JPS6076728A - Projecting and exposing device - Google Patents

Abstract

PURPOSE:To make the thermal energy which projecting optical systems receive constant and to maintain the projecting optical systems always in a stable state by making light of the wavelength except the prescribed wavelength incident on the projecting optical systems so that the optical characteristics of the projecting optical systems in an exposing state and a non-exposing state are made roughly equal. CONSTITUTION:Light from a light source 1 is conducted to a double-faced mirror shutter 10' after the light of a (g) line is reflected by a cold mirror 3. The shutter 10' consists of a rotary shutter having a transmission part 10'a which allows incidence of the exposing light and puts projecting optical system 4-8 into the exposing state and a light shielding part 10'b which shuts the exposing light and puts the systems into a non-exposing state. The light of the (g) line is made incident on the reducing projection lens system 8 in the state of exposing and the light of an (e) line is made incident thereon in the state of non-exposing and therefore said system receives always the energy o the light by which the temp. of the lens system 8 for reduction projection is maintained constant and the optical characteristics, i.e., the magnification, etc. are eventually stabilized at the specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Portion IF of the Invention) The present invention relates to a projection exposure apparatus having a projection optical system.

(Aspects of the Invention) FIG. 1 shows a schematic configuration of a reduction projection n-light device for exposing an image of a ready-made circuit pattern onto a wafer, for example. In the figure, after light from a light source 1 is focused by an elliptical reflector 2, it is reflected by a cold mirror 3, passes through a shutter 10 consisting of a rotating plate, an integrator 5, a mirror 4, a condenser lens 6, and then the reticle. A projection type exposure apparatus that illuminates the reticle 7 and forms an image of the circuit pattern of the reticle 7 onto the wafer 9 via the reduction projection lens system 8 is not shown. Note that 11 is an illumination optical system that guides the illumination light of the microscope for pattern overlay on the wafer 9. In general, the projection lens system used in this type of projection exposure apparatus is manufactured with aberrations, magnification, etc. strictly controlled. Ru. In particular, in the reduction projection lens system 8, the exposure range is 2 in diameter on the wafer 9.
The lens used has a large aperture to satisfy high resolution and high numerical aperture. For this reason, the lens barrel itself becomes quite large, and its heat capacity also increases.

In a normal lens, it is not a problem that optical characteristics such as magnification change depending on the energy of light passing through the lens.

However, in the manufacturing stage of ICs, especially VLSIs, in recent years, the line width of patterns has been required to be finer, and the overlay accuracy of patterns on the wafer 9 has also been required to be more precise over the entire surface of the chip. .

For this reason, if there is a magnification error in the projected image of the next chip pattern to be overprinted with respect to the chip pattern printed on the wafer 9, accurate overlay may not have been achieved in part of the chip pattern. However, in other parts, the overlay accuracy is extremely reduced depending on the magnification error.

Although this magnification error varies depending on the optical lens configuration of the projection lens system, it is thought to be caused by the temperature of the lens itself, the air temperature between the lenses, or the temperature change inside the lens barrel.

FIG. 2 shows how the magnification changes depending on the energy of light passing through the lens system. The state in which the magnification changes was measured by the following method.

First, in the conventional exposure condition H shown in FIG. 1, the temperature of the reduction projection lens system 8 is stabilized by leaving it for 1 to 2 hours in a state in which the g-line exposure light does not pass through the reduction projection lens system 8. . Later, as reticle 7, the applicant of the present application filed the patent application in JP-A No. 5
A test reticle with a vernier as disclosed in Publication No. 8-86853 is placed.The test reticle has an Iff& mark on the reticle, and one mark among the plurality of marks is exposed to the light of the projection optical system. This mark is placed at a position where the optical axis passes through, and during overprinting, it is possible to measure the absolute amount of deviation at any position during overprinting, using the mark provided at a position that passes through the optical axis as a reference. This allows optical properties to be measured accurately.

After placing this test reticle on the device, the shutter 10 is opened for a short time to expose the pattern of the test reticle onto the wafer 9, and the exposed wafer 9 is developed to expose the resist surface of the test pattern. Fall to the surface.

Remove the test reticle from the n-front exposure device,
In this state, the shutter 10 is left open for a certain period of time.

