JPS6373519A - Projection aligner - Google Patents

Abstract

PURPOSE:To enable pattern transfer always at a predetermined reduction ratio by providing a temperature controller in the wafer stage, and controlling the wafer temperature according to the fluctuation of the reduction rate of a projection aligner, thereby offsetting the fluctuation of the reduction ratio with the thermal expansion and thermal shrinkage of the wafer. CONSTITUTION:A mask M is illuminated by a light source 11 and a condenser lens 12, and a mask pattern is projected and exposed on the surface of a wafer W by an imaging lens 13. And, the atmospheric pressure at this time is measured by a barometer 32, and in a microcomputer 31, the fluctuation of the reduction ratio at this atmospheric pressure is calculated from the characteristics of the atmospheric pressure and the reduction ratio. Further, this reduction ratio is applied to the thermal expansion coefficient of the silicon wafer to calculate a wafer size needed for correcting this fluctuation. And this calculation result is outputted to a heater controller 24 or a flow rate control valve 26 in order to control the electrical energization amount of a heater 23 or the cooling medium flow rate of a cooling pipe 25 based on the measured temperature of a thermocouple 27, thereby heating or cooling the wafer W to a required temperature through a base stand 21. For this, the wafer W is thermally expanded or thermally shrinked in response to the reduction rate. Therefore, a pattern transfer with a stable reduction rate can be achieved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a projection exposure apparatus used for manufacturing semiconductor devices, and in particular to a projection exposure apparatus that corrects fluctuations in image magnification in a projection optical system to enable high-precision projection. Related to exposure equipment.

[Conventional technology]

In a photolithography process, which is one of the manufacturing processes of semiconductor devices, a pattern of a reticle or a photomask is transferred onto a semiconductor wafer using a projection exposure device such as a stepper. In particular, in recent years, as the element patterns of semiconductor devices have become finer and denser, the size of transferred patterns has also become smaller and smaller, and the reduction ratio of projection exposure equipment has also increased to 1:5 or 1:1.
0 has been adopted.

[Problem that the invention seeks to solve]

By the way, it has been found that when a pattern of a reticle or a photomask is transferred using this type of projection exposure apparatus, variations in the size of the transferred pattern occur due to differences in exposure date and time and differences in exposure environment. That is, JP-A-1986-
According to the specification of No. 261137, the optical system of the projection exposure apparatus, that is, the focal length of the lens is changed due to changes in the temperature, humidity, and atmospheric pressure of the environment of the projection exposure apparatus, and the reduction magnification is changed depending on the time and environment. This is caused by

In particular, changes in this reduction rate are largely due to changes in atmospheric pressure, and according to the characteristic diagram described in the above specification, as shown in Figure 3, as atmospheric pressure increases, the reduction rate (with respect to the standard size) It can be seen that the projected image becomes larger and the projected image becomes larger.

For this reason, the apparatus described in the above specification adopts a configuration in which the optical axis distance of the optical system is changed and adjusted according to changes in atmospheric pressure, etc., but this makes the projection exposure apparatus complicated and requires small dimensions. In order to make adjustments, there are practical problems such as the need to operate the control system with high precision.

An object of the present invention is to provide a projection exposure apparatus that can cope with fluctuations in the reduction ratio of a projection exposure apparatus, always ensure a stable reduction ratio, and that can be easily controlled without complicating the configuration of the projection exposure apparatus. The purpose of the present invention is to provide an exposure device.

[Means for Solving the Problems] The projection exposure apparatus of the present invention includes a temperature controller on the wafer stage that supports the wafer, and enables the temperature controller to be controlled in response to changes in the reduction ratio of the optical system. The structure is such that the temperature of the wafer can be changed at any given time.

[Effect]

The temperature controller installed on the wafer chuck is controlled in accordance with changes in factors that change the reduction rate of the optical system, such as atmospheric pressure, and the wafer temperature is changed accordingly, thereby changing the reduction rate of the optical system. At the same time, the wafer thermally expands or contracts, changing its dimensions. As a result, the dimensions of the projected pattern projected on the wafer will always be the predetermined dimensions when the wafer is returned to room temperature, making the actual reduction rate of the projected pattern stable and achieving high-precision pattern transfer. be able to.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a perspective view conceptually showing an embodiment of the present invention, and this projection exposure apparatus includes an optical system 1 that directly performs pattern transfer, and a semiconductor wafer W such as silicon to which the pattern is transferred.
The wafer stage 2 supports the wafer stage 2, and the control system 3.

The optical system 1 includes a light beam B11 composed of a mercury lamp or the like, a condenser lens 12. It is equipped with an imaging lens 13 and the like, and can project the pattern of the reticle or photomask M onto the surface of the wafer W on the wafer chuck 2 at a required reduction ratio.

