JPH0915134A - Method and equipment for inspecting particle - Google Patents

Abstract

PURPOSE: To obtain method and equipment for inspecting a particle, which can not be inspected conventionally, at high sensitivity even if the filming process is proceeding. CONSTITUTION: The method for inspecting a particle comprises first step for projecting laser light vertical to a wafer 5 and receiving the reflected light thus deciding whether any particle is present and counting the number of particles if any, second step for projecting laser light at an incident angle of 45 deg. to a transparent film formed on the wafer 5 and counting the number of particles from the reflected light, third step for projecting P polarized laser light at an angle of depression of 20 deg. to a reflecting film formed on the wafer 5 and counting the number of particles from the reflected light, and fourth step for projecting S polarized laser light at an angle of depression of 20 deg. to a metal film formed on the water 5 and counting the number of particles in any from the reflected light.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, along with the ultra-miniaturization of ULSI devices, there is an increasing need for clean processes. Above all, the particle inspection technique is an important technique from the viewpoints of yield control of semiconductor devices and device management. Conventional particle inspection uses a light source that oscillates a single-wavelength laser to irradiate the wafer vertically with a laser,
The scattered light of the laser is received by the light receiving portion, and the signal of the light receiving portion is processed by using a computer. Thereby, the particles are measured and the particles on the wafer are inspected.

[0003]

However, since the particle inspection method of this conventional example is only the measurement by vertically irradiating the laser beam of a single wavelength, the oxide film formation from the initial bare silicon wafer, As the film forming process progresses to form a polysilicon film and a metal film, sufficient sensitivity cannot be obtained and desired particles cannot be measured.

The present invention solves the problems of the prior art example. Even if the film forming process progresses, sufficient sensitivity can be obtained, and particles that could not be detected in the past can be detected. It is an object of the present invention to provide an inspection method and an inspection device.

[0005]

According to a first aspect of the present invention, there is provided a method for inspecting particles, wherein laser light is incident on a semiconductor substrate at a first incident angle, light reflected by the semiconductor substrate is received, and the received light signal is used. The first step of calculating the presence or absence of particles and the number of particles, a transparent film is formed on a semiconductor substrate, laser light is incident on the semiconductor substrate at a second incident angle, and light reflected by the semiconductor substrate is received. The second step of calculating the presence or absence and the number of particles using the received light signal, and forming a reflective film on the semiconductor substrate, and making P-polarized laser light incident on the semiconductor substrate at a third incident angle. Then, the third step of receiving the light reflected by the semiconductor substrate and calculating the presence / absence and the number of particles using the received light signal, and forming a metal film on the semiconductor substrate to obtain S-polarized laser light. Semiconductor substrate at fourth angle of incidence Incident, receiving light reflected from the semiconductor substrate, is intended to include a fourth step of performing the calculation of presence and number of particles using the received light signal.

A particle inspection apparatus according to a second aspect of the present invention includes a first laser light source which is incident on the semiconductor substrate at a first incident angle, and a second laser light source which is incident on the semiconductor substrate at a second incident angle. A third laser light source that oscillates S-polarized laser light that enters the semiconductor substrate at a third incident angle, and a fourth laser light source that oscillates P-polarized laser light that enters the semiconductor substrate at a fourth incident angle. A laser light source, and light receiving means for respectively receiving the light that has been incident by the first laser light source or the fourth laser light source and reflected by the semiconductor substrate,
And a calculator that inputs the light receiving signals of the light receiving means by the first laser light source or the fourth laser light source to calculate the presence or absence and the number of particles.

According to a third aspect of the present invention, in the particle inspection method, the P-polarized laser light is incident on the semiconductor substrate at the first incident angle, the light reflected by the semiconductor substrate is received, and the light reception signal is used to detect the particle. The first step of calculating the presence / absence and the number of the particles, the S-polarized laser light is incident on the semiconductor substrate at a second incident angle, the light reflected by the semiconductor substrate is received, and the light reception signal is used to generate particles. And the second step of calculating the presence and absence and the number thereof.

According to a fourth aspect of the present invention, there is provided a particle inspection apparatus, wherein a laser light source that oscillates a P-polarized laser beam that is incident on a semiconductor substrate at a first incident angle and an S-polarized light that is incident on the semiconductor substrate at a second incident angle. A laser light source that oscillates the laser light, a light receiving unit that receives the P-polarized reflected light of the semiconductor substrate and a light receiving unit that receives the S-polarized reflected light, and a light receiving signal of the light receiving unit. And a computer for inputting and calculating the presence or absence of particles and the number of particles.

