JP3780657B2 - Etching method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an etching method, and more particularly to an etching method for etching an etching target layer including a tungsten layer or a tungsten silicide layer.
[0002]
[Prior art]
In recent years, tungsten and tungsten silicide have been widely used in semiconductor devices. Tungsten silicide is used as a kind of silicide to be stacked on a polycrystalline (poly) silicon layer to form a polycide electrode (wiring), or used alone for local wiring or the like. Tungsten can be selectively grown on a conductive region by chemical vapor deposition (CVD) or blanket grown on the entire surface of the base, and is widely used as a conductive plug or a lower layer wiring. Note that tungsten can also be sputtered. The tungsten silicide layer is generally formed by CVD or by sputtering using tungsten silicide as a target.
[0003]
Many of the fine MOS transistors in a highly integrated semiconductor integrated circuit have a polycide structure as a gate electrode. The lower silicon layer ensures the threshold characteristics of the MOS transistor, and the upper silicide layer reduces the resistance value of the gate electrode (wiring). The characteristics of MOS transistors, particularly the operation speed, are greatly affected by the gate length. In order to produce a transistor having a narrow gate length with high accuracy, a technique for etching a polycide stack with high accuracy is desired.
[0004]
Hereinafter, WSi is used as the gate electrode.₂A patterning process in the case of using / polySi polycide stack will be described. WSi₂In general, etching is performed with a mixed gas of chlorine-containing gas and oxygen gas. For example, Cl containing chlorine₂Is used. The addition of oxygen gas can be achieved by using WOCl with a relatively high vapor pressure._FourIs performed to facilitate etching. In addition, in polySi etching, SiO₂In many cases, oxygen gas is added to improve the selectivity with respect to the gate oxide film.
[0005]
FIG. 5 shows Cl according to such a conventional technique.₂/ O₂WSi using plasma₂2 shows etching of a / polySi stack. On top of the Si substrate 101, a thin SiO film that becomes a gate oxide film₂A layer 102 is formed, on which a poly Si layer 103, WSi₂Layer 104 is laminated. WSi₂A resist mask 107 is formed on the layer 104. The resist mask 107 has a pattern that matches the gate shape. As the LSI wiring becomes finer, the aspect ratio (height / width) of the space portion S between the wirings increases.
[0006]
In the upper space in the figure, Cl₂/ O₂Supply gas, for example, supply 2.45 GHz microwave and Cl₂/ O₂Plasma 108 is generated. Further, a high frequency (RF) of 13.56 MHz, for example, is applied to the wafer susceptor on which the silicon substrate 101 is placed.
[0007]
Etching conditions are, for example, pressure = 2 mTorr, microwave power = 1400 W, RF power = 40 W, etching gas flow rate is Cl₂/ O₂= 25/9 sccm.
[0008]
According to the shape of the resist 107, first, the underlying WSi₂Layer 104 is etched substantially vertically. In the wide space where a large space is exposed outside the resist mask 107 before long, WSi₂Etching of layer 104 ends. Even at this time, in the region where the space between the patterns is narrow, the etching rate is reduced due to the microloading effect.₂Layer etching does not end.
[0009]
When etching is continued, WSi is formed in a narrow space.₂Etching of the layer 104 proceeds further, and in a wide space portion, WSi₂Etching of the polySi layer 103 under the layer proceeds. Eventually, even in narrow spaces, WSi₂The etching of the layer 104 is finished, and the underlying polySi layer 103 is etched. When the polySi layer 103 is etched even in a narrow space portion following a wide space portion, a shape as shown in the figure is obtained.
[0010]
At this time, WSi₂The side wall facing the narrow space portion of the layer 104 becomes reversely tapered as shown in the figure. This is because excess oxygen and WSi in the etching and over-etching of the Si layer₂Reacting with the side walls of the layer, WOCl_xWSi to form and evaporate₂It is believed that this is because the layer sidewalls are etched.