The wafer stage 2 is constructed as a so-called XY stage, and as shown in its cross-sectional structure in FIG. With the open configuration, the wafer W can be suctioned and fixed onto the surface of the base 21 using these suction holes 22. Further, a heater 23 is buried inside the base 21, and the amount of current flowing to the heater 23 is changed by a heater controller 24, so that the base 21 to the wafer W can be heated to a required temperature accordingly. It consists of Further, a cooling pipe 25 is extended from the base 21, and a flow rate control valve 26 is inserted therein to control the amount of cooling medium flowing back to a cooling source (not shown). Further, the base 21 is provided with a thermocouple 27 for measuring temperature.

Furthermore, the control system 3 is mainly composed of a microcomputer 31, and its input interface includes the thermocouple 2.
7 and a barometer 32 for measuring atmospheric pressure, and the heater controller 24 of the heater 23 and the flow rate control valve 26 of the cooling pipe 25 are connected to the output interface, respectively. The microcomputer 31 is manually input with the data of the correlation between the atmospheric pressure and the reduction ratio of the optical system 1, and the correlation between the temperature of the semiconductor wafer and its coefficient of thermal expansion, and configures a necessary program.

According to the projection exposure apparatus having this configuration, the mask M can be illuminated by the light source 11 and the condenser lens 12, and the mask pattern can be projected and exposed onto the surface of the wafer W supported on the wafer stage 2 by the imaging lens 13. can. Then, the atmospheric pressure at this time is measured with the barometer 32, and the atmospheric pressure data is input into the microcomputer 31. Then,
The microcomputer 31 calculates the fluctuation of the reduction rate at this atmospheric pressure from the characteristics of atmospheric pressure and reduction rate shown in FIG. Furthermore, necessary calculations are performed by applying this reduction rate to the coefficient of thermal expansion of the silicon wafer, and the wafer dimensions necessary to correct the change in this reduction rate are calculated. Then, this calculation result is output to the heater controller 24 or the flow rate control valve 26, and the amount of electricity supplied to the heater 23 and the amount of coolant flowing through the cooling pipe 25 are controlled based on the temperature measured by the thermocouple 27, and the base of the wafer stage 2 is controlled. The wafer W is heated or cooled to a required temperature via the table 21.

Therefore, the wafer W is thermally expanded or contracted in accordance with the reduction ratio. That is, when the atmospheric pressure increases and the reduction rate increases, the wafer W is heated and thermally expanded. For this reason,
Even if the pattern projected in this state is large, a predetermined pattern size can be obtained when the wafer is returned to room temperature. Similarly, when the atmospheric pressure decreases and the reduction rate decreases, the wafer may be cooled and contracted to perform projection exposure, thereby making it possible to obtain a predetermined pattern size when the wafer is at room temperature.

Therefore, regardless of fluctuations in the reduction ratio of the optical system due to the influence of atmospheric pressure, etc., projection exposure can always be performed at a predetermined reduction ratio, and pattern transfer with a stable reduction ratio can be realized.

Here, the above-mentioned embodiment is only one embodiment of the present invention, and it goes without saying that the configuration of each part including the temperature controller such as the heater and the cooling pipe can be changed in various ways.

Furthermore, although the above-mentioned embodiment shows an example in which changes in the reduction ratio due to changes in atmospheric pressure are dealt with, the present invention can be similarly applied to changes in the reduction ratio due to environmental temperature, environmental humidity, and the like.

〔Effect of the invention〕

As described above, in the present invention, a temperature controller is provided on the wafer stage of a projection exposure apparatus, and the temperature of the wafer is controlled in accordance with changes in the reduction ratio of the projection exposure apparatus. , can be offset by thermal contraction, and pattern transfer can always be achieved at a predetermined reduction ratio regardless of changes in the environment, which is particularly effective for highly accurate transfer formation of fine patterns.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the conceptual configuration of an embodiment of the present invention, FIG. 2 is a sectional view of a wafer stage, and FIG. 3 is a diagram showing the correlation between atmospheric pressure and reduction ratio. DESCRIPTION OF SYMBOLS 1... Optical system, 2... Wafer stage, 3... Control system, 11... Light source, 12... Condenser lens,
13... Imaging lens, 21... Base, 22... Adsorption hole, 23... Heater, 24... Heater controller, 25... Cooling pipe, 26... Flow rate control pulp, 27...Thermocouple, 31...Microcomputer, 32...Barometer, M...Photomask (
reticle), W... semiconductor wafer (silicon wafer)
. Figure 1

Claims (1)

[Claims] 1. In a projection exposure apparatus that projects and transfers a pattern of a photomask or the like onto a wafer supported on a wafer stage using an optical system, the wafer stage is provided with a temperature controller, and the optical system is equipped with a temperature controller. A projection exposure apparatus characterized in that the temperature controller is controlled in response to changes in the reduction ratio, and the temperature of the wafer during exposure can be varied and adjusted. 2. The temperature controller has a heater and a cooling pipe provided on the wafer stage, and the current and cooling medium flowing through these heaters and cooling pipes are controlled based on fluctuations in atmospheric pressure, as claimed in claim 1. The projection exposure apparatus described.