JP2897346B2 - Projection exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a projection exposure apparatus, and more particularly to a projection optical system in which an electronic circuit pattern on a reticle surface is projected onto a wafer surface when a semiconductor device such as an IC or LSI is manufactured. The present invention relates to a projection exposure apparatus capable of satisfactorily correcting optical performance such as a distortion error and a projection magnification error when performing projection to obtain a highly accurate projection pattern image.

(Prior Art) Conventionally, a printing apparatus (aligner) for manufacturing semiconductor elements such as ICs and LSIs has been required to have extremely high assembly accuracy and optical performance.

Of these, the matching accuracy when the reticle on which the electronic circuit pattern is formed and the wafer are superposed is particularly important. One factor that most affects the matching accuracy is a projection magnification error and a distortion error of the projection optical system. The projection magnification error and the distortion error appear as a difference between a desired grid point and a grid point of the projection pattern. Applicant filed Japanese Patent Application Laid-Open
Japanese Patent Application No. 35620 proposes an aligner having means for reducing the image distortion error using optical means and correcting the projection magnification.

By the way, the pattern dimensions used for recent aligners have been miniaturized year by year, and accordingly, higher matching accuracy has been required. Therefore, there is a demand for further reducing the projection magnification error and the distortion error of the projection optical system.

The projection magnification error and distortion error of the current projection optical system are corrected by adjustment in the manufacturing process of the projection optical system and adjustment at the time of installation of the apparatus.

(Problems to be Solved by the Invention) However, a projection magnification error, a distortion error, and the like of the projection optical system change depending on an assembly error and a surrounding environment, particularly, atmospheric pressure and temperature. Also, the projection optical system absorbs exposure energy when exposing the wafer, and the optical elements (for example, refractive index and shape) change,
This also changes the projection magnification error, distortion error, and the like.

It is difficult to satisfactorily correct both of these optical performances, and in a conventional projection exposure apparatus, a distortion error due to, for example, atmospheric pressure, temperature change, light absorption, etc. remains, or a distortion error occurs when correcting a projection magnification error. It is very difficult to completely correct both the projection magnification error and the distortion error due to the occurrence.

It is an object of the present invention to provide a projection exposure apparatus capable of satisfactorily correcting both a projection magnification error and a distortion error when projecting a pattern on a reticle surface onto a wafer surface by a projection optical system and easily obtaining high optical performance. And

(Means for Solving the Problems) A projection exposure apparatus according to the present invention includes: (1-1) a projection exposure apparatus having a projection optical system for projecting a pattern of a first object onto a second object with exposure light. Adjusting means for adjusting the optical characteristics of the projection optical system, the adjusting means changing the wavelength of the exposure light to change the distortion and the projection magnification of the projection optical system; The optical system has a refractive index changing means for changing the distortion and projection magnification of the projection optical system by changing the refractive index of the gas in the closed space provided in the optical system, the wavelength changing means and the refractive index changing means Is used to adjust the distortion and the projection magnification of the projection optical system.

In particular, there is provided: (1-1-1) a pressure sensor for detecting a pressure around the projection optical system, wherein the adjusting means adjusts a distortion of the projection optical system due to a pressure change according to a signal from the pressure sensor. And the change in the projection magnification.

(1-1-2) a temperature sensor for detecting a temperature of the projection optical system, wherein the adjusting means projects a change in distortion of the projection optical system due to a temperature change in accordance with a signal from the temperature sensor; To correct for changes in magnification.

(1-1-3) The exposure light is a laser beam.

Further, the method of manufacturing a semiconductor device according to the present invention is characterized in that it includes the step of (2-1) transferring a circuit pattern onto a substrate by the projection exposure apparatus having the configuration (1-1).

Embodiment FIG. 1 is a schematic view showing an embodiment of the projection exposure apparatus of the present invention.

In FIG. 1, 1 is a reticle as a first object on which a circuit pattern is drawn, 2 is a reticle chuck for holding a reticle 1 by suction, 3 is a reticle stage that supports a reticle chuck 2, and 4 is a reduced projection lens system. , 5, 6 and 7 are partial lens systems constituting the projection lens system 4, respectively. Reference numeral 8 denotes a space in the partial lens system which is shielded from the outside air, 9 denotes a wafer as a second object coated with a photosensitive material such as a resist, 10 denotes a wear chuck for sucking and holding the wafer 9, and 11 denotes a wafer chuck. It is a wafer driving device.

