming apparatus capable of applying a substrate bias, oxidation of the metal wiring is more effective. Can be prevented.
[0027]
The silicon nitride insulating film in contact with the metal wiring affects the adhesion between them. For this reason, the silicon nitride insulating film of this part is made of Si. _Three N _Four By making the composition richer than the stoichiometric composition, the reaction activity is increased and the adhesion can be improved. The upper silicon nitride insulating film is made of Si from the viewpoint of securing insulation properties. _Three N _Four The stoichiometric composition is desirable. The lower and upper silicon nitride insulating films may change sharply at the interface or may change smoothly at the gradient composition.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a highly integrated semiconductor device will be taken as an example of an electronic device, and a method of forming an interlayer insulating film including a silicon nitride insulating film on a Cu metal wiring formed by a Damascene process will be described as an example. The electronic device is not limited to a semiconductor device, but can be applied to various electronic devices such as thin film magnetic heads, magnetoresistive heads, thin film inductors, thin film coils, and micromachines, particularly those employing low resistance Cu wiring. it can.
[0029]
FIG. 1 is a schematic cross-sectional view showing a main part of a highly integrated semiconductor device as an example of the electronic device of the present invention.
That is, a wiring groove 3 is formed in the interlayer insulating film 2 on the semiconductor substrate 1 such as Si, and the metal wiring 4 is embedded in the wiring groove 3. A silicon nitride insulating film 5 and an insulating film 6 are formed on the metal wiring 4.
The structure shown in FIG. 1 shows only the main parts related to the present invention, and illustration of MOS transistors, element isolation regions, or upper layer wirings formed on the semiconductor substrate 1 is omitted. Further, the dimensions of each component are not proportional to the actual semiconductor device.
[0030]
The interlayer insulating film 2 is generally composed of a silicon oxide insulating film. The silicon oxide insulating film is, for example, SiH _Four And O ₂ It is formed by a low pressure CVD method using a gas as a source gas, a plasma CVD method using TEOS (Tetraethyl Orthosilicate) as a source gas, or the like. The interlayer insulating film 2 is composed of a low dielectric constant insulating film, a low dielectric constant insulating film and SiO. ₂ You may comprise by lamination | stacking of inorganic insulating films, such as. By adopting a laminated structure with an inorganic insulating film, it is possible to reinforce a low dielectric constant insulating film generally having a low mechanical strength and improve the reliability of a semiconductor device. Of course, the use of a low dielectric constant insulating film can reduce the capacitance between wirings.
[0031]
As the low dielectric constant insulating film, in addition to inorganic insulating films such as SiOF and xerogel (porous silicon oxide film), organic SOG, polyaryl ether, polyimide, polyparaxylylene (trade name Parylene), benzocyclobutene Polynaphthalene, fluororesin, or the like can be used.
[0032]
The metal wiring 4 may be a groove wiring or a contact plug with an impurity diffusion layer (not shown) formed in the semiconductor substrate 1. Moreover, the structure which integrated the groove | channel wiring and the contact plug may be sufficient. In the case of a contact plug, a via contact plug facing a lower layer wiring (not shown) may be used.
The metal wiring 4 may have a barrier metal structure. In this case, a stacked structure of TaN and Cu, a stacked structure of Ta and Cu, a stacked structure of TiN and Al—Cu alloy, or the like is employed. If Cu is used, the wiring becomes low resistance, and if an Al—Cu alloy is used, wiring with a relatively low resistance and low cost can be provided. As a material of the metal wiring 4, W, Mo, Ag, or the like may be adopted.
Other materials for barrier metal include W ₂ N, Ta ₂ N or Mo ₂ N or the like may be adopted. That is, it is desirable to use a low-order nitride of a refractory metal that is not formed into a columnar or granular crystal structure but is formed as an amorphous or microcrystal close to an amorphous state.
The barrier metal is formed not only by a sputtering method or a reactive sputtering method but also by a CVD method or a plasma CVD method. In this case, the raw material gas employed is WF. ₆ , WCl ₆ , TaBr _Five , MoF ₆ , MoCl _Five A metal halide such as fluoride, chloride or bromide, which has a relatively high vapor pressure and is easily vaporized, or an organic metal compound is employed. Nitride gas used as a mixture is N ₂ , NH _Three Or N ₂ H ₂ Etc. are exemplified.
