JPH11329931A - Reticle for electron beam projection exposure, electron beam exposure system, and cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To readity detect contamination for deciding whether cleaning of the carbon contamination of a reticle is required or the cleaning is adequate. SOLUTION: A plurality of metal thin films 101 and 102, formed so that each of them does not touch one another in a surface for measuring electrical resistances among them, are formed on the surface of a reticle in the reticle that is used for electron beam projection exposure for projecting a pattern which is formed on the reticle onto a sensitive substrate by electron beams. In this manner, by the use of the reticle with the metal films 101 and 102 formed such that the surface is divided into several portions, the extant of carbon contamination can be readity measured by measuring the resistance between films at each section, thus the carbon contamination is appropriately and rapidly dealt with.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reticle used for electron beam projection exposure, an electron beam exposure apparatus, and a reticle cleaning method.

[0002]

2. Description of the Related Art At present, a method (stepper) using light reduction projection exposure is used for processing a fine shape of a semiconductor integrated circuit. In this method, the pattern formed on the photomask is reduced and projected on the silicon wafer coated on the resist using light (ultraviolet light). However, since dirt on the mask directly affects the projected image, the mask is not affected. Cleaning and dirty hats are very important. For this reason, the exposure environment is cleaned, and a thin film called a pellicle, which is transparent to light used for reduction projection, is placed at a certain distance from the mask, thereby protecting the mask from various types of contamination.
This prevents a reduction in the processing capacity of the device.

The minimum processing line width of a semiconductor circuit has been reduced year by year due to the high integration of semiconductors. However, in projection exposure using light (ultraviolet light), the minimum processing line width is limited in principle by the diffraction limit. Therefore, a method using an X-ray or an electron beam for performing finer processing has been proposed. In electron beam projection exposure, which is one of them, a pattern formed on a thin film called a reticle (sometimes called a mask) is thinned by an electron beam optical system to a substance which reacts to an electron beam called a resist. Projection is performed on the applied silicon wafer. Because the electron beam is strongly absorbed by the material, it is difficult to form a transparent film for the electron beam, and thus it is difficult to protect the reticle with a pellicle, and how to deal with reticle contamination Is very important.

[0004]

When the reticle is continuously irradiated with an electron beam, carbon stains adhere to the surface of the reticle. In general, a very small amount of organic matter is present in a vacuum vessel due to the backflow of oil from the vacuum evacuation system, etc. When an electron beam is irradiated in that atmosphere, the organic matter is decomposed and carbon adheres to the surface. You do it. Such carbon contamination is not a problem if it is in a very small amount. However, when the carbon contamination becomes a certain level or more, the absorption of an electron beam increases, which causes a distortion in the shape of the reticle due to thermal distortion. Therefore, it is necessary to clean the carbon dirt on the reticle to which carbon dirt has adhered to some extent. Therefore, there has been a demand for a means for easily detecting the carbon contamination of the reticle in order to determine whether or not the cleaning is necessary, and to determine whether or not the cleaning is sufficient.

[0005] The present invention has been made in view of the above problems.

[0006]

Therefore, the present invention provides the first
In a reticle used for electron beam projection exposure in which a pattern formed on a reticle is projected on a sensitive substrate by an electron beam, each of the reticle surfaces is in contact with an in-plane surface so that the electrical resistance between them can be measured. A reticle for electron beam projection exposure, wherein a plurality of metal thin films formed so as not to be formed are formed.

According to a second aspect of the present invention, there is provided an electron beam projection exposure apparatus for projecting a pattern formed on a reticle onto a sensitive substrate using an electron beam, wherein the reticle is formed on the reticle. An electron beam exposure apparatus provided with means for measuring the electrical resistance between the plurality of thin metal films. Further, the present invention is a third aspect of the present invention wherein "a device for cleaning carbon contamination generated on the reticle is provided, and a means for measuring electric resistance between respective portions of the metal thin film formed on the reticle in the cleaning device is provided. 3. An electron beam exposure apparatus according to claim 2, wherein (3) is provided.