The wafer driving device 11 includes, for example, a piezoelectric element or the like, and displaces the wear chuck 10 in the optical axis AX direction of the projection lens system 4 to move the wafer 9 in the optical axis AX direction. Reference numeral 12 denotes a wafer stage that supports the wafer driving device 11 and is movable in a plane orthogonal to the optical axis AX of the projection lens system 4.

Driving of the wafer chuck 10 by the wafer driving device 11 is performed based on a signal from the wafer drive control system 13, and at this time, the position of the (surface of) the wafer 9 in the optical axis AX direction is detected by the focus detector 18. The focus detector 18 is composed of, for example, an air sensor or an optical sensor conventionally used in this type of projection exposure apparatus. The signal from the focus position detector 18 is a microprocessor
Entered into 23. On the other hand, the atmospheric pressure around the projection lens system 4,
An air pressure sensor 19, a temperature sensor 20, and a humidity sensor 21 are provided to detect changes in temperature and temperature, and a lens temperature sensor 22 is provided to detect a temperature change due to light absorption of the projection lens system 4. These various sensors 1
Signals from 9, 20, 21, and 22 are also input to the microprocessor 23.

The space 8 in the lens system shielded from the outside air is
A pressure sensor 17 for measuring the internal pressure (atmospheric pressure) and a pressure control device 14 for controlling the pressure in the space 8 are connected. Then, a constant pressure is constantly supplied to the pressure control device 14 from the pressurizing supply device 16B through the filter 16A, and the pressure is released by the exhaust device 15 as needed. A signal from the pressure sensor 17 for detecting the pressure in the space 8 is also input to the microprocessor 23.

Note that the wafer drive system 13 and the pressure control device 14 are controlled by signals from the microprocessor 23. Of the above, each of the elements 14, 15, 17, and 23 constitutes a part of the air pressure adjusting means.

Reference numeral 24 denotes an illumination system for illuminating the circuit pattern of the reticle 1 with uniform illuminance. The illumination system 24 includes a KrF excimer laser that emits a laser beam having a wavelength λ = 248.4 nm as a light source for exposure. The laser light from the illumination system 24 is directed onto the wafer 9 via the reticle 1 and the projection lens system 4, and the circuit pattern image of the reticle 1 is projected on the wafer 9.

In the present embodiment, in order to perform projection exposure with laser light having a wavelength in the far ultraviolet region, each lens constituting the projection lens system 4 is made of synthetic quartz (SiO 2) having a high transmittance for light having a wavelength λ = 248.4 nm. ₂ ) Manufactured in.

Next, each element of the illumination system 24 in the present embodiment will be described. Reference numeral 27 denotes a laser light source, which emits a light beam whose oscillation wavelength is controlled by a wavelength selection element drive control system 32 described later. 25 is a condenser lens, a laser light source
The light beam from 27 is reflected by a mirror 26 to uniformly illuminate the reticle 1 surface.

The laser light source 27 includes a laser resonator 28 and a wavelength selection element 29.
have. Reference numeral 30 denotes a wavelength selection element driving device, 31 denotes a wavelength selection element angle detector, and 32 denotes a wavelength selection element drive control system.

FIG. 2 is a schematic view of a main part of the laser light source 27 of FIG. The wavelength selection element 29 can narrow the wavelength band by using a prism, a grating, an etalon, or the like. At the same time, it is possible to change the wavelength within the original wavelength band of the laser resonator by changing the angles of the reflecting mirror, grating and etalon after the prism.

The wavelength selection element driving device 30 is composed of a step motor, a piezoelectric element, or the like, and is driven based on a signal from the wavelength selection element drive control system 32. At this time, the angle of the wavelength selection element 29 is detected by the wavelength selection element angle detector 31. The wavelength selection element angle detector 31 can be composed of various angle detectors such as an optical encoder. The signal from the wavelength selection element angle detector 31 is input to the microprocessor 23. The wavelength selection element drive control system 32 is controlled by the microprocessor 23.

