JPS63317729A - Integrating exposure meter - Google Patents

Abstract

PURPOSE:To facilitate measurement and to improve measuring accuracy, by forming a pulse signal having a specified width with a voltage which is proportional to the peak value of a detected light signal, sequentially integrating the pulse signals, and obtaining the output which is proportional to the amount of exposure. CONSTITUTION:The detected signal from a photodetector 10 is supplied to a pulse signal generating circuit 20. The pulse signal generating circuit 20 generates a pulse signal having a specified width at a voltage, which is proportional to the peak value of the detected signal. The pulse signal is supplied to an integrator 30. The integrator 30 comprises, e.g., a Miller integrator circuit. The integral output is supplied to a comparator 40. The comparator 40 compares the integral output with a reference level. When the integral output is larger than the reference level, an 'H' signal is outputted. With the 'H' signal, exposure with a pattern exposure device is finished.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an integrating exposure meter that measures the exposure amount in a pattern exposure apparatus using a pulsed light source. The present invention relates to an integrating exposure meter that determines the exposure amount by 71FJ based on a peak value.

(Prior Art) In recent years, exposure apparatuses have been developed that utilize pulsed light sources such as excimer lasers to expose desired patterns onto semiconductor wafers. In this apparatus, in order to give the wafer the optimum amount of exposure, the output of the light source is kept constant and the irradiation is applied for a certain period of time. However, the output light intensity of a light source such as an excimer laser changes depending on its usage conditions, aging force, and other factors. Therefore, it is necessary to monitor the intensity of the light emitted from the light source in order to provide the optimum exposure amount.

Conventionally, this type of monitoring means includes a photodetector that detects light from a light source, displays a detection signal from the photodetector with a synchroscope, and measures its peak value at arbitrary time intervals. Then, the level of each peak value is multiplied by the number of laser oscillations, and the total exposure amount is determined from the cumulative total.

However, this type of method has the following problems. That is, the operator performs all measurements manually and also controls the exposure amount at the same time, resulting in very poor work efficiency. Furthermore, since the detection signal of the photodetector is displayed on a synchroscope for peak detection,
Peak detection error is large. For this reason, it has been difficult to accurately measure the exposure amount, and it has been extremely difficult to provide the optimum exposure amount to the wafer.

(Problems to be Solved by the Invention) Conventionally, it has been difficult to accurately measure the amount of exposure using a pulsed light source, and it has been difficult to perform optimal exposure in an exposure apparatus using a pulsed light source.

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to accurately measure the exposure amount by a pulsed light source, and to enable optimization of the exposure amount in an exposure apparatus using a pulsed light source. The purpose of the present invention is to provide an integrating exposure meter that can contribute to the present invention.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to generate a pulse signal with a constant width and a voltage proportional to the peak value of pulsed light, and to sequentially add and integrate the signals. The purpose is to find the amount of exposure.

That is, the present invention provides an integrating exposure meter that determines the exposure amount of light emitted from a pulsed light source and irradiated onto a sample by 11P1.
a photodetector that detects light emitted from the pulsed light source; a pulse signal generation circuit that generates a pulse signal of a constant width with a voltage proportional to a peak value of a detection signal of the photodetector;
An integrator is provided to integrate the pulse signal generated by the pulse signal generating circuit, and the exposure amount is determined from the integrated output of the integrator.

(Function) According to the present invention, a signal proportional to the actual exposure amount can be obtained by integrating a pulse signal with a constant width of voltage proportional to the peak value of pulsed light. This is because the amount of exposure by pulsed light is proportional to the peak value of pulsed light. Therefore, the exposure amount can be accurately measured from this signal (integrated output). In addition, by comparing the integrated output with a predetermined level and stopping the pulsed light source when it exceeds the level, exposure equipment that uses a pulsed light source can automatically determine the end of exposure, and optimize the output for the wafer. It becomes possible to give a certain amount of exposure.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a block diagram showing a schematic configuration of an integrating exposure meter according to an embodiment of the present invention. Note that this integrating exposure meter is used in a pattern exposure apparatus to be described later.

In the figure, 10 is a photodetector consisting of a photoelectric conversion element such as a photodiode or a phototransistor, and this photodetector 1
At 0, a part of light emitted from a pulsed light source, which will be described later, is received. A detection signal from the photodetector 10 is supplied to a pulse signal generation circuit 20.

The pulse signal generating circuit 20 generates a pulse signal having a constant width and a voltage proportional to the peak value of the detection signal, and this pulse signal is supplied to the integrator 30. The integrator 30 is composed of, for example, a Miller integration circuit, and its integrated output is supplied to a comparator 40. The comparator 40 compares the integrated output with a reference level, and outputs an 'H' signal when the integrated output is greater than the reference level. ”, the exposure by the pattern exposure device described later is completed.

FIG. 2 is a block diagram showing a specific configuration of the pulse signal generation circuit 20, and this pulse signal generation circuit 20 includes:
Comparator 21. Delay circuit 22. Reference pulse generator 23. Integrator 241 Multiplier 25. It is composed of a peak hold circuit 26, a reset pulse generator 27, and the like. The detection signal of the photodetector 10 is supplied to a comparator 21 and a peak hold circuit 26. The comparator 21 compares the detection signal with a predetermined level and binarizes the signal, and the output signal is sent to the reference pulse generator 2 via the delay circuit 22.
3. The reference pulse generator 23 generates a reference pulse of a constant width based on the rise of the delayed output, and this reference pulse is supplied to the integrator 24 and the reset pulse generator 27. The integrator 24 integrates the reference pulse and shapes the rise and fall of the pulse into a gentle waveform, and this shaped signal is supplied to the multiplier 25. The peak hold circuit 26 holds the peak value of the detection signal, and the hold signal is supplied to the multiplier 25. The multiplier 25 multiplies the shaped signal and the hold signal, and this multiplied signal is supplied to the integrator 30 as the output of the pulse signal generation circuit 20. Further, the reset pulse generator 27 generates a reset pulse at the falling edge of the reference pulse, and uses this reset pulse to reset the peak hold circuit 26.

FIG. 3 is a schematic diagram showing a schematic configuration of a pattern exposure apparatus using a pulsed light source. The pulsed light source 50 is composed of an excimer laser or the like, and the mask 60 is irradiated with light emitted from the pulsed light source 50. The light that has passed through the mask 60 is transmitted to the wafer 70 placed on the table 80.
irradiated onto the wafer 70, thereby forming a mask pattern on the wafer 70.
The image is projected onto the surface and exposed to light. Note that the photodetector 10 is arranged close to the pulsed light source 50 and receives a part of the light emission output of the pulsed light source 50.

Next, the operation of the apparatus configured as described above will be explained with reference to the timing charts of FIGS. 4 and 5.

A detection signal A proportional to the irradiation energy obtained by the photodetector 10 is supplied to a comparator 21 and a peak hold circuit 26. In the comparator 21, the detection signal A is converted into a rectangular wave by zero point detection comparison, and this comparison output B is supplied to the delay circuit 22.

The delay circuit 22 obtains an output C which is obtained by delaying the comparison output B by a predetermined time τ, and this delayed output C is supplied to the reference pulse generator 23. Here, the delay time τ is set longer than the time it takes for the photodetection signal A to reach its peak from zero. The reference pulse generator 23 generates a pulse signal having a constant width t based on the rise of the delayed output C, and this reference pulse D is supplied to the integrator 24 and the reset pulse generator 27. In the integrator 24, the reference pulse D
A shaped signal is obtained in which the rising and falling times of E are set at a certain time, and this integral output E is supplied to the multiplier 25. Here, the integrator 24 is used to prevent errors from occurring in the calculation results due to the frequency characteristics of the multiplier 25, and by cutting the high frequency components of the pulse D, it reduces errors caused by vibrations during transients. I'm letting you do it.

In the pulse generator 27, the reference pulse D
A reset pulse F is generated based on the falling of , and this reset pulse F is supplied to the peak hold circuit 26 . In the peak hold circuit 26, a signal holding the peak value of the detection signal A is obtained, and this peak hold signal G is supplied to the multiplier 25. Further, the output of the peak hold circuit 26 is reset by inputting a reset pulse F. The multiplier 25 multiplies the integral output E and the peak hold output G. Here, the integral output E is a pulse with a constant voltage and a constant width, and the level of the peak hold signal G is constant in a region where the integral output E exists.

