JP2000058415A - Charged particle beam exposure system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce displacement when the coordinate axis of deflection coordinates of an electron beam exposure apparatus of a bidirectional continuous movement exposure method does not coincide with the movement direction of a stage. SOLUTION: A charged particle beam deflector having a main deflector 16 and a sub deflector 14, and a moving mechanism 17 for moving a sample 18, the pattern exposure range is divided into a plurality of sub-regions 32a, 32b, After setting the main deflection amount, the sub-deflector changes the deflection position of the charged particle beam to pattern exposure of each sub-region, and the pattern exposure is performed by correcting the displacement while moving the sample. And the main deflector
In the main deflection area by 16, the drawable ranges 33a and 33b are set to limit the range of the movement direction of the sample used for pattern exposure, and the pattern exposure is performed even during the movement in the reverse direction, and the drawable range is set. Are independently set according to the moving direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charged particle beam exposure apparatus, and more particularly to a charged particle beam exposure apparatus that forms a pattern with a charged particle beam while continuously moving a stage. Semiconductor integrated circuits tend to be more highly integrated with advances in microfabrication technology, and the performance required for microfabrication technology is becoming increasingly severe. In particular, in the case of the exposure technology, the limit of the light exposure technology used for the steppers and the like conventionally used is expected. Charged particle beam exposure technology such as electron beam exposure technology is a technology that is likely to be the next generation of fine processing in place of light exposure technology. Hereinafter, an electron beam exposure apparatus will be described as an example.

[0002]

2. Description of the Related Art The problem of the electron beam exposure technique that has been pointed out so far is that the processing speed is slow and the manufacturing efficiency is poor. For this reason, various techniques for improving the throughput have been developed, and a continuous moving exposure (stage scan) method for performing continuous exposure while moving a stage is one example of such a technique.

In a conventional electron beam exposure apparatus, like a stepper, a sample (wafer) is placed on a stage, and after exposure of a pattern in a predetermined area is completed, the stage is moved to form a pattern in the next area. The step-and-repeat method of exposing the entire pattern on the sample by repeating the operation of exposing has been used. For example, 15 on one wafer
When exposing 60 mm-square chips, the deflectable area of the electron beam is about 1.5 mm. Therefore, it is necessary to move the stage 100 times for one chip, and 6000 times for one wafer. Will be needed.
Exposure cannot be performed while the stage is being moved or until the irradiation position of the electron beam that is changed according to the movement of the stage is accurately set. Such a time is referred to as a stage settling time here. The movement of the stage is a mechanical movement, and requires a certain amount of time for precise movement. Therefore, the stage settling time is considerably long, and is currently about 0.5 seconds. Therefore, the time required for 6000 stage movements was as long as 50 minutes, and it was difficult to improve the processing speed.

The continuous moving exposure method is a technique for dividing the exposure area into a plurality of strip-shaped areas and performing exposure while moving the stage continuously, thereby eliminating the stage settling time and improving the processing speed. . Assuming that the deflectable area of the electron beam is about 1.5 mm, an area of 1.5 mm × several dozen cm is drawn at a stroke without the stage settling time, so the stage settling time is reduced to about 1/100, and the processing speed is reduced. Is greatly improved. Therefore, in the method of drawing a pattern by scanning an electron beam, the continuous movement exposure method is an indispensable technique.

Conventional electron beam exposure apparatuses include a main deflector having a large deflection area but a low response speed, and a sub deflector having a small deflection area but a high response speed as compared with the main deflector. In the case of exposure, the exposure area is divided into a plurality of subfields, and the amount of deflection is fixed so that the deflection position by the main deflector is near the center of one subfield, and then exposure data is applied to the subdeflector. Draw the pattern in that subfield. By doing so, the number of changes (japs) in the deflection distance of the main deflector whose setting is slow is reduced, and high-speed exposure can be performed. It is conceivable that the sub-deflector corrects the displacement due to the movement of the stage in the continuous movement exposure method. In that case, the amount of movement of the stage is added to the exposure data and then applied to the sub deflector. In addition, there may be a case in which a deflection unit for correcting a displacement due to the movement of the stage is provided separately to facilitate control. In this specification,
The description will be made by taking as an example a configuration in which a deflection unit called a feedback coil for correcting a shift due to the movement of the stage is separately provided. However, the present invention is not limited to this, and can also be applied to a configuration in which a displacement due to the movement of the stage is corrected by means other than the sub deflector.

