JPH0480912A - Exposing device - Google Patents

Abstract

PURPOSE:To make it possible to make uniform the temperature of materials used by a method wherein a device, with which the prescribed material among the materials constituting an exposing device in heated or cooled, and another device which measures the temperature of the materials used are provided. CONSTITUTION:A sensor 20 is arranged on the positions A, B, C and D on a stage 3, and a Peltier element 21 is arranged on the positions (a), (b), (c) and (d) on the stage plate 3. A CPU 201 performs the functions of driving of the stage 3, the read-in of temperature from the sensor 20, the heat generation and heat absorption of the Peltier element 21. The Peltier elements 21 at points (a) and (d) generate heat, and the Peltier elements 21 at points (b) and (c) absorb heat. The CPU 201 controls each Peltier element 21 so that the measured value of the sensor 20 at points A, B, C and D is brought to the target temperature. The temperature of each section is measured by the temperature sensor 20, and the temperature of the entire stage plate 3 can be made uniform by controlling the quantity of heat generation and heat absorption of the Peltier element 21.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exposure apparatus for manufacturing semiconductor devices such as ICs and LSIs, and particularly relates to an exposure apparatus for manufacturing semiconductor devices such as ICs and LSIs, and in particular, to a first object surface of a reticle, mask (hereinafter referred to as "reticle"), etc. A pattern such as an electronic circuit formed on the top is directly or through an optical means such as a projection lens,
The present invention relates to an exposure apparatus that can perform positioning, that is, alignment, of a second object and a second object with high precision when performing exposure transfer onto a second object surface such as a surface of a sea urchin.

[Prior Art] An exposure apparatus for manufacturing semiconductor devices such as ICs and LSIs is required to have two basic performances: resolution performance and overlay performance. The former is the ability to form fine patterns on the photoresist surface coated on the semiconductor substrate (hereinafter referred to as "wafer"), and the latter is the ability to form fine patterns on the surface of the urchin in the previous process. In contrast, it is the ability to accurately align and transfer the pattern on the reticle.

Exposure apparatuses are broadly classified into, for example, contact, proximity, mirror 1:1 projection, stepper, and X-ray aligner, depending on their method, and the optimal overlay method for each has been devised and implemented.

In general, exposure apparatuses that have a good balance between resolution performance and overlay performance are preferable for manufacturing semiconductor devices, and for this reason, reduction projection type exposure apparatuses, so-called steppers, are currently often used.

The resolution performance required for these exposure devices is 0.5μ.
Exposure methods that can achieve this performance include, for example, a stepper using an excimer laser as a light source, a proximity type aligner using X-rays as an exposure source, and an exposure method that can achieve this performance.
There is a direct writing method called B. Of these, the former three methods are preferable from the viewpoint of productivity.

[Problem to be solved by the invention] Overlay accuracy is generally determined at a minimum line width of 1/3 to 1 for burn-in.
A value of 15 is required, and achieving this accuracy is generally as difficult or more difficult than achieving resolution performance.

In general, the following points need to be taken into consideration for relative positioning, that is, alignment, between the pattern on the reticle surface and the pattern on the eight surfaces. That is, (1-1) the cross-sectional shape, physical properties, and optical characteristics of the pattern (or mark) on the eight faces of the sea urchin vary widely depending on the type of device and process.

(1-2) In order to ensure alignment with a predetermined accuracy in response to a wide variety of processes, the flyment detection system (
(optical system, signal processing system) must have a degree of freedom.

(1-3) In order to give the alignment optical system a degree of freedom, it is generally advantageous to configure it independently from the projection lens, but as a result, the alignment between the reticle and the wafer becomes indirect. This becomes a systematic error factor.

In general, it is important to minimize these error factors and maintain a good balance.

Here, a specific example will be given and explained.

(2-1) By setting the alignment light to the same wavelength as the exposure wavelength, a TTL ON AXIS alignment system can be constructed. The projection lens has good aberration correction for this wavelength. Therefore, with this method, it is possible to achieve an alignment optical system that can simultaneously observe the projected image of the wafer pattern and the reticle pattern within the same field of view and align both. be able to. This method does not generate systematic errors.

However, this method has process disadvantages such as the alignment wavelength being limited and the signal light from a wafer processed with absorption resist being extremely reduced.

(2-2) On the other hand, in an off-axis type stepper, the wafer alignment optical system can be freely designed without being subject to any restrictions of the projection lens, and this degree of freedom can enhance process adaptability.

However, with this method, it is not possible to observe the reticle and the cross section simultaneously; the reticle is aligned to a predetermined standard using a reticle alignment microscope, and the wafer is aligned using a wafer alignment microscope (hereinafter referred to as a "wafer microscope").
(referred to as ) to perform alignment to the reference within the microscope. For this reason, an error factor exists between the reticle and the square. Moreover, after wafer alignment, a predetermined distance II is set in order to overlap the wafer pattern with the projected image of the reticle.
(Reference length) The wafer must be moved. Therefore, this results in an increase in error factors.

