JPH02177416A - Exposure controller - Google Patents

Abstract

PURPOSE:In an exposure device which repeats exposure and nonexposure, to enable accurate light quantity measurement so as to control exposure highly accurately by providing a means, which changes over input signals to an exposure measuring means, and a pseudosignal generating means so as to make the exposure measuring means keep almost the same condition both at exposure and at nonexposure. CONSTITUTION:In an exposure controller which is equipped with the exposure measuring means 3 to measure the light quantity of pulse-form exposure light emitted by a light source, and which controls the exposure of the light source 1 based on the output of the exposure measuring means 3, a means which changes over input signals to the exposure measuring means 3 and a pseudosignal generating means 4 which outputs pseudosignals, are equipped, and the change-over means 5 inputs the output signals of the pseudosignal generating means 4 into the exposure measuring means 3 at the time of nonexposure so that the exposure measuring means 3 may keep the almost same conditions both at exposure and at nonexposure. For example, said pseudosignal generating means 4 issues both or one of pseudosignals, a light quantity signal, which is a target of measurement of the exposure measuring means 3, and measurement command signal per pulse.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exposure amount control device in semiconductor manufacturing equipment such as an aligner or an etching device, and particularly relates to a light source that emits pulsed light or a light source that emits intermittent continuous light. The present invention relates to an exposure amount control device that aims to control the exposure amount with high precision when using a light source.

[Prior Art] Conventionally, in semiconductor manufacturing equipment such as aligners and etching equipment, the following two types of exposure control methods have been used to accurately measure pulsed light, for example, excimer laser light, and control the exposure amount. One device that has been proposed is one that sends a measurement command signal to an exposure meter every time pulsed light is emitted, measures the photoelectrically converted light amount signal, and controls the exposure amount. The other method is to repeat short measurements at different times, and when a pulsed light intensity signal is detected, obtain the measured value and control the exposure amount.

[Problems to be Solved by the Invention] However, in such conventional exposure amount control devices, no particular consideration was given to the fact that the exposure device repeatedly performs exposure/non-exposure cycles. Therefore, the situation of the exposure meter is different between when it is measuring the light amount signal during exposure and when it is not measuring after -th exposure and until the next exposure. Become.

On the other hand, this exposure meter, which measures pulsed light, needs to accurately measure pulse signals having components in a high frequency band on the order of IGHz. For example, excimer laser light emission has a repetition frequency of 100Hz and a light emission time of 10
It has a very sharp peak at nsec. Exposure metering devices are designed to be extremely sensitive so that they can sufficiently respond to these signals and make highly accurate measurements.

Therefore, due to changes in the environment such as during exposure and non-exposure, for example due to electrical offset fluctuations in the measurement system, the light amount measurement accuracy decreases.

FIG. 4 shows how the accuracy deteriorates. Here, we show the results of measuring the exposure amount using an exposure meter when emitting the same amount of pulsed light at a constant pulse frequency and repeating the emission intermittently in cycles of exposure and non-exposure. . As you can see from the figure, since the same amount of light was continuously measured, the exposure measurement value should be constant, but if you start the exposure after stopping the exposure for a certain amount of time, the exposure measurement value will start to change. The value is inaccurate, indicating the characteristic that the measured value will not stabilize unless pulsed light is continuously measured for a while.

As described above, there is a problem in that a rising characteristic occurs in exposure measurement from immediately after the start of exposure until it stabilizes, and the exposure cannot be controlled with high precision during this period.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an exposure amount measuring means for measuring the amount of pulsed exposure light emitted by a light source,
An exposure control device for controlling the exposure of a light source based on the output of the exposure measurement means, comprising a switching means for switching an input signal to the exposure measurement means, and a pseudo signal generation means, the exposure measurement means The switching means inputs the signal from the pseudo signal generating means to the exposure amount measuring means during non-exposure so that the signal remains substantially the same during exposure and during non-exposure.

The pseudo signal generating means generates, for example, a pseudo signal of both or one of the light amount signal to be measured by the exposure amount measuring means and the measurement command signal for each pulse.

Alternatively, a programmable pseudo signal generating means may be used, and the generated signal may be substantially the same as the signal input to the exposure amount measuring means during exposure.

