JPH08274019A - Exposing method and reticle used for the same - Google Patents

Abstract

PURPOSE: To precisely correct the projected magnification error, shot rotation error, etc., by optically detecting the mark positional slippage reflecting the projected magnification error so as to correct the projected magnification according to the mark positional slippage amount. CONSTITUTION: Respective positional measuring marks 16b are formed on the peripheral four parts in the exposure pattern region 16a on a reticle 16. On the other hand, a mark forming part 12a is formed on the periphery of mounting region of a wafer 10 on a wafer stage 12 further to form reference position marks 12b on the four parts of this mark forming part 12a. Next, when the four parts are irradiated with scanned light along both marks, the distance between peaks is measured to compute the positional slippage. In such a constitution, the projected magnification error and rotation error can be detected by detecting the positional slippage ΔX, ΔY relating to the orthogonal axis of the position measuring mark 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method for correcting a projection magnification error, a rotation error, etc. of an exposure shot and a reticle used therefor.

[0002]

2. Description of the Related Art In order to improve exposure accuracy, it is necessary to measure a rotation error of an exposure shot, a projection magnification error, etc. An example of this is disclosed in Japanese Patent Laid-Open No. 3-26211. Has been done. According to the present invention, the positional deviation between the measurement mark formed on the exposure mask and the measurement mark formed on the wafer is calculated by TTL (T
It is detected by the "therough The Lens" method. A plurality of measurement marks formed on the wafer are provided in each exposure area of one shot. The measurement mark is provided for each of a plurality of layers formed by a plurality of photolithography processes. Therefore, a problem has been pointed out that the space efficiency on the semiconductor wafer deteriorates.

In addition, a plurality of measurement marks are arranged in the exposure area of one shot in order to improve the measurement accuracy, and it is necessary to measure and calculate the plurality of measurement marks for each exposure process of one shot. Therefore, the throughput of the exposure process was greatly reduced.

Further, the measurement mark on the wafer, which serves as a reference for detecting an error, includes many variable elements due to the manufacturing cause of the semiconductor wafer, environmental conditions, etc., and serves as a reference mark for detecting various errors. It was inappropriate.

On the other hand, Japanese Laid-Open Patent Publication No. 60-28613 discloses a method of measuring environmental conditions in a clean room in which an exposure apparatus is installed and correcting a projection magnification error based on the measurement result. The environmental conditions are:
Changes in atmospheric pressure around the exposure device, temperature changes, etc.
Especially, since the projection magnification of the projection lens has an environment dependency,
The temperature of the projection lens is measured to correct the projection magnification error.

By the way, in recent years, with the miniaturization of the exposure pattern, the exposure wavelength has become shorter and the wavelength has shifted from i-line to excimer laser. Then, when the short-wave light is used as the exposure light, the problem of a projection magnification error due to the temperature fluctuation of the reticle has been newly pointed out. This issue is
Proceedings of the 40th Joint Lecture Meeting of the Japan Society of Applied Physics held in 1993 No. 2, page 606. This reticle is repeatedly used for exposing a plurality of semiconductor wafers, and a chrome layer is used as a light shielding film.
Therefore, it has been found that the chromium layer thermally expands with time and causes a projection magnification error. To solve the problem of projection magnification error due to the temperature rise of the reticle, Japanese Patent Laid-Open No.
In the invention of JP-A-28613, only the ambient temperature or the temperature of the projection lens is measured, and therefore, it is not possible to appropriately deal with it.

Therefore, it is an object of the present invention to form a reference mark on an object having few fluctuation factors due to manufacturing causes or environmental conditions, and accurately correct projection magnification errors, shot rotation errors, and the like. It is an object of the present invention to provide a possible exposure method and a reticle used therefor.

Another object of the present invention is to provide an exposure method and a reticle used for the same which can correct a projection magnification error and the like without reducing throughput by forming a reference mark on a substrate other than the substrate to be processed. It is in.

Still another object of the present invention is to provide an exposure method capable of accurately correcting a projection magnification error caused by temperature dependence of a reticle.

[0010]

According to a first aspect of the present invention, a pattern on a reticle is projected through a projection lens onto an object to be processed supported on a movable stage, and the object to be processed is projected. In an exposure method for exposing a processing object, the stage having the reference position mark formed thereon is moved with respect to the reticle having the position measurement mark formed thereon, and the reference position mark is formed on an optical path passing through the projection lens. And a step of setting the stage at a position corresponding to the position measurement mark, irradiating the stage with light having an exposure wavelength through the reticle and the projection lens, and the position measurement mark and the reference position mark. From the step of optically detecting the positional deviation amount of both marks reflecting the projection magnification error, based on the positional deviation amount of both marks,
And a step of correcting the projection magnification.

