# US 5,708,276 A · Electron-beam exposure device and a method of detecting a mark position for the device

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- Number: US 5,708,276 A
- Document ID: US5708276A
- Status: Granted
- Kind: A
- Application number: 08/600,456
- Filed: 1996-02-13
- Granted: 1998-01-13
- Earliest claimed: 1995-07-20
- Assignees: Fujitsu Limited
- Inventors: Tatsuro Ohkawa; Kawakami Kenichi; Yoshihisa Ooae; Tohru Ikeda; Kazushi Ishida
- Web page: https://patentgrep.com/patent/US5708276A

## CPC

- H01J 37/3045: {Object or beam position registration}
- H01J 2237/24495: Signal processing, e.g. mixing of two or more signals
- H01J 2237/30438: Registration
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

An electron-beam exposure device having at least one deflector for deflecting an electron beam and detecting a position of a position-detection mark with the electron beam includes a plurality of detectors detecting electrons scattered from the position-detection mark, a plurality of amplifiers, each of the amplifiers amplifying an output of a corresponding one of the detectors, and a setting unit for setting amplification factors of the amplifiers such that a magnitude of an output from each of the amplifiers is constant irrespective of a deflected position of the electron beam at a time of detection of the position of the position-detection mark.

## Claims

### Claim 1

An electron-beam exposure device having at least one deflector for deflecting an electron beam, and detecting a position of a position-detection mark with said electron beam, said electron-beam exposure device comprising:
a plurality of detectors detecting electrons scattered from said position-detection mark;
a plurality of amplifiers, each of said amplifiers amplifying an output of a corresponding one of said detectors; and
setting means for setting amplification factors of said amplifiers such that a magnitude of an output from each of said amplifiers is constant irrespective of a deflected position of said electron beam at a time of detection of said position of said position-detection mark.

### Claim 2 (depends on 1)

The electron-beam exposure device as claimed in claim 1, wherein said detectors comprise at least four detectors arranged symmetrically around an axis of said electron beam.

### Claim 3 (depends on 2)

The electron-beam exposure device as claimed in claim 2, wherein said at least four detectors comprise pairs of detectors, each one of said pairs having a first detector and a second detector arranged symmetrically with respect to said axis, said output from said first detector and said output from said second detector being added.

### Claim 4 (depends on 1)

The electron-beam exposure device as claimed in claim 1, wherein said setting means comprises:
a plurality of registers, each of which is connected to a corresponding one of said amplifiers and stores one of said amplification factors of said corresponding one of said amplifiers; and
a controlling unit setting said amplification factors in said registers.

### Claim 5 (depends on 4)

The electron-beam exposure device as claimed in claim 4, wherein said position-detection mark comprises a first groove extending in an X direction and a second groove extending in a Y direction, and said detectors comprises:
a first detector arranged in a +X and +Y direction with respect to said position-detection mark;
a second detector arranged in a +X and -Y direction with respect to said position-detection mark;
a third detector arranged in a -X and +Y direction with respect to said position-detection mark; and
a fourth detector arranged in a -X and -Y direction with respect to said position-detection mark, and wherein said position-detection means comprises:
first adding means for adding outputs of said first detector and said second detector;
second adding means for adding outputs of said third detector and said fourth detector;
third adding means for adding outputs of said first detector and said third detector;
fourth adding means for adding outputs of said second detector and said fourth detector;
means for detecting positions of edges of said second groove by analyzing outputs of said first adding means and said second adding means when said electron beam is scanned in said X direction; and
means for detecting positions of edges of said first groove by analyzing outputs of said third adding means and said fourth adding means when said electron beam is scanned in said Y direction.

### Claim 6 (depends on 1)

The electron-beam exposure device as claimed in claim 1, wherein said setting means comprises:
map memories storing said amplification factors and receiving said deflected position as an address thereof, said map memories outputting said amplification factors stored at said address to said amplifiers; and
a controlling unit storing said amplification factors corresponding to said deflected position in said map memories in advance.

### Claim 7 (depends on 6)

The electron-beam exposure device as claimed in claim 6, further comprising means for obtaining said amplification factors through a linear interpolation when said deflected position corresponds to a point between two successive addresses of said map memories.