[0009]

According to the particle inspection method of claim 1,
In the first step and the second step, the wafer is irradiated while changing the incident angle of the laser beam, and in the third step and the fourth step, the laser beam is changed from P polarized light to S polarized light. It is possible to measure the particles on the wafer with high sensitivity by supplementing the insufficient measurement sensitivity with a single laser and suppressing the influence of the film surface, and it is possible to measure desired particles that could not be detected in the conventional example. .

According to the particle inspection apparatus of claim 2, since it can be applied to the particle inspection method of claim 1, it has the same effect as that of claim 1. According to the particle inspection method of claim 3, since the laser light is changed from P-polarized light to S-polarized light, insufficient measurement sensitivity due to a single laser of normal incidence is compensated, and the influence of the film surface is suppressed to suppress the influence on the wafer. Particles can be measured with high sensitivity, and desired particles that could not be detected in the conventional example can be measured.

Since the particle inspection apparatus of claim 4 can be applied to the particle inspection method of claim 3, it has the same effect as that of claim 1.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. A particle inspection device will be described. FIG. 1 shows a configuration including an optical system,
FIG. 2 shows a scanning system when vertically incident on the wafer. In FIG. 1, reference numeral 1 is a first laser light source that generates P-polarized Ar laser light having a wavelength of 488 nm. The laser light oscillated from this is arranged so as to enter the area on the bare silicon wafer 5 of the semiconductor substrate placed horizontally through the half mirror 12 at the first incident angle vertically. Further, a P-polarized light receiving portion 6 which is a light receiving means is arranged so as to receive the scattered light reflected on the wafer 5. Further, these received light signals are input to a computer 8 having a computer as an embodiment, and the computer 8 calculates the presence / absence and the number of particles.

Reference numeral 2 is a second laser light source for generating P-polarized Ar laser light having a wavelength of 488 nm. The laser light oscillated from this is arranged so as to be incident on a region on the wafer 5 on which an oxide film, which is a transparent film, which is horizontally placed is formed at an angle of a depression angle of 45 degrees which is a second incident angle. .
Further, the light receiving section 6 is arranged so as to receive the scattered light reflected on the wafer 5. Further, these received light signals are input to the calculator 8 and the same calculation as above is performed.

Reference numeral 3 is a third laser light source for generating P-polarized Ar laser light having a wavelength of 488 nm. The laser light oscillated from this is arranged so as to be incident on a region on the wafer 5 on which a polysilicon film which is a reflection film is placed horizontally, at a third incident angle of a depression angle of 20 degrees. . Further, a polarization beam splitter 10 is placed so as to receive the scattered light reflected on the wafer 5. This polarization beam splitter 10 allows P-polarized light and S-polarized light.
A P-polarized light receiving portion 6 and an S-polarized light receiving portion 7 which constitute the light receiving means are arranged so that the light separated into the polarized light enters. Further, the P-polarized light reception signal and the S-polarized light reception signal are input to the computer 8 to perform the same calculation as above.

Reference numeral 4 is a fourth laser light source for generating S-polarized Ar laser light having a wavelength of 488 nm. The laser light emitted from this is arranged so as to be incident on a region on the wafer 5 on which the aluminum film, which is a metal film, which is placed horizontally is formed at an angle of a depression angle of 20 degrees which is a fourth incident angle.
In addition, a light receiving portion 7 is arranged on which the scattered light reflected on the wafer 5 is incident. These received light signals are input to the calculator 8 and the presence or absence of particles and the number of particles are calculated in the same manner as described above.

Next, a particle inspection method using this particle inspection apparatus will be described. That is,
This particle inspection method includes a first step, a second step, a third step, and a fourth step. In the first step, laser light is incident on the semiconductor substrate wafer 5 at a first incident angle, the light reflected by the wafer 5 is received, and the presence or absence of particles and the number of particles are calculated using the received light signal. As shown in FIG. 2, the wavelength 488 of the first laser light source is
A region of the bare silicon wafer 5 placed horizontally is vertically irradiated with an Ar laser beam of nm through the half mirror 12. The size of the stage 11 on which the wafer 5 is placed is almost the same as the size of the wafer 5. The stage 11 first moves in the + x direction within the apparatus in steps of about 20 μm while the wafer 5 is placed. As a result, as the stage 11 on which the wafer 5 is placed in the apparatus moves, the Ar laser light is emitted by 2
The wafer 5 can be scanned with a step interval of 0 μm. When the laser light has finished scanning from one end to the other end of the wafer 5, the stage 11 then moves 20 μm in the + y direction with the wafer 5 still mounted, and then moves in the −x direction at a step interval of about 20 μm. To do. By repeating this operation, the entire surface of the wafer 5 can be scanned with laser light.

