JPH0845827A - Projection exposure device and manufacture of semiconductor device using it - Google Patents

Abstract

PURPOSE:To efficiently correct nonuniformity of the distribution of a refractive index by heating the peripheral part of a lens in a ring-like form and supplying and exhausting a gas in a plurality of spaces between lenses to linkingly operate temperature control so that the temperature becomes a predetermined temperature which is set in advance. CONSTITUTION:A lens space is set as lens spaces 35, 36, 38, 39 and a gas is made to flow into there. A heating means for warming the peripheral part of the lenses is provided in lens frames 4, 7. A gas temperature control means 21 controls a heat exchange means 19 so that the gas has a predetermined temperature on the basis of the measured results by a thermometer. A gas exhausting means 22 collects the gas by an exhaust piping 16 to exhaust a fixed quantity of gas per unit time. The temperature control by the heating means for warming the peripheral part of the lenses and the gas temperature control means 21 is linkingly operated so that the temperature becomes a predetermined temperature which is set in advance. Thereby, the temperature distribution inside the lenses is always kept flat, thereby being able to suppress the change of the magnifying power of a projection lens and the change of distortion.

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 and a method of manufacturing a semiconductor device using the same, and particularly to IC, L
When an electronic circuit pattern on a reticle surface is projected onto a wafer surface by a projection optical system (projection lens) when manufacturing a semiconductor device such as SI, the lens forming the projection optical system uses exposure light (exposure light energy). The temperature distribution inside the lens is effectively prevented by absorbing the temperature fluctuations in the lens and changing the optical characteristics, so that a highly accurate projected pattern image can be obtained. is there.

[0002]

2. Description of the Related Art Conventionally, a step-and-repeat type reduction type projection exposure apparatus (stepper) using a projection optical system has been widely used for forming an electronic circuit pattern of a semiconductor element such as an IC or an LSI.

In recent years, as the degree of integration of semiconductor integrated circuits has improved, further improvement in resolution, overlay accuracy and throughput has been demanded. One of the factors that affect the resolution is the curvature of field of the projection lens. Further, one factor that influences the overlay accuracy is the imaging magnification and distortion of the projection lens. Normally, the projection lens is assembled while being adjusted with high accuracy at the time of assembly, so that the optical aberrations thereof are about the designed values. However, during actual operation of the device, each lens that constitutes the projection optical system absorbs part of the energy of the exposure light (g-line, i-line, KrF excimer laser, etc.), which causes a temperature distribution inside the lens. come.

As a result, a refractive index distribution is generated inside the lens, and the surface shape of the lens is changed. It has been pointed out for some time that the optical characteristics (field curvature, imaging magnification, distortion) of the projection lens change due to both causes. Although glass materials having a high transmittance for each exposure light have been developed, recently, the number of lenses in the projection lens increases and the NA of the projection lens increases, so that the lens aperture tends to increase. For this reason,
This phenomenon is of further concern. Further, recent LSIs have a complicated structure, and a process with a large step tends to be frequently used, and it is important to secure a predetermined depth of focus within the angle of view of the projection lens.

Further, in the mass production line of each LSI, in order to improve the throughput, a high resolution stepper is used for the critical layer, and a high throughput stepper having a low resolution but a wide angle of view is used for the non-critical layer. Is coming. In general, it is necessary to suppress fluctuations in the projection lens magnification, distortion, etc. as much as possible in order to support the Mix & Match process in different models. As described above, the optical performance is one of the foundations of the device performance of the stepper, and it is important to suppress these performance changes as much as possible or to provide some kind of correction means even if a change occurs.

Conventionally, as means for correcting the change in the optical characteristics, Japanese Patent Laid-Open Nos. 60-79357 and 60-
Japanese Laid-Open Patent Publication No. 79358 proposes a method of flowing a gas whose temperature and pressure are controlled to predetermined values in a chamber of a projection lens. Further, Japanese Patent Laid-Open No. 5-347239 proposes a method of heating the peripheral portion of one or more lenses of the projection lens to make the temperature distribution inside the lens as uniform as possible.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In Japanese Patent Laid-Open No. 357 and Japanese Patent Laid-Open No. 60-79358, air is made to flow through one or more lens spaces of a projection lens at a predetermined temperature. However, in our simulation, it was difficult to suppress the aberration change to a predetermined value even if the temperature of the center of the lens having the highest temperature was lowered by 20 to 30%. Although the optical performance of the projection lens can be maintained at a predetermined value by uniformly lowering the temperature inside the lens to the temperature of the air, its implementation is quite difficult. Even if the temperature inside the lens can be uniformly lowered to the temperature of the air,
This is very difficult to implement because it requires a large amount of equipment, such as using a liquid as a refrigerant.