[0011]
Thus, WSi₂When the side wall of the layer is in a reverse taper shape, impurities are implanted directly under the gate electrode in the subsequent ion implantation process, and the effective gate length changes. In addition, since the shape of the sidewall spacer is different from that when the gate sidewall is vertical, there is a possibility that the gain and life of the MOS transistor do not reach desired values.
[0012]
In order to prevent the occurrence of a reverse taper shape, it is conceivable to increase the anisotropy of etching by increasing ion energy. However, if the ion energy is increased, the etching selectivity of the resist is lowered, so that the resist film thickness must be increased. If the resist film is thickened, the resolution of photolithography is impaired, and the processing accuracy is lowered.
[0013]
JP-A-1-239932 discloses chlorine gas (Cl₂) And nitrogen gas (N₂And a method of etching a stacked layer of a tungsten silicide layer and a polysilicon layer using an etching gas mixed with). It has been reported that when this etching gas is used, the tungsten silicide layer is etched in a forward tapered shape, and the polysilicon layer is etched vertically (page 3, lower right column to page 4, upper right column).
[0014]
The same publication also discloses that when etching the lower polysilicon layer, chlorine gas, nitrogen gas, and SiCl are used to etch the remaining film following the main etching._FourA technique of over-etching using a mixed gas with a gas is also described (page 4, upper right column to page 4, lower right column).
[0015]
USP 5,219,485 discloses various etching processes for polycide electrodes. As one of them, a stack of a tungsten silicide layer and a polysilicon layer is made of BCl._Three/ Cl₂/ NF_ThreeA method of etching with a mixed gas of is proposed. NF_ThreeWSi₂When etching the layer, the W fluoride with high vapor pressure (WF₆) And used to increase the etching rate (FIG. 15, column 9, lines 1-19).
[0016]
[Problems to be solved by the invention]
As described above, the laminated structure of the tungsten silicide layer and the polysilicon layer is made Cl.₂/ O₂When etching with gas, the tungsten silicide layer is etched in a reverse taper shape. Cl₂/ O₂Instead of Cl₂/ N₂WSi₂Although it is possible to prevent the layer from being reversely tapered, it becomes conversely a tapered shape. In the etching of a fine pattern, in order to improve the etching pattern accuracy, it is desirable that the sidewall can be formed substantially vertically.
[0017]
An object of the present invention is to provide an anisotropic etching method capable of etching a tungsten or tungsten silicide layer substantially vertically.
[0018]
Another object of the present invention is to provide an anisotropic etching method capable of etching a stack of a tungsten or tungsten silicide layer and a polysilicon layer substantially vertically.
[0019]
[Means for Solving the Problems]
  According to one aspect of the present invention, an isolation pattern sandwiched between a wide space portion and a narrow space portion is disposed on an etching target layer formed on a base surface and formed of tungsten or tungsten silicide. A step of forming an etching mask including a plurality of dense patterns, and the etching target layer is formed through the etching mask.Contains gas containing chlorine and oxygen gasWith the first kind of gasetchingAnd a first surface exposing the base surface of the wide space portion.etchingProcess and firstetchingFollowing the step, a second etching gas is used to etch the remaining etching target layer with a second type of etching gas containing chlorine and nitrogen.etchingAnd an etching method including the steps.
[0020]
Tungsten or tungsten silicide layers are Cl₂/ O₂It is possible to perform anisotropic etching almost vertically with a first type gas such as.
[0021]
When a region with a high pattern density having a narrow space part and a region with a low pattern density having a wide space part coexist on the same substrate, even if etching is finished in the low pattern density region due to the microloading effect, the pattern density Etching is not yet finished in the high region. To complete the etching in the high pattern density region, a second type etching gas different from the first type gas is used, and the remaining tungsten or tungsten silicide layer is over-etched to form tungsten or tungsten silicide. The entire layer can be anisotropically etched almost vertically.