Therefore, the multiplication output H (output of the pulse generation circuit 20) is:
The pulse signal has a voltage proportional to the peak value of the detection signal A and has a constant width.

The output H of the pulse signal generation circuit 20 is supplied to an integrator 3. The integrator 30 sequentially integrates the output H to obtain an output I proportional to the exposure amount. here,
The output voltage vo per pulse obtained by the integrator 30 is
It is determined by the following formula.

Vo = (-1/Cf'Rs), 1"V
p d , where Vp is a constant voltage proportional to the normalized optical peak value, cr and Rs are integral time constants, and t is a constant pulse width. From the above equation, the one-spot pressure proportional to the peak value Vp of the optical output obtained by the photodetector 10 is integrated, thereby making it possible to determine the total exposure amount.

The integrated output I of the integrator 30 is supplied to a comparator 40 and compared with a set voltage ``■'' corresponding to the optimum exposure amount. and,
This comparator 40 outputs an "H" level signal when I>1'. Therefore, by stopping the light emission of the pulsed light source 50 based on the output J of the comparator 40, it is possible to end the exposure when the optimum exposure opening is given to the wafer 70, and it is possible to perform good exposure. becomes.

Thus, according to this embodiment, by generating a pulse signal of a constant width with a voltage proportional to the peak value of the photodetection signal and sequentially integrating this pulse signal, it is possible to generate an output i'4 proportional to the exposure amount. Can be done. Therefore, compared to measurement by visual confirmation using a synchroscope or the like, it is easier to measure the exposure amount, and the measurement accuracy is extremely high. That is, the amount of exposure from a pulsed light source can be easily and highly accurately measured, and the requirements for this are extremely important. Further, by providing a comparator 40 and controlling the pulsed light source 50 based on the comparison output, it is possible to automatically terminate the exposure when the wafer 70 reaches the optimum exposure amount.

Note that the present invention is not limited to the embodiments described above. For example, the pulse signal generating circuit is not limited to the same as shown in FIG. 2, but may be any circuit that generates a pulse signal with a constant width and a voltage proportional to the peak value of the photodetection signal. Further, the integrating exposure meter according to the present invention is not limited to pattern exposure apparatuses, but can be applied to 7111 constants of various exposure apertures by irradiation with pulsed light.

In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described in detail above, according to the present invention, the amount of exposure from the pulsed light source can be electrically determined by 4p1, and measurement can be facilitated and measurement accuracy can be improved. Therefore,
It becomes possible to contribute to optimization of exposure amount in a pattern exposure apparatus using a pulsed light source.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an integrating exposure meter according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of main parts of the exposure meter, and FIG. FIGS. 4 and 5 are schematic diagrams showing the schematic structure of the pattern exposure apparatus used, and are signal waveform diagrams for explaining the operation of the above embodiment. 10... Photodetector, 20... Pulse signal generation circuit,
21... Comparator, 22... Delay circuit, 23... Base pulse generator, 24... Integrator, 25... Multiplier,
26... Peak hold circuit, 27... Reset pulse generator, 30... Integrator, 40... Comparator, 5
0...Pulse light source, 60...Mask, 70...Wafer. Applicant's agent Patent attorney Nina Suzue Figure 2 Figure 3

Claims (3)

[Claims] (1) An integrating exposure meter that measures the amount of light emitted from a pulsed light source and irradiated onto a sample includes a photodetector that detects the light emitted from the pulsed light source, and a detection signal of this photodetector. It is equipped with a pulse signal generation circuit that generates a pulse signal of a constant width with a voltage proportional to the peak value, and an integrator that integrates the pulse signal generated by this pulse signal generation circuit, and performs exposure from the integrated output of the integrator. An integrating exposure meter that is characterized by determining the amount of light. (2) The pulsed light source is an excimer laser, the sample is a semiconductor wafer, and the light from the laser is irradiated onto the wafer through a predetermined mask. Integrating exposure meter described in section. (3) Comparison means for comparing the integrated output of the integrator with a predetermined level is provided, and when the integrated output exceeds the predetermined level, the exposure of the wafer by the laser is terminated. The integrating exposure meter according to item 2.