JPH02199814A - Projection aligner - Google Patents

Abstract

PURPOSE:To eliminate a fluctuation of an image by a method wherein a space including an optical path of an exposure beam between a first object on which a pattern to be projected onto an object to be exposed has been formed and a second object as an object to be exposed is surrounded locally and its temperature is controlled separately from a chamber surrounding a whole aligner. CONSTITUTION:A whole aligner is mounted on a surface plate 8 which has been made vibrationproof by a vibrationproof base 9; it is installed inside a chamber 20. The air whose temperature has been adjusted by using a heat exchanger 21 is blown into the chamber 20 from a blowoff duct 23, and is evacuated from a return duct 23. Then, a chamber 33 which surrounds a space as an optical path, of an exposure beam between a projection lens 3 and a wafer 4 is installed; it surrounds also a space around a wafer stage including an optical path of an interferometer length-measuring instrument 10. Also a space including the optical path of the exposure beam between a reticle 2 and the projection lens 3 is surrounded by a chamber 34. The air, whose temperature has been adjusted, from a heat-exchange blower 30 is sent to the chambers 33, 34 by means of blast pipes 31, 32. Thereby, a fluctuation in a refractive index of the air in the space as the optical path of the exposure beam can be reduced to a minimum and a good alignment accuracy can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection exposure apparatus used for forming extremely fine patterns, such as in semiconductor integrated circuits.

[Prior Art] In recent years, as the degree of integration of semiconductor integrated circuits has increased, projection exposure equipment that projects and transfers the pattern on the reticle onto the wafer is also equipped with a high-resolution reduction projection lens, and the wafer can be moved step-and-repeat. The mainstream is a so-called stepper that sequentially projects and transfers a pattern onto a plurality of exposure areas on a square by moving the pattern in a sequential manner.

The stepper is required to have an overlay (alignment of the pattern formed in the previous process on the wafer and the projected image of the reticle) accuracy commensurate with the resolving power of the projection lens. Generally, an overlay accuracy of 175 to 1/1O of the minimum resolution line width of the projection lens is required. Therefore, for example, a lens that resolves a 0.8 μm wide pattern for VLSI manufacturing requires an overlay accuracy of 0.08 to 0.16 μm.

In order to realize such highly accurate overlaying, temperature control of each part of the device is important. Conventionally, the entire device was installed in a temperature control chamber 120 as shown in FIG. 4, and the air inside the chamber 120 was controlled the temperature. In FIG. 4, a reticle 102 is illuminated by an illumination optical system 101, and an image of a pattern formed on the reticle 102 is projected onto a projection lens 103.
The image is projected and transferred onto the exposure area of the wafer 104 located directly below the projection lens 103.

The wafer 104 can be moved in the vertical direction (in the direction of the optical axis of the projection lens) by a Z stage 105, and can be moved in the X and Y directions (in the direction of the optical axis of the projection lens) by an
It is possible to move in a direction perpendicular to the optical axis of the projection lens. The position of the wafer 104 in the X and Y directions is monitored by a laser interferometer 110, and is positioned at a predetermined position by the X and Y stages 106 and 107. Further, the surface height of the wafer 104 is detected by a height sensor (not shown), and the height is adjusted by a Z stage.

The entire apparatus is mounted on a surface plate 108 that is vibration-isolated by a vibration-isolating table 109 and installed in a temperature-controlled chamber 120 . Inside this temperature control chamber 120, air whose temperature has been adjusted to a set temperature by a heat exchanger 121 is blown from a blow-off duct 122, and the blown air is exhausted from a return duct 123.Although not clearly shown in Fig. 6, The air sent out from the blow-off duct 122 also flows around the reticle 102, the projection lens 103, and the wafer stage (105, 106, 107).

[Problem to be solved by the invention] However, in the conventional technology as described above, the entire device is surrounded by one chamber and air-conditioned at once, so various electronic parts, motors, lasers, etc. Due to the large influence of heat generated from the heat source, it has been difficult to maintain temporal and spatial uniformity in the refractive index of the air in the space between the reticle and the projection optical system, including the projection optical system. That is, since the refractive index of air changes depending on the temperature, the image formation position may be scattered or the image may be distorted, which is one of the major causes of deteriorating the overlay accuracy.

The present invention has been made in view of these conventional problems, and provides a projection exposure apparatus that can minimize the refractive index fluctuation of the air in the space that serves as the optical path of the exposure light and obtain good overlay accuracy. The purpose is to provide the following.

