JP2002198287A - Mask and its preparation method and exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mask that can fix a reference surface even if the periphery section of the mask (mask retention section) is retained on a mask stage by solving the problem of the reference surface of the mask not being fixed since the mask retention section corresponds to the non-guaranteed section of a wafer, when the mask that is prepared with a wafer as a substrate where the characteristics as the wafer are not guaranteed in the periphery region (non-guaranteed section) of approximately 10 mm from the outer-periphery edge of the wafer and the same time sag normally exists on a wafer surface is retained on a mask stage. SOLUTION: This mask is prepared with the wafer as the substrate. The wafer is set to the mask that should be a circular wafer that is cut from the center section of an original wafer that is larger than the mask.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a mask used in projection exposure using a charged particle beam, a method for manufacturing the mask, and an exposure method using the mask.

[0002]

2. Description of the Related Art In recent years, the development of semiconductor integrated circuit technology has been remarkable, and the tendency of miniaturization and high integration of semiconductor elements has been remarkable. As an exposure apparatus for printing an integrated circuit pattern on a sensitive substrate, a so-called optical stepper apparatus using light has been generally used.

However, as circuit patterns become finer, the resolution limit of light is concerned, and electron beams, ion beams,
2. Description of the Related Art Exposure apparatuses using X-rays have been actively studied and developed in recent years. A mask having a predetermined pattern is irradiated with an electron beam, an ion beam, or an X-ray, and a pattern in the irradiation range is reduced and transferred to a sensitive substrate by a projection optical system. An exposure apparatus has been proposed.

A mask having a predetermined pattern to be transferred to a sensitive substrate is manufactured using a wafer as a substrate. Among them, as a mask for a charged particle beam reduction transfer exposure apparatus, a part of a wafer is made into a membrane or a membrane is formed on the upper surface of the wafer, and the wafer is used as a mask as it is. Generally, the pattern is formed at the center of the mask. FIG. 5 shows charged particle beam exposure (for example, electron beam projection exposure).
FIG. 4 is a diagram showing the central portion (a portion where a pattern is formed) of the mask used in FIG. The pattern to be transferred is divided according to the size of the field of view of the projection optical system,
A pattern divided into a plurality of subfields 51 (for example, a square having a side of 1 mm) on the mask is formed.
A skirt portion 52 and a strut 53 are formed around each subfield 51. A support 53 formed in a lattice shape
Has a thickness of, for example, 170 μm, and maintains the strength of a mask made of a very thin (for example, 2 μm) membrane 54. At the time of exposure, a peripheral portion of the mask (mask holding portion) is held on a mask stage of the exposure apparatus.

[0005]

FIG. 6A is a cross-sectional view of a wafer, and FIG. 6B is a view showing a state where a mask manufactured using the wafer as a substrate is held on a mask stage. is there. As shown in FIG. 6A, in a peripheral region 61 (non-guaranteed portion) of about 10 mm from the outer peripheral edge of the wafer 60, the characteristics as a wafer are not guaranteed, and there is usually a droop on the wafer surface. is there. When the mask 62 manufactured using such a wafer as a substrate is held on the mask stage 63, the mask holding portion corresponds to the non-guaranteed portion of the wafer. Face 64
Or there was a problem that 65 was not constant.

The present invention has been made in view of such a problem, and provides a mask capable of keeping a reference surface constant even when a peripheral portion (mask holding portion) of the mask is held on a mask stage. The purpose is to:

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention firstly provides a "mask formed using a wafer as a substrate, wherein the wafer is located at a center of an original wafer larger than the size of the mask. A mask (claim 1), which is a circular wafer cut out, is provided. Since the mask is manufactured using the central portion without the non-guaranteed portion as the substrate without using the shape of the original wafer as it is, the reference plane can be made constant even when the peripheral portion of the mask is held.

The present invention also provides a mask according to claim 1, wherein the central portion is a portion including a center located at least 10 mm inward from an outer peripheral edge of the original wafer. Item 2) "is provided. Since the non-guaranteed portion is within a range of about 10 mm from the outer peripheral edge of the original wafer, a mask without the non-guaranteed portion is reliably manufactured.

The present invention also provides a third aspect of the present invention in which "the size of the original wafer is 300 mm or 400 mm in diameter, and the size of the circular wafer is 200 mm or 300 m in diameter.
m, wherein the mask according to claim 1 or 2 (claim 3) is provided. By setting the size of the circular wafer to a standard size, a conventional mask manufacturing apparatus, processing apparatus, or the like can be used as it is. If a circular wafer having a size different from the standard size is used, an apparatus corresponding to the size is newly required, which leads to an increase in cost. However, the present invention can suppress the increase in cost.