[0022]
When a silicon layer is present under the tungsten or tungsten silicide layer, it is desirable that the silicon layer is also etched vertically. By selecting the second type of gas, the silicon layer can also be etched almost vertically.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
As described above, Japanese Patent Application Laid-Open No. 1-239932 proposes a method for dry etching a gate laminated film having a polycide structure using an etching gas containing a chlorine-based gas containing chlorine atoms in the molecule and a nitrogen gas. is doing. However, according to this method, the silicide film is etched in a forward tapered shape. The polysilicon layer under the silicide layer necessarily has a width wider than the resist pattern. Therefore, this method has a limit when a MOS transistor or the like having an extremely short gate length is produced. In addition, if the forward taper shape cannot be accurately controlled, the pattern accuracy of the etching process is also lowered.
[0024]
WSi₂Judging from the RIE lag data, a pattern in which the aspect ratio (height / width) of the space portion of the line-and-space pattern exceeds 1 can be defined as a dense pattern (high-density pattern). In an actual semiconductor device, a wiring pattern or the like in a memory cell region can be defined as a high-density pattern or a dense wiring region.
[0025]
When the etching is finished, the upper end of the cross-sectional shape of the wiring coincides with the lower end of the resist mask, and when there is no side-etched portion from the end of the resist mask, the etching is a taper etching. Can be defined. According to this definition, the anisotropic etching for forming the wiring having the vertical side wall is also a taper etching.
[0026]
The forward taper refers to an etched shape in which the elevation angle viewed from the base surface is 0 ° to 90 ° in the cross-sectional shape of the etched wiring layer.
[0027]
Further, in the cross-sectional shape of the etched wiring layer, when the elevation angle viewed from the substrate side is in a region exceeding 90 ° to 180 °, such a taper can be defined as an inverse taper. As a configuration of the semiconductor device, it is preferable that the etching is a taper etching and a forward tapered shape is formed. Even if a forward tapered cross-sectional shape can be created, it is difficult to achieve high pattern accuracy in the case where erosion occurs at the mask edge (non-taper etching).
[0028]
From the point when etching of the target layer is completed in the low-density pattern region having a wide space portion outside the pattern, the target layer is completely formed in the high-density pattern region having only a narrow space portion between the patterns. Etching until removal is defined as over-etching.
[0029]
The inventor₂/ N₂The properties of anisotropic etching using as an etching gas were investigated in more detail.
[0030]
FIG. 3 is a cross-sectional view schematically showing the configuration of an electron cyclotron resonance (ECR) plasma etcher used in this preliminary experiment and also used in the examples of the present invention. The etcher housing 20 is made of metal and defines a waveguide 26 and reaction chamber 21 therein.
[0031]
At the boundary between the waveguide 26 and the reaction chamber 21, a transmission window 27 that allows microwaves such as quartz glass to pass therethrough is airtightly provided. For example, a microwave of 2.45 GHz is supplied from above the waveguide 26 to guide the microwave into the reaction chamber 21. The reaction chamber 21 has a two-stage structure having a narrow portion and a wide portion, and electromagnets 24 and 25 are provided on the outer sides thereof. The ECR condition is established by introducing a microwave into the magnetic field generated by these electromagnets 24 and 25. A gas supply hole (not shown) and an exhaust hole 33 are connected to the reaction chamber 21.
[0032]
A wafer susceptor 28 that is airtightly coupled to the housing and serves as a lower electrode is provided at the lower part of the reaction chamber. The wafer susceptor 28 is connected to a high frequency power supply 29 of 13.56 MHz, for example. A silicon wafer 31 is placed on the wafer susceptor 28, ECR plasma is generated in the reaction chamber 21, and an etching experiment is performed.
[0033]
FIG. 4A schematically shows one configuration of a sample used in the experiment. On the Si substrate 40, WSi₂A layer 41 is formed, and a resist pattern 42 is formed thereon. Using this resist pattern 42 as an etching mask, Cl₂/ N₂ECR plasma etching was performed using as an etching gas. Etching conditions are as follows.
