JP2020197570A - Method for manufacturing resist pattern and resist film - Google Patents

Abstract

To provide a method for manufacturing a resist pattern, by which a resist pattern can be formed that is suitable for patterning a metal film formed by a PVD process by use of a lift-off method without roughening a substrate surface.SOLUTION: A method for manufacturing a resist pattern of the present invention includes: a step of forming a photosensitive resist film 1 on a surface of a substrate Sw; a step of exposing the resist film with light 3 at a predetermined wavelength in a direction orthogonal to the substrate surface; and a step of developing the exposed resist film to form a resist pattern 14 having a resist opening 15 where the substrate surface is exposed in a predetermined pattern. The substrate surface is configured to reflect light passing through the resist film; and when minimum light quantity of light, which irradiates the resist film in such a manner that a wall surface of the resist opening forming an interface between an exposed region 11 to the light and an unexposed region 12 to the light extends in an orthogonal direction with respect to the substrate surface, is defined as reference light quantity, the light quantity during exposure of the resist film is set to be within a range from 50 to 70% of the reference light quantity.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a resist pattern and a resist film, and more particularly to a method suitable for forming a metal pattern on the surface of a substrate by using a lift-off method.

For example, in the manufacturing process of a semiconductor device, there is a step of forming a metal pattern as a lead wiring on the surface of a silicon wafer (hereinafter referred to as “board”), and the so-called lift-off method has been conventionally used for forming such a metal pattern. It's being used. In this case, for example, a positive resist is applied to the surface of the substrate to form a photosensitive resist film, and light is emitted from a direction orthogonal to the surface of the substrate through a photomask arranged above the resist film (for example). The resist film is exposed by irradiating with ultraviolet light). As a result, the exposed portion of the resist film becomes the photosensitive region, and the portion of the resist film shielded by the photomask and not irradiated with light becomes the non-photosensitive region.

Next, when the exposed resist film is developed, the photosensitive region is removed, and a resist pattern having a resist opening in which the substrate surface is exposed is formed in a pattern corresponding to the photomask. After that, a metal film is formed on the entire surface of the substrate including the resist pattern, and the resist pattern is removed together with the metal film formed on the upper surface of the resist pattern with a chemical solution to form a predetermined metal pattern on the surface of the substrate.

Here, a PVD method (physical vapor deposition) such as a sputtering method or a vapor deposition method is usually used for film formation of the metal film, but a metal film is also formed on the wall surface of the resist opening, and this is the substrate surface. If it is connected to a film formed on the resist pattern, there arises a problem that the chemical solution cannot be brought into contact with the resist pattern. As one of the solutions to such a problem, it has been proposed to make the wall surface of the resist opening tapered toward the surface of the substrate (see, for example, Patent Document 1).

In the above-mentioned conventional example, when an opaque substrate such as a silicon wafer is used as the substrate, the surface of the substrate is roughened and light is diffusely reflected on the surface of the substrate when the resist film is exposed. However, this requires pretreatment on the surface of the substrate, which not only increases the number of manufacturing processes, but also causes deterioration of the performance of the semiconductor device due to roughening of the silicon wafer.

Japanese Unexamined Patent Publication No. 9-185174

Therefore, in view of the above points, the present invention is a resist pattern manufacturing method capable of forming a resist pattern suitable for patterning a metal film formed by the PVD method by the lift-off method without roughening the substrate surface. The subject is to provide a resist film and a resist film.

In order to solve the above problems, a step of forming a photosensitive resist film on the surface of the substrate, a step of irradiating light of a predetermined wavelength from a direction orthogonal to the surface of the substrate to expose the resist film, and exposure were performed. The method for producing a resist pattern of the present invention, which includes a step of developing a resist film to form a resist pattern having a resist opening whose substrate surface is exposed in a predetermined pattern, reflects light that has passed through the resist film on the substrate surface. The minimum amount of light when irradiating light so that the wall surface of the resist opening forming the interface between the photosensitive region and the non-photosensitive region extends in the direction orthogonal to the substrate surface is used as the reference light amount, and the resist is used. The light amount at the time of exposure of the film is set within the range of 50 to 70% of the reference light amount.