According to the first aspect of the invention, the reference position mark serving as a reference for the position measurement mark formed on the reticle is
It is formed on the stage itself, which has few fluctuation factors due to manufacturing causes or environmental conditions. Then, the position measurement mark and the reference position mark are detected by the TTL method, and since the positional deviation amount of both marks reflects the projection magnification error, the projection magnification is corrected based on this. Since the positional deviation amount of both marks reflects the projection magnification error resulting from all the causes of the temperature variation of the reticle and the change amount of the environmental condition, it is not necessary to measure the individual causes. Since the reference position mark is formed on the stage itself, it is not necessary to detect the projection magnification error for each exposure process of one shot, and the throughput of the exposure process is improved.
Note that the projection magnification can be corrected by, for example, any one or a method of changing the distance between the reticle and the substrate, a method of adjusting the air pressure of the air lens in the projection lens, or a method of adjusting the temperature of the projection lens. Can be realized by a combination of.

As described in claim 2, the positional deviation amount of the two marks reflecting the projection magnification error is the reference position and the position measurement mark at the position distant from the reference position on the projection surface in the radial direction. It can be detected as the amount of positional deviation of both marks along the radial direction.

Further, as described in claim 3, a shot rotation error can be detected from the position measurement mark and the reference position mark, and based on the positional deviation amount of both marks reflecting this shot rotation error,
Shot rotation error correction, for example, reticle rotation correction, can be performed.

As described in claim 4, the positional deviation amount of both marks reflecting the shot rotation error is the radial direction at a position distant from the reference position and the reference position on the projection plane of the position measurement mark in the radial direction. It can be detected as the amount of positional deviation of both marks along the direction orthogonal to.

In order to perform these two error corrections more accurately, as shown in claim 5, a step of comparing the positional deviation amount of both marks in the radial direction or the orthogonal direction with each corresponding allowable value is carried out. It is better to provide more. The steps of correcting the projection magnification error and the shot rotation error are repeatedly performed until the respective displacement amounts satisfy the allowable values.

As described in claim 6, a reticle alignment mark is provided on the reticle, the positional deviation of the reticle with respect to the exposure optical axis is optically detected from the reticle alignment mark, and the optical axis alignment of the reticle is also corrected. You can also

At this time, as described in claim 7, the position measurement mark formed on the reticle can also be used as the reticle alignment mark.

In the step of correcting the projection magnification error, when the object to be processed on the stage is replaced,
It can be performed every time or every time. As a result, the throughput in the exposure process is significantly improved as compared with the case of performing the correction process which is conventionally performed for each one-shot exposure process.

In order to measure the projection magnification error more accurately, as described in claim 9, the exposure mask pattern forming area on the reticle is separated by an equal distance from the center of the exposure mask pattern forming area. It is preferable to provide the position measurement marks at a plurality of points.

As described in claim 10, the position measurement mark is a conjugate position when the reference position mark is measured by the TTL method, that is, a plurality of positions formed on the stage on the optical path passing through the projection lens. It is formed at a position corresponding to each reference position mark. A plurality of position measurement marks formed on the reticle can also be used as a plurality of reticle alignment marks as described in claim 11.

According to a twelfth aspect of the present invention, there is provided an exposure method for exposing the object to be processed by projecting a pattern on a reticle through a projection lens onto the object to be processed supported on a movable stage. Correlation information between the temperature of the reticle and a parameter for changing the projection magnification is stored in advance,
It is characterized in that the temperature of the reticle repeatedly used for exposing a large number of the objects to be processed is measured, and the projection magnification is corrected based on the measured reticle temperature information and the correlation information.

According to the twelfth aspect of the present invention, the correlation information between the reticle temperature and the parameter for changing the projection magnification is stored in advance, and the temperature of the reticle repeatedly used for exposing a large number of objects to be processed is measured. Thus, the projection magnification error due to the temperature dependence of the reticle can be accurately corrected based on the measurement result and the correlation information.

In order to accurately measure the temperature of the reticle,
As described in claim 13, it is preferable that the area of the exposure film formed on the contact portion of the reticle that comes into contact with the temperature sensor provided on the reticle support is set to be substantially equal between the contact portions. As a result, it is possible to reduce the difference in measurement temperature detected by each temperature sensor and to accurately measure the temperature of the reticle.

The step of correcting the projection magnification due to the temperature dependency of the reticle can be performed every time or a plurality of times when the object to be processed on the stage is replaced, as described in claim 14.

The temperature dependence of the reticle depends on the aperture ratio in the light transmitting portion of the reticle, and the smaller the aperture ratio, the more marked the temperature rise rate. Therefore, the correlation information with the reticle temperature and the parameter for changing the projection magnification, which is stored in advance, is information specific to the reticle having different aperture ratios. Instead of measuring and storing correlation information for each reticle,
The invention of claim 15 or claim 16 can also be applied.