In the present embodiment, the oscillation wavelength from the laser light source 27 is changed independently of the projection lens system 4 as described later to simplify the entire apparatus with the above configuration.

FIG. 3 is a lens sectional view of a specific lens configuration of the projection lens system 4 of FIG. During the reticle 1 and the wafer 9 in the figure, reference numeral G ₁ 12 Like the lens shown in ~G ₁₂ is arranged along the optical axis AX projection lens system 4 is constructed.

Table 1 shows the lens data of the projection lens system shown in FIG. In Table _{-1, R i (i = 1~24} ) Part of the i-th surface of a curvature radius counted from the reticle 1 side in this order (mm), D _i is the i-th counted from the reticle 1 side in this order and The on-axis wall thickness or on-axis air space (mm) between the (i + 1) th plane is expressed by N _i (i = 1 to 1).
2) is the refractive index of the lens G _{i (i} = 1~12). Also, S ₁
Reticle 1 of the circuit pattern surface and the lens G ₁ of the reticle 1
S ₂ is the lens G ₁₂
3 shows the axial air gap between the lens surface on the wafer 9 side and the surface of the wafer 9.

Table -2 is changed by the lens system G _i and _{G i + 1 (i = 1~11} ) of the space between the air pressure (pressure) + 137.5mmHg adjacent to each other in the projection lens system shown in Table 1 When the relative refractive index is changed to 1.00005, the oscillation wavelength λ from the laser light source 27 of the illumination system 24 is set to +0.
A shift amount ΔSD (hereinafter, referred to as a “symmetric distortion change amount ΔSD”) accompanying a change in the symmetric distortion of the image point at a position of an image height of 10 mm on the image plane of the projection lens system when the distance is changed by 1 nm, and projection. A shift amount Δβ (hereinafter referred to as “projection magnification change amount Δβ”) accompanying a change in magnification and a ratio | ΔSD / Δβ | Note that the image point shifted in a direction away from the optical axis of the projection lens system is positive, and the image point shifted in a direction approaching the optical axis of the projection lens system is denoted by a negative sign.

In the present embodiment, the space D _2i (i = 1 to 11) based on Table-2
Wavelength λ and other one or two of the two variables
The feature is that both the projection magnification and the distortion (hereinafter, also referred to as “symmetric distortion”) are adjusted by adjusting the values of the space as one or more variables.

Now, let two variables be X and Y, and let each change amount be ΔX,
Let ΔY. Further, the change amounts of the symmetric distortion corresponding to Table 2 of the respective variables are represented by ΔSD _X and ΔSD _Y , and the change amounts of the projection magnification are represented by Δ
_Let β _X and Δβ _Y be the amount of change in symmetric distortion ΔSD _{TOT in the} whole system
And the change in projection magnification Δβ _TOT can be expressed by the following equations.

Therefore, ΔX and ΔY are given by the following equations.

From the equation (2), a distortion error ΔSD _TOT and a projection magnification error Δ
When β _TOT occurs, the space D _2i (i = 1 to 11) and the wavelength λ
When two variables X and Y are selected, the amounts ΔX and ΔY to be changed are obtained from equation (2), and the distortion error and the projection magnification error can be corrected simultaneously.

Next, a method of correcting a projection magnification error and a distortion error when the pattern on the reticle 1 is projected onto the wafer 9 in the projection exposure apparatus shown in FIG.

The microprocessor 23 is programmed in its memory with formulas for obtaining the projection magnification change amount Δβ _TOT and the distortion change amount ΔSD _TOT of the projection lens system 4. The calculation formulas are atmospheric pressure, temperature, humidity, and projection lens, respectively. The amount of change in the temperature of the system 4 from a predetermined reference value is a variable. The memory is also programmed with the above formula (2). By substituting the values of Δβ _TOT and ΔSD _TOT into the formula (2), the amounts ΔX, Δ
Find Y.

The formulas for calculating the values of Δβ _TOT and ΔSD _TOT based on atmospheric pressure, air temperature, humidity, and temperature changes of the projection lens system 4 can be derived by experiments.

