JPH09260262A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform the temperature in a chamber by detecing the temperature distribution in the chamber. SOLUTION: The inside of a chamber 40 is image-sensed by using two-dimensional image sensing equipments 61, 62 such as infrared cameras. By processing the obtained image, a thermograph (temperature distribution figure) in the chamber is obtained. On the basis of the thermograph, the temperature and the flow rate of partial air-conditioning or the like of each part in the chamber are controlled to be optimum. As to temperature control, the temperature of atmosphere circulating in the chamber is wholly controlled by an air-conditioning equipment 51. Temperatures of parts, such as the temperatures of a reticle 14, projection optical system 16 and a wafer 17, and the optical path air- conditioning temperature of a laser interferometer 21 are controlled by using partial air-conditioning equipments 52, 56 and temperature adjusting parts 53, 54, 55, 57 which circulate liquid.

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 used for manufacturing semiconductor integrated circuits and liquid crystal displays.

[0002]

2. Description of the Related Art In a photolithography process for manufacturing semiconductor devices, liquid crystal display devices, thin film magnetic heads, etc., a pattern formed on a photomask or reticle (hereinafter referred to as reticle) is coated with a photosensitizer such as photoresist. Projection exposure is performed on a photosensitive substrate such as a wafer or a glass plate.

As an apparatus for performing this projection exposure, a pattern formed on a reticle is exposed on a predetermined area of a photosensitive substrate held on a substrate stage, and then the substrate stage is stepped a fixed distance to re-pattern the reticle. A so-called step-and-repeat type projection exposure apparatus that repeats exposure is often used.
Further, as another type of exposure apparatus, there is a slit scan type exposure apparatus which exposes a reticle pattern onto a photosensitive substrate while relatively synchronously scanning the reticle and the photosensitive substrate with respect to a rectangular or arcuate illumination area. Projection exposure devices are also known.

The pattern exposure on the photosensitive substrate is usually carried out by repeating another exposure by superposing another pattern on the already formed pattern a plurality of times. In recent years, the pattern formed on the photosensitive substrate is becoming more and more miniaturized, and accordingly, the requirement for the pattern overlay accuracy is becoming more and more strict. One of the factors that influence the pattern overlay accuracy is a projection lens magnification error. The magnification of the projection lens is adjusted when the device is installed. However, the projection lens absorbs a part of the exposure energy during exposure and the temperature rises. Therefore, if the projection lens is continuously irradiated with the exposure light for a long time or if the exposure operation is continuously performed for a long time, the temperature may change and the magnification may change to a level that cannot be ignored. When the reticle also absorbs the exposure light and rises in temperature, it may deform and cause a pattern shift.

Therefore, in order to perform overlay exposure with high accuracy, it is necessary to control the temperature and keep the temperature in the chamber accommodating the projection exposure apparatus as constant as possible. Therefore, a resistor temperature sensor is arranged in a main part of the chamber, for example, an air outlet of an air conditioner, a stage interferometer for measuring the two-dimensional position of the substrate stage, or a projection lens, and the temperature is output from these temperature sensors. The temperature inside the chamber was controlled using the temperature information.

[0006]

According to the conventional method using a temperature sensor, it is possible to obtain temperature information of only a few points in the chamber. If temperature information of the entire chamber is to be obtained, a large number of temperature sensors must be dispersed and arranged in the chamber, which is costly. Therefore, since the temperature distribution of the entire chamber cannot be known, the temperature inside the chamber cannot be homogenized, and since there is a temperature gradient, convection occurs and air fluctuation occurs.

The present invention has been made in view of the above problems of the prior art, and it is possible to detect the temperature distribution in the chamber and homogenize the temperature in the chamber without using many temperature sensors. With the goal.

[0008]

In the present invention, a thermograph (temperature distribution chart) in the chamber is obtained by imaging the inside of the chamber using a two-dimensional imaging device such as an infrared camera and processing the obtained image. The temperature control such as air-conditioning control of each part in the chamber is performed based on the above, and the above-mentioned object is achieved.

