JPH08101135A - Foreign matter inspecting device - Google Patents

Abstract

PURPOSE: To stably perform the measurement of foreign matter in the neighborhood of the min. measurable particle size by conducting the surface inspection of a semicon ductor single crystal base board under the condition where the S/N ratio is as great as possible. CONSTITUTION: The foreign matter inspecting device concerned is structured so that foreign matter existing on the surface of a base board is sensed by irradiating the board surface with a laser beam and sensing the diffused beams, and is composed of a laser beam source 8, a polygonal mirror 9 to make straight scan over the surface of the base board 1 with laser beam, a moving means to translate the base board perpendicularly to the straight scan direction, and a sensor 10 to sense the diffused beams from the board. The arrangement further includes a rotating means, which rotates the board a specified angule by angle, and a computer 15 which rotates the board before or after irradiation with laser beam a specified angule by angle, senses the diffused beams by making straight scan with laser beam over the board in each rotational angular position, sets as reference position the rotational angular position where the intensity of the produced diffusive beams becomes minimum, and translates the board perpendicularly to the straight scan direction when at the reference position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign substance inspection apparatus for detecting foreign substances on the surface of a semiconductor single crystal substrate.

[0002]

2. Description of the Related Art In manufacturing a semiconductor single crystal substrate, a pass / fail judgment test is performed at the final stage of the manufacturing process to determine whether foreign matter such as particles adhered to the surface of the substrate is within a predetermined level, and defective products are detected. It is necessary to remove it from the product.

Conventionally, for the inspection of foreign substances adhering to the surface of a semiconductor single crystal substrate, an inspector visually inspects scattered light outside the reflection angle of incident light by irradiating the surface of the substrate with parallel rays of high brightness in a dark room. According to the light intensity of foreign matter, foreign matter such as particles adhering to the substrate surface is distinguished from minute irregularities (hereinafter referred to as surface roughness) on the substrate surface, crystal defects or scratches.

In recent years, the minimum pattern size of VLSI memory circuits is 0.35 μm of 64 MDRAM and 256 MDRAM.
Has been reduced to about 0.25 μm. And
The problematic particle size of adhered particles is about 0.06μ in the former case.
m, the latter is said to be about 0.04 μm.

However, when the particle size of the foreign particles to be inspected becomes smaller than 0.25 μm in the longitudinal direction, the foreign particles cannot be visually discerned by the inspector, so the surface inspection device must be used. As the surface inspection device, a method of measuring the number of inspected objects by image processing after taking an image of the inspected object magnified through an optical system with an image pickup device such as a CCD camera and making it a digital image, and the surface of the inspected object There is a method of scanning the laser beam with a laser beam and capturing the scattered light in the reflected component with a photomultiplier tube for measurement, but in the inspection of the manufacturing process, the laser scattered light, which is more advantageous in terms of processing capacity, is used. Surface inspection equipment is commonly used.

[0006]

The detection limit of the surface inspection apparatus is the ratio of sensitivity to non-erasable noise, that is, S / N.
Determined by the ratio. No matter how high the sensitivity is, if the noise is large, the detection limit becomes large and the performance deteriorates.
As a surface inspection apparatus using laser scattered light, a surface inspection apparatus having a minimum measurable particle size of about 0.1 μm is currently on the market.

The S / N ratio changes under the influence of the surface condition of the semiconductor single crystal substrate to be inspected. For example, the surface roughness of the substrate surface, scattered light due to fine particles, defects, oxide film, etc. initially deposited increase the intensity of noise. Above all, the surface roughness generated on the entire substrate surface is S / N. Greatly affects the ratio. Since the minimum measurable particle size increases as the noise increases and the S / N ratio decreases, it is preferable to inspect the surface of the substrate under the condition where the S / N ratio is as large as possible.

The present invention has been made in view of the present situation where the S / N ratio fluctuates under the influence of the surface condition of the semiconductor single crystal substrate, and its purpose is to achieve the semiconductor under the condition that the S / N ratio is as large as possible. By inspecting the surface of the single crystal substrate,
An object of the present invention is to provide a foreign matter inspection device capable of stably measuring foreign matter near the minimum measurable particle size.

