JPH0122725B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for forming a resist pattern in which the dimensions of elements such as photomasks, etc., on which chip patterns of semiconductor integrated circuits are formed are accurately controlled. (Technical background of the invention and its problems) With the increasing density of integrated circuits, the pattern accuracy and element dimensions of photomasks, in which the original pattern of the integrated circuit is formed on a transparent substrate as a light-shielding film, have become extremely high precision. is requested. However, when producing a photomask, various conditions are difficult to keep constant, and it is difficult to control the photoresist pattern on the submicron order. For example, the element dimensions are controlled by the sensitivity of the photoresist, the illuminance of the photorepeater, the development conditions, etc. Currently, the illuminance of the photorepeater is stable, but the other two factors are unstable. In other words, resist sensitivity changes over time.
Development conditions tend to become unstable depending on the concentration of the developer, temperature, and length of development time. Moreover, in a photomask, the integrated circuit chip pattern is not composed of one type of pattern, but is usually composed of a plurality of different types of patterns, such as a main pattern, a resist pattern, a target pattern, etc. The main pattern referred to here is a pattern corresponding to a semiconductor integrated circuit, and the resist pattern is a pattern for alignment between a plurality of photomasks used when creating an integrated circuit. Further, the target pattern is a pattern for checking the position and precision of the patterns among a large number of chip patterns provided on the photomask. The problem is complicated because it is difficult to make the conditions for creating each of these patterns constant. (Object of the Invention) The present invention is a pattern forming method devised to manage the element dimensions of a photo pattern in view of the above-mentioned problems during photomask manufacturing. (Summary of the Invention) That is, the present invention arranges a pattern group consisting of a photoresist whose exposure amount is sequentially changed for each of a plurality of different types of patterns constituting the element pattern of a photomask. Separately, a test mask is prepared by arranging independent patterns of visible size made of photoresist with sequentially different exposure doses, and the state when the test mask is set as the development end point at an appropriate rate of progress. This method of forming a pattern is characterized in that the appropriate exposure amount for each of the plurality of patterns of different types is determined from the above, and the appropriate progress of development is determined based on the independent pattern of a visually visible size. (Detailed Description of the Invention) Hereinafter, a detailed description will be given based on the drawings. FIG. 1 shows an example of a test mask 1 used in the present invention. In the figure, one side of the test mask has a main pattern 2. There is a pattern row 2a made of photoresist whose exposure amount is successively changed. For example, the main pattern 21 at the left end was printed using a photorepeater with an exposure time of 0.145 seconds, and as you move to the right, the exposure amount is increased by 0.05 seconds.
Increase by seconds in main pattern 29 on the right side
The exposure time is 0.190 seconds. For the other patterns that make up the photomask, namely register pattern 3 and target pattern 4, the exposure time is similarly changed from 0.145 seconds to 0.190 seconds from the left end to the right end.
Increase in 0.05 second increments up to seconds. Separately from the plurality of patterns of different types constituting these photomasks, independent patterns 5 of a visually visible size are arranged with the exposure amount sequentially changed. For example, if the independent pattern 5 is reproduced using a photorepeater with an exposure time of 0.110 seconds for the leftmost independent pattern 51, it is preferable to increase the exposure time to the right in steps of 0.010 seconds. Independent pattern 5 is a future development ending marker (hereinafter referred to as Development Ending Marker).
(DEM). After exposing the photoresist on the test mask 1 to form a latent image in this manner, development is performed. When developing and forming a pattern, the exposure time for each pattern is different, so the element shape of the developed resist pattern is mostly defective patterns due to underexposure or overexposure, but one of them is due to proper exposure. A good pattern can be obtained depending on the amount. Main pattern 2, the 7th from the left in Figure 1
7. The second register pattern 32 from the left and the fifth target pattern 45 from the left are shown to be good patterns as a result of pattern inspection. At this time, independent pattern 5 is 3 from the left.
Assuming that up to the th independent pattern 53 has been developed, the exposure amount of this independent pattern is 0.130 seconds, so the following relationship holds true.

[Table] In the above formula, DEM is the development end marker, and here it is shown that when the third DEM is developed, the development progress is appropriate, and each of the three different types of patterns that make up the photomask. The appropriate exposure amounts are also shown for these conditions. A photo mask is created based on the above knowledge. That is, as shown in FIG. 2, in the photomask 6, each chip pattern 7 is composed of a combination of the above-mentioned three types of patterns: main, register, and target. The appropriate exposure amount for the main pattern is 0.175 seconds, and the register pattern is 0.175 seconds based on the above formula.
Set to 0.150 seconds and target pattern to 0.165 seconds. Further, apart from these chip patterns 7, a DEM 8 corresponding to the above-mentioned independent pattern is placed. DEM8 allows you to know the appropriate development progress. That is, by terminating the development operation when the third from the left of the independent pattern group of the DEM 8 has been developed, a resist pattern in an appropriate developed state can be obtained. (Effects of the Invention) The present invention is as described above, and at the same time, it is possible to determine the optimum exposure amount for obtaining the appropriate dimensions of each pattern of main, register, and target, and at the same time, the development end marker (DEM) can also be measured in seconds. It is possible to know whether the image has been developed and to understand the relationship between the DEM and each pattern. According to the present invention, the element dimensions of a photomask can be managed in good condition, pattern defects are drastically reduced, and the effort of pattern correction is also reduced.
This is a practically excellent pattern forming method.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of a test mask suitable for performing the resist pattern creation method of the present invention, and FIG. 2 is a plan view showing an example of a photomask when the method of the present invention is applied to the photomask. It is a diagram. 1...Test mask, 2...Main pattern,
3...Register pattern, 4...Target pattern, 5...Independent pattern, 6...Photomask, 7...Chip pattern, 8...DEM.

Claims (1)

[Claims] 1. A pattern group consisting of photoresist whose exposure amount was sequentially changed was arranged for each of the plurality of different types of patterns constituting the element pattern of the photomask, and apart from these, the exposure amount was also sequentially changed. A test mask is prepared by arranging independent patterns of visible size made of photoresist, and each of the plurality of different types of patterns is determined from the state when the test mask is set as the development end point at an appropriate rate of progress. 1. A method for forming a pattern, comprising: determining an appropriate exposure amount for the image, and determining an appropriate degree of development based on the independent pattern of a visible size.