JP3218654B2 - EXPOSURE APPARATUS, EXPOSURE METHOD, AND METHOD OF MANUFACTURING MICRODEVICE USING THE EXPOSURE METHOD - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection apparatus which enables an exposure method for increasing the apparent depth of focus of a projection optical system when a fine pattern is projected and exposed on a photosensitive substrate.

[0002]

2. Description of the Related Art Conventionally, as this type of projection exposure apparatus, for example, one disclosed in Japanese Patent Application Laid-Open No. 63-64037 is known. In this publication, a resist layer formed on the surface of a semiconductor wafer and an image plane of a projection optical system for projecting a reticle pattern are relatively moved in an optical axis direction to perform a multiple exposure, thereby developing a developed resist. It is disclosed that an image has image quality as if it was transferred via a projection optical system having a large depth of focus. In this case, in the apparatus disclosed in the above publication, after performing the first exposure, the Z stage holding the wafer is moved by a fixed amount in the optical axis direction, and then the second exposure is performed with the same reticle pattern. ing. Further, the step position of the Z stage in the optical axis direction is 2
It is shown that it may be more than the point.

[0003] Similarly, as a method of obtaining the effect of increasing the apparent depth of focus, Japanese Patent Laid-Open No. 58-1744 discloses a method.
As disclosed in Japanese Unexamined Patent Application Publication No. 6-2006, there is also known a method of vibrating the wafer in the optical axis direction during a one-shot exposure operation on the wafer. In this case, the above publication does not specify the waveform of the vibration, but considering general sinusoidal vibration, by setting the vibration amplitude and frequency to appropriate values, the above-mentioned JP-A-63-64037 can be used. The effect of expanding the depth of focus can be obtained in exactly the same manner as in the publication.

[0004]

However, of the above two prior arts, in the method of performing exposure at each of a plurality of points separated from each other in the optical axis direction, a shutter for completing exposure of one shot on a wafer is used. As a result, the number of times of opening / closing operations increases, and there arises a problem that the throughput inevitably decreases. In the method of exposing the wafer while oscillating the wafer, the shutter needs to be opened and closed only once. Instead, it is necessary to set the oscillation frequency during the opening time of the shutter to be an integral multiple. Further, in the above two prior arts, in the case of the vibration method, the position of the vibration center to be accurately set in the optical axis direction is determined. There is no explicit disclosure of how to guarantee the position of the surface relative to the wafer surface. For this reason, in the prior art, control accuracy and throughput in the optical axis direction (Z direction) have been extremely unsatisfactory.

The present invention has been made based on such a demand, and it is an object of the present invention to provide a projection exposure apparatus which improves the throughput and significantly improves the position control accuracy and reproducibility in the optical axis direction. Aim.

[0006]

According to the first aspect of the present invention, there is provided an exposure apparatus for exposing an image of a pattern on a mask (R) illuminated with illumination light onto a first exposed portion (W). , First
Exposure means (40-) for exposing a portion to be exposed (first shot)
42) and changing means (18-2) for changing the relative distance between the pattern image and the first exposed portion in the optical axis direction of the illumination light.
0, 30, 102) and the relative interval obtained by exposing the first exposed portion until the exposure amount of the first exposed portion reaches an appropriate exposure amount while changing the relative interval by the changing means. Acquiring means (CPU 300) for acquiring information related to the change of the information, and a second exposed part (second part) different from the first exposed part based on the information acquired by the acquiring part.
Control means (CPU 300) for controlling the exposure operation of the exposure means for the shot) and the operation of the change means. Further, in the invention according to claim 2, the mask (R)
The pattern above is illuminated with illumination light and the image of the pattern is
An exposure method using an exposure apparatus that exposes a portion to be exposed (a first shot) by changing a relative distance in the optical axis direction of illumination light between the first portion to be exposed and an image of a pattern.
Exposing the first portion to be exposed until the amount of exposure to the first portion to be exposed reaches a proper exposure amount, and obtaining information related to the change in the relative interval obtained by the exposure with the change in the relative interval; Then, based on the obtained information, a relative distance in the optical axis direction of the illumination light between the second exposed portion and the image of the pattern with respect to a second exposed portion (second shot) different from the first exposed portion. The exposure operation accompanying the change operation is controlled.

[0007]

[0008]

According to the first and second aspects of the present invention, the relative distance between the pattern image and the portion to be exposed is changed until the amount of exposure to the portion to be exposed reaches an appropriate amount of exposure for each exposure operation. Exposure, and the subsequent exposure is controlled based on the information related to the change of the relative interval obtained as a result of the exposure. Therefore, it is possible to obtain a substantially stable depth of focus expansion effect for each exposure operation. Can be. More specifically, when the exposure operation is repeatedly performed under substantially the same conditions as in the embodiment described later, the interlocking relationship of the continuous movement of the relative interval changing means (for example, the Z stage) during the preceding exposure operation is analyzed ( Learning)
Then, the interlocking error is obtained, and the parameters are corrected so that the error is corrected in the subsequent exposure operation.

