JP3781290B2 - Method for processing laminated insulating film and method for forming wiring structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for processing a laminated insulating film composed of a plurality of different insulating films (in particular, a method of forming a connection hole or a recess using a plasma etching method used in the field of manufacturing semiconductor devices), and a processing method thereof The present invention relates to a method for forming a used wiring structure.
[0002]
[Prior art]
In the field of semiconductor devices, miniaturization and integration have progressed, and the demand for fine processing technology has become increasingly severe. Further, in recent development of ultra large scale integrated circuit (Ultra LSI) devices, various companies are studying with the realization of high speed and low power consumption devices in mind.
[0003]
In particular, in a multilayer wiring structure of a logic device, Cu wiring and a low dielectric constant interlayer film have been adopted in order to realize low resistance and low dielectric constant. As a result, even in the field of process development, demands for the establishment of technologies that can adapt flexibly to more diverse structures and various materials from the pursuit of miniaturization as in the past have become stricter. In the dry etching process, various studies have been repeated aiming at high-precision processing.
[0004]
Usually, as the low dielectric constant interlayer film, a SiOCH-based material (for example, methyl group-containing polysiloxane MSQ) or an organic polymer film is often used. The former is silicon oxide SiO₂A part of O in the methyl group (—CH_Three) Has been developed with the goal of lowering the density of the film itself and consequently lowering the dielectric constant. In other words, the SiOCH-based material has the characteristics that the film density is low, the oxygen contained in the film is small, and elements such as C and H are included.
[0005]
This SiOCH-based low dielectric constant film includes a conventional silicon oxide film (SiO 2₂The film) processing technology can be applied as it is, and a fine hole (connection hole or via hole) or groove (recess or trench) can be formed by dry etching technology using existing equipment. is there.
[0006]
However, Tsuji et al., Proceedings of the 2000 Dry Process Symposium, p. 37, when the amount of oxygen contained in the film is reduced by substitution with a methyl group or the like, the ability to remove excess polymer products from the etched surface is significantly impaired. Etching performance such as the etching rate and etching state of the rate film changes very sensitively to minute changes such as the flow rate and pressure of the reaction gas.
[0007]
Especially for trench and via hole processing used for damascene wiring, so-called micro-trenching (excessive cutting under the mask edge), residue, faceting (shoulder fall around the trench or hole) Such a shape abnormality is a big problem.
[0008]
Since the occurrence of these abnormalities varies depending on the type of film used, it is not easy to find a general solution. Therefore, there is an urgent need to develop a method for obtaining an optimum reaction gas composition according to the film composition and an apparatus for realizing the method.
[0009]
[Course to Invention]
In plasma etching, the reactive gas that has reached the plasma discharge region is subjected to the action of plasma to generate reactive active species, and this reactive active species reacts with the insulating film or the like on the etching surface to generate volatile products. Etching of the insulating film or the like proceeds as volatile products are detached from the etching surface and discharged.
[0010]
On the other hand, on the etched surface, a high molecular compound (polymer) is also generated by plasma polymerization of the reaction gas simultaneously with the generation of the volatile product, and the etching surface is usually a two-layer structure (polymer layer and reaction layer). This is formed according to the amount of incident flux. The polymer layer adheres to the surface and functions to suppress the progress of the etching reaction at that portion. The proper amount of polymeric product will adhere to and protect the sidewalls and photoresist surface. The formation of deep trenches and the control of the sidewall shape are made possible by the protective action of the polymer product. However, an excessive amount of the polymer-like product partially deposits on the etching surface, decelerates ions, prevents energy supply to the reaction layer, and inhibits etching.
[0011]
The present inventor has paid attention to a method for controlling the composition and amount of deposits formed during etching, including polymer products, from an early stage, and always performs good etching while maintaining appropriate etching conditions. We have intensively studied how to control the
[0012]
For example, Japanese Patent Application Laid-Open No. 7-106312 proposes an etching method in which the amount of a product that functions as a sidewall protective film is monitored and the etching temperature is adjusted based on this. The amount monitored here is a physical quantity that varies according to the etching amount actually progressing, such as the emission intensity of the reaction product and the mask spectrum amount, and can be actually measured.
[0013]
In JP-A-8-316209 and JP-A-9-115878, in the etching of an organic polymer insulating film that easily generates a polymer compound, the ratio of fluorine-based chemical species in plasma is increased. A method for preventing excessive deposition of a polymer product or the like by using as a reaction gas at least one of a CF-based gas and a gas capable of generating an oxygen-based chemical species. is suggesting.