[Means for Solving the Problems] In the present invention, in addition to the first chamber surrounding the entire projection exposure apparatus, a projection optical system and a second object to be exposed (
a second space surrounding the space containing the optical path of the exposure light between the wafers);
The above object is achieved by providing a chamber and controlling the temperature of the air in the first chamber and the second chamber separately.

Further, a third chamber is provided which surrounds a space including an optical path of exposure light between the first object (reticle) on which a predetermined pattern is formed to be projected onto the second object (reticle) and the projection optical system. It is more desirable to control the temperature of the air in the first chamber and the air in the second and third chambers separately in order to suppress image fluctuation and distortion.

[Function] A major cause of distortion and fluctuation of the projected image is the fluctuation in the refractive index of the air in the space that serves as the optical path of the exposure light. In addition, second and third chambers are provided which locally surround a space including the optical path of exposure light between the reticle and the square;
Temperature control is performed separately from the chamber. That is, since the second and third chambers do not include a heat source and have a small capacity, the heat load within the chambers is small, and therefore it is possible to control the temperature of the air with high precision.

It is preferable that the second and third chambers are provided so that the capacity is as small as possible, but as long as the capacity of the second chamber does not become too large, the area around the stage including the optical path of the interferometric length instrument that detects the position of the wafer stage. If the space is surrounded by the second chamber, the error in detecting the position of the wafer will be reduced, which is advantageous in improving the overlay accuracy.

It should be noted that the third chamber described above does not necessarily need to be provided when reduction projection is performed by the projection optical system, because if the reduction ratio of the reduction projection optical system is m times, the distance between the reticle and the projection optical system is This is because the influence of the refractive index fluctuation of the air between the reticle and the projection optical system is smaller than the space between the projection optical system and the space, since the influence of the refractive index fluctuation of the air between the reticle and the projection optical system is also multiplied by m.

[Embodiment] FIG. 1 is a block diagram of a projection exposure apparatus according to an embodiment of the present invention. In FIG. 1, a reticle 2 is illuminated by an illumination optical system 1, and a pattern formed on the reticle 2 is projected onto a wafer by a projection lens 3. The image is projected and transferred to the exposure area located directly under the projection lens 3 of No. 4.

The wafer 4 can be moved vertically (in the direction of the optical axis of the projection lens) by a Z stage 5, and can also be moved by an X stage 6.
, Y stage 7 allows movement in the X and Y directions (directions perpendicular to the optical axis of the projection lens). and,
The position of the wafer 4 in the X and Y directions is determined by the laser interferometer 1.
0 and the wafer 4 is positioned in position by the X and Y stage 106107.

Further, the surface height of the wafer 104 is detected by a height sensor (not shown), and the height is adjusted by a Z stage.

The entire device consists of a surface plate 8 which is vibration-isolated by a vibration-isolating table 9.
a first chamber 2 placed above and surrounding the entire device;
It is set within 0. The first chamber 20 itself has a configuration similar to that provided in a conventional exposure apparatus, and air, which has been adjusted to a predetermined temperature by a heat exchanger 21, is blown into the first chamber 20 from a blowout duct 23. The blown air is exhausted from a return duct 23. Note that a light source (such as a lamp) that supplies illumination light to the illumination optical system 1 is arranged outside the partition wall of the first chamber 20.

In the present invention, in addition to the first chamber 20, a second chamber 33 is provided which surrounds a space that becomes the optical path of the exposure light between the projection lens 3 and the wafer 4 to be exposed. Interferometer 10 with two chambers 33
It also surrounds the space around the wafer stage (2 stages 5, X stage 6, Y stage 7) including the optical path.

Here, the laser light source 11 of the length measuring device 10 serving as a heat source is
It is installed outside the chamber 33, and the laser beam is introduced into the second chamber 33 by an introduction optical system covered with the vibrator 12.

Furthermore, in this embodiment, the space between the reticle 2 and the projection lens 3 that includes the optical path of the exposure light is also surrounded by the third chamber 34 .

Then, air sent out from the heat exchanger/blower 30 and adjusted to a predetermined temperature is sent into the second and third chambers 33 and 34 by blower vibrators 31 and 32, respectively. Note that the second and third chambers 33.3
A gap is provided between the partition wall 4 and the projection lens 3 to prevent vibrations caused by air from being transmitted to the projection lens 3.
It is desirable that the material be made of a material that can absorb zero vibrations.

