JP2625076B2 - Projection exposure method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method and apparatus capable of preventing a change in a projection magnification and a focal position caused by a change in an atmospheric pressure and enabling a highly accurate pattern projection.

[0002]

2. Description of the Related Art Generally, in the manufacturing process of semiconductor devices such as ICs and LSIs, a so-called photolithography technique is used, and a reticle and a photomask pattern are respectively transferred to a photomask original plate or a semiconductor wafer surface using the photographic technique. doing. In recent years, with the miniaturization and high integration of the element pattern of a semiconductor device, the size of a pattern to be transferred tends to be further miniaturized. : 10, etc., have been widely used (published by the Industrial Research Institute, Electronic Materials 1983 separate volume, pp. 97-104).

[0003]

The inventors of the present invention have performed various types of pattern transfer using this type of projection exposure apparatus. As a result, the reduction ratio of the transferred pattern fluctuates minutely from day to day, and At the same time, it was found that the focal position also slightly fluctuated. It has been clarified that this fluctuation occurs even when the temperature and humidity in the work place (clean room) where the projection exposure apparatus is installed are kept constant and the wavelength of the light source is stabilized.

[0004] From the above, the present inventor repeatedly conducted various experiments and examined the cause of the fluctuation of the reduction (transfer) magnification. As a result, the following result was obtained. That is, while the fluctuation of the pattern reduction rate was measured every day, the atmospheric pressure on that day was measured and their correlation was obtained, and the relationship shown in FIG. 1 was obtained. The graph shown in the figure is obtained by plotting the atmospheric pressure on the horizontal axis and the reduction ratio on the vertical axis, and is represented by a substantially linear equation by plotting a large number of data (only a part of the data is plotted in the figure). The correlation, that is, the atmospheric pressure (P) and the reduction fluctuation rate (M), is M = Kp · P + Cp
It has been found that the following relational expression is satisfied. here,
Kp and Cp are constants determined by the characteristics of the optical system. In addition, the reduction ratio (M) is, as shown in FIG.
It is defined as the amount of dimensional change for 5 mm.

Accordingly, the present inventor has further studied the relationship between the reduction fluctuation rate and the atmospheric pressure, and has examined the fluctuation of the atmospheric pressure and the reduction rate in the clean room (chamber) due to the fluctuation of the atmospheric pressure, and the focus position at that time. I tried to find the correlation for the variation. As a result, as shown in FIG. 2 and FIG. 3, a correlation similar to the atmospheric pressure can be confirmed between the pressure in the clean room and the variation in the reduction ratio. Was observed.

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

An object of the present invention is to prevent a change in projection magnification such as a reduction ratio of a transfer pattern irrespective of a change in atmospheric pressure or an ambient pressure of a projection exposure apparatus, based on the above-mentioned examination results by the inventor, and It is another object of the present invention to provide a projection exposure method and a projection exposure method that prevent a change in a focal position, thereby improving the dimensional accuracy and alignment accuracy of a transfer pattern and enabling highly accurate pattern transfer.

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

[0009]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the invention of claim 1 comprises a table on which a semiconductor wafer is mounted, an illumination optical system, a reticle having a desired transfer pattern, and a lens group including a plurality of lenses. A projection optical system that projects onto one main surface of the semiconductor wafer, and a magnification adjustment mechanism that adjusts a projection magnification of the transfer pattern onto the semiconductor wafer by moving the reticle or the lens on the reticle side of the projection optical system. And a focus position adjusting mechanism for adjusting a focus position of the projection optical system with respect to the semiconductor wafer. A first step of detecting a change, and the projection optical system and the table in accordance with the change of the atmospheric pressure or the ambient pressure. A focus position adjusting mechanism for relatively changing the distance from the projection optical system, the operation of adjusting the focus position of the projection optical system with respect to the semiconductor wafer independently of the operation of adjusting the projection magnification by the magnification adjusting mechanism. And a third step of transferring the transfer pattern of the reticle to the semiconductor wafer.

The invention according to claim 2 comprises a table on which a semiconductor wafer is mounted, an illumination optical system, a reticle having a desired transfer pattern, and a lens group including a plurality of lenses. A projection optical system that projects the projection pattern onto one main surface of the semiconductor wafer, and a magnification adjustment that adjusts a projection magnification of the transfer pattern with respect to the semiconductor wafer by moving the reticle or the lens on the reticle side in the projection optical system. A mechanism, a focus position adjusting mechanism for adjusting a focus position of the projection optical system with respect to the semiconductor wafer, a barometer for detecting a change in atmospheric pressure or an environmental pressure of an installation environment, and the atmospheric pressure detected by the barometer Alternatively, the distance between the projection optical system and the table is relatively changed in accordance with the fluctuation amount of the ambient pressure. A control section for operating a focal position adjusting mechanism for adjusting a focal position of the projection optical system with respect to the semiconductor wafer independently of the adjustment of the projection magnification by the magnification adjusting mechanism. An exposure apparatus.