FIG. 1 is a diagram showing a configuration of an electron beam exposure apparatus that performs exposure by a continuous moving exposure method. In FIG. 1, reference numeral 1 denotes a processor, 2 denotes a magnetic disk,
Numeral 3 denotes a magnetic tape device, which is connected to each other via a bus 4 and to a data memory 6 and a stage control circuit 7 via a bus 4 and an interface circuit 5, respectively.

On the other hand, reference numeral 8 denotes a housing, in which an electron gun 9, a lens 10, a blanking electrode 11, a lens 12, a feedback coil 13, a sub deflector coil 14, a lens 15, a main deflector coil 16, a stage 1 are provided.
7 and a sample 18 are arranged. The sample 18 is placed on a stage 17, and the movement of the stage 17 is controlled in the X and Y directions by an output signal of the stage control circuit 7.

The data read from the data memory 6 is supplied to a pattern correction circuit 20 through a pattern generation circuit 19. The pattern correction circuit 20 applies a blanking signal to the blanking electrode 11 via the amplifier 21, and outputs a blanking signal to each DA converter (DAC) 2.
Signals are applied to the coils 13, 14 and 16 via 2, 24 and 26 and amplifiers 23, 25 and 27.

The electron beam emitted by the electron gun 9 is
After passing through the lens 10 and being transmitted or cut off by the blanking electrode 1 and further shaped into, for example, a rectangular beam of any parallel shot size of 3 μm or less, a feedback coil 13, a sub-deflector coil 14, and a main deflector coil While being deflected by 16, it is further converged on the sample surface through the projection lens 15. The deflectable areas of the feedback coil 13, the sub-deflector coil 14, and the main deflector coil 16 increase in this order. That is, the feedback coil 1
The deflectable area 3 is smaller than that of the sub deflector coil 14, and the deflectable area of the sub deflector coil 14 is smaller than the main deflector coil 16. In order to obtain a large deflectable area, it is necessary to increase the number of turns of the coil accordingly, and the response speed of each coil decreases in the reverse order to the above. That is, the feedback coil 13
Is the shortest, and the sub-deflector coil 14 and the main deflector coil 16 become longer in this order.

FIG. 2 is a diagram for explaining changes in the drawing area in the continuous movement exposure method. The exposure data describes data for one to several chips and is divided into an integer × an integer number of frames 30. The width of the frame 30 is set slightly smaller than the width of the deflectable area 31 of the electron beam. Each frame 30 is further divided into sub-frames 32, and the sub-frame 32 is set slightly smaller than the deflectable area of the sub-deflector. In FIG. 2A, reference numeral 30 denotes a frame, 31 denotes an electron beam deflectable area, and subframes 32 of A to L are shown. In each frame data, the deflection position of the main deflector of all patterns existing within the range,
The exposure data (the deflection position of the sub-deflector) and the feedback deflection position can be known. The stage is moved so that the exposure target position (the center position of the sub-frame to be exposed) enters the deflectable area, and at the same time, exposure starts.

The subframe in (1) of FIG.
When exposing in the order of B,..., L, the sub-frames A, B,..., L are exposed at the deflection positions shown in FIG. Actually, it is gradually shifted even in each subframe, but here, it is shown as shifted for each subframe for the sake of explanation. When exposing each sub-frame, the deflection position of the main deflector is set near the center of the sub-frame, and the exposure data of the sub-frame is applied to the sub-deflector. At the same time, the shift of the exposure position due to the movement of the stage is applied to the feedback coil 13.

As described above, the feedback coil 13
The deflection range is as small as several μm, and when there are many patterns in the subframe or when the stage speed is high, the deflection by the feedback coil reaches the limit before drawing the subframe is completed, that is, exceeds the deflection range of the feedback coil. Sometimes. This is called feedback overflow. When a feedback overflow occurs, the deflection position of the main deflector is reset based on the stage position at that time, the deflection amount of the feedback coil is reset, and the pattern is subsequently exposed. Such a process is called main deflector resetting. If the feedback overflow occurs many times, the deflection position of the main deflector gradually moves in the deflectable range in the direction of movement of the stage.

FIG. 3 is a diagram for explaining the operation of the feedback coil and the resetting of the main deflector accompanying the movement.
When the deflection amount of the feedback coil changes with the movement of the stage and reaches one limit of the deflectable range, the deflection amount of the feedback coil is changed to the other limit of the deflectable range, and at the same time, the deflection amount of the feedback coil is changed. The amount of deflection of the main deflector is changed by the amount of change. Therefore, the deflection amount obtained by adding the deflection amount of the feedback coil and the deflection amount of the main deflector at this time does not change. Accordingly, as shown in the figure, the total amount of deflection constantly changes in accordance with the movement of the stage. In addition,
Here, the stage moves at a constant speed,
Actually, it changes according to the complexity of the pattern to be drawn, so that the change in the amount of deflection of the feedback coil is not constant. Furthermore, when the drawing pattern is dense, the deflection position of the main deflector may move out of the deflectable range as it is. This is the main deflector overflow. In this case, an exposure failure occurs and the error is processed as an error. Actually, exposure is performed by setting the speed of the stage so that such exposure failure does not occur.

