JPH085569A - Particle measuring apparatus and particle inspection method - Google Patents

Abstract

PURPOSE:To obtain an apparatus for measuring a particle which can not be detected using a single wavelength laser beam. CONSTITUTION:A wafer 13 is set horizontally. A laser beam source 11 is disposed to irradiate the wafer 13 vertically with a P polarized He-Ne laser light while a laser beam source 12 is disposed to irradiate the wafer 13 vertically with S polarized He-Ne laser beam the laser beam sources 11, 12 are disposed such that a same region on the wafer 13 is irradiated with the laser beam. A polarizing beam splitter 14 is disposed to receive the laser beam reflected on the wafer 13. The reflected beam is separated through the polarizing beam splitter into a P polarized component and an S polarized component which are received, respectively, at light receiving sections 15, 16. The P polarized and S polarized components are converted into electric signals which are processed by means of a computer 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle inspection device and an inspection method.

[0002]

2. Description of the Related Art In recent years, along with the ultra-miniaturization of ULSI devices, the need for process cleansing is increasing. Among them, particle inspection is an important technique from the viewpoint of yield control of semiconductor devices and device management.

In the conventional particle inspection, an inspection device as shown in FIG. 6 has been used. That is, it has a light source 1 that oscillates a laser beam having a single wavelength, and irradiates a bare silicon wafer 2 (hereinafter referred to as a wafer) with a laser 3 vertically. The laser scattered light 4 is received by the light receiving unit 5, and the computer 6 is used to process the scattered light 4 for particle measurement.

[0004]

However, in the conventional structure, when the size of the particles 7 on the wafer 2 ranges from a very small size to a maximum size, a single wavelength vertical laser light irradiation is used. Sufficient sensitivity could not be obtained only by measurement, and sufficient particle measurement could not be performed.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a particle inspection apparatus and inspection method capable of detecting particles having various particle sizes.

[0006]

In order to achieve this object, a particle measuring apparatus of the present invention comprises a semiconductor substrate, a light source which oscillates a P-polarized laser beam which is vertically incident on the semiconductor substrate, A light source that oscillates S-polarized laser light that is vertically incident on the semiconductor substrate;
A beam splitter for separating the light reflected by the semiconductor substrate into a P deflection component and an S deflection component, a first light receiving portion for receiving the separated P deflection component, and a second light receiving portion for receiving the separated S deflection component. And a computer that processes a signal from the light receiving unit.

Further, a semiconductor substrate, a light source that oscillates P-polarized laser light that is vertically incident on the semiconductor substrate, and a light source that oscillates S-polarized laser light that is incident on the semiconductor substrate at a low angle. The light reflected by the semiconductor substrate is converted into P
A beam splitter that separates the deflection component and the S deflection component, a first light receiving unit that receives the separated P deflection component, a second light receiving unit that receives the separated S deflection component, and a signal from the light receiving unit And a computer for processing.

In order to achieve this object, the particle inspection method of the present invention is a laser in which a P-polarized laser beam and an S-polarized laser beam are vertically irradiated to the same region on a semiconductor substrate and the semiconductor substrate is irradiated with the laser beam. The reflected light of light is separated into a P-polarized component and an S-polarized component, the separated P-polarized component and S-polarized component are received, and the received light intensity is converted into an electric signal, which is calculated.

[0009]

With the above structure, since the P-polarized laser light and the S-polarized laser light are incident, it is possible to supplement the insufficient sensitivity of the single laser, and to measure sufficient particles. it can.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of an optical system of the apparatus of the present invention.

Reference numeral 11 denotes He- which is P-polarized and has a wavelength of 594 nm.
A Ne laser light source, 12 is an S-polarized He-Ne laser light source having a wavelength of 633 nm. These are arranged so that the emitted laser light is vertically incident on the same region of the bare silicon wafer 13 placed horizontally. Further, the polarization beam splitter 14 is placed so that the scattered light reflected on the wafer 13 is incident. Furthermore, the P-polarization component and S
The light receiving portion 15 for the P polarization component and the light receiving portion 16 for the S polarization component are arranged in correspondence with these polarization components so that the light separated into the polarization components enters. The P-polarized signal and the S-polarized signal are input to the computer 17.

The operation in the case of performing particle measurement using the apparatus thus configured will be described below.

