JP3004034B2 - Charged beam drawing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a charged beam writing method for writing a fine pattern such as an LSI on a sample, and particularly to a writing apparatus of a continuous stage moving type. And a charged beam writing method for optimizing the moving speed of the stage.

(Prior Art) Conventionally, various electron beam writing apparatuses have been used for writing a desired pattern on a sample such as a semiconductor wafer. In this apparatus, there are a continuous movement method and a step-and-repeat method for moving a stage on which a sample is placed. In the continuous movement method, a high throughput can be obtained because the stage movement has no dead time compared to the step & repeat method. However, if the optimum stage speed is not determined according to the pattern density, a writing error or a decrease in throughput is caused.

Therefore, in the electron beam lithography system of the continuous stage moving system, the following is performed in order to determine the stage speed according to the pattern density. That is, the stage is actually moved to perform dummy drawing, and it is determined whether or not a drawing error has occurred. Further, the above operation is repeated while changing the moving speed of the stage, and the maximum stage speed at which no error occurs is obtained. However, in the case of this method, since the stage is actually made to perform the dummy traveling, a very large amount of dead time is required in addition to the drawing.

(Problems to be Solved by the Invention) As described above, in the electron beam lithography apparatus of the conventional continuous stage moving system, unless an optimum stage moving speed is determined, a drawing error or a decrease in throughput is caused.
In addition, when the stage is moved and dummy drawing is performed in order to obtain an optimum stage moving speed, there is a problem that a very large amount of waste time is required and the operation rate of the apparatus is reduced.

The present invention has been made in consideration of the above circumstances, and has as its object to easily obtain the optimum moving speed of the stage without actually moving the stage, thereby improving the operation rate of the apparatus and It is an object of the present invention to provide a charged beam writing method capable of improving the writing throughput.

[Summary of the Invention] The gist of the present invention is to provide a charged beam lithography system of a continuous stage moving type, which determines a moving speed of a stage by calculating from pattern data and a beam deflection area. In consideration of the above, an optimum stage moving speed is determined.

That is, the present invention provides a charged beam drawing method for dividing a drawing region on a sample into frames of a predetermined width and drawing the frame while continuously moving a stage on which the sample is placed. Is divided into small areas, the time required for drawing is determined for each divided small area, and the stage moving speed is determined from the relationship between these times and the beam deflection width in the stage continuous moving direction. is there.

Further, according to the present invention, in a charged beam drawing method for dividing a drawing area on a sample into frames of a predetermined width and drawing the frame while continuously moving a stage on which the sample is placed, the frame may have a maximum size in a stage continuous moving direction. Assuming that the stage was moved at a certain speed by dividing the stage into small regions with a fixed width in the continuous movement direction of the stage at intervals smaller than the beam deflection width, finding the required drawing time required for drawing for each of the divided small regions. The maximum drawing time of the small area at this speed is obtained, the small area in the frame is evaluated in order from the end, and the required drawing time of each small area is added to the value A, and the maximum drawing time corresponding to the number of evaluated small areas. Is compared with the sum B of the maximum drawing times corresponding to the number of the largest small areas included in the maximum beam deflection width. B It is a method to determine the substantially maximum stage moving speed does not exceed C.

(Operation) In the present invention, the frame is divided into small regions in the direction of continuous movement of the stage, and the required drawing time of each small region is obtained from the beam positioning time and the irradiation cycle for each small region. Assuming that the stage is moved at a certain speed, the relationship between the pattern irradiation position and the beam deflection position is evaluated while shifting the frame for each small area. The stage speed to be evaluated next is determined according to the evaluation result, and the same evaluation is repeated, and the stage speed is determined so that the beam position does not become over-deflected.

If the required drawing time of the small area exceeds the maximum drawing time,
It is assumed that the excess is added to the next small area and the beam is deflected by the width of the small area for writing. At this time, since the maximum deflection width of the beam is larger than the width of the small region, it is possible to draw even in the case described above. If the required writing time of the small area is several times longer than the maximum writing time, it is necessary to deflect the beam by a plurality of small area widths. Further, even if the required drawing time of each small area is not so long, since the protruding time is accumulated sequentially, it is necessary to deflect the beam by a plurality of small area widths. If the deflection width at this time is smaller than the maximum deflection width of the beam, writing is possible, but if it is large, a writing error occurs.

In the present invention, since the maximum stage movement speed at which the deflection amount of the beam to be deflected does not exceed the maximum deflection width of the beam is obtained, the maximum stage movement speed without causing a drawing error, that is, the optimum speed can be obtained. Will be.

(Examples) Hereinafter, details of the present invention will be described with reference to the illustrated examples.

