JPH01453A - Foreign object detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a foreign matter detection device that detects minute foreign matter present on a substrate with a foreign matter adhesion prevention means having a pellicle formed in a frame attached to the substrate. be.

[Prior art]

A conventional foreign matter inspection device was constructed as shown in FIG. That is, the foreign matter 2 present on the wafer 1 is irradiated with S-polarized laser light 5°6 emitted from the S-polarized laser oscillator 3.4 from two oblique directions, and the foreign matter 2 emits s
+P polarized laser light 7 is reflected. After condensing this S+P polarized laser beam 7 with an objective lens 8, only the S polarized laser beam is blocked by an S polarization cut filter 9, and only the P polarized laser beam 10 is passed through a field-limiting aperture 11 to a photoelectric conversion element 12. Detected by. Only the S-polarized laser beam is reflected from the circuit pattern step. Therefore, the photoelectric conversion cable 1
The presence of foreign matter can be known from the output of step 2.

However, this conventional foreign matter inspection device.

The purpose is to detect foreign matter present on the wafer.

[Purpose of the invention]

In view of the above-mentioned prior art, an object of the present invention is to provide a J8 board with a foreign matter adhesion prevention means in which a pellicle is formed on the frame.
Accurately detects minute foreign matter present on the board surface without being affected by the frame over the entire surface of the board with the circuit pattern, eliminating defective exposure due to foreign matter adhering to the board,
The purpose of the present invention is to provide a foreign object detection device that can significantly improve yields in semiconductor production.

[Summary of the invention]

That is, in order to achieve the above object, the present invention includes a light source, and the light from the light source is passed through the pellicle onto the surface of a substrate equipped with foreign matter adhesion prevention means in which a pellicle is formed in a frame, and is tilted toward each other. A pair of illumination optical systems that perform condensed illumination and a pair of illumination optical systems that face each other from a direction of about 90 degrees on the substrate surface with respect to the direction of illumination by the illumination optical system and direct reflected light from foreign matter existing on the substrate to the pellicle. comprising a pair of detection optical systems for detecting light through the optical system, and a photoelectric conversion means for receiving the light obtained from each optical system and converting it into a signal, and dividing the surface of the substrate into at least four parts to obtain signals from the photoelectric conversion means. This foreign matter detection device is characterized in that it is configured to detect foreign matter attached to the substrate surface over the entire surface of the substrate based on a signal.

In exposure equipment such as reduction projection type automatic mask aligner,
When transferring a circuit pattern formed on a reticle, photomask, etc. onto a semiconductor wafer by step-printing and repeating, if there is a foreign object on the reticle pattern or photomask, the image (shadow) of the foreign object may be lost along with the circuit pattern. After being transferred onto a wafer, all single exposed parts (chips) on the finished wafer may be defective. Therefore, as a measure to prevent the adhesion of foreign matter, a so-called foreign matter adhesion prevention means, in which a pellicle of nitrocellulose or the like is attached to a frame made of metal or the like, is attached after cleaning the substrate such as the reticle or photomask.

By the way, the feature of the present invention is that after the pellicle is attached to the substrate, minute foreign matter on the substrate surface can be detected with high reliability over the entire surface of the substrate without being affected by the frame, pellicle, etc. It is in.

[Embodiments of the invention]

The present invention will be specifically described below based on embodiments shown in the drawings. FIG. 2 is a diagram showing an embodiment of an apparatus for detecting foreign matter on a substrate such as a photomask or reticle when a pellicle body according to the present invention is attached to the substrate. That is, the laser beam 30 emitted from the laser oscillator 27 becomes a linearly polarized wave (horizontal wave) in a specific direction by the polarizing element 29, is totally reflected by the galvano mirror 28 connected to the rotating or swinging motor 34, and is reflected by the lens. 31 and reaches the mirror 32. Then mirror 35a.

The light is incident on the surface of the substrate 21 from an oblique direction at an inclination angle α via 36a, 35b, and 36b. Galvano mirror 28
oscillates at a constant rotation speed, and the lens 31 is an f.0 lens that can linearly scan the laser spora 1-80 on the surface of the substrate 21 in proportion to the rotation angle of the galvanometer mirror 28.

In order to detect the reflected light 25 from 24, the laser beam 30a
, 30b and obliquely above the horizontal plane of the substrate 21 at an inclination angle β, a detector 41a such as an S polarization shut filter is installed.
, 41b, condensing lenses 40a, 40b, and slit-shaped light shielding device 39a.

Detecting devices 37a and 37b, each consisting of photoelectric conversion elements 39b and photoelectric conversion elements 38a and 38b, are respectively installed at symmetrical positions about the center of the reticle in the substrate 21y direction.

The analyzers 41a and 41b are for extracting linearly polarized light waves in a specific direction from the reflected light 25 from the foreign object 24. The extracted light passing through the analyzer is sent to a slit-shaped light blocking device 39a by condenser lenses 40a and 40b.