Further, in recent years, a gas molecule in the atmosphere of a clean room undergoes a photochemical reaction with exposure light, and as a result, a substance such as ammonium sulfate is produced and adheres to the lens surface of the illumination optical system to reduce the image plane illuminance. The problem has been pointed out. In the above conventional example, the projection lens is the object to be air-cooled even though the HEPA filter is used. Therefore, the lens space is constantly supplied with air from the air supply source, and the lens is exposed to air. as a result,
The above substance may adhere to the lens surface of the projection lens and the optical characteristics of the lens may change. In that case, lens cleaning may be performed, but it is generally not easy, and there arises a problem that very large-scale disassembly, assembly, readjustment and the like are required.

In JP-A-5-347239, when the exposure is performed, the temperature distribution of each lens of the projection lens is high in the vicinity of the optical axis and low in the peripheral portion, paying attention to the phenomenon that the peripheral portion of the lens is forcibly added. It is heated to make the temperature distribution uniform.

However, in this projection exposure apparatus, a phenomenon in which heat is trapped inside the projection lens can be considered. Therefore, this heat must be dissipated by some means, but the above-mentioned conventional example does not sufficiently disclose it.

According to the present invention, the lens constituting the projection optical system absorbs the exposure light and the temperature distribution of the lens becomes non-uniform,
A projection exposure apparatus and a projection exposure apparatus capable of effectively correcting a change in lens shape and a non-uniform internal refractive index distribution, maintaining good optical characteristics, and obtaining a projection pattern image with high resolution are used. An object is to provide a method for manufacturing a semiconductor device.

[0012]

Means for Solving the Problems (1-1) A projection exposure apparatus according to the present invention is a projection exposure apparatus that projects and exposes a pattern on a first object plane onto a second object plane by a projection optical system. Heating means for heating at least one lens peripheral portion constituting the system in a ring shape,
Lens temperature control means for controlling the peripheral portion of the lens to a predetermined temperature, gas supply / exhaust means for supplying and exhausting gas to and from a plurality of lens spaces sandwiched by lenses forming the projection optical system, and the gas Is provided with a gas temperature control means for controlling the temperature to be a predetermined temperature, and the lens temperature control means and the temperature control by the gas temperature control means are interlocked so as to be a predetermined temperature. I am trying.

In particular, the gas supply / exhaust means connects a gas supply means for supplying gas into the lens space and a gas exhaust means for exhausting gas by a duct, and the gas is exhausted in a closed system through the lens space. Circulating, the gas supply and exhaust means has a laminar flow means for making the flow of gas laminar in the supply port for supplying gas into the lens space and the exhaust port for exhausting gas, And the gas is air,
It is characterized by being N ₂ and CO ₂ .

(1-2) In the method of manufacturing a semiconductor device according to the present invention, after the pattern on the reticle surface is projected and exposed on the wafer surface by the projection optical system, the wafer is subjected to a developing process to manufacture a semiconductor element. At this time, at least one lens peripheral part constituting the projection optical system is heated in a ring shape by a heating means, and at this time, the lens temperature control means controls the lens peripheral part to reach a predetermined temperature. When the gas is supplied and exhausted by the gas supply / exhaust means to the plurality of lens spaces sandwiched by the lenses forming the system, and the temperature of the lens is controlled by the gas temperature control means so that the gas becomes a predetermined temperature, It is characterized in that a step of operating the temperature control by the control means and the gas temperature control means in conjunction with each other so as to reach a predetermined temperature set in advance is utilized.

