JP2004031892A - Method for manufacturing semiconductor device using amorphous carbon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for selectively etching or almost completely peeling a carbon film against a resist film. <P>SOLUTION: An amorphous carbon film 46 is formed on a substrate on which a film to be patterned is formed. A resist pattern 47 is formed on the surface of the amorphous carbon film. At least one gas of a group configured of gas containing reducing fluoride gas, halogen gas, and oxygen is used, and the substrate is heated at 70°C to 450°C, and the amorphous carbon film in an area which is not covered with any resist pattern is removed by dry etching. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a method for manufacturing a semiconductor device using amorphous carbon (aC: H), and more particularly, to a method for manufacturing a semiconductor device using aC: H as an anti-reflection film when exposing a photoresist film. .
[0002]
Here, aC: H refers to a hydrocarbon compound containing carbon and hydrogen, and includes a compound having a structure close to the crystal structure of carbon to a compound having a structure close to an organic substance.
[0003]
[Prior art]
Japanese Patent Application Laid-Open No. Sho 60-235426 discloses a method of depositing carbon on an Al surface to a thickness of about 1000 ° as an antireflection film at the time of photoresist exposure. It is taught that the deposition of carbon can suppress the constriction of the pattern.
[0004]
However, it is not clear what kind of carbon film is formed to ensure the antireflection effect in photolithography. When a carbon film is used as an antireflection film, a technique for etching the carbon film becomes important, but an etching technique having sufficient processing accuracy in a semiconductor process has not yet been developed.
[0005]
For example, a method of performing reactive ion etching at room temperature with an oxygen gas, a method of performing etching at room temperature using CF ₄ / CHF ₃ / Ar as an etching gas using an SiO ₂ film etching apparatus, and an Al etching apparatus are used. A method of performing etching at room temperature using Cl ₂ / BCl ₃ as an etching gas, or a method of using a W etching apparatus and etching at room temperature using SF ₆ / N ₂ as an etching gas. However, the above method does not provide a sufficient etching rate and a sufficient selectivity to the resist film.
[0006]
Also, in the case of removing the carbon film, a down-flow type in which plasma is generated by microwave using an etching gas such as O ₂ or O ₂ / CF _{4 and} separation is performed by oxygen radicals, or an etching gas such as O ₂ A method such as a barrel type in which high-frequency plasma is generated by using a method and stripping is performed by oxygen radicals is considered, but it is difficult to perform sufficient stripping.
[0007]
When a resist film is applied on a carbon film and exposed and developed, a desired resist pattern may not be obtained. In such a case, a resist film is created (remade) again. The antireflection carbon film and the resist film thereon may be peeled off and remade, but the process becomes complicated. A technique for removing only the resist film without damaging the antireflection effect of the underlying carbon film has not been established.
[0008]
[Problems to be solved by the invention]
When a fine pattern, particularly a pattern of 1 μm or less, is formed on a substrate having a high reflectance, a sufficient effect cannot be obtained only by depositing carbon on the substrate. This is considered to be mainly due to the effect of the reflected light, which is the exposure light transmitted through the antireflection film and reflected on the substrate surface having a high reflectance. Since reflection from the surface of the antireflection film cannot be completely prevented, it is considered that there is an influence of light reflected from the surface of the antireflection film.
[0009]
For this reason, the line width of the resist pattern formed on the substrate having a step may change depending on the shape of the base. Further, since the binding energy of the carbon film is very high, the etching rate is low and the etching selectivity with the resist is low in the conventional method. For this reason, if a carbon film is used as the antireflection film, it is necessary to make the resist film thicker, and on the contrary, the exposure accuracy may be deteriorated.
[0010]
It is also difficult to completely remove the carbon film. For example, if the carbon film cannot be completely removed and the carbon film remains between the W wiring and the interlayer insulating film, the adhesion between the W wiring and the carbon film and between the carbon film and the interlayer insulating film deteriorates. . If the carbon film remains when the contact hole is formed, good electrical connection cannot be obtained.