According to the invention of claim 15, the correlation information stored in advance is stored for each of a plurality of types of reticles having different aperture ratios, and when a reticle having a predetermined aperture ratio is mounted, the predetermined aperture ratio is attached. The stored correlation information for the reticle with the aperture ratio closest to is shared.

Alternatively, when a reticle having a predetermined aperture ratio is mounted as in the sixteenth aspect of the present invention, interpolation calculation is performed from correlation information stored for two types of reticle having aperture ratios close to the predetermined aperture ratio. Thus, correlation information unique to the reticle can be obtained.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment to which the present invention is applied will be described.
This will be described with reference to the drawings.

First Embodiment FIG. 1 shows an example of an exposure apparatus to which the method of the present invention is applied. In the figure, a substrate to be processed, for example, a semiconductor wafer 10 is supported by a wafer stage 12 which is rotatable around a two-dimensional direction of X and Y and a Z axis orthogonal to the X and Y axes. An exposure source such as an excimer laser source 14 is arranged above the wafer stage 12. A reticle 16 and a projection lens 18 are arranged between the excimer laser source 14 and the semiconductor wafer 10. This reticle 16 is also similar to the wafer stage 12,
It is supported by a reticle support stand 17 which is rotatable around the Z axis and the two-dimensional directions of X and Y. Further, the reticle support base 17 is also movable in the Z axis direction. By moving this reticle support in the X and Y directions, the optical axes of the exposure optical axis 2 and the reticle are aligned. The shot rotation error is corrected by rotating the reticle support 17 about the Z axis. Further, the projection magnification error can be corrected by moving the reticle support stand 17 in the Z-axis direction.

The exposure pattern formed on the reticle 16 passes through the projection lens 18 and is reduced and projected, for example, to ⅕ to form an image on the semiconductor wafer 10. By step-driving the wafer stage 12, the semiconductor wafer 10
It becomes possible to project the exposure pattern of the reticle 16 into each chip formed on the substrate.

As shown in FIG. 2, position measurement marks 16b are formed at four locations around the exposure pattern area 16a of the reticle 16. On the other hand, on the wafer stage 12 and around the mounting area of the wafer 10,
The mark forming portion 12a is formed, and the mark forming portion 12 is formed.
Reference position marks 12b are formed at four locations on a. The thickness of the mark forming portion 12a is equal to the semiconductor wafer 1
It is almost the same as the thickness of 0. Further, by setting the wafer stage 12 to a predetermined position, as shown in FIG.
On the optical path 4 that passes through the projection lens 18, the reference position mark 12b and the position measurement mark 16b correspond to each other at four locations.

The reference position mark 12b and the position measurement mark 16b are used to detect the projection magnification error and the shot rotation error, respectively. For this purpose, the exposure apparatus shown in FIG. 1 is provided with a mark detection optical system 20 having a half mirror 22 arranged between the excimer laser source 14 and the reticle 16. The half mirror 22 measures the reflected light from the reticle 16 and the reflected light from the mark forming part 12 a in the measuring part 32.
It leads to.

When the wafer stage 12 is moved to the position shown in FIG. 2 and then irradiated with light from the excimer laser source 14, the reflected light from the position measurement mark 16b on the reticle 16 and the reference position mark on the mark forming portion 12a. The reflected light from 12b passes through the half mirror 22 and the measurement unit 32.
Be led to.

FIG. 3 shows the reference position mark 12b and the position measurement mark 1 on the projection surface received by the measuring section 32.
6b is shown. In FIG. 3A, each mark 12
The distance between the vertical axes of b and 16b is set to L1 by design. Similarly, the distance between the horizontal axes of the marks 12b and 16b is set to L3 by design. Here, FIG. 3 (A)
As shown in FIG. 5, when both marks 12b and 16b are irradiated with the light 6 scanned along the X direction, the output waveform shown in FIG. The peak-to-peak distance L2 can be measured from this output waveform. Therefore, the positional deviation ΔX of the marks 12b and 16b in the X-axis direction is obtained by the following equation (1).

ΔX = L1-L2 (1) Similarly, when both marks 12b, 16b are irradiated with the light 8 scanned along the Y-axis direction, the output waveform shown in FIG. 3C can be obtained. it can. By obtaining the peak-to-peak distance L4 of this output waveform, the positional deviation ΔY of both marks 12b and 16b along the Y-axis direction is obtained by the following equation (2).

ΔY = L3−L4 (2) The principle that the projection magnification error and the shot rotation error described above can be detected by detecting the positional deviations ΔX and ΔY of the reference position mark 12b and the position detection mark 16b with respect to the orthogonal axes. Will be described with reference to FIGS. 4 to 7.

