JP3461279B2 - Charged beam drawing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged beam drawing apparatus for drawing a fine pattern of a semiconductor integrated circuit or the like on a sample surface, and particularly to improve a deflection control circuit for deflecting a beam on the sample surface. Charged beam drawing apparatus.

[0002]

2. Description of the Related Art Conventionally, a drawing apparatus using an electron beam has been used as a means for drawing a desired resist pattern on a sample such as a semiconductor wafer. In this device, the deflection area (field) is determined by the characteristics of the deflector that deflects the beam.
Is defined, it is necessary to connect fields to draw a larger area. Then, in order to connect the deflection regions with high accuracy and draw a more accurate pattern, the sensitivity of the deflector, the deflection position distortion and the like are measured in advance and corrected.

However, this type of device has the following problems. That is, in the conventional electron beam drawing apparatus, when measuring the sensitivity and deflection position distortion of the deflector,
As shown in, the size of the calibration mark 21 and the area 24 for scanning the calibration mark 21 with the electron beam are taken into consideration, and the calibration area slightly narrower than the writable deflection area 20 (maximum drawing area). The measurement was performed at 23. The scanning position of the electron beam for detecting the calibration mark 21 is 22 in the figure, but a scanning region 24 necessary for rough measurement of the mark position is required. Therefore, in the peripheral portion of the maximum drawing area 20, the error is magnified because the deflection position is obtained by extrapolation,
There was a problem that the field connection accuracy deteriorates.

If the calibration area is made wider than the maximum drawing area in order to solve this problem, the deflection control circuit for driving and controlling the deflector needs to be controlled in an area wider than the actual maximum drawing area. This causes a reduction in drawing throughput. That is, although the deflection control circuit includes a deflection DAC and an amplifier, increasing the deflection region increases the number of input bits of the DAC, and increasing the number of input bits of the DAC leads to an increase in settling time.

[0005]

As described above, in the conventional electron beam drawing apparatus, when measuring the sensitivity and deflection position distortion of the deflector, if the measurement is performed in a calibration area slightly narrower than the maximum drawing area, There is a problem that the field connection accuracy deteriorates, and conversely, if the calibration area is wider than the maximum drawing area, there is a problem that the drawing throughput decreases.

The above problem is not limited to the electron beam drawing apparatus that draws a pattern by using an electron beam, but an ion beam drawing apparatus that draws a pattern by using an ion beam, and a pattern by using various charged beams. The same applies to the drawing device.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to reduce the beam position error even in the maximum drawing area without reducing the drawing throughput and to improve the field connection accuracy. It is an object of the present invention to provide a charged beam drawing apparatus capable of improving the above.

[0008]

[Means for Solving the Problems]

(Structure) In order to solve the above-mentioned subject, the present invention has adopted the following structures.

That is, the present invention is a charged beam drawing apparatus for selectively irradiating a surface of a sample with a charged beam to draw a desired pattern on the surface of the sample, and deflecting the charged beam to a desired position. In order to input the input data to the deflection DAC,
In a charged beam drawing apparatus having a deflection control circuit which performs A / A conversion and further amplifies it with an amplifier and gives it to a beam deflector,
The number of input bits used for adjusting the charged beam is used for writing to the deflection DAC in the deflection control circuit so that the deflection region used for adjusting the charged beam is larger than the deflection region used for writing with the charged beam. The feature is that the number of bits is larger than the number of input bits.

Preferred embodiments of the present invention are as follows. (1) Use an electron beam as the charged beam. (2) The deflection control circuit must be adjusted so that the deflection settling time is minimized by the number of input bits used for drawing in the deflection DAC or the maximum positive or negative voltage or maximum current.

(3) In the deflection DAC, the number of input bits used for adjusting the charged beam must be one bit or more larger than the number of input bits used for drawing. (Operation) According to the present invention, the deflection D in the deflection control circuit is
Since the number of input bits used for adjusting the charged beam is larger than the number of input bits used for drawing with respect to AC,
The deflection area used for adjusting the charged beam can be made larger than the deflection area used for writing. Therefore, even in the maximum drawing area, the beam position error can be reduced and the field connection accuracy can be sufficiently improved, and the drawing accuracy can be improved.

In this case, the deflection control circuit is set to the deflection D
In AC, by adjusting the number of input bits used for drawing to minimize the deflection settling time, that is, by adjusting the number of input bits used for drawing or the maximum positive or negative voltage or maximum current to obtain the fastest operation speed, There is no increase in throughput during drawing. Here, when adjusting the charged beam, the settling time is longer than that during drawing, and when the operation speed of the deflection control circuit is adjusted to the maximum by the number of input bits used for drawing as described above. The settling time is further increased when adjusting the charged beam. However, the frequency of beam adjustment is significantly less than the number of times of drawing, and the time required for beam adjustment is extremely short with respect to the time required for drawing. Therefore, the increase in beam adjustment time causes almost no problem.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the illustrated embodiments. (First Embodiment) FIG. 1 is a schematic block diagram showing an electron beam drawing apparatus used in the first embodiment of the present invention.