[0034]
Pressure = 2 mTorr,
Microwave power = 1400W
RF (13.56 MHz) power = 40 W,
Cl₂+ N₂= 30-100 sccm
Under such conditions, WSi₂When layer 41 is etched, as shown in FIG.₂Layer 41 was etched in a forward taper. A taper angle between the forward tapered side wall and the Si substrate 40 is defined as θ. Total gas flow rate of etching gas and N in the etching gas₂WSi by changing the flow rate ratio (%)₂Layer 41 was etched. The result is shown in FIG.
[0035]
As is apparent from the graph of FIG.₂As the flow rate is increased, the forward taper angle gradually decreases. The taper angle θ shows a continuous change even when the total gas flow rate changes. Such a change in the forward taper angle is caused by the progress of etching and the nitride of W (WN_x) And Si nitride is WSi₂This is considered to be because it adheres to the side wall of the layer 41. The result of FIG.₂It is considered that increasing the flow rate ratio increases the amount of nitride deposited on the sidewall protective film.
[0036]
The inventor further conducted an experiment in which the pattern density of the resist pattern was changed.
[0037]
FIG. 4C schematically shows the shape of the sample used in the experiment. Similar to the sample of FIG. 4A, WSi is formed on the Si substrate 40.₂A layer 41 was deposited, and a resist pattern 42 was formed thereon. In the resist pattern 42, a pattern having a narrow space (a left side in the figure) in which patterns having a line width of 0.5 μm are arranged in parallel at intervals of 0.5 μm and a pattern having a width of 0.5 μm are arranged in a wide space. It has an isolated wiring portion (right side in the figure). Etching conditions are the same as in the above experiment
Pressure = 2 mTorr,
Microwave power = 1400W
RF power = 40W
Cl₂/ N₂= 27 / 3sccm
It was. WSi in open space₂The etching depth of the layer was set to 250 nm.
[0038]
WSi under this condition₂When the layer 41 was etched, a forward taper shape with an elevation angle of 36 ° was formed in the isolated wiring pattern, and an etching shape having a forward taper shape with an elevation angle of 53.5 ° was obtained in the dense wiring pattern. That is, it was found that the taper angle of the forward taper shape depends on the pattern density. The taper angle is expected to increase as the pattern density increases.
[0039]
Interpreting this experimental result, it is estimated that a large amount of nitride side wall protective film is deposited on the side wall of the isolated wiring pattern, and a little side wall protective film is deposited on the side wall of the dense wiring pattern arranged at a narrow interval. . In the case of a dense wiring pattern arranged at a narrow interval, even if a sidewall protective film is deposited, the amount thereof is smaller than that of a wide open space, and it is estimated that the etched sidewall approaches vertical.
[0040]
  In the above experiment, Cl as a gas containing chlorine.₂Was used, but Cl as a gas containing chlorine₂, HCl, BCl₃,SiCl ₄ ,S ₂ Cl ₄ , CCl₄Or a combination of these could be used. Similar results may be obtained using tungsten instead of tungsten silicide.
[0041]
Tungsten or tungsten silicide layer is Cl₂When etching is performed with a mixed gas of chlorine-containing gas and nitrogen gas such as the above, it will be unavoidable that the cross-sectional shape of the etched tungsten or tungsten silicide layer becomes a forward tapered shape.
[0042]
Cl₂/ O₂If an etching gas such as, for example, is used, etching can be performed in a shape in which the sidewall of the tungsten or tungsten silicide layer is vertical. However, if this etching is continued even after the etching in the low-density pattern region is completed until the etching in the high-density pattern region is completed, the cross-sectional shape of the tungsten or tungsten silicide layer is inversely tapered in the high-density pattern region. As described in the prior art.
[0043]
The present inventor uses a main etching process using an etching gas capable of obtaining a vertical cross-sectional shape in anisotropic etching of a tungsten or tungsten silicide layer, and an etching gas containing a mixed gas of chlorine-containing gas and nitrogen gas. It is proposed to use an over-etching process.
[0044]
1 and 2 are cross-sectional views of a semiconductor substrate showing the main steps of an etching method according to an embodiment of the present invention.