That is, the projection exposure apparatus according to the present invention is
A substrate stage on which a photosensitive substrate is placed and movable in two dimensions, a laser interferometer for detecting the two-dimensional position of the substrate stage, a reticle stage on which a reticle is placed,
An illumination system that allows light from a light source to enter the reticle, a projection optical system that forms an image of the reticle on a photosensitive substrate placed on a substrate stage, a chamber that surrounds the device, and infrared imaging that captures the inside of the chamber. And a temperature control unit, the temperature distribution in the chamber is obtained from the output image of the infrared imaging unit, and the temperature control unit controls the temperature so that the temperature in the chamber becomes substantially uniform.

By arranging the infrared imaging means at several places in the chamber, the temperature distribution in the entire chamber can be measured instantaneously, and the temperature distribution can be efficiently homogenized. For the temperature of the blind spot of the infrared imaging means, a conventional temperature sensor is placed at that position, and by using both the infrared imaging means and the conventional temperature sensor, the temperature distribution inside the chamber can be reduced by a small number of temperature measuring means. You can know more accurately.

The temperature control means is at least the temperature of the atmosphere circulating in the chamber, the temperature of the reticle, the temperature of the projection optical system, the temperature of the photosensitive substrate placed on the substrate stage, or the temperature of the optical path of the laser interferometer. One temperature, preferably all temperatures, is controlled by controlling the temperature and flow rate of the air blown out from the partial air conditioners provided in the respective parts, or the temperature and flow rate of the fluid that is circulated to the device part whose temperature is to be controlled. Is done by controlling.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic diagram for explaining the arrangement in the chamber of the projection exposure apparatus according to the present invention. The projection optical system main body includes a light source 10, an optical system 12, a reticle 14, a projection optical system 16, a wafer stage 19 and the like. The exposure light emitted from the light source 10 is reflected by the reflection mirror 11, is made into a light flux having a uniform intensity distribution by the optical system 12 such as a fly-eye integrator, and the optical path is bent by the reflection mirror 13 and held on the reticle stage 15. Reticle 1
Illuminate 4 uniformly. The pattern formed on the reticle 14 is imaged on the wafer 17 held by being attracted to the wafer holder 18 on the wafer stage 19 via the projection optical system 16.

The wafer stage 19 has a well-known structure in which a pair of blocks movable in directions orthogonal to each other in a plane perpendicular to the optical axis AX of the projection optical system 16 are stacked, and is driven by a driving means 22. It The position of the wafer stage 19 is detected by measuring the distance between the movable mirrors 20 fixed on the wafer stage 19 with a laser interferometer 21, and the two-dimensional position of the wafer 17 is determined based on this measurement value. Adjusted. The alignment between the reticle 14 and the wafer 17 is performed using the alignment system 23 or the like. The reticle transport unit 31 replaces the reticle 14.
The wafers are stored in the cassette 32, taken out one by one by the wafer transfer unit 33, sequentially placed on the wafer stage 19, and exposed.

The entire apparatus is placed in the chamber 40,
The air circulating in the chamber 40 is conditioned to a constant temperature by the main air conditioner 51. In addition, the temperature of the heat generating portion in the device or the portion that requires highly accurate temperature control is individually controlled by methods such as partial air conditioning and liquid circulation. That is, the temperature of the reticle 14 exposed to the illumination light is controlled by the air blown out from the partial air conditioner 52, and the projection optical system 16, which may be heated by the absorption of the exposure light, circulates the liquid having a predetermined temperature. The temperature is controlled to a constant temperature by the temperature adjusting units 53, 54, 55. In this example, the projection optical system 16 is divided into three parts, that is, an upper part 16a, an intermediate part 16b, and a lower part 16c, and the first temperature adjusting part 53 includes an upper part 16a of the projection optical system.
The temperature of the projection optical system is controlled with high accuracy by making the second temperature adjusting section 54 share the intermediate section 16b and the third temperature adjusting section 55 share the lower section 16c. Further, the optical path of the laser interferometer 21 that measures the position of the wafer stage 19 is temperature-controlled by the air blown from the partial air conditioner 56, and the wafer holder 18 that fixes the wafer 17 is fixed.
Is a fourth temperature adjusting unit 57 that circulates a liquid having a predetermined temperature.
The temperature is controlled by. The alignment system 23 also
The temperature is controlled by a temperature adjusting unit 58 that circulates the place where the predetermined temperature occurs.