[0011]
An object of the present invention is to provide a technique for etching a carbon film with good selectivity to a resist film and a technique for almost completely removing the carbon film.
[0012]
[Means for Solving the Problems]
According to one aspect of the present invention, a step of forming an amorphous carbon film on a substrate on which a film to be patterned is formed, a step of forming a resist pattern on the surface of the amorphous carbon film, Using at least one gas from the group consisting of halogen gas and oxygen-containing gas, heating the substrate at 70 ° C. to 450 ° C. to form the amorphous carbon film in a region not covered with the resist pattern, And a step of removing by dry etching.
[0013]
[Action]
By heating the substrate to 70 ° C. to 450 ° C. using a reducing fluoride gas, a halogen gas, or a gas containing oxygen, the aC: H film can be efficiently etched.
[0014]
【Example】
The principle of the embodiment of the present invention will be described with reference to FIG. FIG. 1 shows the light intensity in the resist film. A transparent film 2, an aC: H film 3, and a resist film 4 are formed in this order on a highly reflective substrate 1 having a high reflectance. When light enters from the surface of the resist film 4, the light is reflected on the aC: H film 3, the transparent film 2, and the surface of the high-reflection substrate 1, and the incident light and the reflected light overlap within the resist film 4. Normally, since the amplitudes of the incident light and the reflected light are different, there is no point where the intensity of the light in the resist film 4 becomes completely zero, and the maximum and the minimum are repeated at a half-wave period as shown in FIG.
[0015]
The periodic change in light intensity as a function of location indicates that standing waves are formed in the resist film. When the average of the light intensity is I _ave and the amplitude of the intensity change is Iδ, the magnitude I _sw of the standing wave in the resist film 4 is normalized by the average light intensity, and I _sw = I δ / I _ave Define. For example, if the amplitudes of the incident light and the reflected light are equal, a complete standing wave is generated in the resist film 4, so that Iδ = I _ave , and the magnitude I _sw of the standing wave is 1. In addition, since Iδ = 0 when there is no reflected wave with only incident light, the magnitude I _sw of the standing wave is 0. That is, the smaller the reflection from the base, the smaller the magnitude I _sw of the standing wave.
[0016]
If the magnitude I _{sw of the} standing wave is reduced, the intensity of the reflected light and thus the magnitude of the halation is also reduced, so that a finer pattern can be exposed with high precision. FIG. 2 shows a change in the magnitude I _sw of the standing wave with respect to the thickness of the transparent film and the thickness of the antireflection film. The horizontal axis represents the thickness of the transparent film in units of Å, and the vertical axis represents the thickness of the aC: H film in units of Å. The number corresponding to each curve indicates the magnitude I _sw of the standing wave. The figure shows an exposure wavelength of 365 nm, a high-reflection substrate 1 with a base WSi layer with a complex refractive index of 2.94 to 2.66i, and a transparent film 2 with a high-temperature oxide film (HTO) with a refractive index of 1.48. Simulation results when the complex refractive index of the film 3) and the complex refractive index of the aC: H film 3 are 1.58-0.752i and the complex refractive index of the resist film 4 is 1.65-0.02i. Here, i represents an imaginary unit.
[0017]
From FIG. 2, it can be seen that when the transparent film is about 400 ° and the aC: H film is about 300 °, the size of the standing wave is minimized. FIG. 3 shows the case where the film thickness of the aC: H film was fixed at 300 ° and the film thickness of the transparent film was changed, and the film thickness of the aC: H film was fixed at 400 °. It shows the magnitude of the standing wave when the thickness is changed. The horizontal axis represents the thickness of the aC: H film or the transparent film in the unit Å, and the vertical axis represents the magnitude of the standing wave I _sw . In the figure, ○ indicates the magnitude of the standing wave corresponding to the thickness of the transparent film when the thickness of the aC: H film is fixed at 300 °, and ● indicates the case where the thickness of the transparent film is fixed at 400 °. 3 shows the magnitude of the standing wave with respect to the thickness of the aC: H film. It can be seen that when the thickness of the aC: H film is 300 ° and the thickness of the transparent film is 400 °, the magnitude I _{sw of the} standing wave is 0.05, which is the minimum.