[0045]
As shown in FIG. 1A, a thin silicon oxide film 2 such as a gate oxide film is formed on the surface of a Si substrate 1, and a stacked layer of a polycrystalline Si layer 3 and a tungsten silicide layer 4 is deposited thereon. A photoresist pattern 7 is formed on the tungsten silicide layer 4. The photoresist pattern includes a dense pattern region NS in which patterns are densely packed at a narrow interval and a low density pattern region WS in which wide space portions exist on both sides of the pattern.
[0046]
First, as shown in FIG.₂/ O₂Cl using gas₂/ O₂A main etching process of the tungsten silicide layer 4 is performed by the plasma 8. This main etching process is an etching process until the tungsten silicide layer 4 is completely etched in the low density pattern region WS.
[0047]
At the end of this step, wide openings 5 in which the surface of the polycrystalline Si layer 3 is exposed are formed in the low density pattern region WS. In the high-density pattern region NS, the etching rate is reduced due to the microloading effect, so that the groove 6 that has advanced to the middle part of the thickness of the tungsten silicide layer 4 is formed.
[0048]
As shown in FIG. 2C, an overetching process for completely etching the tungsten silicide layer 4 in the high-density pattern region NS is performed. In this over-etching process, the etching gas is Cl.₂/ N₂Convert to
[0049]
As can be seen from the preliminary experiment described above, a large amount of the nitride protective film 11 is deposited on the side wall of the tungsten silicide layer 4 in the low density pattern region. In contrast, a small amount of the nitride protective film 12 is deposited in the high-density pattern region NS. For this reason, in the low density pattern region WS, a sufficient amount of the protective film 11 is deposited on the sidewall of the tungsten silicide layer 4, and the tungsten silicide layer 4 is rarely etched from the lateral direction. For this reason, the vertical shape of the side wall is maintained, and the dimensional accuracy is maintained.
[0050]
In the high-density pattern region NS, the nitride protective film 12 deposited on the sidewall of the tungsten silicide layer 4 is small, and the etching of the tungsten silicide layer 4 is efficiently continued. The side wall has a slight forward taper shape or a substantially vertical shape. The polycrystalline Si layer 3 under the tungsten silicide layer 4 is etched in the low density pattern region until the overetching is completed in the high density pattern region NS. This Cl₂/ N₂Etching the silicon with will form vertical sidewalls. That is, in the over-etching process, an inversely tapered shape does not occur in the low density pattern region, and a substantially vertical side wall is obtained, and a vertical side wall is obtained in the high density pattern region.
[0051]
FIG. 2D shows an anisotropic etching process of the polycrystalline Si layer. After the over-etching of the tungsten silicide layer 4 is completed, the gas is switched again to perform the vertical etching of the polycrystalline Si layer 3. Etching gas is, for example, Cl₂/ O₂ECR plasma etching is performed. Cl₂/ O₂Plasma 10 is SiO₂It has a property of maintaining a high selectivity with respect to the layer 2 and etching the Si layer 3 vertically.
[0052]
Note that Cl shown in FIG.₂/ N₂The Si layer can also be etched vertically by plasma etching. Therefore Cl₂/ N₂Plasma etching of Cl₂/ O₂Switch to plasma etching of SiO underlayer of Si layer₂It may be when the layer is exposed. WSi₂From the end of over-etching of the layer to SiO₂It may be until the layer is exposed. Cl₂/ N₂If the etching ratio of the gas can be selected with the base, Cl₂/ N₂All of the Si layer may be etched.
[0053]
In addition, since the protective film remains on the sidewall of the tungsten silicide layer 4 during the vertical etching of the Si layer, it is possible to prevent the tungsten silicide layer from being etched to form a reverse taper shape.
[0054]
By such a process, the polycide laminated structure composed of the laminated tungsten silicide layer and silicon layer can be etched almost vertically.
