JP2005108867A - Exposure mask and electron beam exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the thin film part of an exposure mask being used in an exposure system from being damaged by adhering to a wafer. <P>SOLUTION: The exposure mask 30 is provided with a mechanical stopper 35 for preventing contact of a thin film part 32 and a wafer 40 on the surface of the thin film part 32 opposing the wafer and having an opening 33 corresponding to an exposure pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure mask used in an exposure apparatus that exposes a fine pattern used in a manufacturing process such as a semiconductor integrated circuit, and in particular, a mask having an opening corresponding to the exposure pattern is close to the surface of a sample such as a semiconductor wafer. The present invention relates to an exposure mask used in an electron beam proximity exposure apparatus in which an exposure is performed with an electron beam that has been disposed and irradiated with an electron beam through an opening.

  In recent years, with the need for higher integration of semiconductor integrated circuits, further miniaturization of circuit patterns has been demanded. At present, the limits of miniaturization are mainly limited to exposure apparatuses, and new exposure apparatuses such as an electron beam direct writing apparatus and an X-ray exposure apparatus have been developed.

  Recently, an electron beam proximity exposure apparatus that can be used for ultrafine processing at a mass production level has been disclosed as a new type of exposure apparatus (for example, Patent Document 1 and Patent Document 2 corresponding to Japanese Patent Application). .

  FIG. 1 is a diagram showing a basic configuration of an electron beam proximity exposure apparatus disclosed in Patent Document 1. As shown in FIG. A conventional electron beam proximity exposure apparatus will be briefly described with reference to FIG. As shown in the drawing, an electron gun 12 having an electron beam source 14 for generating an electron beam 15, a shaping aperture 16, and an irradiation lens 18 for making the electron beam 15 a parallel beam, A scanning unit 21 that includes a pair of main deflectors 22 and 24 and a pair of sub-deflectors 51 and 52 and that scans the electron beam parallel to the optical axis, and a mask 30 having an opening corresponding to the pattern to be exposed. And an electrostatic chuck 44 and an XY stage 46.

  As shown in FIG. 2, the exposure mask 30 has a thin film portion 32 having an opening formed in the center of the thick outer edge portion 34, and the thin film portion 32 has an opening 33 corresponding to the pattern to be exposed. Is provided. And it arrange | positions so that it may adjoin to the wafer 40 attracted | sucked by the electrostatic chuck 44 (so that the gap of the mask 30 for exposure and the wafer 40 may be set to 50 micrometers, for example), and an electron beam is perpendicular | vertical to the mask 30 By irradiating, the resist layer 42 on the surface of the sample 40 is irradiated with the electron beam that has passed through the opening 33 of the mask.

  The main deflectors 22 and 24 in the scanning means 21 control the deflection of the electron beam so that the electron beam 15 scans the entire surface of the thin film portion 32 of the exposure mask 30 as shown in FIG. As a result, the mask pattern of the mask 30 is transferred to the resist layer 42 on the wafer 40 at the same magnification.

Further, the sub deflectors 51 and 52 in the scanning unit 21 control (inclination correction) the incident angle of the electron beam to the mask pattern so as to correct the mask distortion. As shown in FIG. 4, when the incident angle of the electron beam 15 to the exposure mask 30 is α and the gap between the exposure mask 30 and the wafer 40 is G, the transfer position of the mask pattern by the incident angle α is as follows. The deviation amount δ is expressed by the following equation:
δ = G ・ tanα
It is represented by

  In FIG. 4, the mask pattern is transferred to a position shifted from the normal position by a shift amount δ. Therefore, when the exposure mask 30 has a mask distortion as shown in FIG. 5A, for example, the tilt control of the electron beam is performed according to the mask distortion at the electron beam scanning position, thereby FIG. As shown in B), the mask pattern without mask distortion is transferred.

  The XY stage 46 moves the wafer 40 adsorbed by the electrostatic chuck 44 in two horizontal orthogonal axes, and moves the wafer 40 by a predetermined amount each time the mask pattern is transferred at an equal magnification. A plurality of mask patterns can be transferred to a single wafer 40.