[0018]
When a pattern having a line width of 0.3 μm is formed, it is preferable to suppress the dimensional variation to 10% of the line width, that is, within 0.03 μm. For this purpose, it is desired that the magnitude of the standing wave be 0.2 or less. In order to reduce the magnitude of the standing wave to 0.2 or less, the thickness of the transparent film may be 250 to 550 ° when the thickness of the aC: H film is 300 °. When the thickness of the transparent film is 400 °, the thickness of the aC: H film may be set to 210 to 450 °. More preferably, the film thickness of the aC: H film and the film thickness of the transparent film are within ± 20% of 300 ° and 400 °, respectively, that is, within ± 20% from the film thickness giving the minimum value of the standing wave. The film thickness may be set as follows.
[0019]
In the above simulation, the case was considered where the imaginary part (extinction coefficient) of the complex refractive index of the transparent film was 0. However, if the extinction coefficient is 0.2 or less, the film may be considered as a substantially transparent film. it can. Although an aC: H film having an extinction coefficient of 0.752 was considered as an antireflection film, any film having an extinction coefficient of 0.3 or more can be used as an antireflection film.
[0020]
Next, an embodiment based on the above consideration will be described. A substrate with a WSi surface having a complex refractive index of 2.94 to 2.66i as a high reflection substrate, an aC: H film having a complex refractive index of 1.58 to 0.75i as an antireflection film, a thickness of 300 °, and a complex as a resist film The resist film was patterned on a sample using a novolak-based resist film having a refractive index of 1.65 to 0.02i and a thickness of 0.76 μm. For comparison, a sample having a transparent film thickness of 1000 ° was also patterned.
[0021]
FIGS. 4A and 4B show resists when the thickness of the transparent film is 1000 °, and when the thickness of the aC: H film is 300 ° and the thickness of the transparent film is 400 °, respectively. 2 shows a sketch of an SEM photograph of the substrate surface after film patterning.
[0022]
As shown in FIGS. 4A and 4B, a linear resist pattern having an inclined surface 12a or 12b and an upper surface 11a or 11b is formed on the transparent film 10 in the vertical direction in the figure. Note that a step is formed on the surface of the substrate in the lateral direction of the drawing.
[0023]
In FIG. 4 (A), as shown in the shape of the upper surface 11a, the line width becomes thicker or thinner at the step portion on the substrate surface. Further, in FIG. 4B in which the thicknesses of the aC: H film and the transparent film are optimized, the line width is substantially constant regardless of the step on the substrate surface.
[0024]
FIGS. 2 and 3 show the case of i-line with an exposure wavelength of 365 nm, but the optimum film thickness is different if the exposure wavelength is different. For example, when the exposure wavelength is 248 nm, a similar simulation shows that when the thickness of the amorphous carbon film is 200 to 500 ° and the thickness of the SiO ₂ film is 50 to 300 ° or 700 to 1100 °, the standing wave It is derived that the size can be reduced.
[0025]
As described above, by optimally selecting the thicknesses of the aC: H film and the transparent film, the line width of the fine pattern can be formed substantially constant regardless of the step of the underlying substrate. In the above embodiment, the case where the aC: H film is used as the anti-reflection film and the SiO ₂ film is used as the transparent film, but other materials may be used. For example, a carbon film containing no or little H may be used as the antireflection film. Further, PSG refractive index from 1.48 to 2.0 as the transparent film, BSG, inorganic glass mainly comprising SiO ₂ such as BPSG, refractive index may be used about 2 SiN film or the like. In this case, the optimum film thickness may be set according to the complex refractive index of each material.
