JPS5914892B2 - Pattern formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of patterning using lithography.

First, a conventional pattern forming method using photolithography will be explained.

FIGS. 1a and 1b are cross-sectional views for explaining a conventional photolithography method.

In the conventional pattern forming method, as shown in FIG. The coating is coated with light 5 having a certain wavelength from a light source (not shown).

The photoresist layer 3 in the transparent part of the photomask 4 is exposed to light,
This is done by leaving the uncovered portion of the photomask and etching it as pattern 6. In this case, in order to etch the desired pattern 6 on the photoresist layer 3, the exposure amount of the exposure light needs to be the optimum condition for exposure of the photoresist layer 3, that is, the appropriate exposure amount. Only when the photoresist is exposed with this appropriate amount of light, a pattern similar to the designed pattern is precisely etched into the photoresist, and a predetermined pattern is obtained. If the exposure amount deviates from the appropriate exposure amount, that is, if the exposure amount is too high, it will be overexposed, and if it is less than 10, it will be underexposure, and the resulting pattern 6 will have blurring or blurring, making it impossible to obtain a precise pattern. . As described above, the conventional pattern exposure method has the drawback that exposure is performed under exposure conditions with an appropriate amount of exposure, and that only a 15-pattern pattern, which is the same as the photomask pattern used, can be obtained. Furthermore, in conventional exposure methods, if the material to be processed has a concave portion or a difference in film thickness in the photoresist layer, it is difficult to determine the appropriate exposure amount for the exposure conditions during pattern formation. This method also has the disadvantage that it is difficult to obtain a precise pattern. For example, when there is a recess on the surface of the workpiece material, if photoresist is applied to the surface of the workpiece material using a conventional coating method, the thickness of the applied photoresist film will be The concave part is thick,
Areas other than the recessed areas are coated thinner than the recessed areas.

The present invention is intended to eliminate the above-mentioned conventional drawbacks, and its purpose is to utilize the difference in film thickness of photoresist to obtain a pattern completely different from the photomask pattern when using a photomask. It is an object of the present invention to provide a pattern forming method in which a region exposed with an appropriate amount of light can be obtained as a selected pattern even when the present invention is not used.

The present invention will be described in detail below with reference to the drawings.

FIGS. 2a and 2b are cross-sectional views for explaining an example of the pattern forming method of the present invention.

The workpiece material 1 has a concave portion 8 on one surface 2 having a substantially U-shaped cross section.

The pattern forming method of the present invention begins by coating a photoresist 3 on the surface of a workpiece material 1 having recesses 8 as shown in FIG. 2a. The thickness of the photoresist 3 is applied so that the portion located above the recessed portion 8 is thicker than the thickness of the flat portion.

Next, the photoresist 3 is covered with a photomask 4 at a position where at least a portion of the recess 8 is covered, and a light source (not shown) is used.
Light 7 having a certain wavelength is irradiated with an appropriate exposure amount. As a result, as shown in FIG. 2b, the photoresist 3 has a portion 9' exposed at the appropriate exposure amount and a portion 9 exposed at less than the appropriate exposure amount, as shown in FIG. A pattern can be formed. That is, a pattern completely different from the pattern 4 used after the development process is obtained. The above example is one in which a photomask is used, but next, an example in which a photomask is not used will be described.

The workpiece material 1 has a shape similar to that shown in FIG. 2a.

As shown in Fig. 3 AVC, one main surface 2 of the workpiece material 1
When a 1IC photoresist 3 is applied and the photoresist 3 is irradiated with light 7 without using a photomask until it reaches an appropriate exposure level, either once or at least multiple times, the photoresist 3 will be exposed as a photosensitive area at an appropriate exposure level, as shown in FIG. An exposed portion 10'' and a portion 10 exposed to less than the appropriate exposure amount are created, and a pattern can be formed in which the portion 10'' exposed to the appropriate exposure amount is open. Note that although the contact exposure method has been described as an explanation of the case where a photomask is used, the same applies to the projection exposure method, so the explanation will be omitted.

Next, the method of the present invention will be explained in more detail using an example in which a positive type resist is used.

In the example shown in Fig. 2 AVC, one main surface 2 has a width of 20 mm.
A photoresist (AZ-1350 (product name)) 3 is applied to the surface 2 of the workpiece material 1 having a recess 8 with a depth of 5 μm and 6000A1 for the parts other than the recess to 54000A for the recess 8.
Apply A.

Next, a part of the recess 8 is covered using a photomask 4, and the light 7 using a mercury lamp as a parallel beam is irradiated for 6 seconds, followed by development. The concave portions are not dissolved in the developer because the exposure amount is less than the appropriate amount, and a pattern 9 shown in FIG. 2b can be formed. As a result, a pattern completely different from that of the photomask used is formed due to the inclusion of recesses. Next, one surface 2 of the workpiece material 1 has a width of 20 μm and a depth of 5 μm.
A photoresist 3 of 6,000 A is coated on the surface 2 including the concave portions 8, and a photoresist of 54,000 A is coated on the concave portions.The surface of FIG. conduct.

As a result, as shown in FIG. 3 BVC, the photoresist 3 on one surface 2 of the workpiece material 1 is exposed, and the portion of the recess 8 in the surface 2 is exposed only halfway due to the thick film of the photoresist 3. The pattern 10 is etched. This means that even though the entire surface of the material 1 to be processed is irradiated with the light 7, the etched pattern remains in the resist with a width of 20 ftm, and the pattern can be obtained without a photomask. Even once, the energy of the irradiated light sensitizes the photoresist 3 in the thick and thin parts.
Further, a pattern is formed by performing at least a plurality of exposures.
The result shows that the time for irradiating the light 7 can be divided into the number of times required to create a pattern of the desired shape, in which case the photoresist 3 is completely exposed, regardless of whether a photomask 4 is used or not. It has been obtained. Although the case of a positive type resist has been explained above as an example, the same result can be obtained with a negative type resist, so the explanation will be omitted. As explained above, in the mask exposure method of the present invention, a pattern is etched through a process of performing exposure once or at least multiple times until an appropriate exposure amount is reached by utilizing the difference in film thickness of the photoresist. The type and number of photomasks that were required, and the production time and cost that go through the complicated process of manufacturing photomasks, have been reduced. It has great industrial value because it can be applied to light exposure, electron beam exposure, etc.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1A and 1B are diagrams for explaining a conventional photolithography method, and FIGS. It is a figure for explaining an example.

Claims (1)

[Claims] 1. A step of applying photoresist to the surface of the workpiece material having recesses on the surface so that the thickness of the photoresist on the recesses is thicker than that of the photoresist in other parts, and applying an appropriate exposure amount to the photoresist in the thin parts. For the photoresist in the thick part, there is a step of exposing an area partially including the recesses with a light amount less than the appropriate exposure amount, and a step of developing only the area of the photoresist that has been exposed with the appropriate exposure amount as a selected pattern. A pattern forming method comprising: