JPH11354063A - Electron beam transfer device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the defective of sample wafers when abnormality such as abnormal increase in electron gun current is generated, prevent the trouble of a device, and provide a measure to quickly recover the failure of the device, even if the device fails. SOLUTION: This electron beam transfer device has thermocouples 18, 16, 13, 6, 12 arranged in an exciting coil 17a of a lens, a deflecting coil 15, an astigmatic correction coil 14, a forming opening 5 or a crossover opening 12. The thermocouples are connected to a controller 31, and the controller set controls so that when the temperature in either part of them exceeds the specified value, either the transfer operation is stopped, or the output of a cooling device in each part of the device is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an electron beam transfer apparatus intended to form fine and high-density patterns of m or less with high throughput. In particular, the present invention relates to an electron beam transfer device improved so as to prevent a decrease in pattern transfer accuracy due to a rise in temperature of each part of the device.

[0002]

2. Description of the Related Art A method of circulating a refrigerant (water, chlorofluorocarbon, helium, etc.) around a deflection coil so as not to cause a temperature rise of the deflection coil has been known (Japanese Patent No. 2659).
No. 471).

[0003]

In the prior art as described above, there is no particular problem in normal operation. However, a problem may occur when abnormalities occur, for example, when the room temperature rises abnormally or when the electron gun current becomes abnormally large. This is because there is a positive feedback characteristic that when the temperature of the coil rises, the resistance rises and the heat generation further increases and the temperature of the coil rises. In this case, since the coil is deformed and the transfer accuracy is reduced, the wafer during the transfer operation may become defective, or in extreme cases, the apparatus may break down.

The present invention provides a countermeasure for minimizing a defect of a sample wafer when such an abnormality occurs, preventing a failure of the apparatus, and promptly recovering the apparatus even if the apparatus becomes inoperable. The purpose is to do.

[0005]

In order to solve the above-mentioned problems, an electron beam transfer apparatus according to the present invention illuminates a mask having a pattern to be transferred onto a sensitive substrate with an electron beam and passes the mask through the mask to form a pattern. A device for transferring a pattern by forming an electron beam on a sensitive substrate and transferring the pattern; a temperature sensor disposed in an excitation coil, a deflection coil, an astigmatism correction coil, a shaping opening or a crossover opening of the lens; A control unit that receives a signal from a sensor and stops the transfer operation when the temperature of any one of the above parts exceeds a predetermined value, or increases the output of a cooling device of each part of the apparatus. And

In the present invention, it is preferable to first increase the output of the cooling device when the temperature of any of the above parts exceeds a predetermined value, and to temporarily stop the transfer operation when the temperature continues to rise thereafter. . At this time, it is preferable to reduce the current of each coil to suppress heat generation.

In an electron beam transfer apparatus of a partial batch exposure system (block exposure or the like) or a split transfer system having a wide transfer range, if the electron gun current becomes abnormally large, the heat generated in the forming opening or the crossover opening increases. However, these openings may be melted. By monitoring the temperature and increasing the flow rate of the cooling water or lowering the temperature of the cooling water so that the temperature does not exceed a predetermined value, melting of the opening can be avoided. Further, when a mark is not found due to mark detection or the like and mark scanning is performed for a long time at the end of the field of view, the temperature of the deflection coil may rise. By monitoring the coil temperature and improving the cooling capacity, in most cases, the value returns to the normal value, and the transfer operation can be continued.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of an electron beam transfer apparatus according to one embodiment of the present invention. First, the configuration and operation of the optical system will be described. The electron gun 1 arranged at the uppermost stream of the optical system emits an electron beam downward. Below the electron gun 1, three stages of condenser lenses 2, 3, and 4 are provided.
Through the blanking aperture 7 to form a crossover.

Below the condenser lens 3, a rectangular opening 5 is provided.
Is provided. This rectangular aperture (illumination beam shaping aperture) 5 is used for one sub-field (exposure 1) of the reticle.
Only the illumination beam that illuminates the unit area) is passed. Specifically, the opening 5 forms the illumination beam into a square having a dimension of slightly more than 1 mm square in reticle size conversion. The image of the opening 5 is formed on the reticle 9 by the condenser lens 8.

