KR20020056018A - method for forming contact hole of semiconductor device - Google Patents

Abstract

PURPOSE: A method for fabricating a contact hole of a semiconductor device is provided to form a contact hole for designing a mask while being not affected by an optical proximity effect, by patterning photoresist while using a periodical line/space pattern and twice performing a photolithography process. CONSTITUTION: An insulation layer is formed on a semiconductor substrate(21). The first photoresist(22) is applied on the insulation layer. The first photoresist is patterned in the first direction by using the first mask in which a line/space pattern is defined. The second photoresist(23) is applied on the entire surface of the semiconductor substrate including the patterned first photoresist. The second photoresist is patterned in the second direction vertical to the first direction by using the second mask in which a line/space pattern is vertically defined with respect to the line/space pattern of the first mask. The insulation layer is selectively eliminated to form a contact hole by using the patterned first and second photoresist.

Description

Method for forming contact hole of semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for forming contact holes in a semiconductor device suitable for improving process margins.

In general, it is well known that various patterns of semiconductor devices are formed by lithography technology.

The lithography technique forms a photoresist whose solubility is changed by irradiation with light such as X-rays or ultraviolet rays on a film, such as an insulating film or a conductive film on a semiconductor substrate, to which a pattern is to be formed. Exposing the portion to light rays and then removing the portion having high solubility by development to form a photoresist pattern; and removing the exposed portion of the film to be formed by etching to form various patterns such as wiring and electrodes. It consists of steps.

On the other hand, most of the patterns used to fabricate semiconductor devices are rectangular, which causes problems, particularly in the corner regions, when transferring these straight patterns onto the wafer. For example, upon exposure, the photoresist receives and integrates energy from all peripheral regions.

This means that the exposure dose in one vicinity of the wafer is affected by the exposure dose in neighboring neighborhoods. This phenomenon is called the optical promixity effect, which is known to be caused by optical diffraction in the projection system. Optical diffraction causes adjacent patterns to interact with each other, resulting in variations with pattern dependency.

The optical proximity effect is not severe in periodic grain type patterns such as line / space (hereinafter referred to as L / S) patterns, but in island patterns such as active, contact holes, and storage nodes in capacitors. It causes serious problems that cause deterioration of the properties.

That is, since there are no neighboring regions in the corner regions of these island patterns, the exposure dose at the corner region is always smaller than the exposure dose reaching the body or extended side of the pattern.

As a result, the corner areas of the developed pattern become somewhat rounded. In low-density semiconductor devices with large device shapes, the effect of rounding corners on device characteristics is negligible, but in ultra-high density semiconductor devices in which the shape of the device becomes smaller than sub-micron, This circularization seriously affects circuit operation.

On the other hand, in proportion to the size of the device is smaller, the size of the contact hole is smaller, the size of the lithography process has reached the limit.

In general, the size of the contact hole is about 1.27 times the line width of the gate line (in the case of logic devices), but since it is a two-dimensional structure, the resolution is more difficult than the L / S pattern such as the one-dimensional gate pattern, and the linearity of the contact size (contact on the mask) The ratio of the size change to the contact size change on the wafer is poor, resulting in poor CD (Critical Dimension) uniformity.

Therefore, in order to form a fine contact hole, a method of reducing contact size using a method of forming a large contact hole and then reflowing the photoresist by heat treatment is used.

Hereinafter, a method for forming a contact hole in a conventional semiconductor device will be described with reference to the accompanying drawings.

1A to 1B are cross-sectional views illustrating a method of forming a contact hole in a conventional semiconductor device.

As shown in FIG. 1A, an insulating film (not shown) is formed on the semiconductor substrate 11, and the photoresist 12 is coated on the insulating film by spin-coating.

Here, in order to improve adhesion between the semiconductor substrate 11 or the insulating film to be patterned and the photoresist before applying the photoresist 12, a surface treatment process using HMDS (Hexamethyldisilazane) may be performed.

Subsequently, a soft-bake process is performed on the entire surface of the semiconductor substrate 11 to which the photoresist 12 is applied.

