JPH1126363A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the decrease in the measuring accuracy of an interferometer due to temperature control of a motor for driving a stage. SOLUTION: The temperatures of motors 22A, 22B, etc., are controlled via a liquid-cooling unit 54 by a control unit 50 on the basis of air-conditioned temperatures close to a wafer stage 18 measured by a temperature sensor 42. Thereby the temperatures of the motors can be controlled, so that the air- conditioned temperatures close to a wafer stage 18 is almost the same at the surface temperatures of the motors. As a result, the movement of the wafer stage 18 hardly generates fluctuations of air over a length-measuring axis (optical path of interferometer beam) of an interferometer 32X, etc. Thus this can suppress the decrease in the measuring accuracy of the interferometer due to the temperature control of the motors 22A, 22B for driving the stage and so on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure apparatus, and more particularly, to an exposure apparatus suitable for use in a photolithography process in manufacturing a semiconductor integrated circuit, a liquid crystal display substrate, and the like.

[0002]

2. Description of the Related Art Generally, an exposure apparatus used for manufacturing a semiconductor circuit, particularly, an ultra-large scale integration (Large Scale Integration) or a liquid crystal circuit having a high degree of integration has a very high precision temperature control and high cleanliness. Degree is required. For this reason, the entire exposure main body for performing the exposure is usually installed in a chamber, and air whose temperature is adjusted in a machine room in which a heat exchanger is built is blown by a blower and supplied. A ULPA filter (Ultr filter) is provided at the air supply port in the chamber.
a Low Penetration Air-filter) is provided to remove dust and supply the dust into the chamber. Most of the air supplied from the machine room into the chamber is returned to the machine room again from the viewpoint of temperature controllability, and is circulated.

As a conventional exposure apparatus used for manufacturing the semiconductor integrated circuit, a step-and-repeat type reduction projection exposure apparatus (stepper) has been mainly used. Accordingly, recently, a step-and-scan type scanning exposure apparatus capable of performing a large-area exposure with a small projection optical system has been relatively frequently used.

In these exposure apparatuses, the wafer stage is moved in the XY two-dimensional directions because it is necessary to sequentially expose a plurality of shot areas on a substrate such as a wafer or a glass plate (hereinafter collectively referred to as a "wafer"). The position of the wafer stage is measured by a high-precision measuring device such as a laser interferometer with a resolution of, for example, several nm to 10 nm. As a drive system of the wafer stage, a drive system including a stepping motor (servo motor) and a feed screw has been used, but a linear motor has recently been used relatively frequently.

Further, in an exposure apparatus such as a stepper, since it is necessary to expose a plurality of circuit patterns in a superimposed manner with high precision, a pattern of a mask or a reticle (hereinafter collectively referred to as a “reticle”) and a shot area on a wafer are required. Is required as well as a highly accurate positioning capability between the shot area and the image plane of the projection optical system. In particular, recently, with the miniaturization of patterns, projection optical systems having a large numerical aperture (NA) have come to be used, so that the depth of focus of the projection optical system tends to be shallow, and the In order to match the area within the depth of focus of the projection optical system, it has been necessary to detect the position of the wafer in the optical axis direction with high accuracy. For this reason, this type of exposure apparatus is usually provided with a focus detection system such as an oblique incident light type.

Since the heat generated by the motor for driving the wafer stage, particularly the linear motor for driving the wafer stage at a high speed, may adversely affect the temperature control accuracy in the chamber, the conventional exposure apparatus is also required. The liquid cooling of the motor was performed.

Further, since the wafer is thermally expanded by irradiation of the exposure light to the wafer, from the viewpoint of preventing the thermal expansion, cooling (temperature adjustment) of a wafer holder or a wafer stage portion holding the wafer is also performed.

Further, if the refractive index of the internal air changes due to a change in the temperature in the chamber, an error may occur in the measured value of the interferometer. In recent exposure apparatuses, partial temperature control for controlling the temperature within a predetermined temperature range is also performed.

