JPH0388317A - Projection exposure apparatus - Google Patents

Abstract

PURPOSE:To make it possible to correct errors in projection magnification of a pattern image and distortion errors excellently by providing adjusting means for moving a body such as reticle which is arranged on the side of the body in a projection optical system and a lens close to the body in the projection optical sytem in the direction of the optical axis of the projection optical system. CONSTITUTION:Adjusting means are provided for performing the following operations. A lens 6 close to a first body 1 in a projection optical system 5 is moved in the direction of an optical axis AX in the projection optical system 5. The projection magnification of a pattern image is adjusted. The first body 1 is moved in the direction of the opitcal axis AX in the projection optical system 5. Then the distortion of the pattern image is adjusted. Namely, a reticle chuck 2 is displaced in the direction of the optical axis AX in the projection lens system 5 with a reticle driving device 3. Thus, a reticle 1 is moved in the direction of the optical axis AX. A wafer chuck 10 is displaced in the direction of the optical axis AX of the projection lens system 5 with a wafer driving device 11. Thus, a wafer 9 is moved in the direction of the optical axis AX. Meanwhile, the field lens 6 is moved into the direction of the optical axis AX with a lens driving device 8. Said driving and control systems are controlled with a microporcessor 23. Thus, the errors in projection magnification of the pattern image and the distortion errors can be excellently corrected.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a projection exposure apparatus, and in particular to an IC,
The present invention relates to a projection exposure apparatus that projects a circuit pattern image of a reticle onto a wafer, which is used when manufacturing semiconductor devices such as LSIs.

[Prior art]

In projection exposure equipment for manufacturing semiconductor devices such as Is and LSI, it is important to improve the accuracy of overlaying the pattern formed on the wafer in the previous process and the pattern image projected onto the wafer by the projection optical system. This is a challenge. Factors that affect this overlay accuracy include projection magnification errors and distortion errors of pattern images, as shown by the applicant in JP-A No. 62-35620. Conventionally, projection magnification errors and distortion errors have been There was no projection exposure apparatus that could satisfactorily correct both.

[Summary of the invention]

An object of the present invention is to provide a projection exposure apparatus that can satisfactorily correct both projection magnification errors and distortion errors of pattern images.

To achieve this objective, the present projection exposure apparatus has telecentric projection optical systems on both the object side and the image side, and a pattern image of a first object placed on the object side is transferred to a second pattern image placed on the image side. In a projection exposure device that projects exposure onto an object,
Adjusting the projection magnification of the pattern image by moving a lens close to the first object of the projection optical system in the optical axis direction of the projection optical system, and moving the first object in the optical axis direction of the projection optical system. At least it has an adjustment means for adjusting the distortion of the pattern image. .

This projection exposure apparatus has adjustment means for moving the first object and a lens close to the first object of the projection optical system in the optical axis direction of the projection optical system, so that projection magnification errors and distortions of the pattern image can be caused. It becomes possible to correct errors favorably.

The distortion error that is a problem in ordinary projection exposure equipment is mainly caused by the symmetrical distortion aberration of the projection optical system. Therefore, the first object is moved in the optical axis direction of the projection optical system so that this symmetrical distortion aberration is corrected. By moving the pattern image by a fixed amount, distortion errors in the pattern image can be corrected.

Some features and specific configurations of the present projection exposure apparatus are described in detail in the embodiments shown below.

[Embodiment] FIG. 1 is a schematic diagram showing an embodiment of a projection exposure apparatus of the present invention.

In FIG. 1, l is a reticle on which a circuit pattern is drawn, 2 is a reticle chuck that holds the reticle l by suction, and 3
4 is a reticle drive device attached to the reticle chuck 2;
5 is a reticle stage that supports a reticle drive device 4;
6 is a reduction projection lens system that is telecentric on both the object side and the image side, and 6 is a lens of the projection lens system 5 disposed close to the reticle 1 (hereinafter referred to as "field lens 6").
, 7 is a lens system consisting of several lenses other than the projection lens system 5, 8 is a lens driving device for moving the field lens 7 in the direction of the optical axis AX of the projection lens system 5, and 9 is coated with a sensitive material such as resist. 11 is a wafer drive device attached to the wafer chuck 9, 12 is a wafer drive device 11, and 10 is a wafer chuck that holds the wafer 9 by suction. shows a movable wafer stage.