The electron beam 2 emitted from the electron gun 1 is
The light is deflected by the main deflector 3 and the sub-deflector 4, and is positioned and irradiated at a desired position on the sample 5 placed on the movable stage 6. Further, on the movable stage 6, a mark stand 7 to which a beam position measuring mark is attached is installed.

The control computer 10 converts the deflection data into the main deflection D
The data is transferred to the AC circuit 11 and the sub deflection DAC circuit 12, and the main deflection DAC circuit 11 and the sub deflection DAC circuit 12 output the deflection data as an analog signal. The main deflector 3 and the sub deflector 4 are driven by the main deflector amplifier circuit 13 and the sub deflector amplifier circuit 14 based on the outputs of the DAC circuits 11 and 12.

The main deflector 3 is used for positioning a relatively wide deflection area, and the sub deflector 4 is used for positioning a relatively narrow deflection area. The settling time of the deflection voltage is generally long when the deflection voltage is large, that is, when the deflection area is large.
As described above, the method of selectively using the deflector according to the size of the deflection area is often used.

In this embodiment, the number of bits of the drawing deflection DAC / amplifier circuit system (deflection control circuit) determined at the time of system design from the minimum address unit, the maximum deflection area, and the sensitivity of the deflector is used for calibration. The system has 1 bit added. Here, a case where the main deflection DAC circuit 11 has an address of 19 bits and the sub deflection DAC circuit 12 has an address of 14 bits will be specifically described.

The main deflection DAC circuit 11 uses only 18 bits at the time of drawing, and the sub deflection DAC circuit 12 uses only 13 bits. The main deflection DAC circuit 11 uses at the time of calibration of the electron beam for measuring deflection sensitivity and deflection position distortion. 19
The bit and sub-deflection DAC circuit 12 uses 14 bits.

Next, a specific calibration method will be described. Mark stand 7 fixed to the movable stage 6
2 are moved at equal intervals as shown in FIG. 2, the calibration mark 21 installed on the mark base 7 is scanned 22 with a beam each time to measure the mark position, and the ideal mark position measurement value is obtained. The deviation from the position is obtained and the deflection distortion and deflection sensitivity are measured. These deflection distortion and deflection sensitivity are
If the beam is largely deflected, the number of measurement points is increased, and fitting is performed by the least squares method, it is possible to perform accurate measurement.
Then, as shown in FIG.
Even a slight deflection distortion of the drawing area 20 smaller than 3 can be detected.

The number of used bits of the main deflection DAC circuit 11 and the sub deflection DAC circuit 12 is switched by the circuit configuration shown in FIG. 4 (a) or (b). In FIG. 4 (a),
The deflection area is limited so that the upper bits are not used at the time of drawing, and used properly during calibration.

In FIG. 4B, in addition to the restriction of the deflection area, the relay 17 is used for drawing / calibration for DAC / calibration.
Separately use the amplifier circuit. DAC / amplifier (1 bit or more) 13 ', 1 for controlling MSB data for large deflection
4 ′ is added, the outputs of the drawing DAC / amplifiers 13 and 14 are added by the adder 15, and the buffer amplifier 16 is added.
It is amplified by and applied to the deflectors 3 and 4.

In both cases of FIGS. 4A and 4B, the number of bits of the DAC used at the time of drawing and the operating speed of the DAC / amplifier circuit are adjusted to be optimum. The amplification degree and linearity of the deflection control circuit for the main deflection and the sub-deflection do not change during both drawing and calibration.

In the case of the above-mentioned structure, when the minimum address unit of the main deflection required for writing is 1 nm, the main deflection area for writing is 262.144 μm square. Further, the main deflection area at the time of calibration is 524.288 μm square. With this method, the minimum address unit is 1 nm at the time of drawing and at the time of calibration, so the same control accuracy can be maintained. Further, the operation speed of the deflection control circuit is adjusted so as to be the fastest in the number of bits used at the time of drawing, and thus the drawing throughput is not reduced.

Further, during calibration, the number of bits of the main deflection / deflection DAC circuit increases by 1 bit, the output of the amplifier circuit doubles, and the settling time increases exponentially. The high speed is not required and the minimum address unit is the same as that at the time of drawing, so that the calibration accuracy and the execution time are not deteriorated. The same effect can be obtained in the sub-deflection region.

