JPS6134252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an exposure amount control device, particularly for controlling the exposure amount of a printing device used to print circuit patterns on a mask onto a semiconductor wafer in the manufacturing process of ICs, LSIs, etc. The present invention relates to a suitable exposure control device.

Generally, this type of exposure control device has a shutter that opens and closes to pass and block light from the light source of the printing device to the masks and wafers, and a light amount detector to detect the exposure amount of the wafer. The amount of exposure is controlled by opening and closing the shutter based on the detection results of the photoelectric detector. In this type of exposure control device, it is necessary to correct overexposure caused by a delay in shutter operation, that is, a time delay from when a shutter close command signal is generated until the shutter is completely closed. For this reason, in the past, a method has been adopted in which the exposure amount is set to be a certain amount of light less than the appropriate exposure amount of the wafer, and the shutter close command signal is generated earlier than the original exposure time. However, this method is based on the premise that the amount of overexposure is always constant relative to the shutter operation delay time, so if the intensity of the light from the light source of the printing device changes, the amount of overexposure will always be constant compared to the shutter operation delay time. There was an inconvenience that it was not possible to correct overexposure. Normally, in a semiconductor printing apparatus, the light source is used even if the intensity of the light source is reduced to about half of its maximum value, so this method causes the problem of overexposure or underexposure.

Problems with such conventional devices will be explained in detail using illustrated examples. FIG. 1 is a block diagram showing an example of a conventional exposure amount control device, and shows an example applied to a semiconductor printing device. In the figure, 1 is a light source, 2
1 is a mask illuminated by the lamp 1, on which a semiconductor circuit pattern is formed. A wafer 3 is placed close to the mask 2, and the circuit pattern on the mask 2 is printed onto its upper surface by light from the light source 1. 4 is a shutter that blocks the illumination light from the light source, 5 is a light sensor that detects the intensity of the light that has passed through the shutter 4, and the light intensity detected by this light sensor 5 is converted into a voltage signal by an amplifier 6. converted. 7 is a V/F converter that converts a voltage signal into a frequency signal, 8 is a total counter that counts the number of pulses from the V/F converter 7, and 9 is a value counted by the total counter 8 and an exposure amount setting device 10. This is a comparison circuit that compares the values set in , and issues a match signal when these values match. Reference numeral 11 denotes a shutter opening/closing command device, which generates a shutter opening command signal by pressing an exposure start command button, etc., activates the shutter drive circuit 12, causes the shutter 4 to open, and instructs the total counter 8 to start counting. do. Further, based on the coincidence signal from the comparator circuit 9, a shutter closing finger cooling signal is generated, the operation of the shutter drive circuit 12 is stopped, and the shutter 4 is caused to operate in a closing operation.

In this example, in order to correct overexposure due to a delay in the operation of the shutter 4, the exposure amount setter 10 is set to a value obtained by subtracting a certain number of pulses from the number of pulses corresponding to the actual exposure amount. For this reason,
As described above, excess or deficiency in the amount of exposure occurs based on fluctuations in the brightness of the light source 1. . This will be explained using a significantly simplified model.

Figures 2a and b show the shutter operation time charts when the brightness of light source 1 is at its maximum and at 1/2 of its maximum brightness.High level indicates the shutter is open, and low level indicates the shutter is closed. show.
As shown in Figure 2a, when the brightness of light source 1 is the highest,
After the shutter 4 performs an opening operation at time _t1 , the total counter 8 counts the pulse signals from the V/F converter 7 up to the value set in the exposure amount setting device 10, and the shutter opening/closing command device 11 outputs the shutter signal. The time until the closing command signal is issued is until time _t2 . Then, the closing operation of the shutter 4 is completed during a certain period of time _t2 to _t3 . Therefore, the shutter open time is from _t1 to _t3 . Figure 2b
In this case, since the brightness of the light source 1 has been halved, the opening time of the shutter 4 from t ₁ to t ₆ must be twice as long as from t ₁ to t ₃ . However, even in this case, the shutter ₄ closes from the time t 4 when the shutter close command signal is generated after the total counter 8 has counted a certain number of pulses (the times t ₁ to t ₄ are twice the times t ₁ to t ₂ ). Since the time up to this point is the same as time t ₂ to _{t 3} in FIG. 2a, it closes before time t ₆ . Therefore,
The shutter opening time is from t ₁ to t, and then from t ₅ to _{t 6}
There will be a lack of light.

