JPH0541348A - Electron beam aligner and method of inspecting lithographic pattern - Google Patents

Abstract

PURPOSE:To inspect a blocking mask without detaching it from an aligner by a method wherein an opening pattern, on the blocking mask, which has been projected on a screen is scanned. CONSTITUTION:The image of an opening part on a blocking mask 110 is converged on a blanking aperture plate 117 by means of a controller 300. In order to scan the image, the controller 300 forms scanning signals Sx, Sy and supplies them to an alignment coil 127. The alignment coil deflects an electron beam in accordance with the scanning signals Sx, Sy. As a result, the image is moved on the blanking aperture plate 117. In addition, the controller 300 generates a synchronizing signal SYNC and supplies it to an image processing unit 302. The image processing unit 302 reproduces the image on the basis of the following: an input signal which is supplied from a detector 301 and which indicates the arrival of the electron beam; and the synchronizing signal SYNC which indicates the scanning operation of the electron beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to the manufacture of semiconductor devices, and more particularly to an electron beam exposure apparatus for drawing a semiconductor pattern on a semiconductor substrate with an electron beam, and an inspection method for inspecting the drawn pattern.

For patterning semiconductors in the submicron size, it is convenient to use an electron beam exposure apparatus. In the electron beam exposure apparatus, a finely converged electron beam is used to draw a semiconductor pattern on a semiconductor substrate, so that a resolution of 1 μm or less can be easily achieved.
On the other hand, the conventional electron beam exposure apparatus has a problem that the throughput is low due to the system constraint that the semiconductor pattern has to be drawn with one stroke of the converged electron beam.

To alleviate the problem of low throughput, so-called block exposure technology has been proposed.
According to this method, the electron beam is shaped corresponding to the basic pattern of the semiconductor pattern, and the selected basic pattern is repeatedly exposed (shot) to draw a desired semiconductor pattern on the substrate. The block exposure technique is particularly suitable for manufacturing a semiconductor device having a repeating basic pattern, such as a memory.

[0004]

2. Description of the Related Art FIG. 9 shows a structure of a conventional electron beam exposure apparatus using a block exposure technique. Referring to the drawings, the electron beam exposure apparatus generally includes an electron optical system 100 that forms a focused electron beam and a control system 200 that controls the electron optical system 100.

The electron optical system 100 includes an electron gun 104 which serves as an electron beam source. The electron gun 104 has a cathode electrode 107.
And a grid electrode 102 and an anode electrode 103, and emits an electron beam as a divergent beam in a substantially predetermined optical axis direction.

The electron beam thus formed by the electron gun 104 is shaped when passing through the opening 105a formed in the aperture plate 105. Aperture plate 1
05 is provided so that the opening 105a is aligned with the optical axis O, and shapes the cross section of the incident electron beam into a rectangular shape.

The electron beam thus shaped is incident on the electron lens 107a having a black dot on the opening 150a. At that time, the incident electron beam is converted into a parallel beam and enters the electron lens 107b.
It is converged on the block mask by b. Lens 10
7b then projects the image of the rectangular opening 105a onto the block mask. As shown in FIG. 10, the block mask 110 has basic patterns 7a, 7b, 7c, ... Of semiconductor display patterns that are not drawn on the substrate in the form of openings, and when the electron beam passes therethrough, The cross section is shaped according to the shape of the opening.

The deflector 1 is used to deflect the electron beam that has passed through the electron lens 107b and select a desired aperture.
11, 112, 113 and 114 are provided. Of these, the deflector 111 deflects the electron beam so as to deviate from the optical axis O according to the control signal SM1. On the other hand, the deflector 112 returns the electron beam parallel to the optical axis O according to the control signal SM2. After passing through the block mask 110, the deflector 113 responds to the control signal SM3 by
The electron beam is deflected in the optical axis direction, and further the deflector 114
Makes the electron beam coincide with the optical axis O according to the control signal. The block mask 110 itself is provided so as to be movable in a direction perpendicular to the optical axis, whereby the block mask 1
It becomes possible to select all the openings formed on the entire surface of 10.

The electron beam that has passed through the block mask 110 is converged at a point f1 on the optical axis by the electron lenses 108 and 116. At that time, the image of the selected opening on the block mask 110 is reduced and imaged at the point f1. The electron beam thus converged is further subjected to the blanking aperture 11 formed in the blanking plate 117.
After passing through 7a, an electron lens 11 for forming another reduction optical system on the surface of the substrate held on the moving stage 126.
It is converged by 9,120. Here, the electronic lens 12
0 acts as an objective lens, a correction coil 120 for focus correction and Sting correction, and an electron beam on the substrate 1
Deflection coils 124, 1 for moving on the surface of 23
Also includes 25.