[0033]
The metal wiring 4 can be formed by sputtering, CVD, electrolytic plating, or the like. In any method, the excess wiring material formed also on the interlayer insulating film 2 is removed by a CMP (Chemical Mechanical Polishing) method, and the surface is formed flat.
[0034]
Now, the silicon nitride-based insulating film 5 is composed of two layers, which are made of Si. _Three N _Four The lower silicon nitride insulating film 5a is richer in Si than the stoichiometric composition, and the upper silicon nitride insulating film 5b is richer in N than the lower silicon nitride insulating film 5a. The upper silicon nitride insulating film 5b may have a graded composition that gradually becomes N rich toward the surface. The silicon nitride insulating film 5 is manufactured by the method of the present invention.
[0035]
The film thickness of the lower silicon nitride insulating film 5a is desirably 10 nm or more. If the film thickness is less than 10 nm, the metal wiring 4 may be nitrided when the upper silicon nitride insulating film 5b is formed, and the adhesion between them may be reduced. The total thickness of the silicon nitride insulating film 5 is preferably 30 nm or more and 150 nm or less, and more preferably 50 nm or more and 100 nm or less. If it is less than 30 nm, the effect of preventing the diffusion of metal in the metal wiring 4 is poor. In particular, Cu is easily diffused, and when it is used for the metal wiring 4, it is necessary to reliably suppress the diffusion. On the other hand, if it exceeds 150 nm, the capacitance between the wirings is increased and the device characteristics are deteriorated.
[0036]
As a method for forming the silicon nitride insulating film 5, a vapor phase growth method such as a plasma CVD method or a sputtering method, which can be formed at a low temperature, is employed. In addition to the method using silicon nitride as a target, the sputtering method uses silicon as a target and Ar is replaced with N. ₂ And NH _Three A reactive sputtering method to which is added is employed. At this time, N ₂ And NH _Three The composition of the silicon nitride insulating film 5 can be controlled by controlling the amount of addition.
[0037]
The silicon nitride insulating film 5 can also be formed by a plasma CVD method. 1 × 10 as plasma generation source ^Ten / Cm ^Three It is particularly preferable to use a plasma CVD apparatus having a high-density plasma generation source that can obtain an electron density of a degree or more. High density plasma CVD equipment is 1 × 10 ^-3 Plasma generation at a high vacuum level of about Torr is possible, and the ultimate vacuum level of the turbo molecular pump (1 × 10 ^-6 Consistency with Torr). Examples of these high-density plasma CVD apparatuses include an ECR (Electron Cyclotron Resonance) plasma CVD apparatus, an ICP (Inductively Coupled Plasma) CVD apparatus, and a helicon wave plasma CVD apparatus. Furthermore, it is desirable to use a plasma CVD apparatus that can independently control a power source for generating plasma and a power source for applying a substrate bias. Thereby, reverse sputtering can be performed in the same film formation chamber.
[0038]
A normal parallel plate type plasma CVD apparatus can also be used as the plasma CVD apparatus. Parallel plate type plasma CVD equipment is 1 × 10 ^-2 Since the plasma is generated at a vacuum level of about Torr, the film forming chamber is purged with an inert gas having a small residual oxygen such as high purity nitrogen and then evacuated to obtain an oxygen concentration of 100 ppb or less, and then the silicon nitride insulating film is formed. It is desirable to form a film.
[0039]
Prior to forming the lower silicon nitride insulating film 5a, it is desirable to remove an oxide film (not shown) formed on the surface of the metal wiring 4 by reverse sputtering. In the reverse sputtering, a rare gas such as He, Ar, Xe, Kr or Ne is used. H to these rare gases ₂ Or SiH _Four A reducing gas such as may be added.
The reverse sputtering may be performed in the same film formation chamber of the silicon nitride insulating film forming apparatus, or may be performed here by providing a pretreatment chamber dedicated to reverse sputtering. In this case, the pretreatment chamber and the film formation chamber are connected by a vacuum gate valve to prevent reoxidation during the transfer.
[0040]
The insulating film 6 is formed as necessary when the silicon nitride insulating film 5 is thin. The material of the insulating film 6 is silicon oxide or the above-described low dielectric constant insulating film. Silicon oxide has no problem in reliability, but has a problem in terms of dielectric constant. On the contrary, the low dielectric constant insulating film may reduce reliability.