Here, as a result of diligent research by the inventors, when a photosensitive resist film generally used for this kind of application is irradiated with light having a predetermined wavelength (for example, ultraviolet light having a wavelength of 365 nm), the amount of light is increased. When a certain threshold is exceeded, the part of the resist film that exceeds this threshold is exposed to light and becomes a photosensitive area, while the part of the resist film that is irradiated with light but the amount of light does not reach a certain threshold is incompletely exposed. It has become a region, and it has been found that this incompletely photosensitive region is not removed in the subsequent development as well as the non-photosensitive region of the resist film which is shielded by a photomask and is not irradiated with light at the time of exposure.

Based on the above findings, in the present invention, it was decided to adopt a configuration in which the amount of light at the time of exposure is set within the range of 50 to 70% of the reference amount of light. According to this, when light of a predetermined wavelength is irradiated through a photomask from a direction orthogonal to the substrate surface, for example, in the portion of the resist film where the light is not shielded by the photomask, from the surface of the resist film to the first depth. In the meantime, when the amount of light exceeds a certain threshold, it becomes a photosensitive region having a width equivalent to the opening width of the photomask (in other words, the interface between the photosensitive region and the non-photosensitive region is relative to the substrate surface. Extends downward in the direction orthogonal to each other).

Then, when the depth exceeds the first depth, an incompletely photosensitive region is formed at a position immediately below the inner edge of the opening of the photomask, and this incompletely photosensitive region increases in depth from the surface of the resist film. , It becomes larger so as to expand inward (in other words, the interface between the photosensitive region and the incompletely photosensitive region expands while shrinking like a spindle). It is considered that this is because the amount of light at the time of exposure is set to be less than the reference amount of light, and the light that has entered the resist film is attenuated and scattered when it exceeds the first depth.

Further, when the depth exceeds the second depth, which is deeper than the first depth, the incomplete photosensitive region becomes smaller so as to shrink outward, and reaches the substrate surface (in other words, is not the photosensitive region). The interface with the completely photosensitive area extends while swelling like a spindle). It is considered that this is because the light that has passed through the resist film is reflected on the surface of the substrate, and the reflected light is added to increase the amount of light, so that the incompletely photosensitive region becomes smaller.

When the resist film exposed as described above is developed, the cross-sectional shape of the wall surface of the resist opening is a vertical plane between the surface of the resist film and the first depth, and the first depth to the second depth. The gradually narrowing first curved surface between them and the gradually wider second curved surface between the second depth and the surface of the substrate are continuous. As a result, when the resist pattern is applied when forming a metal pattern by the lift-off method, when a metal film is formed on the substrate surface by the PVD method, the boundary between the first curved surface and the second curved surface causes The metal film formed on the surface of the substrate and the metal film formed on the wall surface of the resist opening can be trimmed, and the chemical solution can be brought into contact with the resist pattern. If the amount of light during exposure is more than 70% of the reference amount of light, the desired incomplete photosensitive region may not be formed, while if the amount of light during exposure is less than 50% of the reference amount of light, light is emitted to the substrate surface. It may not be possible to make it transparent.

In the present invention, when the wavelength of the light is in the range of 200 nm to 400 nm, it is preferable to set the thickness of the resist film to 50 times or more the wavelength of the light. If it is less than 50 times, the desired incomplete photosensitive region may not be formed.

Further, in the present invention, it is preferable to set the aspect ratio of the resist pattern to 1 or more. If the aspect ratio is less than 1, the desired incompletely photosensitive region may not be formed.

Further, in order to solve the above problems, in the resist film of the present invention in which a resist opening is formed on one surface of the substrate in a predetermined pattern, the cross-sectional shape of the resist opening is the first depth from the surface of the resist film. The vertical plane between the two, the gradually narrower first curved surface between the first depth and the second depth, and the gradually wider second curved surface between the second depth and the substrate surface. It is characterized by being continuous.

The schematic cross-sectional view which shows the resist pattern manufacturing method of embodiment of this invention. The schematic cross-sectional view which shows the resist pattern manufacturing method of embodiment of this invention. (A) and (b) are schematic cross-sectional views showing a metal pattern forming method using the resist pattern shown in FIG.

Hereinafter, referring to the drawings, the substrate is a silicon wafer (hereinafter referred to as “substrate Sw”), a resist pattern is formed (manufactured) on the surface of the substrate Sw, and a metal pattern is formed on the surface of the substrate Sw by a lift method using this resist pattern. The embodiment of the resist pattern manufacturing method of the present invention will be described by taking the case of forming the above.