FIG. 3 shows an example in which the deflection amount changes instantaneously when the voltage applied to the main deflector and the feedback coil is changed. However, when the voltage of the main deflector or the feedback coil is changed, it takes time until the desired deflection amount is actually obtained. This is the aforementioned settling time. The resetting operation of the main deflector in consideration of the control unit of the main deflector and the feedback coil and the settling time will be described.

FIG. 4 is a block diagram showing a configuration of a control circuit for a main deflector and a feedback coil for realizing a conventional exposure sequence. Reference numeral 40 denotes a stage for detecting the moving speed of the stage. The stage counter 41 counts the pulses output by the interferometer and detects the moving amount of the stage. Latch 42 to latch
Having. The first difference calculation circuit 43 calculates the difference between the output of the stage counter 41 and the output of the latch 42, and the output is output as the amount of deflection of the feedback coil. In this block diagram, when the difference is zero, the deflection amount of the feedback coil is an initial value. However, if an offset is added in a subsequent stage, the feedback coil can be used in a free range. Further, from the difference between the output of the latch 42 and the field target position calculated by the second difference calculation circuit 44, the relative distance of the field target position excluding the amount of deflection by the feedback coil is obtained. This is corrected by the correction operation circuit 46, and the difference between the main deflector data value and the output of the correction operation circuit 46 is calculated by the third difference operation circuit 4.
By calculating in step 7, the actual output value of the main deflector can be calculated, and this is output to the main deflector. In such a control circuit, when the deflection amount of the feedback coil reaches the limit, a pulse is continuously input to the latch 42, and when the main deflector settling wait time ends, the input of the pulse is stopped and exposure is started.

FIG. 5 is a diagram showing a sequence when the main deflector is reset by the control circuit as described above. The main deflector is not only reset when the amount of deflection of the feedback coil reaches its limit, but also when the sub-deflector finishes drawing the sub-frame, the deflection position is set to the center of the next sub-frame. Is done. FIG. 5 shows both resetting and setting of the main deflector. As shown in the figure, in the first part, the deflection position of the main deflector is constant, the deflection amount of the feedback coil changes according to the movement of the stage, during which the electron beam is turned on and off by the blanking electrode,
The pattern is drawn. When the amount of deflection of the feedback coil reaches the limit, the blanking electrode is turned off,
The feedback coil is reset, from which the counting of the settling time of the main deflector is started. The correction value of the beam irradiation position due to the reset of the feedback coil is calculated, and the position of the main deflector is changed. The time required for this calculation is about 5 μs. Since the position of the main deflector has been changed, the feedback coil is reset again. Further, with the reset of the feedback coil, the correction value of the beam irradiation position is calculated again, and the deflection position of the main deflector is changed. The filtering process is repeated until the end of the main deflector settling wait time. If the settling wait time of the main deflector has expired at the timing of resetting the feedback coil again, the feedback coil is not reset but waits for a fixed time (5 μs), and then the exposure is restarted. The correction amount of the beam position by the main deflector in the above is the distance that the stage moves during the immediately preceding 5 μs, and the moving speed of the stage is 20 m.
Assuming m / s, it is 0.1 μm, and the small jaw waiting time immediately before the start of exposure is the time to wait for the setting of the 0.1 μm main deflector jap.

In the above description, the deflection coordinate of the electron beam in the deflectable area 31 of the electron beam is a rectangular coordinate system, and one axis is coincident with the moving direction of the stage. However, this is an ideal case, and distortion is unavoidable in actual deflection coordinates of the electron beam.
There are various types of coordinate distortions, such as a distortion in which a square becomes a parallelogram as shown in FIG. 6, and a distortion in which a square or a pincushion is formed. If there is a distortion as shown in FIG. 6, adjacent sub-frames P and Q are exposed at the illustrated position in the deflectable area, and sub-frame Q is exposed at the illustrated position in the deflectable area. A shift d1 occurs in the lateral direction (the direction perpendicular to the movement). Similarly, adjacent subframes X and Y
Are exposed at the illustrated positions, a shift d2 occurs in the lateral direction (the direction perpendicular to the movement). In the case of FIG. 6, d2 is larger than d1. This is not limited to the distortion in which the square shown in FIG. 6 becomes a parallelogram. Generally, the more the exposure is performed at a more distant position, the larger the deviation becomes. This shift is particularly problematic between adjacent frames.