FIG. 4A shows a state in which the reduction magnification of the projection lens 18 itself is changed due to the environment dependency of the projection lens 18 and different optical paths 4a and 4b are generated. on the other hand,
In the same figure (B), due to the temperature dependence of the reticle 16, when a transmission part on the reticle 16 moves due to thermal expansion,
Different optical paths 4c and 4d passing through the respective transmission parts are shown.

In any case, it can be seen that the imaged positions on the wafer 10 are different. FIG. 5 shows a state in which this phenomenon is represented on the surface on which the reflected light of the reference position mark 12b and the position measurement mark 16b is projected. In the figure, due to the temperature dependence of the reticle 16 or the environment dependence of the projection lens 18, for example, the reference position mark 12b and the position measurement mark 16b in the X-axis direction on the projection surface.
It shows a state where the edges are out of alignment. That is, at the time of design, the position measurement mark 16b should be originally located at a position separated from the reference position O on the projection surface by the distance A, but this is projected in a state shifted by ΔA. It can be understood that this phenomenon when the projection magnification changes occurs not only on the X-axis but also on the Y-axis and in any radial direction from a certain reference point O on the projection surface. Therefore, it can be seen that the projection magnification error is reflected as the amount of positional deviation between the marks 12b and 16b along the radial direction at a position distant from the reference position O on the projection surface in the predetermined radial direction.

On the other hand, FIG. 6 is a principle diagram for explaining the shot rotation error. This figure shows the reticle 1
6 shows a state in which there is a rotational deviation by an angle θ. This rotational deviation can be detected as a state in which the point P, which should originally be located at a position spaced a distance A in the X-axis direction from the center of the reticle 16, is displaced by ΔB in the Y-axis direction.

FIG. 7 shows a state in which this is shown on the projection plane of the reference position mark 12b and the position measurement mark 16b.

In the present embodiment, as shown in FIG. 2, by detecting the corresponding four reference position marks 12b and measurement position marks 16b on the optical path 4 passing through the projection lens 18, the above-mentioned projection magnification is obtained. Errors and shot rotation errors are detected. As shown in FIG. 2, this projection magnification error is caused by a positional deviation amount ΔX of both marks 12b and 16b in the X axis direction at two different points B and C on the X axis.
When calculated as the average of B and ΔXC, (ΔXC−ΔXB)
/ 2.

Similarly, Y of two points A and D different in the Y-axis direction
The positional deviation amount ΔYA of both marks 12b and 16b in the axial direction,
The average of ΔYD is (ΔYA−ΔYD) / 2.

When the projection magnification error is calculated as an average value at these four points A to D, projection magnification error = [(ΔXC−ΔXB) / 2 + (ΔYA−ΔYD) / 2] / 2 = (ΔXC + ΔYA) / 4− (ΔXB + ΔYD) / 4 (3)

On the other hand, when the shot rotation error is calculated as the average value of the positional deviation amounts ΔYB and ΔYC in the y-axis direction at two different points B and C on the X-axis, (ΔYB-Δ
YC) / 2. Similarly, two points A and D in different Y-axis directions
When the shot rotation error is calculated from the average of the positional deviation amounts ΔXA and ΔXD in the X direction at (ΔXA−
ΔXD) / 2.

Therefore, when the shot rotation error is calculated as an average value at the four points A to D, the shot rotation error = [(ΔXA-ΔXD) / 2 + (ΔYB-ΔYC) / 2] / 2 = (ΔXA + ΔYB) / 4- (ΔXD + ΔYC) / 4 (4)

In order to obtain the projection magnification error and the shot rotation error, as shown in FIG. 1, in addition to the measuring section 32, a control section 30 for controlling the error detection operation and the correction operation based thereon is provided. A storage unit 34 and a calculation unit 36 are connected to the unit 30.

From the measuring section 32, L2 and L4 shown in FIG.
Information is output for four points A to D shown in FIG.
It is input to the calculation unit 36 via the control unit 30. On the other hand, the storage unit 34 stores the information of L1 and L3 shown in FIG. 3 in advance. These pieces of information are output to the calculation unit 36 via the control unit 30. In the calculation unit 36, the above (1),
By performing each calculation of (2), it is possible to calculate the shift amount of the amount marks 12b and 16b in the X and Y directions in A to D. After that, the calculation unit 36 uses the above formulas (3) and (4).
The projection magnification error and the shot rotation error can be calculated by performing the above calculation.

The control unit 30 further includes a reticle drive unit 3
8 and the stage drive unit 40 are connected. The reticle drive unit 38 moves the reticle support table 17 in the XY and Z-axis directions, respectively, and rotationally moves it around the Z-axis. The control unit 30 drives and controls the reticle drive unit 38 based on the projection magnification error and the shot rotation error calculated by the calculation unit 36. That is, the reticle support 17 is moved in the Z-axis direction based on the projection magnification error, and the projection magnification is corrected. Further, the reticle support table 17 is rotated around the Z axis based on the shot rotation error, and the shot rotation error is corrected.

