JPS62148804A - Inspecting instrument for surface comparison - Google Patents

Abstract

PURPOSE:To eliminate to the need for stable real image information or a sensitivity adjusting function of the real image information to be compared by including a means to calculate a difference with surface shape information to be compared from interference light intensity and reflected light intensity. CONSTITUTION:A reflection mirror 12 is vibrated by a vibrator 13 according to the surface shape information to be compared on a data disk 14. The interference light intensity, a wavelength of light, the laser light intensity for inspection, the laser light intensity for reference, an optical path difference from the inspection surface, the reference surface and a beam splitter 7 are denoted as I, lambda, I1, I2 and X, respectively, 1 is equal to I1+I2+2X(I1.I2)<1/2>cos(4piX1//lambda). Here, since the reflection mirror 12 for reference is moved according to the surface shape information to be compared, in case a shape of the inspection surface on a sample 1 is equal to the comparison information, I is not changed. In case I is changed, it is detected that a defect exist there. Further, in case the reflectivity of the sample is changed according to a location, the correction can be performed by considering a change of I2 from a photomultiplier 5b.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a surface comparison inspection device, and particularly to a surface comparison inspection device that can be applied to automatically inspect the appearance of fine patterns such as LSI wafers and compare them with standard patterns. Regarding inspection equipment.

[Conventional technology]

As a conventional technique, for example, Japanese Patent Publication No. 59-17075
There is a pattern comparison inspection device as shown in Japanese Patent No. 0.

Conventional surface comparison inspection equipment consists of an objective lens that magnifies a single point on a sample, a rotating polygon mirror or vibrating mirror placed in the middle of the optical system to scan the real image, and a light beam that converts the real image into an electrical signal in parallel. It consists of a fiber, a group of photopules, and a high-voltage power supply that individually adjusts the sensitivity of each photopul.

Next, a conventional surface comparison inspection device will be described in detail with reference to the drawings.

FIGS. 3(a) and 3(b) show an example of a conventional surface comparison inspection device.

The surface comparison inspection device shown in FIG. 3 includes an objective lens 33,
A photoful group 36 integrated with an optical fiber 35 having an optical system of a field lens 38, a quadrature lens 39, and a rotating polygon mirror 34, an illumination light 37, a current-voltage converter 42, an analog comparison circuit 44, and an AND circuit 45. 46 and counter 47
, a DA converter 48 , and a DC-DC converter 49 . Here, in FIG. 3(a), 37a,
37b is illumination light that irradiates the surface of the sample 31 through objective lenses 33a and 33b. detection point 32a on the sample,
32b is an objective lens (33a, 33b is magnified, field lens 38a, 38b: imaging lens 39a, 39
b, and is scanned by the rotating polygon mirror 34 to connect the optical fiber 35a.
, 35b. The light that has passed through the optical fibers 35a and 35b reaches the photoful groups 36a and 36b, where it is converted into an electrical signal.

Since the photofull groups 6a and 6b are several tens of thin films, pattern information on the sample is detected in parallel by the photofull groups. For example, the corresponding Hotomaru Comrade 4 (l and 4
If the signals of 0b are compared and they do not match, it is determined that there is a defect on the sample.

To adjust the sensitivity of the photomultiplier, as shown in FIG. 3(a), the sample 31 is positioned so that the detection points 32a and 32b are located at the locations with the highest reflectance within the chip. At this time, Hotomaru 4
The output current i of 1 is converted into voltage by the current-voltage converter 42. The analog comparison circuit 44 compares the output voltage e of the current-voltage converter 42 with a constant voltage Ec, and when e exceeds Ec, a logic "1" is sent to the AND circuit 45, e:>Ec.
When , k sends a logic "'1" to the AND circuit 46. AND circuit 45.46 ANDs the logic signal and the clock pulse 9. When e (Ec, the counter 47 is counted up, and when e>EC, it is counted down. When e=Ec, K is the content of the counter. The content of the counter 47 is converted into an analog signal Ei by the DA converter 18.The DC-DC converter still outputs a high voltage E proportional to the output EiK of the fiDA converter 48.
It is converted into O and applied to the photomultiplier 41. This makes it possible to adjust the photomultisensitivity and correct changes in photosensitivity. .

Clock pulses are cut off during inspection and input only when making corrections before inspection.

[Problem that the invention seeks to solve]

The conventional surface comparison inspection equipment described above enlarges and compares the real image on the sample as a defect detection method, so it has the disadvantage that it requires stable real image information for comparison or a sensitivity adjustment function for the real image information. there were.

[Means for solving problems]

The surface comparison inspection device of the present invention includes a data disk for storing surface shape information to be compared, a means for determining the inspection surface, and an X-Y direction for moving the determined inspection surface in the main scanning and sub-scanning directions of the laser. a table; a vibrator having means for separately irradiating the inspection surface and the reference surface with a laser beam; and means for vibrating the reference surface according to the surface shape information to be compared; means for measuring the intensity of light, means for interfering reflected light from the inspection surface and the reference surface and measuring the intensity of the interference light, and the surface shape information to be compared based on the interference light intensity and the reflected light intensity. and a means for calculating the difference between the two.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the present invention.