[0055]
Note that Cl is used for etching the tungsten silicide layer.₂/ O₂However, other etching gas capable of vertically etching tungsten or tungsten silicide may be used.
[0056]
WSi₂Although the case of etching the polycide layer of the layer / silicon layer has been described, a similar process could be used for etching a tungsten silicide layer or a single layer of a tungsten layer. In the overetching process of the tungsten or tungsten silicide layer, it is important to use an etching gas containing a mixed gas of chlorine and nitrogen.
[0057]
A gas containing chlorine and nitrogen gas (for example, Cl₂/ N₂), It is possible to etch the silicon layer vertically. Accordingly, even after the etching of the tungsten or tungsten silicide layer is completed, the etching may be continued with a mixed gas containing a gas containing chlorine and a nitrogen gas to etch the silicon layer under the tungsten or tungsten silicide layer.
[0058]
In addition to the polycide structure etching, a single layer of tungsten or a tungsten silicide layer may be etched as described above. In this case, naturally, the etching process of only the silicon layer can be omitted.
[0059]
The gate length of the MOS transistor is an important factor that determines the operation speed. When a portion having a high pattern density and a portion having a high pattern density exist on the semiconductor chip, a wide space portion exists on both sides of the gate electrode pattern in the portion having a low pattern density. In the dense pattern portion, the gate electrode patterns are densely arranged with a narrow interval. In such a pattern shape, a microloading effect (or RIE lag) occurs in which the etching rate is delayed in a dense pattern density portion.
[0060]
According to the conventional technique, a forward taper shape is generated in all patterns, or a reverse taper shape is generated in a portion having a high pattern density.
[0061]
According to the above-described embodiment, first, etching with high anisotropy is performed with the first kind of etching gas, and the tungsten or tungsten silicide layer is anisotropically etched at a portion with a rough pattern density, so that it is almost vertical. Side walls are formed.
[0062]
Following this main etching step, an overetching step of the tungsten or tungsten silicide layer is performed using an etching gas containing chlorine and nitrogen. In this over-etching process, WN_xIt is considered that the sidewall protective film made of is deposited on the pattern sidewall. Further, the deposited amount of this nitride protective film depends on the pattern density. In the portion where the pattern density is rough, a large amount is deposited, and the pattern side wall is strongly protected. On the other hand, in the dense pattern portion, the amount of the nitride protective film to be deposited is small, and the degree to which the etching shape becomes a forward tapered shape can be reduced.
[0063]
When etching is performed using the second type of etching gas from the beginning of etching, a strong forward taper shape is likely to be formed in a region having a large space, but a pattern having a vertical shape in a portion having a rough pattern density. Since the finishing has already been completed, the forward tapered shape can be prevented.
[0064]
Protect the vertical shape of the sidewall of tungsten or tungsten silicide layer with a protective film in a rough pattern density area with a wide space, and reduce the deposition amount of the protective film in a high density pattern area with a narrow space with a reverse taper shape Thus, the degree of forward taper can be reduced.
[0065]
Further, in this over-etching process, when a silicon layer is present under the tungsten or tungsten silicide layer, SiN generated by etching the silicon layer in a region having a low pattern density._xCl_yThus, the side wall can be protected. For this reason, side etching can also be prevented.
[0066]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0067]
【The invention's effect】
As described above, according to the present invention, the tungsten or tungsten silicide layer can be anisotropically etched almost vertically.
[0068]
In the etching of the polycide structure, both the silicide layer and the silicon layer can be etched almost vertically.
[0069]
The amount of side etching can also be suppressed, and high pattern accuracy can be obtained.
[0070]
The dimensional accuracy of etching can be increased, and a high-performance semiconductor integrated circuit can be produced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a semiconductor substrate showing main steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a semiconductor substrate showing the main steps of a method of manufacturing a semiconductor device according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view schematically showing a configuration of an ECR plasma etcher apparatus.
FIG. 4 is a cross-sectional view and a three-dimensional graph for explaining a preliminary experiment conducted by the present inventor.
