JP2007194293A - Electron beam drawing device - Google Patents

Abstract

An electron beam writing apparatus capable of calculating an optimum moving speed of a sample stage without performing empty drawing and optimally controlling the sample stage speed and shortening a drawing processing time.
Rendering data is output to a graphic decomposing unit 3, decomposed into a shot-capable size, and stored in a drawing data buffer 4. The counter 7 counts the number of times the electron beam is irradiated in the subfield output from the decomposition unit 3 and outputs it to the sample stage speed calculation unit 17. The data stored in the buffer 4 is read by the correction calculation unit 5 and the subfield coordinates currently being drawn are output to the sample stage control unit 14. The buffer 4 stores drawing data for one subfield or more, and the operation of the disassembling unit 3 and the operation of the calculating unit 5 have a phase difference of one subfield or more, and the calculating unit 17 is one or more ahead of the subfield currently being drawn. Output the number of drawing data. The sample stage control unit 14 calculates the optimum moving speed of the sample stage 13 based on the number of data 16 for each output subfield of the counter 7 and controls the sample stage moving speed.
[Selection] Figure 1

Description

  The present invention relates to an electron beam drawing apparatus, and more particularly to an electron beam drawing apparatus capable of controlling a moving speed of a sample stage during drawing.

  There is a technique described in Patent Document 1 as a conventional technique related to sample stage control of an electron beam drawing apparatus that performs drawing by continuously moving the sample stage successively.

  In the electron beam drawing apparatus, an electron beam emitted from an electron gun is converged by a column and irradiated on a sample mounted on a sample stage. The drawing data stored in the external storage device is output to the graphic decomposition unit in accordance with an instruction from the control computer.

  The graphic decomposition unit decomposes the input drawing data into figures of a size that can be shot, and outputs the figure to the correction calculation unit. The correction operation unit performs correction operations such as deflection distortion and beam size on the decomposed drawing data, and outputs them to the DA converter. The DA converter converts the drawing data output from the correction calculation unit into an analog value, drives the deflector, irradiates a desired position on the sample, and draws a desired pattern.

  In addition, the correction calculation unit outputs drawing position data for which drawing is currently performed to the sample stage control. The sample stage control refers to the target speed table calculated in advance and controls the speed of the sample stage.

  Here, a rapid change in the speed of the sample stage becomes a factor that causes a structure such as a column to vibrate. When the vibration of the structure occurs, an error occurs in the irradiation position of the electron beam, and the drawing accuracy is deteriorated.

  Further, when there is a difference between the moving speed of the sample stage and the progress speed of the drawing, there is a difference between the drawing position and the position of the sample stage. If the difference exceeds the deflectable range, drawing cannot be performed.

  Therefore, it is necessary to control the sample stage so as not to cause acceleration / deceleration as much as possible and to reduce the difference between the sample stage position and the drawing position.

  Next, examples of drawing patterns will be described with reference to FIGS.

  FIG. 5 is a diagram illustrating an example of a drawing pattern. In this example, 30 chips 26 are arranged on the wafer 25. Each chip has the same drawing pattern, but the actual drawing pattern may not be the same chip. Drawing is performed in units of stripes 27. Drawing is performed by continuously moving the sample stage in the longitudinal direction of the stripe 27.

  Further, drawing is performed by deflection of the electron beam in a direction orthogonal to the moving direction of the sample stage. Therefore, the width of the stripe 27 needs to be equal to or less than the maximum deflection width.

  FIG. 6 is an enlarged view of the stripe 27 shown in FIG. In this example, a part of the chip is drawn with one stripe, and a part of the stripe that covers each chip is a chip stripe 28.

  In FIG. 5, the coordinates indicated by Ycs1 to Ycs4 are the coordinates of the lower side of each chip stripe 28, and are the chip stripe start coordinates. The chip stripe 28 is further divided into subfields 29 of an appropriate size, and the moving speed of the sample stage is controlled in units of subfields 29.

  Here, the contents of the target speed table will be described. The target moving speed table stores the target moving speed of the sample stage corresponding to the drawing position data being drawn. The target moving speed is the moving speed of the sample stage determined by the drawing pattern density.

  In this calculation method, first, the drawing pattern is divided into subfields 29 of an appropriate size. The drawing pattern divided into the subfields 29 is actually drawn using only the external storage device to the correction calculation unit 5 and the drawing time for each subfield 29 is measured. This operation is called empty drawing.

  Here, the target moving speed is calculated based on the measured drawing time for each subfield 29. FIG. 7 shows an example of the target speed table. This example is a target speed table for drawing the stripe shown in FIG. 6, and is an example in which the same drawing pattern is drawn by four chips in the direction of movement of the sample stage. 7 shows the target moving speed of the part where CS1 to CS4 in FIG. 7 actually perform drawing.

  In the case of the above-described example, since each chip stripe has the same drawing pattern, empty drawing for one chip is executed, and the result is arranged in accordance with the drawing coordinates of each chip, thereby setting target coordinates for one stripe. A table can be calculated.

  In the sample stage control, the speed of the sample stage is controlled based on the target sample stage speed output from the target speed table. The sample table coordinates output from the laser length meter are differentiated by a differentiating circuit to obtain the current moving speed of the sample table.

  The subtracter obtains the difference (speed deviation) between the target moving speed and the current sample stage moving speed and outputs it to the mixing circuit. Further, the difference (position deviation) between the drawing position data and the sample table coordinates is obtained by a subtracter and output to the mixing circuit. Based on the output of the subtracter, the mixing circuit calculates the sample stage moving speed at which both the position deviation and the speed deviation are minimized, and controls the moving speed of the sample stage according to the calculated speed.

  By operating in this way, for example, even when the target sample stage speed changes greatly due to a large change in the density of the drawing pattern, it is possible to perform optimum sample stage moving speed control.

JP-A-5-267134

  By the way, as described above, in the conventional technique, it is necessary to measure the drawing time by performing a drawing operation such as empty drawing in advance and obtain the target sample stage speed for each drawing position.

  Since the calculation of the target sample stage moving speed requires the same time as the drawing, the time is wasted, the drawing processing time is increased, and the throughput is reduced.

  It is an object of the present invention to calculate an optimal movement speed of a sample stage in real time without performing empty drawing, to optimally control the sample stage speed, and to reduce the overall drawing processing time. It is to realize a beam drawing apparatus.

  The electron beam drawing apparatus according to the present invention outputs a decomposing unit that decomposes the drawing data divided into small areas into a size that can be shot, a counting unit that counts the number of times of electron beam irradiation for each small region, and an output from the decomposing unit. Data storage means for storing at least one small area of drawing data to be performed, correction data for reading out the drawing data output from the data storage means, and correcting the read drawing data; Based on the number of drawing data for each region, a speed calculating means for calculating the optimum moving speed of the sample stage and a sample stage movement control means for controlling the moving speed of the sample stage are provided.

  The sample stage movement control means calculates an optimum sample stage movement speed based on the number of drawing data counted in the process of the drawing operation, and controls the movement speed of the sample stage according to the calculated optimum sample stage movement speed. And draw.

  According to the present invention, it is possible to calculate the optimum moving speed of the sample stage in real time without performing empty drawing, to optimally control the sample stage speed, and to reduce the overall drawing processing time. A beam drawing apparatus can be realized.

  In addition, since drawing can be performed at an optimum sample stage speed, vibration of the apparatus accompanying the acceleration / deceleration of the sample stage is not generated, so that it is possible to improve drawing accuracy.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram of an electron beam drawing apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is an external storage device, 2 is a control computer, 3 is a graphic decomposition unit, 4 is a drawing data buffer, 5 is a correction operation unit, 6 is a DA converter, 7 is a drawing data counter, 8 is an electron gun, 9 is a column, 10 is a deflector, 11 is an electron beam, 12 is a sample, 13 is a sample stage, 14 is a sample stage control unit, 15 is drawing position data, 16 is the number of drawing data, 17 is a sample stage speed calculation unit, 18 is a differentiation circuit, 19 and 20 are subtractors, 21 is a mixing circuit, and 22 is a laser length meter.

