JPH09297403A - Method for developing photoresist - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the pattern defects and to improve the uniformity in size of the pattern by optimizing the condition when a wafer is rotated after pure water is supplied before development. SOLUTION: Pure water is dripped on the surface of an exposed photoresist, a wafer is rotated at 600-2000r.p.m. for 0.2-6sec, and a water coating film is formed on the photoresist in 20-200μm thickness. A developer is then dripped from a nozzle to coat the rotating wafer so that the developer is held on the photoresist for a definite time. When a pattern is formed, the developer is rinsed out from the wafer with pure water, and then the wetted wafer is spin- dried. Consequently, a bubble is not deposited on the photoresist surface, the deveoper is not deactivated, the pattern defects are reduced, and the uniformity in pattern size is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for developing a photoresist used in a photolithography process in a semiconductor integrated circuit manufacturing process, for example.

[0002]

2. Description of the Related Art To develop a photoresist used in a photolithography step of a semiconductor integrated circuit manufacturing process,
In the case of a negative type, an organic solvent such as xylene is used as a developer in the case of a positive type, and an alkaline aqueous solution is used as a developer, and a pattern is formed by utilizing the difference in solubility between the exposed portion and the unexposed portion of the photoresist in these developing solutions. Is formed. In the photolithography process, the pattern shape and dimensional variation, the presence or absence of pattern defects, etc. are so important that they can be finally determined by this developing process.

A conventional general photoresist developing method will be described below with reference to FIG. As shown in this figure, while the wafer after the exposure is being rotated, the developing solution is dropped and applied from the upper nozzle, and the developing solution is kept on the wafer for a certain period of time. And when the pattern is formed,
The developer is removed from the wafer by rinsing with pure water, and then the wet wafer is spin dried. Through such a procedure, a fine pattern of the semiconductor integrated circuit is formed.

By the way, the developer is stored in, for example, a canister in the basement of a clean room, pressurized by nitrogen gas to 1.1 atmospheres or more, flows in a pipe, and is discharged from a discharge nozzle on the ground floor. It is a mechanism to operate. In this case, the nitrogen gas has a property that its solubility increases as the pressure of the liquid increases, but since the pressure of the liquid decreases to the atmospheric pressure in the vicinity of the developer discharge nozzle, the nitrogen gas is dissolved in the developer in the canister. The nitrogen gas becomes bubbles in the piping on the ground floor. When the developing solution is discharged onto the wafer in the state where there are bubbles in this way, there is a very high probability that the bubbles will remain even in the heap of the developing solution, and the bubbles will adhere to the photoresist. A pattern is formed by immersing the photoresist after exposure in a developing solution, but since a portion to which bubbles adhere is not in contact with the developing solution, a predetermined pattern is not formed and a so-called pattern defect occurs.

Therefore, for the purpose of preventing bubbles from adhering to the photoresist, there has been considered a method of improving the wettability of the photoresist surface so that the bubbles in the developer do not come into contact with the photoresist surface. Japanese Unexamined Patent Publication No. 7-1423
Japanese Patent Laid-Open No. 44-44 discloses a method of rinsing with pure water before applying a developing solution. In this method, as shown in the process flow of FIG. 4, pure water is supplied onto the exposed photoresist, and the substrate is rotated to form a film thickness of 0.05 to 0.
After forming a water film of 20 μm, application of a developing solution, embedding of a developing solution, rinsing with pure water, and spin drying are sequentially performed.

[0006]

By the way, as the degree of integration of semiconductor integrated circuits is improved to 16M and 64M, and the number of pattern defects must be reduced more and more as the fine processing advances. Has become. Then, as a countermeasure, the inventors of the present invention have conducted an analysis and found that the bubbles generated on the photoresist have a diameter of about 3 to 20 μm as measured by an image recognition type defect inspection apparatus. .

On the other hand, the technique disclosed in JP-A-7-142344 aims to prevent the adhesion of air bubbles having a large size of 50 to 200 μm as described in the publication, and for that purpose, the film thickness is about 0.05 to 0.20 μm. It was possible to prevent the bubbles from adhering due to the relatively large buoyancy of the bubbles themselves in the developing solution by only forming a water film of (3) to give a slight wettability to the photoresist surface.

