JPH0572145A - Foreign matter inspecting device - Google Patents

Abstract

PURPOSE:To carry out measurement with stable detection sensitivity by correcting light intensity in a shorter time than ever. CONSTITUTION:A standard sample 13 for generating the standard scattered light, light detector 10 for detecting the standard light, and a measured sample 7 are arranged on a stage 8 so as to be set on a same plane. A memory part 12 for memorizing the light intensity value obtained from the standard sample 13 and the light detector 10, and a control part 11 which compares the intensity of the light used for measurement and the intensity of the scattered light supplied from the measured sample with each standard value and corrects the sensitivity of a photoelectric conversion element 2 which receives the scattered light supplied from the measured sample 13 are provided, and the light detecting sensitivity is monitored and corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter inspection apparatus for inspecting the presence or absence of foreign matter adhering to a semiconductor wafer, a reticle for lithography and a mask in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a conventional foreign matter inspection apparatus. As shown in FIG. 2, this foreign matter inspection apparatus captures the light emitting section 3 that scans the surface of the sample 7 to be measured placed on the stage 8 with light, and the scattered light reflected from the surface to convert the light into an electric current. The photoelectric conversion element 2 for conversion, the A / D converter 5 for converting the output current of the photoelectric conversion element 2 into a digital value as a voltage, and the output of the A / D converter 5 determine the size of foreign matter adhered. However, the size conversion circuit 1 that outputs a signal corresponding to the size and the display unit 6 that displays the size of the foreign matter by the output of the size conversion circuit 1 are included.

FIG. 3 is a view showing a reference sample to which standard particles are attached, and FIG. 4 is a view showing a waveform of a photovoltaic voltage due to scattered light captured. In the above-described foreign matter inspection apparatus, the inspection sensitivity is calibrated in preparation for the actual inspection. For this, the reference sample shown in FIG. 3 is irradiated with laser light, and scattered light reflected from the standard particles 9 is generated as the waveform shown in FIG. Then, as shown in FIG. 4, the output value was adjusted so that the wave light value of the photovoltaic voltage to be obtained by the standard particles 9 would be matched with the reference value by the sensitivity adjusting circuit 4 shown in FIG.

After the adjustment as described above, the wafer or photomask as the inspection object is scanned with light, the scattered light of the inspection object is captured by the photoelectric conversion element, converted into photocurrent, and converted into a photovoltaic voltage. It is digitized by the A / D converter 5. And the size conversion circuit 1 according to the number of digitized signals
Judges the size of the foreign matter adhering to the object to be seen and displays the foreign matter on the display unit 6.

[0005]

However, in the conventional foreign matter inspection apparatus, in order to prepare the reference sample to which the standard particles are attached in advance, confirm the detection level, and adjust the voltage applied to the photoelectric conversion element, For example, there was a problem of wasting more than 4 hours. Also, the detection sensitivity often changes due to fluctuations in the output of scanning light from a laser or the like,
In order to maintain constant performance for a long period of time, it was necessary to frequently perform regular checks and adjustments. This results in a large loss of time. Further, since it is assumed that the detection sensitivity does not change from one inspection to the next inspection, it is difficult to determine whether or not the device is above the above.

[0006] An object of the present invention is to provide a foreign matter detecting device which can detect the detection sensitivity, correct the fluctuation in a shorter time, and always detect with the stable detection sensitivity in order to solve such a problem.

[0007]

A foreign matter inspection apparatus according to the present invention comprises a stage on which a sample to be measured is placed, a light emitting section for projecting light onto the surface of the sample to be measured, and scattered light reflected from the sample to be measured. In a foreign matter inspection device having a photoelectric conversion element to be captured and a size conversion circuit for determining the size of a foreign matter attached by the output value of the photoelectric conversion element, the stage is arranged on the same plane as the measurement sample and A light-detecting section for detecting light of the light-emitting section and a reference sample to which standard particles are attached, a storage section for storing a reference value of light intensity obtained from the light-detecting section and the reference sample, the light-emitting section and the light Comparing the intensity of scattered light from the sample to be measured and the reference value,
And a control unit that adjusts the sensitivity of the photoelectric conversion element.

