JPH0667405A - Mask for exposure - Google Patents

Abstract

PURPOSE:To provide a mask for exposure which easily solves the problem of a shift of the pattern due to warpage caused in the case where a light shielding film is formed on the surface of the substrate. CONSTITUTION:In a mask 1 for exposure with a light shielding film 2 on the periphery of the surface of the substrate 10, the light shielding film 2 is divided with slits 3, etc. When this mask for exposure is formed as a negative pattern mask, the precision of superposition on a positive pattern mask is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask. The exposure mask of the present invention can be used, for example, for forming a pattern of an electronic material (semiconductor device or the like).

[0002]

2. Description of the Related Art Conventionally, a patterned light-shielding portion is formed of a light-shielding material on a substrate which is transparent to exposure light, and the material to be exposed is exposed and the pattern is transferred, Various patterns are formed on a material to be exposed. For example, in the case of forming various fine patterns on a semiconductor device, pattern exposure of a photoresist with an exposure mask is performed. One-to-one exposure may be performed, and reduction projection exposure such as 5-to-1 may be performed when forming a fine pattern.

FIG. 2 shows a conventional manufacturing process of this type of exposure mask. For example, a transparent substrate 10 having a thickness of about 2.3 mm, for example, a quartz substrate 10 as shown in FIG. 2A is used, and a light shielding material film 20 is provided on one surface thereof as shown in FIG. 2B.
To form. For example, Cr is formed to have a thickness of 700 to 800 Å. At this time, the quartz substrate 1 warps due to the contraction due to the metal film (here, the Cr film), as shown extremely in FIG. In this state, the light shielding material film 20 is patterned by EB drawing or the like. After forming the pattern, the warp is released, and the state shown in FIG. Therefore, as the warp returns, the formed pattern 21 is displaced. Even if the pattern is accurately formed in the state of FIG. 2B, the pattern formed at the distance A in FIG.
This is because in this state, the pattern shifts by W1 and W2 in FIG. The pattern shift amounts W1 and W2 are referred to as a gain.

In order to prevent the displacement of the pattern due to the occurrence of warp as described above, for example, the light shielding material film 20 is not made of Cr alone, but is formed by forming chromium oxide Crx Oy in a thickness of 100 to 300 Å on the Cr film. It is also used. As a result, it is possible to reduce the warp, reduce the reflectance, and improve the pattern accuracy. However, even with this method, although it is possible to reduce the warp to some extent, it is difficult to suppress the warp to below the required accuracy.

Therefore, as shown in FIG. 3, Cr and / or
Alternatively, it is conceivable to cover the entire surface of the substrate 10 with the light shielding material film 20 made of chromium oxide or the like and perform patterning. According to this method, since both surfaces of the substrate 1 are balanced, the occurrence of warpage can be reduced. Moreover, against charge-up by electron beam (EB), etc., it is possible to ground from the side or bottom of the substrate, making it easy to take measures against static electricity.
In addition, it is possible to play a role of a back surface protective film of the substrate 10, which is advantageous.

However, in this case, the pattern area of the substrate is not necessarily the entire surface of the substrate, but rather the pattern area 4 is often a part of the substrate as shown in FIG.
A light-shielding film is left around the substrate. The reason is that, if Cr or the like in the entire unnecessary portion is removed by EB or the like, it takes too much time and the productivity is extremely reduced. (Especially with negative pattern masks this problem occurs). Another reason is that it is advantageous to leave a light-shielding material film such as Cr at least in the periphery in order to facilitate the above-mentioned countermeasure against static electricity. However, if the light-shielding material film is left on the outer periphery of the substrate in this way, the warp is unlikely to return, which eventually causes a problem that the image is blurred in the projection exposure process.

