JPH02216035A - Detection of fine particle - Google Patents

Abstract

PURPOSE:To enable the detection of fine particles with a diameter of 0.1mum and below by irradiating the surface of a substrate with ultraviolet rays to determine a level of scattered light from the surface of the substrate. CONSTITUTION:Light from a laser 3 is made incident into a silicon wafer 1. A condenser lens 4 condenses light scattering vertically from a main surface of the wafer 1. Moreover, a filter 5 allows the passage of a second harmonic of the laser 3 in band and the scattered light passing through the filter 5 is increased with a photomultiplier 6 and a signal thereof undergoes a signal processing 7 to shown on a display 8. Then, when no fine particle exists at the part of the surface of the wafer 1 exposed to light from the laser 3, light is mirror reflected on the surface of the wafer 1 and none thereof enters the lens 4. Therefore, only when the fine particle exists at the part of the surface of the wafer 1, the scattered light from the fine particle enters the lens 4. A moving base 2 on which carrying the wafer 1 can be moved horizontally and a position on the wafer 1 is shifted sequentially to scan entire surface of the wafer 1. Moreover, the movement of the position is inputted into a device 7 thereby enabling the display of the presence of the fine particle of the wafer 1 on a display 8.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for detecting fine particles, particularly for detecting fine particles adhering to the surface of a substrate, and is aimed at detecting fine particles having a diameter of 0.1 μm or less.

For detecting fine particles adhering to the substrate surface.

The present invention relates to a method for detecting microparticles, in which the presence of microparticles is detected from the intensity of scattered light from the substrate surface by irradiating the substrate surface with ultraviolet light (industrial application field). This invention relates to a method for detecting fine particles.

In the process of manufacturing fine patterns for semiconductor devices,
Monitoring the cleanliness of the atmosphere is extremely important. When the pattern width becomes 1 μm or less.

The presence of fine particles with a diameter of 0.1 μm or less has a large effect on the product yield.

Therefore, it is necessary to detect and monitor fine particles with a diameter of 0.1 μm or less that adhere to the semiconductor substrate.

[Conventional technology]

Conventionally, a He-Ne laser (wavelength 6328) was used to detect scattered light from fine particles with a photomultiplier tube.

Counting the number of particles attached to a semiconductor substrate has been carried out. This method makes it possible to detect fine particles with a diameter of about 0.3 μm.

However, with conventional methods, it is extremely difficult to detect fine particles with a diameter of about 0.1 μm.

On the other hand, the processing dimensions of patterns for large-scale integrated circuits are progressing to submicron dimensions, and it is becoming necessary to control particulate contamination more strictly. For example, in the case of 16Mb memory, which is currently being researched and developed, a vacuum width of 0.5 μm is used, so fine particles with a diameter of about 1/10 of that, that is, about 0.05 μm, are used to improve the product yield. It greatly affects performance. In contrast, conventional detection techniques cannot cope with this problem.

[Problem to be solved by the invention]

An object of the present invention is to provide a new method for detecting fine particles with a diameter of 0.1.71 m or less, which has been extremely difficult to detect in the past.

[Means to solve the problem]

The above problem is solved by a particle detection method in which when detecting particles attached to the surface of a substrate 1, the surface of the substrate 1 is irradiated with ultraviolet light and the presence of particles is detected from the intensity of scattered light from the surface of the substrate 1. resolved.

[Effect] First, the principle of the present invention will be explained.

When the radius r of a particle is very small compared to the wavelength of light, the intensity of light scattered by the particle is 0ster *
is given as follows.

= (8π' r6/λ4 D2 )X ((m2
−1)2/ (m” +1)21i□ −(Bπ4
r6 /λ″ D2 )X I (m2-1)”
/ (m2 →-1)2 ) xc o s2 γ engineering * G, 0ster, The 5 catterin
Hof Light and Its Application
ions to Chemistry”, Chem
, Rev.

Vol, 43. pp. 319-365 (1948)
Here 11 and 12 are.

These are the vertical polarization component and the horizontal polarization component of the scattered light intensity, respectively, where r is the radius of the particle, λ is the wavelength of the light, and D is the distance from the particle to the observation point2.
m is the relative refractive index of the fine particles with respect to the surrounding medium, and T is the angle between the incident light and the scattered light.

From the above equation, it can be seen that in order to increase the scattered light intensity, λ can be made smaller.