With reference to FIG. 1, a positive resist is applied to the surface of the substrate Sw to form a photosensitive resist film 1 having a predetermined thickness d. The thickness d of the resist film 1 is set to be 50 times or more the wavelength of light described later. If it is less than 50 times, the present inventors presume that it is a problem of diffraction, but there is a problem that the incompletely photosensitive region 13 as described later cannot be formed. In the following, the surface side of the substrate Sw will be described as the top.

Next, the photomask 2 is placed above the resist film 1. As the photomask 2, for example, a known photomask in which a chromium film 22 as a light-shielding film is patterned on the lower surface of a transparent substrate 21 such as a glass substrate or a quartz substrate can be used. Then, the upper surface of the resist film 1 is exposed by irradiating the light 3 having a predetermined wavelength through the photomask 2. At this time, light 3 is irradiated from a direction orthogonal to the surface of the substrate Sw (the light parallelism is preferably collimation half-width ≤ 1.5 ° and declination angle ≤ 1.0 °), and the resist film. A photosensitive region 11 and a non-photosensitive region 12 are formed in 1. As the light 3 to be irradiated at the time of exposure, UV light having a wavelength in the range of 200 nm to 400 nm can be used, and specifically, i-line having a wavelength of 365 nm can be exemplified.

Here, in the above-mentioned conventional example, light 3 is irradiated so that the interface between the photosensitive region 11 and the non-photosensitive region 12 (the wall surface of the resist opening 15 described later) extends in the direction orthogonal to the surface of the substrate Sw during exposure. Orthogonal. Assuming that the minimum amount of light when irradiating light 3 is used as the reference light amount, the present inventors have come to find out the following through diligent research. That is, when the amount of light applied to the resist film 1 exceeds a certain threshold value, the portion of the resist film 1 becomes the photosensitive region 11, while the light 3 is irradiated, but the amount of light does not reach a certain threshold value. The portion 1 is the incompletely photosensitive region 13. The incompletely photosensitive region 13 is not removed by the developing solution in the subsequent development, like the non-photosensitive region 12 of the resist film 1 which is shielded by the photomask 2 and is not irradiated with light during exposure. Regarding the minimum amount of light, that is, the reference amount of light, for example, whether or not the vertical surface 15a reaches the surface of the substrate Sw by irradiation with light 3 (or whether or not the incompletely exposed region 13 is formed) is used as an index. It is good to experimentally determine the minimum amount of light, but it may be derived by calculating the irradiation energy using the standard exposure amount and film thickness of the resist.

Based on the above findings, in the present embodiment, it is decided to adopt a configuration in which the amount of light at the time of exposure is set within the range of 50 to 70% of the reference amount of light. As a result, in the portion of the resist film 1 that is not shielded by the photomask 2 (the light-shielding film 22), r1 from the surface of the resist film 1 to the first depth h1 exceeds a certain threshold value, so that the photo The photosensitive region 11 has a width w2 equivalent to the opening width w1 of the mask 2. In other words, the interface between the photosensitive region 11 and the non-photosensitive region 12 extends downward in a direction orthogonal to the surface of the substrate Sw. When the first depth h1 is exceeded, an incompletely photosensitive region 13 is formed at a position directly below the inner edge 22a of the opening of the photomask 2, and the incompletely photosensitive region 13 is formed from the surface of the resist film 1. As the depth increases, it grows inwardly. In other words, the interface between the photosensitive region 11 and the incomplete photosensitive region 13 expands while shrinking like a spindle. It is considered that this is because the light amount at the time of exposure is set to be smaller than the reference light amount, and the light that has entered the resist film 1 is attenuated and scattered when it exceeds the first depth h1. Then, when the second depth h2, which is deeper than the first depth h1, is exceeded (that is, the portion indicated by r3 in the figure), the incompletely photosensitive region 13 contracts outward, contrary to the above. It becomes smaller and reaches the surface of the substrate Sw. In other words, the interface between the photosensitive region 11 and the incomplete photosensitive region 13 extends while expanding like a spindle. It is considered that this is because the light that has passed through the resist film 1 is reflected on the surface of the substrate Sw, and the reflected light is added to increase the amount of light, so that the incompletely photosensitive region 13 becomes smaller.