In particular, the gas supply / exhaust means connects a gas supply means for supplying gas into the lens space and a gas exhaust means for exhausting gas by a duct, and the gas is exhausted in a closed system through the lens space. Circulating, the gas supply and exhaust means has a laminar flow means for making the flow of gas laminar in the supply port for supplying gas into the lens space and the exhaust port for exhausting gas, And the gas is air,
It is characterized by being N ₂ and CO ₂ .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of a projection exposure apparatus of the present invention, and FIGS. 2 and 3 are explanatory views of a part of FIG.
In the figure, 51 is a reticle, on the surface of which an electronic circuit pattern is formed. A reticle stage 51a holds the reticle 51 by suction. Reference numeral 50 denotes an illumination system, which is, for example, an excimer laser as a light source means,
Alternatively, it has an ultra-high pressure mercury lamp, a masking device, etc., and illuminates the electronic circuit pattern on the surface of the reticle 51 with exposure light with a uniform illuminance distribution.

PL is a projection optical system (projection lens),
The electronic circuit pattern on the surface of the reticle 51 illuminated by the exposure light from the illumination system 50 is given a predetermined magnification (for example, 1/5 or 1 /).
In 10), it is projected on the surface of the wafer 27. The surface of the wafer 27 is coated with a photosensitive material such as a resist. Two
A wafer chuck 8 sucks and holds the wafer 27. 29 is a wafer stage, and the wafer 27 is XY
Z direction, θ, and tilt drive are possible.

Reference numeral 2 is a projection lens barrel, 9 to 14 are respective lenses constituting the projection lens PL, and 3 to 8 are lenses 9 to 1.
4 is a lens frame that stores and holds 4. 35 to 40 are lens spaces formed by the respective lenses. In this embodiment, the temperature distribution and the shape deformation due to the energy absorption of the exposure light of each lens at the time of exposure are calculated in advance, and the lens that particularly contributes to the field curvature variation, magnification variation, and distortion variation of the projection lens PL is obtained. .

In this embodiment, the lenses 10 and 1 are used for convenience.
3 is set. Therefore, in this embodiment, the lens spaces into which the gas is introduced are lens spaces 35, 36, 38 and 39. The heating means for warming the lens peripheral portion is provided in the lens frames 4 and 7. 18 is a gas supply means,
Gas (air, N, etc.) in the lens spaces 35, 36, 38, 39
₂ and CO ₂ ) are flowed in, and at this time, it is adjusted in advance so that a constant flow rate of gas flows into each lens space per unit time. 19 is a heat exchange means for adjusting the gas sent from the gas supply means 18 to a predetermined temperature. 20 is a HEPA filter (High Efficiency Par
It is a ticulate air filter) and removes the gas dust sent from the heat exchange means 19.

A thermometer 17 measures the temperature of the gas passing through the HEPA filter 20. Reference numeral 21 denotes gas temperature control means (temperature control means A), which is a thermometer 1
The heat exchange means 19 is controlled so that the gas reaches a predetermined temperature based on the measurement result of 7. The accuracy of gas temperature control is ± 3/100 ° C., for example. Reference numeral 15 is a supply pipe, which sends the temperature-controlled gas into the lens space. Reference numeral 16 denotes an exhaust pipe, which is a lens space 35, 36, 3
The gas that has passed through 8, 39 and has cooled the lenses 10, 13 is collected. Reference numeral 22 denotes a gas exhaust means, which collects the gas through the exhaust pipe 16 so that a constant amount of gas is exhausted per unit time. The gas supply means 18 and the gas exhaust means 22 form one element of the gas supply / exhaust means. Reference numeral 1 denotes a circulation pipe (duct), which sends the gas recovered by the gas exhausting means 22 to the gas supplying means 18 again.

In this embodiment, the circulation pipe 1 allows the gas to circulate through the lens spaces 35, 36, 38 and 39 in a system which is always closed, whereby the projection optical system PL.
The substance that causes the decrease in transmittance is prevented from adhering to the lens surface. Reference numeral 23 is a current supply means as one element of the heating means, and supplies current to the heaters of the lens frames 4 and 7 in order to flatten the temperature distribution inside the lenses 10 and 13.

Reference numeral 24 is a lens temperature control means (temperature control means B) which controls the current supply means 23 so that the temperature becomes a predetermined temperature based on the measurement result of a thermometer (not shown) embedded in the lens frames 4 and 7. Have control. The lens frames 4 and 7 are shown in detail in the drawings described later. Reference numeral 31 is a stage drive means, which is a control means for positioning the wafer 27 at a predetermined position. Reference numerals 25, 26 and 30 are known focus position detection systems for measuring the height of the wafer 27 under the projection lens PL, of which 26 is a light projecting optical system and 25 is a light receiving optical system. The light emitted from the projection optical system 26 is emitted from the wafer 2
7 planes are incident at a low incident angle and are reflected on the wafer 27 plane,
It is incident on the light receiving optical system 25. The focus position control means 30 issues a command to the stage drive means 31 so that the incident position of the surface of the wafer 27 becomes a predetermined position.