After that, the test reticle and wafer 19 are placed on the exposure device again, and the projected image of the test reticle is transferred to the wafer 9.
Expose by overlaying it with the pattern above.

After performing the above steps for a certain period of time, for example, every 5 minutes, the chip pattern on the wafer 9 that has been overprinted at each time interval is read with a vernier at multiple positions within the chip to estimate the overlapping state. Ru.

FIG. 2 shows the relationship between the magnification change obtained as a result and the time during which the exposure light flux passes through the reduction projection lens system 8.

As is clear from the figure, the magnification M of the reduction projection lens system 8 gradually changes with time at the exposure start time t1, and becomes stable at the magnification M2 at the time t2. In other words, this magnification variation amount ΔM is due to the fact that when the exposure light beam passes through the projection lens system 8, the energy of the light causes a temperature rise inside the projection lens system 8, causing a change in the refractive index of the lens system, resulting in a change in magnification. it is conceivable that. Note that in FIG. 2, the magnification on the vertical axis is equivalent to, for example, a value that represents how much misalignment occurs in overprinting at the periphery when the centers of the chips are accurately overlapped. Also, the amount of magnification fluctuation ΔM
It also depends on the light intensity of the lamp as the light source. Although not shown in the figure, the focal position also changes at the same time.

In the conventional reduction projection exposure apparatus shown in FIG. 1, when projecting and exposing the image of the reticle 7 onto the wafer 9,
The shutter 10 transmits and blocks the exposure light, and the stable state of optical characteristics differs depending on whether the exposure light is passing through the reduction projection lens system 8 or not. As mentioned above, there are some cases in which it is not possible to celebrate in advance especially during the transitional state. Therefore, in the manufacturing stage of ICs, especially VLSIs, where miniaturization of pattern line width is required and high pattern overlay accuracy is required over the entire surface of the chip, the optical characteristics of the reduction projection lens system 8 are It is necessary to aim for stability.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems and provide a projection exposure apparatus that always maintains a projection optical system in a stable state.

(Summary of the Invention) A projection exposure apparatus of the present invention includes an exposure light generating means that generates exposure light of a predetermined wavelength; and an optical image of a pattern on a mask, for example, a reticle, is formed on a photoreceptor, for example, a wafer, by the incidence of the exposure light. a projection optical system that allows exposure light to enter the projection optical system to put the projection optical system in an exposed state; and also blocks the exposure light from entering the projection optical system to put the projection optical system in a non-exposed state. The projection optical system includes a switching means such as a shutter; and a light irradiation means for inputting light of a wavelength other than the predetermined wavelength into the projection optical system at least in a non-exposure state; The purpose is to stabilize the optical characteristics of the projection optical system by keeping the thermal energy received by the projection optical system by the incident light constant.

(Example) This invention will be explained in detail based on examples.

FIG. 3 shows a schematic configuration of a reduction projection exposure apparatus which is an embodiment of the present invention. In the figure, the same reference numerals as in the schematic structure of the conventional reduction projection exposure apparatus shown in FIG. 1 indicate the same parts.

In the figure, the exposure light generating means is composed of a light source 1, an elliptical reflecting mirror 2, and a cold mirror 3.

The light source 1 emits exposure light such as 9m light (wavelength 436"m) and light with a wavelength other than 914m, such as e-line light (wavelength 546%m).
) using a mercury discharge lamp. The cold mirror 3 is a gicroic mirror that can selectively reflect g-line light and transmit the others.0 After the light from the light source 1 is focused by the elliptical reflector 2, the g-ray light is reflected by the cold mirror 6. The light of the line is reflected, creating a double-sided mirror.
It is guided to the shutter 10'.

The double-sided mirror/shutter 10' consists of a rotary shutter with reflecting mirrors on both sides, and as shown in FIG.
o'a, and a light shielding portion 1σt that blocks the incidence of exposure light and puts the projection optical system in a non-exposed state. The projection optical system includes an optical integrator 5, a mirror 4, a condenser lens 6, and a reduction projection lens system 8, and projects the pattern image of the reticle 7 onto the wafer 9 using exposure light. The light irradiation means consists of a dichroic mirror 12 that selectively reflects e-line light from the light source 1, a mirror 4"s aperture 16, and a lens 14, and e-ray light is emitted through a double-sided mirror shutter 10'.
Guides the line of light to the projection optical system.

