KR20020012412A - Method of forming a photoresist pattern - Google Patents

Abstract

A photosensitive film pattern forming method is provided. The method comprises the steps of applying a photoresist film on a semiconductor substrate, selectively exposing a predetermined region of the photoresist film, and curing the photoresist film by performing a heat treatment to remove moisture and solvent present in the exposed photoresist film. Developing the cured photoresist to form a photoresist pattern. The heat treatment here is carried out in an oven at a temperature between 80 ° C and 200 ° C. This prevents the photoresist pattern from flowing due to an additional process such as ultraviolet baking and can simplify the process.

Description

Photosensitive film pattern formation method {METHOD OF FORMING A PHOTORESIST PATTERN}

The present invention relates to a method of forming a photosensitive film pattern.

In the semiconductor device manufacturing process, a number of photographic and etching processes are repeatedly performed.

The photolithography process forms a photoresist pattern by coating a photoresist on a semiconductor substrate and selectively passing light on the photoresist through an exposure apparatus. In general, the photoresist pattern serves as an etching mask. That is, the portion not exposed by the photoresist pattern on the semiconductor substrate in the ion implantation process or the etching process may be protected from ion implantation and etching. Through a series of photolithography, etching, ion implantation, and deposition, semiconductor devices are completed.

The photographic process may be subdivided into an exposure process and a developing process. Due to the high integration of semiconductor devices, the exposure equipment used in the above exposure process has been rapidly developed, and advanced exposure equipment capable of forming ultra-fine patterns has been used in the photolithography process. However, it is true that the development process using various chemicals has not made much progress compared to the rapid technological improvement of exposure equipment. For this reason, even after exposing the photoresist on the semiconductor substrate for a fine pattern, a case in which the photoresist pattern is not matched in the development process may occur.

Hereinafter, the problems of the prior art will be described with reference to FIGS. 1 and 2.

Referring to FIG. 1, a photosensitive film is coated on a semiconductor substrate 10, and a photosensitive film pattern 12 is formed on the semiconductor substrate 10 through an exposure and development process. As a result, the exposed semiconductor substrate 10 is etched during the subsequent dry etching, and the semiconductor substrate 10 protected by the etching mask, which is the photosensitive film pattern 12, remains after the dry etching and thus the semiconductor substrate 10 The pattern to be implemented is formed on). Here, of course, the case where the etching target layer is the semiconductor substrate 10 is exemplified. However, even when another etching target layer is present on the semiconductor substrate 10, the etching pattern formation process of the etching target layer by the photoresist pattern is the same.

Referring to FIG. 2, an ultra violet bake is performed to cure the photoresist pattern 12 so that the photoresist pattern 12 may serve as a mask. Ultraviolet bake removes moisture inside the photoresist pattern 12 by thermal energy, and irradiates the surface of the photoresist pattern 12 with ultraviolet rays to cause the photo active compound (PAC), a constituent material of the photoresist layer, to be cross-linked. The photoresist pattern 12 is chemically cured so as to be effective.

However, the ultraviolet baking process promotes a serious density change in the surface and the inside of the photoresist pattern 12 to cause the photoresist pattern 12 to flow. The flow of the photoresist pattern 12 has a problem in that a space CD after etching is increased due to the flow of the photoresist pattern 14 in a subsequent dry etching process. That is, the photoresist pattern 12 flows to the exposed semiconductor substrate 10 region, thereby preventing CD from performing a role as an etching mask in a dry etching process, thereby increasing CD. In addition, when the subsequent process is an ion implantation process, a problem arises in which a portion of the region to be ion implanted on the semiconductor substrate 10 is covered by the flow of the photoresist pattern 12.

Accordingly, the technical problem to be achieved by the present invention is to provide a method of forming a photosensitive film pattern which can minimize the difference between the CD after the development of the photographic process and the CD after etching.

1 and 2 are cross-sectional views for explaining the problem of the photosensitive film pattern formation according to the prior art.

3 and 4 are cross-sectional views illustrating a method of forming a photosensitive film pattern according to the present invention.

In order to achieve the above technical problem, the present invention comprises the steps of applying a photosensitive film on a semiconductor substrate, selectively exposing a predetermined region of the photosensitive film, and a heat treatment to remove the moisture and solvent present in the exposed photosensitive film And curing the photoresist film and developing the photoresist film cured by the heat treatment to form a photoresist pattern.