A P-polarized He-Ne laser beam having a wavelength of 594 nm and an S-polarized He-Ne laser beam having a wavelength of 633 nm are vertically irradiated to the same region on the wafer 13 placed horizontally. The light reflected on the wafer 13 enters the polarization beam splitter 14, where the P polarization component and S
It is separated into a polarized component. The separated P-polarized component is converted into an electric signal by the P-polarized component light receiving unit 15. The separated S-polarized component is converted into an electric signal by the S-polarized component light receiving unit 16. Then, these signal outputs are sent to the computer 17. Then, the presence or absence of the particles 18 is detected by the calculation process here, and the calculation is performed for each particle size.

FIG. 2 shows the configuration of the scanning system of the stage of the present invention. The stage 19 in the apparatus is almost the same size as the wafer, and the wafer 13 is placed on it. On the stage 19, with the wafer 13 still mounted, the inside of the device is increased in steps of about 20 μm.
Move in x direction. As a result, the wafer 1 in the apparatus is
Along with the movement of the stage 19 on which the wafer No. 3 is placed, two types of He—Ne laser light scan the wafer 13 at step intervals of 20 μm. When the laser light has finished scanning from one end to the other end of the wafer 13, the stage 19 then moves 20 μm in the + y direction with the wafer 13 still mounted,
Subsequently, the movement is performed in the −x direction with a step interval of about 20 μm. By repeating this operation, the entire surface of the wafer 13 can be scanned with laser light. Wafer 1
3 Particles can be measured on the entire surface.

FIG. 3 shows an S-polarized laser (wavelength 633n).
m) and P-polarized laser (wavelength 594 nm), the scattered light intensity with respect to the particle size of the particle particles is shown. Here, the scattered light intensity is expressed in a unit called a scattering cross section (μm ² ).

When particle particles having a size of 0.1 to 0.3 μm are measured, the scattered light intensity for each particle size is
The intensity of the S-polarized scattered light is about one order of magnitude higher than that of the P-polarized scattered light. Therefore, when measuring particle particles of 0.1 to 0.3 μm, it is possible to perform measurement with higher sensitivity by using S-polarized light as compared with P-polarized light.

However, in the case of S-polarized light, as shown in FIG. 3, the sensitivity suddenly drops from around 0.3 μm.
On the other hand, in the P-polarized light, the intensity of scattered light is higher than that in the S-polarized light in which the sensitivity suddenly increases from around 0.35 μm and the sensitivity drops. Therefore, when measuring particle particles larger than 0.35 μm, P-polarized light can be used to perform measurement with higher sensitivity than S-polarized light.

As described above, by using the two kinds of lasers of S-polarized light and P-polarized light, the most sensitive particle measurement can be performed.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 4 schematically shows the construction of the optical system of the apparatus of the second embodiment of the present invention.

Reference numeral 21 denotes He- which is P-polarized and has a wavelength of 594 nm.
The Ne laser light source 22 is an S-polarized He-Ne laser light source having a wavelength of 633 nm. The laser light emitted from the laser light source 21 is arranged to vertically enter the bare silicon wafer 23 placed horizontally. On the other hand, the laser light emitted from the laser light source 22 is arranged so as to enter the bare silicon wafer 23 placed horizontally at a low angle of 10 degrees in elevation. Further, the polarization beam splitter 24 is placed so that the scattered light reflected on the wafer 23 enters. Further, a P-polarized light receiving portion 25 and an S-polarized light receiving portion 26 are respectively arranged so that the light separated into the P-polarized light and the S-polarized light by the polarization beam splitter 24 enters. The P-polarized signal and the S-polarized signal are input to the computer 27.

The operation in the case of performing particle measurement using the apparatus thus configured will be described below.

He-Ne laser light of P polarization having a wavelength of 594 nm is vertically irradiated onto the wafer 23 placed horizontally. On the other hand, S-polarized He-Ne with a wavelength of 633 nm
The laser light is irradiated onto the wafer 23 at a low angle of 10 degrees. These laser lights are applied to the same area on the wafer 23. The light of these laser lights reflected on the wafer 23 enters the polarization beam splitter 24, where it is separated into a P-polarized component and an S-polarized component. The separated P-polarized component is converted into an electric signal by the P-polarized light receiving unit 25. The separated S-polarized component is converted into an electric signal by the S-polarized light receiving unit 26. Then, these signal outputs are sent to the computer 27. Then, the presence or absence of the particles 28 is detected by the calculation process here, and the calculation is performed for each particle size.