[0009]

In order to achieve the above object, the invention according to claim 1 is characterized in that the surface of a semiconductor single crystal substrate which is an object to be inspected An inspection apparatus for detecting foreign matter present on the surface of the object to be inspected by translating at right angles to the direction of linear scanning and detecting scattered light of the laser light, wherein the light source for the laser light is Scanning means for linearly scanning the surface of the object to be inspected with the laser beam, moving means for translating the object to be inspected at right angles to the direction of the linear scanning, and means for detecting scattered light of the laser light. And a rotating means for rotating the inspection object by a predetermined angle, and the inspection object is rotated by a predetermined angle before or after the laser light irradiation, and the laser is provided on the inspection object at each rotation angle position. Linearly scan the light to detect scattered light, A rotation angle position at which the intensity of turbulent light generation is minimized is set as a measurement reference angular position, and the inspection control means is provided to translate the object to be inspected at a right angle to the linear scanning direction at the measurement reference angular position. It is characterized by that.

Similarly, in order to achieve the above object, the invention according to claim 2 linearly scans the surface of the semiconductor single crystal substrate, which is the object to be inspected, with the direction of the linear scanning of the object to be inspected. And a laser light source, which is an inspection apparatus for detecting foreign matter present on the surface of the object to be inspected by detecting a scattered light of the laser light, which is moved in parallel with respect to the laser light. Scanning means for linearly scanning the surface of the object to be inspected, moving means for translating the object to be inspected at right angles to the direction of linear scanning, means for detecting scattered light of the laser light, and the object to be inspected. Rotating means for rotating the inspection body by a predetermined angle, and the inspection object is rotated by a predetermined angle with respect to the laser light whose irradiation direction is fixed to detect scattered light. The rotation angle position that becomes Set as, it is characterized in that it has an inspection control means for translating at right angles to the direction of linear scan the object to be inspected by the measurement reference angular position.

[0011]

The surface of the semiconductor single crystal substrate is selectively etched by washing, heat treatment or the like performed during the manufacturing process of the substrate to form minute irregularities having anisotropy on almost the entire surface. When the surface of the substrate is irradiated with laser light from different directions, anisotropy of minute irregularities causes the scattered light, which becomes noise, to become stronger and weaker.

For example, the following [Equation 1]

[0013]

[Equation 1]

Orientation in the plane direction indicated by
Plane orientation (1) having a flat (hereinafter, referred to as OF)
When the surface of the semiconductor single crystal substrate of (00) is irradiated with laser light from a plurality of different directions, scattered light generated due to minute unevenness is parallel to the OF as shown in FIG. Is the strongest when the angle of irradiation is 90 °, S /
The N ratio becomes the minimum. This is because, on the surface of the substrate, since the crystal interface of minute unevenness is generated along the plane perpendicular to OF, the direction perpendicular to the crystal interface of minute unevenness, that is, with respect to OF. When the laser light is scanned in parallel, the scattered light that becomes noise becomes the strongest.

On the other hand, in the case of a semiconductor single crystal substrate having a plane orientation of (111), the following [Equation 2]

[0016]

[Equation 2]

The intensity of the scattered light becomes the highest when the angle of laser light irradiation perpendicular to the OF of the plane orientation shown by is 0 ° or 180 °. The present invention utilizes this characteristic of minute unevenness having anisotropy.

[0018]

【Example】

[First Embodiment] First, a first embodiment of the present invention will be described with reference to FIGS. 1 is an explanatory view showing the configuration of the same embodiment, FIG. 2 is a flowchart showing the first half of the operation of the same embodiment, FIG. 3 is a flowchart showing the second half of the operation of the same embodiment, and FIG. 4 is of the same embodiment. It is a characteristic view of the setting operation of the measurement reference angle.

In this embodiment, as shown in FIG. 1, a transfer table 2 on which a semiconductor single crystal substrate 1 as an object to be inspected is placed is provided, and a rotary shaft 3 is attached to the center position of the transfer table 2. The rotary shaft 3 is connected to the rotary shaft of the motor 4, and the motor 4 is provided on the table 14. A drive circuit 12 is connected to the motor 4, and the drive table 12 drives the motor 4 so that the transfer table 2 can rotate about a rotation shaft 3. Further, a feed screw rod 5 is fixed to the table 14, a gear 6 which is rotated by the drive of a motor 7 is meshed with the feed screw rod 5, a drive circuit 13 is connected to the motor 7, and the drive circuit 13 drives the motor. The table 14 can be moved in the direction indicated by the arrow X in the figure by the feed screw rod 5 via the gear 6 by the drive of 7. Therefore, the substrate 1 can be rotated and moved in the arrow X direction.