In this embodiment, as shown in FIG. 2, reticle alignment marks 16c are formed on the reticle 16 at, for example, two positions around the exposure pattern region 16a. The reticle alignment mark 16c is used to align the reticle 16 with the exposure optical axis 2. Therefore, a reference position mark for optical axis alignment is provided in the optical path of one of the mark detection optical systems 20 or in the measuring section 32 in correspondence with the two reticle alignment marks 16c. Since the reticle alignment operation based on the detection of the reticle alignment mark 16c is known, its details will be omitted. However, the deviation amounts of the reticle alignment mark 16c and the reference position mark (not shown) in the X and Y directions are not shown. The reticle alignment operation is performed by moving the reticle support base 17 in the X and Y directions, which is measured by the measurement unit 32 and via the control unit 30 and the reticle drive unit 38.

The stage driving section 40 is for step-driving the wafer stage 12 in the X and Y directions in order to perform exposure on each of the chips formed on the semiconductor wafer 10.

Next, the above-mentioned projection magnification error correction step,
The process of correcting the shot rotation error and the reticle alignment operation will be described with reference to the flowchart of FIG.

After the reticle 16 is set on the reticle support 17 in step 1, the wafer stage 12 is moved so that the mark forming portion 12a is located directly below the mark detection optical system 20 (step 2). At this stage, the operation of correcting the optical axis deviation of the reticle has not been completed, so the determination in step 3 is NO and the process proceeds to step 4.

In step 4, the excimer laser source 14
Laser light is emitted from the reticle mask 16 and the reflected light from the mark forming portion 12 a on the wafer stage 12 is guided to the measuring portion 32 via the half mirror 22.
The measuring section 32 measures each position of the reference position mark 12b and the position measurement mark 16b in the XY directions. Further, the reticle alignment mark 16c and the reference position mark (not shown) for that purpose are detected.

When step 4 is completed, the optical axis shift of the reticle is first detected (step 5). afterwards,
In step 6, it is judged whether or not each of the detected error values is within the preset allowable range. The respective allowable values are stored in the storage unit 34 in advance, and the determination of Step 6 is performed by the control unit 30. Only if the judgment in step 6 is NO, step 7
At, the step of correcting the optical axis shift of the reticle is performed.

If the determination in step 6 is YES, the shot rotation error is determined based on the information of the reference position mark 12b and the position measurement mark 16b previously measured in step 4 previously performed. Is detected (step 10).

When the optical axis deviation correction of the reticle is performed in step 7, the process returns to step 2 and the light is directed toward the reference position mark 12b and the position measurement mark 16b after the optical axis deviation correction is completed. Irradiate. After that, since the determination in step 3 is YES, the positions of the reference position mark 12b and the position measurement mark 16b are detected in step 8. At this time, it is not necessary to detect the position of the reticle alignment mark 16c.

After that, since the determination in step 9 is NO, a shot rotation error is detected in step 10. In step 11, it is determined whether or not each of the detected error values is within a preset allowable range. The respective allowable values are stored in the storage unit 34 in advance, and the determination of Step 11 is performed by the control unit 30. Only when the determination in step 11 is NO, the step of correcting the shot rotation error is performed in step 12. It should be noted that it is also possible to measure or correct the optical axis shift of the reticle again after correcting the shot rotation error.

If the determination in step 11 is YES, a projection magnification error is immediately detected based on the data collected in step 8 (step 13). On the contrary, when the correction is made in step 12, the process returns to step 2 again,
The reference position mark and the position measurement mark are measured again in step 8, and the process proceeds to step 13 via step 9.

As described above, the reason for collecting the data for the projection magnification error again is that the information for the projection magnification error changes after performing the reticle alignment and the shot rotation error correction as compared with that before the correction. Because it is.

Next, it is judged whether or not the error value detected in step 13 is within the allowable value (step 1).
4). This allowable value is also stored in the storage unit 34 in advance, and the determination process in step 14 is performed by the control unit 30. Then, the projection magnification error is corrected in step 15 only when the detected error value exceeds the allowable value.

After the above operation is completed, the wafer 10 can be exposed. First, in step 16, the wafer 10 is supplied onto the wafer stage 12. Thereafter, after the wafer alignment is performed in step 17, the wafer stage 12 is moved stepwise, and light is emitted from the excimer laser source 14 at each stop position to expose all the chips of the semiconductor wafer 10. The process will be performed (steps 18 and 19). Step 1
When the exposure of all the chips of the semiconductor wafer 10 is completed in 9, the wafer stage 1 is processed in step 20.
The processed wafer 10 is removed from step 2.