[0014]
The inventor has further researched and_FourF₈SiOCH system with SiO2 as reaction gas, SiO_xThe following conclusions have been obtained regarding plasma etching of materials (Mr. et al., Proceedings of the 2000 Dry Process Symposium, p37).
[0015]
The cause of micro-trenching and residues is that the inflow of CF radicals supplied to the etching surface is the ability of oxygen (or nitrogen) in the insulating film to remove carbon by chemical reaction (no ion assistance is required) Chemical reaction) and excess.
[0016]
When the content of oxygen contained in the material is reduced by substitution with a methyl group or the like, the ability to remove excess polymer products from the etched surface is significantly impaired, so the etching rate of the SiOCH-based low dielectric constant material is: It changes very sensitively to minute changes such as the flow rate and pressure of the reaction gas.
[0017]
FIG. 7 shows that the other conditions are not changed so that the removal action of the polymer product by oxygen or the like is kept constant._FourF₈It is the trend graph which investigated the change of the etching rate of planar SiOCH type material, and the change of the thickness of the polymeric product deposited on an etching surface only by changing a flow rate (henceforth, C_FourF₈The graph showing the change in the etching rate of various materials with respect to the change in the flow rate of the reaction gas and the like and the change in the thickness of the polymer product deposited on the etched surface will be referred to as a trend graph of the material).
[0018]
The experiment was performed using a CCP (capacitively coupled plasma) apparatus of a two frequency application type. The experimental conditions are as follows.
Gas flow rate: C_FourF₈/ Ar / N₂= 0 to 12/1000/160 sccm (standard cc per minute),
Reaction chamber pressure: 60 mTorr,
Electric power applied to generate plasma (wafer upper / lower wafer; hereinafter simply referred to as upper / lower): 1200/1500 W,
Plasma density: 1.5 × 10¹¹/ Cm^Three,
Ion Acceleration Voltage (Ion Energy): 2000V,
Substrate temperature: 40 ° C
[0019]
C in FIG._FourF₈In region I where the flow rate is relatively small, C_FourF₈As the flow rate increases, the etching rate increases. This is C_FourF₈F supplied to the etching surface by increasing the flow rate^*This is thought to be due to an increase in the inflow of reactive species such as. In region I, the thickness of the polymer product deposited on the etched surface is small and almost constant.
[0020]
But C_FourF₈When the flow rate reaches 5 sccm, the etching rate takes the maximum value, and C_FourF₈In regions II and III where the flow rate is higher than this, C_FourF₈The etching rate rather decreases with increasing flow rate. At the same time, the thickness of the polymeric product deposited on the etched surface increases in inverse proportion to the decrease in etch rate. This is presumably because the inflow of excess CF radicals forms a polymer deposit on the etched surface, which inhibits etching.
[0021]
That is, the trend graph of FIG. 7 is classified into the following regions I to III based on the surface state of the etched surface.
Region I: A thin polymer deposit layer (polymer) is formed on the surface of the material, and good etching is in progress.
Region II: This is a transition state from region I to region III, and etching proceeds, but removal of the polymer product is unstable and a residue may be generated.
Region III: A thick polymer deposit layer is constantly formed and the etching rate is slow, or only a polymer product is deposited and etching does not proceed.
[0022]
Other SiOCH and SiO_xAs a result of obtaining a trend graph for the materials of the system, the above-mentioned tendency is observed for any material, and the surface state during etching of these materials is classified into the above-mentioned regions I to III. I understood.
[0023]
If the etching rate takes the maximum value and the reaction gas flow rate corresponding to the boundary between the region I and the region II is called a critical point Pc, in order to etch these materials satisfactorily, the reaction gas flow rate is suppressed to Pc or less, It is preferable to keep the surface state in the state of region I.
[0024]
As a method of obtaining the above trend graph,
(A) Actual change in etching rate
(B) Measurement of changes in polymer thickness
(C) Calculation based on actual measurement of radical amount
(D) Calculation from process conditions
It can be obtained by either method. Although the accuracy is as high as the former, a graph with practically sufficient accuracy can be obtained by either method.
[0025]
As shown in FIG. 8, in a processed part having a high aspect ratio or a processed part blocked from plasma by a pattern, a radical inflow amount of a reactive active species or the like supplied to the etching surface is flat and open to the plasma. Relatively less than In actual machining, this point needs to be taken into consideration.