The light reaches the photoelectric conversion elements 38a and 38b via 39b.

A photoelectric conversion element 38a such as a photomultiplier tube having high sensitivity,
38b generates an electrical signal proportional to the intensity of the received light.

In FIG. 2, a pair of lighting devices 35a, 36a, and 35b,
36b and the detection devices 37a and 37b are provided for the following reason.

5 and 6 show the irradiation direction of the laser beam 3o and the foreign matter 24.
FIG. 3 is a diagram showing the direction in which reflected light 25 is detected. Laser beams 30a and 3ob and reflected light 25 from foreign matter 24 are reflected by the pellicle frame 22.
As a means to prevent the laser beams from being blocked, the substrate 21 is divided into two halves as shown in FIG.
5 is also designed to be detected from the opposite side of the area where the foreign object 24 exists. That is, if the inspection area of the substrate 21 is divided into four parts as shown in FIG. 6, the laser beam 30a is irradiated when inspecting areas A and C, and the laser beam 30b is irradiated when inspecting areas B,
Irradiate when inspecting D. In this case, the laser beam 30a
, 30b, the mirror 32 (Fig. 2) is switched by the motor 33.
This is done by rotating it 90 degrees. The detection device 37a is activated when the laser spot 80 is in the area A or B on the surface of the substrate 21, and the detection device 37b is activated when the laser spot 80 is in the area C or D on the surface of the substrate 21. . That is, in synchronization with the rotation angle of the galvanometer mirror 28, the detection signal of the photoelectric conversion element 38a or 38b, such as a photomultiplier, is made conductive or non-conductive (on/off) by the electric circuit. In addition, the detection sensitivity of the reflected light 25 from the 5'4 object changes depending on whether the foreign object 24 is present near the center of the substrate 21 or the foreign object 24 is present near the edge. The threshold value (slice level) for applying electricity is changed in synchronization with the position of the laser spot 80 on the substrate 21.

FIG. 7 shows an outline of the detection circuit. Photoelectric conversion Hiroshi-f-38
The analog signal of a or 38b is sent to a voltage amplifier 42a, 4
2b to multiplexer/1;3. The multiplexer 43 is a galvanometer mirror F, J4! tj+
"In synchronization with the drive signal 50 shown in FIG. 8(a) which is proportional to the rotation angle output from the device 44, the gate signal 51 shown in FIG.
Only one of the signals of 8b is passed. The analog (?j number 52 shown in FIG. 8(d) is the threshold circuit (comparator) 4
7 is compared with the variable threshold signal 53 shown in FIG. 8(c) generated by the threshold generating circuit 46 which varies the voltage in synchronization with the electric signal output from the galvanometer mirror drive device 44, and the signal shown in FIG. 8(e) is compared with the variable threshold signal 53 shown in FIG. A signal 54 shown is obtained. In this case, when the detection signal 52 exceeds the threshold value 53, the A/D converter 49 converts the peak value of the detection signal 52 into the y-coordinate electric signal 50 obtained from the galvanomirror drive device 44 and the X-coordinate of the table drive device 45. X coordinate ffl obtained from the detection sensor
Since it is stored in the storage device 48 in correspondence with the (x, y) coordinate position on the substrate 21 determined based on the number 3, the (x, y) location of the foreign object can be known, and the foreign object can be detected using a microscope or the like. Later, it is possible to measure the size and shape of the foreign object.

The above explanation is based on the surface foreign matter detection device 85 of the substrate 21.
However, when detecting foreign matter on the lower surface of the substrate 21, it is possible to detect foreign matter on the lower surface of the substrate 21 by installing an additional set of lower surface foreign matter detection devices 90 on the lower surface of the substrate 21 as shown in FIG. .

In this case, the configuration of the device and the configuration of the electric circuit may be exactly the same.

1/] In the reticle for 0 reduction projection type mass aligner,
It is necessary to detect foreign objects of 10 to 20 μm or more on the top surface of the reticle and foreign objects of 2 to 5 μm or more on the bottom pattern surface.
The threshold value of upper/lower surface detection mounting 85.90 is set to the above foreign object detection level.In addition, although the above explanation is based on reticle foreign object inspection, by mounting this device on a mask aligner, it is possible to Also removes foreign matter from
It becomes possible to inspect.

As explained above, in the present invention, the 107 m pellicle frame 22 (thickness 2IIN11.
In order to avoid the influence of the height 4 wn or 6.3 mm), we set a position (α = 22.5° ± 15°) where the substrate surface can be illuminated without being affected by the pellicle frame, as shown in Figure 10.
) with a lighting device (27°29) installed at right angles (90°) to this.
degree ±10 degrees) and diagonally above the board (β = 22.5 degrees ± 15 degrees)
) is provided with a detection device 37 to detect foreign matter on the substrate 2. However, in the present invention, since the illumination light is irradiated onto the substrate 21 from an oblique direction, as shown in FIG. The reflected light 26c from the foreign object 58 on the substrate 23 is mistakenly detected as a foreign object on the surface of the substrate 21. Here, since the foreign object 58 is separated from the substrate 21, the image is out of focus during projection exposure, and no inspection is necessary.

