JP2892014B2 - Light exposure mask and exposure method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a light exposure mask and an exposure method using the same. The present invention, for example, in the manufacture of semiconductor devices,
It can be used when performing pattern transfer.

[Summary of the Invention]

According to the present invention, for an exposure mask having a mask pattern, at least a part of an opposing portion of an adjacent pattern portion adjacent to each other, the light intensity is reduced to a projection pattern between the adjacent patterns. The adjacent masks due to the distortion of the light intensity distribution by providing a notch portion having a corner portion in an inner direction portion of the notched pattern to prevent the occurrence of a portion. The light intensity between the patterns is prevented from lowering, and a shape faithful to the patterns can be obtained.

[Conventional technology]

The light exposure mask is used, for example, in a manufacturing process of a semiconductor device to transfer a mask pattern formed on the mask to a photoresist to form a resist pattern. However, with the recent trend toward ultra-miniaturization and high integration of semiconductor devices, even higher precision is required for transfer of mask patterns.

For example, recently, in the photolithography process for VLSI manufacturing, it has been necessary to stably and accurately form fine resist patterns close to the diffraction limit of the optical system of exposure equipment, and even finer patterns than the diffraction limit. It is becoming necessary.

2. Description of the Related Art Conventionally, as an exposure apparatus for photolithography, a method of projecting and exposing a pattern of a mask onto a resist film or the like on a wafer, which is a substrate to which a pattern is to be transferred, mainly through a lens or a mirror has been used. .
Generally, the pattern on this type of light exposure mask is formed of a rectangular pattern, but the light intensity distribution projected on a substrate (wafer or the like) that plays a role in determining the shape of a resist film or the like is based on light diffraction and interference. For example, when the pattern dimension approaches the diffraction limit of the optical system, the fidelity to the mask is lost. That is, in one part, the corners of the rectangular pattern are projected in a remarkably rounded shape. On the other hand, the projected pattern is distorted. When the resist is exposed with such a light intensity distribution, the resist pattern after development becomes
Reflecting the light intensity distribution, the corners are rounded. In addition, distortion occurs. Therefore, a fine resist pattern cannot be faithfully formed on the mask.

Of the above problems, it is naturally desirable that the roundness at the corners be faithful to the mask pattern,
It does not always produce a decisive disadvantage. However, the distortion of the resist pattern may significantly impair the reliability of the semiconductor device to be manufactured. This problem is particularly serious when using a light exposure mask having a plurality of mask patterns which are close to each other and are mutually adjacent.

Such a problem will be described below with reference to FIGS. 3 and 4.

FIG. 3 shows a light exposure mask having two rectangular patterns 1 'and 2' adjacent and adjacent to each other, and the two patterns 1 'and 2' are adjacent to each other at a distance l. This l
Is, for example, 0.7μ or 0.6μ, when this is exposed by a projection exposure apparatus having a resolution of 0.8μ, for example, as shown in FIG. The light intensity distribution is distorted in the vicinity of the corner, and a portion where the light intensity is remarkably reduced occurs in the projected portion corresponding to the groove between the patterns 1 'and 2'. This portion is indicated by A in FIG. FIG. 4 is a light intensity distribution diagram corresponding to a portion surrounded by a broken line in FIG.

As described above, when a portion having a low light intensity is formed in a part of the fine groove-shaped pattern (punched pattern) due to the influence of the pattern distortion, the resist often remains in the portion after the resist development. For example, as schematically shown in FIG. 5, the light intensity distribution may cause contact of the resist due to the remaining resist at a portion indicated by reference numeral B in the figure. If the subsequent processing is performed as it is, a semiconductor device obtained will be obtained. Is not as designed and the reliability is significantly reduced. As described above, in the state of the projection intensity distribution as shown in FIG. 4, a fine groove pattern cannot be formed stably, which is extremely problematic in the manufacture of a semiconductor device.

As a technique for precisely transferring the end of the rectangular mask pattern to achieve a substantially rectangular shape, a protrusion is provided in advance at the end of the pattern, or at the corner, whereby the end of the projection pattern is formed. A proposal to prevent rounding was found in Japanese Patent Publication No. 62-7
As described in Japanese Patent Publication No. 535, if the pattern is provided with a projection, the occurrence of the portion where the light intensity is reduced is rather promoted, and the problem associated with the distortion of the projection pattern cannot be solved. The technique described in this publication is to make the portions of the mask patterns adjacent to each other that have a weaker light intensity distribution appear more, and is difficult to employ as a technique for obtaining a stable resist shape. (While this prior art is concerned with precision on the order of 2μ to 5μ, the present invention is concerned with so-called submicron and even ultrafine pattern structures on the order of quarter micron). FIG. 5 (D) of the publication discloses an example in which a concave notch is provided in the concave pattern portion, but this is also for preventing the projection pattern of the corner portion from being circular. It does not have a function of correcting the distortion of the projected light intensity distribution.