[0026]
For example, in the case of trench (groove or recess) processing, if the central portion of the trench where the amount of radical inflow is the largest is accommodated in region I, the amount of radical inflow is slightly less at the end of the trench and the etching rate is slightly lower. Therefore, a well-shaped trench having a flat bottom or slightly rounded shape can be formed.
[0027]
In FIG. 9A, a Cu wiring 2 is embedded in a silicon oxide film 1 formed on a semiconductor substrate (not shown), a silicon carbide film 3 for preventing copper diffusion, and a SiOCH-based film are formed on the silicon oxide film 1. An interlayer insulating film 8 is laminated, and a resist mask 9 corresponding to the trench pattern is formed on the insulating film.
[0028]
C_FourF₈When a trench pattern is to be formed by removing a part of the SiOCH film 8 by etching using as a reactive gas, since Pc of SiOCH is 5 sccm, a C_FourF₈It can be expected that a good etching process in the region I can be performed if the flow is performed.
[0029]
Therefore, in consideration of the error range, C_FourF₈The flow rate was set to 4 sccm, and etching was performed under the following experimental conditions using the same two-frequency application type CCP apparatus as that obtained in FIG.
Gas flow rate: C_FourF₈/ Ar / N₂= 4/1000/160 sccm,
Reaction chamber pressure: 60 mTorr,
Electric power applied for plasma generation (upper / lower): 1200 / 1500W,
Substrate temperature: 40 ° C
[0030]
As a result, it is possible to obtain a good trench processing shape (trench pattern) 20 having no micro-trenching or residue as shown in FIG. 9B, and the residue 10 is generated as shown in FIG. 9C. There was no. The C used here_FourF₈The flow rate is C used in normal processing._FourF₈It is much smaller than the flow rate.
[0031]
[Problems to be solved by the invention]
As described above, with respect to the single-layer insulating film 8, it is possible to set an appropriate reaction gas flow rate capable of performing good etching processing. However, in an actual semiconductor device, a plurality of films form a laminated structure.
[0032]
For example, when different SiOCH (A) films and SiOCH (B) films are laminated as an interlayer insulating film, in order to continuously and satisfactorily etch these two films, C_FourF₈What value should be used for the flow rate, or in order to etch only the SiOCH (A) film without etching the SiOCH (B) film?_FourF₈A method for responding to the problem of what value should be used for the flow rate has not yet been shown.
[0033]
  The present invention has been made to solve such problems, and its purpose is as follows.SiOCH systemAn object of the present invention is to provide a processing method capable of obtaining a favorable processed shape of a laminated insulating film, and a method of forming a wiring structure using the processing method.
[0034]
[Means for Solving the Problems]
  That is, the present inventionEtching characteristicsDifferent from each otherTwo-layer SiOCHInsulation film(SiO _x C _y H _{z ;} However, x, y, and z are arbitrary numbers. )ButTouchingLaminated insulation film laminatedThe two-layer SiOCH-based insulating filmWhen processing by etching,The two-layer SiOCH systemAbout each insulation film,Relationship of etching rate to reaction gas type and / or supply rateAnd the critical point (reaction gas flow rate at which the etching rate takes the maximum value)Seeking
    In the first method for processing a laminated insulating film, the supply amount of the reactive gas is changed to the two layers of SiOCH.  Set the size below the critical point of the system insulating film,
    In the second method for processing a laminated insulating film, the supply amount of the reaction gas is changed to the two-layer SiOCH.  The intermediate size of the critical point of the system insulating film, and the two layers of Si  The size at which the etching rate of the upper layer of the OCH insulating film is equal to the etching rate of the lower layer  Set to
The present invention relates to a method of processing a laminated insulating film and a method of forming a wiring structure in which wiring is embedded in a connection hole or a recess formed by the processing method.
[0035]
  here,"Etching characteristics“Different insulating films different from each other” refers to insulating films that exhibit different etching rates with respect to the same reactive gas under the same conditions due to differences in composition, manufacturing method, post-treatment, and the like.
[0036]
  According to the present invention, it was obtained in advance,Relationship of etching rate to the kind of reaction gas and / or its supply amountAnd critical pointsSince the etching is performed based onThe supply amount of the reaction gas isSaidTwo-layer SiOCHThe etching rate of the insulating film can be selected appropriately.In sizeCan be optimized and saidTwo-layer SiOCHEven if the insulating films are stacked, it is possible to always obtain a good processed shape, and always to form wiring with good reliability.