Below the opening 5, a blanking opening 7 is provided at a position where a crossover is formed. Below this, a condenser lens 8 is arranged. The condenser lens 8 converts the electron beam into a parallel beam and impinges it on the reticle 9 to form an image of the aperture 5 on the reticle 9.

Although the reticle 9 shows only one sub-field on the optical axis, it is actually in the vertical plane (X-
(Y plane). On the reticle 9, a pattern (chip pattern) forming one semiconductor device chip as a whole is formed. The reticle 9 is XY
It is mounted on a reticle stage that can move in the direction. The wafer 21 as a sensitive substrate is also mounted on a wafer stage that can move in the X and Y directions. By synchronously scanning the reticle stage and the wafer stage in the opposite Y directions, a large number of sub-fields arranged in the Y direction in the chip pattern are sequentially exposed. Both stages are equipped with an accurate position measurement system using a laser interferometer.
On 1, the reduced images of the pattern small areas on the reticle 9 are accurately joined.

Below the reticle 8, projection lenses 10 and 17 are provided. Then, an illumination beam is applied to a certain sub-field of the reticle 9, and the patterned electron beam passing through the reticle 9 is reduced by the projection lens and is imaged at a predetermined position on the wafer 21. An appropriate resist is applied on the wafer 21, and the resist is given a dose of an electron beam to transfer a reduced pattern of a reticle image onto the wafer 21.
The wafer 21 is mounted on a wafer stage movable in a direction perpendicular to the optical axis. Note that the crossover C. is a point at which the reticle 9 and the wafer 21 are internally divided at a reduction ratio.
O.20 is formed, and a contrast opening 11 is provided at the crossover position. The opening is a reticle 9
To block the non-pattern beam scattered by the above from reaching the wafer 21.

The excitation coils of the projection lenses 10 and 17 are controlled by a controller 31 via a coil power supply 32. Further, the reticle stage and the wafer stage are also controlled by the controller 31 via the stage drive motor control unit. As a result, each of the sub-fields on the reticle 9 is sequentially illuminated, and the image of the sub-field is projected onto an appropriate position on the wafer 21, so that the reduced images of the sub-fields are accurately joined to each other to form a chip. A reduced image of the entire pattern is transferred onto the wafer.

The second projection lens 17 has an exciting coil 17a housed in a magnetic pole 17b having a U-shaped cross section opened toward the optical axis. On the optical axis side of the exciting coil 17a, a ferrite stack 23 for magnetic shield (a stack of insulators and ferrite rings) is arranged. Inside the ferrite stack 23, a stigmator coil 14 and a deflector group 15 are further arranged. Astigmatism correction coil 14
Is a coil for correcting astigmatism of the optical system.
The deflector group cooperates with the astigmatism correction coil 14 to correct aberrations when a reticle in a portion away from the optical axis is exposed,
The linear distortion of the pattern image is corrected. The optical axis side surface of the astigmatism correction coil 14 and the deflector group 15 and the side surface of the wafer 21 are covered with a vacuum wall (not shown). The first projection lens 10
Similarly to the second projection lens 17, it has a ferrite stack, an astigmatism correction coil, and a group of deflectors, but is not shown.

Next, the structure for cooling each part and the arrangement of the temperature sensor will be described. The molding opening 5 is provided with a cooling jacket 5a. The cooling jacket 5 a has a refrigerant circulation passage therein and cools the forming opening 5. A thermocouple 6 is attached to the molding opening 5.
Is monitoring the temperature. The crossover opening 11 is also provided with a similar cooling jacket 11 a and a thermocouple 12.

A refrigerant passage 17c is formed in the magnetic pole 17b of the second projection lens, and the excitation coil 17a, the astigmatism correction coil 14,
The deflector group 15 and the like are cooled. Also, the exciting coil 17a
A thermocouple 18 and the astigmatism correction coil 14 a thermocouple 13
However, a thermocouple 16 is attached to the deflector group 15, and monitors the temperature of each part.