[0008]

The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a foreign matter inspection apparatus showing an embodiment of the present invention. As shown in FIG. 1, this foreign matter inspection apparatus includes a reference sample 13 for calibrating the size of the foreign matter attached to the sample 7 to be measured, and a light detection section 1 for detecting the light from the light emitting section 3.
0 is placed on the stage 8 on the same plane as the sample to be measured 7,
Intensity of light from the light emitting unit 3, reference intensity of the light, scattered light from the measured sample 7, and scattering of the reference in the storage unit 12 that stores the intensity of the reference light and the intensity of the scattered reference light. That is, the control unit 11 that compares the light intensity and gives a correction command to the sensitivity adjustment circuit is provided. Other than that, it is the same as the conventional example.

Next, the operation of this foreign matter inspection apparatus will be described. First, the light detector 3 is irradiated with light from the light emitting unit 3, and the reference light intensity value obtained from the light detector 10 is stored in the storage unit 12. Then, the same light is projected on the reference sample 13,
The scattered light is made to enter the photoelectric conversion element 2, and the intensity value of the reference scattered light converted into the photocurrent is stored in the storage unit 12.

After the preparation is completed in this way, the light emitting unit 3
Projects light onto the surface of the sample 7 to be measured. The scattered light reflected from the sample to be measured enters the photoelectric conversion element 2. next,
The control unit 11 extracts the reference light intensity value and the scattered light intensity value from the storage unit 12 and compares them with the intensity of the scattered light from the photoelectric conversion element 2. If there is a difference between the scattered light intensity value and the reference light intensity value or scattered light intensity value, the sensitivity adjustment circuit 4 is instructed to correct only the difference. The sensitivity adjustment circuit corrects the voltage applied to the photoelectric conversion element 2.

As described above, the storage unit for storing the reference light projection intensity and the scattered light intensity in advance is provided, and the light receiving unit is provided by comparing the measured light intensity and the obtained scattered light intensity with the reference value. Since the sensitivity of the photoelectric conversion element is corrected,
The size conversion circuit always gives a stable digital signal and can make an accurate judgment. Particularly, by disposing the reference sample and the photodetector for obtaining the reference value on the same surface of the sample to be measured, there is an advantage that a more reproducible measurement value can be obtained. If necessary, an abnormality detection circuit may be provided in the control unit to warn the abnormality when it is determined that the difference from the reference value is large.

[0013]

As described above, according to the present invention, the reference sample for generating the reference scattered light and the photodetector for detecting the reference light are arranged on the same surface as the material to be measured. A storage unit that stores the reference value of the light intensity obtained from the detector, compares the intensity of the light used for the measurement and the intensity of the scattered light from the measured sample with the reference value, and the scattered light from the measured material. By providing the control unit that corrects the sensitivity of the photoelectric conversion element that receives light, it is possible to obtain a foreign substance inspection apparatus that can correct the light intensity in a shorter time and perform measurement with stable detection sensitivity.

[Brief description of drawings]

FIG. 1 is a block diagram of a foreign matter inspection apparatus showing an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional foreign matter inspection device.

FIG. 3 is a side view showing a reference sample.

FIG. 4 is a waveform diagram showing a photovoltaic voltage due to trapped scattered light.

[Explanation of symbols]

 1 size conversion circuit 2 photoelectric conversion element 3 light emitting section 4 sensitivity adjustment circuit 5 A / D converter 6 display section 7 sample to be measured 8 stage 9 standard particles 10 photodetector 11 control section 12 storage section 13 reference sample

Claims (1)

[Claims] 1. A stage on which a sample to be measured is placed, a light emitting section which projects light onto the surface of the sample to be measured, a photoelectric conversion element which captures scattered light reflected from the sample to be measured, and a photoelectric conversion element of this photoelectric conversion element. In a foreign matter inspection device having a size conversion circuit that determines the size of a foreign matter that adheres based on an output value, a light detection unit and a standard that are arranged on the same surface as the measurement sample on the stage and that detect the light of the light emitting unit A reference sample to which particles are attached, a storage unit that stores the reference value of the light intensity obtained from the light detection unit and the reference sample, the intensity of the light of the light emitting unit and the scattered light from the measured sample, and the reference. A foreign matter inspection device, comprising: a control unit that adjusts the sensitivity of the photoelectric conversion element in comparison with a value.