[0037]
  The etching rate varies depending on the type, supply amount, pressure, and the like of the reaction gas, and the appropriate supply amount of the reaction gas varies depending on the film type. Such a property requires finding an appropriate supply flow rate of the reaction gas for each film type, but once it is found, the etching rate that differs for each film type depends on the supply amount of the reaction gas. Sex, saidTwo-layer SiOCHIt can be effectively used as means for differentiating between insulating films and appropriately setting the etching selectivity of the laminated insulating film in accordance with the purpose.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
  Of the present inventionMethod for processing first laminated insulating film and method for forming wiring structure for forming connection hole or recess by processing methodThen, saidTwo-layer SiOCHInsulating film lower layer etching rate exceeds upper layer etching rateTo control the etching selectivitythingButEtching each insulating film continuously and satisfactorilyAbovedesirable.
[0040]
In the present invention, it is preferable to form a trench or a via hole by the etching, and it is preferable to adjust the supply amount of the reaction gas and / or the plasma generation power according to the depth of the etching.
[0041]
  In the present invention, the insulating film isIt is formed of two layers of SiOCH-based insulating film, but other layers are in contact with this insulating film.Silicon oxide and / or silicon nitrideInsulation filmSpecifically, SiO_x, SiO_xH_y, SiO_xF_y, Si_xN_y, And SiC_xN_y(However, x, y, and z are arbitrary numbers.) At least one selected from the group consisting ofInsulation filmFormationEven thoughGood. As described above, oxygen in the insulating film has the ability to remove carbon, but nitrogen has the same ability.
[0042]
  Also, as the reactive gasFluoroIt is better to use carbon, specifically C_FourF₈, C_FourF₆, C_FiveF₈, CF_Four, C₂F₆And C_ThreeF₆It is preferable to use at least one selected from the group consisting of
[0043]
Embodiments according to the present invention will be specifically described below with reference to the drawings.
[0044]
Embodiment 1
1A, in the same manner as described above, a silicon carbide film 3 is formed on a silicon oxide film 1 in which a Cu wiring 2 is embedded, and a SiOCH-based SiOCH (B) film 4 and a SiOCH-based film are formed thereon. A state is shown in which a laminated insulating film is formed by laminating the SiOCH (A) film 5 and a resist mask 9 having a shape corresponding to the trench (groove or recess) pattern 20 is formed. The SiOCH (B) film 4 is a film having almost the same composition as the SiOCH film 8 described above, but the SiOCH (A) film 5 is a film having a smaller proportion of methyl groups and a higher oxygen content than the SiOCH film 8. is there.
[0045]
As shown in FIG. 1B, a trench pattern 20 that penetrates the SiOCH film (A) of such a laminated insulating film and reaches the middle portion of the SiOCH (B) film 4 is formed as C._FourF₈Is formed by dry etching using as a reactive gas. In this case, the region I is filled with both the SiOCH (A) film 5 and the SiOCH (B) film 4 to be etched._FourF₈If the flow rate (supply amount) is set, even in a laminated structure, good etching is continuously performed without causing microtrenching, residue, etch stop due to excessive polymer deposits, etc. Is possible.
[0046]
FIG. 1C shows a trend graph of the SiOCH (A) film 5 and the SiOCH (B) film 4. The composition of the SiOCH (B) film 4 shows the same tendency as that of the SiOCH film 8, and Pc is about 5 sccm. Since the SiOCH (A) film 5 is a film having less methyl groups and more oxygen than the SiOCH (B) film 4, its Pc is present at a higher flow rate side of about 8 sccm. This trend graph is obtained by any method, either by actual measurement, by correction calculation from a trend graph actually measured in the case of a flat surface, or by calculation alone.
[0047]
Therefore, C which is Pc of the SiOCH (B) film 4_FourF₈If the flow rate is about 5 sccm or less, it is expected that the two films can be continuously etched with a good surface state in the region I. Therefore, as an example, considering the error range, etc., C_FourF₈The flow rate was set to 4 sccm, which is a lower flow rate than in the case of via hole processing described later, and etching processing was performed under the following experimental conditions using a two-frequency application type CCP (capacitively coupled plasma) device.