[0009]

[0010]

FIG. 1 shows an outline of a projection exposure apparatus used in the present invention. A condenser lens CL constituting a final stage of an illumination system is provided on a reticle R on which a circuit pattern for semiconductor printing is drawn. Irradiate illumination light with uniform illuminance. The 1/5 or 1/10 reduction projection lens PL projects and exposes the pattern of the reticle R onto the wafer W under telecentric conditions on both sides. A photosensitive layer (photoresist) (not shown) is applied to the wafer W, and is attracted onto a Z stage 20 including a wafer holder. The Z stage 20 is provided on an XY stage 21 so as to be finely movable in the optical axis AX direction (Z direction) of the projection lens PL. The Z stage 20 usually has a correct focus plane (projection lens PL
The XY stage 21 is used to position the projected image of the reticle R and the wafer W in a plane perpendicular to the optical axis AX. Move two-dimensionally. This Z stage 2
0 is, for example, 0.1 μm so that the surface of the wafer W can be positioned with higher accuracy within an effective focal range that decreases as the resolution (numerical aperture NA) of the projection lens PL increases.
The movement is controlled with the following resolution.

It is known that the optical performance of the projection lens PL, such as the focus position and magnification (distortion), varies depending on the atmospheric pressure, the temperature, the exposure power at the time of wafer processing, the irradiation light amount, and the like under the use environment. . Therefore the apparatus of this embodiment inputs information S ₁₁ thereof environmental conditions and exposure conditions, the variation amount monitor 100 to calculate the variation of the optical performance of the projection lens PL, the projection lens in accordance with the fluctuation amount thereof is calculated Pressure regulator 102 for adjusting air pressure in PL
Are provided to correct fluctuations in optical performance.

FIG. 2 shows an oblique incidence type automatic focusing mechanism provided in the projection exposure apparatus shown in FIG. 1, and FIG. 3 is a block diagram showing hardware and software mechanisms of a control system in the apparatus shown in FIG. FIG. First, an automatic focusing (hereinafter, referred to as AF) mechanism will be described with reference to FIG. Illumination light IL that is insensitive to the resist layer on the wafer W and has a wide wavelength width uniformly illuminates the slit plate 1. The light passing through the slit of the slit plate 1 becomes an image forming light beam obliquely incident on the wafer W via the lens system 2, the mirror 3, the diaphragm 4, the projection lens 5, and the mirror 6. As a result, a one-dimensional slit image is formed at the position on the wafer W where the optical axis AX of the projection lens PL passes, that is, at the center of the projection area of the pattern image of the reticle R. Wafer W
The reflected light reflected by the above forms an image on the slit plate 14 for light reception via the mirror 7, the objective lens 8, the relay lens 9, the vibration mirror 10, and the parallel flat glass 12. That is, when the wafer W comes to a predetermined position (focus position) in the optical axis direction,
The three points of the light transmitting slit plate 1, the wafer W, and the light receiving slit plate 14 are set to be conjugate to each other. Further, the system from the light transmitting slit plate 1 to the light receiving slit plate 14 is arranged without fine movement with respect to the projection lens PL. Here, assuming that the wafer W is coincident (focused) with the best image forming plane of the projection lens PL, the slit image on the light receiving slit plate 14 is changed by the action of the vibration mirror 10 to the light receiving slit plate. It will vibrate around 14 slits. When the wafer W deviates from the in-focus position, the center of vibration of the slit image on the slit plate 14 is
It is displaced from the slit of the slit plate 14. The photomultiplier (PMT) 15 is a slit plate 14 for receiving light.
The amount of light passing therethrough is photoelectrically detected, and the photoelectric signal is output to a synchronous detection circuit (hereinafter referred to as PSD) 17. The oscillator (OSC.) 16 outputs an AC drive signal having a frequency f to the actuator (M-DRV) 11 that drives the vibrating mirror 10 and outputs a reference signal having the frequency f to the PSD 17. The PSD 17 is OSC. 16 and the photoelectric signal from the PMT 15
The photoelectric signal is synchronously detected with respect to the reference signal.

This synchronous detection is the same as that of a conventionally well-known photoelectric microscope. When the center of vibration of the slit image vibrating on the slit plate 14 coincides with the center of the slit of the slit plate 14, The photoelectric signal of PMT15 is OSC. The frequency becomes the second frequency (2f) of the frequency f of the 16 oscillation signal, and the detection output FS of the PSD 17 becomes zero. When the PSD 17 shifts from this state, the PSD 17 moves in the direction of the shift, that is, when the position of the wafer W is shifted with respect to the in-focus position.
The detection output F of which polarity differs depending on the displacement
Generate S.

Accordingly, the detection output FS of the PSD 17 is a continuous voltage change that is zero in the focused state, positive when the wafer W approaches the projection lens PL side, and negative when the wafer W moves away from the projection lens PL. Is shown. The detection output FS is usually called an S-curve signal, and there is a range near the zero point where the relationship between the voltage change and the change in the position of the wafer W in the Z direction is almost linear. Used for servo control for

The Z stage 20 is an XY stage 2
Drive circuit (Z-DRV)
It is moved by servo control by 18. In the normal mode, the Z-DRV 18 inputs the detection output FS from the PSD 17 as deviation information, and drives the motor 19 so that the detection output FS matches the target value DS from the main control unit (MCU) 30. . Above, the vibrating mirror 1
0, M-DRV11, slit plate 14, PMT15, O
SC. 16, PSD17, Z-DRV18, motor 1
9 and the Z stage 20 constitute a closed loop control system for automatic focusing. The motor 19 has a Z
An encoder for detecting the amount of movement of the stage 20 or a potentiometer is incorporated, and an information signal ES of the amount of movement is output.