The light receiving component reflected on the wafer 5 is converted into an electric signal by the light receiving section 6. This signal output is sent to the computer 8, where the presence or absence and the number of particles 9 on the bare silicon wafer 5 are detected by calculation processing. As a result, particles of 0.1 μm or more can be detected on the bare silicon wafer. In the second step, a transparent film is formed on the semiconductor substrate wafer 5, laser light is incident on the wafer 5 at a second incident angle, the light reflected by the wafer 5 is received, and the received light signal is used. The presence / absence of particles and the number of particles are calculated. That is, an oxide film of about 500 nm is formed on the bare silicon wafer 5 by thermal oxidation. In FIG. 1, the wavelength 488 of the second laser light source 2 is
The Ar laser beam of nm is irradiated at an angle of 45 degrees on the region of the wafer 5 on which the oxide film placed horizontally is formed.
After scanning the entire surface of the wafer 5 with a laser beam in the same manner as the scanning in the first step, the P-polarized component reflected on the wafer 5 is converted into an electric signal by the light receiving section 6. This output signal is sent to the computer 8, where the presence or absence and the number of particles 9 on the wafer 5 are detected by calculation processing. When an oxide film is formed on the bare silicon wafer 5, the reflected light is scattered due to the influence of the film surface, but the influence of the oxide film surface can be suppressed by providing an irradiation angle of 45 degrees. Particles above 0.2 μm can be detected.

In the third step, a reflection film is formed on the semiconductor substrate wafer 5, P-polarized laser light is incident on the wafer 5 at a third incident angle, and the light reflected by the wafer 5 is received. The presence or absence of particles and the number of particles are calculated using the received light signal. LPCVD of polysilicon film on wafer 5
The film is formed to a thickness of about 400 nm by In FIG. 1, the third
The P-polarized Ar laser light 3 having a wavelength of 488 nm of the laser light source 3 is irradiated onto a region on the wafer 5 on which the polysilicon film is horizontally placed at a depression angle of 20 degrees.
After the entire surface of the wafer 5 is scanned with the laser beam, the wafer 5
The S-polarized component reflected above is converted into an electric signal by the light receiving unit 6. Then, this output signal is sent to the computer 8.
Then, the presence or absence and the number of the particles 9 on the wafer 5 are detected by the calculation processing here. When a polysilicon film is formed on the bare silicon wafer 5, for example, when a polysilicon film having a thickness of 400 nm is formed on the surface of the wafer 5, the polysilicon film is irradiated with laser light at a high angle. Irradiated light is diffusely reflected on the surface of the and particles cannot be accurately measured. Here, by giving the depression angle of 20 degrees, it is possible to suppress the influence of the unevenness of the film surface to a low level, and it is possible to detect particles of 0.25 μm or more on the polysilicon film.

In the fourth step, a metal film is formed on the semiconductor substrate wafer 5, S-polarized laser light is incident on the wafer 5 at a fourth incident angle, and light reflected by the wafer 5 is received. The presence or absence of particles and the number of particles are calculated using the received light signal. That is, an aluminum film having a thickness of about 700 nm is formed on the wafer 5 by the sputtering method. In FIG. 1, the S-polarized Ar laser light 4 having a wavelength of 488 nm of the fourth laser light source 4 is radiated at a depression angle of 20 degrees onto a region on the wafer 5 on which the aluminum film is placed horizontally. After scanning the entire surface of the wafer 5 with laser light in the same manner as described above, the S-polarized component reflected on the wafer 5 is converted into an electric signal by the light receiving section 7. This output signal is sent to the computer 8,
Here, the presence or absence and the number of particles 9 on the wafer 5 are detected by calculation processing. When the aluminum film is formed on the bare silicon wafer 5, the reflected light is considerably scattered due to the influence of the unevenness of the film surface, but the influence of the film surface is minimized by providing the irradiation angle of 20 degrees. Therefore, particles of 0.3 μm or more can be detected on the aluminum film.

