JPS6347924A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable the formation of patterns of uniform dimensions, to make uniform the characteristics of semiconductor devices manufactured, and to attain an improvement in the reliability and manufacturing yield thereof, by a method wherein the quantity of exposure of a necessary pattern to a photoresist is made different in accordance with plane positions of a semiconductor wafer. CONSTITUTION:A photoresist is applied on a semiconductor wafer 1, exposed in a necessary pattern and developed to form a photoresist mask. A ground film is etched by using this mask. The exposure for the photoresist pattern in this process is varied in accordance with surface positions of the semiconductor wafer 1. For instance, a polycrystalline silicon film 3 is formed on a silicon oxide film 2 on the surface of the semiconductor wafer 1, and a positive photoresist 4 is applied on the film 3. Then, the wafer is exposed in such a manner that the time of exposure is longer toward its center than its peripheral, so that the sizes of the individual chip patterns of a developed photoresist 4 become smaller as they are positioned nearer to the center.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a semiconductor device in which patterning using photolithography can be uniformly performed over the entire surface of a wafer.

C. Prior Art] Conventionally, in the manufacturing process of forming semiconductor devices on a semiconductor wafer, required patterning is often performed by a photolithography process using a photoresist. Normally, in this photolithography process, a photoresist is coated on a film of polycrystalline silicon, metal, etc. formed on the surface of a semiconductor wafer, and a desired pattern is exposed to light on the photoresist, which is then developed to form the desired pattern. Shape. Then, using this as a mask, a process such as plasma etching is performed on films of polycrystalline silicon, metal, etc., and this etching is used to form these films into a desired pattern.

[Problem that the invention seeks to solve]

In the conventional photolithography process described above, when exposing the photoresist, the entire surface of the wafer is usually exposed with a uniform exposure amount.

For this reason, due to variations in the film thickness of the photoresist coated on the wafer and variations in the development speed that occur during the development of the photoresist, the photoresist pattern after development may vary in position on the wafer surface. Dimensional variations corresponding to the differences often occur. Further, due to the etching characteristic that starts from the periphery of the wafer, etching progresses at the periphery of the wafer more than at the center.

For this reason, due to variations in film thickness, development speed, and processing speed, variations in the dimensions of polycrystalline silicon, metal, and other film patterns formed by etching occur, resulting in multiple This leads to non-uniformity in the characteristics of semiconductor devices in the 1,000-knob pattern, leading to problems such as a decrease in reliability and manufacturing yield.

For example, FIGS. 4(a) and 4(b) are plan views of a state in which a plurality of chip patterns 5 are exposed on a semiconductor wafer 1 using the conventional method described above, and the dimensions of each pattern arranged in the horizontal direction of the figure are compared. From this figure, it can be seen that the pattern size at the center of the wafer is larger than the pattern size at the periphery of the wafer, causing variations in pattern size.

[Means for Solving the Problems] The semiconductor device manufacturing method of the present invention eliminates variations in pattern dimensions in the photolithography process, enables pattern formation with uniform dimensions, and uniformizes the characteristics of the manufactured semiconductor device. The aim is to achieve improvements in reliability and manufacturing yield.

The method for manufacturing a semiconductor device of the present invention includes exposing a photoresist coated on a semiconductor wafer to a required pattern and developing it to form a photoresist mask;
When etching the base film using this mask, the amount of exposure of the required pattern on the photoresist is varied depending on the planar position of the semiconductor wafer.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example 1) FIG. 1(a) is a diagram showing a first example of the present invention, in which a plurality of chip patterns are exposed on a semiconductor wafer 1 by a step-and-repeat method. .

As shown in FIG. 2, the semiconductor wafer 1 has a structure in which a polycrystalline silicon film 3 is formed on a silicon oxide film 2 on the surface of the semiconductor wafer 1, and a positive photoresist 4 is applied thereon. .

Then, the required chip patterns 5 are sequentially exposed one by one on this photoresist 4 by a step-and-repeat method using a reduction type projection exposure apparatus (not shown).

At this time, in this embodiment, exposure is performed such that the exposure time of the chip pattern on the center side of the semiconductor wafer is longer than that of the chip pattern on the peripheral side. Here, the exposure time is set to 200 m5 ec for the central chip pattern 5a, 225 m5 ec for the surrounding chip pattern 5b, and 250 m5 ec for the peripheral chip pattern 5C.