On the other hand, a laser light source 8 for supplying laser light is provided, and the laser light from this laser light source 8 is supplied to the substrate 1.
A polygon mirror 9 that linearly scans the surface of the substrate and linearly scans it as shown by L in FIG. 1 and a drive circuit 11 for the polygon mirror 9 are provided, and the scattered light from the substrate 1 placed on the transfer table 2 is detected. A container 10 is provided. Further, the laser light source 8, the driving circuit 11, the detector 10, the driving circuit 12, and the driving circuit 1
A computer 15 for controlling the whole operation is connected to 3.

Then, in this embodiment, the substrate 1 is rotated by a predetermined unit angle by the motor 4, and the laser light is projected on the substrate 1 by the polygon mirror 9 at each rotational angle position as shown in FIG. 6 (a). The measurement reference angle setting means for performing linear scanning on the optical axis, detecting scattered light by the detector 10 in response to the linear scanning, and detecting the rotation angle at which the intensity of the scattered light is minimum and setting it as the measurement reference angle, It is provided in the computer 15. Further, the computer 15 drives the motor 7 at the measurement reference angular position to move the substrate 1 in parallel at predetermined intervals, and captures and stores the detection output of the detector 10 at each parallel movement position. There is provided inspection control means for obtaining information on surface foreign matter on the substrate 1 by performing calculation based on the detected output. In addition, 20 is OF in FIG.

The operation of this embodiment having such a configuration will be described with reference to FIGS. In step S1 of FIG.
When it is determined and confirmed that the OF 20 of the substrate 1 is set to match the reference position of the transfer table 2, the computer 15
The measurement reference angle setting means is activated, and the measurement reference angle setting operation of steps S2 to S9 is started.

First, in step S2, the computer 1
The laser light from the laser light source 8 is applied to the surface of the substrate 1 at the measurement start angular position by the polygon mirror 9 by the drive circuit 11 which operates according to the command No. 5, and the polygon mirror 9 rotates to generate the laser light as shown in FIG. 1L. The line is scanned. Then, the scattered light from the surface of the substrate 1 of the detector 10 accompanying this linear scanning is counted, and the count value obtained in step S2 is associated with the rotation angle of the substrate 1, and the computer 15 in step S3. Stored in memory.

Next, the motor 4 is rotated in the clockwise direction by a preset unit angle (for example, 15 °) by the drive circuit 12 operated by the command of the computer 15,
Since the transfer table 2 is rotated by the rotation of the motor 4 via the rotation shaft 3, the substrate 1 is set at a position rotated by a unit angle, and it is determined in step S4 whether the substrate 1 is rotated by a unit angle. To be done. If it is determined in step S4 that the substrate 1 has rotated by a unit angle, the process proceeds to step S5, where the drive circuit 11 operated by the command of the computer 15 causes the laser light from the laser light source 8 to rotate by a unit angle. The surface of the substrate 1 located at the position is irradiated and linearly scanned in parallel with FIG. 1L by the rotation of the polygon mirror 9. And
The scattered light from the surface of the substrate 1 detected by the detector 10 is counted in accordance with this linear scanning, and the count value obtained in step S5 is associated with the rotation angle of the substrate 1 in step S6. It is stored in 15 memories.

Further, in step S7, it is determined whether the rotation angle of the substrate 1 has reached 180 °. If the rotation angle of the substrate 1 has not reached 180 °, step S7 is performed.
Returning to step 4, the processes of steps S4 to S6 are repeated. Then, when it is determined in step S7 that the rotation angle of the substrate 1 has reached 180 °, the process proceeds to step S8, and the computer 15 causes the minimum count value of the scattered light count values stored in the memory. Is detected, the process proceeds to step S9, and the rotation angle corresponding to the detected minimum count value is set as the measurement reference angle.

In this way, in this embodiment, the rotation angle that allows the surface inspection of the substrate 1 is detected under the condition that the scattered light from the surface is minimum and the S / N ratio is maximum. The rotation angle is set as a measurement reference angle for measuring the surface foreign matter.

FIG. 4 is a characteristic diagram of the measurement reference angle setting operation by the measurement reference angle setting means of the computer 15. As described above, the substrate 1 counted by the detector 10 is rotated by the unit angle Δθ. The levels of scattered light P (0) ... P (n + 1) ... P (r + 1) from the surface of the are stored in the memory of the computer 15 and correspond to the lowest level of scattered light from these count values. The rotation angle θm is set as the measurement reference angle.