During non-exposure, when the light blocking portion 10'b of the double-sided mirror shutter 10' is located in the optical path between the cold mirror 6 and the integrator 5, the g-line light reflected by the cold mirror 3 is blocked by the double-sided mirror shutter 10'. The light is reflected by the surface reflecting mirror of the light section 10'b and enters the illumination optical system 11. On the other hand, the e-line light reflected by the Dyck mirror 12 passes through the mirror 4a% lens 14, is reflected by the back reflector of the double-sided mirror shutter 10', enters the integrator 5, and enters the reduction projection lens system 8. reach. During exposure when the double-sided mirror shutter 10' rotates and the transmission section 10'a is located in the optical path between the cold mirror 3 and the integrator 5, the g-line light reflected from the cold mirror 3 passes through the integrator 5 to the reduction projection lens. We arrive at Corollary 8, and this
The pattern of the reticle 7 is exposed onto the wafer 9 by nine lines of light. At this time, the e-line light from the lens 14 passes through the transmission section 10'a of the double-sided mirror shutter 10', and therefore does not enter the inch crater 5 and the reduction projection lens system 8. In FIG. 3, the wafer 9 is placed on a two-dimensionally movable stage 60, and the stage 30 is controlled by a drive unit 31 including a motor and the like.

Figure 5 shows the double-sided mirror shutter 1 in the apparatus shown in Figure 6.
0' to obtain the appropriate exposure amount, and the aperture 1
This is an example of a circuit etc. for controlling the opening amount of No. 3.

The entire sequence is based on Mike Ta Computer' (hereinafter referred to as C
It is centrally controlled by the PU (PU) 100. CPU1
00 contains microprocessor (MPU), RAM, R
It includes memory such as OM, input/output/board (I/Q board) for interface with the outside, etc.

In FIG. 6, the light receiving element 101 is placed in the optical path between the condenser lens 6 and the reticle 7 at a peripheral position where it does not block the direct illumination beam to the reticle 7, and detects the intensity of the illumination light of the reticle 7. do.

The amplifier 102 amplifies the photoelectric output of the light receiving element 101 and outputs a signal S1. Analog-to-digital converter (hereinafter referred to as
ADC) 103 digitally converts the signal S1,
The digital value D'1 is output to CPU 1 [IQ].

Further, the signal S1 is digitized by a voltage-frequency converter (hereinafter referred to as VFC) 104 to generate a pulse signal S having a frequency corresponding to the voltage of the signal S1. The counter 105 adds and counts the pulse signal S:. However, the counting contents of the counter 105 are cleared to zero in response to a pulse-like start signal S3 from the CPU 100.

On the other hand, the CPU 100 outputs data D corresponding to a predetermined target exposure amount to a target value set register (hereinafter simply referred to as register) 106. Comparator 107 is counter 1
05 count value data and data set in register 106 D! and when they match, a match signal S4 is sent.
Output. Now, the start signal S3 and the coincidence signal S4 are input to the drive circuit 108 of the shutter 10'. Incidentally, since the shutter 10' is a rotary shutter as shown in FIG. 4, it is assumed here that it is directly connected to and rotated by the pulse motor 17. Therefore, in response to the start signal S3, the drive circuit 108
A drive pulse for rotating 0' by % rotation (45 degrees) is output to the pulse motor 17.

As a result, the shutter 10' is opened and the reticle 7 is irradiated with g-line light. Then, in response to the coincidence signal S4, the drive circuit 108 causes the shutter 10' to move further four times.
A drive pulse for rotating by 5° is output, and the shutter 10' is closed. The CPU 100 outputs data D3 that determines the aperture amount of the diaphragm 13 shown in FIG. 6 to the drive circuit 109. The drive circuit 109 outputs a drive signal according to the aperture amount to the motor 110 that drives the aperture 16, and sets the aperture amount of the aperture to a predetermined value. Also, C.P.
U100 also outputs data D4 for moving the stage 3.0 to the drive unit 31, and also controls the stepping of the stage 30.

