JPH05198490A - Charged-particle beam exposure system - Google Patents

Abstract

PURPOSE:To realize a charged-particle beam exposure system having high positioning accuracy by mounting a refrigerant flow path to a stage and connecting the refrigerant flow path to an external refrigerant source. CONSTITUTION:A sample 10 is placed onto an X-stage 3, and held movably in XY-planes by the X-stage 3 and a Y-stage 2. Refrigerant flow paths 11, 14 are formed into the Y-stage 2 and the X-stage 3, and connected mutually by a bellows 15 in an expansible and contractible manner in the X-direction. These refrigerant flow paths are connected to an external refrigerant source by a bellow 12. Accordingly, heat generated by friction can be removed quickly. The thermal expansion of the stages can be prevented, thus allowing charged- particle beam exposure having high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam exposure apparatus, and more particularly to a highly accurate and high throughput charged particle beam exposure apparatus.

In recent years, with the increase in density of semiconductor integrated circuit devices, it has been required to expose finer and more precise patterns. Charged particle beam exposure, such as electron beam exposure, has the potential to potentially meet these requirements. The positional accuracy of the exposure pattern is determined by the accuracy of the stage on which the sample is placed and the positional accuracy of the charged particle beam.

[0003]

2. Description of the Related Art In a conventional electron beam exposure apparatus,
Subfields are drawn by electrostatic deflection. The area that can be deflected by electrostatic deflection is usually at most several hundred μm □. A plurality of stages of electromagnetic deflection coils are provided to draw a wider area. That is, while the electron beam is deflected in a wide range by the electromagnetic deflection coil, a minute portion is deflected by electrostatic deflection.

However, even if the electromagnetic deflection coil is used, it is impossible to deflect-scan the entire surface of, for example, an 8-inch wafer. Therefore, a sample such as a semiconductor wafer is placed on a stage, and the stage is moved to draw a pattern in a wide range on the sample.

As a pattern drawing method, a step and repeat (SR) mode and a continuous move (CM) mode are mainly known. In the SR mode, the stage is moved intermittently, and electron beam exposure is performed while the stage is stopped. In the CM mode, the stage moves continuously, and stage movement and electron beam exposure are performed in parallel.

The SR must always move to the next field after the main field exposure, and must repeat the acceleration / movement / stop of the stage each time. The number of times varies depending on the size of the main field and the size of the sample, but when a 4-inch wafer is exposed in a main field of 2 mm □, the number of times of movement is about 1000 times.

Further, since it is necessary to calibrate the electron beam lens barrel during exposure, it is necessary to move the stage to the calibration position. Also, the stage itself must be moved in the calibration itself.

Since all stage movements are included in the exposure time as a whole, if the static waiting time until the stage is completely stopped is the same, the stage movement speed should be as high as possible to shorten the exposure time. preferable. Also, it is preferable that the acceleration is large.

In CM, the number of stage movements, that is, the number of acceleration stops is smaller than that in SR. Since the stage moves continuously and the stop acceleration for each main field can be omitted, the stop acceleration required for the exposure is only when making a U-turn at the edge of the sample, and the intermediate stop can be omitted.

However, it is necessary to calibrate the electron beam lens barrel even in the CM, and all stage movements including the U-turn are directly reflected in the exposure time. Therefore, it is preferable that the stage moving speed is as high as possible within the range where the electron beam exposure can follow the stage movement. Further, it is still preferable that the acceleration is large.

Electron beam exposure is generally performed using a point beam, a variable rectangular beam, a block pattern beam, or the like. In either case, it is necessary to position the stage and deflect and position the electron beam to expose the desired area on the wafer.

An electron beam exposure apparatus capable of block exposure will be described with reference to FIG. The exposure apparatus is roughly divided into an exposure unit 110 and a control unit 150. Exposure unit 1
Reference numeral 10 denotes a portion for generating an electron beam, shaping it into a spot shape or a pattern shape, and exposing it at a desired position on an exposure object. The control unit 150 is a unit that forms a signal for controlling the exposure unit 110. Below the exposure unit 110, there is a stage 135 on which the exposure target W is placed.

First, the exposure section 110 will be described. Electrons generated from the cathode electrode 111 are generated by the grid electrode 1
12 and the anode electrode 113. These electrodes 111, 112, 113 form a charged particle beam generation source 114.

The electron beam generated from the charged particle beam generation source 114 is shaped by, for example, a first slit 115 having a rectangular opening, passes through a first electron lens 116 that focuses the electron beam, and is transmitted onto the transmission mask 120. Is incident on the slit deflector 117 for correcting and deflecting the beam irradiation position of. The slit deflector 117 is controlled by the modified deflection signal S1.

In order to shape the electron beam into a desired pattern, a transmission mask (stencil mask) 120 having a plurality of transmission holes such as a rectangular opening and a block pattern opening of a predetermined pattern is used.

The electron beam that has passed through the slit deflector 117 has a second electron lens 11 provided opposite thereto.
8, a third electron lens 119, a transparent mask 120 mounted horizontally movable between these electron lenses, and arranged above and below the transparent mask 120, respectively, according to the position information P1 to P4. The beam is deflected and shaped into a desired pattern through an electron beam shaping unit including first to fourth deflectors 121 to 124 that select one of the transmission holes on the transmission mask 120.

The shaped electron beam is blocked or passed by the blanking electrode 125 to which the blanking signal SB is applied. The electron beam that has passed through the blanking electrode 125 is adjusted by the fourth electron lens 126, the aperture 127, the refocus coil 128, and the fifth electron lens 129, and the focus coil 130 is adjusted.
Incident on. The focus coil 130 has a function of focusing the electron beam on the exposure target surface. Also,
The stig coil 131 corrects astigmatism.

The electron beam further includes a sixth electron lens 1
32, its position is controlled by a main deflector 133, which is an electronic deflection coil that positions the object W to be exposed according to the exposure position determination signals S2 and S3, and a sub-deflector 134, which is an electrostatic deflector. The desired position on W is irradiated.

The exposure object W is placed and moved on the stage 135 which is movable in the XY directions. The exposure unit 110 is further provided with first to fourth alignment coils 136, 137, 138, 139.