Reference numeral 33 denotes an arithmetic means, which works in conjunction with the timer 32 to calculate the target values of the temperature control of the gas temperature and the lens peripheral temperature for each exposure process based on the values stored in the memory 34, and calculate them. It is sent to the temperature control means A21 and the temperature control means B24. Similarly, the calculation means 33 uses the timer 3
The target value is output to the focus position control means 30 based on the value stored in the memory 34 in association with 2.

FIG. 2 is a schematic view of the vicinity of the lens 10 shown in FIG. In the figure, reference numeral 45 denotes a lens frame ring, which is a main member constituting the lens frame 4 and uses a low thermal expansion material in order to suppress thermal expansion due to heating of the peripheral portion of the lens. Reference numeral 43 is a ring-shaped heater that warms the peripheral portion of the lens.

Reference numeral 42 denotes a ring member, which is made of a member having a high thermal conductivity in order to transfer the heat from the heater 43 to the lens and is in close contact with the heater 43. Reference numeral 44 is a thermometer, which is in contact with the lens in order to measure the temperature around the lens. Reference numeral 41 is a holding ring, which is a heater 43 and a ring member 4
2 is fixed to the lens frame ring 45 and is made of a low thermal expansion material. As shown in the figure, the surface of the lens 10 is cooled by the inflowing gas, and the periphery of the lens is warmed by the heater 43, so that the temperature distribution is flat as shown by the profile 81 in FIG.

FIG. 3 is a plan view of the vicinity of the lens 10 of FIG. 1, and particularly shows the vicinity of the lens space inflow of the supply pipe 15 and the exhaust pipe 16.

As shown in the figure, the supply pipe 15 and the exhaust pipe 16 are bifurcated near the lens space. A lens barrel 52 has holes for the supply pipe 15 and the exhaust pipe 16. Further, the gas flow in the lens space is controlled to be a laminar flow at the gas inlet (gas supply port) and the gas exhaust port, and the cooling gas is evenly flowed into the lens space to recover the gas.
0-40% punching plate (laminar flow means) 60
~ 63 are provided.

In this embodiment, if the lens barrel 52 has a structure capable of forming a large hole in its side surface,
A configuration as shown in FIG. 9 is also possible.

In FIG. 9, 64 is a lens barrel in this case, 65 is a supply pipe in this case, and 66 is an exhaust pipe in this case. Then, punching plates 67 and 68 are attached to the gas inflow port and the gas exhaust port in the same manner as in FIG. By providing laminar flow means such as a punching plate for laminar flow at the inlet and the exhaust port in this manner, even if particles flow into the lens space or particles are generated in the lens space, gas is generated. Since the flow is a laminar flow, it is promptly discharged out of the lens space.

In this embodiment, two lenses 10 and 13 are used to make the temperature distribution inside the lens flat, but the number of target lenses is not constant depending on the type of projection lens PL.

Next, the features of the basic constituent features of the present invention will be described before the operation of the present embodiment is described with reference to the flowchart of FIG.

In the projection exposure apparatus of the present invention, each lens absorbs part of the exposure light during exposure, so that a temperature distribution occurs in the lens in which the vicinity of the lens center is high and the peripheral portion of the lens is low. In our simulation, from the viewpoint of changes in optical performance, it is better to make the slope of the distribution as flat as possible rather than lower the absolute value of the temperature inside the lens, that is, lower the temperature at the center of the lens and raise the temperature around the lens. The change in aberration of the projection lens is gentler,
It is concluded that the degree is small.

FIG. 8 is an explanatory view of the temperature distribution in the lens in the radial direction. Referring to FIG. 8, when the apparatus is in thermal equilibrium after the exposure is started, the temperature distribution in the lens shows a curve 8.
It becomes like 0. In this state, when air (air) for air cooling is flown into the lens space, a temperature distribution of a curve 82 is obtained.
Further, a curve 81 shows the profile of the temperature distribution when air is passed through the lens in order to make the inclination of the temperature distribution of the lens flat and at the same time a little heat is applied to the periphery of the lens. At this time, the absolute value of the temperature of the curve 81 is the curve 82.
It has been obtained by simulation that the change in the optical performance of the projection lens is smaller in the case of the curve 81 than in the case of the curve 82, and the aberration is benign, even though the temperature is higher than the temperature of.