[0026]
Next, a technique for etching a carbon film or an aC: H film will be described. FIG. 5 shows the relationship between the ashing speed and the temperature when the carbon film and the resist film formed by sputtering are separated by the downflow of microwave plasma. The horizontal axis represents the reciprocal of the temperature in units of 1000 / K, and the vertical axis represents the ashing speed in units of Å / min. The solid line a in the figure shows the ashing speed of the sputtered carbon film, and the solid line b shows the ashing speed of the resist film.
[0027]
Here, an i-line resist (ZIR-9100) was used as the resist film. Ashing was performed under the conditions of O ₂ flowing at 1000 sccm as an ashing gas, a pressure of 1.0 Torr, and a microwave power of 1.0 kW.
[0028]
From the graph, it can be seen that the temperature needs to be about 70 ° C. or more in order to peel off the carbon film at a significant speed. Considering that the ashing rate of about 500 ° / min is preferable in view of further improving the throughput of the semiconductor process by 100 ° / min, the substrate temperature is preferably about 150 ° C or more, more preferably 200 ° C or more. If the temperature is 450 ° C. or higher, the carbon as the antireflection film does not exist as a film, so the substrate temperature needs to be 450 ° C. or lower.
[0029]
When an Al wiring is used, ashing needs to be performed, for example, by flowing O ₂ gas at 1000 sccm and CF ₄ gas at 60 sccm, at a pressure of 1.0 Torr, and at a microwave power of 1.0 kW. In this case, it is preferable to first strip the resist film at a low temperature of about 30 ° C., and then heat the substrate to strip the carbon film. This is because the sidewall fence remains when the substrate is heated from the beginning. At about 30 ° C., the carbon film cannot be peeled off.
[0030]
FIG. 5 shows the case where the carbon film is peeled off by down-flow of microwave plasma using O ₂ gas. However, the substrate is also heated when the carbon film is removed by RIE, electron cyclotron resonance etching (ECR), or the like. This can increase the etching rate.
[0031]
For example, etching may be performed by RIE under the conditions of an O ₂ gas flowing at 150 sccm as an etching gas, a pressure of 0.2 Torr, and a high frequency power of 150 W. Alternatively, etching may be performed by RIE under the conditions of a flow of 50 sccm of CF ₄ / CHF ₃ as an etching gas and a pressure of 0.05 Torr and a high frequency power of 350 W. Under this condition, if there is an SiO ₂ film under the carbon film, the SiO ₂ film can be etched at the same time.
[0032]
Alternatively, etching may be performed by RIE at a flow rate of 40 sccm / 40 sccm of SF ₆ / N ₂ as an etching gas, a pressure of 0.05 Torr, and a high-frequency power of 350 W. Under this condition, if there is a blanket tungsten film (BW film) under the carbon film, the BW film can be etched at the same time. Even under these conditions, it is preferable that the substrate temperature be 70 ° C to 450 ° C.
[0033]
As the etching gas, other than the above, a fluorine compound gas such as NF ₃ , a halogen gas such as Br ₂ and I ₂ , a gas containing oxygen such as CO and CO ₂ , or a mixed gas thereof may be used.
[0034]
Alternatively, the carbon film may be etched by ECR under the conditions of a flow of 40 sccm / 60 sccm of Cl ₂ / BCl ₃ as an etching gas, a pressure of 4.0 mTorr, a microwave power of 800 W, and a high frequency power of 150 W. Note that, in this case, it is preferable that the substrate temperature be 100 ° C. to 450 ° C. By etching under these conditions, if there is an Al film under the carbon film, the Al film can be etched at the same time.
[0035]
Next, a method for preventing local damage to the substrate surface due to reflection of ions from the side surfaces of the resist film during RIE by using the aC: H film used as the antireflection film as an etching mask will be described. .