The present invention was developed in view of the above circumstances, and its purpose is to control the exposure amount of a recording medium by means of a shutter that is opened and closed to pass and block light from a light source to a recording medium. An object of the present invention is to provide an exposure amount control device that can always expose a recording medium by an accurately set amount even if the brightness of a light source changes.

And, in order to achieve this purpose, the present invention
The amount of exposure commensurate with the delay in shutter operation is detected via a photoelectric detector that detects light from a light source, and the timing of generation of the shutter close command signal is corrected based on the detected amount of exposure.

Hereinafter, the present invention will be explained in detail based on each embodiment shown in FIG. omitted. In the embodiment shown in FIG. 3, 13 is a correction timer, 14 is a correction counter, and 15 is a two-input AND gate, which constitute the light amount detection means of the present invention. The correction timer 13 starts operating by the operation of the V/F converter, and generates an output for a time period _t2 to _t3 corresponding to the delay in the operation of the shutter 4. The correction timer 13 is connected to one input terminal of the AND gate 15. Further, the output of the V/F converter 7 is applied to the other input terminal of the AND gate 15. Therefore, the correction counter 14 counts the number of pulses corresponding to the operation delay time _t2 to _t3 of the shutter 4. Reference numeral 16 denotes an adder serving as a correction means of the present invention that adds the count values of the total counter 8 and the correction counter 14;
The comparison circuit 9 compares the added value of 6 and the value set in the exposure amount setter 10. In this embodiment, the setting value of the exposure amount setting device 10 is different from the example shown in FIG. 1, and an appropriate exposure value is set. Other points are the same as the example shown in FIG.

Since this embodiment is configured as described above,
As shown in Figure 4 a and b, even at the highest brightness,
Even in the case of 1/2 brightness, the shutter close command signal is set so that the appropriate exposure times t ₁ to t ₃ and t ₁ to t ₆ can be obtained, that is, the shutter close command signal is delayed by an amount corresponding to the overexposure caused by the delay in shutter 4 operation. The actual exposure amount is always equal to the exposure amount set in the setting device 10 because it is generated at the time t ₂ to _{t 4} when exposure occurs.

Next, another embodiment of the present invention in which the count value of the correction counter 14 is input to the exposure amount setter 10 will be described with reference to FIG.

Similar to the embodiment of FIG. 3, the correction timer 13
outputs an output to the AND gate 15 for a time corresponding to the operation delay time of the shutter 4 from the start of operation of the V/F converter 7. During this time, the AND gate 15 outputs a pulse signal corresponding to the intensity of the light from the light source 1 that is incident on the optical sensor 5. The number of pulse signals is counted by the correction counter 14, and this count value is input to the exposure amount setting device 10. The number of pulses corresponding to the appropriate exposure amount is set in the exposure amount setter 10, and this set number of pulses is subtracted by the count value of the correction counter 14. Therefore, the comparison circuit 9 compares the subtracted set value and the count value of the total counter 8. Since the following is the same as the embodiment shown in FIG. 3, the explanation will be omitted.

Next, still another embodiment of the present invention using a microcomputer will be described with reference to FIG. The difference from the embodiment shown in FIG. 3 is that the comparator circuit 9, shutter opening/closing command device 11, AND gate 15, and adder 16 perform commands or calculations using the CUP, and the total counter 8 and correction counter 14 are used randomly.・Access memory RAM1 is used, and the oscillator OSC and RAM2 are used as the correction timer 13.
The point is that it uses . In order to have the same functions as the embodiment shown in FIG. 3, the main routine shown in FIG. 7a and the interrupt routine shown in FIG. 7b are provided. Exposure control usually operates on the main side, and when an interrupt occurs, the main routine is temporarily suspended, the interrupt routine is jumped to, and the interrupt processing is determined and processed. When this is completed, the exposure amount control is completed while repeating the operation of returning to the main routine again. In FIG. 6, the output of the V/F converter 7 and the output of the OSC 13 are used for interrupts.

