JPH07111375B2 - Illuminance distribution measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for measuring an illuminance distribution of energy applied to a predetermined area, and more particularly to an apparatus capable of measuring an illuminance distribution in pulsed energy irradiation. Is.

[Prior Art] For example, when performing exposure using an exposure apparatus, it is necessary that the illuminance on the exposed surface or the mask surface is uniform. Therefore, it is extremely important to accurately measure the uniformity of the illuminance.

Conventionally, as a light source for an exposure apparatus or the like, a continuous light emission type light source having a stable intensity such as a mercury lamp has been generally used.
Therefore, as the device used for measuring the uniformity of illuminance, an energy amount detector having only a light receiving area of a part of the measured region has been used. That is, it was possible to measure the illuminance uniformity in the area by moving the detection position and sequentially performing the measurement.

[Problems to be Solved by the Invention] In the conventional device as described above, since the energy amount detector having a part of the light receiving area of the measurement region is measured by moving in the measurement region, It was performed under the precondition that the output intensity of the energy source is constant from the start to the end of the illuminance uniformity measurement.

Therefore, when the energy generation source is a pulse emission type energy generation source having a variation in the amount of energy for each pulse, it is difficult to measure the illuminance uniformity using the above-mentioned conventional device. .

FIG. 5 (a) is a diagram showing the illuminance distribution when laser light is emitted one pulse at each of the measurement points P1, P2, ..., Pn in the measured region. In this case, the illuminance at each measurement point greatly varies as shown in the figure. Therefore, the variation between the pulses at each measurement point may be larger than the variation between the measurement points, which makes it difficult to measure the illuminance uniformity.

As described above, the conventional apparatus has a problem that it is difficult to measure the illuminance uniformity in pulsed energy irradiation.

The present invention has been made to solve the above-mentioned problems, and even when the energy generation source is a pulse generation type energy generation source having a variation in energy amount for each pulse, measurement of illuminance uniformity is performed. It is an object of the present invention to provide an illuminance distribution measuring device capable of performing.

[Means for Solving Problems] An illuminance distribution measuring apparatus according to the present invention is a detecting means for detecting the energy intensity of an arbitrary local portion within a predetermined area; First computing means for detecting a plurality of pulse energies from the energy source in a defined local portion and calculating information according to variations in the intensity of the pulse energies between the respective pulses; The above-mentioned problems by providing a second calculation means for calculating the number of oscillations of pulse energy required when measuring the illuminance distribution based on the information and a predetermined illuminance uniformity standard value. It has been resolved.

[Operation] According to the principle of propagation of fluctuations, if the variation of the energy amount of one pulse is (δp / p), the variation of the average energy by n pulses is Becomes Therefore, take an appropriate value for the value of n, and
By integrating or averaging the pulse energies, it is possible to reduce the measurement error due to variations for each pulse.

FIG. 5 (b) is a diagram showing a case where, for example, an average value is taken every 5 pulses at each measurement point. In this case, the variation of the average value for every 5 pulses at each measurement point is compared with the case of FIG. 5 (a). Becomes

Therefore, in the present invention, a plurality of pulse energies from the energy source are detected at a predetermined local portion within a predetermined area by using the detecting means; and between the pulses of the pulse energy by the first calculating means. Calculating information according to the variation in intensity;
Based on the calculated information and a predetermined illuminance uniformity standard value, the number n of oscillations of pulse energy required when measuring the illuminance distribution is calculated; and the energy of n pulses is integrated or averaged. And the measured value And the measurement error becomes small.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, a laser beam output from a laser light source 10 such as an excimer having an oscillation spectrum in the ultraviolet region enters a cylindrical lens 12, and when the laser beam has a different aspect ratio such as a rectangle or an ellipse, The aspect ratio of the laser beam is changed in the cylindrical lens 12, and the laser beam is output as a laser beam having the same aspect ratio.

Next, the laser beam has its optical path bent in the vertical direction by the bending mirror 14, and then has a predetermined beam diameter in the beam expander 16.

