JPH07181686A - Forming method of resist pattern - Google Patents

Abstract

PURPOSE:To obtain a forming method of a resist pattern by which defects in the resist pattern due to deposition of foreign matter on a photomask can be prevented. CONSTITUTION:In the first exposure, a pattern image 61 is formed on a resist 6 by exposure with a first photomask 1 having a mask pattern 12. The resist is exposed with using a second photomask 2 having the same mask pattern 22 as that of the first photomask 1 in such a manner that the pattern image 62 to be formed in the resist 6 is matched with the pattern image 61 in the same direction. By this method, exposure is done to irradiate one area for several times. Then by developing the resist 6, the resist pattern in which production of pattern defects due to deposition of foreign matter on the photomask can be prevented is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist pattern forming method, and more particularly to a method of patterning a resist by lithography.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a resist pattern is formed on a wafer by lithography, and the wafer is subjected to various processings using the resist pattern as a mask. In the case of forming a resist pattern on a wafer by lithography, as shown in FIG.
As shown in FIG. 1, first, a photomask 3 in which a mask pattern 302 made of a light-shielding material is formed on a substrate 301 having a light-transmitting property is prepared. A resist 6 is applied on the upper surface of the wafer 5 on which a resist pattern is formed. Then, the exposure light 7 is applied to the photomask 3, and the exposure light 7 that has passed through the photomask 3 is reduced by a lens (not shown) here, and exposure is performed to form a pattern image 601 of the mask pattern 302 on the resist 6. Here, for example, when a negative resist is used as the resist 6, the crosslinking reaction of the resist 6 in the portion irradiated with the exposure light 7 proceeds. Therefore, when the foreign matter 8 is attached on the photomask 3, the exposure light 7 is not irradiated to the resist 6 in the portion where the pattern image 602 of the foreign matter 8 is formed by the exposure, and the crosslinking reaction occurs in this portion. Not proceed.

Thereafter, as shown in FIG. 3B, the exposed resist 6 is developed to form a resist pattern 300 on the wafer 5. Here, the resist in the portion not irradiated with the exposure light is removed, and the resist 6 in the portion irradiated with the exposure light and undergoing the crosslinking reaction remains on the wafer 5 as a resist pattern 300. Therefore, when the resist is exposed using the photomask on which the foreign matter is attached as described above, the resist 6 at the portion where the pattern image of the foreign matter shown by the chain double-dashed line in the figure is removed, and the resist is removed. A pattern defect occurs in the pattern 300.

In the manufacturing process of a semiconductor device, the above exposure is performed using a stepper. In this case, a wafer is placed on the stage of a stepper, and while the wafer is being moved, the exposure with a single photomask is repeated to arrange a plurality of identical pattern images on the wafer. Therefore, when the foreign matter adheres to the transfer mask as described above, the foreign matter is transferred to the same location of all patterns on the wafer, and a pattern defect occurs at the same location of all resist patterns. When wirings are formed on the wafer by using this resist pattern as a mask, wirings are short-circuited or broken at the same location of all wirings, which has a fatal influence on the yield of semiconductor devices.

Therefore, in order to prevent the defect of the resist pattern due to the adhesion of foreign matters to the photomask as described above, a method of forming a resist pattern is performed in which a transparent film called a pellicle is attached to the photomask and the resist is exposed. ing. In this method, as shown in FIG. 4A, a photomask in which a pellicle 403 is attached onto a photomask formed by forming a light-shielding mask pattern 402 on the upper surface of a substrate 401 having a light-transmitting property as described above. Prepare 4. Then, using this photomask 4, the resist 6 applied on the wafer 5 is exposed in the same manner as described above. In this exposure, even if the foreign matter 8 adheres to the photomask 4, the foreign matter 8 has a different height position from the mask pattern 402.
The pattern image of the foreign matter 8 is not formed on the resist 6. Therefore, by performing a development process as shown in FIG. 4B after the exposure, the resist pattern 400 in which the pattern defect due to the adhesion of the foreign matter on the photomask is prevented is formed.

