JP2876507B2 - Wafer foreign matter inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer foreign matter inspection apparatus, and more particularly to a wafer foreign matter inspection apparatus capable of detecting an outer periphery of a wafer and easily setting a center position of the wafer to a reference position of a wafer mounting table. The present invention relates to a foreign matter inspection device.

[0002]

2. Description of the Related Art IC chips are projected and exposed on a wafer of silicon or the like by a mask using a mask, and are subjected to predetermined processing and inspection. In each processing step of the IC manufacturing process, each IC chip on the wafer must be correctly positioned. For this purpose, the orientation flat OF (orientation flat) provided on the wafer and the center position of the wafer are determined by the wafer of each processing apparatus. It is necessary to place or match the reference position of the placement table. Further, in the wafer foreign matter inspection apparatus, the foreign matter coordinates are usually taken as R and θ coordinates with respect to the center of the wafer, and the foreign matter detected by performing the spiral scan is displayed. is there.

In order to make the center position of the wafer coincide with the center of the wafer mounting table or to locate the center of the wafer, the outer periphery of the wafer is usually used. FIG. 4 is a schematic view of an apparatus for detecting the outer peripheral position of a wafer of this type proposed by the present applicant (Japanese Patent Laid-Open No. 2-292284). In the figure, reference numeral 1 denotes a wafer, and the wafer 1 is transferred by a wafer handling mechanism (not shown) and is mounted on a rotary table 2 which is a wafer mounting table. here,
The diameter of the mounting table 2a of the rotary table 2 is smaller than the diameter of the wafer 1, and when the wafer 1 is mounted on the mounting table 2a, the outer periphery 1a of the wafer 1 protrudes outside the mounting table 2a. Is placed. A linear light source 3a in which a plurality of LED elements are arranged is provided on the lower side so as to sandwich the protruding outer periphery 1a, and a linear light sensor 3b such as a one-line CCD image sensor is provided adjacent to the wafer 1 on the upper side. And each is arranged in parallel. Linear light source 3
a and a linear optical sensor 3b, there are provided rod lens arrays 3c and 3d each composed of a plurality of rod-shaped lenses arranged linearly, and a wafer 1 (sample) and a linear optical sensor 3b.
b (CCD), a filter (not shown) is inserted.

[0004] The characteristics of the filter are selected so as to transmit light corresponding to the wavelength of the LED of the linear light source 3a. The distance between the center of the rotary table 2 and the end of the light receiving element of the linear optical sensor 3b on the rotary table 2 side is l ₁
Have been set to the center and the distance between the end of the light receiving elements of the linear photosensor 3b is set to l _2. Thus, the number itself from the end of the light receiving element represents the distance from the rotation center to the outer periphery of the wafer 1. In the figure, 3e is a CCD drive circuit, and 3f is an LED power supply circuit.

In such a configuration, the rotary table 2
Is rotated, the linear optical sensor 3b receives a signal from the outer edge of the outer periphery of the wafer to the outer edge in response to the rotation. The outer peripheral position of the wafer can be detected from the position of the CCD that has received the outer end. With this configuration, the orientation flat OF and the center position of the wafer can be accurately calculated without the data of the outer peripheral position being affected by disturbance light.

[0006]

However, in such an outer peripheral position detecting device, a linear optical sensor for detecting the outer peripheral of the wafer is required. Must be retracted from the wafer surface.
For this purpose, a moving mechanism is required, and the positioning of the detection device by the moving mechanism is required to have high accuracy, and it is inevitably expensive.

[0007]

Means for Solving the Problems In a wafer foreign matter inspection apparatus, a detection optical system is usually provided on the upper part of the wafer, or a light from the upper part is separated for observing foreign matter by using a TV camera or the like. Can be observed.
Therefore, in order to eliminate the above-mentioned drawbacks and to simplify the outer periphery detecting mechanism, the wafer surface is illuminated by epi-illumination, the image of the wafer is directly captured by a TV camera, the outer periphery is calculated from the image, and the center position is calculated. I thought about finding out. However, when an image of the wafer is actually taken by a TV camera and displayed on a display, the wafer surface is strongly reflected and appears as a white wafer image portion W as shown in FIG. , A black outer video portion B is displayed outside the outer video portion B.

It has been found that the wafer image portion W does not accurately display the outer periphery of the wafer. This is shown in FIG.
As shown in the partial cross-sectional view of the peripheral portion of the wafer in (a), the outer edge portion 1b of the wafer 1 is inclined by polishing the peripheral portion. Therefore, the portion actually displayed in white is the portion of the edge A at which the inclination starts, and is not the original edge B of the wafer 1. In addition, the position of the edge A is an edge determined by the result of polishing, and differs for each wafer. As a result, in imaging using a TV or the like, the outer periphery of the wafer cannot be accurately detected. SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer foreign matter inspection apparatus which solves the above-mentioned drawbacks of the prior art, has a simple structure, and can easily locate the center of a wafer.

A feature of the wafer foreign matter inspection apparatus of the present invention for achieving the above object is that the outer peripheral side protrudes outside the table and is adjacent to the back side of the protruding outer peripheral portion of the wafer mounted on the table. A mirror is provided below the wafer, and the reflected light is reflected by the mirror to capture an image of the periphery of the wafer.

[0010]

As described above, if the mirror is provided below the wafer, the reflected light from the position outside the peripheral portion of the wafer can be reliably obtained. Further, light reflected from the surface of the wafer can be obtained as it is. Moreover, the reflected light cannot be obtained at the inclined edge portion of the peripheral portion when the wafer is polished. As a result, this inclined portion appears as a black stripe.
Although the inside of the black image of the edge portion is an inaccurate line due to polishing, the outside line is an accurate line corresponding to the outer periphery of the wafer. In a wafer foreign matter inspection apparatus, an objective optical system is usually arranged above a wafer, so that an image of a peripheral edge of the wafer can be captured by epi-illumination via the objective optical system. If the outer line is treated as the outer peripheral edge of the wafer according to the image data obtained through this and the center position is calculated, the center position of the wafer can be accurately obtained.

[0011]

FIG. 1 is a block diagram of a wafer foreign matter inspection apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory view of a detection mechanism portion, and FIG. 3 is an explanatory view of a display image on a display. In FIG. 1, a wafer 1 to be inspected is placed on a rotary table 2, and the rotary table 2 is provided on an XYZ moving stage 30 that can move in the XYZ directions. Reference numeral 4 denotes a He-Ne laser generator, which is driven when detecting foreign matter. In this case, the inspection surface of the wafer 1 is irradiated with a red laser, preferably at a low irradiation angle of about 2 ° to 10 °. Reference numeral 5 denotes an objective lens, which is reflected light of a red laser (scattered light at the edge of a foreign substance or a pattern).
In the vertical direction above the wafer 1. 5. The light received by the objective lens 5 is converted to a half mirror 6 provided at an upper portion thereof, which is inclined at approximately 45 °. The light is sent to a detection optical system 8 including an image sensor such as a CCD through a half mirror 7 inclined 45 ° in the opposite direction. In the detection optical system 8, the pattern on the wafer 1 is formed on the light receiving surface of the image sensor and received. The detection signal is processed by the image processing device 17 to detect foreign matter on the wafer.

Reference numeral 9 denotes an illumination device for visual observation of the visual observation optical system 14. The white light passes through the lens group 10, the half mirror 6, the objective lens 5, and irradiates the wafer 1 with light (emitted light). The reflected light from the surface of the wafer 1 is sent to the microscope 13 via the objective lens 5, the half mirror 6, the half mirror 7, the lens 11, and the half mirror 12. Here, the microscope observation optical system 14 is configured by these components.

The half mirror 12 of the microscope observation optical system 14 is arranged so as to be inclined so as to be parallel to the half mirror 7, and is divided here and a part of the light is condensed by the condenser lens of the image processing TV monitor system 20. Color video camera 1 after 15
6. The color video camera 16 receives an image identical to the image observed by the microscope, converts the image into an image signal, and an image processing device 17 including a microcomputer or the like.
Send to The image processing device 17 digitizes the received video signal, eliminates noise and the like in the signal, performs image processing on the digitized signal according to the position signal from the position control device 19 of the position control system according to a predetermined program, and performs image processing. The data is generated, converted to an analog video signal, and sent to the display 18. As a result, the image of the scanning point at that time is displayed on the screen of the display 18.