Before forming the insulating film 6, the surface of the underlying upper silicon nitride insulating film 5b may be reverse-sputtered. The reverse sputtering at this time is performed in order to improve the adhesion of the insulating film 6.
[0041]
An interlayer insulating film and an upper metal wiring are further formed on the silicon nitride insulating film 5 or the insulating film 6 as necessary, and finally a passivation film is formed to complete the semiconductor device.
[0042]
【Example】
Hereinafter, the method for manufacturing an electronic device according to the present invention will be described in more detail with reference to FIGS. 2 to 3 by taking a method for manufacturing a highly integrated semiconductor device as an example. However, this embodiment is merely an example, and the present invention is not limited to this embodiment.
[0043]
[Example 1]
In this embodiment, Si is used as the lower silicon nitride insulating film 5a on the metal wiring. _Three N _Four This is an example in which silicon nitride richer than the stoichiometric composition is formed, and silicon nitride richer in N than the lower silicon nitride insulating film 5a is formed as the upper silicon nitride insulating film 5b.
[0044]
FIG. 2A: an interlayer insulating film 2 is formed on a semiconductor substrate 1 such as Si. ₂ A state is shown in which a wiring trench 3 is formed in the interlayer insulating film 2 so as to face an impurity diffusion layer (not shown) of a predetermined element such as a MOS transistor formed in the semiconductor substrate 1.
[0045]
The interlayer insulating film 2 is SiH _Four And O ₂ Was formed by a CVD method using as a source gas.
In the step of forming the wiring trench 3, first, a photoresist is coated on the interlayer insulating film 2, and a resist mask (not shown) is formed by patterning the opening shape of the wiring trench. This substrate to be etched was carried into, for example, a magnetron RIE apparatus and patterned under the following etching conditions.
Etching conditions for wiring trench formation
C _Four F ₈ 14 sccm
CO 250 sccm
Ar 100 sccm
O ₂ 2 sccm
Pressure 5.3 Pa
RF power 1.6 kW
Temperature 20 ℃
In addition to the contact plug connection hole, the wiring groove 3 may be a simple groove wiring formation or a via contact plug.
The shape of the wiring groove 3 is, for example, an opening diameter of 0.2 μm, a depth of 1.0 μm, and an aspect ratio of 5.
[0046]
FIG. 2B: The substrate to be processed shown in FIG. 2A is carried into an ECR plasma processing apparatus, and a barrier metal made of TaN is formed.
As source gas, TaBr _Five And N ₂ The mixed gas was introduced. TaBr _Five Is solid at a normal temperature of mp = 265 ° C. and bp = 348.8 ° C., and is heated and vaporized and introduced into the plasma generation chamber.
TaBr _Five 2-10 sccm
N ₂ 5-20 sccm
H ₂ 100-300 sccm
Ar 100-200 sccm
Pressure 1-10 mTorr
μ wave power 1-3 kW
Temperature 200-400 ° C
Before forming the barrier metal, the surface of the substrate to be processed may be reverse-sputtered.
[0047]
Thereafter, Cu is formed by an electrolytic plating method or the like to form the metal wiring 4. The metal wiring 4 is also formed on the interlayer insulating film 2. The metal wiring 4 on the interlayer insulating film 2 is not necessary.
[0048]
FIG. 2C: Therefore, the metal wiring 4 on the interlayer insulating film 2 is removed and flattened by a known CMP (Chemical Mechanical Polishing) method or a whole surface etchback method, and is embedded in the wiring trench 3.
[0049]
The substrate to be processed shown in FIG. 2C is carried into an ECR plasma CVD apparatus and subjected to reverse sputtering. This ECR plasma CVD apparatus has a vacuum degree of 1 × 10 using a turbo molecular pump. ^-6 Torr or less can be achieved. A vacuum is drawn to this degree of vacuum, and the post-treatment gas is introduced and the substrate to be treated is heated.
H ₂ 200-500 sccm
Ar 100-300 sccm
Pressure 1-10 mTorr
μ wave power 1-3 kW
Bias power 500 W
Temperature 200-400 ° C
Although reverse sputtering using only Ar is possible, in this case, since there is no reduction action, the effect of removing the natural oxide film by chemical reaction or reducing the residual oxygen concentration cannot be expected, and the processing time becomes longer. H ₂ With a simple gas, it is difficult to stably generate and sustain plasma.
