JP2012200982A - Method of preparing substrate and method of manufacturing mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a side face of a pattern become closer to a vertical face without formation of a bowing shape, when forming an irregular pattern on a surface of a substrate in dry etching using a hard mask pattern.SOLUTION: This method of preparing the substrate includes: a first process (S2) of forming a hard mask layer on the substrate; a second process (S3-S5) of forming a resist layer with the hard mask layer covered and then forming a resist pattern by patterning of the resist layer; a third process (S6) of etching the hard mask layer by using the resist pattern as a mask to form the hard mask pattern; and a fourth process (S8) of performing dry etching of the substrate by using the hard mask pattern as the mask to form the irregular pattern on the substrate. In the fourth process (S8), dry etching onto the substrate is performed by using etching gas to which gas contributing to retraction of the hard mask pattern is added, and thus, the hard mask pattern is retracted along with progress of the etching onto the substrate.

Description

  The present invention relates to a substrate manufacturing method and a mold manufacturing method. More specifically, the present invention relates to a substrate manufacturing method and a mold manufacturing method applied when manufacturing a substrate having an uneven pattern.

  The following methods are known as a method for forming an uneven pattern on a substrate. First, a resist pattern is formed on a substrate via a hard mask layer. Next, a hard mask pattern is formed by patterning the hard mask layer using this resist pattern as a mask. Next, the substrate is etched using the hard mask pattern as a mask.

  In the case of forming an uneven pattern on a silicon substrate by such a method, a technique using a silicon oxide film as a hard mask layer is known (see, for example, Patent Document 1). However, if the hard mask layer is formed of a silicon oxide film, the etching selectivity between the hard mask material and silicon cannot be secured so large.

  Conventionally, when etching a silicon oxide film, a technique using chromium or a chromium alloy as an etching mask material has been proposed (for example, see Patent Documents 2 and 3).

JP 2000-208484 A Japanese Patent Laid-Open No. 6-2991090 JP 2003-86513 A

  In general, when forming a concavo-convex pattern on a silicon substrate, if the hard mask layer is formed of a metal film such as chromium, the hard mask layer is made thinner and the pattern is finer and more accurate than when a silicon oxide film is used. Can be achieved.

  However, when the silicon substrate is dry-etched using the hard mask pattern as a mask, the side surface of the pattern formed on the silicon substrate may have a “Boeing shape”. The bowing shape is a shape defined as follows. That is, when a circular hole pattern having a concave cross section is formed on the surface of silicon by etching, the hole diameter of the intermediate depth portion of the circular hole pattern is larger than the hole diameter (opening diameter) of the inlet portion of the circular hole pattern. The shape which becomes. Further, when a groove pattern having a concave cross section is formed on the surface of silicon by etching, the groove width of the intermediate depth portion of the groove pattern is wider than the groove width of the inlet portion of the groove pattern.

  The main reason why the side surface of the pattern formed on the silicon substrate is bowed is that the silicon is side-etched under the hard mask pattern by the isotropic etching of silicon. Specifically, for example, when silicon is etched using a halogen gas, the etching of silicon proceeds isotropically depending on the setting of the process pressure (pressure in the etching chamber). For this reason, silicon is side-etched, and the side surface of the finally obtained pattern becomes a bow shape. In order to avoid this, if the process pressure is lowered, the etching rate of silicon is lowered.

  Further, in so-called deep etching in which a silicon substrate is etched at a high aspect ratio, suppression of side etching is an important issue in order to maintain the verticality of the side surface of the pattern. The influence of side etching becomes particularly large when an imprint mold (master) that needs to form a fine pattern with high accuracy is manufactured. The reason is as follows. That is, in the imprint method, the resist is cured by applying heat or irradiating light with the mold pattern pressed against an uncured resist layer formed on the transfer substrate. At this time, the resist filled in the recessed portion of the pattern by the pressing of the mold is cured according to the shape of the pattern. For this reason, if the side surface of the mold pattern is bowed, the resist will be caught by the mold pattern when the mold is peeled off from the transfer substrate after the resist is cured, making it difficult to peel off the mold from the transfer substrate. become. Further, even if the mold can be peeled from the transferred substrate, the shape of the pattern formed on the transferred substrate may be broken, or the pattern itself may be broken.