After that, in step 21, it is judged whether or not all the exposure steps for one lot consisting of a large number of semiconductor wafers 10 have been completed. When there is another semiconductor wafer 10 to be exposed, the process returns to step 2,
By carrying out the steps 2, 3, 8, 9, 13 to 15, the projection magnification error is corrected again. As a result, even if the environmental conditions of the projection lens 18 are changed or the temperature of the reticle 16 is increased, the projection magnification error is corrected at the timing of exchanging the wafer 10, and highly accurate exposure is performed. It becomes possible to carry out the process. The process of correcting the projection magnification error performed when the wafer 10 is replaced is not necessarily performed every time the wafer is replaced, but may be performed once every plural times. In addition, each of the marks 12b and 16 described above
When detecting b and 16c, above the reticle 16,
Position measurement mark 16b, reticle alignment mark 1
You may make it arrange | position a position measuring microscope in each place corresponding to 6c.

The reticle 1 formed by the electron beam drawing method is also used.
If the drawing deviation that has occurred at the time of creation of 6 is known in advance, the deviation can be stored in the storage unit 72, and the error due to the drawing deviation can also be corrected in step 7 or 12, for example.

Second Embodiment In view of the temperature dependence of the reticle 16, this second embodiment considers
The temperature of the reticle 16 is measured, and the projection magnification error is corrected based on the temperature. For this reason, as shown in FIGS. 9 and 10, the reticle support 17 that supports the reticle 16 is provided with temperature sensors 50 that measure the temperatures of, for example, the four corners of the reticle 16. The temperature sensor 50 can be configured as a thermocouple that contacts the back surface of the reticle 16. As shown in FIG. 11, the back surface of the reticle 16 is provided with chrome films for forming light non-transmissive portions at various places. Exposure pattern formation area 1
Although the chromium film 6a is omitted, the light shielding portion 16 made of a chromium film is formed in a rectangular frame shape so as to surround the periphery of the region 16a.
d is formed. Further, chromium films as contact portions 16e are also formed at the four corners of the back surface of the reticle 16 with which the thermocouple 50 is in contact. The areas of the chromium films in the four contact portions 16e are set to be substantially equal. Thereby, the temperature difference between the four corners of reticle 16 detected by thermocouple 50 can be further reduced. As for the contact portion 16e, it is sufficient that the areas of the chromium films at the respective places are equal, and the areas of the chromium films can be set to 0, respectively. More preferably, the area of the peripheral chromium film in this contact portion 16e is also set to be substantially equal at each of the four locations.

In the exposure apparatus shown in FIG. 9, the projection lens 18
The structure shown in FIG. As shown in the figure, an air lens 18a is provided at the center of the projection lens 18. The air supply unit 60 is provided in the air lens 18a.
And the exhaust part 62 is connected. And the air supply unit 60
The air valves 64a, 64
b is provided. It is known that the projection lens 18 can change the projection magnification by adjusting the air pressure in the air lens 18a.

FIG. 13 shows the relationship between the use time of the reticle 16 that is repeatedly used in the exposure process and the reticle temperature, that is, the exposure pattern region 16a formed on the reticle 16.
3 shows the case where the aperture ratio of the transmission part is different. Since the light from the laser light source 14 is intermittently irradiated, the temperature of the reticle 16 tends to increase with time while increasing or decreasing the temperature. This tendency is more remarkable as the aperture ratio of the light transmitting portion is smaller. In FIG. 14, an example in which the aperture ratio is 0% and the aperture ratio is 70% is given, but the aperture ratio of 0% is more remarkable. Therefore, for example, a reticle having a small aperture ratio, such as a reticle used for forming a contact hole, has a large difference in reticle temperature between the start of use and the lapse of a predetermined time.

FIG. 14 is a characteristic diagram showing the relationship between the reticle temperature and the projection magnification error. It can be seen that as the reticle temperature increases, so does the projection magnification error. This is because the reticle expands due to the temperature rise and the light transmitting portion at a certain position moves outward in the radial direction, and the amount of this movement increases as the reticle temperature increases.

On the other hand, FIG. 15 is a characteristic diagram showing the relationship between the projection magnification and a parameter for controlling this projection magnification, for example, lens air pressure. It is understood that the higher the air pressure of the air lens 18a in the projection lens 18 shown in FIG. 12 is set, the larger the projection magnification of the projection lens 18 can be set.

As is apparent from FIGS. 14 and 15, the temperature of the reticle 16 is measured and the projection lens 1 is measured accordingly.
It can be seen that the projection magnification can always be controlled to be constant by controlling the air pressure in the air lens 18a of No. 8.

As a drive control system for this projection magnification, as shown in FIG. 9, a control unit 70, a storage unit 72, a calculation unit 74, and an air lens drive unit 76 are provided. Control unit 70
Controls the correction of the projection magnification error based on the reticle temperature. In the storage unit 72 connected to the control unit 70, for example, characteristic data shown in FIGS. 14 and 15 are measured and stored in advance. The information stored in the storage unit 72 is not limited to that shown in FIGS. 14 and 15, and at least the correlation between the reticle temperature and the projection magnification control parameter, for example, the lens air pressure may be stored.