The blanking aperture 117a is provided so as to coincide with the optical axis O, and is used for centering the electron beam. For this purpose, various adjustment coils 127 ...
130 is used. At the start of exposure, an electron beam is emitted and the adjustment coils 127 to 130 are controlled to detect that the electron beam reaches the stage 126. During this process, the mask 110 is removed from the optical path O to allow the electron beam to pass freely. Alternatively, the mask 11
A large opening may be formed at 0 to allow the electron beam to freely pass therethrough.

The state of FIG. 9 shows the operating state of the electron beam exposure apparatus, in which the electron beam is focused on the surface of the substrate 123. In this state, the focus f1 formed by the optical system formed by the lenses 108 and 116 is formed above the blanking aperture plate 117 in order to achieve the desired reduction.

In order to control the exposure operation, the electron beam exposure apparatus of FIG. 9 uses a control system 200. Here, the control system 200 includes a magnetic tape device 201 and a magnetic disk device 20.
2, 203 and the like have storage devices, and device patterns of semiconductor devices to be written are stored in these storage devices. In the illustrated example, the magnetic tape device 201 is used to store parameters, while the magnetic disk device 202 is used.
Are used to store the exposure pattern data. Also,
The magnetic disk device 203 stores the opening pattern on the block mask 110.

The data stored in the storage device is the CPU 2
Read by 04, and sent to the interface 205 after decompression. Here, the data designating the pattern on the block mask 110 is extracted, and the data memory 2
It is stored in 06. The data stored in the data memory 206 is then sent to the first control unit 207 and the control signals SM1 to SM4 are formed. These signals are then sent to the deflectors 111-114. The control unit 207 shapes the control signal of the mask moving mechanism 209, and thereby moves the block mask 110 in the direction orthogonal to the optical axis O. As a result of the deflection by the deflectors 111 to 114 and the horizontal movement of the block mask 110, it becomes possible to address any opening on the mask 110 with an electron beam.

Further, the first control unit 207 sends a control signal to the blanking control unit 210, and the blanking control unit 210 outputs a blanking signal for cutting off the electron beam in response thereto. This blanking signal is converted into an analog signal SB by the D / A converter 211, while the analog signal SB is supplied to the deflector 115 that deflects the electron beam from the optical axis. As a result, the electron beam deviates from the blanking aperture 117a and the substrate 1
23 disappears from the surface. Further, the control unit 207 outputs the pattern correction data Hadj and supplies it to the D / A converter. The D / A converter 208 forms the control signal Sadj according to this, and supplies this to the deflector 106 provided between the electron lens 107a and the electron lens 107b. As a result, it is possible to change the electron beam passing through the selected opening of the mask 110 into an indeterminate shape. This feature is used when the desired electron beam shape does not match that obtained from the opening on the block mask 110.

The interface 205 also extracts the data controlling the movement of the electron beam on the substrate 123 and sends it to the second control unit 212. Control unit 21
Reference numeral 2 forms a control signal for controlling the deflection of the electron beam on the surface of the substrate 123, which is transmitted to the wafer deflection control unit 21.
Send to 5. The wafer deflection control unit 215 generates a control signal in response to this, and outputs the control signal to the D / A converters 216 and 21.
Send to 7. The D / A converters 216 and 217 form deflector drive signals SW1 and SW2, respectively, and these are generated.
4, 125, to deflect the electron beam. that time,
The position of the stage 126 is detected by the laser interferometer 214 and the wafer deflection control unit 215 modifies the output signal. In response to this, the drive signals SW1 and SW2 are converted. In addition, the second control unit 212 includes the stage 12
A control signal for controlling the lateral movement of 6 is output.

[0016]

In such a conventional block exposure apparatus, it is necessary to inspect the pattern of the opening on the block mask 110 for defects quite often. The size of each pattern on the block mask 110 is about several 100 μm square, and such a pattern is on the mask 110 several hundreds to several hundreds.
It is formed on a scale of 0. Therefore, the risk of damaging some of them cannot be ignored. Such damage may occur, for example, during the manufacturing process of the mask 110 or during its use. In particular, during use, the thin membrane in the block mask 110 is deformed by the energy of the electron beam. Therefore, it is necessary to inspect the block mask 110 before exposure. Further, such inspection is preferably performed at regular intervals during the exposure operation.