Of course, it is necessary to reduce the above-mentioned distortion as much as possible, but at present it is difficult to make it completely zero. Therefore, it is conceivable to correct such a shift. However, since the shift amount differs depending on the positional relationship between the subframes, it is not easy to correct the shift, and there is a problem that the control system becomes extremely complicated. In view of this, it has been practiced to reduce the generated displacement by narrowing the area of the electron beam deflectable area 31 that is actually used for exposure in the moving direction. The area actually used for exposure is called a drawable range.

FIG. 7 is a diagram showing an example of a drawable range and the manner of exposure of a subframe when such a drawable range is set. In FIG. 7, reference numeral 33 indicates a drawable range. From the viewpoint of reducing the deviation, it is desirable that the drawable range be as narrow as possible. However, as described above, since the deflection position of the main deflector changes in accordance with the drawing pattern, when the drawable range is narrowed, the deflection position of the main deflector moves outside the drawable range. The main deflector overflow will occur frequently. In order to prevent the main deflector overflow from occurring in such a drawable range, the moving speed of the stage may be reduced. However, this reduces the throughput and loses the advantage of the continuous moving exposure method. Therefore, the drawable range needs to be widened to some extent.

[0020]

As described above, the drawable range is set with a certain margin, assuming the drawing pattern having the heaviest load. However, since such a heavy load drawing pattern is rare and usually does not require much time to draw a subframe, the deflection position at which the drawing is actually performed is, as shown in FIG.
It will be biased to one side. Even if such a deviation in the deflection position occurs at the time of drawing, if the moving direction at the time of drawing is restricted to one direction, drawing is performed at the same deflection position in other frames, so that adjacent frames are drawn. The deviation between subframes is small, and no particular problem occurs.

In the electron beam exposure apparatus, in order to move the drawing direction in one direction, after the movement from one side to the other is completed, the stage is once returned to the reverse direction, and then the drawing of the next frame is performed. Need to get started. In this case, the time required to return the stage in the reverse direction is delayed, and the throughput is reduced. Therefore, it is general to perform drawing even when returning to the reverse direction.

FIG. 8 is a diagram for explaining the deflection position of each sub-frame when the stage moves in the reverse direction. Since the drawable range 33 is set as shown in FIG.
The deflection position of the sub-frame during one of the movements indicated by 5 is 3
The deflection position of the sub-frame at the time of movement in the other direction indicated by arrow 36 is deviated downward as indicated by arrow 32b. Since drawing is performed while moving in the opposite direction between adjacent frames, a shift d3 corresponding to both ends of the drawable range 33 always occurs. In the case of FIG. 8, the maximum deviation always occurs. Of course, the drawable range 33 must be limited to a width that does not cause any problem even if such a shift occurs, but it is desirable that the shift that occurs is as small as possible even within the allowable range.

According to the present invention, a drawable range is set,
It is an object of the present invention to reduce a shift that actually occurs in a charged particle beam exposure apparatus that performs writing while moving in the opposite direction.

[0024]

In order to achieve the above object, a charged particle beam exposure apparatus according to the present invention enables a drawable range to be set independently according to a moving direction, so that two drawable ranges are provided near the center of a deflection range. Make the drawable areas overlap. That is, the charged particle beam exposure apparatus of the present invention is a charged particle beam deflector having at least a main deflector having a large deflection area and a sub deflector having a small deflection area,
A moving mechanism for placing and moving the sample, dividing the pattern exposure range of the sample into a plurality of sub-regions, setting the amount of deflection by the main deflector, and deflecting the charged particle beam by the sub-deflector. Pattern exposure is performed on each sub-region while changing the position of the sample. In the charged particle beam exposure apparatus, a drawable range for limiting a range of a moving direction of a sample used for pattern exposure is set in a main deflection area by a main deflector. This is also performed during the reciprocating movement in the reverse direction, and the drawable range is independently set according to the moving direction of the sample.