U.S. Pat.No. 5,831,272 Japanese Patent No. 2951947

In order to reduce the circuit pattern, it is necessary to narrow the line width of the opening 33 of the mask 30. The mask thin film portion 32 is required to be formed very thin in order to accurately shape a miniaturized pattern by passing the electron beam 15 through the opening 33 having a narrow line width.
Further, in order to increase the throughput of the exposure apparatus, it is necessary to expose as large a pattern as possible (for example, for one die) with the same mask, so that the mask thin film portion 32 is required to be formed with a large area.
Therefore, the mask thin film portion 32 is required to be thin and large, and a slight deflection due to its own weight occurs.

  In the proximity exposure type electron beam exposure apparatus as described above, the mask 30 and the wafer 40 are arranged very close to each other, and the wafer 40 is irradiated between the mask 30 and the wafer 40 by irradiation of the electron beam 15. Various attractive forces such as Coulomb force due to the electric charge accumulated in the substrate and intermolecular force between the mask 30 and the wafer 40 are acting. Therefore, if the suction force acts strongly by approaching the wafer 40 due to the deflection of the mask thin film portion 32 described above, the mask thin film portion 32 adheres to the wafer 40, and in the worst case, the mask. The thin film portion 32 may be damaged.

  In view of the above problems, an object of the present invention is to prevent the thin film portion of an exposure mask used in an exposure apparatus from being bonded to the wafer and to prevent the mask thin film portion from being damaged.

In order to achieve the above object, the exposure mask of the present invention includes a mechanical stopper on the surface of the mask thin film portion facing the wafer.
In other words, the exposure mask of the present invention is provided on the opposing surface of the thin film portion having an opening corresponding to the pattern exposed to the wafer and the wafer of the thin film portion, and the opposing surface of the thin film portion approaches the wafer within a predetermined distance. And a mechanical stopper that contacts the wafer and prevents contact between the thin film portion and the wafer.

  The mechanical stopper provided on the thin film portion can be realized by providing a protrusion on the surface of the mask thin film portion facing the wafer.

  In addition, if such a mechanical stopper (projection) is formed of a conductive material, it is possible to determine whether the mechanical stopper is in contact with the wafer by detecting conduction between the exposure mask and the wafer. Become.

  For this purpose, the electron beam exposure apparatus of the present invention includes a continuity detector that detects the continuity between the exposure mask and the wafer.

  As described above, since the exposure mask of the present invention includes the mechanical stopper on the surface of the mask thin film portion that faces the wafer, when the facing surface of the thin film portion approaches the wafer within a predetermined distance, the surface of the thin film portion faces the wafer. Before the surface comes into contact with the wafer, the mechanical stopper makes point contact with the wafer to prevent direct contact between the mask thin film portion and the wafer and surface adhesion.

Since the contact area between the mechanical stopper and the wafer is much smaller than the contact area between the mask thin film portion and the wafer, the suction force between the mechanical stopper and the wafer is smaller than the suction force between the mask thin film portion and the wafer.
Therefore, the exposure mask of the present invention can prevent damage such as dropping of the mask thin film portion that occurs when the mask adhered to the wafer is released.

  In addition, by interposing a mechanical stopper between the mask thin film portion and the wafer, the opposing surface of the thin film portion is prevented from approaching the wafer more than a predetermined distance, and the mask thin film portion and the wafer are close to each other. An increase in suction force between the two is prevented. This reduces the force required to separate the mask approaching the wafer.

  In addition, by forming such a mechanical stopper with a conductive material and detecting the continuity between the exposure mask and the wafer using an electron beam exposure device, it is immediately detected that the mechanical stopper is in point contact with the wafer. It becomes possible to do.

  The exposure mask according to the present invention will be described below with reference to the accompanying drawings. The present invention can be applied to any exposure mask used in an electron beam exposure apparatus, but is particularly suitable for a mask for an electron beam proximity exposure apparatus of a proximity exposure system.

  FIG. 6 is an explanatory view of an exposure mask according to the present invention. As shown in the top view of FIG. 6A, the exposure mask 30 has a thin film portion 32 surrounded by a relatively thick outer edge 34, and this thin film portion 32 exposes a wafer as a sample. An opening 33 corresponding to the pattern and a projection 35 that functions as a mechanical stopper are provided.