[0006]

However, the method of forming a resist pattern using a photomask with a pellicle attached has the following problems. That is, although this method can prevent pattern defects due to foreign matter attached to the photomask after the pellicle is attached, it cannot prevent pattern defects due to foreign matter attached to the photomask before the pellicle is attached. Further, when a certain amount of foreign matter adheres to the pellicle, it is necessary to replace the pellicle. However, replacing the pellicle requires equipment and technology with high cleanliness, which is troublesome and costly. Therefore, an object of the present invention is to provide a method for forming a resist pattern that solves the above problems.

[0007]

According to the method of forming a resist pattern of the present invention made to achieve the above object,
A pattern is exposed on the resist by using a plurality of photomasks on which similar mask patterns are formed, and then the resist is developed to form a resist pattern. The overlay exposure is performed in a state where each pattern image formed on the resist by each exposure by each photomask is aligned in the same direction on the resist.

[0008]

In the above resist pattern forming method, a plurality of photomasks on which similar mask patterns are formed are used, and the pattern images formed by exposure using the respective photomasks are overlapped on the resist in the same direction. A matching exposure is performed. Therefore, the exposure at the time of lithography is performed so that the exposure light is applied to the same location a plurality of times.

[0009]

EXAMPLE A method for forming a resist pattern according to an example of the present invention will be described below with reference to FIG. First, Fig. 1 (1)
As shown in, a first photomask 1 is prepared in which a mask pattern 12 is formed on a transparent substrate 11. The mask pattern 12 is formed of a light-shielding material such as chrome, and its width w is set such that the opening width of the resist pattern formed on the wafer 5 becomes W, for example. Further, foreign matter 8 is present on the first photomask 1.
Is attached. A resist 6 is applied on the upper surface of the wafer 5 on which a resist pattern is formed. As the resist 6, for example, a negative resist is used.

Then, the exposure light 7 is applied to the first photomask 1, and the exposure light 7 that has passed through the first photomask 1 is reduced by a lens (not shown) to form a resist 6 on the wafer 5. First exposure for forming the pattern image 61 of the mask pattern 12 is performed. This first exposure is
Here, a stepper (not shown) is used, and the wafer 5 is placed on the stage of the stepper. Then, every time one pattern exposure is completed, the wafer 5 is moved, and the entire surface of the resist 6 on the wafer 5 is subjected to the first exposure using the first photomask 1.

Next, as shown in FIG. 1B, the first
A second photomask 2 in which a mask pattern 22 similar to that of the first photomask is formed on a substrate 21 similar to that of the above photomask is prepared. In the second photomask 2, the width w + Δw of the mask pattern 22 is set to the width w of the mask pattern of the first photomask plus the overlay accuracy Δw of the stepper. And the first
The second photomask 2 is irradiated with the exposure light 7 in the same manner as the second exposure, and the exposure light 7 passing through the second photomask 2 forms a pattern image 62 of the mask pattern 22 on the resist 6 on the wafer 5. Second exposure is performed. This second
The exposure is performed by superposing it on the pattern image 61 formed on the resist by the first exposure so that the pattern image 62 by the exposure using the second photomask 2 is aligned in the same direction. Further, the second exposure is performed using a stepper as in the first exposure.

Thereafter, as shown in FIG. 1C, the resist 6 is developed to form a resist pattern 10 on the wafer 5.

