JPH0442816B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to photomask blanks in which a light-shielding thin film is coated on a light-transmitting substrate, and oxidized film on a semiconductor substrate such as a silicon wafer, in a semiconductor process, for example. A method for manufacturing an illuminance correction plate used as an accessory for an exposure device used when forming a predetermined pattern on a photoresist after applying a photoresist to an original plate, such as a substrate coated with a material film or a conductive film. Regarding.

[Conventional technology]

Conventionally, in this type of exposure equipment, an optical system such as an integrator or collimator lens is generally placed on the optical path between the light source and the original plate, and the light emitted from the light source lamp is collimated by these optical systems. The photoresist is applied to the substrate coated with photoresist, and then irradiated through the original plate. In this case, a position adjustment knob is usually provided at the mounting location of the light source lamp, so that the optical axis can be adjusted.

[Problem that the invention seeks to solve]

However, the integrator, collimator lens, etc. mentioned above are not made especially for the device, and for example, if there is a slight unevenness in the illuminance distribution that is unique to each device, they can be used to make it uniform, or to make it more uniform. It does not have an adjustment function to further emphasize.

[Means for Solving the Problems] In order to solve these problems, the method for manufacturing an illuminance correction plate for an exposure apparatus according to the present invention includes a method for manufacturing an illuminance correction plate for an exposure apparatus, in which a light-shielding plate is provided on the main surface on the optical path between the light source and the substrate to be exposed. A transparent substrate laminated with a transparent thin film and a photoresist and a contact screen are arranged with the latter facing the light source side, and a halftone screen reflecting the illuminance distribution on the main surface is created by lithography and etching to adjust the illuminance. A correction plate or a halftone screen obtained in this way and a second light-transmitting substrate on which a light-shielding thin film and a photoresist are laminated on the main surface are placed on the optical path with the former facing the light source. Then, by performing lithography and etching again, an inverted pattern of the halftone dot screen is formed on the light-shielding thin film, and this second light-transmitting substrate is used as an illuminance correction plate.

[Effect]

In photolithography, by using a contact screen used for mesh resolution to reproduce the continuous tone density of an image, it is possible to easily form a halftone screen with a density that reflects the illuminance distribution. By using different photoresists and further reversing the halftone dot pattern once formed, it is possible to create a positive or negative correlation between the illuminance distribution and the density distribution of the light-shielding portion, depending on the purpose.

By placing a correction plate on the optical path in which light shielding parts are distributed at a density that has a positive correlation with the illuminance distribution, unevenness in the illuminance distribution can be offset. , it is possible to further emphasize the non-uniformity of the illuminance distribution.

〔Example〕

FIG. 1 is a block diagram of an exposure apparatus showing an embodiment of the present invention. In the figure, 1 is a light source lamp that emits ultraviolet or far ultraviolet light such as an ultra-high pressure mercury lamp or a Xe-Hg lamp, 2 is a condensing mirror coated with _MgF2 , and 3 is a light source that transmits light in the infrared or visible range. It is a cold mirror that reflects light in the ultraviolet region. The reflected light passes through an integrator 4, which is a collection plate of small convex lenses, and is made into a parallel beam.The light is then reflected by a collimator lens 5, which is a concave mirror, to become a parallel beam, and then reflected by a reflecting mirror 6. The light passes through an original plate 7 such as a photomask, and reaches the main surface of a material substrate 8, which is a substrate to be exposed and coated with a photoresist. At this time, an illuminance correction plate 9 is placed just in front of the original plate 7, and the illumination distribution of the collimated light is adjusted by the correction plate 9, and the illuminance distribution is incident on the original plate 8.

Here, the illuminance correction plate 9 has a rectangular plate shape as shown in FIG. 2a, and as shown in FIG. This chromium film 92 is formed selectively, but as shown in the plan view of part A in Fig. 3a, part B in Fig. 3b, and part C in Fig. 3c, the center part is It is densely formed and coarser towards the periphery. This embodiment is arranged to correct and make uniform the illuminance distribution of light incident on the correction plate 9, for example, when it is high at the center and low at the periphery, as shown in FIG. , its transmittance has a distribution that has a negative correlation with the illuminance distribution as shown in FIG.
As shown in the figure, variations in illuminance are removed and a uniform distribution is obtained.

This illuminance correction plate 9 is similar to a halftone screen used in photolithography, and is manufactured using a contact screen, which is a type of halftone screen, in the following manner.