Next, the operation of the apparatus according to this embodiment will be explained using FIGS. 3 and 5. First, an operation is performed in which the magnification variation due to the g-line light of the reduction projection lens system 8 and the magnification variation due to the ELM light are correlated with the intensity of both light beams. This correspondence is performed only when manufacturing the device, and the result is sent to the CPU 100 no.
If it is stored as a device constant in the M rumor, it will not be necessary when wafer 9 is sold E. However, considering changes in the light intensity of the light source 1 over time and the case where the light source 1 is replaced, it is desirable to perform the correspondence (calibration) when the device is powered on.

Now, before performing this calibration,
The CPU 100 has a magnification variation ΔM9 due to g-line light,
The intensity Bp of g-line light is stored. This is the method explained in Fig. 2, which calculates the amount ΔMp by which the magnification fluctuates from Ml to 2, and calculates the amount ΔMp by which the magnification has changed from M1 to 2, and also calculates
Calculate the average intensity By of the g-line light. Intensities B and 9 can be easily measured by reading the digital value D1 at regular intervals between times t1 and t2 using the ADCI Q 3 shown in FIG. 5, and averaging these digital values D□.

After the power is turned on, the CPU 100 outputs data D3 for maximizing the aperture of the aperture 13 so that the e-line light enters the reduction projection lens system 8 with the maximum light intensity without passing through the reticle 7. Make it. In addition, the 1st aperture is e I here.
The area to which the I light is irradiated on the reticle 7 is not changed, but the entire surface of the reticle 7 is always irradiated, and only the light intensity is changed. In this way, the aperture 13 is set to its maximum aperture, and the magnification variation amount ΔMe and the average light intensity Be of egA at that time are measured in the same manner as described in FIG. In this case as well, ADC1 in FIG.
Use Q3. During this measurement, the shutter 10' must be left closed for a certain period of time, but this period is controlled by the CPU 100. This shutter 1
0' is closed, the e-line light continues to enter the reduction projection lens system 8. Then, after the certain period of time has passed, CPU1
00 outputs a test reticle carry-in request signal to a display device (not shown). Then, test manually or automatically.
After the reticle is transported to the device, it is positioned and exposure begins. At that point, the CPU 100 sets the data in the register 106 and outputs a start signal S3 (start pulse). As a result, the 'C counter 105 is cleared and the opening of the shutter 10' is started.
(2) The FC 104 generates a pulse signal S2. Therefore, the count value of the counter 105 corresponds to the scene integral value of the g-axis light from the time when the shutter 10' begins to open. When the count value and data D2 match and the comparator 107 outputs a match signal S4, the shutter 10' is rotated at 45°.
It rotates and becomes closed. While the shutter 10' is open, the pattern on the wafer 9 and the pattern on the test reticle are overprinted. In this way,
The CPU 100 exposes the pattern of the test reticle on Ueno 9, repeats irradiation with e-line light for a certain period of time, and at appropriate time intervals when e-green light is irradiated.
Read the data D1 of No.3.

After developing the exposed wafer in the manner described above, the vernier resist image is read with a microscope or the like, and the amount of variation in magnification ΔM e is calculated. 2M e is input from a terminal device (not shown) so as to be stored in the memory of the CPU 100. Of course, the CPU 100 also calculates the intensity Be and stores it in the memory. Next, the CPU 100 calculates the correspondence between the intensity of the 983 light and the intensity of the e-line light. Specifically, the ratio of e-line light intensity required to obtain the same amount of magnification variation can be determined. Therefore, when actually exposing the wafer 9 using the step-and-repeat method, ADClo,
'), the intensity Bg of the 9-line light may be measured from time to time, and the opening amount of the diaphragm 1 may be controlled so that the intensity of the e-line light becomes -Bg. In this way, G-line light is incident on the projection lens system 4 to 8 during exposure, and em light is incident on the projection lens system 8 during exposure, so it is constantly receiving light energy and the humidity in the reduction projection lens system 8 increases. Therefore, the optical characteristics, ie, the magnification, etc. are stabilized at a constant value.

Next, FIG. 6 shows another embodiment of the present invention.