Next, FIGS. 7a and 7b will be explained. When entering the main routine, first clear the RAM1 that counts the output pulses of the V/F converter 7 (step 1-1), then open the shutter 4 (step 1-2), and the V/F converter 7 will operate. (Step 1-3). The operation of the V/F converter 7 is detected by interrupt processing (steps 2-1 and 2) using the output of the V/F converter 7.
This is done when RAM1 is no longer 0. When the V/F converter 7 starts operating, set the shutter 4 operation delay time in RAM2 (step 1).
-4), create a loop until RAM2=0 (steps 1-5). RAM2 is decremented by interrupt processing by the output pulse of OSC13 (steps 2-3, 4, and 5). From the time RAM2 is set until it becomes 0, the V/
The number of output pulses of the F converter 7 is also counted in the RAM 1 by interrupt processing. When RAM2 is detected as 0, the value of RAM1 is doubled (step 1-6). This is the example of FIG.
This function is equivalent to adding the value of the correction counter 14 and the value of the total counter 8 while the correction timer 13 is operating.

After correction, RAM2 is set to V/F in the interrupt routine.
It is incremented according to the output of converter 7. In the main routine, input the exposure setting value,
The shutter drive circuit 12 sends a match signal to close the shutter 4 when the value is the same compared to PAM1.
(Steps 1-7, 8, 9). The following operations are similar to those of the previous embodiment, so the explanation will be omitted.

As described above, the present invention provides an exposure amount that is commensurate with the shutter operation delay when controlling exposure to a recording medium using a shutter that is opened and closed to pass and block light from a light source to a recording medium. Since the timing of generating the shutter close command signal is corrected based on the detected exposure amount, the recording medium can always be exposed by the set amount even if the light source brightness changes. Therefore, according to the present invention:
The exposure of the printing device can always be accurate.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an example of a conventional exposure amount control device, FIGS. 2a and b are diagrams showing a time chart of shutter operation in the example of FIG. 1, and FIG. 3 is an exposure amount control system according to the present invention. 4a and 4b are diagrams showing a time chart of shutter operation in the embodiment of FIG. 3; FIG. 5 is a block diagram showing another embodiment of the present invention; FIG. FIG. 6 is a block circuit diagram showing still another embodiment of the present invention;
7a and 7b show the operating routine of the embodiment of FIG. 6, FIG. 7a shows the main routine, and FIG. 7b shows the interrupt routine. In the figure, 1 is a light source, 2 is a mask, 3 is a wafer,
4 is the shutter, 5 is the light sensor, 6 is the amplifier,
7 is a V/F converter, 8 is a total counter, 9 is a comparison circuit, 10 is an exposure amount setting device, 11 is a shutter opening/closing command device, 12 is a shutter drive circuit, 13 is a correction timer, 14 is a correction counter, 15 is an and gate.

Claims (1)

[Scope of Claims] 1. A shutter that is opened and closed to pass and block light from a light source to a recording medium, and in response to the generation of a shutter open command signal, the shutter is caused to open and the shutter open command signal is generated. a shutter driving means for causing the shutter to close in response to the shutter, a light detecting means for detecting light from the light source, and a shutter driving means for causing the shutter to close in accordance with the shutter closing operation; and a light detecting means for detecting light from the light source; a light amount detecting means for detecting a light amount corresponding to the amount of light from the light source passing through the shutter in between, based on a detection result of the light detecting means before the shutter close command signal is generated; The timing of generation of the shutter close command signal is adjusted to match the set light amount with the amount of light from the light source that passes through the shutter from the time the shutter open command signal is generated until the shutter close operation is completed. An exposure amount control device comprising a correction means for correcting a value corresponding to the amount of light detected by the light amount detection means. 2. The light detecting means detects light from the light source passing through the shutter, and the light amount detecting means detects the light from the shutter closing command signal generated during the shutter opening operation until the shutter closing operation is completed. 2. The exposure amount control device according to claim 1, wherein the detection results of the light detection means are integrated only during a period of time corresponding to the time. 3. Claim 1, wherein the correction means adds the amount of light detected by the light amount detection means to the amount of light from the light source that passes through the shutter after the shutter open command signal is generated. The exposure amount control device described. 4. The exposure amount control device according to claim 1, wherein the correction means subtracts the amount of light detected by the amount of light detection means from the amount of light set for the recording medium. 5. The exposure amount control device according to claim 1, wherein the detection means includes a voltage frequency converter for converting the detection result into a pulse signal.