[0050]
This reverse sputtering process is performed in order to remove the natural oxide film on the surface of the metal wiring 4 and to reduce the residual oxygen concentration in the chamber when forming the lower layer silicon nitride insulating film in a later step. This also improves the adhesion of the lower silicon nitride insulating film. This reverse sputtering treatment is not necessarily performed when plasma CVD at a high vacuum of 1 to 10 mTorr is possible as in an ECR plasma CVD apparatus. However, when a parallel plate type plasma CVD apparatus is used, it is desirable to apply.
[0051]
FIG. 3D: Thereafter, a lower silicon nitride insulating film 5a is formed to 10 nm on the cleaned metal wiring 4.
SiH _Four 25-50 sccm
N ₂ 25-50 sccm
Pressure 1-10 mTorr
μ wave power 1-3 kW
Temperature 200-400 ° C
This film forming condition is SiH _Four And N ₂ The flow ratio of is 1 and Si _Three N _Four Thus, a silicon nitride insulating film having a larger Si amount than the stoichiometric composition is formed. The film formation rate is about 100 nm / min, and the film thickness control is relatively easy.
[0052]
FIG. 3E: Subsequently, the upper silicon nitride insulating film 5b is continuously formed.
SiH _Four 25-50 sccm
N ₂ 50-150 sccm
Pressure 1-10 mTorr
μ wave power 1-3 kW
Temperature 200-400 ° C
This film forming condition is SiH _Four And N ₂ The flow rate ratio is 2 or more and is N richer than the underlying lower silicon nitride insulating film 5a, that is, Si _Three N _Four A silicon nitride insulating film close to the stoichiometric composition is formed. The upper silicon nitride insulating film 5b has a thickness of 70 nm. Therefore, the total thickness of the silicon nitride insulating film 5 is 80 nm.
[0053]
N as nitriding gas ₂ Instead of NH _Three Can be used, but NH _Three Has a strong nitriding effect, and may cause nitriding of the metal wiring 4. Therefore, when the lower silicon nitride insulating film 5a is thin, N is used as the nitriding agent gas. ₂ It is desirable to use
[0054]
Thereafter, a reverse sputtering process is performed on the surface of the upper silicon nitride insulating film 5b in the same ECR plasma CVD apparatus. This reverse sputtering may be performed with Ar gas alone. Further, reverse sputtering is performed in order to improve the adhesion when an insulating film is further formed on the silicon nitride insulating film 5. In particular, it is desirable to perform reverse sputtering when forming an organic low dielectric constant film, SOG, or the like by a coating method.
This reverse sputtering process is not necessarily performed when plasma CVD at a high vacuum of 1 to 10 mTorr is possible as in the ECR plasma CVD apparatus. However, when a parallel plate type plasma CVD apparatus is used, it is desirable to apply.
[0055]
FIG. 3F: An insulating film 6 is further formed on the silicon nitride insulating film 5 as necessary. This insulating film 6 is necessary when the thickness of the silicon nitride insulating film 5 is small and the insulation withstand voltage as an interlayer insulating film is insufficient or the wiring capacity increases.
As the insulating film, the material of the interlayer insulating film 2 is SiO. ₂ Alternatively, various low dielectric constant films are employed, and the film formation method may be in accordance with the film formation method of the interlayer insulating film 2 described above.
[0056]
In the subsequent steps, when an upper-layer metal wiring structure is formed, the process of FIGS. 2A to 3F may be repeated by returning to FIG. Finally, a final passivation film and a pad electrode are formed to complete the semiconductor device.
[0057]
[Example 2]
The upper silicon nitride insulating film 5b constituting the silicon nitride insulating film 5 may have a gradient composition that gradually becomes N rich toward the surface. In this embodiment, only the step of forming the silicon nitride insulating film 5 will be described with reference to FIGS.
[0058]
2A to 2C are the same as those in the first embodiment from the metal wiring formation process to the CMP process, and a duplicate description is omitted.
[0059]
FIG. 3D: Thereafter, a lower silicon nitride insulating film 5a is formed to 10 nm on the cleaned metal wiring 4.
SiH _Four 30 sccm
N ₂ 30 sccm
Pressure 1-10 mTorr
μ wave power 1-3 kW
Temperature 200-400 ° C
This film forming condition is SiH _Four And N ₂ The flow ratio of is 1 and Si _Three N _Four Thus, a silicon nitride insulating film having a larger Si amount than the stoichiometric composition is formed. The film formation rate is also about 100 nm / min, and the film thickness control is relatively easy.