In this way, in an apparatus having an alignment method that includes system errors, these error factors must be kept stable. For example, the reference length, which is the distance between the optical axis of the projection lens and the optical axis of the alignment microscope, is usually several tens of mm. When the structure holding the projection lens and alignment microscope is made of iron-based material, the temperature is 0.1°C.
The reference length changes by about 0.1 μm due to changes in object temperature. Alternatively, when a laser interferometer is used to measure the position of the wafer stage, the measurement is usually performed using a linear mirror reference attached near the end face of the stage, so variations in the distance between the mirror and the wafer will result in alignment errors. Since this distance is also usually several + mm, if the stage substrate is made of an iron-based material, the reference wavelength changes by about 0.1 μm due to a change in object temperature of 0.1° C. That is, it is necessary to suppress temperature fluctuations to within 100% during a series of operations from reference length measurement to alignment measurement and exposure. In terms of temperature control, it is relatively easy to keep things stable in steady state. However, as in the above system, since the exposure position and alignment position are far apart, for example,
In order to align and expose a 6-inch wafer over its entire surface, the wafer stage must move 200 to 300 mm. The temperature must always be stabilized at 0.1°C or less over the entire range.

Generally, this type of equipment is attached with an air conditioner for temperature control, and a system is installed to stabilize the temperature of the entire equipment. For example, in the case of a system in which a room is set up that encloses the entire device, temperature-controlled air is flowed from the ceiling, and the return is taken from a place close to the floor, problems may occur if there is no heat source inside the device. However, since an exposure apparatus has many drive actuators, their drivers, etc., a considerable amount of heat is generated. In that case, the area facing downwind will be affected by the heat and the temperature will gradually rise.

Furthermore, if there are structures that obstruct the flow of wind due to mechanical or structural issues, the areas shaded by these structures become stagnation points for the flow of wind, so there is a heat source there. In some cases, the temperature may become high in some parts.

Therefore, a method often used is to flow air for temperature control through a separate system into areas where temperature stabilization is particularly required (for example, near the wafer stage or near the projection lens).

However, even in that case, the projection lens, focus detection system, wafer microscope, etc., become obstacles to the wind flow, especially in the vicinity of the wafer stage, and the wafer stage is used for wafer exposure and detection of wafer alignment marks. Because the stage structure sometimes moves from 100 mm to several hundred mm, the wind flow changes significantly. Furthermore, there are several actuators in the stage for moving the wafer in XY, θZ, etc., which has the disadvantage of becoming a heat source and causing instability in the surrounding environment.

Furthermore, in Japanese Patent Application No. 1-266184, an exposure device is equipped with a louver consisting of a plurality of individually adjustable angle fins at the temperature control medium outlet and a fan whose air direction and volume can be adjusted on the flow path of the temperature control medium. is proposed.

However, even with this method, there is a phenomenon that the temperature is low near the wind outlet and high near the exhaust. Another drawback was that it was difficult to adjust the fins to make the temperature uniform.

In view of the above-mentioned problems in the conventional example, the present invention makes the temperature of each material constituting an exposure device uniform, and when superimposing a reticle as a first object and a square as a second object, various types of To provide an exposure apparatus that can always perform highly accurate overlay by reducing system errors such as overlay error factors, such as changes over time in a reference length and over time changes in arrangement coordinates of a wafer stage. With the goal.

[tI! Means and operation for solving Pi] In order to achieve the above object, the present invention provides a method for transferring a pattern drawn on an original such as a reticle or mask onto a substrate such as a wafer placed on a substrate mounting stage. The exposure apparatus for projection transfer is characterized in that a predetermined ring material among the constituent materials constituting the exposure apparatus is equipped with means for heating or cooling the ring material and means for measuring the temperature of the ring material. do.

It is desirable that the heating/cooling means and the temperature measuring means be provided in a ring near the wafer mounting stage that is movable with respect to the exposure light source and in a ring near the projection lens to the alignment microscope.

Further, it is preferable that the heating and cooling means is used to control the temperature of the winter clothing based on the temperature measurement results of each part measured by the temperature measuring means.

Furthermore, the temperature of the winter material may be controlled using a heating and cooling means based on the position of the wafer mounting stage.

The apparatus may further include means for partially air-conditioning the ring near the wafer mounting stage and the ring near the projection lens to the alignment microscope.

[Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a schematic diagram of an exposure apparatus according to a first embodiment of the present invention.

In this embodiment, a so-called off-axis alignment type exposure apparatus is taken as an example.