Gas flow rate: C_FourF₈/ Ar / N₂= 4/1000/160 sccm,
Reaction chamber pressure: 60 mTorr,
Electric power applied for plasma generation (upper / lower): 1200 / 1500W,
Substrate temperature: 40 ° C
[0048]
As a result, as shown in FIG. 1B, the two stacked layers of the SiOCH (A) film 5 and the SiOCH (B) film 4 are continuously improved to the intermediate thickness of the SiOCH (B) film 4. It was possible to etch, and it was possible to obtain a good trench processing shape without micro-trenching and residue.
[0049]
However, conventionally, the etching conditions for the laminated insulating film as described above do not depend on the trend graph of FIG._FourF₈Since the etching was performed with a larger flow rate (for example, 8 sccm), the etching state of one of the insulating films was deteriorated.
[0050]
FIG. 2 shows a state in which a Cu wiring 13 is embedded in the trench pattern portion 20 formed by the above etching process to form a damascene structure. As the order of formation, first, the barrier metal layer 11 made of tantalum nitride or titanium nitride is formed on the trench pattern surface by a CVD (Chemical Vapor Deposition) method or a PVD (Physical Vapor Deposition) method. This is to prevent the diffusion of copper to the outside.
[0051]
Next, a Cu plating seed layer 12 is laminated on the barrier metal layer 11 by the CVD method or the PVD method.
[0052]
Finally, the Cu wiring 13 is embedded in the trench pattern portion 20 using the Cu plating seed layer 12 as a base by a CVD method or an electrolytic plating method. In each of the following embodiments, the wiring structure can be formed in the same manner as described above.
[0053]
  Embodiment 2
  As shown in FIG. 3A, a resist mask 9 corresponding to the via hole (through hole or connection hole) 30 is formed on the same laminated insulating film as in the first embodiment, and the etching process is performed to form FIG. ), A via hole 30 that reaches the silicon carbide film 3 is formed through the laminated insulating film made of the SiOCH (A) film 5 and the SiOCH (B) film 4.
[0054]
The following two points are different from the case of the first embodiment. First, when the via hole 30 is formed, the loss of CF radicals disappearing in the hole wall in the hole having a high aspect ratio is larger than that in the case of forming the trench, and the amount reaches the etching surface at the bottom of the hole. The amount of radicals is reduced. A trend graph that takes this into account is necessary.
[0055]
The trend graph in the case of hole formation is obtained by any method, whether it is obtained by actual measurement, obtained by correction calculation from the actually measured trend graph in the case of a flat surface, or obtained only by calculation. When calculating by calculation, it is necessary to take into account the transport of radical species in the hole.
[0056]
The second point is that it is necessary to find a condition in which the SiOCH (A) film 5 and the SiOCH (B) film 4 are both etched through, but the silicon carbide film 3 is not etched. Therefore, a trend graph of the silicon carbide film 3 is also required.
[0057]
FIG. 3C shows a trend graph of each insulating film when holes are formed. Pc of the SiOCH (B) film 4 in the case of hole formation is about 7 sccm, shifted to a higher flow rate side than in the case of planar or trench formation (about 5 sccm). Pc in the case of forming a hole in the SiOCH (A) film 5 with few methyl groups is about 10 sccm on the higher flow rate side. The trend graph of the silicon carbide film 3 shows C in the range of 5.5 to 12 sccm._FourF₈The etching rate decreases with increasing flow rate, and the etching rate at a flow rate of about 7 sccm and higher is sufficiently small.
[0058]
Therefore, C_FourF₈If the flow rate is set to about 7 sccm, both the two films can be continuously etched in a good surface state in the region I, and damage to the silicon carbide film 3 can be minimized.
[0059]
Therefore, as an example, considering the error range, etc., C_FourF₈The flow rate was set to 6.5 sccm, and etching was performed under the following experimental conditions using the above-described dual frequency application type CCP (capacitively coupled plasma) apparatus.
Gas flow rate: C_FourF₈/ Ar / N₂= 6.5 / 1000/160 sccm,
Reaction chamber pressure: 60 mTorr,
Electric power applied for plasma generation (upper / lower): 1200 / 1500W,
Substrate temperature: 40 ° C
[0060]
As a result, as shown in FIG. 3B, the stacked SiOCH (A) film 5 and SiOCH (B) film 4 are continuously and satisfactorily etched, and there is no etch stop. A via hole 30 having a hole shape can be formed, and damage to the silicon carbide film 3 can be minimized (FIG. 3B).