However, the film thickness is 0.05 to 0.20 μm.
With a water film of about m, it is not possible to enclose all the bubbles having a size of 3 to 20 μm, and the bubbles are in a state of being pressed by the developer having high viscosity from above. Moreover, since the water film is thin and the bubbles are small, the buoyancy of the bubbles themselves does not act much, and even after rinsing with pure water and spin drying, the bubbles on the photoresist act between the thin water film. It remains attached due to surface tension. As a result, the photoresist under the bubbles having a diameter of about 3 to 20 μm remains in a circular shape as it is, and even if the technique of Japanese Patent Laid-Open No. 7-142344 is adopted, the occurrence of a relatively small pattern defect cannot be suppressed. Then, when the above-mentioned pressure transfer method using nitrogen gas is used as the developer supply method,
The problem of this pattern failure becomes more prominent because the dissolved gas in the developer increases.

Further, with the miniaturization, the uniformity of the pattern shape and dimensions within the wafer surface has become an important factor for the quality of semiconductor integrated circuits. For example, when rinsing with pure water before supplying the developing solution to reduce pattern defects, the concentration of the developing solution becomes non-uniform on the photoresist due to the mixing of pure water, which causes the width of the pattern within the wafer surface. There was a problem that there was a large variation in. That is, it is difficult for the conventional developing technique to satisfy both the reduction of pattern defects and the improvement of the uniformity of pattern dimensions.

The present invention has been made to solve the above problems, and provides a method for developing a photoresist that can satisfy both the reduction of pattern defects and the improvement of uniformity of pattern dimensions. With the goal.

[0011]

In order to achieve the above-mentioned object, a method of developing a photoresist according to the present invention comprises applying a photoresist onto a wafer, exposing the wafer, and then exposing the photoresist to pure water. It is characterized in that the wafer is supplied and the wafer is rotated under the conditions of a rotation speed of 600 to 2000 rotations / minute and a rotation time of 0.2 to 6 seconds, and then the developing solution is supplied onto the water film.

The inventors of the present invention have made detailed studies on a method of forming a water film on a photoresist before development. As a result, the number of rotations and time of the wafer after the supply of pure water is determined to be the number of pattern defects after development. It was found that both the number and the uniformity of the pattern size are greatly affected.

For the wafer after photoresist coating,
The pattern of lines and spaces was exposed by an i-line stepper, and in the flow shown in FIG. 1, development was performed after changing the wafer rotation speed and rotation time after supplying pure water before development to various conditions. After development, the line width of the photoresist was measured at 20 points on the wafer surface using a scanning electron microscope to obtain the line width variation, and the number of pattern defects was measured using an image recognition type particle inspection device. . As a result, as shown in FIG. 2, when the wafer rotation time after the pre-development pure water supply was less than 0.2 seconds, the line width varied greatly, and when it exceeded 6 seconds, pattern defects increased. . Further, regarding the number of rotations, it was found that when the number of rotations was less than 600 rotations / minute, the variation of the line width was large, and when it was more than 2000 rotations / minute, pattern defects increased.

The same result was obtained not only for lines and spaces but also for patterns such as contact holes. Therefore, in the present invention, when the wafer is rotated after the pure water is supplied before the development, the time is 0.2 seconds or more, 6
The rotation speed is 600 seconds / minute or more and 2000 rotations / minute or less. When the wafer is rotated under such conditions, a water film having a thickness of about 20 to 200 μm is formed on the photoresist surface. At this time, all the bubbles having a diameter of about 3 to 20 μm contained in the developer are in a state of being enclosed in the water film, and as a result, the bubbles are separated from the photoresist surface by the buoyancy in the water film, and are trapped in the water film. It becomes easier to float. That is, when pure water is supplied and the wafer is rotated, excess water drops outside the wafer, but as long as the water is rotated within the range of the above conditions, the remaining water film is 20 to 20%.
Since the thickness of 200 μm can be maintained, it is possible to prevent bubbles from floating in the water film and adhering to the photoresist surface.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a process flow diagram showing the procedure of the photoresist developing method of the present embodiment. As shown in this figure, first, pure water is dropped on the exposed photoresist surface and the wafer is rotated. On this occasion,
Rotation time is 0.2 to 6 seconds and rotation speed is 600 to 20
By setting the rotation speed to 00 rpm, a water film having a film thickness of 20 to 200 μm is formed on the photoresist. afterwards,
While rotating the wafer, the developing solution is dropped and applied from the nozzle, and the developing solution is kept on the wafer for a certain period of time.
Then, when the pattern is formed, the developer is removed from the wafer by pure water rinsing, and then the wet wafer is spin-dried.