### Claim 8 (depends on 1)

The electron-beam exposure device as claimed in claim 1, wherein said setting means comprises:
an interpolation circuit receiving said deflected position as a point (x, y) and outputting said amplification factors as .SIGMA.A.sub.ij x.sup.i y.sup.j to said amplifiers; and
a controlling unit setting coefficients A.sub.ij in said interpolation circuit in advance.

### Claim 9 (depends on 1)

The electron-beam exposure device as claimed in claim 1, wherein each of said amplification factors is proportional to r.sup.2 said r being a distance between said deflected position and a corresponding one of said detectors.

### Claim 10 (depends on 9)

The electron-beam exposure device as claimed in claim 9, wherein each of said amplification factors is .alpha.r.sup.2 /r.sub.O.sup.2, said .alpha. being a reference amplification factor of a corresponding one of said amplifiers when said electron beam is positioned at an axis of said electron beam, said r.sub.O being a distance between said axis and said corresponding one of said detectors.

### Claim 11 (depends on 1)

The electron-beam exposure device as claimed in claim 1, wherein each of said amplification factors is proportional to 1/.OMEGA., said .OMEGA. being a solid angle of a corresponding one of said detectors when said corresponding one of said detectors is viewed from said deflected position.

### Claim 12 (depends on 11)

The electron-beam exposure device as claimed in claim 11, wherein each of said amplification factors is .alpha..OMEGA..sub.O /.OMEGA., said .alpha. being a reference amplification factor of a corresponding one of said amplifiers when said electron beam is positioned at an axis of said electron beam, said .OMEGA..sub.O being a solid angle of said corresponding one of said detectors when said corresponding one of said detectors is viewed from a position of said axis.

### Claim 13 (depends on 1)

The electron-beam exposure device as claimed in claim 1, wherein each of said amplification factors is proportional to 1/V(X), said V(X) being obtained for an arbitrary position X by interpolating a detector output V(X.sub.j) of a corresponding one of said detectors, said V(X.sub.j) being measured by positioning said electron beam on a flat surface of a wafer at a plurality of points X.sub.j (j=1, 2, . . . , n).

### Claim 14 (depends on 13)

The electron-beam exposure device as claimed in claim 13, wherein each of said amplification factors is V.sub.O /V(X), said V.sub.O being a detector output of said corresponding one of said detectors when said electron beam is positioned at an axis of said electron beam.

### Claim 15

A method of detecting a position of a position-detection mark in an electron-beam exposure device which has at least one deflector for deflecting an electron beam and a plurality of detectors for detecting scattered electrons from said position-detection mark when said electron beam is positioned on said position detection mark, said method comprising the steps of:
a) detecting said scattered electrons by using said detectors;
b) amplifying an output of each of said detectors by a corresponding amplification factor so as to obtain said output having a constant magnitude independent of a deflected position of said electron beam;
c) adding for all of said detectors said output having a constant magnitude to obtain an added signal; and
d) analyzing a form of said added signal to detect said position of said position-detection mark.

### Claim 16 (depends on 15)

The method as claimed in claim 15, wherein said step b) comprises the steps of:
b1) calculating a value proportional to r.sup.2, said r being a distance between one of said detectors and said deflected position; and
b2) amplifying an output of said one of said detectors by a factor of said value proportional to r.sup.2.

### Claim 17 (depends on 16)

The method as claimed in claim 16, wherein said value proportional to r.sup.2 is .alpha.r.sup.2 /r.sub.O.sup.2, said .alpha. being a reference amplification factor for said one of said detectors when said electron beam is positioned at an axis of said electron beam, said r.sub.0 being a distance between said axis and said one of said detectors.

### Claim 18 (depends on 15)

The method as claimed in claim 15, wherein said step b) comprises the steps of:
b1) calculating a solid angle .OMEGA. of one of said detectors viewed from said deflected position; and
b2) amplifying an output of said one of said detectors by a factor proportional to 1/.OMEGA..

### Claim 19 (depends on 18)

The method as claimed in claim 18, wherein said factor proportional to 1/.OMEGA. is .alpha..OMEGA..sub.O /.OMEGA., said .alpha. being a reference amplification factor for said one of said detectors when said electron beam is positioned at an axis of said electron beam, said .OMEGA..sub.O being a solid angle of said corresponding one of said detectors when said corresponding one of said detectors is viewed from a position of said axis.

