KR20030044473A - A forming method of pattern using ArF photolithography - Google Patents

Abstract

PURPOSE: A method for forming a pattern using ArF exposing source is provided to be capable of minimizing the deformation of a photoresist pattern. CONSTITUTION: An etch object layer(11) is formed on a semiconductor substrate(10). A hard mask(12) containing a nitride layer and an organic anti-reflective layer are sequentially formed on the etch object layer(11). After forming a photoresist pattern on the resultant structure, the organic anti-reflective layer and the hard mask(12) are sequentially and selectively etched. Preferably, an oxide layer is formed at interface between the hard mask(12) and the organic anti-reflective layer.

Description

A forming method of pattern using ArF photolithography

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor technology, and more particularly, to a pattern formation method using an argon fluoride (hereinafter referred to as ArF) exposure source.

The microfabrication technology that has supported the progress of semiconductor devices is a photolithography technology, and it is no exaggeration to say that the improvement in resolution of this technology is directly connected to the future of high integration of semiconductor devices.

As is well known, the photolithography process includes a process of forming a photoresist pattern and a process of etching a layer to be etched through an etching process using the photoresist pattern as an etch mask to form a pattern having a desired shape such as a contact hole. Wherein the photoresist pattern includes a process of applying a photoresist on the etched layer, a process of exposing the photoresist using a prepared exposure mask, and a portion of the photoresist exposed or not exposed with a predetermined chemical solution; Through the development process.

On the other hand, the critical dimension of the pattern that can be implemented by the photolithography process (hereinafter referred to as CD) depends on the wavelength of the light source used in the above exposure process. This is because the CD of the actual pattern is determined by the width of the photoresist pattern that can be realized through the exposure process.

The wavelength of the light source used in the initial stepper adopting the “step and repeat” exposure method is from 436 nm (g-line) to 365 nm (i-line) and is now 248 nm (KrF Excimer Laser) wavelength. It mainly uses stepper or scanner type exposure equipment using DUV (Deep Ultra-violet). The 248 nm DUV photolithography initially produced a number of problems, such as time delay effects and substrate dependence. However, the development of new DUV photolithography technology with a new wavelength of 193nm (ArF Excimer Laser) is essential to develop products with a design of 0.15µm or less.However, in order to improve the resolution in such DUV photolithography technology, Even if the technique is combined, the pattern of 0.1 占 퐉 or less is impossible, and therefore, the development of the photolithography technique having a new light source is actively progressing.

At present, an ArF (argon fluoride) laser (λ = 193 nm) is being developed to target a pattern up to 0.11 mu m. DUV photolithography is superior in terms of performance and resolution compared to i-rays, but process control is not easy. These problems can be divided into optical causes due to short wavelengths and chemical causes due to the use of chemically amplified photoresists. If the wavelength is shortened, the CD shake phenomenon due to the stationary wave effect and the reflection of reflected light due to the substrate phase become worse.

CD oscillation refers to a phenomenon in which the line thickness changes periodically as the degree of interference between incident light and reflected light changes depending on the slight thickness difference of the resist or the thickness difference of the substrate film. In the DUV process, a chemically amplified photoresist has to be used to improve sensitivity, and problems related to the reaction mechanism include PED (Post Exposure Delay) stability and substrate dependence. Development of a photoresist for ArF.

ArF is a chemically amplified type such as KrF, but the material needs to be fundamentally improved. ArF resist material development is difficult because benzene rings cannot be used. Benzene rings have been used in photoresists for i-rays and KrF to ensure dry etching resistance. However, when the benzene ring is introduced into the ArF photoresist, since the absorbance is large at 193 nm, which is the wavelength region of the ArF laser, the transparency is low and the exposure to the lower portion of the photoresist is impossible. For this reason, research is being conducted on materials that can secure dry etching resistance without having a benzene ring, have good adhesion, and can be developed to 2.38% TMAH. To date, many companies and research institutes around the world have published their research results.

However, the photoresist in the form of COMA (CycloOlefin-Maleic Anhydride) or Acrylate polymer or a mixture thereof is commercially available for ArF, but they also have a benzene structure as described above.