According to the particle inspection method of this embodiment, the wafer 5 is irradiated while changing the incident angle of the laser beam in the first step and the second step, and the laser beam is irradiated in the third step and the fourth step. Since the light is changed from P-polarized light to S-polarized light, it is possible to compensate for the insufficient measurement sensitivity of the single laser of normal incidence, suppress the influence of the film surface, and measure the particles on the wafer 5 with high sensitivity. It is possible to measure desired particles that could not be detected in the conventional example.

Further, since the particle inspection apparatus can be applied to the above-described particle inspection method, it has the same effects as the above. The second embodiment of the present invention is shown in FIGS. That is, in this particle inspection apparatus, in the first embodiment, the first laser light source 1 uses a P-polarized He-Ne laser light source with a wavelength of 594 nm, and the fourth laser light source 3 uses an S-polarized He with a wavelength of 633 nm. The -Ne laser light source is used, and the second laser light source and the third laser light source are omitted.

The laser light oscillated from the first laser light source 1 is arranged so as to vertically enter the bare silicon wafer 5 placed horizontally. On the other hand, the fourth laser light source 4
The laser light oscillated from is incident on the bare silicon wafer 5 placed horizontally at a low depression angle of 20 degrees. Further, the polarization beam splitter 10 is placed so that the scattered light reflected on the wafer 5 enters. Further, the polarization beam splitter 10 causes P
The P-polarized light receiving portion 6 and the S-polarized light receiving portion 7 are arranged so that the light separated into the polarized light and the S-polarized light enters, respectively. In addition, the computer 8 calculates the P-polarized signal and the S-polarized signal.
I am trying to enter it.

The operation when particles are measured using the apparatus thus configured will be described.
That is, the P-polarized He-Ne laser light having a wavelength of 594 nm is vertically irradiated onto the wafer 5 placed horizontally.
On the other hand, the S-polarized He-Ne laser light having a wavelength of 633 nm is irradiated onto the wafer 5 at a low angle of 20 degrees. These laser lights are applied to the same area on the wafer 5. The light of the laser light reflected on the wafer 5 enters the polarization beam splitter 10 where it is separated into a P-polarized component and an S-polarized component. The separated P-polarized component is incident on the light receiving section 6 which is a P-polarized light receiving means and is converted into an electric signal. Further, the separated S-polarized component is incident on the light receiving portion 7 which is a light receiving means for S-polarized light and is converted into an electric signal. These output signals are sent to the computer 8, where the presence or absence of the particles 8 is detected by the calculation process, and the particle size is calculated.

In the inspection method using the particle inspection apparatus, in the first step, the P-polarized laser beam is incident on the wafer 5 of the semiconductor substrate at the first incident angle, and the wafer 5 is removed.
The light reflected by is received, and the presence or absence of particles and the number of particles are calculated using the received light signal. In the second step, the S-polarized laser light is incident on the wafer 5 at the second incident angle, the light reflected by the wafer 5 is received, and the presence / absence of particles and the number of particles are calculated using the received light signal. .
In this method, the first step and the second step may be performed in the order of the steps, but the first step and the second step may be performed simultaneously.

FIG. 4 is a relational diagram of the scattering cross section showing the scattered light intensity with respect to the particle diameter of particles. White circles are S-polarized light having a wavelength of 633 nm, and black circles are P-polarized light having a wavelength of 594 nm. As is clear from FIG. 4, the P-polarized light has a larger scattered light intensity with respect to the particle size than the S-polarized light with a particle size of 0.3 μm or more. When measuring, highly sensitive measurement can be performed.

However, with P-polarized light, the sensitivity drops sharply when the particle size becomes smaller than 0.3 μm. On the other hand, with S-polarized light, the sensitivity increases from around 0.35 μm, and a scattered light intensity that is about an order of magnitude higher than that of P-polarized light with reduced sensitivity is obtained. Therefore, when measuring minute particle particles having a size of 0.1 to 0.3 μm, the S-polarized light can be used for measurement with higher sensitivity than the P-polarized light.

Therefore, when measuring with an S-polarized laser light source, only data of 0.3 μm or less is adopted, and when measuring with an S-polarized laser light source, only data of 0.3 μm or more is adopted. The most sensitive particle can be measured by switching between the two types of laser light of polarized light and P-polarized light and performing measurement under optimum conditions.