Conventionally, as a countermeasure against the pattern positional deviation due to the occurrence of such a warp, pattern correction is applied according to the pattern positional deviation. However, in this method, the correction amount differs depending on the position, and the behavior requiring correction also differs depending on the pattern shape, and the correction program becomes extremely complicated. At present, in particular, in accordance with the warp of the negative mask, the positive mask is also formed by correcting the pattern for that amount, so that the superposition in the case of using both the positive mask and the negative mask is accurate. ing. However, this requires an extremely complicated program, is complicated, and differs depending on the pattern shape, and cannot be said to be a technique that can be easily used.

It is possible to thicken the substrate such as quartz to reduce the warpage mechanically, but the material cost becomes high, and the drawing device and the processing equipment need to be remodeled with high accuracy.
Also, it is necessary to improve the stepper (exposure machine) itself,
It is not practical because it causes compatibility problems with existing equipment and requires new investment.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exposure mask which solves the above-mentioned problems of the prior art and easily solves the problem of pattern displacement due to warpage that occurs when a light-shielding film is formed on a substrate surface. To aim.

[0010]

According to the invention of claim 1 of the present application, in an exposure mask having a light-shielding film on the peripheral portion of the substrate surface, the light-shielding film on the peripheral portion is divided. A mask for use, which achieves the above object.

The invention according to claim 2 of the present application is the exposure mask according to claim 1, wherein the exposure mask is a negative pattern mask and is configured to enhance overlay accuracy with a positive pattern mask. Therefore, this achieves the above object.

[0012]

The exemplification of FIG. 1 is a specific example of the exposure mask according to the invention of claim 1. In this example, in the exposure mask having the light shielding film 2 on the peripheral portion of the substrate surface, the peripheral portion is shielded from light. In this example, the film 2 is divided by forming slits 3, whereby the stress due to the light-shielding film 2 in the peripheral portion of the substrate is dispersed, the pattern displacement due to warpage is reduced, and an accurate exposure mask is obtained. To be

Further, by constructing the exposure mask of the first aspect as a negative pattern mask, it is possible to reduce the pattern deviation and improve the overlay accuracy with the positive pattern mask.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. However, as a matter of course, the present invention is not limited to the examples described below.

Example 1 In this example, an exposure mask 1 as shown in FIGS. 1A and 1B was obtained. In FIG. 1, reference numeral 10 is a substrate made of quartz, and a light-shielding film 2 exists around the substrate 1 and is divided by a slit 3. 4 is a pattern area.

In this embodiment, a quartz substrate (thickness: 2.
3mm or slightly thinner than the front and back surfaces and side surfaces, that is, the entire surface is formed with Cr (700Å to 900Å) or Cr and Crx Oy (100Å to 300Å), that is, as shown in FIG. By forming a blank having the same structure and thus the front and back surfaces having the same structure, the mechanical stress was balanced and the flatness was extremely increased. By passing through a normal process, the back surface film is removed and a pattern is formed only on the front surface. At this time, in order to prevent the warp due to the stress due to the surface pattern film, at least the film on the quartz substrate 1 is formed so that the light-shielding film 2 (light-shielding frame) formed in the peripheral portion of the quartz substrate 1 is discontinuous. Slit 3 in
One or more of them are provided in a slit structure to alleviate the generated stress, thereby providing an extremely high precision mask (reticle).

Generally, the pattern accuracy of a reticle that requires 0.35 μm or less in the device rule is 1:
Although ± 0.03 μm or less is required on the 5-reticle pattern, this can be satisfied according to the present embodiment.

The relationship between the substrate flatness and the pattern position accuracy outlined by FIG. 2 is shown in more detail in FIG. This is the case of single-sided Cr, the warp is now 1 μm, and 10
Calculating the pattern error on a 0 mm long strip gives 0.04
It becomes 6 μm. From the formula shown in FIG. W1 = 2.286 × 0.001 / 100 = 0.023μ
This is because m Gain = W1 + W2 = 0.046 μm / 100 mm. (For the flatness change when heating a substrate in which one or two layers of chrome film are formed on a quartz substrate and provided with a light shielding portion, see Hirokazu Kawahira in STEP / MICROPATTERNING '89 on November 20, 1989. Announcement of "ARRAY METROLOG
(See the material of "Y REQUIREMENTS").