Returning to the flow chart of FIG. 2, when the measurement reference angle θm is set by the measurement reference angle setting means of the computer 15 in step S9, the computer 1
The drive circuit 12 operates according to the command of 5, and the transfer table 2 rotates via the rotation shaft 3 by the motor 4 that is driven,
The substrate 1 is rotated and set to the measurement reference angle θm position. Next, in step S10 of the flowchart of FIG. 3, when it is determined that the substrate 1 has been pivotally set to the measurement reference angle θm, the process proceeds to step S11, and the drive circuit 13 operates according to a command from the computer 15. Then
The driven motor 7 translates the table 14 through the gear 6 and the screw rod 5 at right angles to the linear scanning direction at predetermined intervals.

Then, in step S12, the laser light from the laser light source 8 is applied to the surface of the substrate 1 set at the measurement reference angle θm by the drive circuit 11 operated by the command of the computer 15 at each parallel movement position. Then, the surface of the substrate 1 is linearly scanned by the rotation of the polygon mirror 9. Then, step S1
At 3, the scattered light from the surface of the substrate 1 of the detector 10 accompanying this linear scanning is counted, and the count value obtained at step S13 is stored in the memory of the computer 15 at step S14.

Then, in step S15, it is determined whether or not the linear scanning of the laser light at all the parallel movement positions and the detection and count value of the scattered light corresponding to the linear scanning are all stored in the memory of the computer 15, and the storage is completed. If not, the process returns to step S11 and the same process is repeated. When it is determined in step S15 that the detection of scattered light corresponding to the linear scanning of the laser light and the storage of the count value in the memory of the computer 15 are completed, the process proceeds to step S16 and the computer 15 stores the count value in the memory. Based on the scattered light count value, foreign matter information such as the scattering cross section is calculated, and the foreign matter on the surface of the substrate 1 is inspected.

Thus, according to the first embodiment,
The measurement reference angle setting means of the computer 15 detects and sets a rotation angle at which the surface of the substrate 1 can be inspected under the condition that the scattered light from the surface that becomes noise is the lowest and the S / N ratio is the highest. At this measurement reference angular position, the substrate 1
It is possible to inspect the surface foreign matter with high accuracy with a high S / N ratio.

In order to compare the measurement stability, the same semiconductor single crystal substrate was prepared by randomly setting the orientation of OF using the surface foreign matter inspection apparatus according to the first embodiment and the conventional surface foreign matter inspection apparatus. The number of bright spots above is 0.16 μm
The above items were repeatedly measured 20 times, and the results are shown in [Table 1] below. As the semiconductor single crystal substrate, an epitaxially grown n / n + type substrate having a diameter of 4 inches and an axial orientation of <111> was used.

As a result of the comparative experiment, when the surface foreign matter inspection apparatus according to the first embodiment is used, compared with the conventional inspection apparatus,
It was found that the value of standard deviation σ was significantly reduced and the average value of the number of bright spots was lowered. This is because, when the surface foreign matter inspection apparatus according to the first embodiment is used, the scattered light from the surface that causes noise is measured in the minimum state, so that the number of bright spots counted as noise is the smallest and stable. Because they are doing it.

[0034]

[Table 1]

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flow chart showing the operation of the embodiment. This embodiment basically has the same configuration as the first embodiment described with reference to FIG. In particular, in this embodiment, the object to be inspected is rotated by a predetermined angle with respect to the laser light whose irradiation direction is fixed to detect scattered light, and the scattered light is detected in an arc-shaped detection range as shown in FIG. 6B. Then, the rotation angle position where the intensity of scattered light is minimized is calculated, and the rotation angle position is set as the measurement reference angle position.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. When it is determined in step S21 of FIG. 5 that the OF20 of the substrate 1 has been set in conformity with the reference position of the transfer table 2, the measurement reference angle setting means of the computer 15 operates, and steps S22 to S26. The measurement reference angle setting operation of is started.

First, in step S22, the polygon mirror 9 is rotated by the drive circuit 11 operated by the command of the computer 15 so that the laser light from the laser light source 8 irradiates a predetermined position on the substrate 1. Fix the direction of light irradiation.