As shown in Fig. 7, a contact screen is a two-dimensional lattice formed on a soft film in which halftone dots with the same optical density distribution are arranged. As shown by the broken line in Figure 8, the optical density distribution reaches its maximum at the intersection of the lattice and continuously decreases toward the periphery, and as shown by the solid line in the figure. The structure is such that the transmittance is maximum at the center of each square and continuously decreases toward the periphery, so the transmission area in each square varies depending on the intensity of light, and this is used. This allows the illuminance of the light to be converted into a transmission area. The number of grids is typically 85 to 200 grids per inch.
In the case of 85 lines, the grid spacing is approximately 0.3 mm. It goes without saying that the smaller the interval, the more faithfully the illuminance distribution can be captured, but this interval should be selected as appropriate.
Note that a glass substrate may be used instead of the soft film.

For example, as shown in FIG.
A negative type photoresist 93 (for example, Tokyo Ohka Kogyo's OMR-83) is further coated on the mask blank on which 2 has been coated on the entire surface, and this contact screen 10 is placed on top of the mask blank and is held down with a dummy glass 94 made of quartz glass. It is placed at the position of the correction plate 9 in FIG. 1 and exposed (FIG. 9a). In the exposure of this embodiment, since the illuminance is higher in the center, the transmission area of each square of the contact screen 10 becomes larger in the center. b),
By peeling off the resist 93 that is no longer needed, a correction plate 9 having halftone dots made of a chromium film 92 formed on a glass substrate 91 as shown in FIGS. 2 and 3 is completed.

In FIG. 1, the original plate 7 is, for example, a transparent glass substrate 71 on which a chromium film 72 of a desired pattern is formed, as shown in FIG. membrane 82
The photoresist 83 is coated on the entire surface and a photoresist 83 is applied thereon.The photoresist 83 is exposed to light transmitted through the light-transmitting part of the original plate 7, and if it is a negative type resist, the photoresist 83 is exposed by development and etching. The pattern of the chrome film 72 is inverted and transferred to the chrome film 82, while only the pattern of the chrome film 72 is transferred to the chrome film 82.On the other hand, if it is a positive type resist, the exposed part is removed, so the pattern of the chrome film 72 is transferred to the chrome film 82.
2 is transferred as is. At this time, in reality, the light that has passed through the light-transmitting part of the original plate 7 wraps around to the light-shielding part as shown in the figure, but reaches the critical illuminance at positions A and F in the figure, and below the critical illuminance inward. If the design is made so that the chromium film 7
Pattern 2 can be faithfully reproduced.

However, as mentioned above, if the illuminance happens to vary due to the influence of the optical system, etc., in the part where the illuminance is higher than the design value mentioned above, for example, B or E mentioned above.
However, if the illumination exceeds the critical illuminance and is exposed, if a positive type resist is used, the line width of the pattern will be smaller than the design value in that area, and conversely, if a negative type resist is used, it will become larger and the line width will be smaller than the design value. There will be variations in width.

On the other hand, by inserting the correction plate 9 which has been prepared in advance by the method described above, the non-uniformity of the illuminance distribution can be eliminated, and therefore the variation in line width can be suppressed.

Conversely, if the illuminance at the center is low, the line width will be large in the center if a positive type resist is used, and it will be small if a negative type resist is used. By using a positive type photoresist (for example, Hoechst's MP-1350) and using the same process as described above, a chromium film 9 is formed which is coarse in the center and dense in the periphery.
It is sufficient to prepare a correction plate 9 on which 2 is attached and interpose this.

By the way, when a projection exposure method is used without requiring a very high resolution, or when using a contact exposure method, the original plate 7 and the material substrate 8 are brought into almost complete contact with each other to maintain their parallelism and flatness. In some cases, only non-uniform illuminance distribution should be considered as a case where line width varies; however, even if the illuminance distribution is uniform, variation in line width may occur. That is, when a positive type photoresist is used in a contact exposure method, the photosensitive component of the resist, such as quinone diazide, decomposes due to the exposure and generates _N2 gas, and the pressure causes at least one of the original plate 7 and the material substrate 8 to become It may be curved as shown in FIG. In such a case, the distance between the original plate 7 and the material substrate 8 is large at the center and becomes smaller toward the periphery. Therefore, even if the illuminance distribution is uniform, the illuminance distribution on the material substrate 8 is not necessarily uniform due to the amount of wraparound due to diffraction, and the longer the distance from the original plate 7 is, the line width becomes larger. In such a case, rather, the illuminance distribution should be actively made non-uniform, that is, the illuminance in the center should be made higher than in the peripheral areas, and the resulting line width reduction effect would cause the above-mentioned curvature. It is necessary to cancel out the effect of line width expansion, but in this case, the illuminance distribution is uniform, so it is not possible to create a correction plate by simply using the non-uniformity of the illuminance distribution as described above. Can not.