  The main object of the present invention is to develop a technique that allows the side surface of a finally obtained pattern to be close to a vertical surface when an uneven pattern is formed on the surface of a substrate by dry etching using a hard mask pattern as a mask. It is to provide.

The first aspect of the present invention is:
A first step of forming a hard mask layer on the substrate;
A second step of forming a resist pattern on the substrate by patterning the resist layer after forming a resist layer in a state of covering the hard mask layer on the substrate after the first step;
After the second step, a third step of forming a hard mask pattern on the substrate by etching the hard mask layer using the resist pattern as a mask;
And a fourth step of forming an uneven pattern on the substrate by dry etching the substrate using the hard mask pattern as a mask after the third step,
In the fourth step, the hard mask pattern is retracted with the progress of the etching of the substrate by dry etching the substrate using an etching gas to which a gas contributing to the recession of the hard mask pattern is added. This is a feature of a substrate manufacturing method.

The second aspect of the present invention is:
In the second step, the opening size of the hard mask pattern obtained when the hard mask layer is etched using the resist pattern as a mask in the third step is smaller than a predetermined size. Form a resist pattern,
In the fourth step, the substrate is etched so that the opening size of the hard mask pattern becomes the specified size by the recession of the hard mask pattern. This is a manufacturing method.

The third aspect of the present invention is:
In the first step, a silicon substrate is used as the substrate, and the hard mask layer is formed of chromium or a chromium alloy,
In the fourth step, oxygen gas is added as a gas that contributes to the recession of the hard mask pattern. The substrate manufacturing method according to the first or second aspect, wherein the oxygen gas is added.

The fourth aspect of the present invention is:
An imprint mold is obtained by applying the substrate manufacturing method according to the first, second, or third aspect to form an uneven pattern on the substrate. .

  According to the present invention, when an uneven pattern is formed on the surface of a substrate by dry etching using a hard mask pattern as a mask, the side surface of the finally obtained pattern can be brought close to a vertical surface.

It is a flowchart which shows the basic procedure of the board | substrate preparation method which concerns on embodiment of this invention. It is FIG. (1) explaining the processing content of each process of the board | substrate preparation method which concerns on embodiment of this invention. It is FIG. (2) explaining the processing content of each process of the board | substrate preparation method which concerns on embodiment of this invention. It is a figure explaining the example of receding of a hard mask pattern. It is a schematic diagram which shows the progress state of the etching of a silicon substrate in time series. It is a figure which shows the shape of the pattern obtained by the experimental result.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the embodiment of the present invention, description will be given in the following order.
1. 1. Basic procedure of substrate manufacturing method 2. Description of characteristic processes Experimental results 4. Effects of the embodiment Modified example

<1. Basic procedure of substrate fabrication method>
First, a basic procedure of the substrate manufacturing method according to the embodiment of the present invention will be described.
As shown in FIG. 1, the substrate manufacturing method according to the embodiment of the present invention mainly includes a substrate preparation step S1, a hard mask layer formation step S2, a resist layer formation step S3, a resist exposure step S4, It includes a resist developing step S5, a hard mask pattern forming step S6, a resist pattern removing step S7, a substrate etching step S8, and a hard mask pattern removing step S9.
Hereinafter, each process is demonstrated using FIG. 2 and FIG.

(Substrate preparation step S1)
First, as shown in FIG. 2A, a substrate 1 to be processed is prepared. The substrate 1 is, for example, a flat substrate having a circular shape in a plan view, and has a thickness that provides appropriate rigidity. As the substrate 1, a substrate that can be dry-etched in a substrate etching step S8 described later is used. Specifically, a silicon substrate, a quartz substrate, or the like can be used. In this embodiment, as an example, a silicon substrate is used as the substrate 1. In the following description, “substrate 1” is described as “silicon substrate 1”.

