JPH07183210A - Projection aligner - Google Patents

Abstract

PURPOSE:To realize the pattern transfer with high precision by a method wherein the change in the focus position of a projection optical system due to the change in the atmospheric pressure or environmental air pressure of a projection exposure device is avoided to improve the dimensional precision and the alignment precision of a transfer pattern. CONSTITUTION:The projection aligner is composed of an illumination optical system 4, a reticle 5, a projection optical system for transferring the pattern of the reticle 5 to a semiconductor wafer 22 and an X-Y table 21 on which the semiconductor wafer 22 is mounted comprising a part of the projection optical system 7. In such a constitution, the title projection aligner including a movable lens 39 held by a movable lens supporter 40, a piezoelectric element 16 for moving vertically the movable lens 39 with respect to the reticle 5 through the intermediary of the supporter 40 and a controller 24 for controlling the piezoelectric element 16 by the signals from a barometer 23 for detecting the environmental air pressure can correct the change in magnification of the image of the semiconductor wafer 22 of the projection optical system 7 due to the change in the environmental air pressure by moving vertically the movable lens 39 with respect to the reticle 5 according to the environmental air pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus capable of performing highly accurate pattern projection by preventing fluctuations in projection magnification and focus position due to fluctuations in environmental atmospheric pressure.

[0002]

2. Description of the Related Art Generally, a so-called photolithography technique is used in a manufacturing process of a semiconductor device such as an IC or an LSI, and a reticle or a photomask pattern is transferred onto a photomask original plate or a semiconductor wafer surface by using a photographic technique. is doing. In recent years, with the miniaturization of element patterns of semiconductor devices and the higher integration, the size of patterns to be transferred tends to become smaller and smaller. : Microprojection exposure apparatuses such as: 10 have been widely used (published by the Industrial Research Institute, Electronic Materials 1983, Supplement, P97 to P104).

[0003]

By the way, when the present inventor has carried out various pattern transfer using this type of projection exposure apparatus, the reduction ratio of the transferred pattern slightly changes depending on the day, and At the same time, it was found that the focus position also fluctuates slightly. It has been clarified that this variation occurs even if the temperature and humidity in the work room (clean room) where the projection exposure apparatus is installed are kept constant and the wavelength of the light source is stabilized.

From the above, when the present inventor repeatedly conducted various experiments and examined the cause of fluctuation of the reduction (transfer) magnification, the following one result could be obtained. That is, while the variation in the reduction ratio of the pattern was measured every day, the atmospheric pressure on that day was measured and the correlation between them was obtained, and the relationship shown in FIG. 1 was obtained. The graph shown in the figure shows the atmospheric pressure on the horizontal axis and the reduction rate on the vertical axis, and is represented by a substantially linear equation by plotting a large number of data (only some data are plotted in the figure). The correlation, that is, the atmospheric pressure (P) and the reduction fluctuation rate (M), is M = Kp · P + Cp
It was found that the relational expression shown by is satisfied. here,
Kp and Cp are constants determined by the characteristics of the optical system. The reduction ratio (M) is as shown in FIG.
It is defined by the amount of dimensional change with respect to 5 mm.

From this, the present inventor further studied the relationship between the reduction variation rate and the atmospheric pressure, and the variation of the atmospheric pressure and the reduction rate variation in the clean room (chamber) due to the variation of the atmospheric pressure and the focus position at that time. I tried to find a correlation for fluctuations. As a result, as shown in FIG. 2 and FIG. 3, respectively, a correlation similar to the atmospheric pressure can be confirmed between the pressure in the clean room and the reduction rate variation, and the correlation is substantially the same although there is some range of the focus variation. The existence of

The clean room is kept at a pressure slightly higher than the atmospheric pressure (approximately 1 mb) to prevent dust in the atmosphere from entering the clean room.

An object of the present invention is to provide a projection exposure apparatus having a projection optical system that is substantially telecentric on the reticle side, without applying stress to the projection optical system due to heat or pressure of gas, and to atmospheric pressure or projection exposure. By preventing the variation of the projection magnification of the transfer pattern due to the variation of the atmospheric pressure of the apparatus, it is possible to improve the dimensional accuracy and the alignment accuracy of the transfer pattern and realize the highly accurate pattern transfer.