The present invention also provides a method for cleaning carbon stains on a reticle, which comprises measuring the electrical resistance between a plurality of metal thin films provided for measuring the degree of carbon stains on the reticle. An exposure method, wherein the carbon contamination of the reticle is cleaned in accordance with the value of the electrical resistance.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a reticle for electron beam projection exposure according to the present invention, a plurality of electrodes are formed by forming a metal film on a reticle surface, and the reticle is attached to the reticle surface by measuring an electric resistance value between the electrodes. It measures the degree of carbon contamination. An outline of the present invention will be described with reference to FIG.

The metal film 10 is formed on the surface of the silicon wafer 100.
Consider a case in which 1, 102 are formed close to each other. When the electric resistance between the two metal films is measured, the resistance when a current flows through the underlying silicon is measured. On the other hand, when the carbon stain 110 is deposited on the surface of the portion where the metal thin film is formed adjacent to the surface, current flows through the carbon layer, so that when the resistance is measured between the two metals, the carbon layer is deposited. The resistance is smaller than when not. Further, the resistance value changes depending on the thickness of the carbon layer. Therefore, by measuring the resistance between the electrodes, it is possible to know the presence or absence of the volume of carbon and how much the carbon layer is deposited.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0012]

FIG. 2 is a structural view of a reticle for electron beam projection exposure according to an embodiment of the present invention. There is a reticle 201 in which a silicon wafer is partially processed into a thin film and a pattern is formed on the thin film. A very thin (thickness of 100 nm or less) gold film is formed on the surface of the reticle, and the gold thin film is divided into four portions on the reticle surface. A pad 202 is formed on each portion of the thin film so as to be easily electrically connected from the outside by an electrode or the like, so that the resistance between the thin films can be easily measured.

FIG. 3 is a block diagram showing an embodiment of an electron beam projection exposure apparatus according to the present invention. Vacuum container (chamber) 34
In 0, an electron source 310, an illumination electron optical system 311, a reticle stage 315, a projection electron optical system 312, a wafer stage 313, and a reticle transport device 320 are arranged, and the reticle 300 is arranged on the reticle stage 315. A wafer 314 is arranged on the wafer stage 313. The cleaning device 3 is provided in the vacuum container 340.
32 and a reticle loader 331 are connected, and the reticle can move in three rooms via the reticle transport device 320. In this embodiment, a reticle having the structure shown in FIG. 2 is used as the reticle. The reticle stage 315 has a device 32 for measuring the resistance between the thin films.
1 is provided, and during the exposure, the extent to which carbon adheres is periodically measured by electric resistance. If it is determined that the resistance value has fallen below a certain value and the amount of deposited carbon has reached an amount that may interfere with projection exposure, the exposure is interrupted and the reticle 3
00 is sent to the reticle cleaning device 332 by the reticle transport device 320. On reticle stage 315, reticle 300 prepared for reticle loader 331 is provided.
Another reticle 301 having the same pattern as that described above is arranged, and exposure is quickly resumed. On the other hand, the reticle 300 conveyed to the reticle cleaning device 332 is irradiated with ultraviolet rays in a reduced-pressure oxygen atmosphere, so that the electric resistance between the thin films can be measured even in this cleaning device. If it is determined from the measurement result of the resistance value of the above that the removal of attached carbon is insufficient, further cleaning is performed. After such cleaning is repeated and it is determined that the deposited carbon has been sufficiently removed, the reticle 300
Is transported to the reticle loader 331. If it is determined that the amount of carbon stains adhered to the reticle 301 as a result of the exposure has reached an amount that may interfere with the projection exposure, the reticle 301 is conveyed to the reticle cleaning device 332, and 300 is placed on the reticle stage.