When an image of the entire wafer 1 is displayed in accordance with the scanning, the image processing device 17 displays the whole image of the wafer 1 from the past to the present when the whole wafer is scanned together with the image including the outline of the wafer 1 and the image including the chip outline. Is generated as a video signal and sent to the display 18 so that the entire foreign substance image of the wafer 1 is displayed on the screen of the display 18. Therefore, the microprocessor (MPU) 17a
In addition, a whole image display processing program 171 for displaying the whole image of the wafer is stored in the memory 17b.
Further, the memory 17b has a reference position of the center of the wafer + outline display program 172 for displaying a partial image from the center of the wafer to the outline, and a wafer center position calculation in order to perform alignment with the center of the wafer as a reference. A display program 173 and a wafer positioning program 174 are stored.

When the visual observation illumination device 9 of the visual observation system is activated, the display 18 displays a pattern image on the wafer, an image of the entire wafer, a partial image for center alignment, and an image of foreign matter on the display 18. Can be selectively displayed on the screen, and can be visually observed. The position control device 19 is controlled by the image processing device 17,
The rotary table 2 and the XYZ movement stage 30 are controlled to drive the wafer 1 in a spiral scan.
The objective lens 5 is positioned at a specific observation position, and an observation signal at that position is sent to the image processing device 17. The image processing device 17 displays the corresponding image on the screen of the display 18 in response to this.

Reference numeral 21 denotes a video tape recorder (VTR)
It is provided to record the visually observed video as it is. In addition to normal visual observation images,
This is effective for recording a red observation image when the He-Ne laser generator 4 is activated without activating the visual observation illumination device 9.

When the He-Ne laser generator 4 is activated to display a map of the foreign matter along with the outer shape of the wafer 1 using a red image, the position of the foreign matter is extracted by visual observation on the display 18 to determine the position of the chip having the foreign matter. You can know the position. Therefore, the chip number and the like can be input to the image processing device 17 and stored. Further, when the position of the foreign matter is confirmed and extracted by visual observation on the display 18, a more detailed position at the observation position can be designated by a mouse or the like and input to the image processing device 17.

A mirror 22 is mounted on the bracket 23. The bracket 23 is fixed to the base 30a of the XYZ moving stage 30 on which the rotary table 2 is mounted, and moves in the XYZ directions together with the rotary table 2. Therefore, the mirror 22 and the rotary table 2
Does not change even if the rotary table 2 moves in the XYZ directions. FIG. 2 shows the relationship between the wafer 1 and the mirror 22 in this case.

As shown in FIG. 2, the mirror 22 is disposed in the vicinity of the outer periphery of the wafer 1 and adjacent to the back surface thereof.
Therefore, the light irradiated on the wafer 1 through the objective lens 5 by activating the illumination device 9 for visual observation emits the objective lens 5 outside the outer periphery of the wafer 1 as shown by an arrow.
And the image at that time is reflected by the color video camera 16.
Supplied to

The resulting monitor image is shown in FIG.
As shown in (a), the image becomes white W, black B, and white W,
The polished tapered portion 24 on the outer periphery of the wafer 1 has black stripes B
Appears as. Therefore, if the boundary position between the black stripe B and the outer portion is calculated, accurate outer peripheral data on the wafer 1 can be obtained.

When the operator supports the whole image display from a keyboard (not shown), the image processing device 17 performs a process of displaying the entire image of the wafer 1. Next, by inputting an alignment function key from the keyboard, a reference position of the center of the wafer + outline display program 172 and a wafer center position calculation display program 173 are sequentially activated. As shown in FIG. 3 (b), the outer shape of the reference wafer is displayed as a partial image with a red mark (indicated by a dashed line) and a + mark at the center thereof, and the wafer 1 under observation is displayed.
Is green (displayed by a solid line), and is similarly displayed on the display 18 as a partial image with a + mark at the center.

Here, when a function key for positioning is input from the keyboard, a wafer positioning program 174 is started, and the position control device 19 is driven and positioned so that the wafer 1 matches the reference position. Since the red and green indications indicate that the wafer 1 is deviated from the reference, the operator does not need to input a function key for alignment from the keyboard.
The XYZ movement table 30 can be controlled by a cursor or the like or a mouse (not shown) to control the XYZ movement table 30 so that the green figure matches the red figure.

When this positioning is completed, the He-N
First, the e-laser generator 4 is activated and spiral scanning (or XY scanning is also possible). First, an image of the entire wafer 1 is collected as a red He-Ne laser image and displayed on the display 18. Since the pattern has regularity, it is determined whether it is a foreign matter or a pattern, the position of the foreign matter is designated, the objective lens 5 is positioned at the position where the foreign matter is detected, and the observation image is displayed with a red He-Ne laser. The image is captured and displayed on the display 18 in an enlarged state, and it is determined whether or not it is a foreign substance, or the image is recorded on the VTR 21.

As described above, in the embodiment, the example of the rotary table has been described, but this may be an XY table. Further, in the embodiment, the mirror is provided at one place, but it may be provided at a plurality of places. In particular, X
In the case of a Y table, it is preferable to provide the mirror corresponding to each side. In this case, a mirror may be attached to the base to which the XY table is fixed. In the embodiment, the image of the video camera is processed by the image processing apparatus to calculate the center position of the wafer from the display data of the outer peripheral edge portion of the wafer. The position of the edge of the wafer may be obtained by extracting the signal of the portion, and the center position of the wafer may be calculated.

[0025]

As described above, in the foreign matter inspection apparatus according to the present invention, since the image of the peripheral edge of the wafer can be captured by the objective optical system, the image data obtained through this can be used. By treating this outer line as the outer peripheral edge of the wafer and calculating the center position,
The center position of the wafer can be accurately calculated. In addition, since the outer periphery of the wafer can be detected simply by providing a mirror, there is no need to provide a dedicated light projecting system or light receiving system for detecting the outer periphery of the wafer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a wafer foreign matter inspection apparatus according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram of the detection mechanism.

FIG. 3A is an explanatory diagram of a display image on a display, and FIG. 3B is an explanatory diagram of a center-aligned display image.

FIG. 4 is an explanatory diagram of a detection mechanism of a conventional wafer foreign matter inspection device.

FIG. 5A is an explanatory diagram of a light reflection state when an edge portion of a wafer is viewed by the foreign matter inspection device of FIG. 4;
(A) is an explanatory view of a display image on a display corresponding thereto.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Rotary table, 4 ... He-Ne laser generator, 5 ... Objective lens, 6, 7, 12 ... Half mirror, 8 ... Detection optical system, 9 ... Illumination device for visual observation, 13 ...
Microscope, 14: Microscope observation optical system, 16: Color video camera, 17: Image processing device, 18: Position control device, 2
0: image processing TV monitor system, 21: video tape recorder (VTR), 22: mirror, 23: bracket, 30
... XYZ moving stage.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/68 G01B 11/30 G01N 21/88 H01L 21/66

Claims (2)

(57) [Claims] An object optical system disposed above a wafer in a wafer foreign matter inspection apparatus for detecting a position of an outer periphery of a wafer placed with an outer periphery protruding outside a table and positioning the wafer. An image processing apparatus that converts an image obtained from the objective optical system into an electric signal to generate image data, and a mirror provided on the lower side of the wafer adjacent to the rear surface side of the protruding outer peripheral portion, The mirror reflects incident light received from the objective optical system, obtains an image of the peripheral portion of the wafer through the objective optical system, and performs the image processing on the wafer from the image data of the outer peripheral edge portion of the wafer. A wafer foreign matter inspection device, wherein the wafer is positioned by calculating a center position. 2. The image processing apparatus converts an image obtained from the objective optical system into an electric signal by an image sensor and calculates a position of an outer peripheral edge portion from a signal of the image sensor instead of the image data. 2. The wafer foreign matter inspection device according to claim 1, wherein a central position of the wafer is calculated.