[Object of the invention]

The present invention seeks to solve the above-mentioned problems,
The purpose is that, in a projection pattern formed by pattern portions of masks adjacent to each other and adjacent to each other, a portion where the light intensity is reduced occurs in the projection pattern between the portions of the adjacent pattern due to distortion of the light intensity distribution. It is an object of the present invention to provide a light exposure mask which can prevent the occurrence of the pattern and obtain a transfer pattern shape faithful to the mask pattern.

[Means for solving the problem]

To solve the above problems, the exposure mask of the present invention is a light exposure mask having a mask pattern,
In order to prevent a portion where the light intensity is reduced in the projected pattern between the adjacent patterns, at least a part of the opposing portions of the adjacent pattern portions adjacent to each other, The notch is formed by notching the pattern in the direction, and the notch is formed in a shape having a corner in an internal direction portion of the notched pattern.

Further, in the exposure method of the present invention, at least a part of the opposing portions of the adjacent pattern portions adjacent to each other has a portion where the light intensity is reduced in the projection pattern between the adjacent patterns. In order to prevent the pattern, a notch is formed by cutting the pattern in the inner direction of the pattern, and the notch has a pattern having a shape having a corner in the inner direction of the cut putter. Exposure is performed through a mask for use.

The configuration of the present invention will be described below with reference to FIG. 1 showing an embodiment of the present invention, which will be described in detail later.

That is, as shown in FIG. 1, the light exposure mask M according to the present invention includes at least one of opposing portions of adjacent patterns (pattern portions) 1 and 2 of the mask M which are adjacent to each other. In order to prevent a portion where the light intensity is reduced in the projected pattern between the adjacent patterns, a notch is formed by notching the pattern in the inner direction of the pattern, and the notch is The chipped pattern has a configuration having a corner in the inner direction part.

In the illustrated example, particularly, the cutout portions 31 and 32 are provided at corners inside (opposite sides) of both of the mask patterns 1 and 2. Notches 31, 32 in the illustrated example
Has a rectangular shape, and the upper left corner of the rectangular cutout 31 in the drawing, and the upper right corner of the cutout 32 correspond to the corners in the internal direction of the pattern.

[Action]

By providing the notches 31 and 32 as described above, a light intensity distribution faithful to the mask patterns 1 and 2 can be obtained as shown in FIG. That is, in the case of the prior art described with reference to FIG. 4, a portion A where the distribution of light intensity is small occurs in the projection pattern. According to the present invention, such a portion is generated. Can be prevented. Therefore, a projection pattern having a light intensity distribution faithful to the mask patterns 1 and 2 can be obtained. Therefore, according to the present invention, a transfer pattern faithful to the mask pattern, for example, a photoresist pattern can be obtained.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Needless to say, the present invention is not limited by the following examples.

In this embodiment, the present invention is applied to a light exposure mask for manufacturing a semiconductor device, and more specifically, is embodied as a light exposure mask used for forming a resist pattern in a photolithography process for manufacturing an VLSI. It is. In particular, in the present embodiment, the present invention is applied to a case where a resist pattern having an ultrafine structure is obtained, and a projection exposure apparatus (stepper) having a resolution of 0.8 μm is used. This is an example applied to a case where a pattern is to be formed, for example, a pattern of 0.6 to 0.7 μm is to be formed.

The exposure mask pattern of the present embodiment has a plurality of mask patterns, and is actually composed of a complicated combination of rectangular patterns corresponding to a desired resist pattern. The mutually adjacent mask patterns 1 and 2 are shown. In the present invention, a cutout portion is provided in at least a part of the opposing portions on both sides of the mask pattern, but in the present embodiment, both of the patterns 1 and 2 are opposed to each other. Notched portions 31 and 32 were provided at corners on the side (inside).

In this embodiment, the mask patterns 1 and 2 are formed on a transparent support 4 with chromium.

In FIG. 1, the distance between the two patterns 1 and 2, that is, the distance l in the figure is as fine as 0.7 μm or 0.6 μm. In the case of FIG. 3 which is a conventional example, when the width l of such a fine groove pattern (cut pattern) is close to the diffraction limit of the exposure apparatus, the light intensity distribution on the wafer as the projection surface is equalized. When expressed by contour lines connecting the intensity points, they are as shown in FIG. 4, and therefore, the grooves (the intervals between the patterns are called.
Near the end portion of the groove pattern (same in the present specification), that is, near a rectangular corner portion, pattern distortion occurs depending on the coherence of the optical system, and a part of the groove pattern (portion A)
There is a place where the high intensity is considerably reduced. In this part, the light energy density applied to the resist is smaller than in the other parts, the exposure becomes insufficient, and the resist remains after the development, and as shown in FIG. Bridging B as schematically shown
Therefore, stable formation of the groove-shaped resist pattern was difficult.