[0061]
Embodiment 3
When etching is performed as shown in FIGS. 4A and 4B using an etching apparatus having poor uniformity in the wafer surface, there is a difference in the etching rate between a plurality of via hole 30 forming portions on the wafer surface. Produce. As a result, the time for the etching surface to reach the interface between the SiOCH (A) film 5 and the SiOCH (B) film 4 varies for each via hole 30 formation location, and the etching surface quickly reaches the interface from the hole where the etching surface has reached the SiOCH (B). Etching of film 4 begins.
[0062]
In such a case, when the etching rate of the lower layer (SiOCH (B) film 4) is set larger than the etching rate of the upper layer (SiOCH (A) film 5) as in the second embodiment, the etching surface There is a concern that an etching process with poor uniformity in the wafer surface in which only a part of the holes are dug deeply with a difference in depth will be caused.
[0063]
When there is such a concern, the etching rate of the SiOCH (A) film 5 and the SiOCH (B) film 4 is set to be equal to each other._FourF₈By setting the flow rate, an etching process with improved uniformity within the wafer surface can be achieved.
[0064]
From the trend graph of FIG._FourF₈The flow rate is determined to be about 8.8 sccm. At this flow rate, the etching surface of the SiOCH (B) film 4 takes the surface state of the region II, but a residue is relatively unlikely to occur in a fine hole, so this is not a problem.
[0065]
In the present embodiment, as an example, C_FourF₈The flow rate was set to 8.5 sccm, and etching was performed under the following experimental conditions using the above-described dual frequency application type CCP (capacitively coupled plasma) apparatus.
Gas flow rate: C_FourF₈/ Ar / N₂= 8.5 / 1000/160 sccm,
Reaction chamber pressure: 60 mTorr,
Electric power applied for plasma generation (upper / lower): 1200 / 1500W,
Substrate temperature: 40 ° C
[0066]
  FIG. 5A shows a stacked insulating film in which a silicon carbide film 3, a SiOCH (D) film 6, and a SiOCH (C) film 7 are stacked on a silicon oxide film 1 in which a Cu wiring 2 is embedded. A state in which a resist mask 9 having a shape corresponding to the trench pattern 20 is formed is shown. Here, as shown in FIG. 5B, the trench pattern 20 is formed by etching only the SiOCH (C) film 7 without etching the SiOCH (D) film 6 of such a laminated insulating film.
[0067]
In such a case, C_FourF₈When the flow rate is set to an appropriate value, the SiOCH (C) film 7 and the SiOCH (D) are formed so that the upper SiOCH (C) film 7 is in the region I and the lower SiOCH (D) film 6 is in the region III. ) The material of the film 6 is selected. For this purpose, it is desirable to laminate two materials that differ greatly in composition.
[0068]
  As an example, here, the SiOCH (C) film 7 includesIn order to highlight the difference from the SiOCH (D) film 6The H-containing polysiloxane HSQ not containing carbon is used, and the SiOCH (D) film 6 is a film similar to the SiOCH film 8.
[0069]
FIG. 5C shows both trend graphs. Since the SiOCH (C) film (H-containing polysiloxane HSQ) 7 does not contain carbon, a large C_FourF₈The region I extends to the flow rate region, and Pc is about 10 sccm, which is far from the Pc value (about 6.5 sccm) of the SiOCH (D) film 6. C_FourF₈If the flow rate is set to 10 sccm, for example, the SiOCH (C) film 7 belongs to the region I and the SiOCH (D) film 6 belongs to the region III._FourF₈Even if the supply of is not stopped, only the upper SiOCH (C) film 7 can be etched by setting the etching selectivity, and the lower SiOCH (D) film 6 can be automatically stopped.
[0070]
In the present embodiment, as an example, C_FourF₈The flow rate was set to 10 sccm, and etching was performed under the following experimental conditions using the above-described dual frequency application type CCP (capacitively coupled plasma) apparatus.
Gas flow rate: C_FourF₈/ Ar / N₂= 10/1000/160 sccm,
Reaction chamber pressure: 60 mTorr,
Electric power applied for plasma generation (upper / lower): 1200 / 1500W,
Substrate temperature: 40 ° C
[0071]
When the etching process proceeds and the etching surface reaches the interface between the SiOCH (C) film 7 and the SiOCH (D) film 6, a thick polymer deposit (thickness of about 6 nm) is formed on the SiOCH (D) film 6. ) Was formed and etching was stopped. Thereby, as shown in FIG. 5B, a trench pattern having a uniform trench depth in the wafer surface could be formed.