On the other hand, the focus position of the pattern image by the projection lens system 4 changes depending on the atmospheric pressure, the temperature, the humidity around the projection lens system 4 and the temperature of the projection lens system 4, and in addition to this, the setting of the variables X and Y It changes depending on the state. Therefore, in this embodiment, a calculation formula for calculating the focus position fluctuation amount of the projection lens system 4 is programmed in the memory of the microprocessor 23 based on these fluctuation factors, and the focus position is accurately grasped based on this calculation formula. I am trying to do it.

The microprocessor 23 receives the signals corresponding to the atmospheric pressure, the temperature, the humidity, and the lens temperature from the barometric pressure sensor 19, the temperature sensor 20, the humidity sensor 21, and the lens temperature sensor 22, and receives the variables X and The amounts ΔX and ΔY of the variable Y to be changed are obtained.

On the other hand, signals corresponding to the setting states of the variables X and Y from the position detectors of the variables X and Y (the wavelength selection element angle detector 31 and the pressure sensor 17) are microprocessor signals.
Entered into 23. The microprocessor 23 sends signals corresponding to the amounts .DELTA.X and .DELTA.Y to be changed of the variables X and Y to a drive control system (a wavelength selection element drive control system) for the variables X and Y.
32 and pressure controller 14). Then, each drive control system of the variables X and Y gives a predetermined control signal to each drive device, and the variables X and Y are driven by the amounts ΔX and ΔY to be changed. By driving the variables ΔX and ΔY, the projection magnification error and the distortion error of the pattern image based on the fluctuations of the atmospheric pressure, the temperature, the humidity around the projection lens system 4 and the temperature of the projection lens system 4 are corrected.

The microprocessor 23 projects based on the signals from the variable X and variable Y detectors (the angle detector 31 and the pressure sensor 17), the barometric pressure sensor 19, the temperature sensor 20, the humidity sensor 21, and the lens temperature sensor 22. The focus position of the pattern layer by the lens system 4 is detected, and based on a signal corresponding to the position of (the surface of) the wafer 9 from the focus position detector 18, the wafer drive control system is set so that the wafer 9 is positioned at the focus position. Control 13 The wafer drive control system 13 gives a predetermined control signal to the wafer drive device 11,
The wafer 9 is moved in the optical axis AX direction by the wafer driving device 11 to position the wafer 9 at the focus position of the pattern image.

With the operation described above, the projection magnification of the pattern image is corrected to a predetermined magnification, and the distortion of the pattern image is suppressed within a predetermined allowable range. Can be accurately superimposed. Further, since the position of the wafer 9 and the focus position of the pattern image can be matched, a clear pattern image can be projected on the wafer 9.

In the present embodiment, the projection magnification of the pattern image and the atmospheric pressure of the distortion,
The output signals from the barometric pressure sensor 19, the temperature sensor 20, the humidity sensor 21, and the lens temperature sensor 22 were used to detect changes due to changes in temperature, humidity, and lens temperature. The projected or recorded pattern image on the medium that does not need to be developed may be imaged by an imaging device, and changes in the projection magnification and distortion error of the pattern image may be detected based on the size and shape of the pattern image.
At this time, if the developing device is attached to the wafer stage 12,
Changes in projection magnification and distortion of the pattern image can be detected at a desired time, and the configuration of the projection exposure apparatus does not become complicated.

In this embodiment, the case where two variables are used to correct the projection magnification error and the distortion error is shown, but the correction may be performed using three or more variables. The method using three or more variables is effective when there is a limit to the variable drive amount. At this time, if a parameter having a small variation in other aberrations, such as coma and curvature of field, is selected, or a combination that cancels out a specific aberration is selected, the aberration of the entire system is favorably maintained.

Further, in this embodiment, instead of controlling the refractive index of the air by changing the air pressure (pressure) of the air in the space cut off from the outside air, a gas such as N ₂ or CO ₂ is sealed in the space, Even if the above gases are mixed and the partial pressure is controlled to change the refractive index in the space, the same effect as described above can be obtained.

Further, the same effect as described above can be obtained even if a plurality of spaces or a plurality of spaces are connected to each other in FIG. 1 to control the atmospheric pressure and the like in the spaces.