A temperature signal from each thermocouple is sent to a thermometer / signal generator 30. The thermometer / signal generator 30 constantly compares the temperature of each part with a predetermined value, and sends a signal to the controller 31 when the temperature rises more than a specified value. Each cooling jacket 5a, 11a and exciting coil cooling water passage 1
The refrigerant is circulated and supplied from the cooling device 33 to 7c.

Next, the operation of monitoring and controlling the temperature of the electron beam transfer apparatus of this embodiment will be described. First, the following temperature reference values are set for each part. 1st upper limit temperature 2nd upper limit temperature Molding opening 200 ° C 300 ° C Crossover opening 400 ° C 800 ° C Second exciting coil 80 ° C 150 ° Astigmatism correcting coil 80 ° C 150 ° Deflector group 80 ° C 150 ° C

The temperature of each part is constantly monitored, and if any temperature exceeds the first upper limit temperature, the amount of refrigerant supplied to that part is increased by, for example, 50 to 100%. This is performed by operating a valve (not shown) in the cooling device 33 or increasing the number of operation and rotation of the pump. Alternatively, a coolant having a particularly low temperature (e.g., 18 to 20 ° C., usually 23 ° C.) is sent to a portion exceeding the first upper limit temperature. At this time, each part of the optical system continues the normal operation, and the exposure operation continues.

If the temperature of any part exceeds the second upper limit temperature despite the increase in the cooling output, the exposure operation is temporarily stopped. At this time, the temperature and current of the electron gun are reduced. The exciting current of each lens is a low value of about 80% of the rating. The exciting current of each deflector is set to 0.

In this embodiment, the temperature of the main part is constantly monitored, and the computer recognizes the temperature value of each part. Therefore, an accident such as the fact that some temperature was abnormally rising without knowing and the transfer with poor accuracy did not occur, and stable transfer could be performed even at a high acceleration voltage of 100 kV, Even if a failure occurs, the cause can be immediately identified, so that it can be quickly recovered.

[0022]

As is apparent from the above description, according to the present invention, it is possible to provide an electron beam transfer apparatus capable of preventing a decrease in pattern transfer accuracy due to a rise in temperature of each part of the apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an overall configuration of an electron beam transfer device according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electron gun 2 Condenser lens 3 Condenser lens 4 Condenser lens 5 Molding opening 5a Cooling jacket 6 Thermocouple 7 Blanking opening 8 Condenser lens 9 Reticle 10 First projection lens 11 Crossover opening 11a Cooling jacket 12 Thermocouple 13 Thermocouple 14 Non Point correction coil 15 Deflector group 16 Thermocouple 17 Second projection lens 17a Excitation coil 17b Magnetic pole 17c Refrigerant passage 18 Thermocouple 20 Crossover 21 Wafer 23 Ferrite stack 30 Thermometer and signal generator 31 Controller 32 Coil power supply 33 Cooling device

Claims (3)

[Claims] An apparatus for irradiating a mask having a pattern to be transferred onto a sensitive substrate with an electron beam, and transferring the pattern by forming an electron beam patterned through the mask onto the sensitive substrate. A lens excitation coil, a deflection coil,
A temperature sensor disposed in the astigmatism correction coil, the shaping opening or the crossover opening; receiving a signal from the temperature sensor; determining whether to stop the transfer operation when the temperature of any of the above-mentioned portions exceeds a predetermined value. ,
Or a control unit for increasing the output of the cooling device of each unit of the apparatus. 2. The method according to claim 1, wherein the output of the cooling device is first increased when the temperature of any one of the portions exceeds a predetermined value, and the transfer operation is temporarily stopped when the temperature continues to rise thereafter. Item 7. An electron beam transfer device according to Item 1. 3. The electron beam transfer device according to claim 1, wherein the output of the cooling device is increased by increasing the flow rate of the refrigerant or decreasing the temperature of the refrigerant.