JP3658846B2 - Projection exposure equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection exposure apparatus used for manufacturing a semiconductor integrated circuit and a liquid crystal display.
[0002]
[Prior art]
In a photolithography process for manufacturing a semiconductor element, a liquid crystal display element, a thin film magnetic head, etc., a wafer or a glass plate or the like coated with a photosensitive agent such as a photoresist on a pattern formed on a photomask or a reticle (hereinafter referred to as a reticle) Projection exposure is performed on the photosensitive substrate.
[0003]
As an apparatus for performing this projection exposure, the pattern formed on the reticle is exposed to a predetermined area of the photosensitive substrate held on the substrate stage, and then the reticle stage is exposed again by stepping the substrate stage by a certain distance. A so-called step-and-repeat type projection exposure apparatus is often used. As another type of exposure apparatus, a slit / scan type exposure apparatus that exposes a reticle pattern onto a photosensitive substrate while scanning the reticle and the photosensitive substrate relatively synchronously with respect to a rectangular or arcuate illumination area. Projection exposure apparatuses are also known.
[0004]
The pattern exposure on the photosensitive substrate is usually performed by repeating a plurality of times by exposing another pattern on the already formed pattern. In recent years, patterns formed on a photosensitive substrate have been increasingly miniaturized, and accordingly, the requirements for pattern overlay accuracy have become increasingly severe. One factor affecting the pattern overlay accuracy is the magnification error of the projection lens. The magnification of the projection lens is adjusted when the apparatus 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 exposed to exposure light for a long time or 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. If the reticle also absorbs exposure light and rises in temperature, it may be deformed and cause pattern deviation.
[0005]
Therefore, in order to perform overlay exposure with high accuracy, it is necessary to control the temperature and keep the temperature in the chamber containing the projection exposure apparatus as constant as possible. For this reason, resistor temperature sensors are arranged in the main part of the chamber, for example, the air outlet of the air conditioner, the vicinity of the stage interferometer for measuring the two-dimensional position of the substrate stage, or the projection lens, and output from these temperature sensors. Temperature control in the chamber was performed using temperature information.
[0006]
[Problems to be solved by the invention]
According to the conventional method using a temperature sensor, only a few points of temperature information in the chamber can be obtained. If temperature information for the entire chamber is to be obtained, a large number of temperature sensors must be distributed in the chamber, which is not cost effective. Therefore, since the temperature distribution of the entire chamber cannot be known, the temperature in the chamber cannot be homogenized, and a temperature gradient exists, so that convection occurs and air fluctuation occurs.
[0007]
The present invention has been made in view of such problems of the prior art, and aims to detect the temperature distribution in the chamber without using a large number of temperature sensors and to homogenize the temperature in the chamber. To do.
[0008]
[Means for Solving the Problems]
In the present invention, the inside of the chamber is imaged using a two-dimensional imaging device such as an infrared camera, and the obtained image is processed to obtain a thermograph (temperature distribution diagram) in the chamber. The object is achieved by performing temperature control such as air conditioning control.
[0009]
That is, a projection exposure apparatus according to the present invention includes a substrate stage on which a photosensitive substrate is placed and movable in a two-dimensional direction, a laser interferometer for detecting the two-dimensional position of the substrate stage, and a reticle on which the reticle is placed. A stage, 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 the substrate stage, a chamber that surrounds the apparatus, and an image of the inside of the chamber An infrared imaging means and a temperature control means for obtaining a temperature distribution in the chamber from an output image of the infrared imaging means, and performing temperature control by the temperature control means so that the temperature in the chamber becomes substantially uniform. And
[0010]
By disposing infrared imaging means at several locations in the chamber, it becomes possible to instantaneously measure the temperature distribution in the entire chamber interior, and to efficiently homogenize the temperature distribution. The temperature of the part that becomes the blind spot of the infrared imaging means is a temperature distribution in the chamber by a small number of temperature measuring means by arranging a conventional temperature sensor at that position and using the infrared imaging means and the conventional temperature sensor together Can know more accurately.
[0011]
The temperature control means is at least one of 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 optical path air conditioning temperature of the laser interferometer Desirably, all the temperatures are controlled by controlling the temperature and flow rate of the air blown from the partial air conditioner provided in each part, or by controlling the temperature and flow rate of the fluid flowing through the device part to be temperature controlled Is done by.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a schematic view for explaining the arrangement in a chamber of a projection exposure apparatus according to the present invention. The projection optical system 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 to be a light beam having a uniform intensity distribution by an 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. The illuminated reticle 14 is illuminated 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.