The control unit 150 includes a memory 151 and a CPU 1.
52. The design data of the integrated circuit device is stored in the memory 1
It is stored in 51, read out by the CPU 152, and processed. The CPU 152 controls the whole other charged particle beam exposure apparatus.

The interface 153 is the CPU 152.
The drawing information taken in by, for example, the drawing position information on the wafer W where the pattern is to be drawn, various information such as mask information of the transparent mask 120, and the like are transferred. The data memory 154 stores and holds the drawing pattern information and mask information transferred from the interface 153.

The pattern controller 155 receives the drawing pattern information and the mask information from the data memory 154, designates one of the transmission holes of the transmission mask according to the information, and indicates the position of the designated transmission hole on the transmission mask. Designating means, holding means, computing means, and output means for generating various signals P1 to P4 and performing various processing including processing for computing a correction value H according to the shape difference between the pattern shape to be drawn and the designated transmission hole shape. Have.

An amplifier section 156 having a digital / analog converter function and an amplifier function receives the correction value H and generates a corrected deflection signal S1. The mask moving mechanism 157
According to the signal from the pattern controller 155, the transparent mask 120 is moved as necessary.

The blanking control circuit 158 controls the amplifier section 159 having a digital / analog converter function and an amplifier function in response to a signal from the pattern controller 155 to generate a blanking signal SB.

The sequence controller 160 receives the drawing position information from the interface 153 and controls the drawing processing sequence. The stage moving mechanism 161 moves the stage 135 as needed according to a signal from the sequence controller 160.

The movement of the stage 135 is detected by the laser interferometer 162 and supplied to the deflection control circuit 163. The deflection control circuit 163 calculates the exposure position on the wafer W and supplies the signals to the amplifier units 164 and 165 that generate the exposure position determination signals S2 and S3, and also supplies the signals to the sequence controller 160. The amplifier units 164 and 165 have a digital / analog converter function and an amplifier function, respectively.

In normal electron beam exposure, the main deflector 133, which is an electromagnetic deflector, is used for 2 to 10 m.
The m.quadrature.deflection field is beam-deflected, and a subdeflector 134 which is an electrostatic deflector deflects a subfield of about 100 .mu.m.quadrature.

The pattern data is read from the memory 151 by the CPU 152, transferred to the data memory 154, and stored therein. The pattern controller 155 decomposes the pattern for each shot based on the pattern data read from the data memory 154.

The pattern data decomposed into each shot is separated into data for the main deflector 133, data for the sub-deflector 134, data for the slit deflector 117, blanking signal SB, etc. to control the deflection of the electron beam.

Charged particle beam exposure such as electron beam exposure must be performed in vacuum. Therefore, the stage for holding and moving the sample to be exposed also needs to be arranged in vacuum. In order to realize high throughput, it is necessary to rapidly accelerate the stage existing in vacuum and move it at high speed.

On the other hand, the positioning accuracy of the stage is 0.0
About 5 μm is required, and positioning accuracy of about 0.01 μm will be required in the future. The laser measurement technology sufficiently satisfies this accuracy.

Therefore, it is considered that such positioning accuracy can be realized by monitoring the movement of the stage with a laser length measuring device and performing field back control of the stage drive mechanism.

FIG. 6 shows the structure of a conventional stage. The housing 170 that houses the stage has a base 171 on the lower surface, and the XY stage is arranged on the base 171. XY stage is Y stage 17
3 has a structure in which the X stage 175 is placed.
The Y stage 173 is configured to be movable in the Y direction by the tire 177, and is driven in the Y direction by the actuator 183.

The actuator 183 is the capstan 1
It is nipped by 85 and the pinch roller 184, and driven by the rotation of the capstan 185. A guide 181 in the X direction is provided on the upper surface of the Y stage 173, and a pinch roller 179 provided on the lower surface of the X stage 175 sandwiches the guide 181 in the X direction from both sides so that the X stage 175 is only in the X direction. You can move to.

The X stage 185 is held on the Y stage 173 by the tire 178. X stage 1
The driving of 75 is performed similarly to the driving of the Y stage 173. On the X stage 175, the wafer W is placed in a cassette.

Mirrors Mx and My optically coupled to the laser interferometer 190 are attached on two sides of the X stage 175, and the position of the X stage 175 is monitored. The laser length measuring device is capable of measuring lengths of about 1/50 to 1/100 wavelength.

FIG. 6 (A) shows a form in which the stage is held by a tire, but in the case of a heavy stage, a roller is used instead of the tire. FIG. 6B schematically shows the structure of the rollers. A cylindrical roller 194 is held in the opening of the retainer 192 to hold an object. In the case of a stage using rollers, rollers are used instead of the tires 177 and 178 of the stage shown in FIG.

[0038]

By the way, it has been confirmed that the beam may be displaced after a long period of stage running. It was confirmed that the origin of the beam changed when the stage was stopped just below the lens barrel for a long time and when it was stopped for a long time away from the lens barrel.

That is, even if the stage position is monitored with high accuracy and the field back control is performed, the required positioning accuracy cannot be obtained. An object of the present invention is to provide a charged particle beam exposure apparatus having high positioning accuracy.

Another object of the present invention is to provide a charged particle beam exposure apparatus having a high positioning accuracy even for continuous use for a long time.

[0041]

A charged particle beam exposure apparatus of the present invention places a sample on a stage, moves the sample by moving the stage, and irradiates the sample with a charged particle beam. A beam exposure apparatus,
The stage has a coolant channel, and the coolant channel is connected to an external coolant source.

[0042]

It has been found that the thermal expansion of the stage causes the positional deviation of the charged particle beam regardless of the irradiation of the charged particle beam after the stage has been running for a long time.

By running for a long time, frictional heat is generated in the movable member forming the stage, which causes thermal expansion of the stage. If the stage itself changes its dimensions, even if the mirror position of the laser interferometer attached to the end of the stage is accurately controlled,
The position on the stage changes.

It was found that the variation of the beam origin at the position directly below the lens barrel and at the position away from the lens barrel is affected by the heat radiation due to the heat generated by the coil in the lens barrel. In order to improve the resolution of the charged particle beam, the distance between the sample surface and the lower surface of the lens barrel is only about several mm, and the distance between the coil and other structures and the sample surface is short.

Further, as the focal length is shortened, the heat generation amount of the coil is increased. Therefore, the sample itself or the stage which receives the heat radiation from the coil or the like causes thermal expansion, and the beam is displaced.