Therefore, as shown in FIGS. 1A and 1B, chlorine-based plasma, which is a characteristic of ArF, during a process such as landing plug contact (LPC) through photolithography using an ArF exposure source. Rather, due to its weak resistance to fluorine-based plasma, stripe-shaped patterns may occur, photoresist may clump during SAC etching, or plastic deformation and resistance of photoresist during SAC etching. This weakness causes a phenomenon to be driven to one side.

Therefore, efforts are made to make up for the weak durability of ArF resistors and the weak physical properties of fluorine-based gas. Thus, hardening the photoresist surface or generating a large amount of polymer during etching of the lower layer protects the photoresist surface. This is being taken.

However, the ArF photoresist is particularly affected by the material state of the underlying layer. When the ArF photoresist is applied on the nitride mask-based hard mask or the nitride film-based antireflection layer which is usually formed on the insulating layer, Compared to other insulating films, the surface roughness of the ArF photoresist becomes more rough. FIG. 2 shows the surface roughness of the ArF photoresist according to the material state of each base layer. The roughness is increased at the interface in contact with the nitride film series.

Therefore, as the surface roughness is transferred downward as it is during the etching process, it acts as one of the main causes of deterioration of the pattern of the device.

3 (a) and 3 (b) are photographs showing that the ArF photoresist pattern is deteriorated, and as shown in FIG.

As described above, when the pattern is formed using the photoresist for ArF, not only the durability of the photoresist itself but also many restrictions on the material of the underlying layer are followed.

The present invention proposed to solve the problems of the prior art as described above, to provide a pattern forming method using an argon fluoride exposure source that can minimize the pattern deformation due to the surface roughness of the ArF photoresist and the underlying layer. There is this.

1 and 3 are photographs showing the deformation of the pattern during the photolithography process using the ArF exposure source,

Figure 2 is a photograph showing the surface roughness of the ArF photoresist according to the material state of the ArF PR and the underlying layer,

3 (a) and 3 (b) are photographs showing that the photoresist pattern for ArF is deteriorated,

4A to 4C are cross-sectional views illustrating a pattern forming process using an argon fluoride exposure source according to an embodiment of the present invention;

5 is a photograph showing a comparison between a good pattern and a conventional pattern deformation due to the process application of the present invention.

* Explanation of symbols for the main parts of the drawings

10: substrate

11: etching target layer

12: hard mask

The present invention to solve the above problems, forming an etching layer on the substrate; Sequentially forming a hard mask including a nitride film and an organic antireflection layer on the etched layer; Applying a photoresist for argon fluoride on the antireflection layer; Forming a photoresist pattern by an exposure and development process using a predetermined mask; And selectively etching the anti-reflection layer, the hard mask, and the etched layer in order using the photoresist pattern as a mask.

The present invention to be described later, by using an organic antireflection layer on the hard mask of the nitride film series before the ArF photoresist coating, to improve the etching resistance which is a problem of the ArF photoresist pattern to prevent the etching profile is deteriorated The main factor above the profile is to solve problems such as pattern deformation due to surface roughness between the photoresist and the underlying material, in particular, a nitride based material.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can more easily implement the present invention.

4A to 4C are cross-sectional views illustrating a pattern forming process using an argon fluoride exposure source according to an embodiment of the present invention.

First, as shown in FIG. 4A, an etching target layer 11 and a nitride-based hard mask 12 are formed on a substrate 10 on which various elements for forming a semiconductor device are formed, and then an organic antireflection film 13 ) Is formed to a thickness of 100 kPa to 1000 kPa.

Here, the etching target layer 11 is a conventional insulating film, for example, an oxide film such as BPSG (Boro Phospho Silicate Glass) or SOG (Spin On Glass) in the process of forming the contact hole between the conductive patterns such as the gate electrode. That is, it includes a non-conductive material, and in the case of forming a pattern such as metal wiring, bit line or word line, it includes a conductive material such as polysilicon, W or aluminum.

Subsequently, after the photoresist is applied on the antireflection layer 13, the photoresist pattern 14 is formed through a photolithography process using an ArF exposure source.