[0036]
First, conventional problems will be described with reference to FIGS. As shown in FIG. 6A, a field oxide film 21 is formed on the surface of a silicon substrate 20 to define an active region. A gate insulating film 22 is formed in an active region on the surface of the silicon substrate 20. On the gate insulating film 22 and the field oxide film 21, conductive films 23 and 24 such as amorphous Si, polysilicon, and silicide are formed. On the conductive film 24, an insulating film 25 such as a SiO ₂ film is formed.
[0037]
A photoresist film 26 is applied on the insulating film 25, and an insulating film 27 such as SOG is applied thereon. On the insulating film 27, a resist pattern 28 is formed in a region where a gate electrode is to be formed.
[0038]
As shown in FIG. 6B, the insulating film 27 is selectively dry-etched using the resist pattern 28 as a mask. After the etching, the resist pattern 28 is removed.
[0039]
As shown in FIG. 6C, the resist film 26 is selectively dry-etched using the insulating film 27 as a mask. As shown in FIG. 7A, the insulating film 25 is selectively dry-etched using the resist film 26 as a mask. At this time, the insulating film 27 on the resist film 26 is also removed at the same time.
[0040]
As shown in FIG. 7B, the conductive films 23 and 24 are dry-etched using the resist film 26 as a mask to form a gate electrode. At this time, if the dimensional variation in etching the resist film 26 in the step of FIG. 6C is large, the accuracy of the gate length becomes unstable.
[0041]
On the other hand, as shown by an arrow in FIG. 7B, ions are reflected on the side surface of the resist film 26 and collide with the substrate surface near the gate electrode. The substrate surface near the gate electrode is locally etched by the reflected ions. When the etching is stopped immediately after the gate insulating film is exposed in order to suppress excessive etching near the gate electrode, a conductive film region 23 a remains on the end surface of the field oxide film 21. When the conductive film region 23a remains, it causes a leak current between semiconductor elements or between a source and a drain.
[0042]
As shown in FIG. 7C, when the region 23a of the conductive film is to be completely removed, the vicinity of the gate electrode is excessively etched, and a groove 29 is formed. As shown in FIG. 7D, ion implantation is performed using the gate electrode portion as a mask to form a source region 30 and a drain region 31. Note that an LDD structure may be formed by forming a sidewall in the gate electrode portion and performing ion implantation again. Next, an interlayer insulating film 32 is formed, a contact hole is formed in the source region 30 and the drain region 31, and a source electrode 33 and a drain electrode 34 are formed.
[0043]
In the MOSFET of FIG. 7D, since the trench 29 is formed near the gate electrode of the source region 30 and the drain region 31, no drain current flows. As described above, reflection of ions from the side surface of the resist film 26 causes an element defect.
[0044]
Next, an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 8A, a field oxide film 41 is formed on the surface of a silicon substrate 40 to define an active region. A gate insulating film 42 is formed in an active region on the surface of the silicon substrate 40. On the gate insulating film 42 and the field oxide film 41, a conductive film 43 made of amorphous Si and a conductive film 44 made of WSi are formed by lamination. On the conductive film 44, an insulating film 45 such as a SiO ₂ film is formed.
[0045]
An aC: H film 46 is formed on the insulating film 45. On the aC: H film 46, a resist pattern 47 is formed in a region where a gate electrode is to be formed.
[0046]
As shown in FIG. 8B, the aC: H film 46 and the insulating film 45 are selectively dry-etched using the resist pattern 48 as a mask. The etching conditions are as follows: CF ₄ / CHF ₃ / Ar gas flow rate is 60/10/400 sccm, pressure is 500 mTorr, and input power is 500 W.
[0047]
As shown in FIG. 8C, using the resist pattern 47 as a mask, the conductive film 44 is selectively dry-etched using a chlorine-based gas. At this time, the etching is stopped on the surface of the conductive film 43 by time control or the like.