Another object of the present invention is projection exposure capable of preventing a change in projection magnification of a transfer pattern due to a change in atmospheric pressure or environmental atmospheric pressure, without requiring an unnecessarily complicated structure. To provide a device.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0010]

Of the inventions disclosed in the present application, a representative one will be briefly described below.
It is as follows.

That is, the projection exposure apparatus of the present invention includes a table on which a semiconductor wafer is placed, an illumination optical system, a reticle having a desired transfer pattern, and first and second.
A projection optical system that is substantially telecentric at least on the reticle side and projects the transfer pattern onto one main surface of the semiconductor wafer; and a magnification adjusting mechanism that adjusts the projection magnification of the transfer pattern onto the semiconductor wafer. A focus position adjustment mechanism that adjusts the focus position of the optical system with respect to the semiconductor wafer, a barometer that detects changes in the atmospheric pressure or the environmental pressure of the projection exposure apparatus, and a fluctuation amount of the atmospheric pressure or the environmental pressure detected by the barometer. Depending on,
A magnification adjusting mechanism for adjusting the projection magnification of the transfer pattern onto the semiconductor wafer by displacing the second lens group, which is closer to the reticle, of the first and second lens groups forming the projection optical system in the optical axis direction. And a control unit for operating the.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIGS. 4 and 5 show a projection exposure apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an exposure machine body of a projection exposure apparatus, an illumination optical system 4 having a light source 2 and a condenser lens 3 inside, and an illumination optical system 4
The projection optical system 7 has a transfer pattern of the reticle 5 and the like illuminated by the lens, and a lens group 6 for projecting and forming the transfer pattern. Further, although not described in detail, an optical system 8 for performing focus setting and alignment (planar position) setting of the projected image is also incorporated. As shown in the enlarged view of FIG. 5, the projection optical system 7 has a reticle support frame 10 at the upper end of a lens barrel 9 attached thereto, and a position from the lower end fitted into a frame 11. The reticle support frame 10 is two points P ₁ as in the planar structure of Figure 6, the P ₂ is attached to the elastic ring plate 12, and the elastic ring plate 12 two points P ₃ via,
In P ₄ are attached to the lens barrel 9, thereby the reticle support frame by elastic deformation of the elastic ring plate 12 1
0 can be finely moved with respect to the lens barrel 9 in the optical axis direction. Then, at three peripheral points P ₅ , P ₆ , and P ₇ , the piezoelectric element 16 is moved through the balls 14 and 15 between the reticle support frame 10 and the adjusting screw 13 integrally screwed to the lens barrel 9. It is interposed in the axial direction. A predetermined electrode is provided on the piezoelectric element 16 and a lead wire 17 is connected to the piezoelectric element 16, and the lead wire 17 is energized to be expanded and contracted in the optical axis direction according to the amount of energization.

That is, in the case of this embodiment, the reticle support frame 10, the elastic ring plate 12, the adjusting screw 13, the ball 1 are used.
A magnification adjusting mechanism is constituted by 4, 15, the piezoelectric element 16, the lead wire 17, and the like.

The lens barrel 9 having the lens group 6 is also constructed so as to be movable in the optical axis direction with respect to the frame 11, and the screw is provided on the frame 11 side and is rotated by a motor 18. A structure (focus position adjusting mechanism) including a shaft 19 and a screw nut 20 provided on the lens barrel 9 side and screwed into the screw shaft 19 is adopted, and the lens group 6 is rotated along with the rotation of the screw shaft 19. The reticle support frame 10 is moved in the optical axis direction.

An X, Y table 21 (table) is arranged below the exposure machine main body 1, and the X, Y table 2 is provided.
A semiconductor wafer 22 for reducing and projecting the pattern of the reticle 5 is mounted on the substrate 1.

On the other hand, a barometer 23 for detecting the atmospheric pressure in the environment including the main body 1 of the exposure apparatus and the X, Y table 21, usually in a clean room, is arranged in the vicinity thereof, and based on the detection signal of the barometer 23, A control unit 24 that controls the piezoelectric element 16 and the motor 18 is provided. The control unit 24 includes a projection magnification correction calculation circuit 25 and a magnification driver 2
6. A focus position correction calculation circuit 27 and a focus driver 28 are provided, and it is possible to change and control the energization amount to the piezoelectric element 16 and the motor 18 according to the environmental pressure by the barometer 23.

According to the above construction, the focus and alignment are normally set by the action of the optical system 8. At the same time, the atmospheric pressure is detected by the barometer 23.
When this atmospheric pressure is lower than the planned atmospheric pressure, the density of air becomes small, so that the substantial focal length in the lens group 6 becomes small, the projection magnification of the substantial projection pattern image becomes small, and the focal position Becomes smaller. For this reason, the projection magnification correction calculation circuit 25 reduces the distance between the lens group 6 and the reticle 5 based on the correlations shown in FIGS. It is calculated, and the magnification driver 26 is operated based on this. A desired current is applied to the piezoelectric element 16 by the action of the magnification driver 26, and the piezoelectric element 16 is shortened (or expanded) in response to this. As the piezoelectric element 16 is shortened, the reticle support frame 10 is moved downward with respect to the lens barrel 9, thereby maintaining a constant distance between the reticle 5 and the lens group 6, that is, a substantial projection magnification with respect to a change in atmospheric pressure. You can Further, at the same time, the focus position correction calculation circuit 27 calculates the correction amount of the focus position based on the atmospheric pressure, and activates the focus driver 28 to drive the motor 18, so that the lens group 6 is moved in the axial direction. The focus position is made substantially constant with the operation. When the atmospheric pressure is higher than the planned pressure, the reticle 5 and the lens group 6 are moved in the opposite direction to the above, and in this case as well, the magnification and the focus position are substantially constant.

As a result, the substantial magnification and focus position between the reticle 5, the lens group 6 and the semiconductor wafer 22 in the projection optical system are always maintained in spite of the change in the atmospheric pressure as well as the environmental pressure of the projection exposure apparatus such as in a clean room. Since it can be held constant, it is possible to prevent fluctuations in projection magnification, stabilize magnification, and achieve highly accurate pattern transfer. It goes without saying that a good projection pattern can be obtained by stabilizing the projection magnification and setting the focus position to the optimum position.

(Embodiment 2) FIG. 7 shows another embodiment of the present invention.

In the figure, the same parts as those in the first embodiment shown in FIG. 4 are designated by the same reference numerals. In this embodiment, the projection optical system 7
Is the lens group 6 (first lens group) on the side closer to the semiconductor wafer 22 and the moving lens 3 closer to the reticle 5.
9 (second lens group), the movable lens 39 is held by the movable lens support 40 so that it can be displaced in the optical axis direction. The piezoelectric element 16 is interposed between the lens barrel 9 and the movable lens support 40 in a posture such that the expansion / contraction direction coincides with the optical axis direction, and the expansion / contraction deformation of the piezoelectric element 16 causes the movable lens 39 to move along the optical axis. It is configured to be driven in the direction.

That is, in the case of this embodiment, the moving lens 39, the moving lens support 40, the piezoelectric element 16 and the like constitute a magnification adjusting mechanism. A required electrode is provided on the piezoelectric element 16 and a lead wire is connected to the piezoelectric element 16, and electricity is applied through the lead wire, whereby the piezoelectric element 16 is expanded and contracted in the optical axis direction according to the amount of electricity.

Generally, in a telecentric projection optical system in which a light beam enters perpendicularly to the pattern surface, it becomes difficult to correct the magnification by moving the reticle up and down.
In such a telecentric projection optical system,
There is a lens close to the reticle, and the reduction ratio can be changed by moving this lens in the optical axis direction. The reduction rate variation due to the atmospheric pressure can be made constant by detecting the atmospheric pressure with the barometer 23 and moving the movable lens 39 in the optical axis direction according to the atmospheric pressure.

[0024]

【The invention's effect】

(1) .In a projection exposure apparatus having a substantially telecentric optical system on the reticle side, the magnification provided in the projection optical system based on the fluctuation of the atmospheric pressure measured by a barometer or the environmental pressure of the projection exposure apparatus. By operating the adjustment mechanism, after adjusting the magnification so as to cancel the change in the magnification of the transfer pattern due to the fluctuation of the atmospheric pressure or the environmental pressure, the exposure operation of the transfer pattern is performed.
It is possible to reliably prevent the variation of the projection magnification of the transfer pattern due to the variation of the atmospheric pressure or the environmental pressure of the projection exposure apparatus.

Further, as in the case of changing the gas pressure or temperature inside the projection optical system or the like, stress due to the heat or pressure of the gas does not act on the projection optical system, and the projection optical system is caused by the stress. There is no concern that accuracy will deteriorate.

As a result, the dimensional accuracy and the alignment accuracy of the transfer pattern are improved, and highly accurate pattern transfer can be realized.

(2) It is not necessary to provide a closed structure for pressurizing the inside of the lens barrel or to provide an air pressure control device for pressurizing, so that it does not require any more complicated structure than necessary. ,
It is possible to prevent a change in projection magnification of a transfer pattern due to a change in atmospheric pressure or environmental pressure.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the pressure detecting section may detect the atmospheric pressure, or the atmospheric pressure may be detected from the pressure difference between this atmospheric pressure and the environment (clean room) of the projection exposure apparatus which is obtained in advance. Alternatively, it may be controlled directly by the atmospheric pressure.

A mechanical expansion / contraction mechanism can be used in place of the piezoelectric element of the first embodiment.
Since the magnification may be changed due to the change in humidity, the temperature and humidity may be detected and the optical characteristics may be controlled accordingly.

(Field of Use) In the above description, the invention mainly made by the present inventor is applied to a reduction type projection exposure apparatus used in the photolithography technique of a semiconductor device which is the field of use thereof. However, the present invention is not limited to, but is applicable to a projection exposure apparatus in a field other than the semiconductor manufacturing technology, as well as an equal-size exposure apparatus.

[Brief description of drawings]

FIG. 1 is a graph illustrating the correlation between atmospheric pressure, projection magnification, and focus position.

FIG. 2 is a graph illustrating the correlation between atmospheric pressure, projection magnification, and focus position.

FIG. 3 is a graph illustrating the correlation between atmospheric pressure, projection magnification, and focus position.

FIG. 4 is an overall configuration diagram of a first embodiment of the present invention.

5 is an enlarged view of a main part of FIG.

FIG. 6 is a plan view of a main part of FIG.

FIG. 7 is an overall configuration diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 exposure machine main body 2 light source 4 illumination optical system 5 reticle 6 lens group 7 projection optical system 9 lens barrel 10 reticle supporting frame 11 frame 12 elastic ring plate 16 piezoelectric element 18 motor 19 screw shaft 20 screw nut 21 X, Y table 22 semiconductor Wafer 23 Barometer 24 Control unit 39 Moving lens 40 Moving lens support

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Maojima, Central 5-1, Marunouchi, Chiyoda-ku, Tokyo Inside Hitachi, Ltd.

Claims (1)

[Claims] 1. A table on which a semiconductor wafer is placed, an illumination optical system, a reticle having a desired transfer pattern, and first and second lens groups, and is substantially telecentric on at least the reticle side. A projection optical system for projecting the transfer pattern onto one main surface of the semiconductor wafer, a magnification adjusting mechanism for adjusting a projection magnification of the transfer pattern with respect to the semiconductor wafer, and a focus position of the projection optical system with respect to the semiconductor wafer. A focus position adjusting mechanism for adjusting, a barometer for detecting a change in the atmospheric pressure or the environmental pressure of the projection exposure apparatus, and the projection optical system according to the fluctuation amount of the atmospheric pressure or the environmental pressure detected by the barometer. Of the first and second lens groups that make up the second lens group closer to the reticle in the optical axis direction. Projection exposure apparatus characterized by comprising a control unit for operating the magnification adjusting mechanism for adjusting the projection magnification of the transfer pattern with respect to the semiconductor wafer by position.