Since the negative resist is used in the above resist pattern forming method, the crosslinking reaction proceeds to the resist in the portion irradiated with the exposure light. For this reason,
As shown in (1), in the first exposure using the first photomask 1 with the foreign matter 8 attached, the mask pattern 12
The exposure light 7 is not applied to the resist 6 in the portion where the pattern image 61 of the foreign matter 8 and the foreign matter 8 is formed, and the resist 6 in this portion
Does not undergo a crosslinking reaction. In the second exposure shown in FIG. 1B, the first photomask 2 having the same pattern as that of the first photomask is used to perform the first exposure.
Pattern exposure is performed by superimposing it with the above exposure. Therefore, the exposure light 7 is applied to the resist in the portion where the exposure light was not applied due to the adhesion of foreign matter in the first exposure, and the crosslinking reaction of this part proceeds. Then, by performing the development processing of the resist 6 shown in FIG. 1C, the resist 6 in the portion irradiated with the exposure light in the first exposure or the second exposure remains on the wafer 5 as a resist pattern 10. The resist 6 is removed from the portion that was never exposed to the exposure light in the two exposures. Therefore, the resist pattern 10 having no pattern defect due to the adhesion of foreign matter to the first photomask is formed.

Further, FIG. 2A shows a plan view of the first photomask 1. As shown in the figure, in the first photomask 1, the foreign matter 8 is attached between the mask patterns 12. Then, in the first exposure using the first photomask 1, the resist 6 is irradiated with the exposure light as shown by the hatched portion in FIG. 2 (2), and the pattern image 61 shown by the blank portion in the drawing is formed. It is formed. Next, FIG. 2C shows a plan view of the second photomask 2 in which the same mask pattern 22 as the first photomask is formed. This second
In the second exposure using the photomask 2 of FIG.
The resist 6 is exposed to the exposure light as shown by the broken line in FIG.
A pattern image 62 shown by a white portion in the drawing is formed. The second exposure is performed so that the pattern image 62 is aligned with the pattern image 61 in the same direction. Therefore, as shown in FIG. 2C, even if the foreign matter 9 adheres to the second photomask 2, as long as the foreign matter 9 does not adhere to the same location as the foreign matter of the first photomask. By developing the above-exposed resist, a resist pattern 10 having no pattern break is formed as shown in FIG. 2 (5).

The width of the mask pattern 22 formed on the second photomask 2 is the same as that of the first photomask 1.
Is a value obtained by adding the stepping overlay accuracy Δw to the width w of the mask pattern 12. Therefore, the distance W between the resist patterns 10 is controlled by the width w of the mask pattern of the first photomask.

When the resist pattern 10 formed as described above is used as a mask to form wiring on the wafer, wiring without defects such as disconnection is formed.

In the above embodiment, the width of the mask pattern formed on the first and second photomasks is set to a value that takes into account the overlay accuracy Δw of the stepper. However, when it is not necessary to precisely control the dimensions of the resist pattern, the width of the mask pattern formed on each photomask may be set to be the same. Further, in the above embodiment,
The exposure was performed twice using the two photomasks of the first photomask and the second photomask. However, the exposure is performed multiple times using two or more photomasks. Is also good. Further, in the above-mentioned embodiment, the description is given using the negative resist. However, the present invention is not limited to this, and a positive resist may be used.

[0018]

As described above, according to the method for forming a resist pattern of the present invention, during lithography,
Overlay exposure is performed using a plurality of photomasks on which the same mask pattern is formed so that the pattern images are aligned in the same direction on the resist, so that the exposure light is applied to the same location multiple times. For this reason, it is possible to prevent defects in the resist pattern due to foreign matter adhering to the photomask. Therefore, in the manufacturing process of a semiconductor device, for example, when wiring is formed using a resist pattern as a mask, defects such as disconnection and short circuit of the wiring due to pattern defects of the resist pattern are prevented, and yield and reliability are improved. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an example.

FIG. 2 is a plan view illustrating an example.

FIG. 3 is a diagram illustrating a conventional example.

FIG. 4 is a diagram illustrating a conventional example.

[Explanation of symbols]

 1 1st photomask 2 2nd photomask 6 resist 10 resist pattern 12,22 mask pattern 61,62 pattern image

Claims (1)

[Claims] 1. A method of forming a resist pattern by subjecting a resist to overlay exposure of a pattern using a plurality of photomasks and then developing the resist, wherein the photomasks are the same as each other. And a pattern image formed on the resist by each exposure by each photomask is aligned in the same direction on the resist. Forming a resist pattern.