In FIG. 6, the e-line light reflected by the dichroic mirror 12 is focused by the elliptical mirror 2 onto one end face of the light 7 eyeper 15. The other end of the optical fiber 15 is connected to an optical unit 16 including an aperture 13, a sub-shutter, an optical lens, etc. as shown in FIG. The e-ray light emitted from the optical unit 16 passes through the cold mirror 3a and enters the reduction projection lens system 8. The cold mirror 3a has a spectral characteristic of reflecting the g-line light from the integrator 5. The control section 18 is simply the circuit shown in FIG. 5 with the addition of a control circuit for the sub-shutter within the optical unit 16. As shown in FIG. 5, the sub-shutter control circuit includes a drive circuit 111 that outputs a drive signal to a solenoid 112 that drives the sub-shutter 11!1 back and forth in response to an opening/closing signal S from the CPU 100. configured. In FIG. 6, the shutter 10 is driven by a pulse motor 17 and is similar to a conventional shutter. Furthermore, the sub-shutter 113 is basically controlled by the CPU 100 to open and close in conjunction with the opening and closing of the shutter 10;
It is not necessarily limited to that. This will be discussed later. Therefore, also in this example,
Basically, during non-exposure, -em light is transmitted to the optical fiber 1.
5. The g-line light enters the reduction projection lens system 8 via the optical unit 16 and the cold mirror 3a, and during exposure, the g-line light reflected from the cold mirror 6 enters the shutter 10. Inlagrator 5, cold mirror 3a and capacitor
It operates so that the light enters the reduction projection lens system 8 via the lens 6.

Next, the specific operation of the embodiment shown in FIG.
The explanation will be based on a 0-chart diagram. First of all, sub shutter 11! Assume that I is open, and wafer 9
It is assumed that has not yet been placed on the exposure device. When the exposure operation starts, the CPU 100 uses the X step 200 to control the ADC.
l 03(7)7'-Data D1 is read and the intensity Be of all light is stored.

Next, in step 201, the CPU 100 outputs an opening/closing signal Ss to close the sub-shutter 113, and in step 2
At 02, the start signal s3 is output and the shutter 10 is set to σ.
9 Release. At this time, the counter 105 shown in FIG.
By the functions of the register 1o6 and the comparator 107, the shutter 10 is controlled to achieve rJFJ with the target exposure amount, but the purpose of opening the shutter 10 here is to irradiate the light receiving element 101 with light of gm. , the time period during which the shutter 1o is open may be set to an appropriate value. Then, the stage 203 checks whether a coincidence signal S4 is generated, and
When the coincidence signal S4 is generated, the process advances to the next step 204, and the CPU 100 reads and stores the data D from the ADC 103 (7). At this time, the closing of the shutter 10 is started in response to the coincidence signal s4, but since there is a slight time lag, the ADC 103 detects the 11 m of light received by the light receiving element 101 immediately before the start of the closing operation of the shutter 10. Digitize the intensity of. Therefore, the data D1 read in step 204 corresponds to the intensity Bp of one line of light. Next, in step 205, the CPU 100 uses the constant 111K as determined in the first embodiment.
From the intensity Be5Bi stored at ゜204, Be and -B
9 is equal or not. If they are not equal, proceed to step 206, and cptJloo is set to Be and I(・B
Data D3 corresponding to the difference in g is output, and the aperture amount of the diaphragm 13 is reset. This operation maintains the correspondence between the intensity of the 8m light and the intensity of the near-field G-line light.

In the next step 207, the CPU 1QQ outputs the opening/closing signal SI+ to open the sub-shutter 113. As a result, the 8m light enters the reduction projection lens system 8, so
This means that the same amount of light energy (thermal energy) as during exposure is supplied, and no magnification change occurs. Thereafter, in step 208, the wafer 9 coated with photoresist is placed on a two-dimensional movement stage (not shown) of the exposure apparatus.