By varying the exposure time in this way, the photoresist 4 after development is greatly influenced by the exposure time, which is a larger factor than the photoresist film thickness, development speed, etc., and the pattern on the center side with a longer exposure time is more affected by the photoresist 4. The pattern size becomes small. Therefore, when etching the polycrystalline silicon film 3 using this photoresist as a mask,
Despite variations in etching speed due to etching progressing from the periphery of the wafer, this etching speed and the difference in pattern size are offset, resulting in etching with uniform dimensions over the entire surface of the wafer. That will happen.

FIG. 1(b) is a diagram showing the results, showing the dimensions of each pattern arranged in the horizontal direction of FIG. I understand that.

(Embodiment 2) FIG. 3 is a diagram showing a second embodiment of the present invention, in which an example is shown in which a chip pattern is exposed by a batch exposure method.

During this exposure, the photomask 6 is kept in constant contact with the semiconductor wafer 1, as shown in FIG. Exposure is being performed. At this time, a filter 7 is interposed between the light source and the photomask 6, and the amount of exposure to the semiconductor wafer 1 is varied depending on the planar position. This filter 7 has a transmission characteristic such that the transmittance at the center is concentrically higher than the transmittance at the periphery as shown in FIG. 100%, and the transmittance of the surrounding portion 7b is 90%.
The transmittance of each peripheral portion 7c is set to 80%.

Therefore, when exposure is performed through this filter 7, the chip pattern 5 at the center of the wafer 1 is exposed as shown in FIG.
Exposure is performed in a state where the amount of exposure is gradually decreased from a toward the chip pattern 5C in the peripheral area.

As a result, the pattern size of the photoresist 4 at the center is reduced as in the first embodiment, and therefore the pattern size of the polycrystalline silicon film 3 formed by etching using this photoresist as a mask covers the entire surface of the wafer. They will be approximately equal to each other.

In each of the above embodiments, a positive photoresist is used, but when a negative photoresist is used, the amount of exposure at the center may be lower than that at the periphery. Further, the filter 7 used in the second embodiment may be configured such that the transmittance is continuously changed from the center to the periphery.

〔Effect of the invention〕

As explained above, in the present invention, since the exposure amount of the pattern is varied depending on the planar position of the semiconductor wafer, the pattern dimensions of the developed photoresist can be correspondingly varied. A pattern with substantially uniform dimensions can be formed over the entire surface of a semiconductor wafer regardless of variations in etching speed using a photoresist as a mask. This makes it possible to uniformly improve the characteristics of a plurality of chips formed on a semiconductor wafer, thereby achieving improved reliability and yield.

[Brief explanation of drawings]

Fig. 1 shows a first embodiment of the present invention, Fig. 1(a) is a plan view of a wafer showing the exposure state, Fig. 1(b) is a characteristic diagram of the dimensions of each pattern arranged in the horizontal direction, and Fig. 2 is a A sectional view of a wafer, FIG. 3 shows a second embodiment of the present invention, FIG. 3(a) is a schematic sectional view showing an exposure state, and FIG. ) is a plan view of the wafer showing the exposure state;
The figure shows a conventional method, where (a) is a plan view of a wafer in an exposed state, and (b) is a characteristic diagram of the dimensions of each pattern arranged in the horizontal direction. 1... Half body wafer, 2... Silicon oxide film, 3...
... Polycrystalline silicon film, 4... Photoresist, 5 (
5a. 5b, 5c)...Chip pattern, 6...Photomask, 7 (7a, 7b, 7c) -=
filter. Agent Patent Attorney Akira Suzuki Mistakes Figure 1 (b) 1 芥 Center / Textbook Figure 3 Complete Figure 4 (b) 婢 Ki,. cicada

Claims (2)

[Claims] (1) At least a step of coating and forming a photoresist on a semiconductor wafer, a step of exposing the photoresist in a required pattern and developing it to form a photoresist mask, and a step of forming a photoresist mask using this mask. A method for manufacturing a semiconductor device including a step of etching a base film, characterized in that the amount of exposure of the required pattern on the photoresist is varied depending on the planar position of the semiconductor wafer. (2) The method of manufacturing a semiconductor device according to claim 1, wherein a positive type photoresist is used and the amount of exposure at the center of the wafer is larger than at the periphery.