KR100752172B1 - Method for Forming of Contact Hole - Google Patents

Abstract

The present invention relates to a method of forming a contact hole.

In the method for forming a contact hole according to the present invention, first, an antireflection film and a photoresist material are sequentially applied onto an insulating film formed on a silicon substrate, and the photoresist material is exposed and developed to form a photoresist pattern.

The antireflection film is selectively etched using oxygen having a flow rate of 6 sccm to 8 sccm and methylene fluoride having a flow rate of methylene fluoride of 25 sccm to 27 sccm as an etchant. At this time, it is preferable that the ratio of oxygen and methylene fluoride is 6: 27-8: 25. In addition, it is preferable to further include 400 sccm of argon in the etchant. The anti-reflection film is etched for 60 seconds at a voltage of 1300 Ws at a pressure of 150 mT. A contact hole is formed by etching the antireflection film and then selectively etching the insulating film.

Etching under these conditions reduces the difference between the design critical dimension and the actual dimension of the contact hole, thereby forming a fine contact hole.

Contact Hall. Antireflection film. Etching

Description

Method for Forming of Contact Hole

1A to 1C are cross-sectional views illustrating a method for forming a contact hole.

2 is a graph showing a pattern deviation value of a contact hole according to an etchant ratio.

3 is a photographic view of a contact hole formed according to an etchant ratio.

4 is a graph showing upper and lower critical dimensions of a contact hole formed according to an etchant ratio.

The present invention relates to a method for forming a contact hole, and more particularly, to a method for forming a contact hole suitable for forming a fine contact hole by adjusting a deviation between a design threshold dimension and a final threshold dimension of a pattern line width.

The semiconductor device is composed of a transistor, a capacitor, and the like, and forms a wiring as a means for transferring an electrical signal between the respective components. This wiring is in contact with the desired portion through the contact hole. Like the various patterns, contact holes are formed through a photolithography process.

The photolithography process includes a coating step of applying a photoresist on an etch target layer, an exposure step of irradiating light to a predetermined portion of the applied photoresist, and a developing step of removing an exposed or unexposed part of the photoresist. The desired pattern is formed by etching the layer to be etched using the photoresist pattern finally obtained through this process. At this time, the critical dimension (CD) of the pattern that can be implemented by the photolithography process depends on the wavelength of the light source used in the exposure process. This is because the CD of the actual pattern is determined according to the line width of the photoresist pattern that can be realized through the exposure process.

However, there is a limit to forming a pattern with a specific light source. In particular, other methods have been proposed for forming a fine pattern contact hole due to the limitation of the exposure apparatus.

For example, when manufacturing a contact hole using a KrF light source, a design CD (Development Inspection Critical Dimension), which is a critical dimension in the exposure process, and a final inspection critical dimension, which is a dimension of an actual pattern formed through etching, FI CD). This pattern deviation generally has a larger value than FI CD for DI CD. That is, as contact holes having a CD value larger than the dimensions designed for forming the contact holes are formed, there are further difficulties in miniaturizing the contact holes.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for forming a contact hole capable of forming a fine contact hole by reducing a deviation between a design CD and a final CD.

In order to achieve these objects, the method for forming a contact hole according to the present invention first sequentially applies an antireflection film and a photoresist material on an insulating film formed on a silicon substrate, and forms a photoresist pattern through an exposure and development process. .

The antireflection film is selectively etched using oxygen having a flow rate of 6 sccm to 8 sccm and methylene fluoride having a flow rate of methylene fluoride of 25 sccm to 27 sccm as an etchant. At this time, it is preferable that the ratio of oxygen and methylene fluoride is 6: 27-8: 25. In addition, it is preferable to further include 400 sccm of argon in the etchant. The anti-reflection film is etched for 60 seconds at a voltage of 1300 Ws at a pressure of 150 mT.

After the anti-reflection film is etched, the insulating film is selectively etched to form contact holes.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In the method for forming a contact hole according to the present invention, first, a bottom anti-reflective coating 6 and a photoresist material 8 are coated on an insulating film 4 formed on the silicon substrate 2 as shown in FIG. 1A. The anti-reflection film 6 is for preventing a problem caused by reflection of light in the process of exposing the photoresist material 8.

Subsequently, a photoresist pattern 8a is formed as shown in FIG. 1B through an exposure and development process using a mask (not shown).

The anti-reflection film 6 and the insulating film 4 are selectively etched based on the photoresist pattern 8a to form the contact holes 11 as shown in FIG. 1C. The antireflection film 6 is then removed.

As described above, the contact hole 11 needs to be subjected to several photo-processing and etching processes, and the etching process is closely related to the formation of the contact hole 11. The etching process is as follows. .

First, in order to etch the antireflection film 6, it is etched using argon (Ar), oxygen (O ₂ ) and methylene fluoride (CH ₂ F ₂ ). The pressure is set at 150mT and the voltage is set at 1300Ws, which is etched for about 60 seconds.

The anti-reflection film 6 is used to form holes for starting the insulating film etch, which is an important factor in determining the size of the overall etching pattern.

Among the etching conditions, the ratio of the etchant is one of the important factors controlling the etching rate. Since the anti-reflection film 6 is oxygen (O ₂₎ in a first etching for etching is etching the photoresist pattern oxygen (O ₂₎ is etched much large, the photoresist pattern greater the CD. On the other hand, since methylene fluoride (CH ₂ F ₂ ) produces a polymer, when methylene fluoride (CH ₂ F ₂ ) is large, polymer deposition is large and CD is reduced.

As such, CD is directly affected by the etching agents oxygen (O ₂ ) and methylene fluoride (CH ₂ F ₂ ).