It is desirable that the drawable ranges in different movement directions overlap at the center of the main deflection area, and that the drawable ranges in different directions extend in different directions. In the charged particle beam exposure apparatus of the present invention, the drawable range can be set independently according to the moving direction of the sample, so that when drawing a normal pattern, the drawable range is set so that the parts where subframes are unevenly distributed overlap. This can reduce the deviation between frames that actually occurs.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electron beam exposure apparatus according to an embodiment of the present invention has the same configuration as that of the conventional one described above, except that a different drawing range is set according to the moving direction. different. FIG. 9 is a diagram showing a drawing range in the electron beam exposure apparatus according to the embodiment of the present invention. Reference numeral 33a indicates a drawable range when moving in the direction indicated by arrow 35, and reference numeral 33b indicates a drawable range when moving in the direction indicated by arrow 36.

FIG. 10 is a diagram showing a deflection position when a sub-frame is drawn by the electron beam exposure apparatus of the embodiment. FIG. 10A shows a state where the electron beam exposure apparatus moves in the first direction indicated by an arrow 35. The deflection position of each sub-frame 32a is shown, and (2) shows the deflection position of each sub-frame 32b when moving in the second direction indicated by the arrow 36. As described above, when a normal pattern is drawn, the deflection position of each sub-frame is biased to one side of the drawable range. In the present embodiment, however, the drawable range 33a is shifted from the vicinity of the center of the main deflection range 31. Since the drawing range 33b extends downward from the vicinity of the center of the main deflection range 31 and extends upward, the deflection position of each subframe in the first and second movement directions is set near the center of the main deflection range 31. As a result, the same effect can be obtained as when the drawing range is substantially narrowed. Therefore, even if the deflection coordinates are distorted and the coordinate axes do not coincide with the moving direction of the stage, the deviation between adjacent frames is small.

[0028]

As described above, according to the present invention,
In both the case of moving the stage in one direction and the other direction, the drawing is performed in the same narrow area of the main deflection area, so that the deviation from the adjacent frame is reduced and the drawing quality is reduced. Can be improved. In addition, when the above-mentioned shift is corrected by the deflection ratio or the like, the shift is small and thus is simple.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of an electron beam exposure apparatus to which the present invention can be applied.

FIG. 2 is a diagram showing a change in an exposure area in a continuous movement exposure method.

FIG. 3 is a diagram illustrating an operation of a feedback coil and a resetting of a main deflector following movement.

FIG. 4 is a diagram showing a configuration of a control circuit in a conventional example.

FIG. 5 is a diagram showing a setting and resetting sequence of a main deflector in a conventional example.

FIG. 6 is a diagram illustrating the occurrence of a shift when the deflection coordinate is distorted and the coordinate axis does not match the moving direction of the stage.

FIG. 7 is a diagram illustrating a drawable range and uneven distribution of deflection positions of subframes within the drawable range.

FIG. 8 is a diagram illustrating a problem in a case where drawing is performed even when moving in the reverse direction.

FIG. 9 is a diagram showing a drawing range in the electron beam exposure apparatus according to the embodiment of the present invention.

FIG. 10 is a diagram showing a deflection position of a sub-frame in two directions of movement in the electron beam exposure apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 8 housing (column) 9 electron gun 10, 12, 15 lens 11 blanking electrode 13 feedback coil 14 sub deflector 16 main deflector 17 stage 18 sample 30 frame 31 main deflection area 32 ... Sub-frames 33, 33a, 33b ...

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H097 AA03 AB05 BB03 CA16 EA03 KA28 LA10 5C033 GG03 5F056 AA20 CA04 CB14 CC05

Claims (3)

[Claims] A charged particle beam deflecting unit having at least a main deflector having a large deflection area and a sub deflector having a small deflection area; and a moving mechanism for mounting and moving the sample. Dividing the pattern exposure range into multiple sub-regions,
After setting the amount of deflection by the main deflector, the sub-deflector pattern-exposes each sub-region while changing the deflection position of the charged particle beam, and the pattern exposure moves the sample by the moving mechanism. A charged particle beam exposure apparatus that performs a correction while exposing a shift between the sample and the charged particle beam due to the movement to the charged particle beam deflecting unit to correct an exposure position. A drawable range is set to limit a range in the moving direction of the sample used for the pattern exposure in the area, and the pattern exposure is performed during the reciprocating movement of the sample during the reciprocating movement of the sample. The charged particle beam exposure apparatus is characterized in that the drawing range is set independently according to the moving direction of the sample. 2. The charged particle beam exposure apparatus according to claim 1, wherein the drawable ranges in different movement directions partially overlap each other. 3. The charged particle beam exposure apparatus according to claim 2, wherein the drawable range overlaps at a central portion of the main deflection area, and the drawable ranges in different directions are spread in different directions. Beam exposure equipment.