[Function] In this configuration, the exposure measurement means measures and integrates the exposure based on the charged and converted pulsed light signal, and controls the exposure such as stopping the exposure operation of the light source when the integrated value exceeds a certain value. However, even during non-exposure when pulsed light emission is not performed, the pseudo light amount signal etc. is input to the exposure amount measuring means, so the exposure amount measuring means always maintains the state at the time of exposure, and during actual exposure. , accurate measurements are always performed without causing inaccuracies in measurement values at the start of exposure.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram showing the configuration of an exposure control device according to an embodiment of the present invention. In the figure, 1 is an excimer laser used as a pulsed light source, 2 is a photodiode that converts the intensity of light output from the excimer laser into an electrical signal,
A photoelectric converter such as a phototube, 3 an exposure meter that measures the exposure amount by integrating the photoelectrically converted signal, and 4 an exposure device such as a signal obtained by photoelectrically converting pulsed light and a light emission synchronization signal that serves as a measurement command signal for each pulse. A pseudo signal generator 5 generates a signal equivalent to the actual input signal to the exposure amount measuring device 3; 5 is a switch for switching between the signal from the pseudo signal generator 4 and the actual signal and inputting the signal to the exposure amount measuring device 3; A two-linked changeover switch used as a means, 6 is an exposure meter 3
A controller 7 controls the exposure amount by monitoring the exposure amount obtained by the excimer laser 1, commanding the excimer laser 1 to emit light or stop emitting light, etc., and issuing switching selection commands to the changeover switch 5. It is a half mirror that takes out a certain percentage and guides it to the photoelectric converter 2.

FIG. 2 is an overall view showing how this exposure control device is applied to a stepper, and 1 to 7 are as explained in FIG. 1.

8 is a reticle on which a circuit pattern is enlarged several times on a quartz plate, 9 is a reticle stage on which the reticle 8 is placed, 10 is a projection lens for projecting the pattern of the reticle 8 in a reduced size, and 11 is a projection lens. 10 is a wafer onto which the pattern of the reticle 8 is projected; 12 is a wafer 11;
An XY stage that moves horizontally in XY to the exposure position with
13 is a wafer supply hand that supplies the wafer 11 onto the XY stage 12, and 14 is a collection hand that collects the wafer 11 from the XY stage 12.

FIG. 3 shows a flow chart of the operation of the stepper of FIG. 2 in an exposure cycle.

Hereinafter, this embodiment will be explained in detail using FIGS. 1 to 3.

Here, the present invention is applied to an exposure apparatus called a stepper, particularly a stepper using an excimer laser as a light source. It is. The operation of the stepper is shown in FIG. 3, and will be explained in order below.

When the stepper printing sequence starts, first, in step Sl, the reticle 8 is carried onto the reticle stage 9. Then, in step S2, the wafer 11 is
It is carried onto the Y stage 12.

In step S3, the XY stage 12 is moved and the wafer 11 is set at a preset exposure shot position.

Next, the process proceeds to step S4, where exposure is performed.

Next, in step S5, it is checked whether exposure for all shots on one wafer has been completed. If the process is completed, the process proceeds to step S6; if not, the process proceeds to step S3 to perform exposure for the next shot.

Next, in step S6, the upper wafer is carried out onto the XY stage.

In step S7, it is checked whether all the wafers to be exposed have been processed. If the process has been completed, the exposure sequence is completed; if not, the process advances to step S2 to expose the next wafer.

The projection exposure cycle is repeated in this manner, but
An excimer laser 1 that emits pulsed light is used as a light source for this reduction projection, and for optimal exposure control, the energy of this pulsed light must be accurately measured for each pulse. It is necessary to control the exposure amount.

In order to achieve this objective, in this embodiment, the exposure control device is configured as shown in FIG. 1, and a changeover switch 5 is provided to switch the input signal to the exposure measurement device 3, so that a pseudo signal is generated during non-exposure. The light amount pseudo signal e generated by the device 4 and the measurement command pseudo signal f for each pulse are input to the exposure amount measuring device 3 so that the exposure amount measuring device 3 maintains approximately the same state both during exposure and non-exposure. The exposure amount of pulsed light is controlled with high precision.

Details of this operation are shown below.