Wherein the softening process reduces the solvent level in the photoresist 12, improves the adhesion of the photoresist 12, and stress caused by shear forces occurring during the spin-coating process. Serves to mitigate

Then, the photoresist 12 is selectively exposed by a stepper using a mask in which an L / S pattern is defined.

Subsequently, when the exposed portion of the photoresist 12 is removed by a developing process, the photoresist 12 is patterned in an L / S pattern.

13 which is not described here is a region where a contact hole is to be formed, and the rest is covered by the photoresist 12.

As illustrated in FIG. 1B, the contact hole 14 is formed by etching the insulating layer using an anisotropic etching process using the patterned photoresist 12 as an etching mask.

However, the above-described conventional method for forming a contact hole in a semiconductor device has the following problems.

That is, it is difficult to obtain the uniformity of the line width due to the change in size depending on the environment of the contact hole, and the pitch of the contact cannot be basically changed, and thus, it is not helpful to form the fine contact hole due to the scaling of the device.

Disclosure of Invention The present invention has been made in view of the above-mentioned problems. It is an object of the present invention to provide a method for forming a contact hole in a semiconductor device to improve line width uniformity and to form fine contact holes.

1A through 1B are cross-sectional views illustrating a method of forming a contact hole in a conventional semiconductor device.

2A through 2D are cross-sectional views illustrating a method of forming a contact hole in a semiconductor device according to the present invention.

3A is a plan view showing a first mask and a second mask for exposing the first and second photoresists of the present invention.

3B is a cross-sectional view taken along the line II-II of FIG. 3A.

4A to 4C are cross-sectional views showing examples of polarization processing of the first and second masks.

Explanation of symbols for the main parts of the drawings

21 semiconductor substrate 22 first photoresist

23: second photoresist 24: contact region

25: contact hole

In order to achieve the above object, a method of forming a contact hole in a semiconductor device according to the present invention includes forming an insulating film on a semiconductor substrate, applying a first photoresist on the insulating film, and a line / space (L). / S) patterning the first photoresist in a first direction using a first mask having a pattern defined thereon, and coating a second photoresist on the entire surface of the semiconductor substrate including the patterned first photoresist And the second photoresist in the first direction using a second mask in which a line / space (L / S) pattern is defined perpendicular to the line / space (L / S) pattern of the first mask. Patterning in a second direction perpendicular to the pattern; and selectively removing the insulating layer using the patterned first and second photoresist to form a contact hole It characterized by forming, including.

Hereinafter, a method of forming a contact hole in a semiconductor device according to the present invention will be described in detail with reference to the accompanying drawings.

2A to 2D are process plan views illustrating a method of forming a contact hole in a semiconductor device according to the present invention.

As shown in FIG. 2A, an insulating film (not shown) is formed on the semiconductor substrate 21, and the first photoresist 22 is coated on the insulating film by spin-coating.

Here, in order to improve adhesion between the semiconductor substrate 21 or the insulating film to be patterned and the photoresist before applying the first photoresist 22, for example, a surface treatment process using Hexamethyldisilazane (HMDS) may be performed. have.

Subsequently, a soft-bake process is performed on the entire surface of the semiconductor substrate 21 on which the first photoresist 22 is applied.

Wherein the softening process reduces the solvent level in the first photoresist 22, improves the adhesion of the first photoresist 22, and reduces the shear force generated during the spin-coating process. It acts to relieve stress caused by it.

Then, the first photoresist 22 is selectively exposed by a stepper using a first mask in which an L / S pattern is defined.

Subsequently, when the exposed portion of the first photoresist 22 is removed by a developing process, the first photoresist 22 is patterned in an L / S pattern.

As shown in FIG. 2B, the patterned first photoresist 22 is UV treated or cured. As such, when the first photoresist 22 is UV-cured or cured, the first photoresist 22 is not removed during the subsequent development process.

Subsequently, after applying the second photoresist 23 to the entire surface of the semiconductor substrate 21 including the first photoresist 22, a softening step is performed.

Wherein the softening process reduces solvent levels in the second photoresist 23, improves adhesion of the second photoresist 23, and relieves stress caused by shear forces generated during the spin-coating process. Play a role.