FIG. 1 is a schematic structural view showing an electron beam drawing apparatus used in the method of one embodiment of the present invention. In the figure, reference numeral 10 denotes a sample chamber, in which a stage 12 on which a sample 11 is mounted is accommodated. The sample stage 12 is moved by a drive circuit 31, and the movement position of the stage 12 is to be measured by a laser length measuring system 32.

Above the sample chamber 10, an electron optical system 20 is provided. The electron optical system 20 includes an electron gun 21, various lenses 22a to 22
e, various deflectors 23 to 26, beam forming aperture mask 27,
It consists of 28 mags. The deflector 23 is a blanking deflector for blanking a beam.
A blanking signal is applied to 23 from a blanking control circuit 33. The deflector 24 is a beam shaping deflector for changing the size and shape of the beam. A deflection voltage is applied to the deflector 24 from a variable beam size control circuit 34. A deflector 25 is a main deflector for positioning the beam in a predetermined area (sub-field), and a deflector 26 is a sub-deflector for deflecting the beam in the positioned area and drawing the area. , 25 are supplied with a deflection signal from a deflection control circuit 35.

In the figure, reference numeral 30 denotes a computer for performing various controls; 36, a data expansion circuit for expanding EB pattern data as described later;
Indicates a memory for storing each expanded information.

Next, a method of determining the stage speed using the apparatus shown in FIG. 1 will be described. The apparatus shown in FIG. 1 forms a variable shaped beam, performs vector scan drawing by two-step main and sub-deflection, and divides the drawing area on the sample into frames having a width determined by the beam deflection width of the deflector 25 in the Y direction. Then, a continuous stage moving method of drawing a frame while continuously moving the stage 12 in the X direction was adopted.

First, the EB pattern data of a certain frame (a band-shaped drawing area obtained by cutting the chip data in the continuous movement direction), which is compressed for the electron beam drawing apparatus, is transferred to the data development circuit 36. In the data expansion circuit 36, the position of the subfield (the area to be drawn by the sub deflector) and the number of shots (the number of graphics) in the subfield are all expanded for the subfield, and the result is stored in the memory 37.

Next, as shown in FIG. 2, the frame is divided into small areas having a frame width in the X direction (continuous stage movement direction) at a certain interval and in the Y direction. Here, the width of the small area is set smaller than the maximum deflection width of the beam in the X direction. There is no relation between the size of the small area and the size of the subfield. The size of the subfield may be larger than the width of the small area as shown by a broken line P in FIG. May be smaller than the width of the small area.

The computer 30 reads the coordinates and the number of shots of all the subfields from the memory 37 and draws each subfield from the positioning time (main deflection settling time) and the irradiation cycle (irradiation time + subdeflection settling time) of the subfield. The required time (required drawing time) is obtained. Subfields belonging to the divided small areas are selected, and the required drawing time of each small area is obtained. FIG. 3 shows the relationship between each small area and the required drawing time.

In a drawing apparatus of the continuous stage movement type, the stage must be moved at a constant speed during drawing. Thus, when the stage speed is determined, the maximum pattern amount that can be drawn while the stage passes through the small area is determined. Here, it is assumed that the stage is continuously moved at a certain constant speed, and the following evaluation is performed for each small area of the frame width. For example, considering the case of drawing the pattern data of the small area 1 in FIG. 3, first, when the speed of the stage is determined, the maximum drawing time of each small area is determined.

As shown in FIG. 4, when the required drawing time of the pattern data A exceeds the maximum drawing time, the remaining drawing occurs and the entire pattern data A cannot be drawn when the stage is in the range of the small area 1. The rest of the drawing is drawn by deflecting the beam by the small area when the stage enters the range of the next small area 2. As long as the maximum deflection width (deflection area) of the beam in the continuous stage movement method permits, the pattern of the small area 1 is drawn even if the position of the stage is in the subsequent small area.

In this way, the beam deflection amount caused by the current position of the stage and the remaining image is evaluated. Then, such evaluation is continued from the beginning to the end of the frame.
An evaluation is made as to whether or not the deflection region over (when rendering is to be performed at a position beyond the deflection region) as shown in the drawing occurs.

In FIG. 5, since the stage speed is high, the remaining drawing increases, and the pattern data D of the small area 4 is about to be drawn at a position beyond the deflection area as shown in FIG.
This is an example in which the deflection area is over.

If the deflection area is not exceeded in the first evaluation, the stage speed is increased and re-evaluation is performed. If the deflection area is exceeded, the stage speed is reduced and re-evaluated. This stage speed can be selected by using the successive approximation method generally used in A / D converters, assuming that the maximum stage speed is 100 mm / s, and that if nine evaluations are performed, the stage speed will be 0.2 mm / s accurate. Speed can be determined.