[0048]
As shown in FIG. 9A, the resist pattern 47 on the aC: H film 46 is removed. As shown in FIG. 9B, the conductive film 43 is dry-etched using the aC: H film 46 as a mask to form a gate electrode. At this time, the etching is performed while lowering the input high frequency power of the etching to lower the etching rate and increasing the selectivity between the gate insulating film 42 and the conductive film 43. After the etching, the aC: H film 46 is removed.
[0049]
As shown in FIG. 9C, ion implantation is performed using the gate electrode portion as a mask to form a source region 49 and a drain region 50. Note that an LDD structure may be formed by forming a sidewall in the gate electrode portion and performing ion implantation again. Next, an interlayer insulating film 48 is formed, contact holes are provided in the source region 49 and the drain region 50, and a source electrode 51 and a drain electrode 52 are formed.
[0050]
According to this embodiment, in the step of FIG. 9B, since the resist film is not used as a mask, there is no reflection of ions from the side surface of the resist film. For this reason, the vicinity of the gate electrode on the substrate surface can be prevented from being excessively etched. Since there is no local damage near the gate electrode, the conductive film 43 on the end face of the field oxide film 41 can be completely removed.
[0051]
2. Description of the Related Art In today's semiconductor processes in which integrated circuits have been miniaturized, the accuracy of overlay during photolithography has become extremely strict. If the overlay accuracy is lower than the reference value, the resist pattern is stripped and patterned again. When a chemically amplified negative resist is used as the resist, oxygen plasma ashing is usually used for stripping the resist.
[0052]
However, when the chemically amplified negative resist on the aC: H film is stripped by this method, at least a part of the aC: H film is also stripped at the same time. If a trace remains on the aC: H film, the process must be repeated from the step of depositing the aC: H film, and rework is large. For this reason, a method of stripping only the chemically amplified negative resist without stripping the aC: H film is desired.
[0053]
Hereinafter, an example of stripping the chemically amplified negative resist on the aC: H film will be described.
A chemically amplified negative resist was formed on the aC: H film, and the chemically amplified negative resist was removed using a mixed solution of conc sulfuric acid and a 1.3% by weight aqueous hydrogen peroxide solution. The etching rate of the aC: H film by this etchant was about 1.5 ° / min, which was substantially negligible. On the other hand, all of the chemically amplified negative resist could be removed in about 1 to 3 minutes.
[0054]
The exposed portion of the aC: H film is exposed to an etchant for 1 to 3 minutes, and the film thickness etched during this time is about 1.5 to 4.5 °. Usually, when an aC: H film is used as an antireflection film, its film thickness is about 200 ° or more. Therefore, even if it is etched by 4.5 °, it is about 2% of the whole film thickness, and there is no hindrance to the function as the antireflection film.
[0055]
Note that only conch sulfuric acid may be used as an etchant. The same effect can be obtained if the ratio of the 1.3% by weight aqueous hydrogen peroxide solution is 20% or less. Further, an alkaline solution such as ammonium hydroxide, a hydrazine-based compound, or tetramethylammonium hydroxide may be used as an etchant.
[0056]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.
[0057]
【The invention's effect】
As described above, according to the present invention, even when an aC: H film is used as an antireflection film, the aC: H film can be selectively removed with high accuracy and completely removed. Can be. For this reason, it is possible to lead out the wiring via the contact hole with good yield.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a substrate for explaining the intensity of light in a resist film.
FIG. 2 is a graph showing the magnitude of a standing wave in a resist film.
FIG. 3 is a graph showing the magnitude of a standing wave in a resist film.
FIG. 4 is a plan view of a substrate sketched with an SEM photograph of the substrate surface to show a resist pattern formed on the substrate surface.
FIG. 5 is a graph showing an ashing speed of an aC: H film.
FIG. 6 is a cross-sectional view of a substrate for explaining a method of manufacturing a MOSFET according to a conventional example.