The parallel flat glass (hereinafter, referred to as "harving") 12 in the optical path of the AF system tilts the reflected light beam from the wafer W so as to shift in the vibration direction of the slit image on the slit plate 14. Function as an offset mechanism for shifting the plane to be focused by a predetermined amount in the direction of the optical axis AX. Now, in the embodiment of the present invention, the projection lens PL
As a method of increasing the apparent depth of focus, the Z stage 20 is moved in the optical axis direction at a predetermined speed characteristic during one exposure operation (while the shutter is open), as in the above-mentioned Japanese Patent Application Laid-Open No. 58-17446. To move continuously. However, the difference from the above publication is that the movement of the Z stage 20 in one exposure operation is limited to one direction from bottom to top or from top to bottom. This is to maximize the throughput.

Hereinafter, each functional unit inside the MCU 30 will be described with reference to FIG. The MCU 30 is mainly configured by a central processing unit (CPU) 300, and stores a timer 301 for starting time measurement in response to a shutter opening command TG at the time of exposure, and various parameters for determining operating conditions of the Z stage 20. A data storage unit 302, a digital-analog converter (DAC) 303 for outputting a target value DS to the Z-DRV 18, a PSD1
Analog-digital converter (ADC) for converting the level of the detection output (S-curve signal) FS from 7 into a digital value
304, a position detection circuit 30 which generates information ES of a movement amount of the Z stage 20 by the motor 19 as a digital value
5, and a time monitor unit 306 that monitors the actual time from when the shutter starts to open until when the shutter completely closes. The CPU 300 controls these timers 301,
Information is exchanged among the storage unit 302, the DAC 303, the ADC 304, the position detection circuit 305, and the time monitor 306, and a series of operations are performed.

Although not shown in FIG. 2, a rotary shutter 40 is disposed in the illumination optical system of the projection exposure apparatus, and switches between blocking and passage of illumination light to the reticle R. The rotary shutter 40 is rotated by a motor 41, and its control is performed by a shutter driving unit 42. In response to the shutter opening command TG, the shutter driving unit 42 rotates the motor 41 to a position where the blade of the rotary shutter 40 does not block the illumination light. When the shutter 40 opens and the illumination light reaches the reticle R, the photoelectric sensor 43 also receives a part of the illumination light with a corresponding light amount. The photoelectric signal is input to a light quantity integrating unit (integrator) 44, and an integrated value corresponding to the exposure amount on the wafer W is calculated. A value corresponding to the target exposure amount (appropriate exposure amount) is set in the setting unit 45, and the integrating unit 44 determines whether or not the value matches the target value. A command for closing the shutter 40 is output. As a result, an automatic exposure control method for making the exposure amount given to the wafer W for each shot substantially constant is obtained.

In the above configuration, the XY stage 21 is moved in a step-and-repeat manner to expose the pattern of the reticle R to each of the plurality of shot areas on the wafer W, and each shot area is positioned immediately below the projection optical system PL. Is immediately sent from the host computer. However, when performing alignment for each shot area such as die-by-die alignment or side-by-side alignment after the step pig, a start command TG is sent after the alignment is completed.

FIG. 4 shows a photoelectric signal from the photoelectric sensor 43.
, Ie, the exposure operation and the Z direction of the Z stage 20
The interlocking relationship with the position change characteristics in the (optical axis AX direction) will be described.
Things. FIG. 4A shows light from the photoelectric sensor 43.
Shows an example of the waveform of the electric signal, the vertical axis is the signal level, and the horizontal axis is
Indicates time. FIG. 4A shows the waveform of reticle R or wafer.
C. It uniquely corresponds to the change in illuminance on W
You. In FIG. 4A, at time T₀With shutter release finger
TG occurs, and after a slight delay (about several milliseconds)
Time T₁Then the shutter 40 starts passing the illumination light
You. After a certain period of time (about 10 to 30 milliseconds)
Time T spent_TwoThe shutter 40 is fully opened and the signal
The bell stops when the bell is at the maximum value ILm. During this time,
The arithmetic unit 44 continues the integration operation of the photoelectric signal level, and
Time T reached_ThreeSends a closing command to the shutter drive unit 42
Output. And almost constant lag time (about a few milliseconds
Time T after degree)_FourThe shutter 40 shuts off the illumination light
Start at time T_FiveTo completely shut off the illumination light and stop.
Where time T₁To T_TwoOpening operation time until time T
_FourTo T_FiveIs almost the same as the closing operation time until
Each operation time and lag time (T₁-T₀, T_Four−
T_Three) Depends on the shutter's mechanical properties, electrical responsiveness, etc.
Is almost constant. The actual shutter time in FIG.
The monitor 306 operates at time T in FIG.₁To T_FiveMa
A digital value corresponding to the time at
Things.