### Claim 20 (depends on 15)

The method as claimed in claim 15, further comprising the steps of:
e) positioning said electron beam having a constant beam size and a constant current density on a flat surface of a wafer at a plurality of points X.sub.j (j=1, 2, . . . , n); and
e) detecting an output V(X.sub.j) of one of said detectors, wherein said step b) comprises the steps of:
b1) obtaining an output V(X) for said deflected position by interpolating said output V(X.sub.j); and
b2) amplifying an output of said one of said detectors by a factor proportional to 1/V(X).

### Claim 21 (depends on 20)

The method as claimed in claim 20, wherein said factor proportional to 1/V(X) is V.sub.O /V(X), V.sub.O being an output of said one of said detectors when said electron beam is positioned at an axis of said electron beam.

### Claim 22

An electron-beam exposure device having at least one deflector for deflecting an electron beam, and detecting a position of a position-detection mark with said electron beam, said position-detection mark including at least one groove formed on a reference chip, said electron-beam exposure device comprising:
a plurality of detectors to detect electrons scattered from said position-detection mark:
position-detection means for detecting said position of said position-detection mark by detecting positions of edges of said position-detection mark, wherein at least one of said detectors in a position to receive none of electrons scattered by a side wall of a given one of said edges is used for obtaining a position of said given one of said edges.

### Claim 23 (depends on 22)

The electron-beam exposure device as claimed in claim 22, wherein said position-detection mark comprises a first groove extending in an X direction and a second groove extending in a Y direction, and said detectors comprise four detectors arranged in a +X direction, a -X direction, a +Y direction, and a -Y direction, respectively, with respect to said position-detection mark, and wherein said position-detection means comprises:
means for detecting positions of edges of said second groove by scanning said electron beam in said X direction, said positions of said edges of said second groove being detected by analyzing signal outputs of two of said detectors which are arranged in said +X direction and said -X direction; and
means for detecting positions of edges of said first groove by scanning said electron beam in said Y direction, said positions of said edges of said first groove being detected by analyzing signal outputs of two of said detectors which are arranged in said +Y direction and said -Y direction.

### Claim 24

A method of detecting a position of a position-detection mark in an electron-beam exposure device which has at least one deflector for deflecting an electron beam and at least one detector for detecting scattered electrons from said position-detection mark when said electron beam is positioned on said position detection mark, said position-detection mark comprising at least one groove formed on a reference chip, said method comprising the steps of:
a) positioning said electron beam on said position-detection mark by scanning said electron beam with said at least one deflector;
b) measuring an output of said at least one detector, said output being free from an effect of electrons scattered by a side wall of an edge of said position-detection mark; and
c) detecting a position of said edge by analyzing an edge signal of said edge appearing in said output.

### Claim 25

A method of detecting a position of a position-detection mark in an electron-beam exposure device which has at least one deflector for deflecting an electron beam and a plurality of detectors for detecting scattered electrons from said position-detection mark when said electron beam is positioned on said position detection mark, said position-detection mark comprising at least one groove formed on a reference chip, said method comprising the steps of:
a) positioning said electron beam on said position-detection mark by scanning said electron beam with said at least one deflector;
b) measuring outputs of said detectors, said outputs being free from an effect of electrons scattered by a side wall of an edge of said position-detection mark;
c) adding said outputs to obtain an added output; and
d) detecting a position of said edge by analyzing an edge signal of said edge appearing in said added output.

### Claim 26

An electron-beam exposure device having at least one deflector for deflecting an electron beam within a deflection field, and detecting a position of a position-detection mark with said electron beam, said electron-beam exposure device comprising:
a reference chip having an upper surface and a lower surface, said upper surface having a position-detection mark for calibrating a deflected position of said electron beam within said deflection field;
a chip holder holding said reference chip by having a fixed contact with said lower surface of said reference chip, said chip holder having a step-form portion lower than said lower surface of said reference chip;
a wafer holder having an upper surface and a first recess for storing said chip holder, said first recess having a bottom surface, an opening continuing to said upper surface, and a stopper surface located beneath said upper surface around said opening; and
a spring provided between said bottom surface of said first recess and said chip holder to urge said step-form portion of said chip holder against said stopper surface such that said upper surface of said reference chip is flush with said upper surface of said wafer holder.