The illumination system including the light source 10 that generates a large amount of heat is housed in a chamber 41 that is independent of the chamber 40, and the temperature is controlled by another system. The heat is prevented from flowing directly into the chamber 40.

FIG. 2 is a conceptual diagram of a partial air conditioner 56 for air conditioning the optical path of the laser interferometer. The partial air conditioner 56 is
A duct 90 for guiding outside air or air circulating in the chamber 40, a heater 91 for heating the air circulating in the duct, and an opening / closing valve 92 are provided to control the temperature and flow rate of the air blown from the blowout port of the partial air conditioner 56. It can be adjusted. The partial air conditioner 52 that partially air-conditions the reticle 14 has the same structure, and blows air whose temperature and flow rate are adjusted to the reticle 14. The temperature adjusting units 53, 54, 55, 57, 58, which circulate the liquid to control the temperature, can adjust the temperature and flow rate of the liquid circulated by a heater or a flow rate control valve. It is also possible to install a heat pump instead of the heater so that cooling control can be performed in addition to heating control.

A plurality of infrared image pickup devices 61, 62, ... Are arranged in the chamber 40, and each part of the device arranged inside the chamber is photographed constantly or at regular intervals. It is preferable that the plurality of infrared imaging devices be arranged so as to cover the entire interior of the chamber 40. The images captured by the infrared imaging devices 61, 62, 63 are input to the image processing device 71 and processed as shown in FIG. In the image processing device 71, an infrared intensity distribution map is created from an image obtained by photographing each part of the device arranged in the chamber 40 by a known method and converted into a temperature distribution map (thermograph). Infrared imaging devices 61 and 6 are provided in the chamber 40.
If there is a blind spot of 2,63, the resistor temperature sensors 66 and 67 are placed at that spot, and the data obtained from the temperature sensors 66 and 67 are taken into account to obtain the temperature distribution data of the entire chamber. Can be obtained.

The main control unit 72 obtains the temperature of each portion in the chamber 40 from the thermograph data obtained by the image processing unit 71, and the partial air conditioning necessary to make the temperature distribution uniform and eliminate the temperature gradient. Device 52, 56 or temperature control unit 53, 54, 55, 57, 58 by liquid circulation
The temperature control parameter of is calculated. The calculation of the temperature control parameter can be performed by PID calculation, and finally, the data of the valve opening degree of the partial air conditioners 52 and 56, the heater (or heat pump) current, and the temperature adjusting units 53 and 5 are obtained.
It is converted into heater (or heat pump) current for adjusting the temperature of the liquid circulated by 4, 55, 57 and 58 and opening degree data of the flow rate control valve, and is supplied to each control unit 81 to 87.

FIG. 4 is a conceptual diagram of an example of a thermograph obtained by processing the image of the projection optical system 16 imaged by the infrared imaging device 61 by the image processing device 71. The temperature is represented by the density of hatching, and the high hatching density indicates that the temperature is high. This figure shows that the upper part of the projection optical system 16 has a higher temperature than the middle part and the lower part. In this case, although it depends on the temperature distribution in the portion other than the projection optical system 16, in general, the main controller 72 causes the temperature adjusting unit 84 for controlling the first temperature adjusting unit 53 to provide the second temperature adjusting unit 84. And temperature adjustment units 85, 8 for controlling the third temperature control units 54, 55
6 will be commanded to circulate a lower temperature liquid. The thermograph as shown in FIG. 4 processed by the image processing device 71 may be displayed on a monitor so that the operator can observe it if necessary.