In the charged particle beam exposure apparatus, since the stage is placed in a vacuum, the heat once accumulated on the stage is transferred by heat conduction through the contact surface of the tire, rollers or the like, or is transferred to the outside by heat radiation. There is no choice but to be done. Therefore, the heat once accumulated in the stage is difficult to be transferred to the outside.

For example, in a stage having a coefficient of thermal expansion of about 8 × 10 ^-6 (a typical value for ceramics), a temperature rise of about 0.1 ° C. will cause a 40 cm stage to reach about 0. Displacement occurs due to thermal expansion of 3 μm. Assuming that the sample is fixed at the center of the stage, the beam position shift is about 0.15 μm. This value is a fatal value in submicron pattern formation.

The stage can be forcibly cooled by forming the coolant channel in the stage and flowing the coolant from the external coolant source into the coolant channel. By controlling the temperature of the refrigerant, the temperature of the stage can be controlled, and the temperature rise of the stage can be prevented.

[0049]

The present invention was born in the process of developing a charged particle beam exposure apparatus with high accuracy and high throughput. Hereinafter, the present invention will be described according to the flow of development.

In order to avoid the Coulomb interaction of the charged particle beam, it is necessary to shorten the focal point of the charged particle beam optical system. When the optical system has a short focal length, the deflection efficiency deteriorates, and a larger current is required to obtain the same deflection distance.

In order to operate the electromagnetic deflection coil as fast as possible, it is necessary to reduce the inductance, and it is desirable to reduce the area of the coil. In such a structure, when the charged particle beam is operated using the electromagnetic deflection coil, it is inevitable that local heat is generated in the column. Such fever
For example, it is about several watts to tens of watts.

When such a charged particle beam exposure apparatus is used, a drift occurs in which the deflection position and the focus position of the charged particle beam fluctuate with the time of use. The following are possible causes for changing the deflection position and the focus position of the charged particle beam.

(A) Output change of amplifier and lens power supply,
(B) Eddy current flowing in metallic peripheral parts due to changes in magnetic flux generated by the coil, (c) charge-up of the portion where the beam passes, (d) variation in position and size of the deflection coil,
(E) The position and size of the coil itself, the bobbin, and other structures change due to temperature changes due to heat generation of the coil.

The present inventors initially suspected that the response characteristics of the deflection coil were extremely deteriorated. However, the output of the amplifier did not change and the settling time constant was the same. Further, the inductance of the deflection coil is almost the same. That is, although the deflection magnetic field is settled, there is a factor that changes the beam position. The eddy current when the same deflection is performed cannot be considered to change before and after exposure.

Further, when the beam is not deflected, the beam position on the optical axis has reproducibility for a long time. Therefore, charge-up cannot be considered. As a possibility of remaining, fluctuations in position and size due to temperature changes of the coil itself, bobbin, and other structures (pole pieces, etc.) due to heat generation of the coil remain. As described above, the electromagnetic deflection coil generates heat of several W to several tens of W, and when the electromagnetic deflection coil is placed in a vacuum, its heat radiation effect is low.

In a converging deflection system with a short focal length, the lens magnetic field strength must be increased and the deflection magnetic field strength must also be increased. Therefore, the lens magnetic pole becomes small, and the deflection coil placed inside the lens magnetic pole is in the optical axis direction. Also in the radial direction, they are arranged in a narrow space without any gap. Therefore, the parts holding the coil are light, thin, short and small, and the heat capacity is a fraction of that of the conventional one.

Further, the difference in the radius of the coil is small in the XY system. In addition, although the size of the coil has been reduced, the thickness of the wire is almost the same, the thickness of the coil in the stacking direction becomes large, and the wire around the inner coil is covered by the wire around the outer coil. I'm hiding it.

Even if the outer side of the coil is air-cooled, the effect of air-cooling is greatly different between the inner and outer coils, and the inner coil can hardly be directly cooled, and the bobbin is used for heat conduction. become. Therefore, the cooling effect differs between the inner coil and the outer coil.

When a coil is manufactured by using a thin wire rod to increase the effect of air cooling, heat generation of the coil becomes large. Therefore, the thermal expansion of the coil wire rod and the thermal expansion of the bobbin to which the coil is adhered further increase the beam width. Deflection accuracy deteriorates.

When copper is used for the coil wire and ceramic is used for the bobbin, the coefficient of thermal expansion of each is 1.7 × 1.
Since 0 ^-5 and 8 x 10 ^-6 , if the main deflection area is set to 2 mm □, when the temperature rise is 10 ° C, 0.34 each.
There is a possibility that a positional deviation of μm or 0.16 μm may occur in the main deflection region.

Since the coil and the bobbin are actually adhered to each other, it can be expected that the positional deviation amount takes a value between 0.34 μm and 0.16 μm. Even if this value is assumed to be 0.2 μm, the positional deviation of the main deflection region is 0.4 μm at maximum, which is a fatal error in submicron pattern formation.

A more serious problem is that the heat generated by the coil causes the thermal expansion of the coil wire itself and the thermal expansion of the bobbin to which the coil is adhered, and the thermal expansion of the pole piece such as ferrite forming the projection lens. Is also to be generated.

These thermal expansions change the coil deflection direction, deflection efficiency, and lens magnetic field strength. For this reason, the accuracy of the deflection position is deteriorated, and especially the thermal expansion of the magnetic pole causes the deviation of the origin of the deflection coordinates and the deviation of the focus.

Particularly in the exposure by the continuous movement of the stage, the alignment mark on the sample surface is detected in advance before the exposure, and the exposure is performed after the correction coefficient at the exposure is determined.
The deterioration of the accuracy of the exposure position, the deviation of the origin of the deflection coordinates, and the deviation of the focus during the exposure are fatal.

FIG. 7 shows the result of measuring the fluctuation component of the beam position when the main deflector is continuously heated. The upper part of FIG. 7 is a graph showing how the offset position deviation amount d1 changes with time. The middle part of FIG. 7 is a graph showing how the positional deviation d2 in the rotation direction changes with time. Further, the lower part of FIG. 7 is a graph showing how the positional deviation d3 in the gain direction changes with time.