In FIG. 1, the main body of the exposure apparatus is entirely surrounded by an apparatus air conditioner 100, and the temperature is stabilized with temperature-controlled air. The lens barrel surface plate 108 holds the projection lens 105, the wafer microscope 106, etc., and ensures their positional relationship.

Illumination light from the illumination system 101 illuminates a reticle 103 as a first object held by a platen (not shown). Then, a pattern such as an electronic circuit formed on the surface of the reticle 103 is projected and transferred onto the surface of the wafer 1 as a second object by a projection lens 105 surrounded by an outer tube 109.

The reticle 103 can be converted by a transport means (not shown). Around the bottom of the reticle 103, the reticle 1
A reticle reference mark 104 for correctly locating the reticle 03 with respect to the coordinate system of the apparatus is arranged with a slight gap from the reticle 103. The reticle 103 is placed at a position opposite to the reticle reference mark 10 with the reticle 103 in between.
A reticle microscope 102 is provided for alignment with respect to 4. Note that the objective lens of the reticle microscope [102 and the reticle reference mark 104 are provided, for example, at two locations symmetrically about the center of the reticle.

To align the reticle, a reticle microscope 102 reads the relative positional error between the set mark provided on the surface of the reticle 103 and the reticle reference mark 104, and a reticle stage (not shown) movable in the XYθ directions moves the reticle 103 to the set mark. This is performed by driving in a direction in which the relative positional error between the reference mark 104 and the reference mark 104 approaches zero, and ends when the relative positional error becomes less than a predetermined tolerance range.

On the other hand, the temperature of the space partitioned by the lens barrel surface plate 10B is controlled by a partial air conditioner 107 in a separate system from the air conditioning of the entire apparatus.

A wafer alignment microscope 1 is installed near the projection lens 105.
06 is placed. The wafer 1 is vacuum-adsorbed and held by a wafer chuck 8 that is movable in the rotational direction and vertical direction, and the wafer chuck 8 is held by a stage plate 3, which moves on a stage substrate 7 in the X and Y directions. It is configured so that it is possible.

A pattern made up of a plurality of shots up to the previous process is formed on the wafer 1, and a photosensitive agent is applied thereto. Each shot is provided with, for example, 2111 wafer alignment marks (hereinafter referred to as FAA marks) symmetrically about the shot center. After the wafer 1 is aligned in the XY direction and rotational direction based on the external shape by a pre-alignment mechanism (not shown), it is carried onto the wafer chuck 8 by a transport means (not shown). Stage board 3 XY
, and send each AA mark of the pre-selected shot into the detection area of the wafer microscope 106 in order, and at the same time move the wafer chuck 8 vertically to bring the pattern surface to the focal position of the wafer microscope 106. Then, the position of each shot on the wafer with respect to the microscope optical axis is calculated and aligned based on the amount of deviation of the mark from the microscope optical axis and the coordinates of the XY stage at that time. Then, by accurately moving the XY stage by a pre-measured reference length (that is, the distance m between the optical axis of the projection lens and the optical axis of the wafer microscope) and performing exposure, the pattern formed up to the previous process is The aligned reticle projection image is transferred.

FIG. 2 is a plan view of the area around the wafer stage of the exposure apparatus shown in FIG. In FIG. 2, at the end of the stage plate 3 on which the wafer 1 is mounted, there is an optical mirror 2 for detecting position coordinates in each of the X and Y directions, and a laser interference length measuring device for making a light beam incident on the optical mirror 2. (hereinafter referred to as "interferometer")5
is located. Then, based on the outputs of the two interferometers 5, the position detection processing unit 6 calculates the position of the wafer stage and the XY position coordinates of the wafer 1. Positioning of the wafer 1 is performed by controlling the drive of the motor 4 so that the coordinates of the wafer 1 calculated by the position detection processing section 6 match predetermined position coordinates.

Conditioned air is supplied through a blowout duct 10 and a flow control valve 15,
It passes through the filter 11 and reaches the blowout side looper 12. The direction of the conditioned air is changed depending on the angle of the plurality of fins 50 of the blow-off side looper 12, and the air flows as shown by the air flow direction arrow 30 in the figure. Conditioned air that has flowed through the wafer 1, optical mirror 2, stage plate 3, etc. passes through the exhaust side louver 13 and is exhausted from the exhaust duct 14.

Here, if the stage plate 3 moves, the transmission of heat from a heat generation source, such as the motor 4, to the stage plate 3 etc. changes, and the distance, reference length, etc. between the wafer 1 and the optical mirror 2 change. Also, depending on the location of the conditioned air itself, there will be areas where the temperature is high and areas where the temperature is low.

It is difficult to control the temperature of the ring by changing the direction, temperature, and flow rate of the conditioned air, and especially when there are obstacles, detailed control is not possible.

FIG. 3 is a simplified diagram of FIG. 2 to explain how temperature control is performed, and is a schematic diagram showing the basic configuration for temperature control.