According to the present invention, on the basis of such a reason, the temperature distribution inside the lens caused by the absorption of the exposure light is temperature controlled so that the inclination is as small as possible. At the same time, a gas controlled to a predetermined temperature is caused to flow, and at the same time, heat is applied so that the peripheral portion of the lens has a predetermined temperature, and each temperature is independently controlled.

In practice, the following measures are taken. The temperature distribution and shape deformation due to energy absorption of each lens at the time of exposure are obtained in advance by experiments and simulations, and the contribution of each lens to the aberration such as the field curvature variation and magnification variation of the projection lens is calculated. Based on the result, the lens that largely contributes to the aberration variation is specified. There may be a single lens or a plurality of lenses depending on the type of projection lens and the illumination method. The lens is provided with heating means for heating the peripheral part of the lens in a ring shape, measuring means for measuring the temperature of the peripheral part of the lens, and lens temperature control means for controlling the peripheral part of the lens to a predetermined temperature based on the measured value. .

Further, the substrate supply / exhaust means for injecting and exhausting the gas into the space between the lenses of the target lens, the measuring means for measuring the temperature of the inflow gas, and the gas is controlled to a predetermined temperature based on the measured value. And a gas temperature control means. At the time of actual exposure, in order to make the temperature distribution inside the lens as flat as possible, use the exposure process parameters such as reticle transmittance, exposure energy, and exposure time per shot, and the control values calculated in advance and experimentally determined. The temperature around the lens and the temperature of the gas flowing into the lens space are linked and simultaneously controlled. The gas flowing in and out is constantly circulated in the closed system via the lens space by connecting the gas supply means and the gas exhaust means with a duct. Further, as the gas flowing into the lens space, it is possible to use an inert gas such as N ₂ or CO ₂ other than air.

By adopting such means, it is possible to prevent the deposition of a substance that causes a decrease in transmittance on the lens surface of the projection optical system and to prevent the lens from being exposed, which is one factor that affects the overlay accuracy of the apparatus. Provided is a projection exposure apparatus capable of effectively suppressing magnification variation and distortion variation of a projection lens due to energy absorption of exposure light and improving overlay accuracy. At the same time, the field curvature variation of the projection lens can be effectively suppressed, so that the depth of focus is sufficiently long within the lens angle of view even in the process with many steps. Next, the operation of the present invention will be described with reference to the flowchart of FIG.

First, the ultra-high pressure mercury lamp in the illumination system is turned on (100). Next, the gas supply means 18 and the gas exhaust means 2
2 starts operating, and lens spaces 35, 36, 38, 39
Predetermined gas is sent to (101). The gas sent in is collected by the gas exhausting means 22, and thereafter circulates in the closed system to keep a clean state at all times, and the lenses 10, 13
Control the temperature of. At this time, the temperature TOgas (initial temperature) of the inflowing gas and the lens peripheral temperature TOlens are controlled to the standard temperature which is the temperature inside the chamber of the apparatus because the exposure has not started yet (102). Next, the wafer 27 is set to the initial focus position Z0stg stored in advance in the memory 34 by the focus position control means 30 and the stage drive means 31 (104). The exposure number counter ΔN is set to 0 (105).

Next, the wafer is globally aligned, and the wafer is aligned with the first shot coordinates (106, 107). Here, prior to the exposure, whether the product of the exposure energy Eexpo, the reticle transmittance Rrtcl, the exposure time Texpo and the exposure number counter ΔN (0 at this point) in the current exposure process is larger or smaller than a certain value. A diagnosis is made (108). This is to determine whether the exposure energy accumulated in the projection lens affects the optical characteristics of the projection lens and the inflow gas temperature Tgas and the lens peripheral temperature Tlens need to be controlled (at this point of time). Of course, no need for control). This diagnostic step 108 is completed, 1 is added to the exposure number counter ΔN (112), the shutter in the illumination system is opened (113), and the shutter is closed (114), whereby the exposure of the first shot is completed.