### Claim 27 (depends on 26)

The electron-beam exposure device as claimed in claim 26, further comprising a wafer having another position-detection mark on an upper surface thereof for aligning said wafer with said electron beam, said electron beam being positioned on said upper surface of said wafer for drawing a pattern, wherein said wafer holder includes a second recess for storing said wafer, said upper surface of said wafer being flush with said upper surface of said wafer holder.

### Claim 28 (depends on 27)

The electron-beam exposure device as claimed in claim 27, further comprising a plurality of stoppers fixedly mounted on said upper surface of said wafer holder, said upper surface of said wafer being urged against said stoppers.

### Claim 29 (depends on 28)

The electron-beam exposure device as claimed in claim 28, further comprising a plurality of detectors detecting electrons scattered from one of said upper surface of said reference chip and said upper surface of said wafer, said stoppers being arranged such that said electrons scattered from said another position-detection mark on said upper surface of said wafer are free from obstruction before reaching said detectors.

### Claim 30

An electron-beam exposure device having at least one deflector for deflecting an electron beam within a deflection field, and detecting a position of a position-detection mark with said electron beam, said electron-beam exposure device comprising:
a reference chip having an upper surface and a lower surface, said upper surface having a position-detection mark for calibrating a deflected position of said electron beam within said deflection field;
a chip holder holding said reference chip by having a fixed contact with said lower surface of said reference chip;
a wafer holder having an upper surface and a first recess for storing said chip holder, said first recess having a bottom surface and an opening continuing to said upper surface; and
a screw fixedly mounting said chip holder to said bottom surface of said first recess such that said upper surface of said reference chip is flush with said upper surface of said wafer holder.

### Claim 31 (depends on 30)

The electron-beam exposure device as claimed in claim 30, further comprising a wafer having another position-detection mark on an upper surface thereof for aligning said wafer with said electron beam, said electron beam being positioned on said upper surface of said wafer for drawing a pattern, wherein said wafer holder includes a second recess for storing said wafer, said upper surface of said wafer being flush with said upper surface of said wafer holder.

### Claim 32 (depends on 31)

The electron-beam exposure device as claimed in claim 31, further comprising a plurality of stoppers fixedly mounted on said upper surface of said wafer holder, said upper surface of said wafer being urged against said stoppers.

### Claim 33 (depends on 32)

The electron-beam exposure device as claimed in claim 32, further comprising a plurality of detectors detecting electrons scattered from one of said upper surface of said reference chip and said upper surface of said wafer, said stoppers being arranged such that said electrons scattered from said another position-detection mark on said upper surface of said wafer are free from obstruction before reaching said detectors.

### Claim 34

A method of exposing a predetermined pattern on a wafer by using an electron-beam exposure device which has at least one detector for detecting scattered electrons from a position-detection mark when said electron beam is positioned on said position detection mark, said method comprising the steps of;
forming a reference chip integrally with a chip holder, said reference chip having a first position-detection mark on an upper surface thereof for calibrating a deflected position of said electron beam within a deflected field;
fixedly mounting said chip holder in a first recess of a wafer holder so that said upper surface of said reference chip is flush with an upper surface of said wafer holder;
detecting a position of said first position-detection mark by detecting electrons scattered from said first position-detection mark;
calibrating said deflected position of said electron beam within said deflected field based on said position of said first position-detection mark;
fixedly mounting said wafer in a second recess of said wafer hold, an upper surface of said wafer being urged against stoppers fixed on said upper surface of said wafer holder such that said upper surface of said wafer is flush with said upper surface of said wafer holder, said wafer having a second position-detection mark on said upper surface thereof;
detecting a position of said second position-detection mark by detecting electrons scattered from said second position-detection mark, said stoppers being arranged such that said electrons scattered from said second position-detection mark are free from obstruction before reaching said at least one detector;
aligning said wafer with said electron beam based on said position of said second position-detection mark; and
drawing said predetermined pattern on said upper surface of said wafer by using said electron beam.