Furthermore, in the development or etching process after exposure, for example, when a developer or etching solution is sprayed while rotating the material substrate 8 with a spinner, the development or etching progresses closer to the center, resulting in the line width decreasing. The distribution may be larger at the center and smaller at the periphery, or vice versa. In this case as well, in order to finally obtain a uniform line width, it is necessary to actively make the illuminance distribution non-uniform.

To summarize the above, when correction is necessary, you want to correct the illuminance in the center to be lower than the peripheral area, that is, in the positive type resist process, the chrome film line width in the center becomes smaller and you want to correct this. There are cases like this, and cases where you want to correct the illuminance in the center to be higher than the peripheral areas, that is, cases where you want to correct the chrome film line width in the center that becomes large in the positive resist process. In each case, the illuminance is uniform, the illuminance is high in the center, and the illuminance in the center is low.

In the case of - above, the correction plate can be created by inversely utilizing the curvature phenomenon caused by gas in contact exposure using a positive type resist as described above. That is, as shown in FIG. 12, for example, a blank in which a chromium film 92A is deposited on the main surface of a transparent glass substrate 91A and a positive type resist 93P is applied thereto and a contact screen 10 are placed, with the latter facing the light source. By placing it on the optical path, exposing it to light, and then developing and etching it, a correction plate 9A having a large area of the chromium film 92A at the center can be formed.

In the case of -, as shown in FIG. 13, a blank coated with a negative type resist 93N is used to obtain a correction plate 9A in which the area of the chromium film 92A in the center is large.

On the other hand, in the case of -, a similar correction plate 9A can be obtained by using a blank coated with a positive type resist 93P as shown in FIG.

On the other hand, in the case of -, the pattern of the correction plate made in - to above is reversed. In other words, the first
As shown in FIG. 5, a blank in which a chromium film 92B is coated on the main surface of a translucent glass substrate 91B and a negative type resist 93N is applied and the correction plate 9A are placed on the optical path with the latter facing the light source. By placing the chromium film 92B in the center and exposing it to light, a correction plate 9B can be formed in which the area of the chromium film 92B in the center is small. As mentioned above, in the positive resist process, when line width variations occur due to curvature caused by gas despite the uniform illuminance distribution, halftone dots with similar variations can be obtained using the method described above. By forming a screen and inverting it in the manner described above, the desired correction plate can be formed.

In the case of -, a positive type resist 93P is used as shown in Fig. 16 in the same way as in the - case, and in the case of -, a negative type resist 93N is used as shown in Fig. 17. In the same manner as above, remove the chromium film 9 at the center.
A correction plate 9B having a small area of 2B can be obtained.

In addition to the above-mentioned MP1350 (Hoechst), there are also other positive type resistors, such as
Kodakposi, OFPR (Tokyo Ohka Kogyo)
etc. may also be used. Similarly, for negative type resists, in addition to the above-mentioned OMR-83 (Tokyo Ohka Kogyo), KMR-747 (Kodatsu Co., Ltd.), Selectirax-N (EM Chemical Co., Ltd.), and others can be used. In addition to the above-mentioned chromium, materials for the light shielding part include nickel, aluminum, titanium, iron, cobalt, zirconium,
Germanium, tantalum, molybdenum, etc. are preferred, and various alloys such as nichrome, chrome cermet, nickel silicon, stainless steel,
Titanium silicon can also be used. Further, oxides, nitrides, carbides, etc. of these can also be used.

By inserting each type of correction plate obtained in this way onto the optical path as shown in Figure 1, various corrections or adjustment illuminance distributions can be made by combining with the original illuminance distribution of the exposure device before correction. can get. This is shown in FIGS. 18 to 20. In each figure, A is the illuminance distribution before correction, and a-
shows the illuminance distribution when the illuminance is uniform, a- in FIG. 19A shows the illuminance distribution when the illuminance at the center is high, and a- in FIG. 20A shows the illuminance distribution when the illuminance at the center is low. Also, each figure B, D, F is the transmittance distribution of the correction plate, and b of each figure B
- indicates a correction plate with low transmittance at the center, i.e., the above-mentioned type of correction plate; b- in each figure D indicates a correction plate with high transmittance at the center; b- in each figure F indicates transmittance at the center. b- shows a transmittance distribution of a new type of correction plate in which the transmittance is lower than b-, and b- shows a transmittance distribution of a new type of correction plate in which the center transmittance is higher than b-. And each figure C, E, G
is the illuminance distribution after correction, and c- in each figure C is b-
When using a correction plate, c- in each figure E becomes b-
When using a correction plate, c- in each figure G becomes b-
The illuminance distribution is shown when a correction plate of c- is used and a correction plate of b- is used.