FIG. 4B shows an example of the position change characteristic in the Z (optical axis AX) direction of the Z stage 20 (or the surface of the wafer W) ideally linked to the exposure operation of FIG. The vertical axis represents the Z position and the horizontal axis represents time. FIG.
Zero Z position of the (B) shows the best focus position where the AF system is detected as a focus point, it is assumed to move the Z stage 20 in a range of ± Z ₁ around the best focus position. That is, when it is considered that the best imaging plane of the projection optical system PL exists at the position of the zero point in FIG. 4B during one exposure operation, the surface of the wafer W moves from the position −Z _1. continuously to a position + Z ₁ would have moved in the Z direction. In FIG. 4 (B), Z stage 20 during the exposure start is in the position -Z _1, moves at a speed Vs from the time T _a in the shutter fully open position at time T _c +
To stop it reached the Z _1. The time T _b to the surface of the wafer W crosses the best imaging plane (zero point) becomes substantially the intermediate time T _a and T _c, and becomes the midpoint of the effective exposure time (T ₅ -T _1).

As described above, during one exposure operation, the Z stage 20 is moved to ± Z under the timing conditions as shown in FIG.
_When moved within the range of ₁ , the weight of the amount of exposure obtained at each minute Z position in the optical axis AX direction becomes the position-as shown in FIG.
It becomes maximum near Z ₁ and + Z ₁ , and becomes extremely small at the Z position between them. As a result, a focus enlargement effect substantially equal to that of the conventional double exposure method (Japanese Patent Application Laid-Open No. 63-64037) can be obtained. In FIG. 5, the vertical axis represents the Z position, and the horizontal axis represents the weight ratio (or relative weight) of the exposure.

Next, the operation of the present apparatus will be described by taking, as an example, the case where exposure is performed on each shot area (area to be exposed) on the wafer W by the step-and-repeat method. However, it is assumed that one effective exposure time (T ₅ −T ₁ ) is almost accurately obtained by the real-time monitor 306 or calculation before the first shot exposure of the wafer W. In the data storage unit 302, the speed Vs during the exposure operation of the Z stage 20 and the swing width ± Z ₁ of the Z stage 20 are stored.
Is stored as an initial value. The swing width ± Z ₁ can be appropriately designated by the operator.

The CPU 300 of FIG. 3 determines the effective exposure time (T
_Five-T₁), Speed Vs, swing width ± Z ₁Is given
Then, the movement start time T of the Z stage 20_aAnd stop time T_c
And decide. First, the speed Vs is a value unique to the Z stage.
Yes, and is usually set near the maximum speed. So
Here the absolute value of the swing width 2Z₁From time and speed Vs, time T_aOr
T_cTime to T_ssTo 2Z₁/ Vs
Confuse. However, the speed of the Z stage 20 is
When stopped, it will not be linear as set value Vs
In practice, the calculated time T_ssSlightly larger than
Need to be

Next, the CPU 300 determines the effective exposure time (T ₅
−T ₁ ), and _１ ／ of the value obtained by subtracting the time T _ss from each other is obtained. This value (time or from time T _c to T ₅₎ time from the time T ₁ to time T _a corresponds to the T _e, so that the moving start timing of the Z stage 20 (time T _a) has been identified . Incidentally, instead of specifying a time T _a time T ₁ as a reference, the occurrence time T ₀ of the shutter opening command TG
May be used as a reference. In that case, the lag time (T ₁ -T
₀₎ minutes to keep in addition to the time T _e.

When the above calculations are completed, the CPU 300 stores the value of the time T _e or T _e + (T ₁ -T ₀ ) in the data storage unit 302 as one of the initial parameters. At this time, the CPU 300 determines the time (T _e + T _ss / 2) until the middle point time T _b of the effective exposure time (T ₅ −T ₁ ) or the time (T _e +
T _ss / 2 + T ₁ −T ₀ ) is also calculated and the initial parameter 1 is calculated.
One is stored in the storage unit 302.

In this embodiment, in order to move the Z stage 20 as shown in FIG. 4B, the target value DS output from the DAC 303 is changed in accordance with the position ± Z ₁ . Hereinafter, this will be described. FIG. 6 shows an example of a change characteristic of the detection output FS from the PSD 17, the vertical axis represents voltage (level), and the horizontal axis represents the amount of focus shift (the amount of shift between the best focus surface and the wafer surface) ΔZ. . This detection output FS is the zero point (focus point)
, There is a range in which the voltage V and the shift amount ΔZ are linear, and when the surface of the wafer W is displaced from the focal point to the position + Z ₁ , the detection output FS becomes the voltage + V ₁ and the position −Z
It becomes the voltage -V ₁ when it is displaced to the _1.

If the target value DS output from the DAC 303 is fixed at -V1, the servo control of the Z stage 20 is performed so that the surface of the wafer W is located at -Z1 from the best focus plane. FIG. 7 shows the Z stage 20
The differential amplifier 180 outputs the difference between the detection output FS and the target value DS, and the differential amplifier 181 further outputs the difference between the speed feedback signal Sv to the power amplifier 182. Output. The motor 19 rotates at a speed according to the drive voltage of the power amplifier 182, and the rotation speed is detected by the tachogenerator 183. The feedback circuit 184 adds integration processing, gain correction, and the like to the detection signal from the tacho generator 183, and outputs the result as a feedback signal Sv. This circuit is a speed feedback system for stabilizing the rotation speed when the motor 19 is driven. In this embodiment, the feedback circuit 1 responds to a command CD from the CPU 300.
A function is provided for extremely reducing the gain for the feedback signal Sv from 84. For example, by creating a state in which the amount of speed feedback is minimized, the motor 19
It is conceivable to increase the rotation speed of the Z stage 20 and thereby increase the moving speed Vs of the Z stage 20 as much as possible.

In the configuration shown in FIG. 7, when the target value DS is changed to + V ₁ from the state where the target value DS is zero and the detection output FS is stable at the zero point, the motor 19 starts from that moment.
Starts rotating at high speed, and the Z stage 20 moves from the zero point to the position +
To move toward the Z _1. And the Z stage 20 is at the position +
When Z ₁ is reached, DS = FS = + V ₁ stabilizes and the system stabilizes. Therefore, in the present embodiment, the swing width of the Z stage 20 is limited to a linear range on the characteristic of the detection output FS, but the optimum swing width for obtaining the effect of expanding the depth of focus is the width of the focus of the projection optical system PL. It is considered to be about the width (for example, ± 1 μm), which is a range that can sufficiently cope with the width. Note that Z
To increase the swing width of the stage 20, see FIG.
Is changed continuously during the movement feedback of the Z stage 20, and the Z stage 20 (motor 19) always obtains the zero point (or constant voltage point) of the detection output FS. Servo control may be performed.

The exposure of one wafer W by the step-and-repeat method is performed according to the flowcharts shown in FIGS. This flowchart is mainly executed by the CPU 300, and although some parts should be processed by the interrupt method, they are shown in a single routine for easy understanding. First, the host computer designates stepping coordinates so that the position of the XY stage 21 is set to coordinates such that the first shot on the wafer W is exposed. As a result, the XY stage 21 is stepped so that the first shot is located at the position of the projected image from the projection optical system PL (step 20).
0). At this time, the CPU 300
Same value as the level of the detection output FS corresponding to the position -Z ₁ based on the value of the set swing width, i.e. the voltage -V
A digital value such that ₁ is set as the target value DS
(Step 201). As a result, the Z stage 20 moves the wafer surface to -Z with respect to the best focus plane.
_The servo is locked at a position where it is displaced by _one .

When the positioning of the XY stage 21 and the Z stage 20 is completed and a static state is established, a shutter open (exposure start) command TG is generated in step 202, and the drive of the motor 41 for the shutter 40 is started. At the same time, the light quantity integration operation of the integrating section 44 and the time measurement of the timer 301 are started. Then CPU300 reads the counting value of the timer 301 in step 203, the value in step 204 it is determined whether reached driving start time T _a of the Z stage 20. As previously described by Figure 4, the time from the start command TG is generated to start time T _a, since it is set as _{T e + (T 1 -T 0} ) in the storage unit 302, CPU 300 counting value of the timer 301 determines whether it is _{T e + (T 1 -T 0} ) in step 204. Note that during this time the shutter real time monitor 306 shutter 40 starts measuring time from the time T ₁ starts to pass through the illumination light.

Then, the start time T of the Z stage 20
_If it is determined that _a has been reached, the CPU 300 proceeds to step 2
At step 05, a digital value for setting the target value DS to a voltage + V ₁ corresponding to the position of the Z stage 20 + Z ₁ is set to the DAC 303.
Output to Accordingly, the Z-DRV18 shown in FIG.
Starts moving the Z stage 20 from the position −Z ₁ to the position + Z _{1 at} almost the maximum speed. CP immediately afterwards
U300 sets the level of the detection output FS of PSD 17 to AD
Reading is performed via C304 (step 206), and it is determined in step 207 whether or not the level has become substantially zero. The detection of whether or not the detection output FS has become substantially zero is performed by passing the output FS through a zero detection comparator or the like having a narrow window width and responding to the zero detection signal (pulse).
It is more realistic to do this by interrupting the PU 300.

Now, immediately after the Z stage 20 starts moving toward the position + Z ₁ , the detection output FS has not yet reached the zero point, so the determination in step 207 is No, and the CPU 300 advances the sequence to step 209. . If it is determined in step 207 that the detection output FS is zero, the CPU 300 determines in step 208 that the timer 301
_Is read and stored in the data storage unit 302. The counting value T _mc is used to later whether the time T _b in FIG. 4 (B) were consistent with the midpoint of the actual exposure time (T ₅ -T _1). And step 208
After that, the CPU 300 returns the sequence to step 206. Here, the conditional branch from step 207 to step 208 may be limited only once or may not be limited at all.

[0034] Thus detection output FS is in after having traversed zero until the Z stage 20 reaches the position + Z _1, is executed loop of steps 206,207,209, level of the detection output FS is set in step 205 Target value D
When the value becomes substantially equal to S (+ V ₁ ), the CPU 300 reads the time value T _me of the timer 301 at that time and stores it in the storage unit 302 at step 210. Then CPU 300
Waits for the end of the first shot exposure operation in step 211. The read time value T _me is the Z time in FIG.
The movement of the stage 20 is used to check the end time _Tc .

When the exposure of the first shot is completed as described above, the CPU 300 reads the actual exposure time (T ₅ −T ₁ ) from the real time monitor 306 and stores it in the storage unit 302 at step 212 in FIG. Then, in the next step 213, the CPU 300 analyzes an error in the interlocking relationship between the exposure operation by driving the shutter 40 and the movement control of the Z stage 20. First, the CPU 300 starts moving the Z stage 20 from the actual exposure time (T ₅ −T ₁ ) of the first shot, that is, the time T _ss of the difference between the clock value T _me and the clock value (T _e + T ₁ −T ₀ ). 'Subtract. Further CPU300 determines the actual exposure market (T ₅ -T ₁₎ from the time T _ss 'the subtracted time 1/2 of T _e'. If there is no error, the time T _e ′ is equal to the time (T _a −T ₁ ) and the time (T ₅ −T _c ) in FIG. 4B. However, especially with respect to the first shot, the values of the three, namely, time T _e ′, time (T ₅ −T _c ), and time (T _a −T ₁ ) may be significantly different from each other. Is big.

Therefore, in this embodiment, an error ΔTe ′ between the time Te ′ and the time (T5−Tc) is calculated, and it is determined whether or not the error ΔTe ′ is equal to or more than an allowable amount. Here time (T
5-Tc) is read by the real-time monitor 306 as a value obtained by subtracting the lag time (T1-T0) at the start of shutter release from the time value Tme read in step 210 when the Z stage 20 is at the position + Z1. It can be obtained by further subtracting from the actual exposure time (T5-T1). Then, the CPU 300 calculates the error ΔT
If e ′ is equal to or larger than the allowable value, it is determined that there is a correction in step 214, and the parameters in the storage unit 302 are corrected in step 215. Specifically, the time (Te + T1−T0) until the movement start of the Z stage 20 set before the first shot exposure is updated to the time (Te + T1−T0−ΔTe ′) corrected by the error ΔTe ′. I just need.

As another correction method, the first shot
Actual exposure time of the eye (T_Five-T₁) Half of the time
Time value T read in step 208_mcLag time from
(T ₁-T₀) Is equal to or less than
If the error is equal to or greater than the allowable value, the error ΔT_e'
As time (T_e+ T₁-T₀) Can be corrected
Conceivable.

Next, in step 216, the CPU 300 determines whether or not the exposure operation for all shots on the wafer W has been completed. If not, the CPU 300 executes the sequence from step 200 in FIG. 8 again. Step 2 above
A series of sequences from 00 to 216 is repeated for each shot on the wafer W, the second shot from the first shot, the third shot from the second shot, and so on. (Shot exposure operation)
The accuracy of the interlocking relationship between the movement and the movement of the Z stage 20 is improved. That is, the interlocking state learned at the time of the immediately preceding shot exposure is always reflected in the interlocking control at the time of the subsequent shot exposure.

As described above, in the present embodiment, the timing of the shutter operation and the movement of the Z stage is analyzed in order to optimize the interlocking relationship. The optimization of the interlocking relationship can be achieved by analyzing the weight ratio of. Also, the parameter correction is not limited to time, but also a predetermined moving speed V of the Z stage 20.
It is also possible to slightly change s.

Further, in this embodiment, the wafer surface is best.
Time T across the focus plane_mcMonitoring
Therefore, it is necessary to identify the speed unevenness of the Z stage 20 to some extent.
To control the speed characteristics
Various parameter corrections are also possible. Z stage 20
Considering the time of the immerser 301, the lag time (T
₁-T₀) As time TL and time (T_e+ TL)
Start after a short time, time T_mcCrosses the zero at
Interval T_meStop at

Therefore, ideally, (T _e + TL +
_Tme ) / 2 = _Tmc . However, if there is a difference between the speed change (rising characteristic) at the start of the Z stage 20 and the speed change (falling characteristic) at the time of stopping, the symmetry is greatly lost. Therefore, the symmetry of the speed characteristic may be obtained around the time when the Z stage 20 crosses the zero point, and when the symmetry is poor, the speed control of the Z stage 20 may be adjusted. Specifically, a command CD that changes the speed feedback amount by the feedback circuit 184 shown in FIG. 7 from the movement start point to the stop point of the Z stage 20 may be given.

In the above embodiment, the effect of increasing the depth of the wafer W obtained at the first shot is not always stable. For this reason, the pattern resolution in the first shot becomes insufficient, and a failure as a device chip may occur. Therefore, as shown in FIG. 10, of the shot regions are arranged on the wafer W, the first shot is always to specify that the exposure shots S ₁₁ that would missing part at the periphery of the wafer W. Chipped shot S ₁₁ is one that does not originally function as a device chip, exposure to the chipped shot S ₁₁ is a kind of dummy exposure. The arrow connecting the centers of the squares in FIG. 10 indicates the stepping direction by the XY stage 21. If it is desired to expose the resist at the peripheral portion of the wafer, stepping is performed so that all the missing shots at the peripheral portion are also exposed. Therefore, the correction of the parameter may be performed at the time of exposing the missing shot. In this case, the parameter correction is not performed while the normal shot is being exposed.
Steps 2 to 215 are executed to perform parameter correction.

The parameter can be modified by adjusting the opening time of the shutter 40 in addition to the speed and drive timing of the Z stage and the like. In this case, by changing the illumination light intensity on the reticle R when the shutter is fully opened, the actual exposure time (T ₅ −T ₁ ) for obtaining an appropriate exposure amount is changed. Generally, the light source used in this type of device is a mercury discharge lamp, so that the illumination light intensity can be adjusted by changing the input power to the discharge lamp. Actual exposure time (T ₅ −T
_As a case where the parameter correction for changing ₁ ) is effective, there is a case where a highly sensitive resist or the like is used and the full opening time of the shutter becomes extremely short. At this time, Z stage 2
When interlocking relationship between the operating characteristics of the transfer characteristics and the shutter of 0 is shifted slightly, there is the balance of the weight ratio of the exposure amount in the Z position ± Z ₁ is greatly different. Therefore, the input power to the discharge lamp is small (for example, about 10 to 30%).
And the full opening time of the shutter may be extended.

Further, in the above embodiment, the Z stage 20 is moved in the optical axis direction during one exposure operation, that is, the wafer W is moved in the optical axis direction with respect to the best image forming plane of the projection lens PL. However, the wafer W may be fixed and the best imaging plane may be moved in the optical axis direction.
Specifically, the command value S to the pressure regulator 102 shown in FIG.
_It is sufficient to add an offset that changes by a certain amount during one exposure operation. By doing so, the projection lens PL
Since the focal position of itself (the position of the best imaging plane conjugate with the reticle R) changes by a very small amount, the same effect as in the previous embodiment can be obtained without mechanical driving. However,
The time change characteristic of the pressure offset to be applied during one exposure operation has the same tendency as that of FIG.

As a mechanical driving method, a reticle R
Can be moved in the optical axis direction, or a lens element in the projection lens PL can be moved in the optical axis direction. Especially when moving the reticle R, a projection magnification (1/5 relative to the swing width ± Z ₁ when moving the the wafer W, or 1
/ 10) is enlarged to the square (25 times or 100 times) of the reciprocal of / 10), so that there is an advantage that mechanical drive control becomes easy.

In this embodiment, FIGS. 4 (A) and 4 (B)
As described above, the actual exposure time (T_Five-T ₁) Midpoint (time T
_b) Moves Z stage 20 with symmetrical speed characteristics
However, the wafer surface is not necessarily at the midpoint of the actual exposure time.
It is not necessary to set so as to cross the focus plane. So
In the case of, the weight ratio of the exposure amount shown in FIG.
Z₁And -Z₁And will take different sizes. this
The weight of the exposure amount is determined by the resist layer to be exposed.
Thickness, resist layer structure, underlying material, etc.
This corresponds to the change of the perlator as appropriate.

In the shutter characteristics shown in FIG. 4A, the opening operation time (T ₂ −T ₁ ) and the closing operation time (T
₅₋ T ₄ ) is different from the actual exposure time (T ₅ −T ₄ ) even if the respective exposure weights at the Z position + Z ₁ are set equal.
₁ ) The timing at which the middle point and the wafer surface cross the best focus surface slightly deviates. In particular, when the full opening time of the shutter (T ₄ −T ₂ ) is relatively short, the tendency becomes remarkable.

[0048]

According to the first and second aspects of the present invention, the relative distance between the pattern image and the portion to be exposed is set for each exposure operation until the amount of exposure to the portion to be exposed reaches an appropriate amount of exposure. Exposure is performed differently, and the subsequent exposure is controlled based on the information related to the change of the relative interval obtained as a result of the exposure. Obtainable. Therefore, in the case of continuously exposing the same photosensitive substrate, it is possible to obtain an almost stable effect of increasing the depth of focus for each shot. further,
Even if the intensity of the illumination light for exposure slightly fluctuates while exposing one photosensitive substrate and the exposure time per one shot changes, for example, the exposure time described in the present embodiment is taken into consideration. As described above, by appropriately correcting the control parameters such as the exposure operation and the stage operation, the ratio of the weight of the exposure amount obtained at at least two Z positions in the optical axis direction of the projection optical system is kept constant. Exposure becomes possible. Furthermore, as described in this embodiment, if the Z stage is moved only in one direction during one exposure operation, the throughput can be improved as compared with the conventional case.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a projection exposure apparatus which is a premise of the present invention.

FIG. 2 is a block diagram showing an oblique incident light type focus detection system and a Z stage control system.

FIG. 3 is a functional block diagram illustrating a configuration of an exposure control unit and a main control unit.

FIG. 4 is a graph showing shutter characteristics and Z stage movement characteristics.

FIG. 5 is a graph showing an example of a weight ratio of an exposure amount in an optical axis direction.

FIG. 6 is a diagram showing a waveform of a synchronous detection output signal.

FIG. 7 is a diagram showing a configuration of a drive circuit of a Z stage.

FIG. 8 is a flowchart showing an operation example.

FIG. 9 is a flowchart illustrating an operation example.

FIG. 10 is a shot array diagram showing an exposure order on a wafer.

[Description of Signs of Main Parts]

 R Reticle W Wafer PL Projection lens AX Optical axis FS Synchronous detection output 18 Z stage drive unit 20 Z stage 40 Shutter 306 Actual exposure time monitor 302 Data storage unit

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁷ Identification code FI H01L 21/30 514A

Claims (23)

(57) [Claims] 1. An exposure apparatus for exposing an image of a pattern on a mask illuminated by illumination light onto a first exposed portion, an exposure unit exposing the first exposed portion, and the illumination light Changing means for changing the relative interval between the image of the pattern and the first exposed portion in the optical axis direction of the first; and changing the relative interval by the changing means to the first exposed portion. Based on the information acquired by the acquisition unit and the information acquired by the acquisition unit, the acquisition unit acquires information related to the change in the relative interval, which is obtained by exposing the exposure unit to an exposure amount that reaches an appropriate exposure amount. 1
An exposure apparatus, comprising: a control unit that controls an exposure operation of the exposure unit and an operation of the changing unit on a second exposed portion different from the exposed portion. 2. A pattern on the mask is illuminated with illumination light.
An exposure method using an exposure apparatus that exposes an image of the pattern onto a first exposed portion, wherein the relative distance in the optical axis direction of the illumination light between the first exposed portion and the image of the pattern is While changing, until the exposure amount to the first exposed portion reaches the appropriate exposure amount,
Exposing the first exposed portion, acquiring information related to the change of the relative interval obtained by the exposure accompanied by the change of the relative interval, and acquiring the first exposed portion based on the acquired information. And controlling an exposure operation involving a change operation of a relative interval in the optical axis direction of the illumination light between the second exposed portion and the image of the pattern for a second exposed portion different from the second exposed portion. Exposure method. 3. The exposure apparatus according to claim 1, wherein the exposure apparatus performs exposure by a step-and-repeat method. 4. The method according to claim 1, wherein the changing of the relative distance is performed by a stage that changes a relative distance between the mask and the exposed portion. 3. The exposure apparatus according to claim 1, wherein the exposure apparatus moves continuously in only one direction of the optical axis. 5. The exposure apparatus includes a projection optical system that projects an image of the pattern onto the exposed portion, wherein the stage is arranged in the optical axis direction with respect to a best imaging plane of the projection optical system. The best image forming surface is movable from the first position to the first position and the second position separated by a predetermined amount from each other while the pattern image is being exposed on the exposed portion. The exposure apparatus or the exposure method according to claim 4, wherein the exposure apparatus moves to the second position after passing through. 6. The exposure apparatus according to claim 1, wherein the relative interval is changed while the image of the pattern is being exposed on the exposed portion. Exposure method. 7. An exposure control for the second exposed portion,
The exposure apparatus according to claim 1, further comprising controlling the illumination light, or the exposure method according to claim 2. 8. The exposure apparatus or the exposure method according to claim 7, wherein the exposure control includes controlling a light source of the illumination light. 9. The exposure apparatus or method according to claim 8, wherein the exposure control changes an input voltage to the light source. 10. The exposure apparatus or method according to claim 9, wherein the illumination light includes continuous light. 11. The first exposed portion includes a predetermined shot region among a plurality of shot regions on a photosensitive substrate, and the second exposed portion includes a predetermined shot region on the photosensitive substrate. 3. The exposure apparatus according to claim 1, wherein the exposure apparatus includes different shot areas. 12. The exposure apparatus according to claim 1, wherein the second exposed portion is exposed at a next exposure performed after the first exposed portion is exposed.
An exposure method according to claim 11, or an exposure apparatus or an exposure method according to claim 11. 13. The exposure is performed by a shutter that opens / closes an optical path of the illumination light, and the information is obtained by analyzing an interlocking relationship between an operation of the shutter and an operation of changing the relative interval. The exposure apparatus according to claim 1, or the exposure method according to claim 2. 14. The analysis includes measuring an actual exposure time by the shutter and an actual change time of the relative interval by the changing unit, and determining whether the shutter is based on the actual exposure time and the actual change time. A first period from the start of exposure to a time when the changing means starts changing the relative interval, and a second period from when the changing means ends the change of the relative interval to when the shutter ends the exposure. 15. The exposure apparatus according to claim 13, wherein the exposure is performed by determining a period, thereafter calculating a difference between the first period and the second period, and determining whether the difference is equal to or more than a predetermined amount. Or the exposure method. 15. The apparatus according to claim 13, wherein the exposed portion includes a photosensitive substrate, and the change of the relative distance is performed by a substrate stage on which the photosensitive substrate is placed and moved in the optical axis direction. The exposure apparatus or the exposure method as described in the above. 16. The exposure control for the second exposed portion, wherein at least one of a movement timing and a movement speed of the substrate stage is controlled based on the analysis result. Exposure apparatus or exposure method. 17. The exposure apparatus or the exposure method according to claim 16, wherein the exposure control for the second exposed portion corrects a parameter defining an operating condition of the substrate stage. 18. The exposure apparatus according to claim 1, wherein the information is obtained by analyzing a weight ratio of an amount of exposure to the exposed portion due to a change in the relative interval. 3. The exposure method according to 2. 19. The exposure is performed by a shutter that opens / closes an optical path of the illumination light, and the exposure control for the second exposed portion includes adjusting a period during which the shutter opens the optical path. The exposure apparatus or the exposure method according to claim 13, wherein: 20. The exposure control according to claim 19, wherein the exposure control for the second exposed portion controls an illumination intensity of the illumination light on the mask while the shutter is opening the optical path. Exposure apparatus or exposure method. 21. The exposure apparatus includes a projection optical system that projects the pattern onto the exposed portion, and the change in the relative distance includes changing an optical characteristic of the projection optical system. The exposure apparatus according to claim 1 or the exposure method according to claim 2. 22. The method according to claim 22, wherein the change of the optical characteristic is performed by adjusting a pressure in the projection optical system or by moving a lens element in the projection optical system in the optical axis direction. The exposure apparatus or the exposure method according to claim 21. 23. Claim 2 or Claims 3 and 2
3. A method for producing a micro device by the exposure method according to any one of 2.