The present invention is a fourth method for manufacturing a mask using a wafer as a substrate, wherein the wafer is a circular wafer cut out from the center of an original wafer larger than the size of the mask. (Claim 4). Since the mask is manufactured using the central portion without the non-guaranteed portion as the substrate without using the shape of the original wafer as it is, the reference surface can be made constant even when the peripheral portion of the mask is held.

[0011] The present invention is also directed to a fifth aspect of the present invention, wherein a charged particle beam generated from a charged particle beam source is irradiated onto a mask having a predetermined pattern, and an image of the pattern is projected and formed on a sensitive substrate. 6. A charged particle beam exposure method according to claim 5, wherein said mask is a mask manufactured using a circular wafer cut from a central portion of an original wafer larger than the size of the mask as a substrate. )"I will provide a. Accordingly, even when the peripheral portion of the mask is held on the mask stage, the reference surface becomes constant, and a pattern having a desired shape can be formed in a desired region of the sensitive substrate.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a wafer serving as a substrate of a mask according to the present invention. The mask of this embodiment is shown in FIG.
As shown in FIG. 1, a peripheral portion 12 is cut off from a 300 mm original wafer 10 by a diamond cutter or a grinder using a laser, and the cut circular wafer 11 is cut.
(For example, a 200 mm wafer) is manufactured as a substrate.
Note that a method for manufacturing the mask will be described later.

FIG. 2 is a schematic view of a mask according to the present invention. In FIG. 2, reference numeral 21 denotes a pattern forming portion on which a fine pattern to be transferred to a sensitive substrate is formed;
Denotes a mask holding unit held on a mask stage of the exposure apparatus. The mask 20 of the present invention is manufactured using the circular wafer 11 having no non-guaranteed portion as a substrate. Therefore, there is no surface droop in the peripheral portion of the mask (mask holding portion 22),
Even when the mask holding unit 22 is held on the mask stage, the reference plane is constant.

Next, a method for manufacturing a mask according to the present invention will be described with reference to FIG. FIG. 3 is a view showing a process of manufacturing a mask using the cut-out circular wafer as a substrate. First,
An SOI (Silicon on Insulator) circular wafer including a supporting silicon substrate 31, a silicon oxide layer 32, and a silicon active layer 33, which is cut from the center of the original wafer shown in FIG. 1, is prepared. A silicon nitride film 34 is formed on the back surface of the support silicon substrate 31 of this SOI circular wafer (FIG. 3).
(A)). Then, the silicon nitride film 34 in the region where the membrane is to be formed is removed by dry etching. Next, using the silicon nitride film 34 as a protective film, the supporting silicon substrate 31 in a region where the silicon nitride film 34 is removed is etched until the silicon oxide layer 32 is exposed (FIG. 3).
(B)).

Thereafter, a resist is coated on the silicon active layer 33, and a fine pattern to be transferred to the sensitive substrate is transferred by using an exposure apparatus such as an electron beam lithography apparatus to form a resist pattern 35 (FIG. 3 ( C)). The silicon active layer 33 is etched using the resist pattern 35 on which the fine pattern to be transferred to the sensitive substrate is transferred (FIG. 3D) as an etching mask, and the silicon oxide layer 32 is removed to complete the mask (FIG. 3D). (E)).

According to the above-described mask manufacturing method, the unevenness of the mask holding portion is 10% of the thickness of the silicon active layer (for example, 2 μm).
Since it is controlled as follows, the reference plane of the mask is
A mask that can be kept constant within the range of m or less was produced. Next, the charged particle beam exposure method of the present invention will be described with reference to FIG.

FIG. 4 is a schematic view of an electron beam exposure apparatus which is a kind of a charged particle beam exposure apparatus for realizing the charged particle beam exposure method of the present invention. The electron gun 121 arranged at the uppermost stream of the optical system emits an electron beam downward. Electron gun 12
Below 1, a condenser lens system 122 is provided.

An illumination beam shaping aperture 123 is provided below the condenser lens system 122. The image of the beam forming aperture 123 is formed on the mask 126 by the illumination lens 125. Therefore, the beam forming aperture 123
Can pass only an illumination beam that illuminates one subfield (unit exposure pattern area) of the mask 126.

Below the beam forming opening 123, a blanking deflector, a blanking opening (both not shown), an illumination beam deflector 124 and the like are arranged. Mask 12
When there is no need to irradiate the illumination beam to 6, the blanking deflector deflects the illumination beam to hit the non-opening of the blanking aperture so that the illumination beam does not hit the mask 126. The illumination beam deflector 124 mainly scans the illumination beam sequentially in the X direction in FIG. 4 to illuminate each subfield of the mask 126 within the field of view of the illumination optical system.