[0072]
  The composition of insulating films other than the above-described SiOCH-based films is variable. FIG. 6 shows etching rates when forming trench patterns for various insulating films formed by coating or CVD (chemical vapor deposition) as in the first embodiment. By selectively using these trend graphs for each film quality, various insulating films can be etched well.
[0073]
Note that, as a change in characteristics depending on the film quality, Pc tends to appear on the lower flow rate side as the oxygen content in the film is smaller or the carbon content is larger. Further, the magnitude of the etching rate on the lower flow rate side than Pc tends to increase as the film density decreases.
[0074]
  As described above, by the method according to the present invention, the process of processing the SiOCH-based laminated insulating film without etch stop and residue can be performed.,It can be provided regardless of the film quality. Therefore, various low-k (low dielectric constant) materials can be processed, and Cu embedded wiring using dual damascene can be formed efficiently and satisfactorily, improving the reliability and yield of high-speed and low-power consumption devices. Can contribute.
[0075]
Although the present invention has been described based on the embodiments, the present invention is not limited to these examples. The reaction gas supply conditions, the material of each film, the apparatus, and the like depart from the gist of the present invention. It is possible to change appropriately within the range not to be.
[0076]
【The invention's effect】
  According to the present invention, it was obtained in advanceThe aboveRelationship of etching rate to reaction gas type and / or supply rateAnd the critical pointOn the basis of theSaidetchingI doSoThe supply amount of the reaction gas is set to the two-layer SiOCH system.Insulating filmSaidEach etching rate can be selected appropriatelyIn sizeCan be optimized,The two-layer SiOCH systemEven if insulating films are stacked, a good processed shape can always be obtained, andWellIt is possible to always form the wiring in the formed connection hole or recess with good and reliability.
[0077]
  SaidEtching rate isSaidIt varies depending on the type of reaction gas, supply amount, pressure, etc.SaidThe appropriate supply amount of the reaction gas varies depending on the membrane type. Such a propertySaidIt is necessary to find the appropriate supply flow rate of the reaction gas for each film type, but once it is found, it differs for each film type.SaidEtching rateSaidThe dependence on the supply amount of the reaction gas isTwo-layer SiOCHDifferentiate between insulating films,SaidIt can be effectively used as a means for appropriately setting the etching selectivity of the laminated insulating film in accordance with the purpose.
[0078]
  By this invention, there is no etch stop and residueSiOCH systemMultilayer insulation film processing process,It can be provided regardless of the film quality. Therefore, various low-k (low relative dielectric constant) materials can be processed, and wiring such as Cu embedded wiring using dual damascene can be formed efficiently and satisfactorily. This can contribute to yield improvement.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention.1The main part schematic sectional drawing and schematic perspective view (a), (b) which show the example which formed the trench pattern in the SiOCH type laminated insulation film, and C_FourF₈It is a graph (trend graph) (c) which shows the change of the etching rate of the SiOCH type material by the change of a flow rate.
FIG. 2 is a schematic cross-sectional view of an essential part showing an example in which a Cu embedded wiring is applied to a trench pattern.
FIG. 3 shows an embodiment of the present invention.2The main part schematic sectional drawing and schematic perspective view (a), (b) which show the example which formed the via hole in the SiOCH type | system | group laminated insulating film, and C_FourF₈It is a graph (trend graph) (c) which shows the change of the etching rate of the SiOCH type material by the change of a flow rate.
FIG. 4 is an embodiment of the present invention.3The main part schematic sectional drawing and schematic perspective view (a), (b) which show the example which formed the via hole in the SiOCH type | system | group laminated insulating film, and C_FourF₈It is a graph (trend graph) (c) which shows the change of the etching rate of the SiOCH type material by the change of a flow rate.
FIG. 5 shows an embodiment of the present invention.4The main part schematic sectional drawing and schematic perspective view (a), (b) which show the example which formed the trench pattern in the SiOCH type laminated insulation film, and C_FourF₈It is a graph (trend graph) (c) which shows the change of the etching rate of the SiOCH type material by the change of a flow rate.
FIG. 6 is a graph (trend graph) showing changes in etching rates of various insulating film materials.
FIG. 7 C_FourF₈It is a graph which shows the change of the etching rate of a SiOCH type material by the change of a flow rate, and the change of the thickness of the polymeric product deposited on an etching surface.
FIG. 8 is a graph showing changes in the flow rate of radicals flowing into the etching surface due to changes in aspect ratio.