Then, in step 208, in order to overlay the pattern of the reticle 7 on a predetermined amount H on the wafer 9 and expose it,
Move the stage. Further, the CPU 100 sets data D corresponding to the optimal exposure amount required for the wafer 9 in the register 106. Next, the CPU 100 outputs the opening/closing signal Ss in step 209, and the sub-shutter 1
13, and in step 210, a start signal S3 is issued to open the shutter sum. As a result, the pattern image of the reticle 7 is exposed onto the wafer 9. Then, in step 211, it is determined whether or not the coincidence signal S4 is generated. When the coincidence signal S4 is generated, the process proceeds to step 212, and the CPU
100 outputs the opening/closing signal Ss and outputs the sub-shutter 1
16 is released. Of course, when the match signal S4 is generated, the drive circuit 108 causes the shutter 1 to
0 is closed. Then, in step 213, the wafer 9
It is determined whether or not exposure has been performed repeatedly N times above.
If it has been completed N times, all n-light operations have been completed. If the N exposures have not been completed, the process advances to step 214 and the CPU
Step 100 steps the stage to the next exposure position, and Step 209 loops around again. This step 2
Between step 09 and step 214, the g-line light and the e-line light are alternately irradiated and non-irradiated as shown in Fig. 8, and the temporally constant light energy is continuously applied to retake/I/7. It will be irradiated. That is, during one exposure time tl of 9-line light, the irradiation of the light elJ is interrupted, and during the stepping time t2 for the next exposure, the light ea is irradiated.

Now, in a step-and-repeat reduction projection exposure apparatus, one wafer is exposed several dozen times. When the time required for each step is 2 to 3 seconds, it is not necessary to repeat irradiation and non-irradiation of e-line light for each step. That is, as shown in Fig. 10, the e-line light intensity is kept at a constant value Be during the period when one wafer is exposed, and the e-line light intensity is kept at a constant value Be during the non-side light period after the exposure of the wafer is completed. With increasing intensity, the average thermal energy of the g-line and e-line light passing through the demagnifying projection lens system 8 during the exposure period and the thermal energy of the ei light passing through the demagnifying projection lens system 8 during the non-exposure period. are controlled so that they are approximately equal, so that the energy absorbed by the reduction projection lens system is always thermally constant. Note that the non-exposure period includes, for example, when aligning the reticle or wafer, or when replacing the wafer or reticle, but when replacing the reticle,
Since the e-line light directly enters the reduction projection lens system without passing through the reticle, it is necessary to reduce the intensity of the e-line light.

Therefore, the above operation will be specifically explained based on the flowchart shown in FIG. Prior to the start of exposure operation yR, as shown in FIG. 7, the intensity of g-line light and eIIi! Steps 200 to 207 for making the correspondence with the light intensity are performed in exactly the same way. Therefore, FIG. 9 shows the operation after step 207. After step 207, the CPU
100 proceeds to step 215, where the current aperture amount of the aperture 13, that is, the aperture r during the non-exposure period] ffi A V
Store t in memory.

Next, in step 216, the CPU 100 determines the exposure time t1 and the stepping time 1. , and the intensity Be of the e-line light to be irradiated during the exposure period based on the previously determined intensity Bg of the g-line light and a constant. Its strength B
e becomes Be− by −13j9・(−!=−> operation t
l+t* round. The meaning of this arithmetic expression will be explained with reference to FIG. As shown in FIG. 10, during the exposure period for one wafer, the average g-line light is Strength By is B y - Seiki-B
It becomes y. Assuming that the intensity Be of the e-line light irradiated during the non-exposure period decreases to the intensity Be during the exposure period, the value of (Be-Be) must be equal to -89. Therefore, by adding -ny to Be-Be-, Be-
If ' is set to -89, then ne=B y・C;, 4
1. ) is complete. Next, CPUI OO is X7-772
17, the aperture MA of the aperture 1'5 corresponding to the intensity Be
Play V2 and record it in memory 1. νI. Step 2
Step 18 sets the wafer 9 in the apparatus in the same way as step 208 in FIG. 7, and sets the data D2 corresponding to the exposure time t1 in the register 106. Next, in step 219, the CPU 100 outputs data D3 corresponding to the aperture 11Av2 previously stored, and sets the aperture amount of the diaphragm 16. Then, the shutter 10 is opened, the m-position of the shutter 10 is detected in step 221 which is the same as step 211, and when the shutter 10 is closed, it is determined whether or not the wafer 9 has been exposed N times in step 222 which is the same as step 216. is determined, and if NO, stepping is performed in step 223, which is the same as step 214. Of course, the stepping time is tl, which is a value that can be calculated in advance based on the chip size on the wafer 9 and the moving speed of the stage. After step 223, the process is repeated from step 220. In this way, when the exposure of one wafer is completed in step 222, the CPU'lQQ
4, apply the data IB to the previously memorized aperture 1Av1 to return the opening amount of the diaphragm 13 to the original value, and set e of the intensity Be.
Irradiates a line of light.