Looking at the value of the pattern deviation according to the flow rate of the etching gas in the process of etching the anti-reflection film (6) as follows.

Table 1 shows the pattern deviation values of the contact holes according to the ratio of O ₂ / CH ₂ F ₂ during the etching of the anti-reflection film 6.

A / B DI CD (μm) FI CD (μm) Pattern deviation (μm) 0.222 (6/27) 0.1793 0.1684 0.0109 0.269 (7/26) 0.1776 0.1714 0.0062 0.320 (8/25) 0.1779 0.1761 0.0019

As shown in Table 1 above, as the ratio of O ₂ / CH ₂ F ₂ decreases, the pattern deviation gradually decreases, and when the ratio of O ₂ / CH ₂ F ₂ is 0.320 μm, the pattern deviation decreases to 0.0019 μm. .

FIG. 2 is a graph showing the results of Table 1. The pattern deviation has a linear relationship with -0.0924X + 0.0313 (µm) with respect to the change of O ₂ / CH ₂ F ₂ (change of X value). Able to know.

3 shows that the surface and the cross section of the anti-reflection film 6 were etched while varying the value of O ₂ / CH ₂ F ₂ , and then the plane and the cross section were observed through an electron microscope. The photograph is shown.

As shown in FIG. 3, when the value of O ₂ / CH ₂ F ₂ is changed, the size of the CD is different but the shape of the final contact hole is not different.

On the other hand, Table 2 is a table showing the change in the upper CD and the lower CD value of the contact hole in the details of the form of the contact hole when the contact hole is formed by changing the value of O ₂ / CH ₂ F ₂ .

O2 / CH2F2 Contact hole size (㎛) Top (XSEM) CD Lower (XEM) CD FI CD 0.222 (6/27) 0.1810 0.1590 0.1684 0.269 (7/26) 0.1869 0.1660 0.1714 0.320 (8/25) 0.1930 0.1720 0.1761

4 is a graph showing the change of the upper CD and the lower CD according to the change of O ₂ / CH ₂ F ₂ with the measured values of Table 2.

As shown in Table 2 and FIG. 4, it can be seen that the change of the upper CD and the lower CD also changes linearly with respect to the change of O ₂ / CH ₂ F ₂ . As such, by controlling the ratio of O ₂ / CH ₂ F ₂ , the pattern deviation can be reduced, and thus the size of the finally formed contact hole can be reduced.

That is, by adjusting the pattern deviation of the contact hole to 1 nm to 10 nm, the pattern variation of the contact hole can be increased to about (+) 7 nm to 20 nm compared with the conventional pattern deviation of (-) 6 nm to (-) 10 nm. That is, by reducing the size of the actual pattern after the contact hole is formed by about 7nm ~ 20nm than before, a condition more suitable for forming a fine contact hole is formed.

After the antireflection film is etched under such conditions, the insulating film is etched using the photoresist pattern and the antireflection film pattern as masks.

The etching of the insulating layer may be divided into main etching and over etching. The main etch is etched for about 80 seconds using a argon (Ar), oxygen (O ₂ ), carbon monoxide (CO) and octafluorocyclobutane (C ₄ F ₈ ) as a etchant at a pressure of 1700Ws at a pressure of 55mT. At this time, the flow rate of the etchant is argon (Ar) is 380sccm, oxygen (O ₂ ) is 10sccm, carbon monoxide is 300sccm and octafluorocyclobutane (C ₄ F ₈ ) to 16sccm.

As such, over etching is performed through the main etching to etch the insulating film that is not completely etched. In the over-etching, an etchant having a large selectivity between the insulating film and the silicon substrate is used so that the lower portion of the insulating film is not etched while the remaining insulating film is etched. That is, using argon (Ar), oxygen (O ₂ ) and octafluorocyclobutane (C ₄ F ₈ ) is etched for about 58 seconds at a voltage of 50mT, 1500Ws. At this time, the flow rate of the etchant is set to 380 sccm for argon, 10 sccm for oxygen and 10 sccm for octafluorocyclobutane (C ₄ F ₈ ).

As described above through the examples, it is an object to provide a method for manufacturing a contact hole that is advantageous to fine plug holes by reducing the difference between the CD design value and the CD value after actual etching.

In the present specification and drawings, preferred embodiments of the present invention have been disclosed, and although specific terms have been used for this purpose, they are merely used in a general sense to easily explain the technical contents of the present invention and to help the understanding of the present invention. It is not intended to limit the scope of the invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

Claims (5)

A first step of sequentially applying an anti-reflection film and a photoresist material on the insulating film formed on the silicon substrate, Forming a photoresist pattern by exposing and developing the photoresist material; A third step of selectively etching the antireflection film by using oxygen having a flow rate of 6 sccm to 8 sccm and methylene fluoride having a flow rate of methylene fluoride of 25 sccm to 27 sccm as an etchant; And a fourth step of selectively etching the insulating film. The method of claim 1, The ratio of the oxygen and the methylene fluoride in the third step is a contact hole forming method, characterized in that 6:27 ~ 8:25. The method of claim 1, The method of claim 3, wherein the etchant further comprises 400 sccm of argon. The method of claim 1, The third step is a contact hole forming method characterized in that the etching for 60 seconds at a voltage of 1300Ws at a pressure of 150mT. The method of claim 1, The fourth step is Etching for 80 seconds with 380 sccm of argon, 10 sccm of oxygen, 300 sccm of carbon monoxide and 16 sccm of octafluorocyclobutane at a pressure of 1700 Ws at a pressure of 55 mT, And etching for 58 seconds with 500 sccm of argon, 10 sccm of oxygen, and 10 sccm of octafluorocyclobutane at a pressure of 1500 Ws at a pressure of 50 mT.

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