When the main deflector continues to generate heat, these deviation amounts change to a considerably large value as shown by the broken line in the figure. As is clear from the figure, these shift amounts are fatally large for an exposure apparatus that exposes a submicron pattern.

Therefore, it can be considered to prevent drift by cooling the electromagnetic deflection coil forming the main deflector and suppressing heating. The present inventors actually created an electromagnetic deflection coil having a large cooling capacity and investigated its effect.

A double structure bobbin having an inner bobbin and an outer bobbin was adopted as the coil supporting bobbin. The coil was wound in one layer in the radial direction and was wound in an arc shape in the rotating direction to form a desired number of turns. This coil was bent along a cylindrical surface to form a saddle-shaped coil.

Saddle coils having different radii of curvature were formed, coils having a small radius of curvature were fixed on the outer circumference of the inner bobbin, and coils having a large radius of curvature were fixed on the inner circumference of the outer bobbin. A space was left between the inner coil and the outer coil, and a flow path was formed so that the coolant could flow in the optical axis direction.

The bobbin has a structure which is independent or integrated by a plurality of stages of coils, and is made of a material containing quartz as a main component and having a small linear expansion coefficient. Pure water or helium gas was used as the refrigerant, and forced reflux was performed.

In this way, the electromagnetic deflection coil of the main deflector was efficiently cooled, and the heat conduction to the structure such as the pole piece was reduced. It was expected that the temperature rise of the structure would be significantly reduced by effective heat dissipation.

The position variation of the electron beam when the electromagnetic deflection coil having such a configuration is used is shown by the solid line in FIG. Figure 7
In, the curve f1 shows the amount of offset position deviation when cooling is performed as a function of time, and the curve f2 similarly.
The positional deviation in the rotation direction during cooling is shown as a function of time, and the curve f3 shows the positional deviation in the gain direction during cooling as a function of time.

However, as is clear from the figure, the beam position fluctuation was reduced to about half of that without cooling, even though the electromagnetic deflection coil was cooled.

For example, the shift amount of the offset position is about 3 minutes after the start of exposure, and about 0.5 when the cooling is not performed.
What was μm was about 0.3 by cooling.
It was only reduced to μm. The amount of offset position offset gradually saturates over time, but the amount of offset at that time was about 0.4 μm, which was not an acceptable value.

Further, the positional deviation in the rotation direction was only reduced to about half even when the cooling was performed, compared with the case where the cooling was not performed. The decrease in misalignment in the gain direction was even smaller.

That is, although the cooling efficiency is improved with respect to the heat generation, the cooling is not completed completely, and it is clear that the temperature change of the structure is caused by the heat generation. Although it is possible to increase the cooling capacity of the refrigerant to such an extent that the amount of heat generated can be ignored, increasing the flow rate of the refrigerant may cause mechanical vibration or the like due to the increase in the flow rate.
Moreover, there is a limit to the increase in the flow rate of the refrigerant. It is conceivable to further reduce the heat conduction from the electromagnetic deflection coil to the pole piece or the like, but there is still a limit.

When the temperature rise of the pole piece due to the heat generation of the electromagnetic deflection coil was measured, it was found that the temperature was about 1.5 ° C. in 10 minutes before cooling, but 1
It decreased to about 0.3 ° C. in 0 minutes. The temperature rise is saturated in about 10 minutes, and the saturated value greatly changes depending on whether cooling is performed or not. That is, the cooling effect is sufficiently observed.

However, the accuracy of the exposure system is far from being sufficiently improved. In particular, since there is not much difference in the temperature change in the initial stage after the change of the drive current, the effect of cooling cannot be said to be remarkable when focusing on the drift of the beam position within the time of about 3 minutes.

In order to obtain the high accuracy required by the semiconductor integrated circuit, it is considered that the temperature change of the structure due to the heat generation of the main deflector is not allowable even 0.1 ° C. It is extremely difficult to achieve this by cooling as described above.

FIG. 8 shows a charged particle beam exposure apparatus created to solve the above problems. FIG. 8A is a cross-sectional view showing the structure, and FIG. 8B is a schematic graph for explaining the operation.

In FIG. 8A, the electromagnetic lens coil 2
11 is magnetically coupled to the iron yoke 212,
A pole piece 213, which is a pole piece made of iron or the like, is magnetically coupled to the tip of 2. Inside the electromagnetic lens, a coil support portion 214 such as a bobbin is arranged,
An electromagnetic deflection coil 216 is attached to the outside of the coil support portion 214.

Further, the electrostatic deflection electrodes 217 are arranged inside the coil support portion 214 so as to face each other. The numbers of the electromagnetic deflection coil 216 and the electrostatic deflection electrode 217 are shown in a simplified manner. The heating element 210 is arranged near the outside of the electromagnetic deflection coil 216.

The heating element 210 is composed of, for example, a resistance element, and generates Joule heat by passing an electric current.
As shown in FIG. 8B, the current flowing through the heating element 210 is the heat Q2 generated by the heating element 210 and the electromagnetic deflection coil 2.
It is controlled so that the sum of the heat Q1 generated by 16 becomes a constant value Q0.

That is, when the heat Q1 generated by the electromagnetic deflection coil 216 changes as indicated by the solid line due to the current flowing through the electromagnetic deflection coil 216, a current change that compensates for this change is supplied to the heating element 210, and the generation thereof is generated. By changing the heat Q2 to be applied in the opposite direction as indicated by the broken line, the heat Q0, which is the sum, is controlled to have a constant value.

By controlling in this way, the heat Q0 generated as a whole by the electromagnetic deflection coil and the heating element is always a constant value, and the temperature does not change after the system once reaches a stable state.

When the sample wafer 219 is not irradiated with the beam, as shown in the exposure start position in FIG. 8B, a certain amount of current is passed through the electromagnetic deflection coil 216, and the heat Q1 generated by the electromagnetic deflection coil 216 is generated. It is preferable that the total heat generation amount Q0 is set to about half and the heat generating element 210 generates substantially the same heat amount Q2.

As described above, even when the charged particle beam is not irradiated onto the sample wafer, the current value is set when the charged particle beam is irradiated onto the sample wafer by causing the idle current to flow through the electromagnetic deflection coil. Even if the change is made, the change width becomes about half or less of the conventional maximum value, and it becomes easy to quickly cope with the change.