The reticle drive device 3 and the wafer drive device 11 each consist of a piezoelectric element, etc., and the reticle drive device 3 displaces the reticle chuck 2 in the direction of the optical axis AX of the projection lens system 5 to move the reticle l in the direction of the optical axis AX. The wafer drive device 11 displaces the wafer chuck IO in the direction of the optical axis AX of the projection lens system 5, thereby moving the wafer 9 in the direction of the optical axis AX. On the other hand, the lens driving device 8 uses air pressure to move the field lens 6 in the direction of the optical axis AX of the projection lens system 5. The specific structure of the lens driving device 8 is disclosed in Japanese Patent Application Laid-Open No. 62-32613 filed by the applicant of the present invention, so a description thereof will be omitted here.

The reticle chuck 2 is driven by the reticle drive device 3 based on a signal from the reticle drive control system 13, and at this time, the position of the reticle I in the optical axis AX direction is detected by the reticle position detector 15.

Similarly, the field lens 8 is driven by the lens drive device 8 based on a signal from the lens drive control system 16, and at this time, the position of the field lens 8 in the optical axis AX direction is detected by the lens position detector 17. Detected. The reticle position detector 15 and the lens position detector 17 can be composed of various position detectors such as an optical encoder. Further, the wafer chuck lO is driven by the wafer drive device 11 based on a signal from the wafer drive control system 14, and at this time, the position of (the surface of) the wafer 9 in the optical axis AX direction is detected by the focus detector 18. be done. The focus detection jl18 is composed of an air sensor or an optical sensor that has been conventionally used in this type of projection exposure apparatus. Reticle position detector 15, lens position detector 1
7 and the focus detector 18 are input to the microprocessor 23. On the other hand, the projection lens system 5
An atmospheric pressure sensor 19, a temperature sensor 20, and a humidity sensor 21 are provided to detect changes in atmospheric pressure, temperature, and humidity around the projection lens system 5, and a lens temperature sensor 22 is provided to detect changes in temperature due to light absorption of the projection lens system 5. These various sensors 19, 20. 21. Signals from 22 are also input to microprocessor-23. Also, a reticle drive control system 13, a lens drive control system 16,
and the wafer drive control system 14 is a microprocessor-23.
controlled by

Reference numeral 24 indicates an illumination system that illuminates the circuit pattern of the reticle l with uniform illuminance, and the illumination system 24 has a wavelength λ=248.4 nm.
A KvF excimer laser that emits laser light is provided as a light source for exposure. The laser beam from the illumination system 24 is directed to the wafer 9 via the reticle l and the projection lens system 5.
The circuit pattern image of the reticle I is projected onto the wafer 9. In this embodiment, 1.
Each lens constituting the projection lens system 5 has a wavelength λ=248
．． Synthetic quartz (S) with high transmittance for 4 nm light
Manufactured by iO□).

A specific configuration of the projection lens system 5 is shown in FIG. FIG. 2 is a cross-sectional view of the projection lens system 5, showing the reticle l and the wafer 9.
In between, 12 lenses denoted by symbols G and -G1□ are arranged along the optical axis AX to constitute the projection lens system 5. A lens designated by reference numeral G1 in FIG. 2 constitutes the field lens 6 of FIG. 1 as a single lens. Further, lens groups indicated by symbols G2 to G12 correspond to the lens system 7 in FIG.

Table 1 shows the lens data of the projection lens system shown in FIG. In Table 1, R+ (i=1 to 24) is the known curvature (m m ) of the i-th surface counting sequentially from the reticle l side, and D+
is the axial wall thickness or axial air gap (mm) between the i-th and i+1-th surfaces counting sequentially from the reticle L side, N
I (i = 1 = 12) is the lens QI (i = 1
~12). In addition, SL is the axial air gap between the circuit pattern surface of the reticle 1 and the reticle 1 side surface of the lens G1, and S2 is the axial air gap between the wafer 9 side surface of the lens G12 and the wafer 9 surface. show.

Table S, = 100.0O000 Table 2 shows the axial air distance S2 between the reticle l and the lens 61, and the lens G 11 in the projection lens system shown in Table 1.
Projection lens system when the axial air spacing S2 between G1 and wafer 9 and the axial air spacing 021 (i=1xll) between adjacent lenses G1 and G+++ (i=1xll) are each individually changed by 1 mm. A shift amount ΔSD of the image point at a position of an image height of 10 mm on the image plane due to a change in symmetrical distortion (hereinafter referred to as "symmetrical distortion change amount ΔSDJ").