(Hard mask layer forming step S2)
Next, as shown in FIG. 2B, a hard mask layer 2 is formed over the silicon substrate 1. Specifically, the hard mask layer 2 is formed so as to cover the surface of the silicon substrate 1. The surface of the silicon substrate 1 described here refers to a surface made of silicon that hardly contains silicon oxide. However, the silicon surface constituting the silicon substrate 1 has a thin silicon oxide layer bonded to oxygen present in the atmosphere or in the etching chamber, even if not specifically intended for handling or processing of the silicon substrate 1. A film (natural oxide film) is formed. In this case, the silicon oxide film covering the surface of the silicon substrate 1 is a very thin film. For this reason, as soon as etching of the silicon substrate 1 is started in a substrate etching step S8 described later, the silicon oxide film is removed, and silicon is subsequently etched. Therefore, the substrate manufacturing method according to the present embodiment is not limited to the case where the surface of the silicon substrate 1 is made of only silicon, but the case where the silicon surface is covered with the thin silicon oxide film or the etching. The same applies to the case where the film is covered with a thin film that does not interfere with the above.

  The hard mask layer 2 serves as a mask pattern when the silicon substrate 1 is etched in a substrate etching step S8 described later. The hard mask layer 2 is formed using a hard mask material. As the hard mask material, a metal (including alloy) material can be used. Specifically, for example, chromium or a chromium alloy (such as chromium nitride) can be preferably used. The hard mask layer 2 can be formed by using, for example, a sputtering method. At that time, it is preferable to make the thickness of the hard mask layer 2 as thin as possible in consideration of the accuracy of the uneven pattern finally formed on the silicon substrate 1. Specifically, for example, the thickness is 5 nm or less.

(Resist layer forming step S3)
Next, as shown in FIG. 2C, a resist layer 3 is formed on the silicon substrate 1 so as to cover the hard mask layer 2. The resist layer 3 is formed by using, for example, a spin coating method. As a resist material, for example, a resist material for electron beam drawing, such as a resist material containing a polymer of α-chloromethacrylate and α-methylstyrene (specifically, ZEP520A manufactured by Nippon Zeon Co., Ltd.). ) Can be used. Then, such a resist material is formed into a predetermined thickness on the upper surface of the hard mask layer 2 by spin coating, and then a baking process is performed to form the resist layer 3. The thickness of the resist layer 3 is set such that the resist layer 3 (resist pattern 3P) remains until the etching is completed when the hard mask layer 2 is etched in a hard mask pattern forming step S6 described later.

(Resist exposure step S4)
Next, as a process for patterning the resist layer 3, exposure and development of the resist layer 3 are sequentially performed. Specifically, as shown in FIG. 2D, the resist layer 3 on the silicon substrate 1 is exposed by electron beam irradiation. In this resist exposure process, for example, the resist layer 3 is exposed in a predetermined pattern by irradiating a predetermined portion of the resist layer 3 with an electron beam using an electron beam drawing apparatus. At this time, when the resist layer 3 is formed using a positive resist material, the portion irradiated with the electron beam (exposed portion) is solubilized. When the resist layer 3 is formed using a negative resist material, the portion irradiated with the electron beam is insolubilized. In this embodiment, as an example, the resist layer 3 is formed using a positive resist material.

(Resist development step S5)
Next, as shown in FIG. 3A, the resist layer 3 on the silicon substrate 1 is developed to form a resist pattern 3P. In this resist development step, for example, by supplying a developer to the exposed resist layer 3, the exposed portion of the resist layer 3 is melted and removed by the developer. Examples of the developer include a solution containing a fluorocarbon-containing solvent (specifically, Vertrel XF (registered trademark), manufactured by Mitsui DuPont Fluorochemical Co., Ltd.), acetic acid-n-amyl, ethyl acetate or a mixture thereof. A solution containing a solvent (specifically, ZED-N50 (manufactured by Zeon Corporation)), a mixed solution of these solutions, or the like can be used. As a result, the resist pattern 3P is formed on the silicon substrate 1 via the hard mask layer 2.
In the following description, the formation process of the resist pattern 3P including the resist layer formation process S3, the resist exposure process S4, and the resist development process S5 is described as a “resist pattern formation process”.