  As shown in the side sectional view of FIG. 6B, the protrusion 35 is provided on the surface of the thin film portion 32 facing the wafer while avoiding the opening 33. Such a protrusion 35 can be realized by various methods. In particular, after the thin film portion 32 and the opening 33 are formed on the mask 30 by a technique such as dry etching, the thin film is formed by a focused ion beam assisted deposition method. It is preferable to form the portion 30 by depositing a carbon film or a silicon oxide film on the wafer facing surface.

Now, it is assumed that the thin film portion 32 bends and approaches the wafer 40 as described above. This state is shown in FIG. Various suction forces such as a Coulomb force due to the electric charges irradiated to the wafer 40 and accumulated are applied between the thin film portion 32 of the mask 30 and the wafer 40.
Since the suction force acts more strongly as the distance between the thin film portion 32 and the wafer 40 becomes smaller, when the thin film portion 32 approaches more than a certain amount, the suction force attracts the wafer 40 further, and FIG. 7B shows. As shown, it is bonded to the wafer 40.

  When the thin film portion 32 and the wafer 40 are bonded in this manner, they are bonded to each other with a relatively large bonding area. Accordingly, a strong adhesive force acts between the thin film portion 32 and the wafer 40, and if the thin film portion 32 is to be separated from the wafer 40 as it is, the thin film portion 32 is dropped and the mask 30 is damaged.

  In the exposure mask 30 of the present invention, as shown in FIG. 7C, since the protrusion 35 is provided on the surface of the thin film portion 32 facing the wafer 40, even if the thin film portion 32 is attracted to the wafer 40, the thin film Prior to the wafer facing surface of the portion 32 reaching the wafer 40, the protrusion 35 contacts the wafer 40 and prevents the thin film portion 32 and the wafer 40 from being bonded to each other.

At this time, a force of the same kind as the suction force acting between the thin film portion 32 and the wafer 40 also acts on the contact point between the protrusion 35 and the wafer 40, but the contact area of the contact point is small, so The total amount is small. Therefore, even if the thin film portion 32 is separated from the wafer 40, the thin film portion 32 does not fall off.
In addition, the distance between the thin film portion 32 and the wafer 40 is maintained at a predetermined height (for example, 10 μm) or more by the projecting portion 35 interposed therebetween. The suction force acting between them is prevented from becoming extremely strong.

  In this manner, the protrusion 35 functions to support the thin film portion 32 by overcoming the attractive force acting between the thin film portion 32 and the wafer 40. Therefore, it is preferable that the protrusions 35 are provided in at least three places so that the installation points form a surface, and the support point of the thin film portion 32 is the surface.

  Incidentally, an exposure mask having a thin film portion as described above includes an exposure mask provided with a beam portion (strut) for supporting the thin film portion in order to increase the mechanical strength of the thin film portion. The structure is shown in FIG.

  8A is a top view of an exposure mask provided with a beam portion, FIG. 8B is a side view thereof, and FIG. 8C is a perspective view. As shown in the figure, a beam 37 is formed on the thin film portion 32 of the exposure mask 30 to support the thin film portion 32 on the surface opposite to the wafer-facing surface. Have been separated.

In the vicinity of such a beam 37, there is no opening 33 and the mechanical strength is high. Therefore, the position on the exposure mask surface where the mechanical stopper (protrusion) of the exposure mask according to the present invention is provided is preferably a position where the beam 37 is formed.
As described above, when the above-described beam structure is provided in the exposure mask, the above-described mechanical stopper (protrusion) 35 is placed on the surface of the exposure mask 30 on which the beam 37 is formed on the wafer facing surface of the thin film portion 34. The upper position is preferably provided (see FIG. 9).

  Further, as described above, the protruding portion 35 can be formed of materials having various electrical properties such as carbon as a conductive material and silicon oxide as an insulating material. By forming the protrusions 35 with a conductive material, it is possible to detect the presence or absence of contact between the protrusions 35 and the wafer 40 by a continuity check between the mask 30 and the wafer 40.