FIG. 5 is a cross-sectional view of a semiconductor substrate for explaining a conventional technique.
[Explanation of symbols]
1 Si substrate, 2 SiO₂ Layer, 3 silicon layer, 4 tungsten silicide layer, 5, 6 opening, 7 resist pattern, 8, 9, 10 plasma

Claims (6)

Etching including an isolated pattern sandwiched between a wide space portion and a plurality of dense patterns arranged via a narrow space portion on an etching target layer formed on the base surface and formed of tungsten or tungsten silicide. Forming a mask;
Through the etching mask, the first etching step the etching target layer is etched by the first kind of gas containing a gas and the oxygen gas containing chlorine to expose the underlying surface of the large space portion,
Following the first etching step, the second type of etching gas containing gas and the nitrogen gas containing chlorine, etching and a second etching step of etching the remaining etched layer method. The etching method according to claim 1, wherein the gas containing chlorine is at least one of Cl ₂ , HCl, BCl ₃ , SiCl ₄ , S ₂ Cl ₄ , and CCl ₄ . An isolated pattern and a narrow space portion sandwiched between wide spaces on an etching target layer formed of tungsten or tungsten silicide, which is formed on a base surface having a silicon layer as an uppermost layer formed on an insulating layer. Forming an etching mask including a plurality of dense patterns arranged via
Through the etching mask, the etching target layer is etched with a first type gas containing chlorine and oxygen gas so that the side walls are substantially vertical , and the base surface of the wide space portion is exposed. 1 etching process,
Following the first etching step, a second etching step of etching the remaining etching target layer with a second type of gas containing chlorine and nitrogen gas ,
An etching method including a third etching step of etching the silicon layer with the first type gas following the second etching step. A plurality of layers are formed on the base insulating layer and arranged on the etching target layer formed of the silicon layer and the tungsten layer or the tungsten silicide layer, with an isolated pattern sandwiched between the wide space portions and a narrow space portion. Forming an etching mask including a dense pattern;
  Through the etching mask, the tungsten layer or the tungsten silicide layer as the etching target layer is etched with a first type gas including a chlorine-containing gas and an oxygen gas to expose the surface of the silicon layer in the wide space portion. A first etching step;
  Following the first etching step, a second etching step of etching the remaining etching target layer with a second type of gas containing chlorine and nitrogen gas,
  A third etching step of ending the second etching step and etching the remaining silicon layer with the first type gas before exposing the base insulating layer in the wide space portion;
Etching method including: A plurality of layers are formed on the base insulating layer and arranged on the etching target layer formed of the silicon layer and the tungsten layer or the tungsten silicide layer, with an isolated pattern sandwiched between the wide space portions and a narrow space portion. Forming an etching mask including a dense pattern;
  Through the etching mask, the tungsten layer or the tungsten silicide layer as the etching target layer is etched with a first type gas including a chlorine-containing gas and an oxygen gas to expose the surface of the silicon layer in the wide space portion. A first etching step;
  Following the first etching step, a second etching step of etching the remaining etching target layer with a second type of gas containing chlorine and nitrogen gas,
  A third etching step of ending the second etching step after the underlying insulating layer in the wide space portion is exposed and etching the remaining silicon layer with the first type of gas;
Etching method including: Etching including an isolated pattern sandwiched between a wide space portion and a plurality of dense patterns arranged via a narrow space portion on an etching target layer formed on the base surface and formed of tungsten or tungsten silicide. Forming a mask;
Using a first type of gas containing a gas and an oxygen gas containing chlorine, the etching target layer is etched into a substantially vertical shape sidewalls, a first etching step for exposing the underlying surface of the large space portion When,
Using a second type of gas including chlorine and nitrogen gas , more nitride is deposited on the side wall facing the wide space portion than on the side wall facing the narrow space portion. Side etching is suppressed, and the remaining etching target layer is etched so that the side wall facing the wide space part and the side wall facing the narrow space part are formed substantially perpendicularly, thereby completing the patterning. An etching method including the etching step.

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