Step S4 of projecting the pattern on the reticle onto the square
During actual exposure, first, before performing exposure, a switching command is output from the controller 6, and the changeover switch 5 is switched to the A side. By switching to the A side, the light emission synchronization signal d output from the excimer laser 1 and the light amount signal C obtained by extracting a part of the excimer laser light and converting it by the photoelectric converter 2 are input to the exposure amount measuring device 3. be done. Thereafter, a light emission command a is issued to the excimer laser 1 to start exposure. Immediately before the excimer laser 1 emits light, it outputs a light emission synchronization signal d, and this signal is inputted to the exposure dose measuring device 3 through the changeover switch 5 as a measurement command signal. In response to this command, the exposure amount measuring device 3 measures the actual light amount signal C of the excimer laser light for each pulse. The controller 6 monitors the measurement value signal g during exposure, and stops the excimer laser light emission when the exposure amount reaches the target value.
One exposure is considered to be the end.

Here, at the end of step S4, a mechanism is activated to prevent the exposure meter 3 from stopping until the next exposure is started. That is, the controller 6 switches the changeover switch 5 to the B side in preparation for the non-exposure time. Then, the signals e and f generated by the pseudo signal generator 4 are input to the exposure meter 3. The signals e and f are set in advance to be equivalent to the light amount signal C1 and the light emission synchronization signal d, respectively.

During non-exposure periods other than step S4, the exposure meter 3 always continues measurement by the last procedure of step S4, and the state is maintained almost the same during both exposure and non-exposure times.

When the next exposure is performed, there is no change in the state of the exposure dose meter 3, so accurate measurement is performed and the exposure dose is controlled with high precision.

In the above description, both the light intensity signal C and the light emission synchronization signal d, which is a measurement command signal, are switched, but the exposure measurement device uses the rising edge of the light intensity signal C as a measurement command and does not require a separate measurement command signal. When using this, it is sufficient to switch only the light amount signal C, and of course there is no need for a pseudo signal of the measurement command signal.

In addition, if the exposure meter 3 has a characteristic that if only the measurement command signal is input continuously, stable and accurate measurements can be made without inputting the light intensity signal, it may be considered a pseudo signal of the light intensity signal. The signal switching mechanism may be omitted.

Furthermore, although the switching signal is issued by the controller 6, the exposure control device automatically detects that no measurement has been made for a certain period of time and issues a pseudo signal switching command. You may also configure

Further, the pseudo signal generator 4 is set in advance to generate a signal similar to the actual signal, and is used fixedly thereafter, but this signal is made programmable and the controller 6
It is also possible to implement a configuration in which a setting command is issued from.

Here, by detecting the actual light intensity signal or measurement command signal at a certain period such as every pulse, every shot, or every few days, and outputting a setting command from the controller so that the pseudo signal is the same as that, During exposure, it is possible to keep the exposure meter in a state that more closely resembles the actual exposure.

[Effects of the Invention] As explained above, by using the exposure amount control device of the present invention, it is possible to accurately measure the light amount and control the exposure amount with high precision in an exposure device that repeats exposure and non-exposure. Become.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment that best represents the present invention, FIG. 2 is an overall view of a stepper to which the present invention is applied, FIG. 3 is a flowchart showing the operation of the stepper, and FIG. FIG. 4 is a characteristic diagram of a conventional exposure meter. 1: Excimer laser, 2: Photoelectric converter, 3: Exposure meter, 4: Pseudo signal generator, 5: Changeover switch, 6:
Controller, : 8-view mirror, 8 reticle, Ni reticle stage, 10: Projection lens, 27 XY stage, 3: Wafer supply hand, 4: Collection hand to sea urchin, : Light emission command signal, b; Switching command signal, : Light amount signal,
d: Light emission synchronization signal, : Light amount pseudo signal, f: Measurement command pseudo signal, : Measured value signal. Patent applicant agent Canon Co., Ltd.

Claims (3)

[Claims] (1) In an exposure amount control device comprising an exposure amount measuring means for measuring the amount of pulsed exposure light emitted by a light source and controlling the exposure amount of the light source based on the output of the exposure amount measuring means, the exposure amount measuring means and a pseudo signal generating means for outputting a pseudo signal. An exposure amount control device characterized in that an output signal of the pseudo signal generating means is inputted to the exposure amount measuring means. (2) The exposure amount according to claim 1, wherein the pseudo signal generating means generates a pseudo signal of both or one of a light amount signal to be measured by the exposure amount measuring means and a measurement command signal for each pulse. Control device. (3) the pseudo signal generating means is programmable;
3. The exposure amount control device according to claim 1, wherein the generated signal is substantially the same as a signal inputted to said exposure amount measuring means during exposure.