[0013]
The wafer stage 19 has a known structure in which a pair of blocks that can move in directions orthogonal to each other within a plane perpendicular to the optical axis AX of the projection optical system 16 are stacked, and is driven by a driving unit 22. 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 measured value. Adjusted. The alignment of the reticle 14 and the wafer 17 is performed using the alignment system 23 or the like. The reticle transport unit 31 exchanges the reticle 14. The wafers are stored in a cassette 32, and are taken out one by one by the wafer transfer unit 33, and are sequentially placed on the wafer stage 19 and exposed.
[0014]
The entire apparatus is disposed in the chamber 40, and the air circulating in the chamber 40 is air-conditioned at a constant temperature by the main air conditioner 51. In addition, the temperature of the heat generating part in the apparatus or the place where temperature control needs to be performed with high accuracy is individually controlled by a method such as partial air conditioning or 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 that may be heated by absorption of exposure light circulates a liquid at a predetermined temperature. The temperature is controlled to a constant temperature by the temperature adjustment units 53, 54, and 55. In this example, the projection optical system 16 is divided into three parts: an upper part 16 a, an intermediate part 16 b, and a lower part 16 c, and the upper part 16 a of the projection optical system is provided in the first temperature adjustment part 53 and the second temperature adjustment part 54. The projection optical system is temperature-controlled with high accuracy by causing the intermediate portion 16b and the third temperature adjustment portion 55 to share the lower portion 16c. The temperature of the optical path of the laser interferometer 21 that measures the position of the wafer stage 19 is controlled by the air blown from the partial air conditioner 56, and the wafer holder 18 that fixes the wafer 17 circulates a liquid at a predetermined temperature. The temperature control unit 57 controls the temperature. The alignment system 23 is also temperature-controlled by a temperature adjusting unit 58 that circulates the place where the predetermined temperature has occurred.
[0015]
Note that the illumination system including the light source 10 that generates a large amount of heat is housed in a separate chamber 41 independent of the chamber 40, and temperature control is performed in a separate system, so that the heat generated in the illumination system is directly Inflow into the chamber 40 is prevented.
[0016]
FIG. 2 is a conceptual diagram of a partial air conditioner 56 that air-conditions the optical path of the laser interferometer. The partial air conditioner 56 includes a duct 90 that guides outside air or air circulating in the chamber 40, a heater 91 that heats the air circulating in the duct, and an on-off valve 92, and is blown out from the outlet of the partial air conditioner 56. The temperature and flow rate of air can be adjusted. A 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, and 58 that control the temperature by circulating the liquid can adjust the temperature and flow rate of the liquid to be circulated by a heater or a flow control valve. In addition, 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.
[0017]
A plurality of infrared imaging devices 61, 62,... Are arranged in the chamber 40, and each part of the devices arranged in the chamber is photographed constantly or at regular intervals. The plurality of infrared imaging devices are preferably arranged so as to cover the entire interior of the chamber 40. Images captured by the infrared imaging devices 61, 62, and 63 are input to the image processing device 71 and processed as shown in FIG. In the image processing apparatus 71, a distribution map of infrared intensity is created from an image obtained by photographing each part of the apparatus arranged in the chamber 40 by a known method, and converted into a temperature distribution chart (thermograph). When there is a place where the infrared imaging devices 61, 62, and 63 are blind spots in the chamber 40, the resistor temperature sensors 66 and 67 are arranged at the places and the data obtained from the temperature sensors 66 and 67 are taken into consideration. Thus, temperature distribution data of the entire chamber can be obtained.
[0018]
The main controller 72 obtains the temperature of each part in the chamber 40 from the data of the thermograph obtained by the image processing device 71, and the partial air conditioner 52, which is necessary for making the temperature distribution uniform and eliminating the temperature gradient. 56 or temperature control parameters of the temperature adjusting units 53, 54, 55, 57, and 58 by liquid circulation are calculated. The calculation of the temperature control parameter can be performed by PID calculation. Finally, the valve opening degree of the partial air conditioners 52 and 56, the data of the heater (or heat pump) current, and the temperature adjustment units 53, 54, 55, 57, 58 is converted into the temperature adjustment heater (or heat pump) current of the liquid circulated and the opening degree data of the flow control valve, and supplied to the respective control units 81 to 87.