FIG. 7 is a cross-sectional view of a substrate for describing a method for manufacturing a MOSFET according to a conventional example.
FIG. 8 is a cross-sectional view of a substrate for describing a method for manufacturing a MOSFET according to an embodiment of the present invention.
FIG. 9 is a cross-sectional view of a substrate for describing a method for manufacturing a MOSFET according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High reflection substrate 2 Transparent film 3 aC: H film 4 Resist film 10 Transparent film 11 a, 11 b Upper surface 12 a, 12 b of resist pattern Slope 20, 40 of silicon substrate 21, 41 Field oxide film 22, 42 Gate insulation Films 23, 24, 43, 44 Conductive films 25, 27, 45 Insulating film 26 Resist film 28, 47 Resist pattern 29 Groove 30, 49 Source region 31, 50 Drain region 32, 48 Interlayer insulating film 33, 51 Source electrode 34 , 52 drain electrode 46 aC: H film

Claims (16)

Forming an amorphous carbon film on the substrate on which the film to be patterned is formed,
Forming a resist pattern on the surface of the amorphous carbon film,
Using at least one gas from the group consisting of a reducing fluoride gas, a gas containing halogen gas and oxygen, heating the substrate at 70 ° C. to 450 ° C. to form an area not covered with the resist pattern Removing the amorphous carbon film by dry etching. The method according to claim 1, wherein the reducing fluoride gas is SF ₆ or NF ₃ . The method according to claim 1, wherein the halogen gas is Cl ₂ , Br _2, or I ₂ . The method for manufacturing a semiconductor device according to claim 1, wherein the gas containing oxygen is O ₂ , CO, or CO ₂ . 2. The method of manufacturing a semiconductor device according to claim 1, wherein said amorphous carbon film removing step is performed by electron cyclotron resonance etching. 2. The method for manufacturing a semiconductor device according to claim 1, wherein said amorphous carbon film removing step is performed by reactive ion etching. 2. The method of manufacturing a semiconductor device according to claim 1, wherein in the step of removing the amorphous carbon film, ashing is performed by downflow of microwave plasma. 2. The method for manufacturing a semiconductor device according to claim 1, wherein in the step of removing the amorphous carbon film, ashing is performed using high-frequency plasma. 9. The method of manufacturing a semiconductor device according to claim 1, wherein said preparing step includes a step of depositing an amorphous carbon film on said substrate by sputtering or chemical vapor deposition (CVD). Forming an amorphous carbon film on the substrate on which the film to be patterned is formed,
Forming a resist pattern patterned in a predetermined region on the surface of the amorphous carbon film,
A first etching step of selectively etching at least the amorphous carbon film using the resist pattern as a mask;
Removing the resist pattern;
A second etching step of selectively etching at least a lower layer portion of the film to be patterned using the amorphous carbon film as a mask. The first etching step includes a step of partially etching an upper layer portion while leaving at least a lower layer portion of the film to be etched, and the second etching step includes: The method for manufacturing a semiconductor device according to claim 10, further comprising a step of etching a portion. The film to be etched includes a lower layer and an upper layer having different etching characteristics from the lower layer,
The first etching step is performed under etching conditions in which the upper layer is etched and the lower layer is hardly etched;
The method of manufacturing a semiconductor device according to claim 11, wherein the second etching step is performed under etching conditions for etching the lower layer. A method of manufacturing a semiconductor device, comprising a step of removing a chemically amplified negative resist pattern formed on the surface of an amorphous carbon film using an acid solution that does not substantially etch the amorphous carbon. 14. The method according to claim 13, wherein the acid solution contains at least sulfuric acid. The method according to claim 14, wherein the acid solution further contains hydrogen peroxide. A method for manufacturing a semiconductor device, comprising a step of stripping a chemically amplified negative resist pattern formed on the surface of an amorphous carbon film using an alkaline solution that does not substantially etch the amorphous carbon.

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