Specifically, an ArF photoresist such as COMA or acrylate is applied on the antireflection layer 13 to a thickness of 2000 kPa to 5000 kPa, and then an argon fluoride exposure source (not shown) and a predetermined reticle (not shown) are applied. The photoresist pattern 14 may be selectively exposed to a predetermined portion of the photoresist, and the exposed or unexposed portions of the photoresist may be left through a developing process and then the etch residue may be removed through a post-cleaning process. ).

In this case, in order to minimize the loss of the photoresist pattern 14 due to the subsequent etching process, a process of curing the photoresist pattern 14 may be additionally performed. In this case, curing using hard bake, ultraviolet light, or electron beam may be performed. It is preferable to carry out the ring (Curing), during hard baking for 10 to 1000 minutes while maintaining a temperature of 120 ℃ to 180 ℃.

Next, as illustrated in FIG. 4B, the antireflection layer 13 and the hard mask 12 are selectively etched using the photoresist pattern 14 as a mask to transfer the pattern to the lower portion.

Subsequently, the etching target layer is selectively etched using the hard mask 12 including the photoresist pattern 14 as a mask.

In this case, when using an Self Align Contact (hereinafter referred to as SAC) as an example, dry etching by plasma is used, and C _x F _y (x is 1 to 5, y is 1 to 10), and C _x An etching gas containing F, such as H _y F _z (x, y, z is 1 to 3) or S _x F _y (x is 1 to 5, y is 1 to 10), is used.

On the other hand, in the case of O ₂ gas acts as a main cause of the abnormality of the pattern profile, it is preferable to exclude this. In addition, since the pattern is particularly sensitive to temperature, the temperature of the substrate 10 is appropriately adjusted to minimize pattern deformation, and the lower electrode cooling temperature, internal pressure, bias power, etc. of the etching apparatus are appropriately adjusted.

Next, as illustrated in FIG. 1D, a desired pattern having a minimum pattern deformation may be formed by removing the photoresist pattern 14 and the anti-reflection layer 13 by performing a photo resist strip process. .

In this case, the photoresist strip process may be performed after the anti-reflection layer 13 or the hard mask 12 is etched.

Meanwhile, in order to improve the surface roughness at the nitride film series and the ArF photoresist interface, as described above, the antireflection layer of the organic series is formed to have a predetermined thickness, so that a thin oxide film may be further formed between the antireflection layer and the nitride film. have. This is because the oxide film has a better surface roughness at the contact interface with the ArF photoresist than the nitride film.

FIG. 5 is a photograph showing a comparison between a good pattern, for example, a bit line and a conventional pattern deformation by the above-described process application, and FIG. 5 (a) shows a conventional pattern deformation, and FIG. The bit line pattern formed according to the process application is shown.

According to the present invention as described above, by using an organic antireflection layer at an interface between the photoresist pattern and the nitride film-based hard mask, deformation of the photoresist pattern due to surface roughness can be prevented, and finer pattern formation can be achieved. The embodiment has been found to be possible.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

According to the present invention described above, it is possible to prevent the deformation and loss of the photoresist pattern according to the ArF transfer method, it can be expected excellent effect that can improve the integration degree of the device.

Claims (6)

Forming an etched layer on the substrate; Sequentially forming a hard mask including a nitride film and an organic antireflection layer on the etched layer; Applying a photoresist for argon fluoride on the antireflection layer; Forming a photoresist pattern by an exposure and development process using a predetermined mask; And Selectively etching the antireflective layer, the hard mask, and the etched layer in order using the photoresist pattern as a mask; Pattern formation method using an argon fluoride exposure source comprising a. The method of claim 1, And forming an oxide film at an interface between the hard mask and the anti-reflective layer. The method of claim 1, The patterning method using an argon fluoride exposure source, characterized in that the etching layer comprises a non-conductive material. The method of claim 1, The patterned method using an argon fluoride exposure source, characterized in that the etching layer comprises a conductive material. The method of claim 1, The pattern forming method using an argon fluoride exposure source, characterized in that the antireflection layer is formed to a thickness of 100 ~ 1000Å. The method of claim 1, A pattern forming method using an argon fluoride exposure source, wherein the photoresist is formed to a thickness of 2000 kPa to 5000 kPa.