(Hard mask pattern forming step S6)
Next, as shown in FIG. 3B, the hard mask layer 2 is etched using the resist pattern 3P as a mask to form the hard mask pattern 2P. This hard mask pattern forming step can be performed, for example, using a mixed gas composed of chlorine gas and oxygen gas when the hard mask layer 2 is a metal film made of chromium or a chromium alloy. Thereby, the portion of the hard mask layer 2 that is not covered with the resist pattern 3P is removed. Therefore, the hard mask layer 2 is patterned following the pattern shape of the resist pattern 3P. As a result, the hard mask pattern 2P and the resist pattern 3P are formed on the silicon substrate 1 so as to overlap each other.

(Resist pattern removal step S7)
Next, as shown in FIG. 3C, the resist pattern 3P is removed from the silicon substrate 1. The removal of the resist pattern 3P is performed with, for example, a resist stripping solution.

(Substrate etching step S8)
Next, as shown in FIG. 3D, the silicon substrate 1 is dry-etched using the hard mask pattern 2P as a mask. Specifically, the silicon substrate 1 is etched by reactive ion etching (RIE). As a result, an uneven pattern 5 is formed on the silicon substrate 1 following the pattern shape of the hard mask pattern 2P. At this time, on the surface of the silicon substrate 1, the recessed portion by etching becomes a concave pattern 5 a and the other portion becomes a convex pattern 5 b. And the uneven | corrugated pattern 5 is formed entirely by the combination of these patterns 5a and 5b.

(Hard mask pattern removal step S9)
Next, as shown in FIG. 3E, the hard mask pattern 2P is removed from the silicon substrate 1. The hard mask pattern 2P is removed, for example, with a chromium etching solution when chromium is used as the hard mask material.

<2. Explanation of characteristic process>
Subsequently, a characteristic process among the plurality of processes (S1 to S9) will be described.

  First, in the resist pattern forming step (S3 to S5), the resist pattern 3P is formed under the condition that the opening size of the hard mask pattern 2P formed in the subsequent hard mask pattern forming step S6 is smaller than the “specified size”. Keep it. Specifically, in the resist exposure step S4, the resist layer 3 is exposed so as to satisfy such dimensional conditions. For example, when the resist layer 3 is exposed using an electron beam drawing apparatus, the time when the resist layer 3 is irradiated with an electron beam and the time when the resist layer 3 is not irradiated are determined using a blanking electrode provided in the electron beam drawing apparatus. By controlling, the resist layer 3 is exposed so as to satisfy the above dimensional conditions. Then, when the resist layer 3 is developed in the subsequent resist development step S5 and the hard mask layer 2 is etched using the resist pattern 3P obtained thereby as a mask, the opening dimension of the hard mask pattern 2P is a specified dimension. To be smaller.

  The “specified dimension” described here refers to a design dimension defined as the opening dimension of the concave pattern 5 a described above in the uneven pattern finally formed on the silicon substrate 1. More specifically, when the concave pattern 5a is a circular hole pattern, the hole diameter is the opening dimension of the concave pattern 5a, and thus the dimension defined by the hole diameter is the “specified dimension”. Further, when the concave pattern 5a is a groove pattern, the groove width is the opening dimension of the concave pattern 5a, and the dimension defined by the groove width is the “specified dimension”.

On the other hand, in the substrate etching step S8, for example, a halogen gas can be used as a reactive gas contributing to the etching of the silicon substrate (silicon). Specifically, a fluorine-based gas, more specifically CF ₄ or the like can be used. The reaction gas such as halogen gas used here is the gas having the highest mixing ratio among the gases contained in the etching gas. In the substrate etching step S8, a gas that contributes to the recession of the hard mask pattern 2P is added to the etching gas. For example, when the hard mask layer 2 that is the basis of the hard mask pattern 2P is formed of chromium or a chromium alloy, oxygen gas can be used as a gas that contributes to the recession of the hard mask pattern 2P. With respect to this oxygen gas, the flow rate ratio when the etching gas is introduced into the etching chamber is smaller than the halogen gas described above. For example, the proportion of oxygen gas is preferably 20% or less.

  Incidentally, due to the configuration of the dry etching apparatus (RIE apparatus) used for etching the silicon substrate 1, the addition of oxygen gas is performed through a separate pipe from the halogen gas that is the main etching gas. Specifically, a pipe (gas pipe) for introducing halogen gas into the etching chamber and a pipe for introducing oxygen gas into the etching chamber are separate systems. The introduction of the halogen gas and the introduction of the oxygen gas can be individually controlled by separately driving a flow rate control valve or the like provided for each gas type system. For this reason, the timing for introducing (adding) oxygen gas into the etching chamber can be set separately from the introduction of the halogen gas. In the present embodiment, oxygen gas is continuously added from the start to the end of dry etching of the silicon substrate 1.