The correlation information stored in this storage unit 72 is
Before a batch of wafers 10 in a lot are exposed,
As information unique to the reticle used in the processing, it is preferable to measure the relationship between the reticle temperature and the projection / projection magnification error. This is because the reticle 16 has a different aperture ratio and the reticle temperature-projection magnification error relationship is different if the lots are different.

As another method, as shown in FIG. 13, the rising characteristic of the reticle temperature depends on the aperture ratio, so that the relationship between the reticle temperature and the projection magnification error is previously determined for a plurality of types of reticles having different aperture ratios. It is also possible to measure and store in the storage unit 72. In this case, when a reticle having an aperture ratio different from the aperture ratio stored in advance is used, the stored data relating to the aperture ratio closest to the aperture ratio of the reticle used is diverted as control data. You can Alternatively, the correlation information of the reticle to be used can be obtained by interpolation from the stored information stored for the reticle having two types of aperture ratios close to the aperture ratio of the reticle to be used. This interpolation calculation is executed by the calculation unit 74 shown in FIG.

Such correction of the projection magnification is preferably performed by measuring the temperature of the reticle 16 at regular intervals.
In particular, the semiconductor wafer 1 supported by the wafer stage 12
It is preferable to measure the temperature of the reticle 16 every time or once every several times when 0 is exchanged to correct the projection magnification error.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, the target substrate to be exposed is not necessarily a semiconductor wafer, but may be another semiconductor substrate such as a liquid crystal display (LCD), or the exposure method of the present invention may be applied to various processed substrates other than the semiconductor substrate. You can also

[0075]

According to the exposure method described in claims 1 to 8, even if the environmental conditions of the projection lens change or the temperature of the reticle changes, the stage side of the substrate to be processed is exposed. By detecting the positional deviation between the reference position mark provided and the position measurement mark provided on the reticle,
It is possible to correct the projection magnification and perform highly accurate exposure.

According to the reticle described in claims 9 to 11, since the position measurement mark used as a pair with the reference position mark formed on the stage of the exposure apparatus on which the reticle is installed is formed, It is possible to easily correct the projection magnification when the reticle is installed in the exposure apparatus.

According to the exposure method of claims 12 to 16,
Even if the temperature of the reticle repeatedly used fluctuates, the projection magnification can be corrected by measuring the temperature of the reticle, and highly accurate exposure can be realized.

[0078]

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a first embodiment apparatus in which an exposure method of the present invention is implemented.

FIG. 2 is a schematic perspective view showing a relationship between a reference position mark formed on a stage and a position measurement mark formed on a reticle.

FIG. 3A is a schematic explanatory view showing a state in which a reference position mark and a position measurement mark are projected, and FIGS. 3B and 3C.
Shows a signal waveform obtained by scanning both marks (A) in the X and Y directions, respectively.

FIGS. 4A and 4B are schematic explanatory diagrams for explaining a change in an optical path caused by a projection refraction magnification error.

FIG. 5 is a schematic explanatory diagram for explaining a mark positional deviation amount that reflects a projection magnification error.

FIG. 6 is a schematic explanatory diagram for explaining a shot rotation error.

FIG. 7 is a schematic explanatory diagram for explaining a mark positional deviation amount that reflects a shot rotation error.

8 is a flowchart showing a procedure for correcting a reticle alignment, a projection magnification error, and a shot rotation error using the exposure apparatus shown in FIG.

FIG. 9 is a schematic explanatory view of a second embodiment device for carrying out the method of the present invention.

10 is a plan view of a reticle and a reticle support base used in the exposure apparatus of FIG.

11 is a rear view of the reticle used in the apparatus of FIG.

12 is a schematic explanatory diagram of a projection lens using an air lens used in the device shown in FIG.

FIG. 13 is a characteristic diagram showing the relationship between the time during which the reticle is repeatedly used and the reticle temperature.

FIG. 14 is a characteristic diagram showing the relationship between reticle temperature and projection magnification error.

FIG. 15 is a characteristic diagram showing a relationship between projection magnification and lens air pressure.