The sensors 20 are installed at positions A, B, C, and D on the stage plate 3, and the Bertier elements 21 are installed at positions a, b on the stage plate 3.
, c, and d.

The CPU 201 drives the stage 3, reads the temperature from the sensor 20, and causes the Vertier element 21 to generate and absorb heat.

'$4 Figure is a graph showing an example of the temperature distribution on the stage plate 3. A, B, C, D, a, bc, and d correspond to each position in FIG. The graph in FIG. 4 shows that the temperature at the lower left of the stage plate 3 in FIG. 3 is low and the temperature at the upper right is high.

A specific method of temperature control will be explained based on the embodiments shown in FIGS. 1 to 4 above.

First, the CPU 201 learns the temperature at each point from the sensors 20 at each point A, B, C, and D. Here, from the graph of FIG. 4, the temperature at point A is lower than the target temperature, the temperatures at points B and D are the same as the target temperature, and the temperature at point 0 is higher than the target temperature. Based on this information, the CPU 201 adjusts the positions a and b in order to bring the temperature of the entire stage plate 3 to the target temperature.
.

The Vertier elements 21 at each point c and d are controlled.

That is, let the Bertier elements 21 at points a and d generate heat, and b
, the Bertier element 21 at point c is endothermic. in this way,
The CPU 201 controls each Vertier element 21 so that the measured value of the sensor 20 at each point A, B, C, and D becomes the target temperature. By measuring the temperature of each part with the temperature sensor 20 and controlling the amount of heat generation and heat absorption of the Bertier element 21,
The temperature of the entire stage plate 3 can be made uniform.

Note that the sensor 20 and the Vertier element 21 can be scattered at various locations, and the temperature of each can be controlled individually, so that the temperature of the object can be easily kept constant. In addition, since it is in direct contact with the object, it can quickly respond to temperature changes in the ring material.

Further, the control method is not limited to measuring the temperature with the temperature sensor 20 and controlling the Vertier element 21 as in the above embodiment. For example, in response to a temperature change that is known in advance depending on the position of the stage, the Vertier element 21 may be controlled according to the position of the stage.

Temperature control using the Bertier element 21X alone may be considered, but it is desirable to use it in combination with partial air conditioning in order to prevent the air inside the device from rising due to heat sources such as the motor and driver within the device.

In addition, if it is difficult to maintain the temperature at the target temperature, try to keep the temperature uniform, and if the reference length changes due to temperature deviation, remeasure the reference length or correct the reference length using software. It's okay.

Further, in the above embodiment, the temperature was controlled using the Bertier element 21, but the temperature may be controlled using cold water, hot water, cold air, hot air, a heater, or the like.

[Effects of the Invention] As explained above, according to the present invention, for example, a means for measuring the temperature of a ring near the stage and a ring near the projection lens to the alignment microscope and a means for changing the temperature up or down are provided. Since the temperature of the rings is made uniform, various error factors in overlaying, such as the reference length, can be avoided when overlapping the reticle as the first object and the square as the second ring material. This has the effect of reducing system errors such as changes over time and changes in the arrangement coordinates of the wafer stage over time, and allows highly accurate overlaying at all times.

[Brief explanation of the drawing]

Figure 's1 is a schematic diagram of an exposure apparatus according to an embodiment of the present invention, Figure 2 is a plan view of the area around the Quartz stage, and Figure 3 is a schematic diagram showing the basic configuration for temperature control. ip, Figure 4 is a graph showing an example of temperature distribution on the stage plate. : Wafer, : Optical mirror: Stage plate, Stage motor, : Interferometer, : Laser interferometer position detection processing unit, 2: Blowout side louver 3: Exhaust side louver 5: Flow rate control valve, 0: Temperature sensor, 1: Beltier element, 01: CPU.

Claims (5)

[Claims] (1) In an exposure device that projects and transfers a pattern drawn on an original onto a substrate placed on a substrate mounting stage, a predetermined material among the constituent materials constituting the exposure device,
An exposure apparatus characterized by comprising means for heating or cooling the material and means for measuring the temperature of the material. (2) Claim 1, wherein the heating/cooling means and the temperature measuring means are provided on an object near a wafer mounting stage movable with respect to an exposure light source and an object near a projection lens to an alignment microscope. The exposure apparatus described in . (3) The exposure apparatus according to claim 1 or 2, further comprising means for controlling the temperature of each material using the heating and cooling means based on the temperature measurement results of each part measured by the temperature measuring means. (4) The exposure apparatus according to claim 1 or 2, further comprising means for controlling the temperature of each material using the heating and cooling means based on the position of the wafer mounting stage. (5) The exposure apparatus according to claim 1, further comprising means for partially air-conditioning objects near the wafer mounting stage and objects near the projection lens to the alignment microscope.