Conventionally, such a block mask 110 is used.
Inspection of the upper opening pattern was done by microscopic observation. That is, the block mask 110 is removed from the optical system 100 of the electron beam exposure apparatus and set under a microscope. However, such an inspection process is time-consuming and increases the risk that the block mask 110 will be damaged during the mounting / removing process. Furthermore, in such a process, dust attached to the mask 110 after the microscopic inspection cannot be detected.

An object of the present invention is to provide an electron beam exposure apparatus which can inspect an opening pattern on a block mask without removing the block mask.

[0019]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by generating an electron beam and emitting it to an object along the optical axis; and an electron beam source provided on the optical axis. Beam shaping means having at least one opening pattern for passing the beam and shaping the cross section of the electron beam into a desired shape; and a beam shaping means provided along the optical axis between the beam shaping means and the object. Focusing means for focusing the electron beam shaped by the means onto the object, and projecting an image of the opening on the beam shaping means through which the electron beam passes onto the object; the beam shaping means and the object on the optical axis A screen provided with a through hole for blocking the electron beam from the object when the electron beam deviates from the optical axis and provided with a through hole corresponding to the optical axis; Control and beam shaping hands Control means for projecting an image of the opening of the beam shaping means through which the electron beam has passed onto the upper surface of the screen when inspecting the pattern of the upper opening; and detecting the image of the opening projected on the screen. And an electron beam exposure apparatus capable of inspecting a pattern drawn on an object.

[0020]

According to the present invention, by inspecting the opening pattern projected on the screen, the pattern on the block mask can be inspected without removing the block mask from the electron beam exposure apparatus, and the efficiency of the exposure process can be improved. Can be improved and damage to the mask pattern can be reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIG. 11 corresponding to the conventional example and FIG. 1 corresponding to the present invention. Here, FIG. 11 corresponds to FIG. 9 and shows a normal state in which the image of the opening on the block mask 110 is formed on the surface of the substrate 123. On the other hand, FIG. 1 shows a state in which an image of the opening pattern on the block mask 110, which is a feature of the present invention, is formed on the blanking aperture plate 117.

Referring to FIG. 11, the electron beam formed by the electron mirror 104 and shaped by the shaping opening 105a is converged on the block mask 110, and the block mask 1 is formed.
A rectangular pattern of the opening 105 a is formed on the surface 10.
The electron beam is further shaped by passing through the mask 110, and lenses 108, 116 and lenses 119,
It is converged on the substrate by 122. As a result, a reduced image of the opening on the block mask 110 is formed on the substrate 123. The reduction optical system formed by the lenses 108 and 116 forms the focal point f1 above the blanking aperture plate 117.

In the present invention, the strength of the electron lens 108 is slightly reduced. This situation is shown as lens 108 'in FIG. Referring to FIG. 1, the focal point f1 of the lens systems 108 and 116 is, as a result, the blanking aperture plate 11
Move to point f2 on 7. As a result, the image of the pattern on the mask 110 is formed on the blanking aperture plate 117. The present invention thus detects the image formed on the blanking aperture plate and inspects the pattern of the opening on the block mask 110. Figure 2
The detection of the image on the blanking aperture plate 117 is shown.
As shown in FIG. 2, the electron beam EB is deflected so that the image on the block mask 110 does not move. As a result, the aperture pattern image moves on the blanking aperture plate 117 according to the deflection of the electron beam EB. At that time, the image is on the plate 1 at the blanking aperture 117a.
It passes through 17 and reaches the substrate 123. Therefore, by detecting the passage of the electron beam through the blanking aperture plate 117 in synchronization with the scanning of the electron beam, the aperture pattern image of the block mask 110 projected onto the blanking aperture plate 117 can be reproduced. ..

FIG. 3 shows an electron beam exposure apparatus according to an embodiment of the present invention. In FIG. 3, the parts described previously are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, a controller 300 is provided to control the intensity of the electron lens 108, so that the image of the opening on the block mask 110 is converged on the blanking aperture plate 117 during inspection. Further, a detection system 300A for detecting the arrival of the electron beam on the substrate 123 is provided. The detection system 300A is an electron detector 3 that detects backscattered electrons emitted in response to an incident electron beam.
01 and an image processing unit 302 which is supplied with the output of the detector 301 and reproduces an image on the blanking aperture plate 117. The image reproduced by the image processing unit 302 is displayed on the display device 303. It is convenient to use SEM as the detection system 300A.