  Here, the receding of the hard mask pattern will be described. “Retraction of the hard mask pattern” means that the position of the opening edge of the hard mask pattern changes in the direction in which the opening dimension of the hard mask pattern increases. For example, if the opening of the hard mask pattern is a circular hole, it means that the position of the opening edge of the hard mask pattern changes in the direction in which the hole diameter increases. In addition, if the opening of the hard mask pattern is a groove, the position of the opening edge of the hard mask pattern changes in the direction in which the groove width increases.

  More specifically, when the opening of the hard mask pattern is a circular hole, as shown in FIGS. 4A to 4C, the hole diameter of the opening portion of the hard mask pattern 2P changes from D1 → D2 → D3. The phenomenon in which the position of the opening edge of the hard mask pattern 2P changes in the direction to be referred to as “retreat”. In this case, the hole diameter of the opening portion of the hard mask pattern 2P at the end of the etching of the silicon substrate 1 is D3, and this D3 is the above-mentioned “specified size”. Therefore, the resist pattern 3P is formed in the resist pattern forming step (S3 to S5) so that the hole diameter of the opening portion of the hard mask pattern 2P formed in the hard mask pattern forming step S6 is D1 smaller than D3. Keep it.

  When the uneven pattern 5 is formed on the silicon substrate 1 according to such a characteristic process, the etching of the silicon substrate 1 proceeds as follows in the substrate etching process S8. Here, for convenience of explanation, the period from the start to the end of etching is divided into three periods, the first period, the middle period, and the second period. These three periods are divided, for example, by dividing the etching time into three equal parts. The etching start time is defined as the time when the introduction of the etching gas is started, and the etching end time is defined as the time when the introduction of the etching gas is stopped.

  First, in the previous period, as shown in FIG. 5A, undercut by side etching occurs under the hard mask pattern 2P as the etching of the silicon substrate 1 proceeds isotropically under conditions such as process pressure. . Further, the surface of the silicon substrate 1 is gradually recessed as the etching progresses, and the recessed shape approaches a bowing shape or a shape approximate thereto. Further, when the amount of undercut under the hard mask pattern 2P increases due to the progress of side etching of the silicon substrate 1, a difference occurs in the degree of progress of side etching in the depth direction of the pattern 5. More specifically, the intermediate depth portion of the pattern 5 deeper than the upper portion (shallow depth portion) of the pattern 5 shielded by the opening of the opening portion of the hard mask pattern 2P has more sides. Etched.

  In the middle period thereafter, as shown in FIG. 5B, the etching of the silicon substrate 1 proceeds in the depth direction, and the hard mask pattern 2P recedes at the same time. The recession of the hard mask pattern 2P proceeds mainly by the reaction between the oxygen gas added to the etching gas and the hard mask material. That is, in the present embodiment, the hard mask pattern 2P is intentionally retracted. Further, the recession of the hard mask pattern 2P occurs not only in the middle period but also in the above-described first period and the later period described later.

  As described above, when the hard mask pattern 2P recedes due to the reaction with the oxygen gas during the etching of the silicon substrate 1, the etching gas is efficiently applied to the upper portion of the pattern 5 that has been shielded by the overhang of the opening portion of the hard mask pattern 2P. Incident. Further, the upper portion of the pattern 5 is a portion where the etching gas is easily incident as compared with a deeper portion. For this reason, the etching proceeds remarkably at the upper part of the pattern 5.

  Therefore, in the later stage, as shown in FIG. 5C, the cross-sectional shape of the pattern 5 changes in the direction in which the opening dimension of the pattern 5 gradually increases as the hard mask pattern 2P further recedes. As a result, the shape of the pattern 5 finally obtained is such that the side surface of the pattern 5 is closer to the vertical surface than when etching is performed so as to suppress the recession of the hard mask pattern 2P. That is, while the silicon substrate 1 is being etched, the dent portion of the pattern 5 once approaches the bowing shape, but the shape of the pattern 5 is gradually corrected by the receding hard mask pattern 2P. Then, at the stage where the etching is finished, such a bowing shape or the like is sufficiently corrected, and the side surface of the pattern 5 becomes a shape close to a vertical surface. The “vertical surface” described in this document refers to a surface perpendicular to the main surface (surface) of the substrate.