Even when the maximum current is passed through the electromagnetic deflection coil 216, it is preferable to set a certain amount of current through the heating element 210 from the viewpoint of more stable temperature compensation.

Further, the electromagnetic deflection coil 216 and the heating element 21
Since 0 always generates a constant heat, the structure such as the pole piece shows a temperature rise. Since the heat of the heating element 210 is added, the value of the temperature rise becomes larger than that of the conventional one. When the temperature rise is saturated, the astigmatism, focus, distortion, and other optical system corrections are performed, and during exposure, these data are used to make corrections.

FIG. 9 is a block diagram showing a column configuration example of the charged particle beam exposure apparatus. Pattern generator 221
Generates pattern data, supplies its X-direction component to the digital-analog converter 222a and its Y-direction component to the digital-analog converter 222b, and also supplies deflection data to the analog operation circuit 224.

Digital / analog converters 222a, 22
2b supplies the deflection data converted into the analog amount to the electromagnetic deflection coil drive circuits 223a and 223b to generate a drive current for driving the electromagnetic deflection coil 226.

Digital-analog converters 222a, 22
The output signal of 2b is also supplied to the analog arithmetic circuit 224.
Be done. The analog arithmetic circuit 224 is a (1-bX²-CY
²) ^1/2A control signal corresponding to the heater driving circuit 2 for compensation
Supply to 25. The compensation heater drive circuit 225 has a constant value
Minus the amount of heat generated by the electromagnetic deflection coil 226
Generates a current equivalent to the amount of heat and supplies it to the heater 227 for compensation.
To pay.

The electromagnetic deflection coil 226 uses the electron beam EB.
A magnetic field is generated to deflect the light, and heat is generated by the flowing current. The compensating heater 227 changes the generated heat so as to compensate for the change in the heat generated by the electromagnetic deflection coil 226.

That is, the total amount of heat generated by the electromagnetic deflection coil 226 and the compensating heater 227 is always kept constant. Therefore, the electromagnetic deflection coil 226 and the compensating heater 2
The thermal effect of 27 on the surroundings does not change depending on the magnitude of the deflection and is kept at a constant value. The electron beam EB passes through the final aperture FA, is focused on the sample wafer W by the projection lens 228, and is deflected to a desired position by the electromagnetic deflection coil 226.

The analog operation circuit 224 performs an operation based on the pattern data so that the total amount of heat generated by the electromagnetic deflection coil 226 and the compensating heater 227 becomes constant.
The control signal is supplied to the compensating heater driving circuit 225. Note that a, b, and c are correction coefficients that are set so that the total amount of heat generated by the electromagnetic deflection coil 226 and the compensation heater 227 is constant.

As described above, by keeping the amount of heat generated in the vicinity of the electromagnetic deflection coil constant, it is possible to eliminate the temperature change due to the movement of the beam position and prevent the beam position drift.

In the conventional electron beam exposure apparatus, the electron beam position drift amount due to heat generation of the electromagnetic deflection coil was about 0.3 μm even when the electromagnetic deflection coil was cooled.
The configuration shown in FIG. 5 enabled the electron beam position drift amount to be about 0.05 μm.

FIG. 10 is a block diagram schematically showing another column configuration example of the charged particle beam exposure apparatus. In the figure,
The electromagnetic lens coil 211, the iron yoke 212, and the pole piece 213 have the same structure as that shown in FIG. Inside the electromagnetic lens, coil support portions 214a and 214b formed of a double-structured bobbin are arranged.

That is, a cylindrical space is defined by the inner bobbin 214b and the outer bobbin 214a, and the flow path 215 is formed between them. The electromagnetic deflection coil 216 has two
It is divided into two parts, one of which is fixed to the inner bobbin 214b and the other of which is fixed to the outer bobbin 214a. The flow path 215 passes through the middle thereof.

The pattern generating section 221 generates deflection data of the charged particle beam and outputs it to the digital / analog converter (D
AC) 222. The DAC 222 supplies the deflection data to the main deflection amplifier 223a, and the electromagnetic deflection coil 21
A current driving 6 is generated.

The DAC 222 also supplies a signal corresponding to the deflection data to the heat compensation circuit 233 and variably sets the current i supplied to the heating element 234. The heating element 234 is arranged in the refrigerant passage through which the cooling medium 231 flows. The coolant in contact with the heating element 234 is supplied to the coolant passage 215 in the electromagnetic lens via the coolant passage 232. This cooling medium is supplied at a constant speed, but the heat compensating circuit 233 causes the heating element 2 to
The current i supplied to 34 is controlled by the deflection data, and the cooling capacity changes accordingly. The current i is adjusted so that the sum of the heat generated by the electromagnetic deflection coil 216 and the heat given by the cooling medium near the electromagnetic lens becomes constant.

Therefore, as in the embodiment shown in FIG. 9, the total amount of heat generated in the vicinity of the electromagnetic lens is constant, and the temperature in the vicinity of the electromagnetic lens is kept constant regardless of the magnitude of deflection. FIG. 11 is a block diagram showing another column configuration of the charged particle beam exposure apparatus. Pattern generator 221, DAC2
22a, 222b, an electromagnetic deflection coil drive circuit 223a,
223b analog operation circuit 224, compensation heater drive circuit 225, electromagnetic deflection coil 226, compensation heater 22
7, projection lens 228, final aperture FA,
It is equivalent to that shown in FIG.

The output signal of the pattern generator 221 is also supplied to digital-to-analog converters (DAC) 222c and 222d, and these DACs 222c and 222d correspond to the analog operation circuits 224 in accordance with the deflection amounts X and Y of the charged particle beam. Signal is supplied.

Thus, the electromagnetic deflection coil drive circuit 22
3 is independent of the signal supplied to the analog operation circuit 224, the compensation heater 22
It is possible to prevent the influence on the data for deflecting the charged particle beam by changing the amount of heat generated in 7.

Further, it becomes easy to adjust the current supplied to the compensating heater separately from the signal supplied to the electromagnetic deflection coil. In the above configuration, one heating element is arranged near the electromagnetic deflection coil. However, the heating element and the electromagnetic deflection coil are at different positions, and there is a difference in the time for which the heat generated by each is transferred to the pole piece of the electromagnetic lens, for example. When trying to compensate the change in heat generated by the electromagnetic deflection coil by the change in heat generated by the heating element,
The use of a single heating element causes fluctuations due to the difference in heat transfer time in the transient state and limits compensation.