FIG. 10 is a configuration diagram of an electron beam proximity exposure apparatus having a function of detecting contact between the protrusion 35 and the wafer 40. Since the configuration of the electron beam proximity exposure apparatus has a configuration similar to the configuration shown in FIG. 1, the same functional parts are denoted by the same reference numerals and the description thereof is omitted.
As shown, the column 10 of the electron beam proximity exposure apparatus 1 includes an electron gun 14 that generates an electron beam 15, an irradiation lens 18 that converts the electron beam 15 into a parallel beam, a main deflector 20, and a sub deflector 50. Is provided.

  The chamber 8 of the electron beam proximity exposure apparatus 1 is provided with a mask 30 having a projection 35 as a mechanical stopper on the mask facing surface of the thin film portion 32, and the wafer 40 is coated with a resist layer 42 on the exposure surface. Then, it is held by a wafer chuck 44 provided on the XY stage 46.

Further, the electron beam proximity exposure apparatus 1 includes a conduction detector 60 that detects conduction between the mask 30 and the wafer 40.
As described above, since the projecting portion 35 is formed of a conductive material, when the conductive material is used for the material of the wafer 30 and the resist layer 42, the projecting portion 35 and the resist layer 42 are masked by contact. 30 and the wafer 40 are electrically connected. The electron beam proximity exposure apparatus 1 detects the presence / absence of contact between the projection 35 and the wafer 40 by detecting the conduction between the mask 30 and the wafer 40 by the conduction detector 60.

  In order to detect the presence or absence of contact between the protrusion 35 and the wafer 40 by the contact detection function of the electron beam proximity exposure apparatus described above, the protrusion 35 is preferably formed of a conductive material. After depositing an insulating material such as silicon oxide in a protruding shape on the portion 35, the contact point of the protruding portion 35 and the mask 30 are sealed by sealing a conductive film such as a silicon film or a metal film by CVD or sputtering. And may be formed so as to be conductive.

It is a basic block diagram of the conventional electron beam proximity exposure apparatus. It is a figure which shows the conventional exposure mask. It is explanatory drawing of the scanning method of the electron beam of an electron beam proximity exposure apparatus. It is a figure which shows a mode that the inclination of an electron beam is controlled by a sub deflector. It is explanatory drawing of mask distortion correction. It is FIG. (1) which shows the exposure mask which concerns on this invention. It is a figure which shows a mode that adhesion | attachment with a wafer is prevented with the exposure mask of this invention. It is a figure which shows the exposure mask provided with the beam structure which supports a thin film part. It is FIG. (2) which shows the exposure mask which concerns on this invention. It is a block diagram of the electron beam proximity exposure apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electron beam proximity exposure apparatus 8 ... Chamber 10 ... Electron optical column (column)
DESCRIPTION OF SYMBOLS 12 ... Electron gun 15 ... Electron beam 21 ... Scanning means 30 ... Exposure mask 32 ... Thin film part 33 ... Opening 34 ... Outer edge part 35 ... Projection part 40 ... Wafer 42 ... Resist layer

Claims (6)

A thin film portion having an opening corresponding to a pattern to be exposed on the wafer;
A mechanical device is provided on a surface of the thin film portion that faces the wafer, and contacts the wafer when the facing surface of the thin film portion approaches the wafer within a predetermined distance, and prevents contact between the thin film portion and the wafer. An exposure mask for electron beam exposure, comprising: a stopper.   The exposure mask according to claim 1, wherein the mechanical stopper is a protrusion formed of a conductive material. In the thin film portion, a beam that supports the thin film portion is formed on a surface that does not face the wafer,
3. The exposure mask according to claim 1, wherein the mechanical stopper is provided on a surface of the thin film portion facing the wafer on a position on the exposure mask surface on which the beam is formed.   The exposure mask according to any one of claims 1 to 3, wherein the exposure mask is an electron beam proximity exposure mask provided in proximity to the wafer. An electron beam exposure apparatus that irradiates the exposure mask according to claim 2 with an electron beam and exposes a pattern on the surface of the wafer with the electron beam passing through the exposure mask,
An electron beam exposure apparatus comprising a conduction detector for detecting conduction between the exposure mask and the wafer.   6. The electron beam exposure apparatus according to claim 5, wherein the exposure mask is provided close to the wafer.

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