By using ultraviolet light with a wavelength λ of 450 nm or less, it becomes possible to detect fine particles with a diameter of 0.1 μm or less, which was difficult to detect with a conventional I(e-N e laser (wavelength 6328)).

It is possible to reduce the intensity of scattered light by reducing the wavelength λ, but currently, if λ is made too small, the detection sensitivity of detectors such as photomultiplier tubes that are affected by this decreases.

In addition, in the vacuum ultraviolet region of 200 nm or less, if the atmosphere is air, etc., light absorption occurs and the intensity of scattered light decreases. It is necessary to replace it with gas, etc.

〔Example〕

FIG. 1 is an embodiment of the present invention, showing the configuration of an apparatus for detecting fine particles adhering to the surface of a silicon wafer.

In FIG. 1, ■ is a substrate, which is a silicon wafer, 2 is a silicon wafer,
3 is a moving stage, 3 is a light source and is an Ar+ laser, 4 is a condensing lens, 5 is a filter, 6 is a detector and is a photomultiplier tube, 7 is a signal processing device, and 8 is a display.

A silicon wafer 1 is mounted on a moving table 2 with its main surface horizontal.

The second harmonic of Ar' laser 3 (wavelength 257
nm). The light from the Ar' laser 3 is incident on the silicon wafer 1 obliquely from above. and condenser lens 4
collects light scattered in the vertical direction from the main surface of the silicon wafer 1.

The filter 5 filters the second harmonic of the Ar” laser (wavelength 257
pass the band (nm). The scattered light that has passed through the filter 5 enters a photomultiplier tube 6 and is amplified, and the signal is processed by a signal processing device 7 and displayed on a display 8.

Silicon wafer 1 exposed to light from Ar' laser 3
If there are no particles on the surface, the light will be specularly reflected on the surface of the silicon wafer 1 and will not enter the condenser lens 4.

Scattered light from the particles enters the condenser lens 4 only when particles are present on the surface of the silicone wafer 1 that is exposed to the light from the Ar'' laser 3.

The movable table 2 on which the silicon wafer 1 is mounted can be moved in the horizontal direction. Therefore, by sequentially moving the position of the silicon wafer 1 that is hit by the light from the Ar'' laser 3 and scanning the entire surface of the silicon wafer 1, the amount of movement is further input to the signal processing device 7, and the silicon wafer 1 is
By displaying the entire surface on the display 8, the presence of fine particles on the silicon wafer 1 can be displayed on the display 8 as bright spots.

By using the second harmonic (wavelength 257 nm) of the “Ar” laser, we can replace the conventional He-N e laser (wavelength 6
32.8 nm), the detection sensitivity (ratio of scattered light intensity to incident light intensity) could be increased about 30 times. In addition, 0, 1, which was extremely difficult to detect in the past,
It has become possible to detect fine particles with a diameter of μm or less.

Although FIG. 1 shows a dark-field observation system, it can also be an FJA-field observation system. That is, the condenser lens 4 is set in the direction in which the incident light is specularly reflected on the surface of the substrate 1. In this case, the position where the fine particles are present in the bright field is displayed as a dark spot.

Further, in FIG. 1, the light a3 is an Ar laser and its second harmonic is used, but a first-order ultraviolet light source may also be used.

ArF excimer laser F2 Excimer laser Low pressure mercury lamp Low pressure water root lamp Synchrotron radiation light Wavelength: 193 nm Wavelength: 152 nm Wavelength: 185 nm Wavelength: 254 nm Wavelength: 300 nm or less [Effects of the Invention] As explained above, according to the present invention, two Fine particles with a diameter of 0.1 μm or less attached to the substrate surface can be detected. The method of the present invention is highly effective as a means for monitoring the cleanliness of the atmosphere during the formation of ultrafine patterns for semiconductor devices.

[Brief explanation of the drawing]

Figure 1 is an example It is. In the figure 1 is a substrate, which is a silicon wafer 2 is a moving platform 3 is a light source, which is an Ar' laser 4 is a condensing lens 5 5 is a filter. 6 is a detector, which is a photomultiplier tube. 7 is a signal processing device 8 is the display も flow example No. figure

Claims (1)

[Claims] When detecting fine particles adhering to the surface of the substrate (1), the surface of the substrate (1) is irradiated with ultraviolet light, and the presence of fine particles is detected from the intensity of scattered light from the surface of the substrate (1). A method for detecting fine particles.