Next, the stage 29 moves to predetermined coordinates according to the measured value of the global alignment for the second shot (107). After the diagnosis step 108, the value of the exposure number counter ΔN is set to 2 (112), and the shutter opening / closing operation (113, 114) completes the exposure of the second shot. When a series of these operations is repeated several times, a part of the energy of the exposure light is gradually accumulated in the projection lens and the optical characteristics change. When the value of E · R · T · ΔN exceeds a certain value according to the diagnosis step 108,
Prior to exposure, the optical performance correction operation starts. That is, the gas temperature Tgas is controlled by the temperature control means A21 for controlling the temperature of the gas and the temperature control means B24 for controlling the temperature around the lens so that the temperature distribution inside the lenses 10 and 13 becomes flat.
And the lens surrounding temperature Tlens is controlled to a predetermined value (10
9).

However, although this control is effective in suppressing the variation of the magnification, distortion, and field curvature of the projection lens, it cannot follow the variation of the focus position, so the focus position control means 30 sets the wafer to a predetermined height Zstg. 27 is controlled (11
0). These three control command values Tgas, Tlens, Zst
Although g varies depending on each exposure process, since it is stored in the memory 34 as a coefficient for the change in optical characteristics by simulation and experiment in advance, it is calculated for each exposure process by the calculation means 33 and the control means 21,
Sent to 24, 30. When these three controls are completed, the exposure counter is reset to 0 (111), and the normal exposure operation starts again (112, 113, 11).
4).

While repeating this series of operations, the exposure operation proceeds while the projection lens always maintains good optical characteristics. When exposure of all shots is completed (115), the wafer is exchanged (116), the process returns to the step of wafer alignment 106 again, the exposure operation of the second wafer is started, and the same operation is repeated thereafter.

In this embodiment, by adopting such a relatively simple structure, it is possible to affect the overlay accuracy of the apparatus without adhering to the lens surface of the projection optical system a substance that causes a decrease in transmittance. Variation in magnification of the projection lens due to absorption of energy of exposure light of the lens during exposure, which is a factor
Provided is a projection exposure apparatus capable of effectively suppressing distortion variation and improving overlay accuracy. At the same time, the field curvature variation of the projection lens can be effectively suppressed, so that the required depth of focus can be ensured within the lens angle of view even in the process having many steps.

FIG. 5 is a schematic view of the essential parts of a second embodiment of the projection exposure apparatus of the present invention, and FIGS. 6 and 7 are explanatory views of a part of FIG. In this embodiment, as a result of previously calculating temperature distribution and shape deformation due to energy absorption of exposure light of each lens at the time of exposure, optical characteristics changes such as field curvature variation and magnification variation of the projection lens are almost the same in each lens. It is suitable for the case.

This embodiment is different from Embodiment 1 in FIG. 1 in that light is used for the heating means around the lens. In FIG. 5, the same members as those in the first embodiment shown in FIG. 1 are designated by the same reference numerals.

In FIG. 5, reference numerals 92 and 93 denote 45 ° mirrors inclined at 45 °. Reference numerals 90 and 91 denote ring illuminators, which are connected to the projection lens PL via 45 ° mirrors 92 and 93.
The peripheral part of each lens is illuminated in a ring shape. Therefore, the direction of the illumination light emitted from the ring illumination units 90 and 91 is changed by 90 ° by the 45 ° mirrors 92 and 93, and the projection lens PL
To the wafer 27 while penetrating only the peripheral portion thereof. The ring illuminators 90 and 91 are composed of a halogen lamp and an optical system for illumination, and the light having a wavelength near the exposure light is removed by a filter in advance. I try not to expose it.

In FIG. 5, only two sets of the ring illuminators 90 and 91 and the 45 ° mirrors 92 and 93 are shown.
Actually, four ring illumination units and a 45 ° mirror are arranged so that the peripheral portion of the projection lens PL can be illuminated. Further, since the heating means around this lens works for all the lenses of the projection lens PL, it is necessary to flow the cooling gas into all the lens spaces 35 to 40, and the supply pipe 15a and the exhaust pipe 16a are provided as shown in the figure. ing. The temperature control means B24 monitors the temperature of all PL lenses of the projection lens, and the current supply means 23 of the ring illuminators 90 and 91 are based on control values calculated in advance and obtained by experiments.
By controlling a, the optimum intensity of the halogen lamp is adjusted so that the temperature distribution inside each lens becomes flat.