The heat treatment is preferably carried out in an oven at a temperature between 80 ℃ to 200 ℃.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 3 to 4.

Referring to FIG. 3, dehydration bake is performed to remove moisture on the semiconductor substrate 20 before the photoresist film 22 is applied on the semiconductor substrate 20. The dehydration bake is preferably performed at a temperature of 150 ℃ to 200 ℃ in a vacuum state. After the dehydration bake, an adhesion promoter (not shown) is applied onto the semiconductor substrate 20. The adhesion strengthening agent may use HMDS (HexaMethylDiSilazane). The adhesion enhancer serves to help the photoresist film 22 to be adhered well on the semiconductor substrate 20.

Subsequently, the photosensitive film 22 is coated on the entire surface of the semiconductor substrate 20 to which the adhesive strengthening agent is applied. The coating of the photoresist layer 22 may be performed using a spin coating method of rotating the semiconductor substrate 20 at high speed and introducing the photosensitive liquid onto the semiconductor substrate 20 through a nozzle. Preferably, the spin coating is rotated at a rotation rate between 2000 rpm and 8000 rpm. In general, when the photoresist film 22 is formed by spin coating, less than 1% of the photoresist flowing through the nozzle is formed as the photoresist film 22 on the semiconductor substrate 20, and the remaining photoresist is applied to the rotation of the semiconductor substrate 20. Pushed out and spilled out.

A soft bake process is performed on the semiconductor substrate 20 to which the photosensitive film 22 is coated. The soft bake removes moisture and solvent in the photoresist layer 22 and stabilizes the photoresist layer 22. When the solvent is removed by the soft bake, the thickness of the photoresist layer 22 becomes thin.

The semiconductor substrate 20 on which the soft bake is completed is transferred to an exposure apparatus such as a stepper for exposure. In the stepper, the photoresist 22 of the semiconductor substrate 20 is exposed through a photomask. Subsequently, a peripheral exposure process of exposing the photosensitive film 22 at the edge of the semiconductor substrate 20 is performed. Through the peripheral exposure, the photosensitive film 22 at the edge portion of the semiconductor substrate 20 may be removed in a subsequent development process.

A PEB (Post Exposure Bake) process is performed on the semiconductor substrate 20 on which the peripheral exposure is completed. The PEB maximizes the difference between the exposed portions of the photoresist layer 22 and the portions not so as to have an accurate CD and profile when the photoresist pattern is formed by a subsequent phenomenon. PEB also reduces the production of residues left after subsequent development. In the PEB process, the water and the solvent in the photoresist film 22 are completely removed and a high temperature heat treatment is performed to perform the role of an etching mask after the formation of the subsequent photoresist pattern without a subsequent ultraviolet bake process. The heat treatment is preferably carried out in an oven at a temperature between 80 ℃ to 200 ℃.

Referring to Figure 4, the development is carried out after the PEB. As the developing solution used in the developing step, an alkaline solution such as NaOH or KOH can be used as the developing solution. Through the development, the photoresist film 22 is formed into the photoresist pattern 22a, and then the developing process of the photoresist pattern 22a is completed by a cleaning process. The semiconductor substrate 20 is dry etched using the photoresist pattern 22a as an etching mask. The photoresist pattern developed through the PEB serves as an etch mask in a high temperature plasma etching process without performing additional ultraviolet baking and does not generate a flow of the photoresist pattern, thereby ensuring accurate CD.

As described above, in order to prevent the flow of the photoresist pattern by the ultraviolet bake process, the photoresist pattern is cured without performing the ultraviolet bake process by performing a high temperature heat treatment in the PEB process before the developing process. It has the effect of enabling simple and accurate CD control.

Claims (2)

Coating a photosensitive film on a semiconductor substrate; Selectively exposing a predetermined area of the photosensitive film; Curing the photoresist by performing a heat treatment to remove moisture and solvent present in the exposed photoresist; And And developing the photosensitive film cured by the heat treatment to form a photosensitive film pattern. According to claim 1, The heat treatment is carried out in an oven at a temperature of between 80 ℃ to 200 ℃ photosensitive film pattern forming method.