On the other hand, in the present embodiment, as shown in FIG. 1, cutout portions 31 and 32 are provided at the corners of the rectangular mask patterns 1 and 2. FIG. 2 shows the light intensity distribution when the mask patterns 1 and 2 provided with the notches 1 and 2 are transferred onto a wafer as a projection surface. FIG. 2 shows a light intensity distribution of a portion corresponding to a portion shown by a broken line in FIG. As is clear from FIG. 2, the pattern distortion at the corner portion is appropriately corrected, the light intensity is uniform over the entire groove pattern, and there is no portion where the light intensity is significantly reduced. Since the pattern shape of the resist after the resist exposure and development is formed in accordance with the contour distribution shape, no resist remains after the resist exposure and development, and a stable transfer pattern can be formed. As a result, a stable and highly reliable semiconductor device can be obtained by using this embodiment.

This is presumably because the presence of the cutouts 31 and 32 compensated for a portion where the light intensity distribution was weakened, thereby obtaining a light intensity distribution faithful to the mask pattern.

In this example, the notches 31 and 32 are defined as horizontal a and vertical b as shown in FIG.
, But is not limited to this shape. Further, notches may be further provided at corners of the upper patterns 31 and 32 facing each other in FIG. In addition to the corners, the notch may be arbitrarily formed as long as it is on both sides of the patterns 31 and 32 where the above-mentioned compensation action can be exhibited.

In this example, the dimensions a and b of the cutouts 31 and 32 can be designed by optimizing according to the optical characteristics of the exposure apparatus and the mask pattern.

For example, as parameters for determining the dimensions a and b, the distance l between the two mask patterns 31 and 32, the number of apertures NA of the exposure apparatus, the wavelength λ of light to be exposed, the coherence factor σ of the exposure apparatus (the optical coherence of the exposure apparatus) To indicate)
By assembling the functions f and g as follows and solving them,
A and b can be obtained by computer analysis.

f (l, NA, λ, σ) = g (a, b) By using the photo-exposure mask of this embodiment, a fine groove-shaped resist pattern can be formed stably in a photolithography process. In addition, it is possible to smoothly pass through a portion where light intensity distribution hardly passes through the ordinary method, that is, a portion where light hardly passes through, thereby obtaining a transfer pattern faithful to the mask pattern.

〔The invention's effect〕

As described above, according to the present invention, in the projection pattern formed by the mutually adjacent mask patterns, the light intensity is reduced due to the distortion of the light intensity distribution to the projection pattern between the mutually adjacent mask patterns. Can be prevented from occurring, and therefore transfer / transfer
There is an effect that a projection pattern shape can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of an essential part showing an embodiment of a light exposure mask of the present invention. FIG. 2 is a diagram partially showing a light intensity distribution when projected using this example. FIG. 3 is a plan view of a main part of a conventional example. FIG. 4 is a diagram partially showing a light intensity distribution when projected using the conventional example. Fifth
The figure is a schematic diagram showing the problems of the conventional example in that case. 1,2: Mask pattern, 31, 32: Notch.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-188857 (JP, A) JP-A-63-81351 (JP, A) JP-A-56-123434 (JP, A) 91523 (JP, A) JP-A-2-29747 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03F 1/08 H01L 21/30 502

Claims (3)

(57) [Claims] In a light exposure mask having a mask pattern, at least a part of an adjacent portion of an adjacent pattern portion adjacent to each other has a light intensity on a projection pattern between the adjacent patterns. In order to prevent the occurrence of a reduced portion, a notch is provided by cutting the pattern in the inner direction of the pattern, and the notch has a shape having a corner in the inner direction of the notched pattern. A light exposure mask, characterized in that: 2. The photo-exposure mask according to claim 1, wherein the notch is provided at a corner on both adjacent sides of the adjacent mask pattern. 3. An exposure method using a photo-exposure mask having a mask pattern, wherein at least a part of an adjacent portion of an adjacent pattern portion adjacent to each other has a pattern between the adjacent patterns. In order to prevent the occurrence of a portion where the light intensity is reduced in the projection pattern, a notch is formed by notching the pattern in the inner direction of the pattern, and the notch is formed with a corner in the inner direction of the notched pattern. An exposure method for performing exposure through a light exposure mask having a pattern having a configuration having a shape having the following.