It was mentioned earlier that variations in line width also occur due to development and etching processes. Further, even if the illuminance is the same, the amount of exposure light that actually contributes to exposure differs depending on the exposure time. This means, on the contrary,
This means that by adjusting these, it is possible to match the final line width. For example, even when using a correction plate with a high transmittance distribution in the center as shown in Figure 21 in order to increase the illuminance in the center, the range of change in transmittance is set to B ₁ in a in Figure 21. B ₂ in FIG.

Further, in the example shown in FIG. 1, the correction plate 9 is placed immediately in front of the original plate 7. This is not particularly limited to this, and it may be inserted anywhere on the optical path from the light source lamp 1 to the original plate 7, but if there are factors that make the illumination uneven in the optical system, their influence This is because it is most effective to perform the correction immediately before the original plate 7 where all of the images are displayed.

In addition, although FIG. 1 shows a case where the original plate 7 and the material substrate 8 are arranged in a horizontal direction and light is irradiated from the vertical direction, it is also possible to arrange the original plate 7 and the material substrate 8 in a vertical direction and The present invention can be applied in exactly the same manner to an exposure apparatus having a structure that irradiates light from any direction.

[Effects of the Invention] As explained above, according to the present invention, by using a contact screen, the illuminance distribution on the main surface of the substrate to be exposed when there is no correction plate on the main surface of the transparent substrate can be adjusted. Since it is possible to obtain an illuminance correction plate with light-blocking parts distributed at correlated densities,
It is possible to eliminate the non-uniformity of the illuminance distribution inherent in the exposure apparatus, or to adjust the distribution to an appropriate one according to a specific purpose.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an exposure apparatus used in an embodiment of the present invention, FIG.
3 is a detailed view of FIG. 2a, FIG. 4 is a diagram showing an example of the illuminance distribution before correction, FIG. 5 is a diagram showing an example of the transmittance distribution of the correction plate, and FIG. A diagram showing an example of the illuminance distribution after correction, FIG. 7 is a plan view showing an example of the structure of a contact screen, FIG. 8 is a diagram showing its transmittance distribution, and FIG. 9 is a process diagram showing an example of the present invention. 10 and 11 are sectional views for explaining the principle of pattern transfer, and FIGS. 12 to 17 are sectional views and 18 to 17 for explaining other embodiments of the present invention, respectively. FIG. 20 is a diagram showing the effect of the correction plate, and FIG. 21 is a diagram for explaining a method of designing the transmittance distribution of the correction plate. 1... Light source lamp, 7... Original plate, 8... Material substrate, 9, 9A, 9B... Illuminance correction plate, 10... Contact screen, 71, 81, 91... Transparent glass substrate, 72, 82 ,92...Chromium film,
83, 93...Photoresist, 93N...Negative type photoresist, 93P...Positive type photoresist.

Claims (1)

[Scope of Claims] 1. In a method for manufacturing an illuminance correction plate for an exposure apparatus, which includes a light source and an optical system that irradiates a substrate to be exposed with light emitted from the light source, an optical path between the light source and the substrate to be exposed is provided. A process of arranging and exposing a light-transmitting substrate with a light-shielding thin film and a photoresist laminated on its main surface and a contact screen with the contact screen facing the light source, and after development, using the remaining photoresist as a mask to remove the light-shielding property. 1. A method of manufacturing an illuminance correction plate for an exposure device, comprising the step of etching a thin film to form a halftone screen. 2. In a method for manufacturing an illuminance correction plate for an exposure apparatus, which is equipped with a light source and an optical system that irradiates the substrate to be exposed with the light emitted from the light source, a light-shielding plate is provided on the main surface on the optical path between the light source and the substrate to be exposed. The light-shielding thin film and photoresist are laminated together on a transparent substrate and a contact screen, which are exposed to light with the contact screen facing the light source, and after development, the remaining photoresist is used as a mask to etch the light-shielding thin film and form a net creating a point screen;
A second light-transmitting substrate having a second light-shielding thin film and a second photoresist laminated on its main surface and the halftone screen are placed on the optical path with the halftone screen facing the light source and exposed. A method for manufacturing an illuminance correction plate for an exposure apparatus, comprising the steps of: etching the second light-shielding thin film using the remaining second photoresist as a mask after development.