Next, the laser beam reaches the reticle 24 via the fly-eye integrator 18, the bending mirror 20, and the main condenser lens 22. At this time, the fly-eye integrator 18 and the main condenser 22 make the laser beam uniform light and illuminate the reticle 24, and the illuminance on the pattern surface of the reticle 24 becomes almost uniform.

Next, the laser light transmitted through the reticle 24 is projected onto the projection lens 26.
A pattern image of the reticle 24 is formed on the wafer 28 via the. The wafer 28 is vacuum-chucked to a wafer holder 30 provided on an XY stage 32 capable of two-dimensional movement.

An illuminance detector 34 is provided on the XY stage 32. When performing illuminance measurement, the XY stage 32 is appropriately moved to detect laser light. The sensor surface of the illuminance detector 34 is set to be substantially the same height as the surface of the wafer 28 (that is, the image plane of the projection lens 26) so that the illuminance uniformity can be measured on the image plane. It has become. The illuminance detector 34 has a pinhole mounted on its light-receiving surface, and is installed so that the pinhole surface is substantially at the same height as the wafer surface, that is, the conjugate surface of the projection lens 26 with the reticle 24.

A control system 36 controls measurement based on a signal corresponding to the illuminance detected by the illuminance detector 34. Also 38
Is an interferometer for measuring the position of the XY stage. Although two interferometers 38 are provided in the X direction and the Y direction, only one of them is shown in this case.

Next, FIG. 2 is an explanatory diagram showing an exposure area and measurement points in the exposure area. In the figure, A is an exposure area, and P1, P2, ..., P49 are measurement points.

Next, FIG. 3 is a block diagram of the control system 36. In the figure, the detection signal from the illuminance detector 34 is the first calculation means.
The data is input to 40, and the first calculating means 40 calculates information according to the variation in the detection signal value.

Next, the second calculation means 42 sets the number of pulses required for measurement from the information according to the variation calculated by the first calculation means 40 and the preset illuminance uniformity standard value. .

Next, the operation when the illuminance uniformity measurement is performed using the apparatus configured as described above will be described.

When measuring the illuminance uniformity, the reticle is removed or a transparent reticle without a pattern (blank reticle) is attached. Then, the XY stage 32 is sequentially moved in the XY directions, and the illuminance detector 34 is moved to the exposure area A.
To move to the positions of P1, P2, ..., P49.
Then, measurement is performed at the focus position of the projection lens 26 by an autofocus mechanism (not shown).

In the above case, the illuminance detector 34 moves on the image plane of the projection lens 26, but the reticle 24
The reticle surface (object surface) may be moved in a state where is removed.

Next, FIG. 4 is a flow chart showing an example of an actual illuminance uniformity measuring sequence. Hereinafter, an example of the sequence will be described with reference to the figure.

First, as the 1st step (step 100), laser light emission of a plurality of pulses is performed at one location in the illuminance uniformity measurement region, for example, at the center position, photoelectric conversion is performed by the illuminance detector 34, and the photoelectric signal of each pulse is converted into Output to the calculating means 40.
The first calculation means 40 calculates the variation δp / p of the energy amount for each pulse from the photoelectric signal of each pulse, and outputs a signal based on the result to the second calculation means 42. In this case, the greater the number of pulses, the more accurately the variation Δp / p can be obtained, but about 100 pulses is a practical value.

Since the variation distribution of the energy of the laser emission is usually a Gaussian distribution type, if the standard deviation is σ, it is sufficient to consider 3σ as δp / p.

Next, in a second step (step 101), the second calculation means 42 sets a signal regarding the variation from the first calculation means and a preset allowable limit of the variation, that is, a value smaller than the illuminance uniformity standard value. And the integrated pulse number n for illuminance uniformity measurement is determined so that the variation satisfies the allowable limit.

According to the principle of fluctuation propagation, the variation in the average energy of n pulses is as described above. Therefore, if the standard value of illuminance uniformity is set to ± A ₀ , for example, It is necessary to determine n so that Actually, A ₀ is about 2%, It is practical to determine n to be a degree.

Next, as the 3rd step, the main measurement of the illuminance distribution measurement is performed. That is, first, the counter i is set to 1 (step 102), the XY stage 32 is moved so that the illuminance detector 34 comes to the position of the measurement point P1 (step 103), and n-pulse illuminance measurement is performed (step). 104).