  Next, the operation of the first embodiment of the present invention will be described. Note that the signal switching operation and the like in the sample stage control unit 14 are performed by a command from the control computer 2.

  In FIG. 1, an electron beam 11 emitted from an electron gun 8 is converged by a column 9 and irradiated onto a sample 12 mounted on a sample stage 13. The drawing data as drawing pattern information is divided into small areas of appropriate sizes called subfields and stored in the external storage device 1.

  The drawing data stored in the external storage device 1 is output to the graphic decomposition unit 3 in accordance with the drawing order of the subfields according to an instruction from the control computer 2. The graphic decomposition unit 3 decomposes the input drawing data into a size that can be shot and stores it in the drawing data buffer 4.

  At this time, the drawing data counter 7 outputs the number of drawing data for each subfield output from the graphic decomposition unit 3, that is, the number of times of irradiation of the electron beam in the subfield. Output.

  The drawing data stored in the drawing data buffer 4 is read by the correction calculation unit 5. The correction calculation unit 5 performs correction calculations such as deflection distortion and beam size correction on the decomposed drawing data, and outputs the result to the DA converter 6. Further, the correction calculation unit 5 outputs the coordinates of the subfield currently being drawn to the sample stage control unit 14 as the drawing coordinates 15.

  The DA converter 6 converts the drawing data output from the correction calculation unit 5 into an analog value, drives the deflector 10, irradiates the electron beam 11 to a desired position on the sample 12, and the desired value on the sample 12. Draw a pattern.

  Here, the drawing data buffer 4 has a capacity capable of storing drawing data for one subfield or more. As a result, the operation of the graphic decomposing unit 3 and the operation of the subsequent correction calculating unit 5 can have a phase difference of one subfield or more, and the sample table speed calculating unit 17 has one of the subfields currently being drawn. It becomes possible to output the number of drawing data of the subfields described above.

  The sample stage control unit 14 calculates the optimum moving speed of the sample stage 13 based on the number of data 16 for each subfield output from the graphic data counter 7 and uses this as the target moving speed to determine the moving speed of the sample stage 13. Control. The subsequent operation of the sample stage control unit is the same as the conventional method.

  Here, the optimum moving speed of the sample stage during drawing will be described.

  The optimal moving speed of the sample stage is the moving speed of the sample stage 13 equal to the drawing speed. As a result, the deflection amount of the beam in the direction of movement of the sample stage can be minimized.

Here, the chip stripe shown in FIG. 5 will be specifically described as an example.
The chip stripe shown in FIG. 5 is divided into square subfields 29 each having a size of ΔL, and N subfields 29 are arranged in the horizontal direction in FIG. 5, that is, in the direction perpendicular to the moving direction of the sample stage 13. Are lined up.

  At this time, while the N subfields 29 are drawn, the speed at which the sample stage moves by ΔL is the optimum sample stage moving speed in this pattern. Further, the moving distance of the sample stage 13 per subfield is ΔL / N because N subfields are arranged in the horizontal direction.

On the other hand, the time T _sf required to draw one subfield is determined by the electron beam irradiation number N _sh , the irradiation time T _sh , the deflection waiting time T _wt , and the overhead time T _oh in the subfield 29. It can be calculated in (1).
T _sf = (T _sh + T _wt ) · N _sh + T _oh −−− (1)
Here, the deflection waiting time T _wt and the overhead time T _oh are determined by the performance of the apparatus, and the irradiation time T _sh is determined by the sensitivity of the resist to be used and the current density of the electron beam, that is, the drawing conditions.

For this reason, T _sh , T _wt , and T _oh are known constants, and can be calculated by a function using N _sh, that is, the number of drawing data in the subfield as a variable.

Therefore, the optimum sample _stage moving speed V _sf for drawing a certain subfield can be calculated by the following equation (2).

V _sf = (ΔL / N) / T _sf = (ΔL / N) / ((T _sh + T _wt ) · N _sh + T _oh ) −−− (2)
FIG. 2 is a diagram illustrating an internal configuration of the target speed calculation unit 17. In FIG. 2, the target speed calculation unit 17 includes an optimum speed calculation unit 33, a mixing circuit 34, a selector 35, and a register 36.