As shown in FIG. 2C, the second photoresist 23 is exposed using a second mask in which an L / S pattern is defined perpendicular to the L / S pattern of the first mask.

In this case, the second mask may use the same mask as the first mask used when patterning the first photoresist 22. In this case, the first mask is rotated 90 ° to obtain a second mask in which the L / S pattern is defined perpendicular to the L / S pattern of the first photoresist 22, and then the second mask is formed using the second photoresist ( 23) is exposed.

On the other hand, the exposed region of the second photoresist 23 is not affected by the optical proximity effect by the first photoresist 22 of the adjacent L / S pattern.

Subsequently, the exposed portion of the second photoresist 23 is removed by a developing process. At this time, the first photoresist 22 remaining under the second photoresist 24 is not removed.

Thus, as shown in FIG. 2C, only the region 24 in which the contact hole is to be formed is exposed, and the remaining region is covered with the first and second photoresists 22 and 23.

As illustrated in FIG. 2D, the contact holes 25 are formed by etching the insulating layer using an anisotropic etching process using the patterned first and second photoresists 22 and 23 as etching masks.

3A is a plan view showing a first mask and a second mask for exposing the first and second photoresists of the present invention, and FIG. 3B is a cross-sectional view taken along the line II-II of FIG. 3A.

As shown in FIGS. 3A and 3B, a chromium (Cr) film pattern 32 is formed on the quartz substrate 31 at regular intervals.

4A to 4C are cross-sectional views showing examples of polarization processing of the first and second masks.

That is, a polarizing material that coats the polarizing material 33 on the front or rear of each L / S mask or polarizes the pellicle 34 in the L / S direction to facilitate exposure energy control and increase the contrast of the image. Made of 33.

3A illustrates a case in which the entire surface of the photo mask is coated with the polarizing material 33, and FIG. 3B illustrates a case in which the rear surface of the photo mask is coated with the polarizing material 33, and FIG. 3C is made of the polarizing material 33. The case of using the pellicle 34 is shown.

On the other hand, in each case, the polarization direction of the polarizing material is the same as the direction of the L / S pattern.

In most cases, the exposure light source of the exposure machine is not polarized or circularly polarized even if it is polarized. Therefore, the light passing through each L / S mask is reduced by half (50%) compared to the case where it is not polarized. When the L / S mask is sequentially exposed, the intensity of the overlapped portion is 100% naturally, so the optimum exposure energy of the L / S pattern can be used.

As described above, the method for forming a contact hole in a semiconductor device according to the present invention has the following effects.

First, since the photoresist is patterned in a periodic L / S pattern using two lithography processes, it is possible to form a contact hole faithful to the mask design without being affected by the optical proximity effect.

Second, since there is no area reduction due to the rounding of the contact hole, the contact resistance can be reduced.

Third, the contrast of the image may be enhanced by coding a polarizing material in the L / S direction or using a pellicle made of the polarizing material in the L / S pattern mask.

Fourth, in order to reduce the size of the contact hole, various techniques applied to improving the resolution capability of the L / S pattern may be applied.

Claims (5)

Forming an insulating film on the semiconductor substrate; Applying a first photoresist on the insulating film; Patterning the first photoresist in a first direction using a first mask in which a line / space (L / S) pattern is defined; Applying a second photoresist to the entire surface of the semiconductor substrate including the patterned first photoresist; The second photoresist is perpendicular to the first direction using a second mask in which a line / space (L / S) pattern is defined perpendicular to the line / space (L / S) pattern of the first mask. Patterning in a second direction; And forming a contact hole by selectively removing the insulating layer by using the patterned first and second photoresists. The method of claim 1, further comprising ultraviolet treating or curing the first photoresist patterned in the first direction before applying the second photoresist. . The method of claim 1, wherein the first mask and the second mask are identical to each other, and the second mask rotates the first mask by 90 °. The method of claim 1, wherein the first mask and the second mask are coated with a polarizing material on a front surface or a rear surface of the first mask and the second mask so as to be polarized in the L / S direction. The method of claim 4, wherein a pellicle is used as the polarizing material.