[Explanation of symbols]

 2 exposure optical axis 10 substrate to be processed 12 stage 12a mark forming portion 12b reference position mark 14 exposure source 16 reticle 16a exposure pattern area 16b position measurement mark 16c reticle alignment mark 17 reticle support 18 projection lens 18a air lens 20 mark detection optical system 22 Half Mirror 30, 70 Control Section 32 Measuring Section 34, 72 Storage Section 36, 74 Computing Section 38 Reticle Drive Section 40 Stage Drive Section 50 Temperature Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 21/30 516E 516F

Claims (16)

[Claims] 1. An exposure method in which a pattern on a reticle is projected onto a target object supported on a movable stage through a projection lens to expose the target object, and a position measurement mark is formed. With respect to the reticle that has been moved, move the stage on which the reference position mark is formed,
Setting the stage at a position where the reference position mark and the position measurement mark correspond on an optical path passing through the projection lens; and exposing the light having an exposure wavelength to the stage through the reticle and the projection lens. Projecting on the basis of the position deviation amount of the both marks, irradiating upward, and optically detecting the position deviation amount of the both marks reflecting the projection magnification error from the position measurement mark and the reference position mark; An exposure method comprising: a step of correcting magnification. 2. The positional deviation amount of both marks, which reflects the projection magnification error, according to claim 1, wherein the reference position and a position of the position measurement mark at a position distant from a reference position on a projection surface in a radial direction. An exposure method, which is detected as a positional deviation between the marks along the radial direction. 3. The method according to claim 2, wherein a step of optically detecting a positional deviation amount of the both marks reflecting a shot rotation error from the position measurement mark and the reference position mark; and a positional deviation amount of the both marks. And a step of correcting a shot rotation error based on the above. 4. The positional shift amount of both marks reflecting a shot rotation error according to claim 3, wherein the radiation at a position distant in a radial direction from the reference position and the reference position on the projection plane of the position measurement mark. An exposure method, wherein the shot rotation error is corrected on the basis of the positional deviation amount of the both marks along a direction orthogonal to the direction, and the positional deviation amount of the both marks in the orthogonal direction is corrected. 5. The method according to claim 2, further comprising a step of comparing a positional deviation amount of the both marks in the radial direction or the orthogonal direction with each corresponding allowable value, wherein the positional deviation amount is An exposure method, wherein the step of detecting the amount of positional deviation and the step of correcting the projection magnification or the shot rotation error are repeatedly performed until a permissible value is satisfied. 6. The reticle according to claim 1, further comprising a reticle alignment mark on the reticle, and optically detecting a positional deviation amount of the reticle with respect to an exposure optical axis from the reticle alignment mark. An exposure method, wherein the optical axis alignment correction is performed. 7. The exposure method according to claim 6, wherein the position measurement mark on the reticle is also used as the reticle alignment mark. 8. The projection magnification is corrected according to claim 1 or 2, wherein when the object to be processed on the stage is replaced, the steps are performed every time or every plural times. Exposure method. 9. A reticle used to expose an object to be processed supported on a stage through a projection lens, the exposure mask pattern forming area being surrounded by an equal distance from the center of the exposure mask pattern forming area. A reticle having position measurement marks for optically measuring a projection magnification error at a plurality of distant locations. 10. The position measurement mark according to claim 9, wherein the position measurement mark is formed at a position corresponding to each of a plurality of reference position marks formed on the stage on an optical path passing through the projection lens. Characteristic reticle. 11. The reticle according to claim 9, wherein the position measurement mark is also used as a reticle alignment mark. 12. An exposure method for exposing the object to be processed by projecting a pattern on a reticle through a projection lens onto the object to be processed supported on a movable stage, wherein the temperature of the reticle and Correlation information with a parameter for changing the projection magnification is stored in advance, the temperature of the reticle repeatedly used for exposing a large number of the objects to be processed is measured, and the measured reticle temperature information and the correlation are measured. An exposure method, wherein the projection magnification is corrected based on the information. 13. The reticle temperature measuring step according to claim 12, wherein a reticle support table that supports the reticle by contacting the reticle at a plurality of positions on a surface side on which a light-shielding film is formed, A plurality of temperature sensors for respectively measuring the contact portions of the reticle are arranged, and the area of the light-shielding film formed on the contact portion of the reticle in contact with the temperature sensor is set to be substantially equal between the contact portions, and An exposure method characterized in that a temperature difference is measured by reducing a difference in temperature measured by a sensor. 14. The exposure according to claim 12, wherein, when the object to be processed on the stage is exchanged, the steps are performed every time or every plural times to correct the projection magnification. Method. 15. The method according to claim 12, wherein the correlation information is stored for each of a plurality of types of reticles having different aperture ratios of the light transmitting portion, and when a reticle having a predetermined aperture ratio is mounted. Is an exposure method, wherein the projection magnification is corrected by sharing the correlation information stored for a reticle having an aperture ratio close to the predetermined aperture ratio. 16. The correlation information according to any one of claims 12 to 14, wherein the correlation information is stored for each of a plurality of types of reticles having different aperture ratios of the light transmitting portion, and when a reticle having a predetermined aperture ratio is mounted. Is an exposure method, wherein the projection magnification is corrected based on information obtained by interpolating from correlation information stored for two types of reticles having aperture ratios close to the predetermined aperture ratio.