JPS5828730B2 - Electron beam exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure apparatus that performs exposure while automatically correcting the exposure amount according to the size of a pattern.

Generally, when electron beam exposure is performed, a proximity effect occurs,
It is known that this has an adverse effect on the dimensional accuracy of the pattern.

For example, a case will now be described in which patterns such as those shown in FIGS. 1A and 1B are exposed.

Now assume that the electron beam pattern is a spot, and the pattern shown in a is exposed with, for example, 9 spots, and b
It is assumed that the pattern shown in 1 is exposed using, for example, 100 spots.

Usually, the exposure amount of one electron beam spot is expressed as follows.

i: Beam current t8: Scanning time (residence time) Area of S spot Even if the patterns shown in Figure 1 a and b are exposed with the same spot exposure amount, there will be overlap between spots and damage in the resist and substrate. The actual exposure amount per unit area varies depending on the area due to the scattering of electrons, etc.
Exposure as shown in b is performed.

FIG. 2 shows the case of a negative resist, where the solid line shows the actual exposure amount and the broken line shows the desired exposure amount.

As can be seen from the figure, if the area of the pattern to be exposed is small, that is, if the number of spots is small, the necessary exposure amount cannot be obtained, and if the area of the pattern to be exposed is dog, that is, if the number of spots is small, the number of spots cannot be obtained. If the number is large, the amount of exposure will be excessive.

Therefore, in the case of Figure 1a, ie, Figure 2a, only a pattern smaller than the required size is obtained, and in the case of Figure 1b, ie, Figure 2, the pattern is larger than the required size. I end up.

In any case, a highly accurate pattern cannot be obtained due to the proximity effect.

If the spot exposure amount is selected to be optimal in the case of Figure 1a, the exposure amount in the case of Figure 1A will be even more excessive, resulting in the formation of a pattern significantly larger than the desired size. , and conversely, if the exposure amount is selected to be optimal in the case of Figure 1A, the exposure amount in the case of Figure 1A will be even more insufficient and a pattern of the required size will not be formed, and in extreme cases. , the pattern itself cannot be formed.

In order to solve the above problem, the spot exposure amount may be appropriately changed and corrected according to the size of the pattern to be exposed.

In that case, it is almost impossible to change the spot exposure amount by changing the beam current i or the spot area S at high speed, so it is most practical to change the residence time t8 of the electron beam. It is.

The present invention automatically changes the residence time of the electron beam according to the size of the pattern to be exposed, controls the exposure amount to the pattern to be always appropriate, and produces a pattern with high dimensional accuracy regardless of the area. This will be explained in detail below.

FIG. 3 is a block diagram of essential parts showing an example of an apparatus for carrying out the present invention.

In the figure, 1 is the central processing unit (CPU), 2 is a register that stores data at position coordinate X1, and 3 is position coordinate Y1.
4 is a register that stores data on the magnitude coordinate X2, 5 is a register that stores data on magnitude coordinate Y2, 6 is a beam scanner, 7 is an X-direction deflection, a drive amplifier, and 8 is a register that stores data on a magnitude coordinate Y2. Y direction deflection, drive amplifier, 9
is an X direction deflection coil, 10 is a Y direction deflection coil, 11 is an electron beam, 12 is a target, 13 is a writing circuit, 1
4 and 15 are decoders, 16 is an nXn memory array,
17 is a readout circuit, 18 is a register, and 19 is a clock.
A pulse generation circuit and 20 represent a pulse conversion circuit, respectively.

A case in which exposure is performed using this apparatus will be explained.

In advance, electron beam residence time information is sent from the central processing unit 1 via the write circuit 13 to the memory array 16 and is stored there.

This information relates to the residence time of the electron beam corresponding to various combinations of size coordinates X2, Y2.

Now, information regarding the positional coordinates X1 and Yl of the pattern to be exposed is transmitted from the central processing unit 1 via the registers 2 and 3.
Further, information regarding size coordinates X2 and Y2 is provided to the beam scanner 6 via registers 4 and 5, respectively.

The beam scanner 6 uses the given information to
In the direction, the deflection coil 9 is driven via the amplifier 7, and in the Y direction, the deflection coil 10 is driven via the amplifier 8, and the electron beam 11 is deflected to scan a desired portion on the target 12. It plays a role in drawing patterns.

Registers 4 and 5 storing information regarding size coordinates X2 and Y2 send information to beam scanner 6 and at the same time to decoders 14 and 15.

Based on the information, the decoder 14.15 decodes the memory array 1
Specify address 6.