If a reticle having a gold film formed so as to divide the surface into several parts is used, the degree of carbon contamination can be easily measured by measuring the resistance between the films in each part. Therefore, it is possible to appropriately and promptly respond to carbon contamination. In the present embodiment, the gold film is formed by dividing the reticle surface into four portions, but the number of divisions of the shape area surface on which the gold film is formed is not limited to this. In this embodiment, gold is used as the material of the film. However, the material is not limited to gold, and another metal or a conductive material may be used.

In this embodiment, a reticle cleaning apparatus for removing carbon stains by irradiating ultraviolet rays in a reduced-pressure oxygen atmosphere is used. However, the apparatus is effective for removing carbon stains and damages the reticle. Or any other cleaning device that is less likely to cause contamination. The reticle cleaning device 332 is provided separately, but may be performed in the vacuum container 340 if carbon dirt can be removed in the vacuum container 340.

The reticle 300 may be arranged directly on the reticle stage, but may be arranged after being fixed to a reticle holder or the like. When using a reticle holder, electrodes are provided on the reticle holder, and a vacuum container 340 is provided.
Before transporting the reticle into the reticle, the reticle is fixed to a reticle holder, and the electrodes of the reticle holder are electrically connected in advance to the pads 202 of each metal thin film shown in FIG. In this way, the electrodes of the resistance measuring device 321 do not need to be directly connected to the small area of the pad 202 (they only need to be electrically connected to the electrodes of the reticle holder), so that the reticle can be easily aligned with the resistance measuring device 321. In addition, the transfer time can be shortened.

In the above embodiment, the degree of carbon contamination was observed by providing a gold film on the reticle. For example, a metal film as shown in FIG. 1 was formed on a reticle holder for fixing the reticle. In addition, instead of directly detecting the degree of contamination of the reticle, it is also possible to indirectly detect the degree of contamination of the reticle by detecting the degree of contamination of the reticle holder. Since the reticle holder can be shared or the same shape for various reticles,
Since it is not necessary to form a metal layer for each reticle, the cost and time required for manufacturing the reticle can be reduced.

[0018]

As described above, according to the reticle for electron beam projection exposure of the present invention and the electron beam projection exposure apparatus using the same, carbon stains deposited on the reticle can be easily detected and evaluated. By making the removal appropriate and quick, a high throughput as an electron beam projection exposure apparatus can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a reticle for electron beam projection exposure according to the present invention.

FIG. 2 is a schematic configuration diagram of a reticle for electron beam projection exposure according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an electron beam projection exposure apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 100 ... Wafer 101, 102 ... Metal film 110 ... Carbon contamination (contamination) 120 ... Electric resistance meter 201 ... Reticle 202 ... Electrode connection part (pad) 300,301,302 Reticle 310 electron source 311 illumination electron optical system 312 projection electron optical system 313 wafer stage 314 wafer 315 reticle stage 320 reticle transport device 321, resistance measuring device 331, reticle loader 332, reticle cleaning device 340, vacuum container

Claims (4)

[Claims] 1. A reticle used for electron beam projection exposure for projecting a pattern formed on a reticle onto a sensitive substrate by an electron beam, wherein each of the reticle surfaces has a surface so that an electric resistance between the reticle can be measured. A reticle for electron beam projection exposure, wherein a plurality of metal thin films formed so as not to contact each other are formed. 2. An electron beam projection exposure apparatus for projecting a pattern formed on a reticle onto a sensitive substrate by an electron beam, wherein a plurality of thin metal films formed on the reticle are used by using the reticle according to claim 1. An electron beam exposure apparatus comprising means for measuring the electric resistance of the electron beam. 3. The apparatus according to claim 1, further comprising a device for cleaning carbon stains generated on said reticle, and means for measuring electric resistance between respective portions of the metal thin film formed on the reticle in said cleaning device. Item 3. An electron beam exposure apparatus according to Item 2. 4. A method for cleaning carbon contamination generated on a reticle, comprising: measuring an electric resistance between a plurality of metal thin films provided for measuring a degree of carbon contamination of the reticle; An exposure method, wherein the carbon stain on the reticle is cleaned according to the value.