  In the target speed calculation unit 17, when the drawing data number 16 input from the drawing data number counter 7 is input to the optimum speed calculation unit 33 and the subfield is drawn using the above equation (2). Are calculated and output to the mixing circuit 34 sequentially.

  The drawing data number 16 output from the drawing data number counter 7 has a phase difference of one subfield or more from that of the subfield actually drawing. As a result, it is possible to input the optimum moving speeds of the subfield in which drawing is currently performed and one or more subfields before and after the subfield to the mixing circuit 34.

  The mixing circuit 34 calculates and outputs a target moving speed 32 that minimizes a change in the actual sample stage moving speed based on the plurality of optimum moving speeds. As a result, it is possible to calculate the target sample table speed while predicting the change in the sample table speed, and it is possible to reduce the change in the sample table moving speed even when the drawing density changes rapidly.

  On the other hand, the target moving speed cannot be calculated when the graphic decomposing unit 3 is not performing a drawing operation, such as at the start of drawing or at the boundary between chip stripes. In that case, the selector 35 is switched to output the standard speed set in the register 36 in advance as the target moving speed 32. By operating in this way, the optimum target moving speed is always calculated and the sample stage speed is controlled.

  As described above, according to the first embodiment of the present invention, it is possible to calculate and control the optimum speed of the sample stage without performing empty drawing, so that it is possible to reduce the overall drawing processing time. A beam drawing apparatus can be realized.

  In addition, even when the drawing speed changes abruptly, the change in the speed of the sample stage can be reduced. Therefore, the apparatus can be prevented from generating vibration due to acceleration and deceleration of the sample stage, and the drawing accuracy can be improved.

  Here, depending on the drawing pattern, for example, there may be a case where the distance between the chip stripes is largely separated as in the case of drawing a stripe of only the evaluation pattern arranged around the drawing pattern.

  When drawing such a stripe, the time for moving the chip stripe is a dead time that does not contribute to the drawing.

  Therefore, when the chip stripes are far apart, the untitled time can be reduced by moving the sample stage 13 faster than when the chip stripes are not far apart.

  Here, if the standard speed preset in the target speed calculator 17 is increased, the dead time can be reduced, but conversely, wasteful acceleration / deceleration is performed when the distance between chip stripes is small.

  FIG. 3 is an overall configuration diagram of an electron beam drawing apparatus according to the second embodiment of the present invention, and is a configuration example for solving the above problem.

  The difference between the configuration of the first embodiment and the second embodiment described above is that, in the internal configuration of the sample stage control unit 14, the start coordinate memory 30 that stores the drawing start coordinates of each chip stripe in the stripe, and The selector 31 is added.

  In the start coordinate memory 30, the chip stripe start coordinates indicated by Ycs1 to Ycs4 shown in FIG. As shown in FIG.

  As a result, the positional deviation output from the subtractor 19 changes according to the distance between the chip stripes. That is, as the distance between chip stripes increases, the positional deviation output from the subtractor 19 also increases. When the positional deviation of the mixing circuit 21 is large, the sample stage moving speed is output so as to reduce the position deviation. Therefore, the higher the table stage moving speed is, the higher the sample stage moving speed is specified. The time required for moving the sample stage between stripes can be reduced.

  By operating in this way, it is possible to realize further reduction of dead time.

  FIG. 4 is an overall configuration diagram of an electron beam drawing apparatus according to the third embodiment of the present invention.

  In FIG. 4, 37 is a first drawing data control unit, 38 is a second drawing data control unit, 39 is a drawing time measuring unit, 40 is a first drawing time memory 1, 41 is a second drawing time memory, Reference numeral 42 denotes a selector, 43 denotes an optimum speed calculation unit, and 44 denotes a sample stage control unit.

  Here, the first drawing data control unit 37 and the second drawing data control unit 38 have the same configuration, and have a function of decomposing the drawing data and performing a correction operation. The drawing data measuring unit 39 has a function of measuring the drawing time for each small area of the drawing pattern divided into the small areas. The first drawing time memory 40 and the second drawing time memory 41 include the drawing time. This is a memory for storing the drawing time measured by the measuring unit 39.