[0019]
FIG. 4 is a conceptual diagram of an example of a thermograph obtained by processing an 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 hatching density, and the portion where the hatching density is high indicates that the temperature is high. This figure shows that the upper part of the projection optical system 16 is hotter than the middle part and the lower part. In this case, although depending on the temperature distribution in the part other than the projection optical system 16, the main controller 72 generally supplies the second temperature adjustment unit 84 that controls the first temperature adjustment unit 53 to the second temperature adjustment unit 84. In addition, the temperature control units 85 and 86 that control the third temperature control units 54 and 55 are instructed to circulate a liquid having a lower temperature than that. The thermograph as shown in FIG. 4 obtained by processing by the image processing device 71 may be displayed on a monitor so that the operator can observe it if necessary.
[0020]
The main air-conditioning control unit 81 controls the heater (or heat pump) current of the air-conditioning apparatus 51 and the opening degree of the on-off valve in accordance with a command from the main control apparatus 72. Similarly, the reticle partial air conditioning control unit 82 and the laser interferometer optical path air conditioning control unit 83 blow air to the optical path of the partial air conditioner 52 and the laser interferometer 21 that respectively blow air to the reticle 14 in accordance with a command 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. Further, the wafer holder temperature adjustment unit 87 controls the temperature adjustment unit 57 in accordance with a command from the main controller 72, and controls the temperature and flow rate of the liquid circulated through the wafer holder 18. By sequentially performing these series of procedures and controlling the circulation, the temperature distribution in the chamber 40 is homogenized. By changing the focus of the infrared imaging devices 61, 62, and 63, a pseudo three-dimensional temperature distribution can be obtained, and air conditioning control with higher accuracy is possible.
The present invention can also be used for searching a heat source at the time of apparatus adjustment, and in that case, the adjustment time can be shortened as compared with the prior art.
[0021]
【The invention's effect】
According to the present invention, the temperature distribution in the chamber can be homogenized, the influence of air fluctuations can be reduced, and the exposure accuracy can be improved.
[Brief description of the 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]
DESCRIPTION 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 ... Movement Mirror, 21 ... Laser interferometer, 22 ... Driving means, 23 ... Alignment microscope, 31 ... Reticle transfer section, 32 ... Cassette, 33 ... Wafer transfer section, 40, 41 ... Chamber, 51 ... Main air conditioner, 52, 56 ... Partial air conditioner, 53, 54, 55, 57, 58 ... temperature adjusting unit, 61, 62, 63 ... infrared imaging device, 66, 67 ... temperature sensor, 71 ... image processing device, 72 ... main control device, 81 ... main Air conditioning control unit, 82 ... reticle partial air conditioning control unit, 83 ... laser interferometer optical path air conditioning control unit, 84, 85, 86 ... projection optical system temperature adjustment unit, 7 ... the wafer holder temperature control unit

Claims (5)

  A substrate stage on which a photosensitive substrate is placed and movable in a two-dimensional direction, a laser interferometer for detecting a two-dimensional position of the substrate stage, a reticle stage on which a reticle is placed, and light from a light source An illumination system that is incident on a 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 infrared imaging means that images the interior of the chamber And a temperature control means, wherein a temperature distribution in the chamber is obtained from an output image of the infrared imaging means, and the temperature control means controls the temperature so that the temperature in the chamber becomes substantially uniform. Projection exposure apparatus.   The temperature control means includes a temperature of the atmosphere circulating in the chamber, a temperature of the reticle, a temperature of the projection optical system, a temperature of the photosensitive substrate placed on the substrate stage, or an optical path air conditioner of the laser interferometer 2. The projection exposure apparatus according to claim 1, wherein at least one of the temperatures is controlled.   The said temperature control means controls the temperature and flow volume of the fluid which distribute | circulates the temperature and flow volume of the gas which blow off from an air-conditioning blowing part, and the predetermined part which should be temperature-controlled. The projection exposure apparatus described. 4. The projection according to claim 1, further comprising a temperature sensor disposed in the chamber, wherein the temperature distribution in the chamber is acquired based on data obtained from the temperature sensor. 5. Exposure device. 5. The projection exposure apparatus according to claim 1, further comprising means for generating a temperature distribution diagram in the chamber based on an output image of the infrared imaging means and outputting the monitor.

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