<3. Experimental results>
The above-mentioned point is also clarified from the experimental results by the present inventor. FIGS. 6A to 6C show the shapes of the patterns obtained from the experimental results. Hereinafter, each experimental result will be described.

(Experimental result 1)
FIG. 6A shows the shape of a pattern obtained when the silicon substrate is etched without adding oxygen gas to the etching gas. In this experiment, after forming a hard mask pattern 2P by patterning a CrN (chromium nitride) metal layer, an etching time of 600 seconds and an etching gas flow rate of CF ₄ = 100 sccm (100%) and a pitch of 90 nm are formed. A pattern was formed on the silicon substrate 1. As a result, a groove pattern having a depth of about 60 nm was formed. However, the cross-sectional shape of the groove pattern was bowed due to the influence of side etching.

(Experimental result 2)
FIG. 6B shows the shape of a pattern obtained when an oxygen gas is added to the etching gas and the silicon substrate is etched. In this experiment, after patterning the CrN metal layer to form the hard mask pattern 2P, the etching time was 300 seconds, the etching gas flow rate was CF ₄ = 95 sccm, oxygen gas = 5 sccm (total flow rate was 100 sccm), and the pitch A 90 nm groove pattern was formed on the silicon substrate 1. As a result, a groove pattern having a depth of about 40 nm was formed. Further, the cross-sectional shape of the groove pattern was a shape in which the upper part of the pattern (opening side) was expanded as compared with the above “Experimental result 1”.

(Experimental result 3)
FIG. 6C shows the shape of a pattern obtained when an oxygen gas is added to the etching gas and the silicon substrate is etched. In this experiment, only the etching time was changed as compared with the above “Experimental result 2”. Specifically, the etching time was 600 seconds. As a result, a groove pattern having a depth of about 60 nm was formed. Moreover, the cross-sectional shape of the groove pattern was a shape in which the upper part of the pattern (opening side) was further expanded as compared with the above “Experimental result 2”.

  As can be seen from the above experimental results, when oxygen gas is added to the etching gas, the side surface of the pattern can be brought close to the vertical surface without forming a bow shape. More specifically, in the groove pattern shown in FIG. 6C, the groove width gradually decreases (continuously) from the top to the bottom of the pattern, and the side of the pattern is inclined accordingly. Accordingly, in the deep etching of the silicon substrate 1, there is a time when the side surface of the pattern becomes a vertical surface or a state close to this while the pattern shape is finally formed. Therefore, by setting the etching time to be shorter than 600 seconds according to the time, or by setting the process conditions so that the etching is completed in such a state, the side surface of the pattern is brought closer to the vertical surface. be able to. In this case, the process conditions to be set are not only the amount (ratio) of the oxygen gas added to the etching gas, but also include, for example, a substrate bias.

  On the other hand, when oxygen gas is not added to the etching gas, as the etching of the silicon substrate 1 proceeds, the side surface of the pattern approaches a bowing shape, and deep digging of silicon proceeds while maintaining this bowing shape. For this reason, the side surface of the pattern cannot be brought close to the vertical surface.

<4. Advantages of the embodiment>
According to the embodiment of the present invention, the following effects can be obtained.

  That is, when forming the concave / convex pattern 5 on the surface of the silicon substrate 1, after forming the hard mask pattern 2P on the silicon substrate 1, an oxygen gas that contributes to the receding of the hard mask pattern 2P is added to the etching gas. The substrate 1 is etched. For this reason, the shape of the pattern 5 can be corrected by the receding of the hard mask pattern 2P. As a result, the side surface of the pattern 5 formed on the silicon substrate 1 can be brought close to a vertical surface.