FIG. 6 is a plan view of the arrangement of the ring illuminator and the 45 ° mirror of FIG. 5, viewed from above the projection lens PL.
In this figure, the ring illuminator and 45 ° mirror are 90 and 9 respectively.
Four sets of 2, 93 and 91, 94 and 96, 95 and 97 are arranged to illuminate the projection lens PL. Of course, the number of combinations is not limited to four, but may be six or eight, and the larger the number, the more uniformly the lens can be illuminated in a ring shape.

FIG. 7 is a view corresponding to FIG. 2 of the first embodiment and shows the lens frame 4. In the figure, reference numeral 45a denotes a lens frame ring, which is a main member constituting the lens frame and is in contact with a thermometer for measuring the ambient temperature of the lens.

In this embodiment, since the ring illumination using light is used as the heating means around the lens, the lens frame does not need to have the complicated structure as in the first embodiment, and has a characteristic that the structure is simple. . As shown in the figure, the surface of the lens 10 is cooled by the inflowing gas, and the periphery thereof is warmed by the non-exposure light, so that the temperature distribution becomes flat as shown by the profile 81 in FIG. The operation of the device according to the present embodiment is substantially the same as the operation of the first embodiment, and only the control command value to the ring illumination unit is changed.

By adopting the structure of this embodiment, when the efficiency of each lens with respect to the change in the optical characteristics of the projection lens due to the absorption of the exposure light is about the same, the internal temperature distribution of all the lenses can be collectively controlled. Therefore, it is possible to easily suppress variations in the optical characteristics of the projection lens. Also, since it is not necessary to embed a heater inside the lens frame, there is no need to consider the thermal expansion of the lens barrel, and because the configuration of the lens frame is simple, the projection lens can be assembled and adjusted in the same manner as in the past. There are advantages.

In the first and second embodiments of the projection exposure apparatus of the present invention described above, the method of selectively using the two embodiments differs depending on the projection lens, and the contribution of each lens to the change in the optical characteristics of the projection lens is calculated beforehand. Calculate,
As a result, it is preferable to use the first embodiment when the lens is deviated to the specific lens and to use the second embodiment when the contribution is relatively the same in each lens.

Next, an embodiment of a method for manufacturing a semiconductor device (semiconductor element) using the above-described exposure apparatus will be described.

FIG. 10 shows a flow of manufacturing a semiconductor device (semiconductor chip such as IC or LSI, or liquid crystal panel, CCD or the like). In step 1 (circuit design), the circuit of the semiconductor device is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured.

On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by a lithography technique using the mask and the wafer prepared above.

The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip by using the wafer manufactured in step 4, an assembly process (dicing, bonding), a packaging process (chip encapsulation). Etc. are included. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 11 shows the detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the exposure apparatus described above.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. In step 19 (resist peeling), the resist that has become unnecessary due to etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device which has been difficult to manufacture in the past.

[0060]

According to the present invention, by adopting the above-mentioned structure, even when the lens forming the projection optical system absorbs the exposure light, the aberration change is effectively corrected and the optical characteristics are improved. The present invention achieves a projection exposure apparatus and a method of manufacturing a semiconductor device using the projection exposure apparatus, which maintains a high resolution and obtains a projected pattern image with high resolution.

In particular, according to the present invention, the temperature distribution and the shape deformation due to the exposure light energy absorption of each lens during exposure are calculated in advance, and the contribution of each lens to the fluctuation of the optical characteristics of the projection lens is calculated. Based on the result, in one or more lenses, the peripheral portion of the lens is heated in a ring shape to a predetermined temperature, a gas of a predetermined temperature is flown into and exhausted from the lens space of those lenses, and these two temperatures are controlled in conjunction with each other. This allows the temperature distribution inside the lens to be kept flat at all times, which is a factor affecting the overlay accuracy of the device. It is possible to provide a projection exposure apparatus capable of suppressing fluctuations and improving overlay accuracy.

At the same time, the variation of the field curvature of the projection lens can be effectively suppressed, so that the required depth of focus can be ensured within the lens angle of view even in the process having many steps. Also, the cooling gas circulates in the closed system,
Since it is possible to suppress the generation of a reaction substance due to the photochemical reaction of a molecule in the atmosphere with the exposure light, it is possible to prevent the adhesion of the substance that causes the transmittance phenomenon to the lens surface of the projection optical system. A projection exposure apparatus has been achieved.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a part of FIG.