  Next, the operation of the third embodiment will be described.

  First, a drawing operation of a stripe drawing pattern to be drawn first is performed using the second drawing data control unit 38. At this time, the drawing time measuring unit 39 measures the drawing time for each small region and stores it in the first drawing time memory 40. With this operation, the drawing time for each small area of the first stripe is stored in the first drawing time memory 40.

  Next, actual drawing is performed on the drawing pattern of the first stripe using the first drawing data control unit 37. At this time, the sample stage control unit 44 reads the drawing time for each small area stored in the first drawing time memory 40 based on the drawing position data 15 output from the first drawing data control unit 37, and calculates the optimum speed. An optimum sample stage moving speed is calculated based on the drawing time read by the unit 43, and the movement of the sample stage 13 is controlled according to the calculated sample stage speed.

  The first drawing data control unit 37 draws the drawing pattern of the first stripe, and at the same time, the second drawing data control unit 38 performs the drawing operation using the drawing pattern of the second stripe. At this time, the drawing time measuring unit 39 measures the drawing time for each small region and stores it in the second drawing time memory 41. By this operation, the drawing time for each small area of the first stripe is stored in the second drawing time memory 41.

  Next, the actual drawing of the drawing pattern of the second stripe is performed using the first drawing data control unit 37. At this time, the sample stage control unit 44 calculates the optimum sample stage speed while reading the second drawing time memory 41 in which the drawing time of the second stripe is stored.

  At the same time, the second drawing data control unit 38 is used to perform the drawing operation using the drawing pattern of the third stripe, and the drawing time for each small area is stored in the first drawing time memory 40.

  By repeating the above operation, it is possible to calculate the optimum sample stage speed and perform drawing without performing empty drawing of the entire drawing pattern.

  In the third embodiment described above, the overhead time for the first one stripe is generated. However, because the drawing time is actually measured by performing the drawing operation of the drawing pattern, the sample stage speed is calculated from the result. Thus, it is possible to calculate the optimum sample stage speed more accurately.

1 is an overall configuration diagram of an electron beam drawing apparatus according to a first embodiment of the present invention. It is a block diagram of the target speed calculating part in 1st Embodiment. It is a whole block diagram of the electron beam drawing apparatus which is the 2nd Embodiment of this invention. It is a whole block diagram of the electron beam drawing apparatus which is the 3rd Embodiment of this invention. It is a figure which shows an example of the drawing pattern by an electron beam drawing apparatus. FIG. 6 is an enlarged view of the stripe shown in FIG. 5. It is a figure which shows an example of the target speed table in an electron beam drawing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 External storage device 2 Control computer 3 Graphic decomposition | disassembly part 4 Drawing data buffer 5 Correction | amendment calculating part 6 DA converter 7 Drawing data counter 8 Electron gun 9 Column 10 Deflector 11 Electron beam 12 Sample 13 Sample stand 14, 44 Sample stand control part 15 Drawing position data 16 Number of drawing data 17 Sample stage speed calculation unit 18 Differentiating circuit 19, 20 Subtractor 21, 34 Mixing circuit 22 Laser length meter 25 Wafer 26 Chip 27 Stripe 28 Chip stripe 29 Subfield 30 Start coordinate memory 31, 35 , 42 Selector 32 Target movement speed 33, 43 Optimal speed calculation unit 36 Register 37 First drawing data control unit 38 Second drawing data control unit 39 Drawing time measuring means 40 First drawing time memory 41 Second drawing time memory

Claims (7)