Below the beam forming opening 123,
An illumination lens 125 is provided. This lens 125
Converts the electron beam into a parallel beam and impinges it on the mask 126 to form an image of the beam forming aperture 123 on the mask 126. The mask 126 is the mask according to the present invention shown in FIG.
It extends in the plane perpendicular to the optical axis (the XY plane), and has a number of subfields shown in FIG. 5 as described above. On the mask 126, a pattern (chip pattern) forming one semiconductor device chip as a whole is formed.

The peripheral portion of the mask 126 is held on a mask stage 127 movable in the X and Y directions. To illuminate each subfield beyond the field of view of the illumination optics, the mask 126 is moved mechanically. Since each subfield is illuminated within the field of view of the illumination optical system, the electron beam can be deflected by the deflector 124 as described above.

A projection lens 128 is provided below the mask 126.
133, a deflector 129 and the like. Then, an illumination beam is applied to a certain subfield of the mask 126, and the electron beam passing through the pattern portion of the mask 126 is reduced by the projection lenses 128 and 133, and deflected by each lens and the deflector 129, and is deflected by the sensitive substrate. An image is formed at a predetermined position on the 17 processing surface 17A (upper surface). An appropriate resist (not shown) is applied on the surface 17A. The resist is given a dose of an electron beam, and the pattern on the mask 126 is reduced and transferred onto the sensitive substrate 17.

By the above charged particle beam exposure method, the reference surface of the mask could be held constant on the mask stage, and the desired pattern could be transferred onto the sensitive substrate.

[0024]

As described above, according to the present invention,
Since the mask is manufactured using the central part without the non-guaranteed part as the substrate without using the shape of the original wafer as it is, the reference plane is fixed even when the peripheral part of the mask (mask holding part) is held on the mask stage Can be as a result,
The design of the mask holding function on the mask stage is facilitated, and the need for a high-precision exposure optical system focusing mechanism is eliminated.

[Brief description of the drawings]

FIG. 1 is a schematic view of an original wafer serving as a substrate of a mask according to the present invention.

FIG. 2 is a schematic view of a mask according to the present invention.

FIG. 3 is a schematic diagram illustrating a mask manufacturing method according to the present invention.

FIG. 4 is a schematic diagram illustrating a charged particle beam exposure method according to the present invention.

FIG. 5 is a detailed view of a pattern forming portion of a mask.

FIG. 6A is a sectional view of an original wafer, and FIG.
(B) is a view showing a state in which a conventional mask manufactured using an original wafer as a substrate is held on a mask stage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Original wafer 11 ... Circular wafer 12 ... Peripheral part 17 ... Sensitive substrate 17A ... Processing surface 20 ... Mask 21 ... Pattern forming part 22 ... Mask holding part 31 ... Supporting silicon substrate 32 ... Silicon oxide layer 33 ... Silicon active layer 34 ... Silicon nitride film 35 ... Resist 121 ... Electron gun 122 ... Condenser lens system 123 ... Beam Molding aperture 124 ... Illumination beam deflector 125 ... Illumination lens 126 ... Mask 127 ... Mask stage 128, 133 ... Projection lens 129 ... Deflector 51 ... Subfield 52 ...・ Skirt part 53 ・ ・ ・ Support column 54 ・ ・ ・ Membrane 60 ・ ・ ・ Wafer 61 ・ ・ ・ Peripheral area (non-guaranteed part) 62 ・ ・ ・ Mask 63 ・ ・ ・ Mask stay 64, 65 ... mask reference surface

Claims (5)

[Claims] 1. A mask manufactured using a wafer as a substrate, wherein the wafer is a circular wafer cut out from the center of an original wafer larger than the size of the mask. 2. The mask according to claim 1, wherein the central portion is a portion including a center located at least 10 mm inward from an outer peripheral edge of the original wafer. 3. The size of the original wafer is 300 mm in diameter.
3. The mask according to claim 2, wherein the diameter of the circular wafer is 400 mm, and the size of the circular wafer is 200 mm or 300 mm. 4. 4. A method for manufacturing a mask using a wafer as a substrate, wherein the wafer is a circular wafer cut out from the center of an original wafer that is larger than the size of the mask. 5. A charged particle beam exposure method, which irradiates a charged particle beam generated from a charged particle beam source onto a mask having a predetermined pattern, and projects and forms an image of the pattern on a sensitive substrate. A charged particle beam exposure method, wherein the mask is a mask manufactured using a circular wafer cut from the center of an original wafer larger than the size of the mask as a substrate.