In order to scan the image on the blanking aperture plate 117, the controller 300 causes the scanning signal Sx,
Sy is formed and is supplied to the alignment coil 127 adjacent to the electron mirror 140. The alignment coil 127 is provided for axis alignment of the electron beam, but deflects the electron beam according to the scanning signals Sx and Sy, and as a result, an image is displayed on the blanking aperture plate 117. Move as shown in 5. Further, the controller 300 generates a synchronization signal SYNC and supplies it to the image processing unit 302. The image processing unit 302 reproduces an image based on an input signal which is supplied from the detector 301 and which represents arrival of the electron beam and a synchronization signal SYNC which represents scanning of the electron beam.

FIG. 4 shows the scanning of the image on the blanking aperture plate 117.

According to the deflection of the electron beam caused by the scanning signal Sx, the image on the blanking aperture plate 117 can be moved by the full width of the image in the X-direction and, at the same time, in the Y direction perpendicular to the X direction. , Are moved according to the scanning signal Sy. Here, the X-direction is the horizontal scanning direction in a normal television, and the Y direction is the vertical scanning direction. In scanning in the Y direction, the image is moved by an amount corresponding to the diameter of the opening 117a.

As described above, the electron beam EB reaching the surface of the substrate 123 is detected by the detector 310. The detector 301 simply detects the arrival / block of the electron beam corresponding to the image C on the blanking aperture plate 17. That is, in inspecting the pattern on the mask 110, no pattern image is formed on the substrate 123.

FIG. 5 shows the synthesis of the reproduced image performed by the image processing unit 302 on the basis of the output signal of the detector 301 and the synchronization signal SYNC.

Referring to FIG. 5, the output of the detector 301 is detected line-sequentially by repeating scanning in the X direction. The synchronization signal SYNC includes a synchronization signal component X in the X-direction and a synchronization signal component Y in the Y-direction, and the deflection control signal S
x is changed according to the synchronization signal component X. Each time the scanning in the X direction is performed, the size of the deflection control means Sy is changed by a predetermined amount, and thereafter, the scanning in the X direction is repeated. As a result, the image on the blanking aperture plate 117 is reproduced and displayed on the display device 303.

Based on the image displayed on the display device 303, in the subsequent exposure process, measures such as not using the opening pattern determined to have a defect are taken.

6 and 7 show general operations of the electron beam exposure apparatus according to the present invention.

In the first step 107, the controller 300 controls the electron lens 108 to emit the electron beam.
It is converged to a point f1 on the blanking aperture plate 117. In the next step 102, one of the openings on the mask 110 is selected by driving the deflectors 111 to 114. Further, in step 103, the drive signal S
The mask 110 is scanned with the electron beam 110 by driving the alignment coil 127 with x and Sy. At the same time, in step 104, the detection system 300 detects the arrival of the electron beam at the substrate 123 in synchronization with the scanning. Further, in step 105, the image on the flanking aperture plate 117 is reproduced by the output signal of the detector 301 and the synchronization signal SYNC. Further, step 10
At 6, the pattern displayed on the display is inspected. If the selected opening pattern is defective, the pattern is registered as a defective pattern.

When the inspection of all the openings on the mask 110 is completed in step 107, the controller 300 focuses the electron beam on the point f1. After this, a normal exposure process is performed in step 109, avoiding the defective opening.

In the present invention, since the opening pattern on the block mask 110 can be checked without removing the mask from the optical system, various problems associated with removing the block mask 110 at the time of inspection are solved. Can be resolved. In particular, the present invention is effective when the openings are formed on the mask 110 with redundancy. Further, the pattern inspection can be automatically performed by the pattern matching technique.

The detection and reproduction of the image on the blanking aperture plate 117 is not limited to the above scanning method, and other means may be used.

FIG. 8 shows another embodiment of the present invention. 8, parts corresponding to those in FIG. 4 are designated by the same reference numerals, and description thereof will be omitted.

In this embodiment, the intensity of the electron lens 107b is reduced, and the electron beam remains parallel to the mask 1
The light passes through 10 and enters the electron lens 108. When passing through the mask 110, the electron beam is shaped according to the opening pattern.

The electron lens 108 is driven so as to have a high intensity, so that the electron beam is focused on a point f3 between the lens 100 and the lens 116. Lens 11
After passing through 6, the electron beam becomes a parallel beam and strikes the blanking aperture plate 117. At that time, mask 1
Ten shadows are projected on the blanking aperture plate 117, and by detecting the pattern thus projected, it is possible to inspect the pattern on the mask 110.

The present invention is not limited to the above embodiments, but various modifications and deflections are possible.