[0012]

Embodiments of the present invention will be described below 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 main body of a projection exposure apparatus, in which an illumination optical system 4 having a light source 2 and a condenser lens 3 therein;
And a projection optical system 7 having a lens group 6 for projecting and imaging the transfer pattern of the reticle 5 and the like illuminated by. Although not described in detail, an optical system 8 for setting focus (focus) and alignment (planar position) of the projection image is also provided. The projection optical system 7 has a reticle support frame 10 at the upper end of the lens barrel 9 attached thereto as shown in an enlarged view in FIG. 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,
At P ₄ , the reticle support frame 1 is attached to the lens barrel 9 by the elastic deformation of the elastic ring plate 12.
Numeral 0 can move slightly with respect to the lens barrel 9 in the optical axis direction. Then, at three surrounding points P ₅ , P ₆ , and P ₇ , the piezoelectric element 16 is illuminated via balls 14 and 15 between the reticle support frame 10 and the adjusting screw 13 screwed integrally with the lens barrel 9. It is interposed in the axial direction. The piezoelectric element 16 is provided with required electrodes and connected to a lead wire 17, and by conducting electricity through the lead wire 17, the piezoelectric element 16 expands and contracts in the optical axis direction according to the amount of electricity.

A lens barrel 9 having the lens group 6 is also configured to be movable in the optical axis direction with respect to the frame 11, and includes a screw provided on the frame 11 side and rotated by a motor 18. A structure including a shaft 19 and a screw nut 20 provided on the lens barrel 9 side and screwed to the screw shaft 19 is employed. As the screw shaft 19 rotates, the lens group 6 and the reticle support frame 10 are moved. It is moved in the optical axis direction. Thus, the structure in the reticle support frame 10 and the structure in the lens group 6 constitute an optical path length setting unit that sets a distance between the reticle 5, the lens group 6, and a wafer, which will be described later, that is, an optical path length. .

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

On the other hand, a barometer 23 for detecting the barometric pressure in an environment including the exposure machine main body 1 and the X and Y tables 21, usually in a clean room, is disposed in the vicinity thereof, and based on a detection signal of the barometer 23, A control unit 24 for controlling the optical path length setting unit is provided. The control unit 24 includes a projection magnification correction calculation circuit 25, a magnification driver 26, a focus position correction calculation circuit 27, and a focus driver 28. The piezoelectric element 16 and the motor 1 are controlled in accordance with the atmospheric pressure by the barometer 23.
8 can be changed and controlled.

According to the above configuration, normal focus setting and alignment setting are performed by the action of the optical system 8, and at the same time, the atmospheric pressure is detected by the barometer 23.
If the air pressure is lower than the predetermined air pressure, the density of the 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 small. Becomes smaller. For this reason, the projection magnification correction arithmetic circuit 25 reduces the distance between the lens group 6 and the reticle 5 based on the correlation as shown in FIGS. The calculation is performed, and the magnification driver 26 is operated based on the calculated value. A required current is supplied to the piezoelectric element 16 by the operation of the magnification driver 26, and the element 16 shortens (or expands) accordingly. As the element 16 is shortened, the reticle support frame 10 is moved downward with respect to the lens barrel 9, whereby the distance between the reticle 5 and the lens group 6, that is, the substantial projection magnification with respect to a change in atmospheric pressure is kept constant. it 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 operates the focus driver 28 to drive the motor 18 to move the lens group 6 in the axial direction. The focal position is kept substantially constant with the operation. When the atmospheric pressure is higher than the predetermined pressure, the reticle 5 and the lens group 6 are moved in the opposite direction to the above, and also in this case, the magnification and the focal position are kept substantially constant.

As a result, the reticle 5, the lens group 6, and the wafer 2 in the projection optical system are changed irrespective of the atmospheric pressure as well as the environmental pressure of the projection exposure apparatus such as a clean room.
Since the substantial magnification and the focal position between the two can always be kept constant, the fluctuation of the projection magnification can be prevented, the magnification can be stabilized, and high-precision pattern transfer can be achieved. It goes without saying that a good projection pattern can be obtained by stabilizing the projection magnification and setting the focal position to the optimum position.

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

In the figure, the same parts as those of the embodiment in FIG. 4 are denoted by the same reference numerals. In this example, the moving lens 39 of the lens group 6 that is approaching the reticle is held by the moving lens support 40. Lens barrel 9 and movable lens support 4
0, the piezoelectric element 16 is interposed in the optical axis direction. The piezoelectric element 16 is provided with a required electrode and connected to a lead wire, and by conducting electricity through the lead wire, the piezoelectric element 16 is expanded and contracted in the optical axis direction in accordance with the amount of electricity.

Generally, in a telecentric projection optical system in which a light beam is incident perpendicular to the pattern surface, it is 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 it is possible to change the reduction ratio by moving this lens in the optical axis direction. The reduction rate fluctuation 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.

[0022]

【The invention's effect】

(1) .A change in the atmospheric pressure of the projection exposure apparatus is detected, and stable control is performed so that the substantial refractive index of the projection exposure system does not fluctuate according to the detected value. A change in projection magnification and a change in focal position due to the change can be prevented and these can be stably controlled, thereby enabling highly accurate pattern transfer.