As described above, according to the present embodiment, by adding 1 bit to the input of the DAC in the deflection control circuit determined at the time of system design, the deflection sensitivity and deflection position distortion in a wider range than the deflection area used for drawing. Since the measurement can be performed, the deflection position can be corrected by interpolation.
Therefore, the beam position error can be reduced in the maximum drawing area narrower than the calibration area, and the field connection accuracy can be improved. Moreover, in this case, the drawing throughput is not reduced by adjusting the deflection control circuit so that the operation speed becomes the fastest and the fastest with the number of input bits used for the drawing.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
FIG. 3 is a schematic configuration diagram showing a variable shaped electron beam writing apparatus for explaining the embodiment of FIG. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The electron beam 2 emitted from the electron gun 1 is
The first shaping aperture mask 51 is irradiated and shaped into a rectangle. The first shaping aperture image shaped in a rectangular shape is
The image is projected onto the second shaping aperture mask 52, shaped into a desired shape by the degree of overlap between the first shaping aperture image and the second shaping aperture opening, and projected onto the sample 5. Positioning of the electron beam on the second shaping aperture mask 52 is performed using the shaping deflector 53.

The control computer 10 transfers the shaping deflection data to the shaping deflection DAC circuit 54, and the shaping deflection DAC circuit 54 outputs the deflection data as an analog signal. Then, this signal is amplified by the shaping deflection amplifier circuit 55, and the shaping deflector 53 is driven by the amplifier 55.

Here, it is necessary that the orientation of the coordinate system of the second shaping aperture mask 52 and the orientation of the drawing coordinate system coincide with each other, and in order to calibrate the orientation of the second shaping aperture mask 52, the second shaping Aperture mask 52
As the mask, a mask having openings 60, 61, 62 as shown in FIG. 6 is used. In normal drawing, the electron beam is shaped into an arbitrary shape using the keyhole-shaped opening 60. The openings 61 and 62 are openings for adjusting the rotation of the aperture mask, and are rectangular openings smaller than the first shaping aperture image.

In order to make the coordinate system of the second shaping aperture mask 52 coincide with the drawing coordinate system, first, the first shaping aperture image is projected on the opening 61, and the mark on the sample is scanned with the transmitted electron beam to move the beam position. Ask for. Then the opening 6
The first shaping aperture image is projected onto the second beam, the beam position on the sample is obtained, and the second position is adjusted so that the coordinates of the two in the Y direction coincide with each other.
The shaping aperture mask 52 is mechanically rotated to calibrate its direction.

The drawing coordinate system generally coincides with the coordinate system of the movable stage 6. Further, when the electromagnetic lens is installed between the second shaping aperture mask 52 and the sample 5, the rotation of the coordinate system due to the rotation of the electron beam is also included.

In such a calibration method, the larger the distance between the openings 61 and 62 is,
The accuracy is improved. In the character projection type electron beam drawing apparatus, in order to select an opening provided in a wide area on the second shaping aperture mask, a selection deflector having a large deflection sensitivity is provided in advance, and the aperture mask described above is provided. A directional calibration method can be used. When the deflection sensitivity is high, it is difficult to control the deflection position at high speed and with high accuracy as compared with the case where the deflection sensitivity is low, but the character projection method has no problem because the beam is formed by the aperture of the aperture mask.

In the variable shaping type electron beam drawing apparatus, it is necessary to deflect the electron beam at a high speed to change the beam size, and only the shaping deflector having a relatively small deflection sensitivity is provided. Such a highly accurate calibration in the direction of the aperture mask cannot be performed, and only an accuracy of several mrad can be obtained. This is 10 μm
Which corresponds to a dimensional error of 10 nm for a beam of
It has a great influence on the drawing of fine patterns.

Therefore, even in an electron beam drawing apparatus having only a shaping deflector having a relatively small deflection sensitivity, the number of bits is larger than the address used for drawing in order to realize highly accurate calibration of the aperture mask rotation direction. A shaped deflection DAC circuit with addresses is used.
The circuit configuration is the same as that shown in FIGS. 4 (a) and 4 (b). Furthermore, the control method is the same as that described in the first embodiment. In the present embodiment, a case will be described in which the operation is performed at 13 bits at the time of drawing and the operation at 16 bits is performed at the time of aperture mask direction calibration.

In the case of the above configuration, when the shaping deflection address unit is 20 nm, the shaping deflection area at the time of drawing is 163 μm.
It becomes m square. In addition, the shaping deflection area at the time of calibrating the aperture mask direction is 1.3 mm square, and the rotation of the aperture mask is detected and calibrated with an accuracy of 0.1 mrad (corresponding to a dimensional error of 1 nm for a beam of 10 μm). Is possible. Therefore, the beam dimension control accuracy is improved, and highly accurate fine pattern writing is possible. Further, the operating speeds of the shaping deflection DAC circuit and the shaping deflection amplifier circuit are adjusted so as to be the highest in the number of bits used at the time of drawing, and thus the drawing throughput is not reduced.

