# Patent

## Title
Chemical amplification photoresist comprising a reverse reaction

## Abstract

The method of forming a photoresist film in a semiconductor according to the present invention comprises a first step for coating a photoresist on a wafer, a second step for dispersing a nitrogen gas of high pressure on the wafer to eliminate microscopic riffle waves, pin holes, and peeling portions formed on the surface of the photoresist film, a third step for dispersing a dried nitrogen gas of high temperature to remove a solvent contained within the photoresist film and bake the photoresist film.

## Background
1. Field of the Invention

The present invention relates to an apparatus for forming a photoresist film in a semiconductor device and method of forming a photoresist film using the same and, more particularly, to an apparatus for forming a photoresist film and method of forming a photoresist film using the same which can form an uniform photoresist film through a post-process performed in a first and a second chambers after forming a photoresist film on a wafer.

2. Description of the Prior Arts

Generally, a photolithography process for manufacturing a semiconductor device involves a coating process, a light exposure process, and a develop process for a photoresist film. In the coating process, the photoresist is dispensed on the wafer fixed at a spin chuck under a vacuum state. After the dispensing of photoresist is completed, the spin chuck is rotated at a high speed. Also, the wafer is rotated, thus, the photoresist dispensed on center portion of the wafer is dispersed uniformly on entire surface of the wafer by a centrifugal force. After coating process, the baking process is performed to remove a solvent contained in the photoresist film 9.

As shown In FIG. 1A, microscopic riffle waves A which can not be seen by a human's eye are existed on the surface of the photoresist film 9 coated on the wafer 8 by this process. Also, as shown in FIG. 1B, a plurality of pin holes B and peeling portions C are formed in the photoresist film 9. At this state, if the exposure process is performed, the microscopic riffle waves A, the pin holes B and the lifting portions C have caused a microscopic defocus.

In addition, in the baking process, the wafer 9 is loaded on a heater block or loaded in a bake oven. The wafer is heated on the heater block in contact heating manner or in the bake oven in heat convention manner. Therefore, the photoresist film 9 is not dried uniformly, especially an inner portion of the photoresist film 9 is not dried completely. Also, in case of using the heater block, since the heat is transferred from a bottom surface of the wafer to the photoresist film, the pattern can be damaged by the heat, thereby lowering the characteristic of device.

It is therefore an object of the present invention to provide an apparatus and method for forming a photoresist film which can planarize a surface of the photoresist film and dry the photoresist film completely.

An apparatus for forming a photoresist film according to the present invention comprises a photoresist coating unit for coating a photoresist on a wafer, a first chamber in which a nitrogen gas of high pressure gas is dispersed for planarizing a surface of the photoresist film formed on the wafer, and a second chamber in which a dried nitrogen gas of high temperature is dispersed for removing a solvent contained within the photoresist film and to bake the photoresist film.

The nitrogen gas dispersed in the first chamber is dispersed with a temperature of 4 through 20 degree Celsius and a high pressure of 150 through 250 psi, the dried nitrogen gas dispersed in the second chamber is dispersed with a high temperature of 100 through 200 degree Celsius and a pressure of 50 through 150 psi.

A method of forming a photoresist film according to the present invention comprises the steps of a first step for coating a photoresist on a wafer, a second step for dispersing a nitrogen gas of high pressure on the wafer to eliminate microscopic riffle waves, pin holes, and peeling portions formed on the photoresist film, and a third step for dispersing a dried nitrogen gas of high temperature to remove a solvent contained within the photoresist film and bake the photoresist film.

The nitrogen gas used in the first step is dispersed with a temperature of 4 through 20 degree Celsius and a high pressure of 150 through 250 psi, the dried nitrogen gas used in the second step is dispersed with a high temperature of 100 through 200 degree Celsius and a pressure of 50 through 150 psi.

Other objects and advantages of the present invention will be understood by reading the detailed explanation of the embodiment with reference to the accompanying drawings in which:

FIGS. 1A and 1B are cross-sectional views of a device for illustrating a conventional method of forming a photoresist film in a semiconductor device.

FIG. 2 is a plane view of an apparatus according to the present invention.

FIG. 3A is a cross-sectional view of a first chamber shown in FIG. 2.

FIG. 3B is a cross-sectional view of a second chamber shown in FIG. 2.

FIGS. 4A and 4B are cross-sectional views of a device for illustrating a method of forming a photoresist film in accordance with the present invention.

An apparatus and method of forming a photoresist film according to the present invention will be explained in detail by reference with the accompanying drawings.

Referring to FIG. 2, an apparatus 10 for forming a photoresist film comprises a photoresist coating unit 20, a first chamber 30 and a second chamber 40. The photoresist coating unit 20, the first chamber 30 and the second chamber 40 are installed in a space, the wafer is transferred the photoresist coating unit 20, the first chamber 30 and the second chamber 40, sequentially, by the wafer transfer system.

The photoresist coating unit 20 comprises a nozzle for dispensing a photoresist on surface of the wafer and, a conventional spinner for rotating a wafer.

As shown in FIG. 3A, the first chamber 30 comprises a housing 31. A gas supplying tube 35A is connected to upper end of the housing 31, and a buffer 32 and diffuser 33 are mounted under the gas supplying tube 35A. At bottom of the housing 31, a chill plate 34 for mounting and cooling a wafer W on which a photoresist film is formed is located, an exhaust outlet 35B is also formed. One the other hand, a wafer loading door 36A and unloading door 36B are formed at both side walls of the housing 31, respectively.