[0009]

However, in the above-described liquid cooling (temperature adjustment) of the motor of the prior art, the cooling of the motor (mainly the surface temperature) is performed without deciding how much to cool. Therefore, undesirable phenomena such as excessive temperature adjustment (cooling) and excessive temperature adjustment (cooling) often occur. Therefore, in any case, a temperature difference occurs between the vicinity of the motor and other portions in the chamber, and as a result, a temperature fluctuation (air fluctuation) occurs in the chamber as the wafer stage moves, There is a disadvantage that this air fluctuation causes an error in the measured value of the interferometer.

With respect to the temperature adjustment of the wafer holder and the like of the prior art described above, the accuracy of the temperature adjustment has been determined from the viewpoint of expansion and contraction of the wafer during exposure. For this reason, in order to suppress expansion and contraction of the wafer, particularly thermal expansion, there is a tendency of overcooling, and the temperature of the wafer surface is low and the temperature of the projection optical system portion is high. There is a possibility that air fluctuations occur in the space between the projection optical system and the detection accuracy of the above-described focus detection system that detects the position of the wafer surface.

The present invention has been made under such circumstances, and an object of the present invention is to suppress a decrease in measurement accuracy of an interferometer due to temperature adjustment of a motor for driving a stage. It is an object of the present invention to provide an exposure apparatus capable of performing the above.

It is another object of the present invention to suppress a decrease in detection accuracy of a focus detection system due to temperature adjustment of a holding member (holder or stage) for holding a substrate. An exposure apparatus is provided.

[0013]

According to a first aspect of the present invention, there is provided a substrate stage (18) for holding and moving a substrate (W) to be exposed, and a motor (20A) for driving the substrate stage (18). 20B, 22A, 22B) and an interferometer (32X, 32Y) for measuring the position of the substrate stage, a temperature for controlling the temperature of the motor based on the air-conditioning temperature of the substrate stage. An adjusting means (50) is provided.

According to this, since the temperature of the motor is controlled by the temperature adjusting means based on the air-conditioning temperature of the substrate stage, the air-conditioning temperature of the substrate stage and the surface temperature of the motor are made substantially the same. The temperature of the motor can be controlled. For this reason, even if the substrate stage moves, air fluctuation hardly occurs on the length measurement axis of the interferometer (the optical path of the interferometer beam). Therefore, it is possible to suppress a decrease in the measurement accuracy of the interferometer due to the temperature adjustment of the motor for driving the stage. Further, since neither excessive cooling nor excessive cooling of the motor occurs, efficient temperature adjustment is possible.

In this case, the temperature adjusting means may control the temperature of the motor so that the motor surface temperature and the air-conditioning temperature of the substrate stage are substantially the same, but this is not always necessary. As described in Item 2, the temperature adjusting means (50) is provided with the motor (20).
A, 20B, 22A, 22B) may be controlled to be within the aforementioned air conditioning temperature + 1 degree. The inventor has confirmed through experiments that even in the case of a linear motor, when the surface temperature of the motor is set within the air conditioning temperature of the substrate stage portion + 1 ° C, the measurement error due to air fluctuation of the interferometer can be suppressed to 3 nm or less.

According to a third aspect of the present invention, there is provided a holding member (28) for holding a substrate (W) to be exposed, and a projection optical system (P) for projecting and exposing a mask pattern on the substrate to be exposed.
L) and a focus detection system (40) that measures the position of the substrate to be exposed in the optical axis direction of the projection optical system. Temperature control means (5) for controlling the temperature within a temperature range determined according to the detection accuracy required for the focus detection system with reference to
0) is provided.

According to this, the temperature adjusting means increases the temperature rise of the holding member for holding the substrate to be exposed within a temperature range determined according to the detection accuracy required of the focus detection system based on the steady state before exposure. Is controlled, it is possible to suppress the temperature rise of the substrate holding member from a steady state before exposure to a temperature range that does not affect the detection accuracy required for the focus detection system. Therefore, it is possible to suppress a decrease in the detection accuracy of the focus detection system due to the temperature adjustment of the holding member (holder or stage) holding the substrate. Further, since neither excessive cooling nor excessive cooling of the holding member occurs, efficient temperature adjustment is possible.