It should be noted that the control of the atmospheric pressure naturally includes keeping the pressure of the space isolated from the outside air constant.

(Effects of the Invention) According to the present invention, at least one space shielded from the outside air is provided in the lens system of the projection optical system, and the atmospheric pressure (pressure) or / and the mixing ratio of the gas in the space are changed. By changing the oscillation wavelength of the luminous flux from the illumination system,
The projection magnification and distortion of the pattern image projected by the projection optical system on the pattern drawn on the first object can be accurately adjusted.
Therefore, even if the projection magnification or distortion of the pattern image changes due to a change in atmospheric pressure or temperature around the projection optical system and an error occurs, both the projection magnification error and the distortion error of the pattern image can be satisfactorily corrected. A projection exposure apparatus can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of the projection exposure apparatus of the present invention, FIG. 2 is an explanatory view of the laser light source of FIG. 1, and FIG. 3 is a specific lens configuration of the projection lens system of FIG. FIG. In the drawing, 1 is a reticle, 2 is a reticle chuck, 3 is a reticle stage, 4 is a projection lens system, 5, 6, and 7 are partial lens systems, 8 is a space shielded from outside air, 9 is a wafer, 10 is a wafer chuck, 11 is a wafer drive device, 12 is a wafer stage, 13 is a wafer drive control system, 14 is a pressure control device, 15 is an exhaust device, 16A is a filter, 16B is a pressurized supply device, 17 is a pressure sensor, and 18 is a focus position detection. Vessel, 19 is a pressure sensor, 20 is a temperature sensor, 21 is a humidity sensor, 22 is a lens temperature sensor, 23 is a microprocessor, 24 is a lighting system,
25 is a condenser lens, 26 is a mirror, 27 is a laser light source, 28 is a laser resonator, 29 is a wavelength selection element, 30 is a wavelength selection element driving device, 31 is a wavelength selection element angle detector, and 32 is a wavelength selection element drive control System.

Continuation of front page (56) References JP-A-4-30411 (JP, A) JP-A-3-88317 (JP, A) JP-A-2-228658 (JP, A) JP-A-2-81019 (JP) JP-A-2-66510 (JP, A) JP-A-1-181520 (JP, A) JP-A-64-82527 (JP, A) JP-A-64-10624 (JP, A) 63-213341 (JP, A) JP-A-62-296514 (JP, A) JP-A-62-258414 (JP, A) JP-A-62-241329 (JP, A) JP-A-61-32613 (JP, A) A) JP-A-61-111529 (JP, A) JP-A-61-67036 (JP, A) JP-A-60-262421 (JP, A) JP-A-60-214334 (JP, A) -256636 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (5)

(57) [Claims] 1. A projection exposure apparatus having a projection optical system for projecting a pattern of a first object onto a second object with exposure light,
Adjusting means for adjusting the optical characteristics of the projection optical system, the adjusting means changing a wavelength of the exposure light to change a distortion and a projection magnification of the projection optical system; A refractive index changing unit that changes a refractive index of a gas in an enclosed space provided in the projection optical system to change distortion and a projection magnification of the projection optical system, the wavelength changing unit and the refractive index changing unit. A projection exposure apparatus for adjusting distortion and projection magnification of the projection optical system using 2. An apparatus according to claim 1, further comprising a pressure sensor for detecting an atmospheric pressure around said projection optical system, wherein said adjusting means controls a change in distortion of said projection optical system due to a change in atmospheric pressure in response to a signal from said pressure sensor. 2. The projection exposure apparatus according to claim 1, wherein a change in magnification is corrected. A temperature sensor for detecting a temperature of the projection optical system, wherein the adjusting means adjusts a change in distortion of the projection optical system and a change in projection magnification due to a temperature change in accordance with a signal from the temperature sensor. 2. The projection exposure apparatus according to claim 1, wherein the change is corrected. 4. The projection exposure apparatus according to claim 1, wherein said exposure light is a laser light. 5. A method for manufacturing a semiconductor device, comprising a step of transferring a circuit pattern onto a substrate by the projection exposure apparatus according to claim 1.