The information stored at that address is read out by the readout circuit 17, and the information, ie, the electron beam residence time information, is set in the register 18.

The information stored in register 18 is input to pulse conversion circuit 20.

The pulse conversion circuit 20 includes a clock pulse generation circuit 19.
Basic clock pulses are sent from

These elementary clock pulses are truncated in pulse conversion circuit 20 in response to information from register 18 and sent to beam scanner 6 as scanning pulses.

Since the beam scanner 6 performs electron beam scanning based on the scanning pulse, the residence time of the electron beam increases in proportion to the number of basic clock pulses that are thinned out.

As a result, the residence time of the electron beam at a predetermined position on the target 12, that is, the spot exposure amount can be changed automatically and at high speed in accordance with the size of the pattern to be exposed.

The information written and stored in the nXn memory array 16 in the device is given from the central processing unit 1 prior to the start of exposure as described above, and its contents are based on the size coordinates , Y2, and it is preferable to change them depending on factors such as the type of resist, its film thickness, and the difference in substrate.

Therefore, the larger the capacity of the memory array 16, the more detailed the correction can be made.

However, since there is a limit to how large the capacity of the memory array 16 can be, in that case, if the following procedure is performed, it is possible to perform a sufficiently promising correction even with a relatively small capacity.

That is, FIG. 4 is a three-dimensional diagram showing the relationship between the number of points exposed by the electron beam spot and the electron beam residence time t3. As can be seen from the figure, there are 10 points in both the X and Y directions. (The pattern width is 10 [μ7
71,1), the proximity effect becomes substantially constant, so the electron beam residence time can be made substantially constant.

That is, it becomes possible to set the correction value of the spot exposure amount to a certain constant value.

Therefore, as shown in FIG. 5, for example, a 16-bit central processing unit is used, and, for example, the size coordinate
When the memory array 16 is accessed by the decoder 14 regarding Y2 (the same applies to Y2), the upper 11 bits of the inputs of decoders 1400 to 15 are input to the OR circuit 14A.
The address Input A.

-A5 is 6 bits and memory array 16 is 64x6
4 with a small capacity will make do.

As can be seen from the above explanation, according to the present invention, a simple logic circuit device such as a small capacity memory is added to an electron beam exposure apparatus, and the residence time of the electron beam is adjusted according to the size of the pattern to be exposed. Since the exposure amount of the pattern can be controlled to be optimal by automatically changing the exposure amount of the pattern, it is possible to eliminate the decrease in the dimensional accuracy of the pattern due to the proximity effect of the electron beam.

Although the above embodiment has been described using a spot electron beam, the present invention is not limited thereto, and can of course be applied to cases where a fixed rectangular electron beam, a variable rectangular electron beam, etc. are used, for example.

However, in the case of a variable rectangular electron beam, the proximity effect can also be corrected by correcting the size of the pattern to be exposed, but rather than doing so, by applying the present invention, the beam By controlling the residence time, the profile of the exposure dose distribution becomes steeper and the base spreads less, so the desired pattern size can be stably formed against changes (fluctuations) in exposure and development conditions. In addition, it is advantageous because adjacent patterns can be resolved.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams and diagrams for explaining the decrease in dimensional accuracy of a pattern that occurs when electron beam exposure is performed, and FIG. 3 is a main part for explaining an example of an apparatus for carrying out the present invention. FIG. 4 is a block diagram showing the relationship between the exposure pattern size and the residence time of the electron beam, and FIG. 5 is a main part block diagram showing the relationship between the decoder and the memory array. In the figure, 1 is the central processing unit, 2 to 5 are registers, and 6 is the central processing unit.
is a beam scanner, 7 and 8 are amplifiers, 9 and 10 are deflection coils, 11 is an electron beam, 12 is a target, 13 is a write circuit, 14 and 15 are decoders, 16 is a memory array, 17 is a readout circuit, and 18 1 is a register, 19 is a pulse generation circuit, and 20 is a pulse conversion circuit.

Claims (1)

[Claims] 1 A register that stores information regarding position coordinates in the X direction and Y direction given from the central processing unit, a register that stores information regarding size coordinates in the X direction and Y direction, and electronic control based on information signals from these registers. a beam scanner for scanning the beam; a memory array for storing information regarding an electron beam residence time determined in accordance with the size of a pattern to be exposed; and accessing the memory array with an information signal regarding the size. An electron beam exposure apparatus comprising a clock pulse supply circuit for supplying the beam scanner with a clock pulse whose cycle is controlled in accordance with the obtained information signal regarding the residence time of the electron beam.