[0016]

Embodiments of the present invention will be described below. In this example, the relationship between the rotation state of the wafer, the number of pattern defects, and the variation in pattern width was investigated using various patterns.

First, Table 1 shows the shape and dimensions of the pattern used as a sample. As shown in this table, line and space and contact hole are used as the shape of the pattern, and the size of these patterns (width of line and space or diameter of contact hole) is 0.5 to 0.8 μm.
m.

[Table 1]

Therefore, lines and spaces having such various widths are applied to the wafer after the photoresist is applied,
Alternatively, after exposing patterns of contact holes having various diameters by an ordinary i-line stepper, pure water was supplied, wafers were rotated under various conditions, and development was performed. Then, the number of pattern defects after development was measured using an image recognition type defect inspection device, and the width or diameter of the pattern was measured at 20 points within the wafer surface using a scanning electron microscope. Table 2 shows the rotation state of the wafer and the measurement result for each sample.
The width or diameter of the pattern is indicated by the variation 3σ within the wafer surface.

[Table 2]

In Table 2, all of the trial Nos. 1 to 5 are samples of this embodiment, in which the wafer rotation state is within the scope of the present invention described in the above embodiment in terms of both the rotation speed and the rotation time.
In the case of these samples, the number of pattern defects is 2 in each case.
It was confirmed that the number was as small as less than the number of wafers / wafer, and the variation 3σ in the width or diameter of the pattern within the wafer was as small as about 0.03 μm.

On the other hand, trial numbers 6 to 9 are comparative examples. Trial No. 6 is a sample in which the wafer was not rotated at all after the supply of pure water before development. Therefore, since the developing solution and a large amount of pure water remaining on the wafer are mixed and the developing solution is diluted, the variation in the pattern width becomes extremely large. In trial number 7, although the wafer was rotated, the rotation time was 7 seconds, which was beyond the range of the present invention.
It is considered that, since the number of revolutions was 2500 revolutions / minute, which was beyond the range of the present invention, the thickness of the water film was thin and bubbles adhered to the photoresist, resulting in many pattern defects. Further, in the test No. 9, the number of revolutions was 350 revolutions / minute, which was less than the range of the present invention. Therefore, it is considered that the proportion of pure water mixed with the developing solution was large and the variation in the pattern width was large.

From the above results, if the rotation time is set in the range of 0.2 seconds to 6 seconds and the rotation speed is set in the range of 600 to 2000 rotations / minute as the conditions for rotating the wafer after the supply of pure water before development,
It was demonstrated that both reduction of the number of pattern defects and improvement of the uniformity of pattern dimensions can be satisfied.

The technical scope of the present invention is not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, a specific method from developing solution coating to spin drying,
The conditions and the like can be set as appropriate.

[0023]

As described above in detail, according to the photoresist developing method of the present invention, by optimizing the conditions at the time of wafer rotation after the supply of pure water before development, the photoresist surface is coated with 20 Since a water film having a thickness of about 200 μm is formed, bubbles are in a state of floating on the water film. As a result, bubbles can be prevented from adhering to the photoresist surface, and the action of the developing solution is not weakened, so that it is possible to reduce pattern defects and improve the uniformity of pattern dimensions.

[Brief description of drawings]

FIG. 1 is a process flow diagram showing a procedure of a photoresist developing method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a range of a wafer rotation speed and a rotation time in the present invention.

FIG. 3 is a process flow diagram showing a procedure of a conventional general photoresist developing method.

FIG. 4 is a process flow diagram showing a procedure of a conventional photoresist developing method for the purpose of preventing bubbles from adhering.

Claims (1)

[Claims] 1. A photoresist is applied on a wafer, exposed, and then pure water is supplied onto the photoresist to rotate at a rotation speed of 600 to 2000 rpm for a rotation time of 0.2.
A method for developing a photoresist, characterized in that the wafer is rotated under a condition of ˜6 seconds, and then a developing solution is supplied onto the water film.