On the other hand, as shown in FIG. 5, in the case of one-sided Cr coating, the change in flatness is deviated from the theoretical value II, while the experimental value I is deviated as shown due to the deflection of the substrate itself. As a result of double-sided coating, the behavior was close to the theoretical value II. That is, in the case of normally single-sided Cr, the amount of warpage in the blank state is 1.5 to 2.5 μm (including its own weight) or more. Now, assuming that the average is 2.0 μm, the Cr is surrounded by a frame. If it does not exist, it returns to a substantially flat state after etching, so 2.0 μm, 1.5 μm even when the self weight is added, and the total gain at this time is about 0.08 μm (± 0.035 For the following specifications). Also, if there is a frame, it may not return to its original state, but may cause a focus problem in the stepper process. On the other hand, when the substrate 10 is coated on both sides with Cr or the like as in the present embodiment, the substrate is substantially optically flat (optically flat), and the peripheral edge of the substrate does not have Cr even after etching. If you make a frame pattern with slits as in the example, keep this flat state,
The pattern shift amount depends only on the substrate weight, and satisfies ± <0.035 as the total gain.

As described above, the exposure mask of this embodiment is
The light-shielding film 2 forming a frame-shaped pattern around the substrate 10 is divided by the slits 3, so that stress distribution can be achieved.
Pattern shift is prevented. Therefore, even when this mask is, for example, a negative pattern mask in which a light shielding film normally remains on the outer periphery, the problem can be solved when Cr remains.

As a result, it is not necessary to correct the electron beam drawing pattern in order to correct the pattern shift. No correction by a complicated program is necessary. In addition, the process of making a mask (reticle) may be the same as it is now.
No need for remodeling or capital investment. In addition, it is the cheapest compared to other conventional technologies and can suppress the price increase. Further, in the present embodiment, since a conductive film such as Cr which is a light-shielding material is formed on the side surface and the back surface in particular, a pattern is formed. Since it has chromium oxide), it also has the advantage of serving as a protective film on the back surface.

Example 2 In this example, the mask formed as in Example 1 was used as a negative pattern mask to improve the overlay accuracy with a positive pattern mask. In general, since a powdery light-shielding film does not remain on the outer periphery of a positive pattern mask, there is no problem of pattern displacement. Therefore, according to the configuration of this example, the light-shielding film in the peripheral portion is almost divided even for the negative pattern mask. As a result of using the pattern-free pattern, it was possible to realize a precise and reproducible pattern formation with very good overlay accuracy.

[0023]

The exposure mask of the present invention can easily solve the problem of pattern shift due to warpage that occurs when a light-shielding film is formed on the surface of a substrate, and can realize good high-precision pattern formation. .

[Brief description of drawings]

1A and 1B are diagrams showing a configuration of an exposure mask of Example 1, where FIG. 1A is a partial plan view and FIG. 1B is a view in the direction B in FIG.

FIG. 2 is a diagram showing a problem.

FIG. 3 is a diagram showing a problem.

FIG. 4 is a diagram showing substrate flatness and pattern position accuracy.

FIG. 5 is a diagram showing accuracy changes due to flatness changes.

[Explanation of symbols]

 1 exposure mask 2 light-shielding film around the substrate surface 3 slits (for dividing the light-shielding film 2) 4 pattern area 10 substrate

Claims (2)

[Claims] 1. An exposure mask having a light-shielding film on a peripheral portion of a substrate surface, wherein the light-shielding film on the peripheral portion is divided. 2. The exposure mask according to claim 1, wherein
An exposure mask configured as a negative pattern mask to enhance the overlay accuracy with a positive pattern mask.