) and the shift amount Δβ (hereinafter referred to as “
"projection magnification change amount Δβ". ) and the ratio of both 1ΔSD
/Δβ1 is shown. Note that a shift of the image point in a direction away from the optical axis of the projection lens system is given a positive sign, and a shift of the image point in a direction toward the optical axis of the projection lens system is given a negative sign.

Table 2 In this embodiment, based on Table 2, it was decided to adjust the projection magnification and the symmetrical distortion by adjusting both the interval S1 and the interval D2, which have small variations in aberrations other than the symmetrical distortion.

Now, assuming that the amount of change in the distance S is ΔS 1 and the amount of change in the distance D2 is ΔD2, the amounts of change ΔSD and Δβ in symmetrical distortion and projection magnification can be expressed by the following equations, respectively, from Table 2.

Therefore, ΔD2+ΔSl is given by the following equation.

However, k l = (15,4)-' Changes in the aberration of the projection lens system 5 due to changes in the distance S0, that is, the distance between the projection lens system 5 and the reticle l, are caused by changes in paraxial amounts such as projection magnification and focus position. The ratio of the amount of change in the amount of aberration to the amount of change in the paraxial amount, the amount of change in the amount of immediate aberration, and the amount of change in the paraxial amount are small. This is because the inclination of the ray within the projection lens system 5 is larger than the inclination of the ray between the object plane and the projection lens system.
This is because when the air distance between the lenses changes, the difference in height of incidence of light rays on the refractive surfaces of the lenses increases, resulting in a large change in aberrations. Therefore, in this embodiment, the projection magnification is adjusted by moving the lens G1 (field lens 6), mainly by adjusting the intervals S1 and D2, and the distortion is adjusted by moving the reticle l, mainly by adjusting the intervals S1. This corrects both the projection magnification error and the symmetry distortion error in the projection exposure apparatus.

Returning to FIG. 1, a method for correcting projection magnification errors and distortion errors of pattern images in this projection exposure apparatus will be described in detail.

The microprocessor 23 has calculation formulas programmed in its memory for determining the projection magnification change amount Δβ and the distortion change amount ΔSD of the projection lens system 5, and each calculation formula is based on atmospheric pressure, temperature, humidity, and The amount of variation in the temperature of the projection lens system 5 from a predetermined reference value is a variable. The above-mentioned calculation formula (2) is also programmed in this memory, and by substituting the values of Δβ and ΔSD into calculation formula (2), the amount of movement of the field lens 6 and the amount of movement of the reticle 1 are calculated. . In addition, the values of Δβ and ΔSD can be expressed as atmospheric pressure, temperature,
A calculation formula based on humidity and temperature changes of the projection lens system 5 can be derived through experiments.

On the other hand, the focus position of the pattern image by the projection lens system 5 changes depending on the atmospheric pressure, temperature, and humidity around the projection lens system 5 and the temperature of the projection lens system 5. It also changes depending on the position of. Therefore, in this embodiment, a calculation formula for determining the amount of change in the focus position of the projection lens system 5 based on these fluctuation factors is programmed into the memory of the microprocessor 23, and the focus position is determined based on this calculation formula. I try to understand it accurately.

The microprocessor 23 includes an air pressure sensor 19, a temperature sensor 20, a humidity sensor 21. Receiving signals corresponding to atmospheric pressure, air temperature, humidity, and lens temperature from the lens temperature sensor 22, the amount of movement of the reticle I and the amount of movement of the field lens 6 are determined based on the above-mentioned predetermined conditional expressions. On the other hand, signals corresponding to the positions of the reticle I and the field lens 6 (with respect to the optical axis AX direction) from the reticle position detector 15 and the lens position detector 17 are input to the microprocessor 23. microprocessor
23 inputs the position signal of the reticle l and the signal corresponding to the movement amount of the reticle l to the reticle drive control system 13, and inputs the position signal of the field lens 6 and the signal corresponding to the movement amount of the field lens 6 to the lens drive control system. 16.