Therefore, the present invention provides a pinhole-shaped light shielding device 57 shown in FIG. 10 and a slit-shaped light shielding device 39 shown in FIG.
By adding this to the detection device, we took measures against false detections. When detecting foreign matter on a substrate surface using a detection device equipped with a pinhole-shaped light shielding device 57 shown in FIG. 10, a table (see FIG. (not shown) and scan in two dimensions.

In addition, when detecting the foreign matter 24 on the surface of the substrate 21 using a detection device equipped with a slit-shaped light shielding device 39 shown in FIG.
- Consists of 0 lens 31, etc. ) is scanned in one direction (X direction), the substrate 21 is placed on an Detection is possible. By employing the pinhole and slit-shaped light shielding device shown in FIGS. 10 and 11 described above in the present invention, the substrate can be protected without being affected by reflected light from the pellicle frame 22 as shown in FIG. Foreign matter on surfaces can be detected with high sensitivity. In addition, by using polarized light for the illumination light and adding an analyzer 41 to the detection device, the difference in polarization angle characteristics of the scattered reflected light between the foreign object and the stepped portion of the circuit pattern can be utilized as described in the prior art. By doing so, it is possible to further improve the sensitivity of minute foreign matter.

Well, in the above example, the smaller the inclination angles α' and β, the more
Changes in polarization angle can be detected effectively, improving detection sensitivity, but due to the influence of the pellicle frame, both α and β angles of 22
．． 5±15 degrees is optimal. Furthermore, detection devices 37a, 37
The uniformity of detection sensitivity can be improved by directing the optical axis b (center of the slit) toward the 42 points in FIG. 6 (line x, x2 when moving the reticle).

〔Effect of the invention〕

As explained above, according to the present invention, the substrate surface is divided into at least four parts and can be detected with the foreign matter adhesion prevention means in which the pellicle is formed on the frame attached to the substrate. 1 to 1 present on a board surface that has a circuit pattern over the entire surface of the board without being affected by
It is possible to accurately detect minute foreign matter with a size of 2 μm, eliminate defective exposure due to foreign matter adhering to the substrate, and contribute to a significant improvement in yield in semiconductor production.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the prior art, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a diagram showing the basic structure of the present invention, and Fig. 4 is a diagram showing the influence of the pellicle frame. 5 is a diagram showing the relationship between the illumination light and the inspection area, and the relationship between the foreign object detection direction and the inspection area. FIG. 6 is a diagram showing the relationship between the inspection area on the board. FIG. 7 is a diagram showing the relationship between the inspection area on the board. FIG. 8 is a diagram showing the signal waveform obtained by the circuit shown in FIG. 7. FIG.
Figure (A) is a diagram showing the case where the detection device shown in Figure 3 is equipped with a pinhole light blocking device, and Figure 10 (B) is a diagram showing the case where the detection device shown in Figure 3 is equipped with a pinhole light shielding device.
11 (Δ) is a diagram showing the case where the detection device is equipped with a slit light shielding device, and FIG. 11 (B) is the A 1 o arrow enlarged view in Figure 11 (A). z, an enlarged view in the direction of arrows, and FIGS. 12(A) and 12(B) are diagrams showing features of the present invention. 21...Substrate 22...Pericle rod frame 23...Pellicle film- 24...Foreign object 27...Laser oscillator 29...Polarizing element 31...F/θ lenses 38, 38 a , 38 b - photoelectric conversion element 3
9.39a, 39b...slit-shaped light shielding device 40,
40a, 40b-condensing lens 4L, 41
a, 4lb - Analyzers 42a, 42b...
・Voltage amplifier 43...Multiplexer 44...Galvano mirror drive device 45...Table drive device 48...Storage device! O ÷ (to), 5 groans...57 in the foreign object detection bag...pinhole-shaped light shielding device

Claims (1)

[Claims] 1. A light source, and a companion illumination optical system that condenses and illuminates the surface of a substrate equipped with a foreign matter adhesion prevention means having a pellicle formed in a frame by tilting the light from the light source to face each other through the pellicle; a pair of detection optical systems configured to detect reflected light from a foreign substance existing on the substrate through the pellicle, facing each other from a direction approximately 90 degrees on the substrate surface with respect to the direction irradiated by the illumination optical system; and photoelectric conversion means for receiving light obtained from each optical system and converting it into a signal,
A foreign matter detection device characterized in that it is configured to detect foreign matter attached to the substrate surface over the entire surface of the substrate based on a signal obtained from the photoelectric conversion means.