In the above embodiment, the laser light source was Ar or He-Ne and the irradiation angle was set to a predetermined angle. However, the present invention is not limited to this, and the type of laser light source and the irradiation angle may be different. good. In addition, at least one pair of the first laser light source 1 to the fourth laser light source 4 is shared, and a swing structure is adopted to change the incident angle, and polarization is changed to mutually change P polarization and S change. Variable means may be adopted.

[0029]

According to the particle inspection method of the first aspect, the wafer is irradiated while changing the incident angle of the laser beam in the first step and the second step, and the third step and the fourth step. Since the laser light is changed from P-polarized light to S-polarized light by the above method, it is possible to compensate for the insufficient measurement sensitivity of a single vertically incident laser and to measure particles on a wafer with high sensitivity, which cannot be detected in the conventional example. There is an effect that desired particles can be measured.

According to the particle inspection apparatus of the second aspect, since it can be applied to the particle inspection method of the first aspect, it has the same effect as the first aspect. According to the particle inspection method of claim 3, since the laser light is changed from P-polarized light to S-polarized light, insufficient measurement sensitivity due to a single laser of normal incidence is compensated, and particles on the wafer are measured with high sensitivity. Therefore, it becomes possible to measure desired particles that cannot be detected in the conventional example.

Since the particle inspection apparatus of claim 4 can be applied to the particle inspection method of claim 3, it has the same effect as that of claim 1.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a particle inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a scanning system of a particle inspection device.

FIG. 3 is an explanatory diagram of a particle inspection apparatus according to a second embodiment.

FIG. 4 shows S-polarized laser light and P-polarized laser light,
It is a relationship diagram which shows the scattering cross section with respect to the particle diameter of a particle particle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st laser light source 2 2nd laser light source 3 3rd laser light source 4 4th laser light source 5 Bare silicon wafer of a semiconductor substrate 6 P-polarized light-receiving part 7 S-polarized light-receiving part 8 Calculator 9 Particles

Claims (4)

[Claims] 1. A first step in which laser light is incident on a semiconductor substrate at a first incident angle, light reflected by the semiconductor substrate is received, and the presence / absence of particles and the number of particles are calculated using the received light signal. A transparent film is formed on the semiconductor substrate, laser light is incident on the semiconductor substrate at a second incident angle, the light reflected by the semiconductor substrate is received, and the presence / absence of particles is detected using the received light signal. The second step of calculating the number, and forming a reflection film on the semiconductor substrate, injecting P-polarized laser light into the semiconductor substrate at a third incident angle, and reflecting the light reflected by the semiconductor substrate. A third step of receiving light and calculating the presence and number of particles by using the received light signal, and forming a metal film on the semiconductor substrate and applying S-polarized laser light at a fourth incident angle to the semiconductor Incident on the substrate, the semiconductor A fourth step of receiving the light reflected by the substrate and calculating the presence / absence and the number of particles using the received light signal. 2. A first laser light source incident on a semiconductor substrate at a first incident angle, a second laser light source incident on the semiconductor substrate at a second incident angle, and a third incident light on the semiconductor substrate. A third laser light source that oscillates S-polarized laser light that enters at an angle, a fourth laser light source that oscillates P-polarized laser light that enters the semiconductor substrate at a fourth incident angle, and the first laser light source. Light receiving means for respectively receiving the light incident from the laser light source or the fourth laser light source and reflected by the semiconductor substrate, and the light receiving signal of the light receiving means by the first laser light source or the fourth laser light source are input. Then, a particle inspection apparatus comprising a computer for calculating the presence or absence of particles and the number of particles. 3. A P-polarized laser beam is first applied to a semiconductor substrate.
The first step of receiving the light incident at the incident angle of and reflected by the semiconductor substrate and calculating the presence or absence and the number of particles using the received light signal, and the second incident angle of the S-polarized laser light And a second step of receiving the light incident on the semiconductor substrate and reflected by the semiconductor substrate, and using the received light signal to calculate the presence or absence and the number of particles. 4. P incident on a semiconductor substrate at a first incident angle
A laser light source that oscillates polarized laser light, a laser light source that oscillates S-polarized laser light that enters the semiconductor substrate at a second incident angle, and a light-receiving unit that receives the P-polarized reflected light of the semiconductor substrate. And a particle inspection device comprising a light receiving unit having a light receiving unit for receiving the S-polarized reflected light, and a computer for inputting a light receiving signal of the light receiving unit to calculate the presence or absence and the number of particles.