Now, in step 225, it is determined whether or not to continue exposing the wafer, and if NO, the process ends.

To expose the next wafer, proceed to step 226;
It is determined whether or not to change the duty of the sub-light time t1 and the stepping time t2. If there is no change in duty, the process proceeds to step 218, and the wafer is exposed again in the same order. If the duty is to be changed, the process proceeds to step 216, where the intensity B of the e-ray light irradiated during the exposure period is changed.
It is repeatedly executed starting from the calculation of e.

As described above, according to the sixth embodiment of the present invention, since e-line light is irradiated even during the exposure period, the sub-shutter 113
There is no need to use the above, and there is an advantage that the configuration and operation are simplified. Therefore, it can be similarly applied to the first embodiment shown in FIG. 6, and is extremely effective in suppressing variations in magnification of the reduction projection lens system 8.

As another modification, if the exposure time t1 and stepping time t2 are constant for all the wafers that are focused by the exposure device, the intensity of e IU light is changed from the beginning to Be during the non-exposure period. The same effect can be obtained even if the configuration is set such that the sub-shutter 116 blocks the e-IJ light irradiation during the exposure period of one wafer. However, in this case, the strength Be is Be = K-B9
- t1-1-t determined for K-Bg-5-.

It is necessary to

In addition, in each of the above embodiments, the light source 1 has two types of g-line light and els light.
It is assumed that one occurs. Therefore, the g-ray light and e
The intensity of the line of light itself cannot be increased or decreased separately.

That is, for the intensity of g-line light, which is exposure light, efa
It is possible to reduce the light intensity with the diaphragm 13, but it is not possible to increase it. Of course, it is not impossible to provide some sort of aperture in the optical path of the g-line light, but this will cause a decrease in the illuminance of the exposure light and cause a decrease in throughput due to an increase in the exposure time t1. Therefore, a light source other than the light source 1 may be provided, and the elfJ light from this light source may be irradiated onto the reduction projection lens system 8 via the optical unit 16 shown in FIG. 6, for example. In this case, it is desirable that the intensity of the e-line light from that other light source is greater than the intensity of the e-line light from light source 1, but it is not necessary; After combining the e-ray light from the light source,
If the configuration is such that the light is emitted through the optical unit 16, it is only necessary to prepare another light source that generates the light intensity corresponding to the amount of light to be intensified. Furthermore, the arrangement of the light irradiation means, which is a combination of another light source and the optical unit 16, does not necessarily mean that the e-line light illuminates from above the reticle 7, that is, from the same direction as the g-ray light illuminates the reticle 7. It is not limited to the location. For example, as shown in FIG. 11, a light source section 20 is provided on the back side of the reticle 7, which is controlled to change the intensity of the C-line light or to irradiate or not irradiate in response to opening and closing of the shutter 10. E-line light 1 from the light source section 20
2 on the back side of the reticle 7.
Make sure to irradiate the area a. e emitted from the light source section 20
Line of light! 2 is reflected by the pattern layer 7a and enters the reduction projection lens system 8, and the magnification of the reduction projection lens system 8 is kept constant.

Furthermore, in each of the above embodiments, the exposure light is g-line light,
eI non-exposure light! Although the wavelength of the exposure light and the non-Fg light is not limited to this.

Light that does not sensitize photosensitive materials, such as infrared rays, has a longer wavelength than G-line and has a higher thermal energy that contributes to raising the temperature of the material, making it suitable as light for thermally stabilizing a reduction projection lens system. be.

Furthermore, although each embodiment has been explained using a reduction projection optical system, thermal stability of the projection optical system can be similarly obtained even when applied to an exposure apparatus equipped with a 1-magnification projection lens, a reflective projection optical system, etc. can.

