JP2007206096A - Pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent etching residue due to a remaining resist, when a step-like pattern with two or more steps is formed by dry etching. <P>SOLUTION: The method includes a first process of forming a structure, including a one-step pattern by first dry etching, a second process of coating the surface of the formed structure with a resist layer 102, a third process of irradiating the resist layer 102 with light-transmitting a photomask 200 and developing to pattern the resist layer 102, and a fourth process of carrying out second dry etching by using the patterned resist layer 102 as an etching mask to form a structure having a two-step pattern. The photomask 200 has two or more areas having different transmittances for light, wherein in a portion to form the second step pattern, the transmittance of an area where light to irradiate a face parallel to the propagation direction of the light transmits is larger than that of the area where the light that is irradiated on areas other than this penetrates. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pattern forming method by dry etching.

  In the fields of semiconductors, liquid crystal display devices, electro-optical devices, MEMS (Micro Electro Mechanical System), and the like, a structure having two or more steps is often formed at a desired position. In such a case, fine processing can be performed with high accuracy by using dry etching, particularly a deep etching technique such as a Bosch process.

  When a step shape of two or more steps is formed on a silicon substrate or the like by dry etching, a series of steps of resist coating, exposure / development, and dry etching are repeated twice or more. In the second and subsequent steps, it is necessary to apply a resist to the step-shaped surface formed by the first dry etching and pattern the resist layer by exposure and development.

  However, when exposing the stepped portion, the side wall portion of the step is not easily exposed to light, so that the resist is not sufficiently exposed, and the resist remains even after development. When dry etching is performed in this state, silicon or silicon that has reacted with the organic component of the resist remains along the resist remaining on the side wall portion, and etching residue (burrs, crown fence) occurs.

  In order to suppress the occurrence of etching residue, there is a method in which the resist on the side wall portion of the step is exposed and developed with a larger exposure amount than usual. However, in order to sufficiently expose the resist on the side wall portion, a very large exposure amount is necessary. If the same exposure amount is applied to a plane portion other than the side wall portion, the exposure amount becomes excessive, and patterning is not performed. The accuracy may deteriorate.

JP-A-2005-67216

  An object of the present invention is to prevent etching residue due to residual resist when a step shape of two or more steps is formed by dry etching.

  The pattern forming method of the present invention is a pattern forming method for forming a structure including at least two or more step shapes on a substrate, wherein the structure includes a one step step shape by performing a first dry etching. A first step of forming a film, a second step of covering the surface of the structure formed in the first step with a resist layer, and irradiating the resist layer with light transmitted through a photomask and developing Thus, a third step of patterning the resist layer and a second dry etching using the resist layer patterned in the third step as an etching mask to form a structure including a two-step shape A fourth step, wherein the photomask has two or more regions having different transmittances, and illuminates a surface parallel to the light traveling direction in a portion forming a second stepped shape. Transmission regions through which light is transmitted is is larger than the transmittance of the region where light is irradiated to the other portions transmits.

  As a result, it becomes possible to prevent unnecessary resist from remaining due to insufficient exposure of light-irradiated portions such as side walls formed by the first dry etching, thereby preventing etching residue due to resist residues. can do.

The photomask has a region where the light transmittance is a value between 0% and 100%.
In addition, the photomask is preferably formed so that a transmittance of a region through which light irradiated to a surface parallel to the light traveling direction is 100%.
As a result, the exposure time and the amount of light can be determined according to the depth at which the resist layer such as the side wall portion is removed, and the exposure amount of other portions can be adjusted by the transmittance.
The photomask may be a gray scale photomask, for example.

The dry etching can be performed by, for example, a Bosch process.
The pattern forming method of the present invention can be applied to the case where a structure having two or more steps is formed at a desired position in the field of MEMS and semiconductors, including the manufacture of an ink jet printer head.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a pattern forming method according to Embodiment 1 of the present invention. Here, a structure having two or more steps is formed on a silicon substrate by dry etching.

  First, the first dry etching is performed to form a step shape as shown in FIG. The dry etching can be performed using, for example, a parallel plate type etching apparatus or an inductive coupling type etching apparatus. As a desirable method, a Bosch process or the like can be given.

  Next, as shown in FIG. 1B, a photoresist is applied to the surface of the silicon substrate 101 on which the step shape is formed, so that a resist layer 102 is formed.