[0042]

According to the present invention, a blanking aperture plate is used as a screen, the electron optical system is controlled to project an aperture pattern on the block mask onto the screen, and the pattern is scanned to scan the pattern on the block mask. The opening pattern can be inspected without being removed from the electron beam exposure apparatus, the throughput of the exposure process can be improved, and the projection of the block mask can be avoided.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle of the present invention.

FIG. 2 is another diagram showing the principle of the present invention.

FIG. 3 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 4 is a diagram showing scanning in the embodiment of the present invention.

FIG. 5 is another diagram showing scanning in the embodiment of the present invention.

FIG. 6 is a diagram showing an exposure process using the electron beam exposure apparatus according to the present invention.

FIG. 7 is another diagram showing an exposure process using the electron beam exposure apparatus according to the present invention.

FIG. 8 is a diagram showing another embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a conventional electron beam exposure apparatus.

FIG. 10 is a diagram showing a block mask used in a conventional electron beam exposure apparatus.

FIG. 11 is a diagram showing normal drawing by a conventional electron beam exposure apparatus.

[Explanation of symbols]

 100 electron optical system 101 cathode electrode 102 grit electrode 103 anode electrode 104 electron gun 105 aperture plate 105a opening 107a electron lens 107b electron lens 110 block mask 111 to 114 deflector 108 electron lens 116 electron lens 117 blanking plate 117a blanking aperture 119 electron lens 120 electron lens 123 substrate 124, 125 deflection coil 127-130 adjusting coil 126 stage 200 control system 201 magnetic tape device 202 magnetic tape device 203 magnetic tape device 204 CPU 205 interface 206 data memory 207 first control unit 209 mask Moving mechanism 210 Blanking control unit 211 D / A converter 208 D / A converter 215 Wafer bias Direction control unit 216, 217 D / A converter 214 Laser interferometer 215 Deflection control unit 300 Controller 300A Detection system 301 Electronic detector 302 Processing unit 303 Display device

Claims (5)

[Claims] 1. An electron beam source which generates an electron beam and emits the electron beam to an object along the optical axis; and at least one opening pattern which is provided on the optical axis and allows the electron beam to pass therethrough, Beam shaping means for shaping the cross section of the electron beam into a desired shape; provided along the optical axis between the beam shaping means and the object, and focusing the electron beam shaped by the beam shaping means on the object. Focusing means for projecting an image of the opening on the beam shaping means through which the electron beam has passed, onto the object; on the optical axis, the electron beam deviates from the optical axis between the beam shaping means and the object. And a screen provided with a through hole for blocking the electron beam and allowing the electron beam to pass therethrough corresponding to the optical axis; and a pattern of openings on the beam shaping means by controlling the converging means. When inspecting A control means for projecting an image of the opening of the beam shaping means through which the child beam has passed onto the upper surface of the screen; and a detection means for detecting the image of the opening projected on the screen, and drawing on the object Electron beam exposure apparatus capable of inspecting the formed pattern. 2. The detecting means passes through a hole on the screen, and a deflecting means for deflecting the electron beam to move an image projected on the screen to a hole formed in the screen. A detector that detects an electron beam that reaches an object, and an image combining circuit that is supplied with the output signal of the detector and that reproduces the image projected on the screen in synchronization with the movement of the image on the screen. The electron beam exposure apparatus according to claim 1, further comprising: 3. The control means supplies a drive signal to the deflection means to move an image on the screen, further forms a synchronization signal in synchronization with the drive signal, and supplies the synchronization signal to an image synthesizing circuit. 2. The electron beam exposure apparatus according to claim 1, wherein the image synthesizing circuit reproduces the image projected on the screen in synchronization with the synchronizing signal based on the output of the detector. 4. The converging means includes an electron lens provided on the optical axis between the beam shaping means and the screen to form a reduction electron optical system, and the electron lens is supplied from the control means. The electron beam exposure apparatus according to claim 1, wherein the electron beam exposure apparatus has an intensity determined by a drive signal, and the control unit changes the intensity of the electron lens when inspecting a pattern on the beam shaping unit. 5. A method of inspecting a pattern drawn by an electron beam on an object in an electron beam exposure apparatus, comprising: emitting an electron beam from an electron beam source toward the object along an optical axis; The electron beam is shaped according to the pattern of the openings by passing through the openings provided on the optical axis; the electron beam is projected on a screen provided at a position away from the object on the optical axis. Forming an image on the screen corresponding to the opening pattern; detecting the image on the screen.