FIG. 9 shows C set based on the graph of FIG._FourF₈FIG. 6 is a schematic cross-sectional view of a main part and schematic perspective views (a), (b), and (c) showing an example of etching a single layer SiOCH-based film into a trench pattern at a flow rate.

Claims (14)

SiOCH-based insulating film of etching characteristics different from each other two layers (SiO _x C _y H _z; however, x, y, z are any number.) Was in the processing method of the stacked insulating film are laminated is in contact When the two-layered SiOCH-based insulating film is processed by etching, the relationship between the type of reaction gas and / or the etching rate with respect to the supply amount of each of the two-layered SiOCH-based insulating films and the critical point (etching) A reaction gas flow rate at which the speed reaches a maximum value), and a supply amount of the reaction gas is set to a value smaller than a smaller one of the critical points of the two-layer SiOCH-based insulation film. Processing method. The lower etch rate of the SiOCH-based insulating film having a two-layer controls the etching selection ratio to be greater than the etching rate of the upper layer, the processing method of the stacked insulating film according to claim 1. This is a method of processing a laminated insulating film in which two layers of SiOCH-based insulating films (SiO _x C _y H _z ; where x, y, z are arbitrary numbers) having different etching characteristics are in contact with each other . When the two-layered SiOCH-based insulating film is processed by etching, the relationship between the type of reaction gas and / or the etching rate with respect to the supply amount of each of the two-layered SiOCH-based insulating films and the critical point (etching) A reaction gas flow rate at which the speed reaches a maximum value), and the supply amount of the reaction gas is an intermediate size between the critical points of the two SiOCH-based insulating films and the two layers. A method for processing a laminated insulating film, wherein the upper layer etching rate and the lower layer etching rate are set to be equal to each other . Forming a trench or via hole by the etching processing method of the stacked insulating film according to claim 1 or 3. The method for processing a laminated insulating film according to claim 4 , wherein a supply amount of the reaction gas and / or a plasma generation power is adjusted according to the etching depth. Using the fluoro carbon as the reaction gas, the processing method of the stacked insulating film according to claim 1 or 3. Using the _{C 4 F 8, C 4 F} 6, C 5 F 8, CF 4, C 2 F 6 and C ₃ at least one selected from the group consisting of F ₆ as the reaction gas, according to claim 6 For processing the laminated insulating film. SiOCH-based insulating film of etching characteristics different from each other two layers _{(SiO x C y H z;} . However, x, y, z are set to an arbitrary number) processed by etching a laminated insulating film is laminated in contact further method of forming a wiring structure buried wiring formed connection hole or recess by etching, the etching rate for each, for the type and / or the supply amount of the reaction gas SiOCH-based insulating film of the second layer And a critical point (reaction gas flow rate at which the etching rate takes a maximum value) is obtained, and the supply amount of the reaction gas having a magnitude smaller than the smaller of the critical points of the two-layer SiOCH insulating film is obtained. A method of forming a wiring structure , wherein the etching is performed in 9. The method for forming a wiring structure according to claim 8 , wherein the etching selectivity is controlled so that the etching rate of the lower layer of the two-layer SiOCH insulating film exceeds the etching rate of the upper layer. Etching is performed on a laminated insulating film in which two layers of SiOCH-based insulating films (SiO _x C _y H _z ; where x, y, z are arbitrary numbers) having different etching characteristics are in contact with each other . further a wiring structure forming method for embedding wiring connection hole or recess formed by the etching, each of the SiOCH-based insulating film of the second layer, the etching for the type and / or amount of reaction gas supplied The relationship between the velocity and the critical point (reaction gas flow rate at which the etching rate has the maximum value) is obtained, and the size is intermediate between the critical points of the two-layer SiOCH-based insulating film, and the 2 wherein at a feed rate of the reaction gas layer of the etch rate and lower etch rate of the composed magnitude equivalent SiOCH-based insulating film layer etch Performing grayed, method for forming a wiring structure. The method for forming a wiring structure according to claim 8 or 10 , wherein a trench or a via hole is formed by the etching. The method for forming a wiring structure according to claim 11 , wherein a supply amount of the reaction gas and / or a plasma generation power is adjusted according to the etching depth. Using the fluoro carbon as the reaction gas, the method of forming the wiring structure according to claim 8 or 10. Using the _{C 4 F 8, C 4 F} 6, C 5 F 8, CF 4, C 2 F 6 and C ₃ at least one selected from the group consisting of F ₆ as the reaction gas, according to claim 13 Method for forming a wiring structure.

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