For example, when the value of the current flowing through the electromagnetic deflection coil is changed significantly, it is difficult to completely compensate for the change due to the heat generation of the electromagnetic deflection coil even if the heat generated by the compensating heater is to be compensated.

FIG. 12A schematically shows the limit of compensation by such a single heating element. In the figure, the horizontal axis represents time in seconds, and the vertical axis represents changes in the deflection field (changes in the position where the electron beam is actually deflected by the same deflection data), for example, the drift amount at the center of the field.

The total change obtained by adding the changes due to the heat generation of the electromagnetic deflection coil and the heat generation of the compensating heating element is shown by p0. At time t = 0, it is assumed that the value of the current flowing through the electromagnetic deflection coil from 0 to a predetermined value is significantly increased. At this time, it is assumed that the current flowing through the compensating heating element is significantly reduced.

It should be noted that a change in the deflection field when only the electromagnetic deflection coil is heated without supplying current to the compensating heating element is shown by p1, and no current is supplied to the electromagnetic deflection coil.
A change in the deflection field when only the compensating current flowing through the compensating heating element is reduced is shown by a broken line p2.

The values of the deflection current flowing through the electromagnetic deflection coil and the compensation current flowing through the compensating heating element are selected so as not to cause a change in the deflection field after a sufficient time has elapsed. In this way, even if set, the deflection field will change in the transient state. This is the curve p1
This is because the transient states of and p2 show different changes. Although the drawing shows the case where a downward convex change occurs in the deflection field, the convex change appears upward depending on the arrangement of the compensating heating element.

As described above, by providing the compensating heating element and compensating the change in the calorific value of the electromagnetic deflection coil with the change in the calorific value of the compensating heating element, the change in the deflection field can be remarkably reduced. It is extremely difficult to completely prevent the change of the deflection field even in the transient state.
Hereinafter, a configuration example in which the change of the deflection field in the transient state can be sufficiently prevented will be described.

FIG. 13 shows another column structure of the charged particle beam exposure apparatus. Electromagnetic lens coil 211, iron yoke 2
12, the pole piece 213, the coil support portion 214, the electromagnetic deflection coil 216, and the electrostatic deflection electrode 217 are the same as those in the embodiment shown in FIG.

In this configuration example, three heating elements 227 are used.
a, 227b, and 227c are provided near the electromagnetic deflection coil 216 and above and below the effective center of the electromagnetic deflection coil 216. Further, compensation heater driving circuits 241 and 2 capable of independently supplying currents to the heating elements 227a, 227b, and 227c.
A control circuit 239 including 42 and 243 is provided.

The deflection data Dx and Dy of the electromagnetic deflection coil are supplied to an electromagnetic deflection coil drive circuit (not shown) and are also supplied to a heat generation amount calculation circuit 237 of the electromagnetic deflection coil to generate heat amount W of the electromagnetic deflection coil. Is calculated.

The compensation calorific value calculation circuit 238 subtracts the calorific value W of the electromagnetic deflection coil from the constant calorific value W ₀ to be generated,
Determine the amount of heat that the compensating heating element should generate. This amount of heat is supplied to the control circuit 239, and the control circuit 239 determines the amount of heat that each of the three heating elements 227a, 227b, 227c should generate. The drive circuits 241, 242, 243 supply the currents based on these calculations, and the heating elements 227 a, 2
27b and 227c are caused to generate heat.

The heating elements 227a, 227b, 227c are arranged in the vicinity of the electromagnetic deflection coil 216, but their positions are different, and the transfer characteristics for transferring heat to the pole piece of the electromagnetic lens, for example, are different. A heating element 227 is provided above and below the effective center of the electromagnetic deflection coil 216.
Since a, 227b, and 227c are provided, each transfer characteristic is distributed above and below the transfer characteristic of the electromagnetic deflection coil.

Therefore, by adjusting the amount of heat generated by these three heating elements, for example, the effective heat transfer time is set at the same time as the electromagnetic deflection coil, and the thermal influence on the peripheral equipment such as the pole piece is adjusted. As shown in (B), it is possible to keep the effect of the total at a constant value even in a transient state. Note that in FIG. 12B, the influence of the heating elements 227a, 227b, and 227c on the change of the deflection field independently exerted by p2 and p.
3, p4.

As described above, the plurality of heating elements are arranged at different positions on the optical axis with the center of the electromagnetic deflection coil interposed therebetween, and the characteristics thereof are made different to further reduce the change of the deflection field in the transient state. Is possible.

FIG. 14 shows another column structure of the charged particle beam exposure apparatus. Similar to the configuration example shown in FIG. 10, a cooling medium is used and a plurality of heating elements are further provided in the flow path inside the electromagnetic lens. Electromagnetic deflection coil 216 (X), 2
16 (Y) is arranged in the flow path 215 formed by the coil supports 214a and 214b, and further, the flow path 215.
Inside, two heating elements 234a and 234b are arranged near the electromagnetic deflection coil and above and below in the optical axis direction.

The pattern generator 221 supplies the deflection data of the charged particle beam to the DAC 222, and the DAC 222 supplies a drive current to the electromagnetic deflection coil 216 via the main deflection amplifier 223a.

The DAC 222 also includes a thermal compensation circuit 233a.
The deflection data is supplied to the heat compensation circuit 233a, and the heat compensation circuit 233a generates the currents i ₁ and i ₂ to be supplied to the two heating elements 234a and 234b based on the deflection data.

The heating elements 234a and 234b are arranged at different places in the flow path 215 having different heat transfer characteristics with respect to the pole pieces, and have different thermal effects on the pole pieces 213 and the like. These two heating elements 234a, 234b
By adjusting the amount of heat generated by, the change in the deflection field in the transient state can be reduced as in the configuration example shown in FIG.

FIG. 15 shows a structural example of a control circuit capable of independently controlling the currents supplied to a plurality of heating elements. In the figure, four heating elements 227a, 227 are shown.
b, 227c and 227d are provided, and currents are supplied from four current sources 241a, 241b, 241c and 41d, respectively.