In this case, the temperature adjusting means may perform control to keep the temperature of the holding member substantially at the temperature in a steady state before exposure, but this is not always necessary. As in the invention described above, the temperature adjusting means (50) may control the amount of temperature rise of the holding member (28) to 0.3 degrees or less from a steady state temperature before exposure. When the inventor controls the holder as a holding member to a temperature of 0.3 ° C. or less from the above-described steady state before the exposure, the detection error caused by air fluctuation of the focus detection system is reduced by 3%.
It was confirmed that it could be suppressed to 0 nm or less.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
3 will be described with reference to FIG.

FIG. 1 shows an exposure apparatus 10 according to one embodiment.
Of the main part is shown. In the exposure apparatus 10, the temperature of the exposure apparatus main body 14 installed in the chamber 12 is adjusted in the machine room 16, and the exposure processing is performed in a state where clean air from which dust is removed is supplied. This is because, when the temperature of the constituent members of the exposure apparatus main body 14 changes, the overlay accuracy of the circuit pattern deteriorates. Therefore, it is necessary to control the temperature of the members with, for example, an accuracy within about ± 0.01 ° C. of the target temperature. Because there is. This temperature control is performed in the exposure apparatus 10 by constantly supplying the air whose temperature has been precisely adjusted by the air conditioning unit in the machine room 16 into the chamber 12.

The exposure apparatus main body 14 includes an illumination system (not shown) for irradiating exposure light, a projection optical system PL for projecting a circuit pattern formed on a reticle (not shown) onto a wafer W as a substrate to be exposed, and a wafer W. And a wafer stage 18 as a substrate stage movable in the X-axis direction (the horizontal direction in the paper plane of FIG. 1) and the Y-axis direction (the orthogonal direction in the paper plane of FIG. 1) orthogonal thereto. It has a stage drive system and the like.

The stage drive system includes a pair of X linear motors 20A and 20B disposed in a chamber 12, as shown in FIG. 2 which is a schematic sectional view taken along line AA of FIG.
It is composed of a pair of Y linear motors 22A and 22B. This will be described in more detail.
0A is X near the end of the chamber 12 in the + Y direction in FIG.
The stator 24a is composed of a coil 24a extending in the direction, and a movable element 25a having an inverted U-shaped cross section engaged with the stator 24a from above. A magnet is fixed to a surface of the mover 25a facing the upper surface and both side surfaces of the stator 24a. Similarly, the other X linear motor 20B is also engaged with a stator 24b extending in the X direction near the end of the chamber 12 in the −Y direction of FIG. 2 and the stator 24b from above. Movable element 25 with inverted U-shaped cross section
b.

The one Y linear motor 22A has a stator 26a composed of a coil installed in the Y direction between the movers 25a and 25b, and a cross section engaged with the stator 26a from the −Y direction side. U-shaped mover 27a (see FIG. 1)
It is composed of The stator 26 of the mover 27a
A magnet is fixed to the side opposite to the -X side surface and the upper and lower surfaces of a. Similarly, the other Y linear motor 22B also includes a stator 26b composed of a coil erected in the Y direction between the movers 25a and 25b,
Movable member 2 having a U-shaped cross section engaged with + X direction side to 6b
7b (see FIG. 1).

The pair of movers 27a and 27b are shown in FIG.
As shown in (1), they are arranged at predetermined intervals in the X direction and are respectively fixed to the bottom surface of the wafer stage.

According to the stage drive system configured as described above, the wafer stage 18 is driven in the Y direction by the pair of Y linear motors 22A and 22B, and is driven by the pair of X linear motors 20A and 20B. The wafer stage 18 is driven in the X direction integrally with the linear motors 22A and 22B, and thus the wafer stage 18 can be freely positioned at an arbitrary position in the XY two-dimensional plane. This wafer stage drive system is controlled by a stage control system (not shown).