Then, the reticle drive control system 13 applies predetermined control signals to the reticle drive device 3 in response to each signal from the microprocessor 23, and the reticle drive device 3 moves the reticle I by a predetermined amount in the direction of the optical axis AX. Further, the lens drive control system 16 provides a predetermined control signal to the lens drive device 16 in response to each signal from the microprocessor 23,
The field lens 6 is moved along the optical axis A by the lens driving device 16.
Move a predetermined amount in the X direction. By adjusting the positions of the reticle 1 and the field lens 6, projection magnification errors and distortion errors of the pattern image due to fluctuations in the atmospheric pressure, temperature, humidity around the projection lens system 5, and the temperature of the projection lens system 5 are corrected. be done.

The microprocessor 23 also includes a reticle position detector 15, a lens position detector 17, an atmospheric pressure sensor 19, a temperature sensor 20, a humidity sensor 21, . Based on the signals from the lens temperature sensor 22 and the lens temperature sensor 22, the focus position of the pattern layer by the projection lens system 5 is detected, and based on the signal from the focus detector 18 corresponding to the position of (the surface of) the wafer 9, The wafer drive control system 14 is controlled so that the wafer is positioned at the focus position. The wafer drive control system 14 gives a predetermined control signal to the wafer drive device 11, causes the wafer drive device 11 to move the wafer 9 in the direction of the optical axis AX, and brings the wafer 9 to the focus position of the pattern image.
position.

Through the operations described above, the projection magnification of the pattern image is corrected to a predetermined magnification, and the distortion of the pattern image is suppressed within a predetermined tolerance range, so that the pattern formed on the wafer 9 in the previous process and the pattern image are can be accurately superimposed. Further, since the position of the wafer 9 and the focus position of the pattern image are also matched, it becomes possible to project a clear pattern image onto the wafer 9.

In this embodiment, the movable field lens 6 for adjusting the projection magnification of the pattern image is composed of one lens (G,), but the field lens 6 may be composed of a plurality of lenses. . In addition, in this embodiment, in order to detect changes in the projection magnification and distortion of the pattern image due to fluctuations in atmospheric pressure, air temperature, humidity, and lens temperature, an atmospheric pressure sensor 19 is used.
, temperature sensor 20, humidity sensor 21. Although the output signal from the lens temperature sensor 22 was used, the pattern image projected by the projection lens system 5 is captured by an imaging device, and the projection magnification and distortion of the pattern image are determined based on the size and shape of the pattern image. Changes may also be detected.

At this time, if an imaging device is attached to the wafer stage 12, changes in the projection magnification and distortion of the pattern image can be detected at a desired time, and the configuration of the exposure device does not become complicated.

〔Effect of the invention〕

As described above, according to the present invention, in a projection exposure apparatus having a projection optical system in which both the object side and the image side are telecentric, an object such as a reticle placed on the object side of the projection optical system;
Since the projection optical system has adjustment means for moving the lens close to the object in the optical axis direction of the projection optical system, the projection magnification and distortion of the pattern image drawn on the object by the projection optical system can be accurately adjusted. Can be adjusted. Therefore, even if an error occurs due to a change in the projection magnification or distortion of the pattern image due to atmospheric pressure fluctuations around the projection optical system, etc., the adjustment means can satisfactorily correct the projection magnification error or distortion error of the pattern image. become.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a projection exposure apparatus of the present invention. FIG. 2 is a sectional view showing a specific configuration of the projection lens system of the apparatus shown in FIG. l... Reticle 2... Reticle chuck 3... Reticle drive device 4... Reticle stage 5... Projection lens system 6... Filled lens 7... Lens system 8... Lens drive device 9... Wafer 10... Wafer chuck 11... Wafer drive device 12... Wafer stage 13... Reticle drive control system 14... Wafer drive control system 15... Reticle position detector 16... ... Lens drive control system 17 ... Lens position detector 18 ... Focus position detector 19 ... Barometric pressure sensor 20 ... Temperature sensor 21 ... Humidity sensor 22 ... Lens temperature sensor 23 ...・Microprocessor

Claims (1)

[Claims] In a projection exposure apparatus that has telecentric projection optical systems on both the object side and the image side and projects and exposes a pattern image of a first object placed on the object side onto a second object placed on the image side, the projection optical system moving a lens close to the first object of the system in the optical axis direction of the projection optical system to adjust the projection magnification of the pattern image, and moving the first object in the optical axis direction of the projection optical system; A projection exposure apparatus comprising an adjusting means for adjusting distortion of the pattern image.