JP2007214232A - Method for forming pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately coat the upper section of a substrate with an irregular shape with a resist by a simple method. <P>SOLUTION: A method for forming a pattern has a first process for forming a resist layer by coating the surface of the substrate 101 with the irregular shape with the resist, and a second process for conducting a patterning by exposing and developing the resist layers 103 and 104. The method further has a third process for conducting a second dry etching while using the resist layers patterned by the second process as etching masks. The first process has a first resist coating process and a second resist coating process, and the fluidity of the coated resist differs in the first resist coating process and the second resist coating process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  In fields such as semiconductors and MEMS (Micro Electro Mechanical System), dry etching techniques are used to perform fine processing with high accuracy. In such fine processing, a structure having two or more steps is often formed at a desired position.

  When forming a step shape of two or more steps on a silicon substrate or the like by dry etching, a series of steps of resist coating, exposure / development, and dry etching must be repeated twice or more. In the second and subsequent steps, a resist is applied to the stepped surface formed by the first dry etching, and the resist layer is patterned by exposure and development.

However, when a resist layer is formed on a step-shaped surface, it is difficult to apply the resist appropriately on the top surface of the step, the bottom of the step, and the side wall of the step. For example, when a resist is applied using a spray coating method, application to the surface of the top of the step is easy, but application to the bottom of the step is difficult.
If the thickness of the resist layer is too thin, it is not sufficient as a protective film at the time of etching, and if the thickness of the resist layer is too thick, it takes a long time to remove the resist.

JP-A-2005-67216

  Therefore, an object of the present invention is to apply a resist with high accuracy by a simple method on a substrate including an uneven shape.

The pattern forming method of the present invention is a pattern forming method for forming a structure by etching on a substrate including a concavo-convex shape, and includes a first step of forming a resist layer by applying a resist to the surface of the substrate. A second step of patterning by exposing and developing the resist layer, and a third step of performing a second dry etching using the resist layer patterned in the second step as an etching mask, The first step includes a first resist coating step and a second resist coating step, and the first resist coating step and the second resist coating step are different in resist fluidity.
Thereby, it is possible to apply the resist appropriately to any of the recessed portion, the surface portion, and the sidewall portion of the substrate including the concavo-convex shape by a simple method.

The fluidity of the resist can be changed by, for example, the viscosity of the resist to be applied. Specifically, it can be adjusted by the dilution of the resist.
Further, the fluidity of the resist may be changed depending on the degree of heat drying at the time of applying the resist.
In addition, when applying a resist by a spin coating method, the fluidity of the resist may be changed depending on the rotation speed of the substrate when the resist is applied.
When resist application is performed by an electrostatic application method, the fluidity of the resist may be changed depending on the strength of the voltage applied when applying the resist.

  In addition, the first step can be performed under reduced pressure conditions to improve the ease of attaching the resist to the substrate surface.

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, as shown in FIG. 1A, an etching mask is formed by forming a resist layer on the silicon substrate 101 and patterning it.
Next, first dry etching is performed to form a step shape as shown in FIG. For dry etching, a technique such as a silicon high-speed etching method or a Bosch process can be used. Next, the etching mask is removed as shown in FIG.

  Next, in order to form the second step by dry etching, a photoresist is applied to the surface of the silicon substrate 101 to form a resist layer 103. Here, the resist layer is formed in two stages. In the first resist coating process (first resist coating process), as shown in FIG. 1D, a resist is coated mainly on the bottom of the step of the silicon substrate 101. In order to apply the resist to the bottom of the step, it is necessary to improve the fluidity of the resist so that the resist spreads over the recessed portions.

  Next, a second resist coating process (second resist coating process) is performed, and a resist layer 104 is further formed on the resist layer 103. In the second resist coating process, as shown in FIG. 1 (E), the resist is compared with the first coating process so that a uniform resist film is formed on the top surface of the step, the bottom of the step, and the side wall of the step. Reduce fluidity.

For example, in the case of applying a resist using a spray coating method, the resist is diluted in the first application process to lower the viscosity and increase the fluidity of the resist. Further, in the spray coating method, coating may be performed while performing heat drying, but heat drying may not be performed in the first coating step.
On the other hand, in the second application process, the resist is made higher in viscosity than in the first application and applied while heating and drying so that the resist is easily applied to the upper surface of the step of the silicon substrate 101.

When applying a resist using a spin coater, the resist is diluted in the first application step to lower the viscosity and improve the fluidity of the resist. Also, the rotation speed is reduced so that the resist can easily reach the bottom of the step.
On the other hand, in the second coating process, the viscosity of the resist is made higher than that in the first time, and the rotation speed is increased so that the resist can be coated on the upper surface of the step.

In the case of using the electrostatic coating method, the bias voltage to be applied is increased in the first coating process so that the resist can easily move in the vertical direction, and the resist can easily reach the bottom of the step.
On the other hand, in the second application step, the bias voltage is made lower than in the first time so that the resist is easily applied not only to the bottom of the step, but also to the surface and the side wall of the step.

  Moreover, even when any of the above methods is used, the ease of attaching the resist can be improved by applying the resist under reduced pressure.

  Note that the order of applying the resist with higher fluidity and applying with lower fluidity may be reversed. Further, the resist coating process may be performed in three or more times.

After the resist layers 103 and 104 are formed, exposure and development are performed to pattern the resist layer.
Next, a second dry etching is performed using the patterned resist layer 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 is removed to obtain a structure including a two-step shape.

2 and 3 are diagrams for explaining a pattern forming method according to a comparative example.
The comparative example shown in FIG. 2 shows a case where a resist layer is formed on the step-shaped surface shown in FIG.
As shown in the figure, in this case, a lot of resist is applied to the upper surface of the step, and the resist does not reach the bottom of the step sufficiently.

Further, the comparative example shown in FIG. 3 shows a case where a resist layer is formed on the step-shaped surface shown in FIG.
As shown in the figure, in this case, the resist is applied only to the upper surface of the step and the bottom of the step, and the resist is not applied to the upper portion of the side wall portion.

  As described above, according to the pattern forming method of the present invention, when a resist layer is formed on a substrate having a step shape, the resist layer is formed on the surface of the top of the step, the bottom of the step, and the side wall of the step by a simple method. A resist can be applied to the substrate.

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. FIG. 3 is a diagram for explaining a pattern forming method according to a comparative example.

Explanation of symbols

101 silicon substrate, 102, 103, 104 resist layer

Claims (6)

A pattern forming method for forming a structure by etching on a substrate including an uneven shape,
A first step of applying a resist to the surface of the substrate to form a resist layer;
A second step of patterning by exposing and developing the resist layer;
A third step of performing a second dry etching using the resist layer patterned in the second step as an etching mask;
The first step includes a first resist coating step and a second resist coating step, wherein the first resist coating step and the second resist coating step have different resist fluidity. Pattern forming method.   The pattern forming method according to claim 1, wherein the fluidity of the resist is changed depending on the viscosity of the resist to be applied.   The pattern forming method according to claim 1, wherein the fluidity of the resist is changed depending on a degree of heat drying when the resist is applied.   The pattern forming method according to claim 1, wherein the fluidity of the resist is changed according to a rotation speed of the substrate when the resist is applied.   The pattern forming method according to claim 1, wherein the fluidity of the resist is changed according to the strength of a voltage applied when the resist is applied. The pattern forming method according to claim 1, wherein the first step is performed under a reduced pressure condition.

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