Then, in step S23, the computer 1
The motor 4 is rotated in the clockwise direction by a preset angle (for example, 180 °) by the drive circuit 12 that operates according to the command of 5, and the transfer table 2 is rotated by the rotation of the motor 4 via the rotation shaft 3. To do. At this time, the laser light from the laser light source 8 scans the surface of the substrate 1 which is rotating by a predetermined angle so as to draw an arc as shown in FIG. 6B. Then, the scattered light from the surface of the substrate 1 detected by the detector 10 is counted in accordance with this scanning, the obtained count value is associated with the rotation angle of the substrate 1, and the memory of the computer 15 is stored in step S24. Stored in.

Further, when the rotation angle of the substrate 1 reaches 180 °, the process proceeds to step S25, and the computer 15 detects the minimum count value of the scattered light count values stored in the memory, and step S26. Then, the rotation angle corresponding to the detected minimum count value is set as the measurement reference angle. Then, as in the first embodiment, the surface inspection of the substrate 1 is performed by the steps after step S10.

In order to see the stability of the measurement by the surface foreign matter inspection apparatus of the second embodiment, a semiconductor single crystal substrate of an n / n ⁺ type having a diameter of 4 inches and an axial orientation of <111> was epitaxially grown. An experiment similar to that of the first embodiment was conducted using the same thing. As a result of the experiment, the average number of bright spots was 13.7 pieces / substrate and the standard deviation was 6.8 pieces / substrate in 20 repeated measurements, which was more stable than the conventional inspection device.

[0041]

According to the present invention, the rotation angle at which the intensity of scattered light becomes the minimum is detected in advance and set as the measurement reference angle, and the surface inspection of the semiconductor single crystal substrate is performed under the condition that the S / N ratio is as large as possible. Therefore, it becomes possible to stably measure the foreign matter in the vicinity of the minimum measurable particle size.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a flowchart showing the first half of the operation of the embodiment.

FIG. 3 is a flowchart showing a latter half of the operation of the embodiment.

FIG. 4 is a characteristic diagram of a setting operation of a measurement reference angle in the same example.

FIG. 5 is a flowchart showing the operation of the second exemplary embodiment of the present invention.

FIG. 6A is a diagram showing a linear scanning pattern for setting a measurement reference angle in the first embodiment of the present invention.
(B) is a figure which shows the circular-arc scanning pattern for setting a measurement reference angle in the 2nd Example of this invention.

FIG. 7 is a diagram showing a change in intensity of scattered light when measurement is performed while changing a scanning angle of laser light.

[Explanation of symbols]

 1 substrate 2 transfer table 4, 7 motor 8 laser light source 9 polygon mirror 10 detector 14 table 15 computer

Claims (2)

[Claims] 1. While linearly scanning a surface of a semiconductor single crystal substrate, which is an object to be inspected, with the laser beam, the object to be inspected is moved in parallel at a right angle to the direction of the linear scanning, and scattered light of the laser beam is scattered. An inspection apparatus for detecting foreign matter existing on the surface of the inspection object by detecting, a light source of the laser light, a scanning means for linearly scanning the laser light on the surface of the inspection object, Moving means for moving the inspection object parallel to the direction of the linear scanning at right angles; means for detecting scattered light of the laser light; rotating means for rotating the inspection object by a predetermined angle; The object to be inspected is rotated by a predetermined angle before or after the laser light irradiation, and the scattered light is detected by linearly scanning the laser light on the object to be inspected at each rotation angle position, and the generated intensity of the scattered light is the lowest. The rotation angle position is And the inspection control means for translating the object to be inspected at the measurement reference angle position at a right angle to the direction of the linear scanning. 2. The surface of a semiconductor single crystal substrate, which is an object to be inspected, is linearly scanned with laser light, and the object to be inspected is moved in parallel at a right angle to the direction of the linear scanning, so that scattered light of the laser light is generated. An inspection apparatus for detecting foreign matter existing on the surface of the inspection object by detecting, a light source of the laser light, a scanning means for linearly scanning the laser light on the surface of the inspection object, Moving means for moving the inspection object parallel to the direction of the linear scanning at right angles, means for detecting scattered light of the laser light, rotation means for rotating the inspection object by a predetermined angle, and irradiation The object to be inspected is rotated by a predetermined angle with respect to the laser light whose direction is fixed to detect scattered light, and the rotational angle position at which the intensity of scattered light is minimized is set as the measurement reference angular position. Straight line to be inspected at the measurement reference angle position A foreign matter inspection apparatus, comprising: an inspection control unit that translates at right angles to a scanning direction.