[0060]
FIG. 3E: Subsequently, the upper silicon nitride insulating film 5b is continuously formed.
SiH _Four 30 sccm
N ₂ 30 → 100 sccm
Pressure 1-10 mTorr
μ wave power 1-3 kW
Temperature 200-400 ° C
This film forming condition is N ₂ Gradually increase the flow rate and finally SiH _Four And N ₂ The flow rate ratio is set to 2 or more. As a result, the N concentration gradually increases toward the surface, and Si is formed on the outermost layer. _Three N _Four An upper silicon nitride insulating film 5b close to the stoichiometric composition is formed. The upper silicon nitride insulating film 5b has a thickness of 70 nm. Therefore, the total thickness of the silicon nitride insulating film 5 is 80 nm.
The gradient composition of the upper silicon nitride insulating film 5b may be inclined over the entire thickness of the upper silicon nitride insulating film 5b or may be only a part below the upper silicon nitride insulating film 5b.
[0061]
By making the upper silicon nitride insulating film 5b have a gradient composition, the entire silicon nitride insulating film 5 can eliminate abrupt composition fluctuation at the interface, and effects such as improved adhesion and reduced film stress can be obtained. .
The subsequent steps may be the same as in the first embodiment.
[0062]
Also in this embodiment, the reverse sputtering process before and after the formation of the silicon nitride insulating film 5 is not necessarily performed when plasma CVD in a high vacuum of 1 to 10 mTorr is possible as in the ECR plasma CVD apparatus. . However, when a parallel plate type plasma CVD apparatus is used, it is desirable to apply.
[0063]
Although the present invention has been described with two examples, the silicon nitride insulating film forming process may employ various plasma CVD methods, low pressure CVD methods, reactive sputtering methods, etc. in addition to the ECR plasma CVD method. it can. In any method, it is desirable to control the oxygen concentration in the vapor phase growth chamber before and during film formation to 100 ppb or less.
[0064]
The present invention is particularly preferably applied to an electronic device that employs easily oxidizable Cu or the like as a metal wiring, but may be applied to an electronic device using a metal wiring such as an Al alloy, a refractory metal, or Ag. Good results can be achieved.
[0065]
In addition, it is excellent in adaptability in an electronic device in which a low dielectric constant insulating film or an interlayer insulating film and a silicon nitride insulating film are combined, in which adhesion is a problem. Examples of the organic polymer material include polyaryl ether, polyimide, organic SOG, benzocyclobutene, polynaphthalene, polyparaxylylene, Teflon (trade name), Cytop (trade name), and the like. These are all low dielectric constant materials desirable as insulating films for highly integrated electronic devices.
[0066]
The electronic device and the manufacturing method thereof according to the present invention are suitably used for multilayer wiring of a highly integrated semiconductor device, etc., but it is desired to reduce wiring capacitance and wiring resistance. The present invention can be applied to a manufacturing method of various electronic devices such as a resistance effect type head, a thin film inductor, a thin film coil, and a micromachine.
[0067]
【The invention's effect】
As is apparent from the above description, according to the method for manufacturing an electronic device of the present invention, undesired oxidation of metal wiring is prevented, and there are effects such as reduction of wiring resistance and improvement of adhesion.
[0068]
In addition, according to the electronic device of the present invention, the original low resistance performance of an easily oxidizable metal wiring such as Cu can be effectively realized, and the adhesion can be improved by combining with an organic low dielectric constant insulating film in which adhesion is a problem. Various electronic devices that are improved and highly reliable can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a main part of a highly integrated semiconductor device which is an example of an electronic device of the present invention.
FIG. 2 is a schematic cross-sectional view showing a manufacturing process of a highly integrated semiconductor device which is an example of the electronic device of the invention.