The main air-conditioning control unit 81 is the main control unit 7
The heater (or heat pump) current of the air conditioner 51 and the opening degree of the opening / closing valve are controlled according to the command from 2. Similarly, the reticle partial air-conditioning control unit 82 and the laser interferometer optical path air-conditioning control unit 83 blow air on the optical paths of the partial air-conditioning unit 52 and the laser interferometer 21 that blow air on the reticle 14, respectively, in accordance with commands from the main controller 72. The heater (or heat pump) current of the partial air conditioner 56 and the opening degree of the on-off valve are controlled. The wafer holder temperature adjusting unit 87 also controls the temperature adjusting unit 57 in accordance with a command from the main controller 72 to control the temperature and flow rate of the liquid circulated in the wafer holder 18. By sequentially performing these series of procedures and controlling circulation, the temperature distribution in the chamber 40 is homogenized. By changing the focus of the infrared imaging devices 61, 62, 63, a pseudo three-dimensional temperature distribution can be obtained, and more accurate air conditioning control becomes possible. Further, the present invention can be used for a heat source search or the like at the time of adjusting the device, and in that case, the adjustment time can be shortened as compared with the conventional case.

[0021]

According to the present invention, the temperature distribution in the chamber can be made uniform, the influence of air fluctuations can be reduced, and the exposure accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating an arrangement in a chamber of a projection exposure apparatus according to the present invention.

FIG. 2 is a conceptual diagram of a partial air conditioner that air-conditions an optical path of a laser interferometer.

FIG. 3 is a schematic diagram of a control system.

FIG. 4 is a conceptual diagram showing an example of a thermograph obtained by photographing a projection optical system.

[Explanation of symbols]

10 ... Light source, 11 ... Reflection mirror, 12 ... Optical system, 13 ...
Reflection mirror, 14 ... Reticle, 15 ... Reticle stage, 16 ... Projection optical system, 17 ... Wafer, 18 ... Wafer holder, 19 ... Wafer stage, 20 ... Moving mirror, 21 ... Laser interferometer, 22 ... Driving means, 23 ... Alignment Microscope, 31 ... Reticle transfer part, 32 ... Cassette, 33 ... Wafer transfer part, 40, 41 ... Chamber, 51 ... Main air conditioner, 52, 56 ... Partial air conditioner, 53, 54, 55, 5
7, 58 ... Temperature adjusting part, 61, 62, 63 ... Infrared imaging device, 66, 67 ... Temperature sensor, 71 ... Image processing device, 72 ... Main control device, 81 ... Main air conditioning control unit, 8
2 ... Reticle partial air conditioning control unit, 83 ... Laser interferometer optical path air conditioning control unit, 84, 85, 86 ... Projection optical system temperature adjustment unit, 87 ... Wafer holder temperature adjustment unit

Claims (3)

[Claims] 1. A substrate stage on which a photosensitive substrate is placed and is movable in two dimensions, a laser interferometer for detecting the two-dimensional position of the substrate stage, a reticle stage on which a reticle is placed, and a light source. An illumination system that makes light from the device incident on the reticle, a projection optical system that forms an image of the reticle on a photosensitive substrate placed on the substrate stage, a chamber that surrounds the apparatus, and an image inside the chamber. Infrared image pickup means and temperature control means are provided, the temperature distribution in the chamber is obtained from the output image of the infrared image pickup means, and the temperature control means controls the temperature so that the temperature in the chamber becomes substantially uniform. A projection exposure apparatus characterized by the above. 2. The temperature control means, the temperature of the atmosphere circulating in the chamber, the temperature of the reticle, the temperature of the projection optical system, the temperature of the photosensitive substrate mounted on the substrate stage, or the laser. The projection exposure apparatus according to claim 1, wherein at least one of the optical path air-conditioning temperatures of the interferometer is controlled. 3. The temperature control means controls the temperature and flow rate of the gas blown out from the air-conditioning blow-out part and the temperature and flow rate of the fluid flowing to a predetermined portion where temperature control is to be performed. The projection exposure apparatus according to claim 1 or 2.