Next, the counter i is incremented by 1 (step 106), the illuminance measurement is sequentially performed at the measurement point Pi, the illuminance measurement is performed at the end measurement point P49 (step 105), and the illuminance uniformity measurement is ended.

Next, as the 4th step (step 107), a value ± A indicating the uniformity of illuminance is calculated. As a concrete example of the definition of A, the maximum illuminance is I _MAX and the minimum illuminance is I _MIN among the measurement points.
In each case, the value given by the following formula is practical.

When the energy source is laser light, the coherence of the laser light may cause uneven illuminance called speckle on the exposure surface. In that case, speckle low-pass measures and the like using a fiber or an optical system in which a laser beam is manipulated to enter the fly-eye lens are considered. Further, an energy control device and the like for obtaining an appropriate exposure amount while considering the variation of the light emission energy of one pulse has been studied. Therefore, when the illuminance distribution is measured using the apparatus of the present invention, the number of pulses to be measured at one measurement point is determined by using the above speckle countermeasures and exposure amount control together. It will be more practical and effective.

Although pulsed laser light was considered in the above embodiments,
Even in the case of a mercury lamp, even when the input power is doubled only for a short time (about 1 second) only at the time of exposure, since the light amount also varies, the same measurement method can be used. Further, a plasma X-ray source may be used as an energy source and may be applied to X-ray illuminance distribution measurement.

[Effects of the Invention] As described above, the present invention includes a detection unit that detects the energy intensity of an arbitrary local portion within a predetermined area; and a detection unit that uses the detection unit to detect a predetermined local portion within the predetermined area. First computing means for detecting a plurality of pulse energies from the energy source and calculating information according to variations in intensity of each pulse of the pulse energy; information according to the computed variations and predetermined illuminance uniformity And a second calculation means for calculating the number of oscillations of pulse energy required when measuring the illuminance distribution based on the characteristic standard value, information corresponding to the variation in energy between pulses can be obtained. The number of pulses can be calculated, and the number of pulses to be used as the measurement unit is calculated based on the information according to the calculated variation and the preset illuminance uniformity standard value. Since it is possible to detect and average the pulses, it is possible to measure the illuminance uniformity even when a pulse emission type energy generation source having a variation in energy amount for each pulse is irradiated. effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an exposure region and measurement points therein, and FIG. 3 is a block diagram showing the configuration of a control unit of the embodiment shown in FIG. FIG. 5 is a block diagram, FIG. 4 is a flow chart showing an example of the sequence of illuminance uniformity measurement, and FIG. 5 (a) is a diagram showing the illuminance distribution when one pulse of laser light is emitted per measurement point, and FIG. b) is a diagram showing a distribution of average values of illuminance for every 5 pulses. [Explanation of symbols for main parts] 10 ... Laser light source, 12 ... Cylindrical lens, 14, 2
0 …… Bending mirror, 16 …… Beam expander, 18
...... Fly eye integrator, 22 …… Main condenser, 24 …… Reticle, 26 …… Projection lens, 28 …… Wafer, 30 …… Wafer holder, 32 …… XY stage, 34 …… Illuminance detector, 36 …… Control Part, 38 ... Interferometer, 40 ... First computing means, 42 ... Second computing means, A ... Exposure area, P1, P2,
~, P49 …… Measurement point.

Claims (1)

[Claims] 1. An apparatus for measuring an illuminance distribution within a predetermined area when a pulse energy is applied to an object having a predetermined area substantially uniformly from a pulse-generating energy source, wherein an arbitrary local portion within the predetermined area is provided. Detecting a plurality of pulse energies from the energy source at a predetermined local portion within the predetermined area by using the detecting means, and intensities between the pulses of the pulse energy. A first calculation means for calculating information according to the variation of; and information according to the calculated variation,
A second calculation means for calculating the number of oscillations of pulse energy required when measuring the illuminance distribution based on a predetermined illuminance uniformity standard value; measuring the number of oscillations of the calculated pulse energy An illuminance distribution measuring device characterized by performing measurement as a unit.