Next, as illustrated in FIG. 1C, the resist layer 102 is irradiated with ultraviolet rays through a photomask 200.
As shown in the figure, the photomask 200 is formed of, for example, a glass plate or the like and has regions a, b, and c. The region a has an ultraviolet transmittance of 100%, the region b has an ultraviolet transmittance of 50%, and the region c has an ultraviolet transmittance of 0%.
As the photomask 200, a material whose transmittance is adjusted by an area opening method or a HEBS (High Energy Beam Sensitive) grayscale mask using Ag ion doping can be used. Note that the type and transmittance values of the photomask 200 are not limited to those described above.

  As shown in FIG. 1C, a step-shaped side wall portion (the portion indicated by X in the figure) formed by the first etching among the portions forming the second step shape on the silicon substrate 101 The ultraviolet rays that pass through the region a are irradiated. Of the portion forming the second stepped shape, the portion other than the portion indicated by X, that is, the portion facing the ultraviolet irradiation surface is irradiated with the ultraviolet rays passing through the region b. The portion where the step shape is not formed (the portion where the second etching is not performed) is covered with the region c of the photomask 200 and is not exposed.

  Since the side wall portion indicated by X in the figure is parallel to the optical path of the irradiated ultraviolet light, it is difficult for light to strike. If the exposure time and light quantity of ultraviolet rays are determined in accordance with the depth (X depth) at which the resist layer 102 is removed from the side wall portion, the exposure amount is excessive in other portions, and the patterning accuracy is deteriorated. Therefore, by adjusting the exposure amount of other portions by the photomask 200, an appropriate exposure amount can be given to all portions.

Next, as shown in FIG. 1D, development is performed to pattern the resist layer 102.
Next, as shown in FIG. 1E, a second dry etching is performed using the patterned resist layer 102 as an etching mask to form a structure including a two-step shape.
Dry etching can be performed in the same manner as the first time.

  After the dry etching is completed, the remaining resist layer 102 is removed to obtain a structure including a two-step shape as shown in FIG.

FIG. 2 is a diagram for explaining a pattern forming method according to a comparative example. The states shown in FIGS. 2A to 2D correspond to FIGS. 1C to 1F.
As shown in FIG. 2A, in the comparative example, the photomask 300 used in the exposure of the resist layer 102 includes only a region a having an ultraviolet transmittance of 100% and a region c having an ultraviolet transmittance of 0%. Have.

  As shown in FIG. 1A, all the portions forming the second step shape on the silicon substrate 101 are irradiated with ultraviolet rays that pass through the region a. The portion where the step shape is not formed (the portion where the second etching is not performed) is covered with the region c of the photomask 200 and is not exposed.

As described above, the side wall portion indicated by X in the drawing is parallel to the optical path of the irradiated ultraviolet light, so that it is difficult for light to strike. Therefore, if the portion other than X is exposed under appropriate conditions, the exposure of the X portion becomes insufficient.
Therefore, as shown in FIG. 2B, when the development is performed, the X portion of the resist layer 102 remains.

When dry etching is performed a second time using the patterned resist layer 102 as shown in FIG. 2B as an etching mask, silicon in the X portion remains without being etched, as shown in FIG.
Therefore, when the resist layer 102 is removed, an etching residue is generated in the structure as shown in FIG.

  As described above, according to the pattern forming method according to the first embodiment of the present invention, it is possible to sufficiently expose a portion that is difficult to be exposed to light, such as a side wall portion formed by the first dry etching. It is possible to prevent the etching residue from occurring due to the remaining.

FIG. 1 is a diagram for explaining a pattern forming method according to the first embodiment. FIG. 2 is a diagram for explaining a pattern forming method according to a comparative example.

Explanation of symbols

101 silicon substrate, 102 resist layer, 200,300 photomask

Claims (5)

A pattern forming method for forming a structure including a step shape of at least two steps on a substrate,
A first step of performing a first dry etching to form a structure including a one-step step shape;
A second step of covering the surface of the structure formed in the first step with a resist layer;
Irradiating the resist layer with light transmitted through a photomask and developing the resist layer to pattern the resist layer; and
A fourth step of performing a second dry etching using the resist layer patterned in the third step as an etching mask to form a structure including a two-step shape;
The photomask has two or more regions having different light transmittances and transmits light irradiated to a surface parallel to the light traveling direction in a portion forming a second stepped shape. The pattern forming method, wherein the transmittance of the region is larger than the transmittance of the region through which the light irradiated to the other part is transmitted.   The pattern forming method according to claim 1, wherein the photomask has a region having a light transmittance between 0% and 100%.   3. The pattern forming method according to claim 1, wherein the photomask has a transmittance of a region through which light irradiated to a surface parallel to the light traveling direction is 100%. 4.   4. The pattern forming method according to claim 1, wherein the photomask is a gray scale photomask. 5. The pattern forming method according to claim 1, wherein the dry etching is performed by a Bosch process.

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