In an electron beam drawing apparatus that divides a drawing pattern into small regions, moves a sample stage on which the sample is mounted, irradiates the sample with an electron beam, and performs drawing for each of the divided small regions,
Decomposing means for decomposing the drawing data divided into the small areas into shot-capable sizes;
A counting means for counting the number of times of irradiation of the electron beam for each small area;
Data storage means for storing the drawing data output by the disassembling means for one or more small areas;
Correction calculation means for reading the drawing data output by the data storage means and performing correction calculation on the read drawing data;
Based on the number of drawing data for each small area where the number of times of irradiation is counted, speed calculation means for calculating the optimum moving speed of the sample stage,
Sample stage movement control means for controlling the movement speed of the sample stage;
The sample stage movement control means calculates an optimal sample stage movement speed based on the number of drawing data counted in the process of the drawing operation, and the movement speed of the sample stage according to the calculated optimum sample stage movement speed An electron beam drawing apparatus characterized in that drawing is performed by controlling the above.   2. The electron beam drawing apparatus according to claim 1, wherein the sample stage movement control means calculates the optimum sample stage movement speed based on the number of drawing data, electron beam irradiation time, deflection waiting time and overhead time in the small area. An electron beam drawing apparatus.   2. The electron beam drawing apparatus according to claim 1, wherein the data storage means stores data for one or more small areas, and thereby stores each of the small areas one or more ahead of the currently drawn small area. The number of drawing data is counted in advance by the counting unit, and the number of drawing data for each small area is input to the sample stage movement control unit. The sample stage movement control unit is configured to draw the drawing data of the small area currently being drawn. An electron beam drawing apparatus characterized in that an optimum sample stage moving speed is calculated based on the number and the number of drawing data of a plurality of small areas to be drawn before and after the number, and the movement of the sample stage is controlled.   2. The electron beam drawing apparatus according to claim 1, further comprising a drawing start coordinate table for storing drawing start coordinates of a drawing pattern, wherein the sample stage movement control means includes a plurality of drawing patterns while the sample stage is continuously moved once. An electron beam drawing apparatus that controls the sample stage speed using the drawing start coordinates of the next drawing pattern output by the drawing start coordinate table coordinates between the drawing patterns. In an electron beam drawing apparatus that divides a drawing pattern into small regions, moves a sample stage on which the sample is mounted, irradiates the sample with an electron beam, and performs drawing for each of the divided small regions,
A first drawing data control means for decomposing the drawing data divided into the small areas into shot-capable sizes and performing a correction operation on the divided drawing data;
Second drawing data control means for decomposing the drawing data divided into the small regions into shot-capable sizes and performing a correction operation on the divided drawing data;
Counting means for counting the number of electron beam irradiation times for each of the small regions output by the second drawing data control means;
Storage means for storing the number of drawing data for each small area counted by the counting means;
Speed calculating means for calculating the optimum sample stage moving speed based on the number of drawing data for each small area read from the storage means;
Sample stage movement control means for controlling the movement speed of the sample stage;
A drawing pattern drawing operation in which the first drawing data control means performs drawing on the sample, and at the same time, the second drawing data control means performs the next drawing using the first drawing data control means. And the counting means counts the number of drawing data output by the second drawing data processing means for each small area, stores the counted number of drawing data for each small area in the storage means, The movement control means reads the number of drawing data for each small area stored in the storage means at the time of the actual drawing, calculates the optimum sample stage moving speed based on the read number of drawing data, and calculates the calculated optimum sample. An electron beam drawing apparatus which performs drawing while controlling the moving speed of the sample stage according to the moving speed of the stage.   6. The electron beam drawing apparatus according to claim 5, wherein the second drawing data control means measures the time required for drawing for each small area, and stores the measured drawing time for each small area in the storage means. An electron beam drawing apparatus, wherein an optimum sample stage moving speed is calculated based on the drawn drawing time, and drawing is performed while controlling the sample stage moving speed according to the calculated optimum sample stage moving speed. In the electron beam drawing method of dividing the drawing pattern into small areas, moving the sample stage on which the sample is mounted, irradiating the sample with an electron beam, and drawing for each of the divided small areas,
Decomposing the drawing data divided into the above small areas into shot-capable sizes,
Count the number of electron beam irradiations for each small area,
Accumulate one or more small areas of the decomposed drawing data,
Read the stored drawing data, perform correction calculation on the read drawing data,
Based on the number of drawing data for each small area where the number of times of irradiation is counted, the optimal moving speed of the sample stage is calculated,
Based on the number of drawing data counted in the process of drawing operation, the optimum sample stage moving speed is calculated, and drawing is performed by controlling the moving speed of the sample stage according to the calculated optimum sample stage moving speed. Electron beam drawing method.

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