As described above, the stage speed is determined for all frames before drawing, and is stored in the disk together with the pattern data. At the time of drawing, the speed calculated for each frame is read from the disk, and the stage is continuously moved at the specified speed to execute drawing.

Thus, according to the present embodiment, the frame is virtually divided into small areas, the time required for drawing is determined for each divided small area, and the stage is determined from the relationship between these times and the beam deflection width in the stage continuous movement direction. , The optimum moving speed of the stage can be determined without actually moving the stage. Therefore, it is possible to improve the writing throughput and the operating rate of the electron beam writing apparatus of the continuous stage moving type, and its usefulness is enormous.

The present invention is not limited to the above embodiments. The moving speed of the stage described above differs between a case where one chip is arranged and a case where a plurality of chips are arranged. Therefore,
When evaluating the stage speed, it is necessary to obtain the chip arrangement information of the frame to be drawn in one pass from the layout information of the drawing chip, and then to develop the drawing time of each area shown in FIG. 3 over the entire frame. is there. Similarly, when different chips are drawn at once, the drawing time may be expanded and evaluated over all frames to be drawn in one pass as shown in FIG.

In addition, the position of each subfield and the number of shots in the subfield can be obtained when converting CAD pattern data into EB format data without using hardware. In this case, if the data as shown in FIG. 3 is obtained from the chip layout information, the position of the subfield and the number of shots, the stage speed can be calculated. In this case, the number of shots in the subfield is
It is also possible to predict from the number of graphics in the subfield (the number of graphics before shot division) and the graphic area, and there is an advantage that the processing time for dividing graphics into shots can be reduced.

In addition, the configuration of the electron beam writing apparatus is not limited to what is shown in FIG. 1 and can be appropriately changed according to specifications. Further, the present invention is not limited to the electron beam writing apparatus, and can be applied to an ion beam writing apparatus. In addition, various modifications can be made without departing from the scope of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, in the charged beam writing apparatus of the continuous stage moving system, the optimum moving speed of the stage can be easily obtained without actually moving the stage, It is possible to improve the apparatus operation rate and the drawing throughput.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam writing apparatus used in the method of one embodiment of the present invention, FIG. 2 is a view showing an example in which a writing area is divided into small areas, and FIG. FIG. 4 shows the relationship between the position of each small area and the required drawing time when the maximum drawing time is determined. FIG. 5 shows the relationship between the drawing pattern and the required drawing time. FIG. 6 is a diagram showing a case where the deflection width is exceeded, and FIG. 6 is a diagram showing an example of evaluating the stage speed when a plurality of chips are arranged. 10 ... sample chamber, 11 ... sample, 12 ... sample stage, 20 ... electron optical system, 21 ... electron gun, 22 ... electron lens, 23-26 ... deflector, 27, 28 ... beam Molded aperture mask, 30 ... Calculator.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-248618 (JP, A) JP-A-2-5406 (JP, A) JP-A-1-243520 (JP, A) JP-A-1- 205421 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/027

Claims (4)

(57) [Claims] 1. A charged beam writing method for dividing a writing area on a sample into frames of a predetermined width and writing the frame while continuously moving a stage on which the sample is mounted, wherein Assuming that the stage was moved at a certain speed by dividing the stage into small regions with a fixed width in the continuous movement direction of the stage at intervals smaller than the beam deflection width, finding the required drawing time required for drawing for each of the divided small regions. The maximum drawing time M of the small area at this speed (the width of the small area / stage speed) is obtained, and the required drawing time A of the small area 1 is satisfied from the end of the frame until the maximum drawing time M is reached. The required drawing time (AM) is moved to the next small area 2 so that the maximum drawing time M
If the required drawing time B exists in the small area 2, a process of filling B after the necessary drawing time A is performed. The processing is performed in order until the end, and the maximum stage speed that does not exceed the maximum beam deflection width is determined based on whether or not the maximum distance in which the movement related to the required drawing time has occurred by the process exceeds the maximum beam deflection width. A charged beam drawing method characterized by being obtained. 2. A two-stage deflector as a deflector for deflecting the beam, the frame is divided into a plurality of subfields, the subfield is positioned by a main deflector, and the subdeflector is deflected by a subdeflector. 2. The charged beam drawing method according to claim 1, wherein drawing of a subfield is performed. 3. The drawing time required for drawing in the small area is determined based on position information of the subfield area and the total number of shots in the subfield area during non-drawing. The charged beam drawing method according to claim 2. 4. The drawing time required for drawing in the small area is determined based on the position information of the subfield area and the total number of shots in the subfield area when converting the pattern to be drawn. 3. The charged beam writing method according to claim 2, wherein: