JPH1097988A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for reproducing unevenness of integrating exposure amount at an arbitrary place with in a shot by providing a function for recording the time of pulse light source's light-emission. SOLUTION: A clock 115 constitutes a time base for taking a time log during one short exposure. The clock 115 is reset by a reset signal 110 from a main control system 104 as soon as a synchronous scan exposure sequence between a wafer stage 14 and a reticule stage 13 is stated. A light emission time recording device 112 records a time data 111 when, an instant, triggered by a trigger signal 16 and an illuminance data 116 of the first exposure amount detector 12. The light emission time recording device 112 temporality store the record data corresponding to the number of light emissions of a light source 1 required for exposure in one shot. After completion of one shot exposure, the light emission time recording device 112 transfers a light emission time log 113 to the main control system 104. With this, distribution of integrated exposure amount in shot is calculated, for exposure amount control with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing semiconductor devices such as ICs and LSIs, liquid crystal devices, imaging devices such as CCDs, and devices such as magnetic heads. Using
The present invention also relates to an exposure apparatus provided with a light emission log function of a pulse light source.

[0002]

2. Description of the Related Art In a conventional static exposure type excimer stepper, an illuminance sensor mounted on a wafer stage is used to obtain only an integrated exposure amount. Had sufficient functions to achieve exposure performance.

As a conventional technique of scanning exposure using a pulse light source, a method of controlling an integrated exposure amount on a photosensitive substrate to a predetermined value includes controlling the number of pulses to be exposed and the energy of each pulse. A method and a method of controlling the interval between individual pulses to be exposed in the scanning exposure apparatus are introduced.

For example, in Japanese Patent Application Laid-Open No. 4-69660, for each pulse from the first pulse, the exposure amount of the next one pulse is calculated from the remaining exposure amount obtained by subtracting the already exposed exposure amount from the total exposure amount. A method for controlling the exposure amount varying means has been proposed.

Similarly, in Japanese Patent Application Laid-Open No. 5-62876, the average energy per pulse of the residual light amount and the average one pulse exposure amount up to a plurality of times before are compared for each pulse. A method of changing a control parameter to match the average energy per pulse has been proposed.

On the other hand, in Japanese Patent Application No. 7-74092, an exposure amount of each pulsed light is monitored while keeping a scanning speed constant in a slit scanning type exposure apparatus, and the next exposure is performed according to the measured intensity of the exposure amount. A method of temporally changing the light emission timing of the pulse light is proposed. At the same time, by making the intensity distribution of the slit light in the scanning direction have a gradual change in the boundary region, consideration is given to prevent the above-described deterministic error of the integrated exposure amount from occurring.

[0007]

However, in a scanning exposure apparatus as described in the prior art, a local irradiation area moves with time during one-shot exposure. The integrated exposure amount distribution cannot be said to accurately measure the integrated exposure amount of the entire shot by measuring only one representative point in the shot as in a static exposure apparatus. Accordingly, there has been a demand for a means for measuring the integrated exposure unevenness suitable for scanning exposure at an arbitrary position in a shot and verifying the integrated exposure unevenness and the integrated exposure amount in the shot in an exposure apparatus.

An object of the present invention is to provide means for reproducing the unevenness of the integrated exposure amount at an arbitrary position in a shot. In particular, in a scanning exposure apparatus that exposes a wafer by scanning an exposure beam slit by pulsed light emission, the function of reproducing the distribution state of the integrated exposure amount on shots actually exposed from exposure history data without developing the wafer The purpose is to provide.

[0009]

In order to achieve the above object, the present invention provides a pulse light source for irradiating a specific area on an original, a substrate mounted on a plate, and a light source perpendicular to the irradiation light from the pulse light source. An exposure apparatus having a substrate stage capable of moving on a flat surface is provided with a function of recording a light emitting time of a pulse light source. Preferably, further,
The function of recording or calculating the position of the substrate stage at the time of emission of the pulse light source, the function of measuring and recording the illuminance data measured by the illuminance sensor in the emission corresponding to the emission time of the pulse light source, and Acquisition function that faithfully measures the integrated exposure unevenness in the scanning exposure shot by associating the position of the shot on the stage with the irradiation position and intensity of the irradiation light from the light source via the axis, and minimizes the integrated exposure unevenness Have the function to suppress.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 shows a schematic configuration of a scanning exposure apparatus according to an embodiment of the present invention. In FIG. 1, a light beam from a pulse laser light source 1 that emits pulse light such as an excimer laser is shaped into a desired shape by a beam shaping optical system 2, and is incident on an optical integrator 3 configured with a fly-eye lens or the like. Oriented to the plane.

The fly-eye lens is composed of a group of a plurality of minute lenses.
A secondary light source is formed. Reference numeral 4 denotes a condenser lens.
The movable slit 6 is Koehler-illuminated with the light beam from the next light source.

The movable slit 6 and the reticle 9 are arranged in a conjugate relationship with the imaging lens 7 and the mirror 8, and the shape and size of the illumination area on the reticle 9 are defined by the shape of the opening of the movable slit 6. Reference numeral 18 denotes a voice coil motor, which can control the movement of the movable slit 6 in the optical axis direction. This slit 6 is actually the reticle 9
The exposure intensity profile formed by the slit 6 has a trapezoidal shape as shown in FIG. As the slit moves along the optical axis, the exposure intensity profile changes as indicated by 51 and 52 in FIG. In FIG. 1, reference numeral 10 denotes a projection optical system;
The circuit pattern drawn on the reticle 9 is reduced and projected on the semiconductor substrate 11. Reticle 9 is reticle stage 13
And the wafer stage 1 via the projection optical system 10.
The semiconductor substrate 11 fixed on the substrate 4 is aligned at a desired position and scanned and exposed.

A second exposure detector 15 is disposed on the wafer stage 14, and the second exposure detector 15 can monitor the exposure of the laser light source 1 via the optical system. . Reference numeral 101 denotes a stage drive control system for controlling the reticle stage 13 and the wafer stage 14. Reference numeral 12 denotes a first exposure amount detector which monitors a partial light beam of the pulse light split by the half mirror 5.

An exposure calculator 102 converts an electric signal photoelectrically converted by the first exposure detector 12 and the second exposure detector 15 into a digital value, and converts the electric signal into a digital value.
Sent to. The first exposure amount detector 12 is fixed to the exposure apparatus main body, and can measure the intensity even during the exposure. Therefore, the first exposure amount detector 12 is used for estimating the integrated value of the exposure light exposed on the semiconductor substrate 11. The second exposure amount detector 15 is connected to the wafer stage 1
4 is used to measure the intensity profile of the exposure light emitted from the slit since the intensity of the slit light can be measured at an arbitrary position. The second exposure amount detector 15 cannot measure the irradiation light intensity from the light source 1 during wafer exposure. The laser control system 103 generates a trigger signal 16 and a charging voltage signal 17 according to a desired exposure amount, and controls the pulse energy and the light emission interval of the laser. When the trigger signal 16 and the charging voltage signal 17 are generated, the illuminance monitor signal 108 from the exposure calculator and the information on the number of times of light emission of the laser light source from the main control system are used as parameters.

The exposure value and the allowable value of the exposure value unevenness are input by an input device 105 which is a man-machine interface or a media interface. The result obtained from the first exposure amount detector 12 and the second exposure amount detector 15 and the estimated value of the integrated exposure amount can be displayed on the display unit 106. The main control system 104 uses the data supplied from the input device 105, the parameters unique to the exposure device, and the data measured by the measurement mechanisms such as the first exposure amount detector 12 and the second exposure amount detector 15 to perform scanning exposure. The parameter group is calculated and transmitted to the laser control system 103 and the stage drive control system 101. A clock 115 serves as a time base for taking a time log during one-shot exposure. The clock 115 resets the reset signal 1 from the main control system 104 at the moment when the synchronous scanning exposure sequence of the wafer stage 14 and the reticle stage 13 starts.
Reset by 10. Reference numeral 112 denotes a light-emission time recorder, which stores time data 111 at the moment triggered by the trigger signal 16 and illuminance data 11 of the first exposure detector 12.
Record 6. The light emission time recorder 112 can temporarily hold recording data corresponding to the number of light emissions of the light source 1 required for exposure within one shot. When the exposure of one shot is completed, the light emission time recorder 112 outputs the light emission time log 113.
To the main control system 104.

FIG. 2 shows the contents of the one-shot emission time log transferred from the emission time recorder 112 to the main control system 104 in FIG. In each row, the light emission time and the light emission intensity corresponding to the light emission of the light source are recorded. An ordinary excimer laser light source has a variation in light emission intensity of about 5% due to the non-uniformity of the gas concentration in the laser tube even when discharging is performed at a constant charging voltage. Therefore, whether or not the light emission intensity of the light source falls within an allowable range with respect to the command charging voltage can be verified by referring to the above record.

Further, charging of the voltage applied to the electrode of the laser light source may rarely fail (discharge on the way). In such a case, the light source does not emit light even when the trigger signal 16 is supplied. By referring to the above record, it is possible to detect the case where the light source does not emit light even though the trigger signal is received (misfire).

FIG. 3 is an acquisition data table of the wafer stage. The position of the wafer stage 14 is such that data of the current position for each servo clock is read into the stage drive control system 101. That is, FIG.
As shown in FIG. 7, the coordinates of the wafer stage position for each time period divided by the servo clock can be obtained for each shot. Normally, the sampling interval of the acquisition data of the wafer stage 14 and the light emission timing of the light source 1 are not synchronized, so that the time at which the laser light emission occurs and the position of the wafer stage at that time will be linked with reference to the time axis. In this case, it is necessary to complement the position of the wafer stage at the light emission timing of the light source 1 with the above acquisition data.

FIG. 4 shows a light source 1 supplemented from the wafer stage acquisition data obtained for each servo clock.
FIG. 4 is a diagram for finding a position of a wafer stage during a light emission time tn. Since the wafer stage moves at a constant speed during the scanning exposure, linear function complementation is sufficient.

According to the above complementing method, after the exposure of one shot is completed, the light emission time log data 113 and the wafer stage acquisition data are transferred from the exposure time recorder 112 and the stage drive control system 101 to the main control system 104. It is possible to link the position of the wafer stage when the laser emission occurs with reference to the time axis. That is, during the actual exposure, it is possible to express where the intensity profile of the exposure light for each emission of the light source 1 is irradiated on the wafer stage (FIG. 6).

FIG. 5 is a profile of the exposure light intensity on the image plane of the wafer stage. In order to smoothly connect the temporally discontinuous exposure light irradiation of the pulse laser light source,
The shape of the base of the profile is aggressively smoothed.
The width of this foot can be changed by moving the movable slit 6 in FIG. 1 from the reticle conjugate plane in the defocus direction on the exposure optical axis. As the defocus amount increases, the width r of the gray zone increases, and the integrated exposure amount is in a direction in which the unevenness is flattened. However, since the width of the projection optical system through which the exposure light passes is represented by r + w, if the diameter of the projection lens is fixed and if r is to be increased, the slit width w must be reduced.

FIG. 6 is a conceptual diagram for estimating the integrated exposure amount when scanning exposure is performed with exposure light having such a known profile. In FIG. 6, an arbitrary position Xn
Is equivalent to the sum of the heights of the trapezoidal profiles crossing at the position of Xn as shown by the dotted line in the figure. The light emission control of the light source is performed as an integrated exposure amount control means for achieving a uniform integrated exposure amount, such as a voltage control method for adjusting the charging voltage 17 according to the detection amount of the first exposure amount detector 12, or a trigger signal. There is a light emission timing control method that adjusts the timing of the sixteenth timing. If scanning exposure is performed at a constant speed, in the former case, the positions of the wafer stages in FIG. 4 will be at equal intervals, and as a result, the intervals between adjacent trapezoidal profiles in FIG. 6 will be the same, and only the maximum intensity of the profile will change. . In the latter case, both the spacing and the maximum intensity of the profile change.

FIG. 7 is a diagram in which the integrated exposure amount at an arbitrary location is reproduced based on the conceptual diagram of FIG. This reproduction is performed in the main control system 104 of FIG. That is, the integrated amount of the height (illuminance) of the trapezoid in FIG. 6 is obtained with respect to the position on the x-axis. According to FIG. 7, the shape of the integrated exposure amount at each location during the scanning exposure can be grasped by performing the integration process on the calculation from the information obtained from the emission timing and intensity log of the laser light source.

As described above, the functions of recording the illuminance and the time for each emission of the pulse laser and the function of recording or calculating the position of the stage at the time of the laser emission are provided, and these functions are obtained. From the log data, the illuminance data and the position data of the wafer stage are linked on the basis of the time axis, and the distribution of the integrated exposure amount placed in the shot is calculated. Further, parameters (scanning speed, emission intensity command value, slit profile, etc.) for controlling the total integrated exposure amount and the integrated exposure amount unevenness are adjusted based on the integrated exposure amount obtained as described above. As a result, more accurate exposure amount control can be performed.

On the other hand, by analyzing the illuminance data at the light emission time in the main control system, it is possible to confirm the presence or absence of misfire (unexpected) during one-shot exposure. The main control system can detect the presence or absence of the misfire, detect the exposure failure of the exposure shot or the chip, and configure process job data.

Embodiment 2 FIG. 8 is a data flow for estimating an integrated exposure dose distribution on a wafer without scanning a wafer stage according to a second embodiment of the present invention. The hardware configuration is the same as in the first embodiment. That is, in FIG. 8, the light emission time log 801 similar to that described in FIG. 2 is temporarily stored in the exposure calculator 102, and is transferred to the main control system 104 after light emission for one shot is completed. The wafer stage scanning speed 802 is a scanning speed v used when exposing a wafer by actually scanning the wafer stage, and it is not necessary to drive the wafer stage when calculating the integrated exposure amount. The calculation 804 of the integrated exposure amount can be obtained by calculating the position Xm of the wafer stage at the light emission time tm from the scanning speed and the scanning start point X0 as described with reference to FIG.
X0 + v * tm). From this relationship, as in the first embodiment, FIG.
It is possible to follow the procedure for obtaining the integrated exposure amount as shown in (1), and obtain the integrated exposure amount 803 in the exposure shot. In this embodiment, the sensor used for detecting the illuminance of the exposure light from the laser light source 1 is a first exposure detector 1 which is a sensor attached to a fixed point in the apparatus as in the first embodiment.
The second exposure amount detector 15 may be a movable sensor mounted on the stage. The second exposure amount disposed at a position for measuring the exposure light intensity after passing through optical elements such as the imaging lens 7, the mirror 8, the reticle 9, and the projection lens 10, as compared with the case where the first exposure amount detector performs the operation. It is preferable that the illuminance is detected by the detector 15 in terms of measurement accuracy.

It is estimated that the allowable value of the integrated exposure unevenness for realizing a line width processing accuracy of 0.25 μm is around 1%. In the case where the reproduced amount of the integrated exposure unevenness in FIG. 7 exceeds the allowable value, the integrated exposure amount unevenness can be reduced by increasing the number of light receiving pulses at the exposure position of interest. For this purpose, a method of increasing the number of received light pulses by simply lowering the maximum intensity im (FIG. 5) and the scanning speed of the wafer stage, and a method of increasing the width r of the slit foot (FIG. 5) (the diameter of the lens is limited) As a result, if the foot is widened, the slit width W becomes narrower). In both methods, the irradiation energy per pulse used for exposure of the light source is limited, which causes a decrease in throughput which is a measure of the productivity of the exposure apparatus. Will be done.

[0028]

As described above, according to the present invention, it is possible to calculate the accumulated exposure unevenness by providing the function of recording the time for each pulse emission of the pulse light source. In particular, in a scanning exposure apparatus that exposes a substrate by scanning an exposure beam slit by pulsed light emission, a function of recording illuminance and time for each pulsed light emission of a pulsed laser, and a position of a stage at the time of laser emission. Or have a function to calculate. Then, from the log data obtained from these two functions, the illuminance data and the position data of the wafer stage are linked based on the time axis, and the distribution of the integrated exposure amount in the shot is calculated.
Further, parameters (scanning speed, light emission intensity command value, slit profile, etc.) for controlling the total integrated exposure amount and the unevenness of the integrated exposure amount are adjusted based on the obtained integrated exposure amount. This makes it possible to reproduce the distribution state of the integrated exposure amount at various points in the actually exposed shot from the exposure history data without developing the substrate.

[Brief description of the drawings]

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

FIG. 2 is a table showing an example of the content of a light emission time log in the apparatus of FIG.

FIG. 3 is an acquisition data table of a wafer stage in the apparatus of FIG. 1;

FIG. 4 shows a position X of a wafer stage in the apparatus shown in FIG.
6 is a graph showing a relationship between m and time tm.

FIG. 5 is a view showing a profile of exposure light intensity on a wafer stage imaging surface.

6 is a conceptual diagram for estimating an integrated exposure amount in the apparatus of FIG.

FIG. 7 is a diagram reproducing an integrated exposure amount at an arbitrary position based on the conceptual diagram of FIG. 6;

FIG. 8 is a data flow diagram according to a second embodiment of the present invention.

[Explanation of symbols]

1: pulse laser light source, 2: beam shaping optical system, 3:
Optical integrator, 4: Condenser lens,
5 :, 6: movable slit, 7: imaging lens 7, 8: mirror, 9: reticle, 10: projection optical system, 11: semiconductor substrate, 12: first exposure amount detector, 13: reticle stage, 14: Wafer stage, 15: second exposure amount detector,
16: trigger signal, 17: charging voltage signal, 18: voice coil motor, 101: stage drive control system, 102:
Exposure calculator 103: laser control system, 104: main control system, 105: input device, 106: display unit, 108: illuminance monitor signal, 109 :, 110: reset signal, 11
1: time data, 112: emission time recorder, 113: emission time log, 115: clock.

Claims (10)

[Claims] An exposure apparatus comprising: a pulse light source for irradiating a specific area on an original; and a substrate stage on which a substrate is mounted and which can move on a plane perpendicular to irradiation light from the pulse light source. An exposure apparatus comprising means for recording a time at which light is emitted. 2. The exposure apparatus according to claim 1, further comprising means for recording or calculating a position of the substrate stage at a time when the pulse light source emits light.
Exposure apparatus according to the above. 3. An exposure apparatus comprising: a pulse light source for irradiating a specific area on an original; and a substrate stage mounted with a substrate and movable on a plane perpendicular to irradiation light from the pulse light source. At least one illuminance sensor for measuring the illuminance of the light source, and a means for recording illuminance data measured by the illuminance sensor in the light emission, in correspondence with the emission time of the pulse light source. Exposure equipment. 4. The exposure apparatus according to claim 3, wherein the illuminance sensor is a fixed point on the exposure apparatus, and is mounted at a position where illuminance can be measured even during exposure of the substrate. 5. The exposure apparatus according to claim 4, wherein the illuminance sensor is a sensor array in which photoelectric elements in at least one dimension are arranged. 6. A position on the substrate stage, an irradiation amount of exposure light by the pulse light source, and a position of the substrate stage at a time when the pulse light source emits light, a position of the substrate stage at a time when the pulse light source emits light, and illuminance data in the light emission. The exposure apparatus according to any one of claims 3 to 5, further comprising means for associating 7. A means for calculating and reproducing an integrated exposure amount distribution in a shot on the substrate from a result of associating exposure light irradiation amount data when the light source emits light with a position on the substrate stage. 7. The method according to claim 6, wherein
Exposure equipment. 8. By synchronously scanning the original and the substrate under an irradiation area defined by an exposure slit,
A scanning exposure apparatus for projecting a pattern on an original onto a substrate, comprising: means for adjusting the width and profile of the exposure slit using the reproduction result of claim 7. 9. A scanning exposure apparatus for projecting a pattern on an original onto a substrate by synchronously scanning an original and a substrate under a specific irradiation area by the pulsed light source, using the reproduction result of claim 7 A scanning exposure apparatus, comprising: means for adjusting the speed of the synchronous scanning by means of the scanning exposure apparatus. 10. The apparatus according to claim 3, further comprising: means for referring to the illuminance data over light emission within one shot, detecting misfire of laser light emission, and detecting exposure failure of the shot. Scanning exposure equipment.