FIG. 3 is an explanatory view of a part of FIG.

FIG. 4 is a flowchart of Embodiment 1 of the projection exposure apparatus of the present invention.

FIG. 5 is a schematic view of the essential portions of Embodiment 2 of the projection exposure apparatus of the present invention.

FIG. 6 is an explanatory view of a part of FIG.

FIG. 7 is an explanatory diagram of a part of FIG.

FIG. 8 is an explanatory diagram for explaining the temperature distribution inside the lens.

9 is an explanatory diagram in which a part of FIG. 3 is modified.

FIG. 10 is a block diagram of essential parts of a method for manufacturing a semiconductor device of the present invention.

FIG. 11 is a flowchart of a method for manufacturing a semiconductor device of the present invention.

[Explanation of symbols]

 PL Projection lens 9-14 Lens 35-40 Lens space 3-8 Lens frame 50 Illumination system 1 Circulation pipe 2 Lens barrel 51 Reticle 18 Gas supply means 19 Heat exchange means 21 Temperature control means A 20 HEPA filter 22 Gas exhaust means 23 , 23a Current supply means 24 Temperature control means B 27 Wafer 26 Projecting optical system 25 Light receiving optical system 30 Focus position controlling means 31 Stage driving means 33 Computing means 43 Heater 52, 64 Mirror with inlet and outlet 44, 44a Lens thermometer 45, 45a Lens frame ring 60-63, 67, 68 Punching plate 90, 91, 96, 97 Ring illumination unit 92-95 45 ° mirror

Claims (8)

[Claims] 1. In a projection exposure apparatus for projecting and exposing a pattern on a first object plane onto a second object plane by a projection optical system, heating for heating at least one lens peripheral portion constituting the projection optical system in a ring shape. Means, lens temperature control means for controlling the lens peripheral portion to a predetermined temperature, gas supply and exhaust means for supplying and exhausting gas to and from a plurality of lens spaces sandwiched by the lenses forming the projection optical system, A gas temperature control means for controlling the gas to a predetermined temperature is provided, and the lens temperature control means and the temperature control by the gas temperature control means are interlocked to operate at a predetermined temperature. And a projection exposure apparatus. 2. The gas supply / exhaust means connects a gas supply means for supplying gas into the lens space and a gas exhaust means for exhausting gas by a duct, and the gas is supplied in a closed system through the lens space. The projection exposure apparatus according to claim 1, which is circulated. 3. The gas supply / exhaust means has a laminar flow means for forming a laminar flow of gas in each of a supply port for supplying the gas into the lens space and an exhaust port for exhausting the gas. The projection exposure apparatus according to claim 2. 4. The projection exposure apparatus according to claim 1, wherein the gas is air, N ₂ or CO ₂ . 5. A projection optical system is used to project and expose a pattern on a reticle surface onto a wafer surface, and then, at the time of manufacturing a semiconductor element through the wafer, a at least one projection optical system is formed. The lens peripheral part is heated in a ring shape by the heating means, and at this time, the lens peripheral part is controlled by the lens temperature control means so that the lens peripheral part has a predetermined temperature, and a plurality of lenses sandwiched between the lenses constituting the projection optical system. When the gas is supplied to and exhausted from the space by the gas supply / exhaust means, and the gas temperature control means controls the gas to have a predetermined temperature at this time, the temperature control by the lens temperature control means and the gas temperature control means is performed in advance. A method of manufacturing a semiconductor device, which uses a step of operating in conjunction with each other so as to reach a set predetermined temperature. 6. The gas supply / exhaust means connects a gas supply means for supplying gas into the lens space and a gas exhaust means for exhausting gas by a duct, and the gas is supplied in a closed system through the lens space. The method of manufacturing a semiconductor device according to claim 5, wherein the method is circulating. 7. The gas supply / exhaust means has a laminar flow means for making a laminar flow of gas in each of a supply port for supplying gas into the lens space and an exhaust port for exhausting gas. The method of manufacturing a semiconductor device according to claim 6. 8. The method of manufacturing a semiconductor device according to claim 5, wherein the gas is air, N ₂ or CO ₂ .