When the resist film 1 exposed in this way is developed, the photosensitive region 11 is dissolved in the developing solution and removed, while the incompletely photosensitive region 13 remains undissolved in the developing solution together with the non-sensitive region 12. The resist pattern 14 (resist film 1 having a patterned resist opening 15) shown in FIG. 2 is formed (manufactured). The cross-sectional shape of the wall surface of the resist opening 15 has a gradual width of the vertical surface 15a of r1 from the surface of the resist film 1 to the first depth h1 and r2 from the first depth h1 to the second depth h2. The narrow first curved surface 15b and the gradually wider second curved surface 15c of r3 from the second depth h2 to the surface of the substrate Sw are continuous, and the first curved surface 15b and the second curved surface 15c are formed. A sharp boundary portion 15d is formed between the two. Here, the aspect ratio of the resist pattern 14 (= height d / width w2 of the resist opening 15) is preferably set to 1 or more. If the aspect ratio is less than 1, there is a possibility that the incompletely photosensitive region 13 having the boundary portion 15d cannot be formed. By setting the width w2 of the resist opening 15 to, for example, the range of 50 to 500 μm, an incompletely photosensitive region 13 having a high lift-off effect can be formed.

Next, a metal film 16 is formed on the surface of the substrate Sw including the surface of the resist pattern 14 by the PVD method. Since a known sputtering method can be used as the PVD method, further description including film forming conditions will be omitted. When the metal film 16 is formed by the sputtering method, a metal target (not shown) is sputtered, and sputtered particles scattered from the target are attached and deposited to form a film. As shown in FIG. 3A, the sputtered particles Ps include those that are obliquely incident on the surface of the substrate Sw, but the boundary portion 15d between the first curved surface 15b and the second curved surface 15c. As a result, the metal film 16a formed on the surface of the substrate Sw and the metal film 16b formed on the wall surface of the resist opening 15 are edge-cut (that is, a metal film is formed on the surface of the second curved surface 15c). Not done). Therefore, the chemical solution for stripping the resist can be brought into contact with the resist pattern 14, and by removing the resist pattern 14 with the chemical solution, the metal film 16b formed on the surface of the resist pattern 14 is removed (lifted off). , A metal film 16a remains as a metal pattern on the surface of the substrate Sw (see FIG. 3B).

According to the above, a resist pattern 14 suitable for patterning the metal film 16 formed by the PVD method by the lift-off method can be formed on the surface of the substrate Sw. Moreover, since the surface of the substrate Sw is not roughened as in the conventional example, pretreatment on the surface of the substrate Sw is unnecessary, and the performance of the semiconductor device is not deteriorated.

Although the embodiments of the present invention have been described above, various modifications can be made as long as they do not deviate from the scope of the technical idea of the present invention. In the above embodiment, the resist film 1 is formed by applying a positive resist, but the present invention can also be applied when a negative resist is applied to form a resist film.

In the above embodiment, the case where the metal film 16 is formed by the sputtering method has been described as an example, but as the film forming method of the metal film 16, another PVD method such as the vapor deposition method can be used. Also in this case, since the metal film 16b is also formed on the wall surface of the resist opening 15, the resist pattern 14 formed in the present invention can be applied.

Sw ... substrate, 1 ... resist film, 11 ... photosensitive region, 12 ... non-photosensitive region, 13 ... incompletely photosensitive region, 14 ... resist pattern, 15 ... resist opening, 3 ... light.

Claims (4)

The process of forming a photosensitive resist film on the substrate surface and
The process of exposing the resist film by irradiating light of a predetermined wavelength from a direction orthogonal to the substrate surface, and
In a method for manufacturing a resist pattern, which comprises a step of developing an exposed resist film to form a resist pattern having a resist opening whose substrate surface is exposed in a predetermined pattern.
The surface of the substrate is configured to reflect the light that has passed through the resist film.
The minimum amount of light when irradiating light so that the wall surface of the resist opening forming the interface between the photosensitive area and the non-photosensitive area extends in the direction orthogonal to the substrate surface is used as the reference light amount, and the amount of light when the resist film is exposed. Is set within the range of 50 to 70% of the reference light amount, which is a method for producing a resist pattern. The method for producing a resist pattern according to claim 1, wherein the wavelength of the light is in the range of 200 nm to 400 nm.
A method for producing a resist pattern, which comprises setting the thickness of the resist film to 50 times or more the wavelength of the light. The method for producing a resist pattern according to claim 1 or 2, wherein the aspect ratio of the resist pattern is set to 1 or more. In a resist film in which resist openings are formed in a predetermined pattern on one surface of a substrate.
The cross-sectional shape of the resist opening has a vertical plane between the surface of the resist film and the first depth, a gradually narrowing first curved plane between the first depth and the second depth, and a second depth. A resist film characterized in that a gradually wide second curved surface is continuous from the surface to the surface of the substrate.

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