  When oxygen is added to the etching gas, a silicon oxide film is formed on the side surface of the pattern during the etching of the silicon substrate 1. This silicon oxide film functions as a sidewall protective film. For this reason, the side wall protective effect effective for suppression of side etching is obtained. Therefore, the pattern shape correction effect and the side wall protection effect described above can be obtained at the same time.

<5. Modified example>
The technical scope of the present invention is not limited to the above-described embodiments, and various modifications and improvements may be added within the scope of deriving specific effects obtained by the constituent requirements of the invention and combinations thereof. Including.

  For example, with respect to the substrate etching step S8, the gas added to the etching gas is not limited to oxygen gas, but may be any gas that contributes more to the recession of the hard mask pattern 2P than the reactive gas that contributes to the etching of silicon. Good. Specifically, a gas that satisfies the above conditions may be selected as appropriate according to the hard mask material from among gas types that do not have a negative influence on the etching of silicon.

  In the above embodiment, oxygen gas is continuously added from the start to the end of dry etching of the silicon substrate 1, but the present invention is not limited to this. For example, the addition of oxygen gas may be started at a timing later than the timing at which dry etching of the silicon substrate 1 is started. Further, the addition of oxygen gas may be stopped at a timing before the timing at which dry etching of the silicon substrate 1 is finished. Furthermore, oxygen gas may be added from a timing after the timing at which dry etching of the silicon substrate 1 is started to a timing before the timing at which the dry etching is ended (that is, only during an intermediate period). Furthermore, the amount of oxygen gas added may be changed (increase or decrease) continuously or stepwise from the start to the end of etching.

  In the above embodiment, the resist pattern removing step S7 is provided between the hard mask pattern forming step S6 and the substrate etching step S8 in the series of steps related to the substrate manufacturing method. Instead, a resist pattern removing step S7 may be provided between the substrate etching step S8 and the hard mask pattern forming step S9.

  Further, the substrate manufacturing method described in the above embodiment can be suitably applied to the case of manufacturing an imprint mold. In particular, when applied to imprint mold production, the side surface of the pattern approaches the vertical surface, which facilitates peeling of the mold from the transfer substrate. Therefore, it is possible to obtain a mold having excellent releasability.

  Furthermore, the substrate manufacturing method according to the present invention is applicable to uses other than imprint mold manufacturing. Specifically, for example, photomasks for semiconductor devices, semiconductor manufacturing, micro electro mechanical systems (MEMS), sensor elements, optical discs, optical components such as diffraction gratings and polarizing elements, nano devices, organic transistors, color filters, micro lenses It can also be applied to the production of arrays, immunoassay chips, DNA separation chips, microreactors, nanobiodevices, optical waveguides, optical filters, photonic crystals, and the like.

1 ... Substrate (silicon substrate)
2 ... Hard mask layer 2P ... Hard mask pattern 3 ... Resist layer 3P ... Resist pattern 5 ... Pattern

Claims (4)

A first step of forming a hard mask layer on the substrate;
A second step of forming a resist pattern on the substrate by patterning the resist layer after forming a resist layer in a state of covering the hard mask layer on the substrate after the first step;
After the second step, a third step of forming a hard mask pattern on the substrate by etching the hard mask layer using the resist pattern as a mask;
And a fourth step of forming an uneven pattern on the substrate by dry etching the substrate using the hard mask pattern as a mask after the third step,
In the fourth step, the hard mask pattern is retracted with the progress of the etching of the substrate by dry etching the substrate using an etching gas to which a gas contributing to the recession of the hard mask pattern is added. A substrate manufacturing method characterized. In the second step, the opening size of the hard mask pattern obtained when the hard mask layer is etched using the resist pattern as a mask in the third step is smaller than a predetermined size. Form a resist pattern,
2. The substrate manufacturing method according to claim 1, wherein, in the fourth step, the substrate is etched such that an opening dimension of the hard mask pattern becomes the specified dimension by retreat of the hard mask pattern. 3. . In the first step, a silicon substrate is used as the substrate, and the hard mask layer is formed of chromium or a chromium alloy,
3. The substrate manufacturing method according to claim 1, wherein in the fourth step, oxygen gas is added as a gas that contributes to the receding of the hard mask pattern. An imprint mold is obtained by forming an uneven pattern on the substrate by applying the substrate manufacturing method according to claim 1, 2 or 3.