The current source 241 is a voltage / current conversion circuit for converting the current value generated by the input voltage, and the variable resistors VR1, VR2, VR are provided on the input sides thereof, respectively.
3 and VR4 are connected. Variable resistors VR1 and VR
Is 2, VR3, VR4 are connected in series, one end of which is grounded, it is given a signal which is proportional to (W ₀ -W) at the other end.

That is, (W ₀ -W) is a signal proportional to the amount of heat that the four heating elements should generate as a whole, and the four heating elements 227a to 227d are adjusted by adjusting the variable resistors VR1 to VR4. The ratio of the amount of heat to be generated can be variably adjusted.

In the configurations as shown in FIGS. 13 to 15, the amount of heat to be generated by a plurality of heating elements may be theoretically derived from the configuration, but more preferably it should be determined experimentally. ..

For example, a current is independently supplied to each of the plurality of heating elements, the resulting change in the deflection field is measured, the change in the deflection field is measured based on various deflection data, and the deflection based on the deflection data is measured. The ratio of the calorific value of the heating element to be compensated for the field change is obtained, and the current is actually applied to the electromagnetic deflection coil and the heating element to obtain the change, and finally the current value to be supplied to the heating element is determined.

It is preferable that the heating element is a resistance element that does not generate a magnetic field by passing an electric current, for example, a non-inductive coil in which a twisted pair wire is wound in a coil shape. In this case, the heat distribution of the electromagnetic deflection coil and the heat distribution of the heating element can be made extremely close to each other.

Further, when the heat is compensated, the temperature of the entire system rises. Therefore, each component is adjusted so that astigmatism correction, focus correction, distortion correction and the like of the optical system can be carried out in a heated state. Preferably.

Even if the heating element generates a slight magnetic field,
The current flowing through the heating element is synchronized with the current setting of the main deflector, and thermal compensation is performed during measurement of various correction maps. Therefore, the beam position and defocus due to the magnetic field generated by the heating element are corrected in the correction map. Will be taken into account.

With respect to the time delay of the temperature change due to heat conduction, the heating elements are arranged at least at two positions above and below the center position of the length of the main deflector in the optical axis direction, and the heating value of each heating element is increased. The effect of heat generation of the heating element and the coil of the main deflector on the structure such as the pole piece can be made equal by adjusting the above, and the effect of heat conduction can also be made equal.

Therefore, the temperature inside and outside the lens barrel is always kept constant during exposure and adjustment, so that the pole piece and other structures do not change their positions and dimensions due to thermal expansion. Therefore, the beam position and the focus position are always determined stably, and the pattern can be drawn with high accuracy.

By the way, it has been found that when the electron beam exposure apparatus in which the electron beam is stabilized as described above is actually used for exposure, the position of the electron beam is uncertain. For example, if the stage was simply run for a long time, the electron beam after that was displaced.

Upon investigating the cause of this, it was found to be the thermal expansion of the stage. The stage is rollers or tires,
It includes movable members such as rails, guide rails, capstans, and actuators, and friction is generated in association with these movable members. In the areas where these frictions occur,
Some frictional heat is generated, causing thermal expansion.

For example, it is extremely difficult to control slip called generally microslip, but such microslip also generates frictional heat.
Further, if the stage is driven without the position being monitored by the laser interferometer, the position is always changed. This fact means the existence of friction, and the existence of friction means the generation of frictional heat. Since the stage is placed in a vacuum, the heat dissipation performance is poor. Therefore, when frictional heat is generated on the stage, the temperature of the stage rises.

FIG. 1 shows a stage portion of an electron beam exposure apparatus according to the embodiment of the present invention. FIG. 1A shows the front surface, and FIG. 1B shows the side surface. On the base 1 which constitutes the lower surface of the housing 5 for storing the stage in a vacuum, Y
The stage 2 is supported via the tire 4. The Y stage 2 is arranged so as to be movable only in one direction by a guide roller that comes into contact with the guide 7.
8 and the actuator 17 driven by the capstan 19.

The X stage 3 is supported on the Y stage 2 via tires 4. A guide 8 is arranged on the surface of the Y stage 2 along the X direction, and the X stage 3 is held movably in the X direction by a guide roller 9 attached to the lower surface of the X stage 3. X
The stage 3 is driven in the X direction by a drive mechanism (not shown).

The sample 10 is placed on the X stage 3, and is held by the X stage 3 and the Y stage 2 so as to be movable in the XY plane. The position of the stage is
A mirror Mx for a laser interferometer provided on the X stage 3,
Monitored by My. FIG. 1A shows a mirror My for monitoring the position in the Y direction, and FIG. 1B shows X.
3 shows a mirror Mx for monitoring directional position.

A short focus projection lens 21 is arranged above the stage, and a main deflector 22 composed of an electromagnetic deflection coil and a sub deflector 23 composed of a counter electrode are arranged inside the projection lens 21. Has been done. The main deflector 22 supplies a current according to the pattern position in order to deflect the electron beam. The main deflector 22 generates heat due to the current flowing through the main deflector. When the temperature of the main deflector 22 rises,
Heat radiation corresponding to the temperature is generated, and the surface of the sample 10 looking at the main deflector 22 receives the heat radiation. The sample 10 and the stage are also heated by this heat radiation.

Refrigerant flow paths 11 and 14 are formed inside the Y stage 2 and the X stage 3 and are connected to each other by bellows 15 which can expand and contract in the X direction. Also,
These refrigerant channels are connected to an external refrigerant source by a bellows 12. In the configuration shown, the Y stage 2
The refrigerant passage 11 in the bellows 12 is expandable and contractible in the Y direction.
Connected by.

The heating source of the stage supported on the base 1 is the radiant heat from the friction portion and the lens barrel in the stage itself. The coolant channels 11 and 14 are arranged so as to efficiently remove the heat from these heating sources.

FIG. 2 shows an example of the arrangement of the coolant channels in the Y stage. The Y stage 2 is movable in the Y direction along the guide 7. Four tires 4 are provided on the lower surface thereof. The main heating source for the Y stage 2 is the frictional portion of these four tires 4. The refrigerant flow passage 11 is arranged through the upper portions of these four tires 4, and the tire 4
When heat is generated by the frictional portion of, the heat is quickly removed.

The refrigerant passage 11 is once connected to the X stage via the bellows 15a at its intermediate point, and the bellows 15b returning from the X stage is connected to the remaining refrigerant passages.