FIG. 3 is a schematic cross-sectional view showing a manufacturing process of a highly integrated semiconductor device which is an example of the electronic device of the present invention, showing a process following FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Interlayer insulating film, 3 ... Wiring groove, 4 ... Metal wiring, 5 ... Silicon nitride type insulating film, 5a ... Lower layer silicon nitride type insulating film, 5b ... Upper layer silicon nitride type insulating film, 6 ... Insulation film

Claims (16)

A method of manufacturing an electronic device comprising a step of forming a silicon nitride-based insulating film on a metal wiring buried in a wiring groove formed in a low dielectric constant insulating film by a vapor deposition method,
Forming a lower silicon nitride insulating film rich in Si than the stoichiometric composition of Si ₃ N _{4 in} contact with the metal wiring;
The contact with the lower silicon nitride insulation film, method for manufacturing an electronic device having a step of forming an upper silicon nitride insulation film close to the stoichiometric composition with N-rich than the composition of the lower layer silicon nitride insulation film. A method of manufacturing an electronic device comprising a step of forming a silicon nitride-based insulating film on a metal wiring buried in a wiring groove formed in a low dielectric constant insulating film by a vapor deposition method,
Forming a lower silicon nitride insulating film rich in Si than the stoichiometric composition of Si ₃ N _{4 in} contact with the metal wiring;
In contact with the lower silicon nitride insulation film, formed from the composition of the lower layer silicon nitride insulation film, becomes gradually N-rich towards the membrane surface direction, the upper silicon nitride insulation film becomes closer to the stoichiometric composition in the outermost layer The manufacturing method of the electronic device which has a process to do.   The low dielectric constant insulating film is one of SiOF, xerogel (porous silicon oxide film), organic SOG (Spin On Glass), polyaryl ether, polyimide, polyparaxylylene, benzocyclobutene, polynaphthalene, and fluororesin. The method for manufacturing an electronic device according to claim 1 or 2, wherein the method is one.   The method for manufacturing an electronic device according to claim 1, wherein the metal wiring is formed from an easily oxidizable metal.   The method of manufacturing an electronic device according to claim 4, wherein the oxidizable metal is formed as Cu, Al—Cu alloy, W, Mo, Ag, or a laminated structure of these and a barrier metal.   3. The method of manufacturing an electronic device according to claim 1, wherein in the step of forming the silicon nitride insulating film by a vapor deposition method, the silicon nitride insulating film is formed while controlling an oxygen concentration in the vapor deposition chamber to 100 ppb or less.   3. The method of manufacturing an electronic device according to claim 1, wherein the metal wiring surface is reverse-sputtered in a non-oxidizing reduced-pressure atmosphere prior to the step of forming the silicon nitride insulating film by a vapor phase growth method. Subsequent to the step of forming the silicon nitride insulating film by vapor deposition, the silicon nitride insulating film surface is reverse-sputtered,
3. The method of manufacturing an electronic device according to claim 1, wherein an insulating film is further formed on and in contact with the silicon nitride insulating film. An electronic device having a silicon nitride insulating film on a metal wiring buried in a wiring groove formed in a low dielectric constant insulating film,
A lower silicon nitride based insulating film that is in contact with the metal wiring and is richer in Si than the stoichiometric composition of Si ₃ N ₄ ;
The lower silicon nitride in contact with the insulating film, an electronic device having upper silicon nitride insulation film close to the stoichiometric composition with N-rich than the composition of the lower layer silicon nitride insulation film. An electronic device having a silicon nitride insulating film on a metal wiring buried in a wiring groove formed in a low dielectric constant insulating film,
A lower silicon nitride based insulating film that is in contact with the metal wiring and is richer in Si than the stoichiometric composition of Si ₃ N ₄ ;
In contact with the lower silicon nitride insulation film, than the composition of the lower layer silicon nitride insulation film, becomes gradually N-rich towards the membrane surface direction, electrons having upper silicon nitride insulation film becomes closer to the stoichiometric composition in the outermost layer apparatus.   The low dielectric constant insulating film is any one of SiOF, xerogel (porous silicon oxide film), organic SOG (Spin On Glass), polyaryl ether, polyimide, polyparaxylylene, benzocyclobutene, polynaphthalene, and fluororesin. 11. The electronic device according to claim 9 or 10, comprising one.   The electronic device according to claim 9 or 10, wherein the metal wiring is made of an easily oxidizable metal.   The electronic device according to claim 12, wherein the oxidizable metal is Cu, Al—Cu alloy, W, Mo, Ag, or a laminated structure of these and a barrier metal.   The electronic device according to claim 9 or 10, wherein the silicon nitride insulating film has a thickness of 30 nm to 150 nm.   The electronic device according to claim 9 or 10, wherein the silicon nitride insulating film has a thickness of 50 nm to 100 nm.   The electronic device according to claim 9, further comprising an insulating film in contact with the silicon nitride insulating film.

Images