In addition, although a mercury discharge lamp was used as a light source in the above example,
When the mask pattern is illuminated with M light using pulsed laser light from a high-power laser oscillator, the shutters 10 and 10' as described above are not required. Instead, 1
Since it is sufficient to excite one to several pulses of laser light at the tip of the laser beam, the means for determining the number of pulses, the timing of excitation, etc. acts as a switching means for switching between the light collection state and the non-exposure state.

Furthermore, the same effect can be obtained by using pulsed laser light as light with a non-exposure wavelength. Even then, by controlling the number and interval of pulses, the magnification during the non-exposure period can be kept constant.

Further, there is a non-n
A similar effect can be obtained by providing a dike-quaternary mirror or the like that reflects light of the optical wavelength and enters the projection lens system 8.

(Effects of the Invention) As described above, according to the present invention, a constant amount of energy always passes through the projection optical system, so the magnification of the projection optical system is stabilized at a constant value, and it is possible to Superposition can be performed with extremely high accuracy. Furthermore, it has the effect of stabilizing not only the magnification of the projection optical system but also optical characteristics such as fluctuations of the imaging plane in the optical axis direction, field curvature, and distortion.

In addition, since the light projected to ensure thermal stability of the projection optical system has a wavelength other than the exposure light, it is important to note that the wafer is positioned below the projection optical system due to Since there is no exposure even when exposed to light, there is an advantage that there is no restriction on the operation of the exposure apparatus and no reduction in throughput is caused.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional reduction projection exposure apparatus, Fig. 2 is a diagram of changes in magnification in a lens system, Fig. 3 is a block diagram of an embodiment of the present invention, and Fig. 4 is a plan view of a shutter. 5 is a control block diagram of the embodiment shown in FIG. 6, FIG. 6 is a block diagram of the embodiment of this invention, and FIG. 7 is a flowchart of the operation of the embodiment shown in FIG. 6. Figure 8 shows the exposure light9
Intensity distribution diagram of line light and e-line light, which is non-exposure light, FIG. 9 shows the operation of the step-and-repeat method which is the third embodiment] 4-Chard diagram, and FIG. 10 shows the third embodiment FIG. 11 is a diagram showing the intensity distribution of the I-line light, which is exposure light, and the e-line light, which is non-exposure light. DESCRIPTION OF SYMBOLS 1... Light source, 2... Elliptical reflector, 6, 3a... Cold mirror, 4.4a... Mirror, 5... Integrator, 6... Condenser lens, 7... Reticle, 8... Reduction projection lens system, 9... Wafer, 1
0...Shutter, 10'...Double-sided mirror shutter,
11... Illumination optical system, 12... Dichlic mirror, 1... Aperture, 14... Lens, 15...
Optical fiber, 16... Optical unit, 17... Shutter motor, 18... Control unit, 60... Stage, 31... Drive unit.

Claims (1)

[Claims] 1. Exposure light generating means for generating exposure light of a predetermined wavelength;
a projection optical system that forms a light image of the mask on a photoreceptor by the incidence of the exposure light; an exposure state that allows the exposure light to enter the projection optical system; and an exposure state that allows the exposure light to enter the projection optical system; a switching means for switching between a non-exposed state and a non-exposed state; a switching device for transmitting light of a wavelength other than the predetermined wavelength to the projection optical system so as to make the optical characteristics of the projection optical system approximately equal in the light-reflecting state and the non-exposed state; 1. A projection exposure apparatus comprising: an incident light irradiation means. 2. The switching means includes a shutter that passes and blocks the exposure light, the shutter has a reflective surface on the back side of the exposure light incident surface, and the reflective surface prevents the light from the light irradiation means in the non-exposed state. 2. A projection exposure apparatus according to claim 1, wherein light having an exposure wavelength is incident on said projection optical system. 3. The exposure light generation means has a light source that generates light at the exposure wavelength and the non-exposure wavelength, and an optical member that guides the light at the exposure wavelength to the projection optical system, and the light irradiation means generates the light at the non-exposure wavelength from the light source. The projection exposure apparatus according to claim 1 or 2, further comprising an optical member for guiding the light to the projection optical system.