The air blown into the second and third temperature control chambers 33.34 flows out through holes (not shown) made in the chamber partition walls, so that the pressure inside the chambers 33.34 increases from the outside. By adjusting the air flow rate so that the air flow is slightly higher, air will not flow backwards. Of course, a return duct may be provided to return air to the heat exchanger/blower 30. Although not shown, the chamber 33 is provided with a screen for loading and unloading the wafer 4. It has a structure that opens and closes only at certain times.

In the embodiment described above, the temperature control chamber 34 is provided between the reticle 2 and the projection lens 3, but as described above, when the projection lens 3 is a reduction projection lens, the reticle 2 and the projection It is not necessarily necessary to provide the lens 3 because the adverse effect of the refractive index fluctuation of the air between the lenses 3 is reduced.

Next, FIG. 2 is a sectional view showing an example of the partition wall of the chamber according to the present invention, and the partition wall of the chamber 33 is formed by the inner metal plate 4.
It has a structure in which a heat insulating material 42 is filled between 1 and an outer plate member 43. In this way, the influence of heat generated outside the chamber is reduced, and if a material with high thermal conductivity is selected for the metal plate 41, the temperature of the entire inner surface of the chamber quickly becomes almost equal to the temperature of the air blown from the vibrator 32. , the temperature of the air inside the chamber can be precisely controlled.

FIG. 3 is a cross-sectional view showing an example of the chamber barrier.

The inside of the partition wall of the chamber 33 is made up of a metal plate 41 and the outside is made up of a plate member 43, which is the same as in FIG.
In the example shown in the figure, the inside of the partition wall has a two-layer structure. In the example shown in FIG. It has a structure in which it enters and exits from an outlet 46. Further, a heat insulating material 42 is filled between the outer side of the fluid conduit 44 and the plate member 43.

By using a chamber with such a partition wall structure and controlling the temperature so that the temperature of the fluid matches the temperature of the air blown from the pipe 32, the temperature inside the chamber can be more uniformly and precisely maintained at a predetermined temperature. The variation in the refractive index distribution of the air inside the chamber can be kept very small.

[Effects of the Invention] As described above, the present invention locally surrounds a space including an optical path of exposure light between a first object on which a pattern to be projected onto an exposure object is formed and a second object that is an exposure object. By controlling the temperature separately from the chamber that surrounds the entire exposure device, fluctuations in the refractive index of the air in the space that forms the optical path of the exposure light can be minimized, and fluctuations and distortions in the projected image can be virtually eliminated. It has the effect of being able to.

That is, if such a projection exposure apparatus is used in the manufacture of integrated circuits, the overlay accuracy of patterns formed on the squares can be improved, and integrated circuits with a higher degree of integration can be manufactured with high yield, which is extremely beneficial. .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a projection exposure apparatus according to an embodiment of the present invention;
FIGS. 2 and 3 are sectional views showing the structure of a partition wall of a chamber according to the present invention, and FIG. 4 is a configuration diagram of a conventional device. [Description of symbols of main parts] 1... Irradiation optical system 2... Reticle (first object) 3... Projection lens 4... Wafer (second object) 20... First chamber 30. ...Heat exchange/blower (temperature control means) 33...
Second chamber 34...Third chamber agent Patent attorney Masaru Sato Figure 2 Figure 3

Claims (2)

[Claims] (1) By irradiating a first object with light emitted from a light source, an image of the pattern formed on the first object is projected onto a predetermined exposure area of a photosensitive second object via a projection optical system. In a projection exposure apparatus for transferring, a first chamber surrounds the entire projection exposure apparatus; a second chamber surrounds a space including an optical path of exposure light between the projection optical system and the second object; 1. A projection exposure apparatus comprising a temperature adjusting means for separately adjusting the temperature of the air in the second chamber and the air in the second chamber. (2) By irradiating the first object with light emitted from a light source, the image of the pattern formed on the first object is projected onto a predetermined exposure area of the photosensitive second object via the projection optical system. In a projection exposure apparatus for transferring, a first chamber surrounding the entire projection exposure apparatus, a second chamber surrounding a space including an optical path of exposure light between the projection optical system and the second object, and the first object. and a third chamber surrounding a space including an optical path of exposure light between the projection optical system and the projection optical system; and temperature adjustment means for separately adjusting the temperature of the air in the first chamber and the air in the second and third chambers. A projection exposure apparatus comprising: