JPH0363817B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wafer foreign matter inspection device that automatically detects foreign matter on the surface of a wafer for LSI or the like.

[Prior Art] There is a wafer foreign matter inspection device that detects foreign matter on the surface of a wafer while spirally scanning the surface of the wafer placed on a rotation stage.

Such conventional wafer foreign object inspection equipment moves a rotary stage in a specific direction while rotating.
The wafer on the rotation stage is scanned spirally by the detection system to detect a foreign object, and when a foreign object is detected, the rotational direction position and specific direction position of the rotation stage at the time of detection are read as the foreign object position. Store in memory. In addition, the contour of the wafer is detected in the same way as foreign objects, a contour image of the wafer is drawn as a series of foreign objects, the detected foreign objects are plotted on the wafer contour image to create a foreign object map, and the foreign object map is plotted on an X-Y plot. Print out with .

[Problem to be solved] As described above, in the conventional wafer foreign object inspection device, the rotational position of the detected foreign object is the rotational direction position of the rotation stage, but the mounting angle of the wafer with respect to the rotation stage is not constant. However, there are variations in the offset angle between the wafer and the rotation stage. In other words, the rotational position of a foreign object detected for a certain wafer has meaning only on the foreign object map of that wafer, not its actual position on the wafer. Therefore, the position information of the foreign object is used as data for data processing. It cannot be used as is. For example, it is impossible to directly obtain statistics such as the distribution of foreign objects on a large number of wafers from the position information of detected foreign objects. I need.

[Object of the Invention] The present invention was made in view of such problems in the prior art, and its purpose is to provide a method for obtaining foreign object position information on a wafer that is not affected by variations in the mounting angle of the wafer on a rotation stage. The purpose is to provide inspection equipment.

[Means for Solving the Problems] In order to achieve such an object, according to the present invention, the surface of a wafer placed on a rotation stage is scanned in a spiral manner to remove foreign particles on the surface of the wafer. A wafer foreign object inspection apparatus for detecting a foreign object, comprising means for detecting an offset angle of a wafer on the rotation stage with respect to the rotation stage, and means for correcting the rotational direction position of the detected foreign object in accordance with the offset angle detected by the means. and is provided.

[Operation] By correcting the position of the foreign object in the rotational direction according to the offset angle of the wafer, it is possible to obtain position information of the foreign object from which the influence of variations in the mounting angle of the wafer has been removed.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing a simplified configuration of the optical system and other parts of a wafer foreign matter inspection apparatus according to the present invention. In this figure, 10 is an X stage supported by a base 12 so as to be slidable in the X direction.
This X stage 10 includes a stepping motor 1.
A screw 16 directly connected to the rotating shaft of 4 is screwed together, and by operating the stepping motor 14, the X stage 10 can be moved forward and backward in the X direction. 18 is a linear encoder that generates a code signal corresponding to the position x of the X stage 10 in the X direction.

A Z stage 20 is attached to the X stage 10 so as to be movable in the Z direction. Its transportation means are omitted in the figure. The Z stage 20 rotatably supports a rotation stage 22 on which a wafer 30 as an object to be inspected is placed. here,
As the wafer 30, a wafer with a blank film, a mirror wafer, or a wafer with a pattern can be set and inspected.

A DC motor 24 is connected to this rotation stage 22, and is thereby configured to be rotationally driven in a specific direction. This DC motor 24
has a built-in rotary encoder that outputs a code signal corresponding to the rotational direction position θ of the rotation stage 22.

Note that the wafer 30 is positioned and fixed on the rotation stage 22 by negative pressure suction, but means for this purpose are omitted in the figure.

This wafer foreign matter inspection device automatically inspects foreign matter on the wafer 30 using polarized laser light.
Polarized laser light is irradiated. For this purpose, S-polarized laser oscillators 36 and 38 are provided. Each S
The polarized laser oscillators 36 and 38 generate S-polarized laser light of a certain wavelength, for example, the wavelength is 8300.
This is an Angstrom semiconductor laser oscillator.

The S-polarized laser beam is directed toward the wafer 30 from the Y direction.
It is irradiated onto the upper surface of the body at an irradiation angle φ of about 2 degrees. Since the irradiation angle is thus small, when a beam of S-polarized laser light having a circular cross section is irradiated, the spot on the wafer surface is elongated, making it impossible to obtain a sufficient irradiation density. Therefore, S-polarized laser oscillator 3
Cylindrical lens 44, 4 in front of 6, 38
6 is arranged, and the S-polarized laser beam with a substantially circular cross section emitted from the S-polarized laser oscillators 36 and 38 is
The wafer surface is irradiated after narrowing the beam down to a beam with a flat cross-sectional shape.

Here, in the case of a wafer with a blank film without a pattern (or a mirror wafer), the S-polarized laser light is
If there is no foreign matter within the irradiation spot, the light will be reflected almost specularly and will not be reflected in the Z direction, but if there is a foreign matter, it will be reflected diffusely and also reflected in the Z direction.

On the other hand, in the case of a patterned wafer, the reflected laser light of the S-polarized laser beam irradiated onto the wafer surface is also reflected in the Z direction if a pattern exists within the irradiation spot, but the surface of the pattern is slightly Since it is visually smooth, the reflected laser light contains almost only the S-polarized component. On the other hand, since the surface of a foreign object generally has minute irregularities, if a foreign object exists within the irradiation spot, the irradiated S-polarized laser light will be scattered and the polarization direction will change, and the reflected laser light will have
In addition to the S-polarized light component, a considerable amount of the P-polarized light component is included.

Focusing on this phenomenon, this wafer foreign matter inspection system detects the presence or absence of foreign matter based on the level of the P-polarized light component contained in the laser beam reflected from the wafer surface in the Z direction in the case of patterned wafers. Detect the size of foreign objects.

On the other hand, in the case of wafers with blank films (including mirror-finished wafers), in order to increase detection sensitivity,
The presence or absence and size of a foreign object are detected based on the levels of the S-polarized reflected laser beam and the P-polarized reflected laser beam in the Z direction.

Referring again to FIG. The reflected laser light from the wafer surface enters an optical system common to a detection system 50 for detecting foreign matter according to the above principle and a microscope 52 for visual observation of the wafer. That is, the reflected laser light reaches the 45-degree prism 60 via the objective lens 54, the half mirror 56, and the prism 58.

A lamp 70 is also provided for visual observation. Visible light emitted from this lamp 70 causes
The wafer surface is illuminated via the half mirror 56 and the objective lens 54.

The visible reflected light that has entered the microscope 52 side via the prism 60 passes through the 60-degree prism 62, the field lens 64, and the relay lens 66 in this order, and enters the eyepiece lens 68. Therefore, the eyepiece 68 allows the wafer 30 to be visually observed at sufficiently high magnification. In this case, the range of the S-polarized laser beam spot on the wafer surface is located at the center of the field of view. Further, the wafer 30 can also be observed at low magnification through the prism 58.

The reflected laser light that has entered the detection system side via the prism 60 passes through an aperture 74 provided in a slit 72 and is sent to the photomultiplier 90.

Here, if the wafer 30 is a patterned wafer, the S polarization cut filter 86 (polarizing plate) is moved to the position indicated by reference numeral 86', so that only the P polarization component of the reflected laser beam is extracted and sent to the photomultiplier. 90. wafer 30
When the wafer is a wafer with a blank film (or a mirror-finished wafer), the S-polarization cut filter 86 is moved to the position shown by the solid line, so that both the S-polarization component and the P-polarization component of the reflected laser light enter the photomultiplier 90. As will be described later, the presence or absence of a foreign object within the field of view of the aperture 74 on the wafer surface and the particle size of the foreign object are determined based on the level of the output signal (detection signal) of the photomultiplier 90.

87 is a solenoid for moving the S polarization cut filter 86.

Here, the foreign matter inspection is performed while rotating the wafer and feeding it in the X direction (radial direction) as described above. According to such movement of the wafer 30, the third
As shown in the figure, a spot 30 of S-polarized laser light
A moves spirally on the upper surface of the wafer 30 from the outside toward the center. The detection system 50 and the microscope 52 are stationary, and the field of view of the aperture 74 is always contained within the spot 30A and moves to follow the spot 30A. That is, the wafer surface is inspected while being spirally scanned.

Here, the irradiation angle φ will be explained. In conventional wafer foreign matter inspection equipment, when inspecting foreign matter on a wafer whose surface has a blank film without a pattern such as a photoresist film or an aluminum evaporated film, a light beam is applied to the wafer at a fairly large irradiation angle, for example 30 degrees. It is designed to irradiate the surface.

According to the inventor's research, the background noise of the detection signal in such conventional devices includes:
It includes not only noise components determined by the state of the wafer surface (the surface of the blank film), but also noise components related to the state inside the blank film and noise components related to the state of the wafer base surface under the blank film. There is. Due to the principle of using reflected light from the wafer surface, it is impossible to completely remove the initial noise component, and its influence is not fatal. However, the latter two noise components are affected by the internal state of the wafer,
This should be removed as it directly causes false positives.

According to the inventor's research, in conventional equipment, because the beam irradiation angle is large, a portion of the light beam incident on the wafer surface penetrates into the interior of the blank film, is reflected on the wafer base surface, and causes the blank film to be exposed again. It was found that the above-mentioned undesirable noise component was generated because the light passed through the wafer surface and entered the photoelectric element.

Therefore, in this embodiment, the irradiation angle of the light beam is selected to be sufficiently small as described above so that the light beam is substantially totally reflected on the wafer surface, thereby preventing the light beam from penetrating inside the wafer. .

Referring again to FIG. A capacitance displacement meter 53 is provided near the objective lens 54 and facing the wafer surface. This capacitance displacement meter 53 is provided as a sensor for detecting the orientation flat portion of the wafer 30, and during the wafer rotation for offset angle detection, which will be described later, the capacitance displacement meter 53 is provided as a sensor for detecting the orientation flat portion of the wafer 30. The capacitance displacement meter 53 is arranged so that the inner portion thereof passes directly under the capacitance displacement meter.

Next, the signal processing and control system of this wafer foreign matter inspection apparatus will be explained with reference to FIG.

The detection signal output from the photomultiplier 90 is amplified by an amplifier 100 and then input to a level comparison circuit 102.

Here, there is a relationship as shown in FIG. 4 between the particle size of the foreign matter on the wafer and the level of the detection signal. In this figure, L ₁ , L ₂ , and L ₃ are threshold values of the level comparison circuit 102.

The level comparison circuit 102 compares the level of the detection signal with each threshold value, and outputs a binary code indicating the result of comparison with each threshold value. For example, if the detection signal level is less than the threshold L ₁ , it will output (000) ₂ , and if the detection signal level is more than the threshold L ₂ and less than the threshold L ₃ , it will output (011) ₂ , and the detection signal level will be the threshold. If L is ₃ or more, outputs (111) ₂ .

The output code of the level comparison circuit 102 is input to an interface circuit 108 that interfaces with the data processing system 104.

The output signal of the capacitance displacement meter 53 is input to the level comparison circuit 103 and compared with a specific threshold value.
The output signal of this level comparison circuit is input to the interface circuit 108.

Further, the interface circuit 108 receives signals (binary code) from the rotary encoder and the linear encoder that indicate information about the rotational direction position θ and the X-direction (radial direction) position x at each point in time. Input via .

Each input code to the interface circuit 108 is sent to the interface circuit 10 at regular intervals.
The data is taken into a certain register inside the 8 and is temporarily held there.

Furthermore, inside the interface circuit 108, the motor 14,
There are also registers in which control information for 24 and solenoid 87 is set. According to the control information set in this register, the motor controller 116 controls the drive of the motors 14 and 24, and the solenoid driver 117 controls the solenoid 87.
drive control is performed.

The data processing system 104 includes a microprocessor 120, ROM 122, RAM 124, floppy disk device 126, and X-Y plotter 12.
7, a CRT display device 128, a keyboard 130, etc. 132 is a system bus, which connects the microprocessor 120, ROM 122,
RAM 124, the interface circuit 108
are directly connected.

The keyboard 130 is used by an operator to input various commands and data, and is connected to the system bus 132 via an interface circuit 134. The floppy disk device 126 is
It stores the operating system, various processing programs, test result data, etc.
It is connected to the system bus 132 via a floppy disk controller 136.

When this wafer foreign matter inspection device is started, the operating system is transferred from the floppy disk device 126 to the system area 124A of the RAM 124.
loaded into. After that, one or more necessary processing programs among the various processing programs stored in the floppy disk device 126 are transferred to the RAM.
124 program area 124B,
It is executed by microprocessor 120. Data that is being processed is temporarily stored in the work area of the RAM 124. The processing result data is finally transferred to and stored in the floppy disk device 126. The ROM 122 stores dot patterns such as letters, numbers, and symbols.

The CRT display device 128 is used to display various messages for interaction with the operator, a foreign object map, and other data, and the display data is stored in the video RAM 138.
The bit map is expanded. 140 is a video controller, which writes data to the video RAM 138;
In addition to control such as reading, it also generates a video signal according to the dot pattern. The video controller 140 is connected to the system bus 132 via an interface circuit 142.

The X-Y plotter 127 is used to print out foreign matter maps and the like, and is connected to the system bus 132 via a plotter controller 137.

Next, automatic foreign matter inspection processing will be explained with reference to the flowchart shown in FIG.

When the operator commands the start of inspection from the keyboard 130 with the wafer 30 set on the rotation stage 22, the floppy disk device 126
The automatic inspection processing program loaded into the program area 124B of the RAM 124 starts running.

First, the microphone processor 120 secures a storage area (see FIG. 2) on the RAM 120 for a table, a counter, a test data buffer, etc., which will be described later (step 200).

A conceptual diagram of the above table (created in the table area 124D) is shown in FIG. This table 1
Each of the 50 entries includes information on the foreign object number (in the order in which it was detected), the position of the foreign object, its type or nature (investigated by visual observation), and size.

Next, the microprocessor 120 sets motor control information for positioning the rotary stage 22 at the initial position (x=0, θ=0) in the internal register of the interface circuit 108 (step 205). According to this motor control information, the motor controller 116 controls the motors 14 and 24 to move each stage to its initial position.

The microprocessor 120 generates a dot pattern of the wafer contour image and sequentially transfers it to the video controller 140 through the interface circuit 142 (step 210). The video controller 140 converts the transferred dot pattern into a video
The contents of the video RAM 138 are sequentially written into the RAM 138, and in parallel, the contents of the video RAM 138 are sequentially read out and converted into video signals, which are then supplied to the CRT video display device 128. Thus, a wafer contour image with the orientation flat facing downward is displayed on the screen of the CRT display device 128.

The microprocessor 120 then controls the motor controller 11 through the interface circuit 108.
6 to start scanning (step 215). Upon receiving this instruction, the motor controller 116 drives the motors 14 and 24 to perform the above-described helical scan at a constant speed. The microprocessor 120 also processes the P counter 1 on the RAM 124.
24K is set to 1 (step 218).

After a certain period of time has elapsed from the start of scanning, the microprocessor 120 reads the contents of a specific register in the interface circuit 108, that is, the code at positions x and θ, and the level comparison circuit 10 at certain time intervals.
2 and the level comparison result bit of the level comparison circuit 103 are taken in and written to the input buffer 124C on the RAM 124 (step 220).

During one rotation of the wafer 30, the output signal level of the capacitance displacement meter 53 changes as shown in the waveform diagram of FIG. 7, for example. That is, when the outline of the wafer 30 exists directly below the capacitance displacement meter 53, the output level is higher than the threshold L of the level comparison circuit 103, but when the orientation flat portion of the wafer 30 passes through the capacitance displacement meter 53, the output level is higher than the threshold L of the level comparison circuit 103. The output signal level will drop significantly. The level comparison circuit 103 outputs a logic "1" when the level difference between the output signal of the capacitance displacement meter 53 and the threshold L is within a predetermined range, that is, when the end of the orientation flat passes through the capacitance displacement meter 53. Outputs a match signal.

Now, the microprocessor 120 determines whether the fetched comparison result bit of the level comparison circuit 103 is "1" (step 225). If the judgment result is NO, the process returns to step 220 and waits for the next register read timing.
If YES, it is determined whether the value of the P counter 124K is 1 (step 230). If the determination result is NO, the microprocessor 120 writes information on the rotational direction position θ stored in the input buffer 124C to the offset angle register 124J (step 235), and decrements the P counter 124K by 1 (step 235). 240), return to step 220.

If the determination result in step 230 is YES, the microprocessor 120 executes a specific calculation using the rotational direction position θ stored in the input buffer 124 and the rotational direction position θ stored in the offset angle register 124J. By doing so, the offset angle is determined and written into the offset angle register 124J (step 245).

This offset angle will be explained with reference to FIG. The end of the orientation flat of the wafer 30 passes directly under the capacitance displacement meter 53, and the level comparison circuit 10
The position in the rotational direction when the matching signal is output from 3 is θ ₁ , θ ₂
shall be. The center point of the orientation flat is the capacitance displacement meter 10
The rotational direction position θ ₃ when passing directly below θ 3 is an intermediate value between θ ₁ and θ ₂ , and is obtained in step 245 . The position of the capacitance displacement meter 53 is determined so that if the offset angle with respect to the rotation stage 22 is 0, θ ₃ is 0. Therefore, θ ₃
is the offset angle itself.

When the offset angle detection process as described above is completed, the process proceeds to step 260 and subsequent steps for actual foreign matter inspection process.

First, the microprocessor 120 provides motor control information to the motor controller 116 via the interface circuit 108 in order to rapidly move the scanning point to the inspection starting position.
260). The motor controller 116 drives the stepping motor 14 at high speed until it reaches the inspection start position.
After the stage 10 is rapidly moved and reaches the inspection start position, the stepping motor 14 is driven to perform normal X-direction feeding for scanning.

After this positioning operation, microprocessor 1
20 takes in the positions θ, x and the comparison result code (L code) of the level comparison circuit 102 from the interface circuit 108, and writes them into the input buffer 124C (step 265).

The microprocessor 120 compares the read X-direction position x with the inspection end position to determine the end of scanning (step 270). The result of this judgment is NO
(during inspection), microprocessor 120
performs a zero determination on the loaded L code (step 275). If L=000, no foreign matter exists at that scanning position. If L≠000, a foreign substance exists.

If the judgment result in step 275 is YES, proceed to step
Return to 265. If the determination result in step 275 is NO, the microprocessor 120 calculates the rotation direction position θ stored in the input buffer 124C.
The offset angle stored in the offset angle register 124J is subtracted to obtain the rotational direction position corrected by the offset angle, and the corrected rotational direction position θ' is returned to the input buffer 124C (step 280).

Next, the microprocessor 120 receives the position information (x, θ') stored in the input buffer 124C.
and the positional information of other detected foreign objects stored in the table 150 (the position in the rotational direction has been corrected) (step 285).

If a match is found in this positional comparison, the current foreign object can be considered to be the same as another previously detected foreign object, and the process returns to step 265.

If the position comparison does not match, it can be assumed that a new foreign object has been detected. Therefore, microprocessor 1
20 increments the N counter 124E on the RAM 124 by 1 (step 290). Then, the position information and L code (size information) of the foreign object in the input buffer 124C are written into the Nth entry of the table 150 (step
295).

Further, the microprocessor 120 reads dot pattern data corresponding to the size information (L code) of the foreign object from the ROM 122, transfers it to the video controller 140 together with the address information of the video RAM 138 corresponding to the position information of the foreign object, and It is written into RAM 138 (step 297). Through this process, the detected foreign object is displayed on the screen of the display device 128 as a pattern unique to its size. wafer 30
The same process is repeated until the scanning is completed.

As described above, the wafer contour image is displayed in a fixed orientation with the orientation flat facing downward, and this orientation corresponds to the case where the offset angle is zero. On the other hand, the rotational position of the foreign object is corrected according to the offset angle so that it corresponds to the actual position on the wafer. Therefore, a foreign matter map with a fixed orientation representing the actual distribution of foreign matter on the wafer is displayed on the screen.

When it is determined in step 270 that scanning has ended, master 120 sends a scanning stop instruction to motor controller 116 through interface circuit 108 (step 300). In response to this instruction,
Motor controller 116 stops driving motors 14 and 24.

Next, the microprocessor 120 processes table 1
Total number of foreign objects with L code 1 ₂ referring to 50
TL ₁ , the total number of foreign objects with a code L of ₃₂ TL ₂ , and the total number of foreign objects with a code L of ₇₂ TL ₃ are calculated, and the total number of foreign objects data is stored in the register 124 on the RAM 124.
Write to F, 124G, 124H (step
305). Then, the stored contents of the table 150 and the foreign matter total data are transferred to the floppy disk device 126 with the wafer number added thereto and stored therein (step 310).

Although the details will not be explained, the foreign material inspection result data is read from the floppy disk device 126, transferred to the plotter controller 137, and the foreign material map, foreign material total data, wafer number, etc.
The Y plotter 127 can be used to print out the image.

In addition, the automatically inspected wafer is transferred to the rotating stage 2.
2 and table 15 for that wafer.
0 from floppy disk device 126 to RAM1
24, visually observe each foreign substance on the wafer, register the observation results in the table 150, and store the table 150 in the floppy disk device 126 when the visual observation is completed.

Although one embodiment of the present invention has been described above, the present invention is not limited thereto, and can be implemented with appropriate modifications.

For example, the sensor for detecting the orientation flat of the wafer is not limited to a capacitance displacement meter, but an optical sensor or the like may also be used.

The means for determining the offset angle from the output signal of the orientation flat detection sensor and the means for correcting the position of the foreign object according to the offset angle may be configured by hardware, and such hardware can be constructed by a person skilled in the art. This can be easily realized based on the explanation of the above embodiments.

Instead of a photomultiplier, other suitable photoelectric elements can be used.

The flow of the inspection process described above is just an example.
Needless to say, it can be changed as appropriate.

Furthermore, the present invention is also applicable to similar wafer foreign matter inspection apparatuses that utilize light beams other than polarized laser light.

[Effects of the Invention] As described above, according to the present invention, in a wafer foreign matter inspection apparatus that detects foreign matter on the surface of a wafer placed on a rotation stage while spirally scanning the surface of the wafer, an offset angle detection means for detecting an offset angle of the wafer on the rotation stage with respect to the rotation stage; and a position correction means for correcting the rotational direction position of the detected foreign object according to the offset angle detected by the offset angle detection means. According to the related invention, there is further provided a means for generating a foreign matter map by plotting the foreign matter corrected by the position correction means on a wafer contour image in a fixed orientation, and a foreign matter map generated by the means. Since a means for outputting the information is provided, it is possible to obtain foreign object position information that eliminates the influence of variations in the mounting angle of the wafer.
Regardless of variations in the mounting angle of the wafer, information on the position of foreign objects can be managed or processed all at once, and effects such as easy comparison of foreign object maps with standard wafers or other wafers can be obtained. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the optical system etc. of the wafer foreign matter inspection apparatus according to the present invention, FIG. 2 is a schematic block diagram showing the signal processing and control system of the wafer foreign matter inspection apparatus, and FIG. 3 is an explanatory diagram of wafer surface scanning. , Fig. 4 is a graph showing the relationship between the particle size of foreign particles and the output signal of the photomultiplier, and the relationship with the threshold value for level comparison, Fig. 5 is a conceptual diagram of a table related to inspection processing, and Fig. 6 is The flowchart of the inspection process, FIG. 7 is a waveform diagram of the output signal of the capacitance displacement meter. 10...X stage, 14...stepping motor, 22...rotation stage, 24...DC motor, 30... ...Wafer, 36, 38...S-polarized laser oscillator, 50...Detection system, 52...Microscope, 5
3...Capacitance displacement meter, 72...Slit, 86
... S polarization cut filter, 90 ... Photomultiplier, 100 ... Amplifier, 102, 103 ...
... Level comparison circuit, 104 ... Data processing system, 108 ... Interface circuit, 116 ...
... Motor controller, 117 ... Solenoid driver, 120 ... Microprocessor, 122
... ROM, 124 ... RAM, 126 ... Floppy disk device, 127 ... X-Y plotter, 128 ... CRT display device, 130
...Keyboard, 138 ...Video RAM, 15
0...Table.

Claims (1)

[Scope of Claims] 1. In a wafer foreign matter inspection apparatus that detects foreign matter on the surface of a wafer placed on a rotation stage while scanning the surface of the wafer in a spiral manner, the rotation stage of the wafer placed on the rotation stage 1. A wafer foreign matter inspection apparatus comprising: means for detecting an offset angle relative to a wafer; and means for correcting a rotational direction position of a detected foreign matter according to the offset angle detected by the means. 2. The means for detecting the offset angle includes a sensor for detecting the orientation flat portion of the wafer on the rotation stage, a means for comparing the level of an output signal of the sensor with a predetermined threshold value, and a coincidence signal output from the means. The wafer foreign object according to claim 1, further comprising means for reading the position in the rotational direction of the rotary stage when the wafer is detected, and means for determining the offset angle from the position in the rotational direction read by the means. Inspection equipment. 3. The wafer foreign matter inspection apparatus according to claim 2, wherein the sensor is a capacitance displacement meter provided at a predetermined position facing the rotation stage.