Further, since the settling time of the deflection DAC circuit is slightly longer in the aperture mask direction calibration than in the drawing, the time required for the calibration is slower than that in the case where the number of bits used in the drawing is adjusted. There is no problem because the amount is negligible with respect to time.

(Other Examples) The present invention is not limited to the above embodiments. Although the electron beam writing apparatus has been described in the embodiment, the present invention is not limited to this, and the present invention can be applied to a charged beam writing apparatus such as an ion beam writing apparatus, and also to a writing apparatus that performs scanning with laser light or irradiation with light. . The number of bits used for the deflection DAC of the deflection control circuit can be appropriately selected according to the required minimum address unit, deflection area, and deflection sensitivity.

In the embodiment, the beam calibration area is made wider than the drawing area by adding 1 bit to the DAC / amplifier circuit system, but the method is not limited to this. For example, when the deflector is an electrostatic type, the deflection amount per unit voltage applied to the deflection electrode may be designed to be large in advance so that the deflection can be performed larger than the deflection area required for drawing. When the deflector is an electromagnetic type, the deflection amount per unit current applied to the deflection coil may be increased. Alternatively, the deflection area can be increased by increasing the output per bit of the deflection amplifier. Furthermore, when performing drawing, the area used for drawing may be limited so that it is smaller than the calibration area. In addition, various modifications can be made without departing from the scope of the present invention.

[0039]

As described above in detail, according to the present invention, the deflection DAC used in the deflection control circuit is set so that the deflection area used for adjusting the charged beam is larger than the deflection area used for writing by the charged beam. By increasing the number of input bits used for adjusting the charged beam to be larger than the number of input bits used for drawing, and adjusting the deflection control circuit so that the operating speed is the fastest and the fastest with the number of input bits used for drawing, It is possible to reduce the beam position error even in the maximum drawing area and improve the field connection accuracy without lowering the drawing throughput.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam drawing apparatus used in a first embodiment.

FIG. 2 is a schematic diagram for explaining a calibration method of a deflection position and a deflection sensitivity according to the first embodiment.

FIG. 3 is a diagram showing a relationship between a maximum drawing area and a beam calibration area in the first embodiment.

FIG. 4 is a block diagram showing a configuration of a deflection control circuit used in the first embodiment.

FIG. 5 is a schematic configuration diagram showing an electron beam drawing apparatus used in the second embodiment.

FIG. 6 is a plan view showing the configuration of a second shaping aperture used in the second embodiment.

FIG. 7 is a diagram showing a relationship between a maximum drawing area and a beam calibration area in a conventional electron beam drawing apparatus.

[Explanation of symbols]

1 ... electron gun 2 ... electron beam 3 ... Main deflector 4 ... Sub deflector 5 ... Sample 6 ... Movable stage 7 ... Mark stand 10 ... Control computer 11 ... Main deflection DAC 12 ... Sub-deflection DAC 13 ... Main deflection amplifier 14 ... Sub-deflection amplifier 15 ... Adder 16 ... Buffer amplifier 17 ... Relay 20 ... Deflection area used for drawing 21 ... Calibration mark 22 ... Electron beam 23 ... Calibration area 24 ... Deflection area required for mark measurement 51 ... First molding aperture mask 52 ... Second shaping aperture mask 53 ... Molding deflector 54 ... Molding deflection DAC circuit 55 ... Molding deflection amplifier circuit

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-1-236565 (JP, A) JP-A-2-7512 (JP, A) JP-A-8-335547 (JP, A) JP-A-53- 67365 (JP, A) JP 60-126827 (JP, A) JP 63-20829 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 H01J 37 / 147

Claims (3)

(57) [Claims] 1. A charged beam drawing apparatus for selectively irradiating a surface of a sample with a charged beam to draw a desired pattern on the surface of the sample, wherein the charged beam is deflected to a desired position. In a charged beam drawing apparatus having a deflection control circuit that D / A-converts input data with a deflection DAC and further amplifies it with an amplifier to give it to a beam deflector, the deflection area used for adjusting the charged beam is used for writing with the charged beam. Charged beam drawing, wherein the number of input bits used for adjusting the charged beam is larger than the number of input bits used for drawing for the deflection DAC in the deflection control circuit so as to be larger than the deflection area. apparatus. 2. The deflection control circuit is adjusted so that the deflection settling time is minimized by the number of input bits, maximum voltage, or maximum current used for drawing in the deflection DAC. 1. The charged beam drawing apparatus according to 1. 3. The deflection DAC according to claim 1, wherein the number of input bits used for adjusting the charged beam is 1 bit or more larger than the number of input bits used for drawing.
1. The charged beam drawing apparatus according to 1 or 2 .