(2) A pressure detecting section for detecting the atmospheric pressure, a substantial optical path length setting section in the projection exposure system, and a constant refractive index in the optical path length setting section based on the detected value of the pressure detecting section. Since the control unit is configured with a control unit for controlling, a substantial refractive index can be controlled in real time by the atmospheric pressure, and the stabilization of the projection magnification can be controlled with high accuracy.

(3) Since the optical path length setting section changes the distance between the lens, the reticle and the wafer in accordance with the fluctuation of the atmospheric pressure and sets it to be substantially constant, high-speed and high-accuracy magnification control is achieved. Since it is possible to further adjust the reticle support angle, it is possible to adjust trapezoidal distortion.

As described above, the invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, the pressure detecting section may detect the atmospheric pressure, and may detect the atmospheric pressure from the pressure difference between the atmospheric pressure and a predetermined environment (clean room) of the projection exposure apparatus. Alternatively, control may be performed directly at atmospheric pressure.

On the other hand, the setting section for keeping the optical path length constant includes controlling the temperature or humidity in the projection optical system to control the change in the optical path length due to the thermal expansion of the lens barrel and the change in the lens focal length due to water vapor in the optical system. It is also conceivable that the method and the configuration are performed so as to achieve the substantially constant optical path. Although it is theoretically possible to stabilize the atmospheric pressure of the projection exposure apparatus, it is extremely expensive in practice and is not practical.

It should be noted that a mechanical expansion and contraction mechanism can be used instead of the piezoelectric element of the first embodiment.
Since the magnification may be changed by a change in humidity, the temperature and humidity may be detected and the optical characteristics may be controlled based on the detected temperature and humidity.

(Usage Field) In the above description, mainly the case where the invention made by the present inventor is applied to a reduction type projection exposure technique used in a photolithography technique of a semiconductor device as a field of application has been described. The present invention is not limited to this, and can be applied to, for example, a projection exposure technique in a field other than a semiconductor manufacturing technique as well as an exposure technique of the same magnification type.

[Brief description of the drawings]

FIG. 1 is a graph illustrating a correlation among an atmospheric pressure, a projection magnification, and a focal position.

FIG. 2 is a graph for explaining a correlation among an atmospheric pressure, a projection magnification, and a focal position.

FIG. 3 is a graph for explaining a correlation among an atmospheric pressure, a projection magnification, and a focal position.

FIG. 4 is an overall configuration diagram of Embodiment 1 of the present invention.

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

FIG. 6 is a plan view of a main part of FIG. 4;

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

[Explanation of symbols]

 DESCRIPTION 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 tube 10 Reticle support 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 Controller 39 Moving lens 40 Moving lens support

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinya Nakagawa 1450, Josuihoncho, Kodaira-shi, Tokyo Inside the Musashi Plant, Hitachi, Ltd. (56) References JP-A-60-79357 (JP, A) JP-A-60-28613 (JP, A) JP-A-60-159748 (JP, A)

Claims (2)

(57) [Claims] 1. A table on which a semiconductor wafer is placed, an illumination optical system, a reticle having a desired transfer pattern, and a lens group including a plurality of lenses, wherein the transfer pattern is formed on one principal surface of the semiconductor wafer. Optical system for projecting light onto the reticle or the reticle in the projection optical system
A magnification adjusting mechanism that adjusts a projection magnification of the transfer pattern with respect to the semiconductor wafer by moving the lens on the lens side, and a focus position adjusting mechanism that adjusts a focal position of the projection optical system with respect to the semiconductor wafer. A reduced projection exposure method using a projection exposure apparatus, comprising: a first step of detecting a change in atmospheric pressure or an environmental pressure of the reduced projection exposure apparatus; the focal position adjusting mechanism for relatively changing the distance between the system and the table, the projection magnification by the magnification adjusting mechanism
A second step of performing an operation of adjusting the focal position of the projection optical system with respect to the semiconductor wafer independently of the rate adjusting operation; and a third step of transferring the transfer pattern of the reticle to the semiconductor wafer. A reduced projection exposure method characterized by comprising: 2. A table on which a semiconductor wafer is mounted, an illumination optical system, a reticle having a desired transfer pattern, and a lens group including a plurality of lenses, wherein the transfer pattern is formed on one principal surface of the semiconductor wafer. Optical system for projecting light onto the reticle or the reticle in the projection optical system
A magnification adjusting mechanism for adjusting a projection magnification of the transfer pattern with respect to the semiconductor wafer by moving the lens on the side of the camera, a focal position adjusting mechanism for adjusting a focal position of the projection optical system with respect to the semiconductor wafer, and an atmospheric pressure. Or, a barometer that detects a change in the environmental pressure of the installation environment, and a distance between the projection optical system and the table is relatively changed according to the amount of change in the atmospheric pressure or the environmental pressure detected by the barometer. By adjusting the magnification
A reduction projection exposure apparatus comprising: a control unit that operates a focus position adjustment mechanism that adjusts a focus position of the projection optical system with respect to the semiconductor wafer independently of adjustment of the projection magnification by a mechanism .