Nitrogen gas (N.sub.2 gas) of high pressure and low temperature is supplied into the housing 31 through the gas supplying tube 35A. A flow rate of nitrogen gas is reduced by the buffer 32, and nitrogen gas is dispersed evenly through the diffuser 33 having a plurality of fine holes. Coolant of temperature of about 4 degree Celsius is circulated in the chill plate 34 on which the wafer W is mounted, therefore, the wafer W is cooled.

As shown in FIG. 3B, the second chamber 40 comprises a housing 41. A gas supplying tube 45A is connected to upper end of the housing 41, and a buffer 42 and diffuser 43 are mounted under the gas supplying tube 45A. At bottom of the housing 41, a vacuum chuck 44 for chucking the wafer W is located, an exhaust outlet 45B is also formed. One the other hand, a wafer loading door 46A and unloading door 46B are formed at both side walls of the housing 46B.

Dried N.sub.2 gas of high temperature is supplied into the housing 41 through the gas supplying tube 45A. A flow rate of nitrogen gas is reduced by the buffer 42, and the dried N.sub.2 gas is dispersed through the diffuser 43 having a plurality of fine holes.

Meanwhile, the apparatus 10 further comprises wafer transfer systems (not shown) for transferring the wafer W from the photoresist coating unit 20 to the first chamber 30 and transferring the wafer W from the first chamber 30 to the second chamber 40, respectively. The wafer transfer systems are located between the photoresist coating unit 20 and the first chamber 30, and between the first chamber 30 and the second chamber 40, respectively.

The method of forming a photoresist film using the apparatus described above will be explained as follow;

Referring to FIG. 4A, a photoresist film P is formed on the wafer W by means of the photoresist coating unit 10. As described above, microscopic riffle waves A, pin holes B and peeling portions C which can not be seen by a human's eye are formed in the photoresist film P.

After finishing the photoresist coating process, the wafer W as shown in FIG. 4A is transferred from the photoresist coating unit 20 to the first chamber 30 through the wafer loading door 36A, and then mounted on the chill plate 34. The N.sub.2 gas of low temperature and high pressure is supplied through the gas supplying tube 35A, the N.sub.2 gas is dispersed by the diffuser 33. Therefore, the N.sub.2 gas pressures the surface of the wafer W, uniformly. During the process in the first chamber 30, the N.sub.2 gas is dispersed with a low temperature of 4 through 20 degree Celsius and a high pressure of 150 through 250 psi for about 1 through 10 minutes.

FIG. 4B is a cross sectional view of device showing a condition of the photoresist film after dispersing the N.sub.2 gas of high pressure. As shown in FIG. 4B, the microscopic riffle waves A, the pin holes B and the peeling portions C are disappeared and the thickness of the photoresist film P becomes thin evenly by dispersing of the N.sub.2 gas of a high pressure.

After dispersing the N.sub.2 of high pressure on the wafer W, the wafer W as shown in FIG. 4B. is transferred from the first chamber 30 to the second chamber 40 through the wafer unloading door 36B of the first chamber 30 and the loading door 46A of the second chamber 40, and the wafer W is mounted on the vacuum chuck 44. The dried N.sub.2 gas of high temperature and air are supplied, alternately, through the gas supplying tube 45A. The N.sub.2 gas is dispersed by the diffuser 43. Therefore, the solvent contained within the photoresist film P is vaporized by the dried N.sub.2 gas of high temperature, the photoresist film P becomes a solid state. During the dry process in the second chamber 40, the N.sub.2 gas is dispersed with a high temperature of 100 through 200 degree Celsius and a high pressure of 50 through 150 psi for 2 through 10 minutes.

Meanwhile, during a baking process in second chamber 40, since heat is transferred from a top surface, that is, the photoresist film P to the wafer W, the baking efficiency is enhanced and a damage of the pattern formed in the wafer can be minimized.

As mentioned above, in the present invention, microscopic riffle waves, pin holes, and a peeling portion formed in the photoresist film can be eliminated and the thickness of the photoresist film becomes thin evenly by dispersing of N.sub.2 gas of a high pressure. Also, solvent contained within the photoresist film is removed by dispersing of N.sub.2 gas with a high temperature. In addition, the baking efficiency of photoresist can be enhance, and damage of the wafer can be minimized.

The foregoing description, although described in its preferred embodiment with a certain degree of particularity, is only illustrative of the principle of the present invention. It is to be understood that the present invention is not to be limited to the preferred embodiments disclosed and illustrated herein. Accordingly, all expedient variations that may be made within the scope and spirit of the present invention are to be encompassed as further embodiments of the present invention.

## Claims

1. A method of forming a photoresist film in a semiconductor device, comprising the steps of: to eliminate microscopic riffle waves, pin holes, and peeling portions formed on said photoresist film; and remove a solvent contained within said photoresist film and bake said photoresist film.

2. The method of forming a photoresist film in a semiconductor device as claimed in claim 1, wherein said nitrogen gas used in said first step is dispersed with a temperature of 4 through 20 degree Celsius and a high pressure of 150 through 250 psi for 1 through 10 minutes.

3. The method of forming a photoresist film in a semiconductor device as claimed in claim 1, wherein said dried nitrogen gas used in said third step is dispersed with a high temperature of 100 through 200 degree Celsius and a pressure of 50 through 150 psi for 2 through 10 minutes.

4. The method of forming a photoresist film in a semiconductor device as claimed in claim 1, wherein said second step uses said dried nitrogen gas and air supplied, alternately.