As shown in FIG. 5A, the laser light
When irradiated at a high angle of about 8 to 90 degrees, the laser light is scattered by the particles 28 on the wafer 23. Further, as shown in FIG. 5B, the laser light is also scattered by crystal-derived particles (hereinafter referred to as COP) 29 on the surface of the wafer 23. These two types of scattered light cannot be distinguished. Therefore, if the particles 28 and the COP 29 are simultaneously present on the measured wafer 23, the particles 2
Both 8 and COP29 are detected, and the two cannot be distinguished as long as the measurement results are seen. However, CO
Defects in P29 can affect the electrical properties.
COP2, which is a trace of etching defects in COP29
It has been reported that 9 itself does not affect the electrical characteristics. Therefore, whether the particles 28 or CO
It becomes necessary to distinguish whether it is P29.

Here, FIGS. 5 (c) and 5 (d) show that the wafer 23 is irradiated with laser light at a low angle of about 10 degrees. Scattering by particles 28 on wafer 23 and CO
There is a considerable difference in the state of scattering by P29. By irradiating the wafer 23 with the laser light at a low angle, scattering at the COP 29 on the surface of the wafer 23 is considerably suppressed. Therefore, the laser light is applied to the wafer 2 at a low angle.
By irradiating No. 3, the particles 28 alone can be measured without being affected by the COP 29 on the surface of the wafer 23.

Thus, by irradiating at least one of the two types of lasers at a low angle, the COP
It is possible to measure only the particles 28 without measuring 29.

The third embodiment differs from the second embodiment in that at least one reflective film is formed on the wafer. For example, when a polysilicon film is formed to a thickness of 500 nm on the wafer surface,
When the laser is irradiated at a high angle of about 0 degrees, the surface of the polysilicon film is diffusely reflected, and the particle measurement cannot be performed accurately. Here, one of the laser beams is, for example, 10
By irradiating the wafer at a low angle of about 10 degrees, the influence of diffused reflection on the surface of the polysilicon can be suppressed low. Therefore, the particles on the polysilicon can be measured. In this way, it becomes possible to measure particles when at least one reflective film is formed on the wafer.

[0027]

The present invention comprises a light source which oscillates P-polarized He-Ne laser light and a light source which oscillates S-polarized He-Ne laser light placed so as to be vertically incident on the wafer. Therefore, an excellent inspection method capable of measuring the particles on the wafer with high sensitivity can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical system of a particle inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a scanning system of a particle inspection apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing scattered light intensities of S-polarized laser (wavelength 633 nm) and P-polarized laser (wavelength 594 nm) with respect to particle diameters of particle particles.

FIG. 4 is a diagram showing a schematic configuration of an optical system of an apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a laser light irradiation direction and a light scattering state due to particles on a wafer and particles originating from crystals on the wafer surface.

FIG. 6 is a configuration diagram of a conventional particle inspection device.

[Explanation of symbols]

 11, 12 Laser light source 13 Wafer 14 Polarizing beam splitter 15, 16 Light receiving part 17 Computer 18 Particle 19 Stage

Claims (3)

[Claims] 1. A semiconductor substrate, a light source that oscillates a P-polarized laser beam that is vertically incident on the semiconductor substrate, and an S-polarized laser beam that is vertically incident on the semiconductor substrate. A light source that oscillates, a beam splitter that separates the light reflected by the semiconductor substrate into a P deflection component and an S deflection component, a first light receiving unit that receives the separated P deflection component, and the separated S deflection component A particle measuring apparatus comprising: a second light receiving section for receiving light; and a computer for processing signals from the first and second light receiving sections. 2. A semiconductor substrate, a light source that oscillates P-polarized laser light that is vertically incident on the semiconductor substrate, and a light source that oscillates S-polarized laser light that is incident on the semiconductor substrate at a low angle. A beam splitter that separates the light reflected by the semiconductor substrate into a P deflection component and an S deflection component; a first light receiving unit that receives the separated P deflection component; and a separated S deflection component. A particle measuring device comprising a second light receiving section and a computer for processing signals from the first and second light receiving sections. 3. A P-polarized laser beam and an S-polarized laser beam are vertically irradiated on the same region on a semiconductor substrate, and reflected light of the laser beam irradiated on the semiconductor substrate is a P-polarized component and an S-polarized component. A method for inspecting particles, characterized in that the P-polarized component and the S-polarized component thus separated are received, the received light intensity is converted into an electric signal, and the electric signal is calculated.