The surface comparison inspection device shown in Fig. 1 includes an X-Y table 2 that moves the sample 1 in the X-Y direction, a collimator 6 that converts the laser beam from the laser 3 into parallel light, and a collimator 6 that converts the laser beam from the laser 3 into parallel light. a beam splitter 7 that splits the beam in the direction of the mirror 12 and the sample 1, a quarter plate 8 on the optical path, an objective lens 10 that narrows the laser to a minute position on the sample 1, a half mirror 9, and photofuls 4 and 5. Lens 11 that focuses the image upward
and a vibrator 1 that vibrates based on the information on the data disk 14.
3. The laser beam from the laser 3 is collimated by a collimator 6, and this collimated beam is divided by a beam splitter 7 into a reference laser beam that is transmitted toward the reflecting mirror 12 and an inspection laser beam that is reflected toward the sample 1. It will be done. The polarization planes of the reference laser beam and the inspection laser beam are reversed by the quarter plate 8. The inspection laser beam is focused onto a minute inspection area on the sample 1 by the objective lens 10. Then, it is reflected on sample 1. A portion of the reflected inspection laser beam is reflected by the No. 1-7 mirror 9b, passes through the lens 11C, and the intensity of the inspection laser beam is measured by the photomultiplier 5b. Said half mi t-9b
The inspection laser beam that has passed through the sample 1 and reflected off the sample 1 is superimposed at the beam splitter 7 with the reference laser beam that has passed through the -7 mirror 9a among the laser beams that have been reflected by the reflector 12. The interference is vibrated by the camera element 13 according to the half-plane shape information. Adjust the intensity of the interference light, adjust the wavelength of the light, adjust the intensity of the inspection laser beam1,
When the reference laser light intensity is '2' and the optical path difference between the inspection surface, the reference surface, and the beam splitter is X, I=I, +It+2β, which is 131±2) λ. Here, since the reference reflecting mirror 12 moves according to the surface shape information to be compared, if the shape of the inspection surface on the sample 1 is equal to the comparison information, the change in ■ does not occur.

Therefore, if a change of ■ occurs, it is detected that there is a defect. In addition, if the reflectance of the sample changes depending on the location, the process from Photomaru 5b! It can be corrected by considering changes in .

Next, FIG. 2 is a block diagram for calculating the optical path difference X from the laser beam intensities from the photomuls 4 and 5.

The inspection laser light intensity value from the photomultiplex 5a and the reference laser light intensity value from the photomultiplex 5b are added by an adder 20. When the above-mentioned addition result is subtracted by the subtractor 21 from the interference light intensity (2) from the photomultiplier 4, optical path difference information Δ is obtained. This optical path difference information Δ is divided by the inspection laser light intensity, the reference laser light intensity 2, and the laser light wavelength λ.
When passing through, the optical path difference X is obtained. Since this optical path difference X includes the intensity of reflected light from the inspection surface and the reference reflecting mirror, it is not affected by changes in the reflectance of the inspection surface. By moving the inspection position to be irradiated by the laser using an X-Y table, searching for surface shape information at the moved position from the data disk, and vibrating the reflector 12 using the vibrator 13, the inspection position can be compared with the known surface shape in real time. Comparative inspection is possible without being affected by surface reflectance.

〔Effect of the invention〕

The surface comparison inspection device of the present invention vibrates a reference reflector according to the surface shape to be compared in two-beam interferometry, instead of comparing enlarged real images of the sample surface, and can detect defects from changes in interference light. By providing a monitor for the inspection light intensity and the reference light intensity, it is possible to inspect a sample whose reflectance on the inspection surface varies.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention.
3(a) is a perspective view showing a conventional example, and FIG. 3(b) is a block diagram of calculating the optical path difference from the photomul 4.5 shown in FIG. 3(a). FIG. 2 is a block diagram showing a sensitivity adjustment method. 1... Sample, 2... X-Y table,
3...Le-f-14...Hotomal, 5
...Photomaru, 6...Collimator, 7
...Beam splitter, 8...1/4
λ plate, 9...Half mirror-110...
Objective lens, 11... Lens, 12...
・Reflector, 13... Vibrator, 14...
Data disk, 20... Adder, 21...
...Subtractor, 22...Divider, ■...-
・Interference light intensity, ■, ... Laser light intensity for inspection, ■, ... Laser light intensity for reference, Δ■...
...Optical path difference information, X...Optical path difference, 31...
...Sample, 32...Test point, 33...
・Objective lens, 34...Rotating polygon mirror, 35...
...Optical fiber, 36.40...Photomultiple, 37...Illumination light, 38...Field lens, 39...Imaging lens, 41・・・・・・
...Photomaru, 42...Current voltage converter, 44
...Analog comparison circuit, 45°46...
・AND circuit, 47... Counter, 49...
...DC-DC converter. i...Photomal output current, e...Output voltage, Ec...Constant voltage, Ei...D
A converter output, E. I4 child'' - Yuboshi Isk Figure 1 outside Figure 82

Claims (1)

[Claims] a data disk that stores surface shape information to be compared;
means for determining an inspection surface; an X-Y table for moving the determined inspection surface in the main scanning and sub-scanning directions of the laser; means for separately irradiating the inspection surface and the reference surface with the laser; and the reference surface. a vibrator having means for vibrating according to the surface shape information to be compared; a means for measuring the intensity of reflected light from the inspection surface and the reference surface; and a vibrator that interferes with the reflected light from the inspection surface and the reference surface. A surface comparison inspection apparatus comprising: means for measuring the intensity of the interference light; and means for calculating a difference between the surface shape information to be compared from the interference light intensity and the reflected light intensity.