As shown in FIG. 1, a wafer holder 28 as a holding member is mounted on the upper surface of the wafer stage 18, and the wafer W is held by the wafer holder 28 by vacuum suction or the like. This wafer holder 28
Is configured to be able to be minutely driven within a range of, for example, about 100 μm in a Z direction orthogonal to the XY plane by a Z drive system (not shown).

A movable mirror 30 composed of an L-shaped mirror having a reflecting surface orthogonal to the X direction and a reflecting surface orthogonal to the Y direction is fixed on the upper surface of the wafer stage 18.
A laser interferometer 32X for measuring the position in the X direction is disposed in the chamber 12 so as to face the reflecting surface on the X side of the movable mirror 30. The laser interferometer 32X projects the measurement beam IMx in the X direction to the movable mirror 30, and also fixes the X fixed mirror 34X fixed to the −X direction side surface of the projection optical system PL.
, A reference beam IRx in the X direction is projected onto the X-direction of the wafer stage 18 based on the interference light of each reflected light.
The coordinates are measured at a resolution of, for example, about 10 nm. Similarly, a laser interferometer 32Y for position measurement in the Y direction is arranged in the chamber 12 so as to face the reflecting surface on the Y side of the movable mirror 20 (see FIG. 2). This laser interferometer 32Y
The measurement beam IMy in the Y direction is projected onto the movable mirror 30, and the reference beam in the Y direction is projected onto an X fixed mirror (not shown) fixed to the + Y side surface of the projection optical system PL. The Y coordinate of the wafer stage 18 is measured at a resolution of, for example, about 10 nm based on the interference light of the reflected light. The measurement values of these laser interferometers 32X and 32Y are supplied to a stage control system (not shown).

In the exposure apparatus 10 of the present embodiment, an autofocus unit 40 as a focus detection system is provided beside the projection optical system PL. In the autofocus unit 40, an irradiation optical system that irradiates the surface of the wafer W with the focus detection beam FB from a direction inclined at a predetermined angle with respect to the optical axis direction (Z direction) of the projection optical system PL;
A light receiving optical system for receiving the reflected light of the focus detection beam FB from the surface of the wafer W is housed therein. As a light source of the irradiation optical system, for example, a light source that emits broadband light such as a halogen lamp is used. The autofocus unit 40 uses the fact that the light receiving position of the focus detection beam FB reflected on the wafer surface fluctuates in accordance with the Z direction position of the wafer W surface in principle, and changes the Z direction position of the wafer W. It is to detect. A detection signal from the light receiving optical system of the autofocus unit 40 is supplied to a stage control system (not shown).

The -X in FIGS. 1 and 2 of the chamber 12
An air supply port is provided in the vicinity of the lower end in the direction, and a ULPA for removing dust in the air is provided at the air supply port.
A filter 35 is provided. The air blown into the chamber through the ULPA filter 35 is mainly used for partial temperature control for partially controlling the temperature near the wafer stage 18 and the stage drive system (linear motors 20A, 20B, 22A, 22C). Air conditioning of other portions of the chamber 12 is performed by air supplied through another ULPA filter provided in an upper portion (not shown).

The exhaust port 12b provided at the end in the + X direction of the chamber 12 is actually connected to the machine room 16 via a return duct, but in FIGS. 1 and 2,
The illustration of these return ducts and the like is omitted.

In the machine room 16, a cooling heat exchanger for cooling the air recovered through the return duct to a predetermined temperature, a refrigerator for supplying a refrigerant to the cooling heat exchanger, The air conditioner 52 (see FIG. 3) including a heater for heating the air cooled by the heat exchanger, a blower for forcing the air heated to a predetermined temperature by the heater to the chamber 12 side, and the like (all not shown) is housed. Have been. The air conditioner 52 is controlled by the control device 50 shown in FIG. 1 (this will be described later).

A temperature sensor 42 is provided in front of the ULPA filter 35 in the chamber 12. The temperature sensor 42 measures the temperature of the air in the chamber 12, and outputs the output (temperature information) to the control device 50. Supplied. The control device 50 controls the heating of the heater in the air conditioner 52 based on the temperature information from the temperature sensor 42, and controls the vicinity of the wafer stage 18 in the chamber 12 and the stage drive system (linear motors 20A, 20B, 22A, 22C). A part (hereinafter, abbreviated as “stage part”) is controlled to a preset target temperature (air conditioning temperature).

Further, the exposure apparatus 10 of the present embodiment is provided with a liquid cooling section 54 for cooling the linear motors 20A, 20B, 22A, 22B with a liquid whose temperature has been adjusted to a predetermined temperature. A path through which the cooling liquid sent from the section 54 passes through the stators 24a, 24b, 26a, and 26b constituting the linear motors 20A, 20B, 22A, and 22B and returns to the liquid cooling section (see FIGS. 1 and 2). (See dotted arrow). Also,
As shown in FIG. 3, information of a temperature sensor (not shown) in the liquid cooling unit 54 is fed back to the control device 50.

In the present embodiment, the control device 50
The temperature of the cooling liquid sent from the liquid cooling section 54 is controlled within a predetermined temperature range based on the temperature information from the temperature sensor 42, and the temperature-controlled cooling liquid and the linear motor 20 are controlled.
A, a stator 24a constituting 20B, 22A, 22B,
Heat exchange is performed between the stators 24b, 26a, and 26b, whereby the surface temperatures of the stators 24a, 24b, 26a, and 26b are adjusted to be substantially the same as the air conditioning temperature of the stage. I have.

The exposure apparatus 10 of the present embodiment is provided with a holder temperature detector 56 for detecting the side surface temperature of the wafer holder 28 (not shown in FIG. 1; see FIG. 3). Further, a holder cooling unit 58 for cooling the wafer holder 28 is provided, and the holder cooling unit 58 has a function of adjusting the temperature of a cooling liquid flowing in a liquid circulation path (not shown). The controller 50 stores the temperature of the wafer holder 28 in a steady state detected by the holder temperature detector 56 before the start of exposure in an internal memory (not shown), and is sent from the holder cooling unit 58 after the exposure is started. The temperature of the coolant is controlled within a temperature range determined in accordance with the detection accuracy required of the autofocus unit 40 with reference to the steady state temperature before exposure stored in the memory.

According to the exposure apparatus 10 of the present embodiment described above, the linear motors 20A, 20B, 22A, and 22A are controlled by the controller 50 via the liquid cooling section 54 based on the air conditioning temperature of the stage detected by the temperature sensor 42. The surface temperature of the stators 24a, 24b, 26a, 26b constituting the base 22B is controlled, and the air-conditioning temperature of the stage portion and the stator 24 are controlled.
Temperature control can be performed so that the surface temperatures of the a, 24b, 26a, and 26b are substantially the same. Therefore, even if the wafer stage 18 moves, air fluctuations (temperature fluctuations) hardly occur near the wafer stage 18, so that the occurrence of measurement errors of the laser interferometer due to the air fluctuations can be effectively suppressed. Can be.

Further, the controller 50 controls the amount of temperature rise of the wafer holder 28 via the holder cooling unit 58 within a temperature range determined in accordance with the detection accuracy required of the autofocus unit 40 with respect to the steady state before exposure. Since the control is performed, it is possible to suppress a rise in temperature of the wafer holder 28 from a steady state before exposure to a temperature range that does not affect the detection accuracy required for the autofocus unit 40. Therefore, even if air fluctuation occurs between the wafer W and the projection optical system PL due to the temperature adjustment of the wafer holder 28, the detection accuracy of the autofocus unit 40 hardly decreases.

In the present embodiment, the linear motor 20
A, a stator 24a constituting 20B, 22A, 22B,
Since overcooling and undercooling of the wafers 24b, 26a, 26b and the wafer holder 28 do not occur, efficient temperature adjustment as a whole is possible.