FIG. 3 shows another structural example of the Y stage.
This configuration is for a stage on which a heavy object can be placed, and rollers 30 are used instead of tires. A guide roller 31 for guiding is also used on the side surface of the guide 8. The coolant flow passage 11 has coolant flow passages 11a, 11a at the bottom of the roller 30 so as to efficiently cool these friction portions.
b, 11c and 11d are arranged.

Further, since friction heat is also generated by the guide rollers 31 arranged on both side surfaces of the guide 8, the refrigerant flow passages 11e, 1 are also formed on the surfaces in contact with these guide rollers 31.
1f, 11g, and 11h are arranged.

By arranging the refrigerant passages in all the places where frictional heat can be generated in this manner, even if heat is generated by friction, it is possible to quickly remove the heat.
The X stage 3 arranged on the Y stage 2 is
Since the radiant heat from the upper part is also received, it is preferable to arrange the refrigerant flow path so that these radiant heat can be efficiently removed.

FIG. 4 shows an example of the structure of a coaxial bellows which can simplify the arrangement of the bellows. Coaxial bellows 4
0 has a configuration in which the inner bellows 41 and the outer bellows 42 are arranged coaxially. By using such a coaxial bellows, it becomes possible to supply and recover the refrigerant with one bellows. For example, outer bellows 4
2 is used to supply the refrigerant, and the inner bellows 41 is used to recover the heat-generated refrigerant.

In the structure shown in the figure, the flexible bellows, which expands and contracts with the movement of the stage in the X and Y directions, only needs to expand and contract in a fixed direction, keeps its durability for a long time, and makes the temperatures of the upper and lower stages equal. Can be managed.

Although it is difficult to predict the generation of frictional heat, the amount of heat generated is not as large as that of the electromagnetic deflection coil. Therefore, satisfactory heat dissipation is performed by forcibly refluxing the refrigerant having a constant temperature.

The temperature of the refrigerant can be adjusted according to the speed of the stage and the like. As explained above,
In the column configuration of the lens barrel, by placing a heating element near the electromagnetic deflection coil to keep the amount of heat generated as a whole constant, and to supply a refrigerant to the stage to prevent heating due to friction and heat radiation. High-precision charged particle beam exposure can be performed.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various modifications, improvements, combinations and the like can be made.

[0152]

As described above, according to the present invention,
By arranging the refrigerant flow path near the frictional portion of the movable member of the stage and flowing the refrigerant, the heat generated by friction can be quickly removed.

Also, for heat radiation from the lens barrel,
By arranging the coolant channel in the stage, the temperature change of the stage can be efficiently prevented. By preventing the temperature change of the stage, thermal expansion of the stage is prevented and highly accurate charged particle beam exposure becomes possible.

[Brief description of drawings]

FIG. 1 is a front view and a side view schematically showing an electron beam exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a view of Y of the electron beam exposure apparatus according to the embodiment of the present invention.
It is a top view showing an example of arrangement of a refrigerant channel in a stage.

FIG. 3 is a diagram of Y of the electron beam exposure apparatus according to the embodiment of the present invention.
It is a perspective view which shows the other structural example of a stage.

FIG. 4 is a cross-sectional view schematically showing a configuration of a coaxial bellows used in an embodiment of the present invention.

FIG. 5 is a block diagram schematically showing a configuration of an EB exposure apparatus according to a conventional technique.

FIG. 6 is a schematic side view and a plan view of a roller for explaining a stage portion of an EB exposure apparatus according to a conventional technique.

FIG. 7 is a graph showing changes in beam position when cooling is performed and when the main deflector is continuously heated.

FIG. 8 is a sectional view and an operation waveform diagram showing a charged particle beam exposure apparatus.

FIG. 9 is a block diagram of a charged particle beam exposure apparatus.

FIG. 10 is a block diagram of a charged particle beam exposure apparatus.

FIG. 11 is a block diagram of a charged particle beam exposure apparatus.

FIG. 12 is a graph for explaining a transient state.

FIG. 13 is a block diagram of a charged particle beam exposure apparatus.

FIG. 14 is a block diagram of a charged particle beam exposure apparatus.

FIG. 15 is a circuit diagram showing a configuration example of a control circuit in the charged particle beam exposure apparatus.

[Explanation of symbols]

 1 Base 2 Y stage 3 X stage 4 Tire 5 Housing 7, 8 Guide 9 Guide roller 10 Sample 11, 14 Refrigerant flow path 12, 15 Bellows 17 Actuator 18 Pinch roller 19 Capstan 21 Projection lens 22 Main deflector 23 Sub deflector Q Heat 210 heating element 211 electromagnetic lens coil 212 iron yoke 213 pole piece 214 coil support 216 electromagnetic deflection coil 217 electrostatic deflection electrode 219 sample wafer 222 digital / analog converter 223 electromagnetic deflection coil drive circuit 224 analog operation circuit 225 compensation heater drive Circuit 226 Electromagnetic deflection coil 227 Compensating heater 228 Projection lens FA Final aperture EB Electron beam 234 Heating element 231 Cooling medium

Claims (5)

[Claims] 1. A charged particle beam exposure apparatus for placing a sample (10) on a stage (2, 3), moving the sample by moving the stage, and irradiating the sample with a charged particle beam. A charged particle beam exposure apparatus in which the stage (2, 3) has a coolant channel (11, 14), and the coolant channel is connected to an external coolant source. 2. A bellows (12) in which the connection between the refrigerant flow path (11) of the stage and an external refrigerant source is unidirectionally expandable and contractible.
2. The charged particle beam exposure apparatus according to claim 1, wherein the charged particle beam exposure apparatus is used. 3. The stage includes a lower stage (2) which moves in one direction and an upper stage (3) which moves in the other direction on the lower stage, and the upper stage (3) and the lower stage ( 2) are the refrigerant flow paths (1
4, 11), wherein the refrigerant flow passage (14) of the upper stage and the refrigerant flow passage (11) of the lower stage are connected by a bellows (15) which is expandable and contractible in the moving direction of the upper stage. 3. The charged particle beam exposure apparatus according to any one of 1 to 3 4. The charged particle beam exposure apparatus according to claim 1, wherein the bellows has a coaxial structure. 5. The charged particle beam exposure apparatus according to claim 1, wherein the stage is mainly made of alumina ceramics.