In this case, in the control device 50, the surface temperatures of the stators 24a, 24b, 26a, 26b constituting the linear motors 20A, 20B, 22A, 22B are set so that the air conditioning temperature of the stage portion becomes substantially the same. Although the liquid cooling unit 54 may be controlled, it is not always necessary.
The inventor conducted various experiments using an exposure apparatus equipped with a wafer stage driven by a linear motor having the same configuration as the apparatus of the present embodiment. As a result, the surface temperature of the linear motor was adjusted to within + 1 ° C. of the air conditioning temperature of the stage portion. In this case, it was confirmed that the measurement error due to air fluctuation of the laser interferometer can be suppressed to 3 nm or less. This measurement error is lower than the resolution of the interferometer.

The control device 50 controls the wafer holder 28
The holder cooling unit 58 may be controlled so as to keep the temperature substantially equal to the temperature in a steady state before exposure, but this is not always necessary. The inventor conducted various experiments using a certain stepper. As a result, if the amount of temperature rise of the wafer holder is controlled to be 0.3 ° C. or less from the steady state temperature before exposure, it is caused by air fluctuation of the focus detection system. It was confirmed that the detection error could be suppressed to 30 nm or less. Therefore, the detection accuracy required for the focus detection system is set to the allowable error 30
In the case of about nm (normal accuracy required is not so strict), the above-mentioned steady state temperature before exposure is 0.3
It is sufficient to control the temperature of the wafer holder to less than the temperature.

As is clear from the above description, in the present embodiment, the controller 50 constitutes a temperature adjusting means.

In the above-described embodiment, the case where the present invention is applied to the exposure apparatus that drives the wafer stage 18 by a linear motor has been described. However, the scope of the present invention is not limited to this. Of course, the present invention can be applied to an exposure apparatus using a motor and a feed screw rotated by the motor.

In the above embodiment, the case where the wafer is suction-held on the wafer stage via the wafer holder has been described. However, even in an exposure apparatus which directly holds a substrate such as a wafer on the substrate stage, the present invention is not limited to this. The invention can be suitably applied.

Although not particularly mentioned in the above description, the present invention can be applied to both a stepper and a scanning type exposure apparatus.

[0045]

As described above, according to the first and second aspects of the present invention, it is possible to suppress the decrease in the measurement accuracy of the interferometer due to the temperature adjustment of the motor for driving the stage. Equipment can be provided.

According to the third and fourth aspects of the present invention, it is possible to suppress a decrease in detection accuracy of the focus detection system due to temperature adjustment of the holding member (holder or stage) holding the substrate. An exposure apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a configuration of a main part of an exposure apparatus according to an embodiment.

FIG. 2 is a schematic cross-sectional view taken along line AA of FIG.

FIG. 3 is a block diagram showing components of the apparatus shown in FIG. 1 related to temperature adjustment of components in a chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Exposure apparatus 18 Wafer stage (substrate stage) 20A, 20B X linear motor 22A, 22C Y linear motor 28 Wafer holder (holding member) 32X, 32Y Laser interferometer 40 Autofocus unit (focus detection system) 50 Control device (temperature adjusting means) ) PL Projection optical system W Wafer (substrate to be exposed)

Claims (4)

[Claims] An exposure apparatus comprising: a substrate stage that holds and moves a substrate to be exposed; a motor that drives the substrate stage; and an interferometer that measures a position of the substrate stage. An exposure apparatus provided with a temperature adjusting means for controlling based on an air conditioning temperature of the substrate stage. 2. The exposure apparatus according to claim 1, wherein the temperature adjusting unit controls the surface temperature of the motor within the air conditioning temperature plus one degree. 3. A holding member for holding a substrate to be exposed, a projection optical system for projecting and exposing a mask pattern on the substrate to be exposed, and measuring the position of the substrate to be exposed in the optical axis direction of the projection optical system. An exposure apparatus including a focus detection system that controls a temperature rise amount of the holding member within a temperature range determined according to detection accuracy required for the focus detection system with respect to a steady state before exposure. An exposure apparatus comprising an adjusting unit. 4. An exposure apparatus according to claim 3, wherein said temperature adjusting means controls the amount of temperature rise of said holding member to 0.3 degrees or less from a steady state before exposure.