TWI714395B - Surface defect detection apparatus for wafer - Google Patents

Abstract

A surface defect detection apparatus for wafer includes a visible light source, a light sensor array, and a processor. The light sensor array includes plural light sensor arranged in an array. The processor groups the light sensors into plural defect accumulate groups. Each light sensor has a light intensity level output range, and the processor sets a light intensity level threshold in the light intensity level output range. When the light intensity is larger than the light intensity level threshold, the processor determines a unit defect exists within the light sensor detection area. Finally, the processor sequentially determines whether the unit defect exists within each light sensor detection area, accumulates these unit defects to obtain the defect area accumulation.

Description

Wafer surface defect detection equipment

The invention relates to defect detection on the surface of a wafer, and particularly relates to a defect detection device on the surface of a wafer.

The length of defects that can be tolerated on the wafer surface is measured in μm, which cannot be directly detected by the naked eye. The defect detection on the wafer surface needs to be magnified by image magnifying equipment. Because of the low efficiency of human eyes for observing enlarged images and the possibility of misjudgment, there has been the development of wafer surface defect detection equipment.

One of the development directions of wafer surface defect detection equipment is to use intelligent image analysis to analyze whether there are defects in the wafer surface image. However, the amount of data calculation required for image analysis is relatively large, which leads to an increase in the setup cost of the data processing device, otherwise the demand for rapid detection cannot be met.

The actual defect detection is to determine the size and location of the defect to determine whether the wafer is a usable good product. Therefore, some estimation methods are used to judge only the size and location of flaws without using image analysis. The estimation method is to project laser light of a specific wavelength on the wafer surface, and then use a photodiodes sensor (PD sensor) matrix to receive the reflected light. If the light intensity received by the light detecting diode is lower than a threshold value, it is estimated that there is a certain size of flaw in the detected area. The sum of the defects obtained by the photodetection diode matrix is regarded as the largest defect. The photodetection diode matrix scans the wafer surface one by one to get the size and relative position of the defect, so as to determine whether the wafer is good.

However, the construction cost of the laser light source is relatively high, and it is not easy to project a large area. The photodetection diode matrix cannot be arranged densely either, usually only a 100×200 matrix can be set, which makes the area of the matrix detected at one time too small. If the density of the matrix is simply increased to increase the area of a test, the amount of data calculation will be greatly increased, and the cost of equipment construction will increase.

In view of the above problems, the present invention proposes a wafer surface defect detection equipment, which can reduce equipment cost and improve detection efficiency.

At least one embodiment of the present invention provides a wafer surface defect detection device for detecting defects on a wafer surface. The wafer surface defect detection equipment includes a visible light source, a light sensor matrix assembly, and a data processing device. The visible light source is used to project a visible light to be reflected by the wafer as a reflected light. The light sensor matrix assembly is formed by arranging a plurality of light sensors, and the multiple light sensors are respectively used to receive the reflected light to obtain a light intensity value; wherein, the light sensor matrix combination system is configured Detect each light intensity value in a light sensor sensing area for each light sensor on the wafer surface, and a defect detection range of the light sensor matrix assembly is determined by the light sensors Sensing area composition. The data processing device is electrically connected to the light sensor matrix assembly; the data processing device receives the light intensity values to determine whether there are defects in the sensing area of each light sensor.

The data processing device groups the multiple light sensors into multiple defect statistical units, and each defect statistical unit forms a sub-matrix in the photo sensor matrix assembly. Each light sensor has a light intensity value output range, and the data processing device sets a light intensity value threshold in the light intensity value output range; when the light intensity value output by each light sensor is greater than the light intensity value threshold, data processing The device judges that there is a unit defect in the sensing area of the light sensor. The data processing device sequentially determines whether there is a unit defect in the sensing area of each light sensor, and sums the unit defects obtained by each defect statistical unit to obtain a statistical value of the defect area.

In at least one embodiment, the wafer surface defect detection equipment further includes a carrier platform. The data processing device controls the carrier platform. The carrier platform is used to carry the wafer and move the wafer relative to the defect detection range to change the defect. The detection range is located on the surface of the wafer, so that the defect detection range can sweep the surface of the wafer completely.

In at least one embodiment, the data processing device sequentially determines the statistical value of the defect area of each defect statistical unit to obtain the number, area, and relative position of the defect in the defect detection range.

In at least one embodiment, the data processing device controls the carrier platform, changes the position of the defect detection range, and re-executes the determination of the statistical value of the defect area of each defect statistical unit until the defect detection range sweeps across the wafer surface. All.

In at least one embodiment, the wafer surface defect detection equipment further includes a beam splitter and an objective lens group, the beam splitter is used to reflect visible light to the objective lens group, and the objective lens group condenses the visible light on the wafer surface to form a condensing point, and The visible light reflected by the surface of the wafer is the reflected light, which penetrates the objective lens group and the beam splitter, and is projected to the light sensor matrix assembly.

In at least one embodiment, the wafer surface defect detection equipment further includes an optical component disposed between the visible light source and the beam splitter for collimating visible light.

In at least one embodiment, the wafer surface defect detection equipment further includes an optical component disposed between the visible light source and the beam splitter to filter the visible light and reduce a wavelength distribution range of the visible light.

In at least one embodiment, the defect detection range falls within the concentrating point and is smaller than the concentrating point.

In the present invention, the data processing device uses the defect statistical unit to determine the number, area, and relative position of the defects one by one, instead of using the light sensor matrix assembly to make the judgment at a time, which can effectively reduce the amount of calculation. Therefore, matrix density can be used. A relatively high camera chip, such as CCD or CMOS, is used as a light sensor matrix assembly to increase the defect detection range and speed up the inspection process. In addition, the data processing device estimates the defect area by the light intensity value instead of judging the defect through image analysis, which speeds up the defect detection process.

Please refer to FIG. 1, which is a wafer surface defect detection device disclosed in an embodiment of the present invention, which is used to detect defects on the surface of a wafer W. The wafer surface defect detection equipment includes a visible light source 100, a beam splitter 200, an objective lens group 300, a photo sensor matrix assembly 400, a carrier platform 500 and a data processing device 600.

As shown in FIG. 1, the visible light source 100 is used to emit visible light V with a wavelength range of 380 nm to 780 nm to project a visible light V, which is reflected by the wafer W as a reflected light R.

As shown in FIG. 1, the beam splitter 200 is used to reflect visible light V to the objective lens group 300, and the objective lens group 300 condenses the visible light V on the surface of the wafer W to form a condensing point S. The visible light V reflected on the surface of the wafer W is the reflected light R, which penetrates the objective lens group 300 and the beam splitter 200, and is projected to the photo sensor matrix assembly 400.

As shown in FIGS. 1, 2 and 3, the photo sensor matrix assembly 400 is formed by arranging a plurality of photo sensors 410 and detects the light intensity toward the wafer W. The plurality of light sensors 410 are respectively used to receive the reflected light R to obtain a light intensity value I respectively. In addition, the defect detection range of the photo sensor matrix assembly 400 is adjusted through the objective lens group 300 so that each photo sensor 410 detects the light intensity in a photo sensor sensing area SA on the surface of the wafer W With a value of I, the sensing area SA of each light sensor is much smaller than the area of the wafer W. The defect detection range of the photo sensor matrix assembly 400 is composed of the light sensor sensing areas SA, and the defect detection range falls in the light-concentrating point S and is smaller than the light-concentrating point S. What is shown in FIG. 3 is a schematic diagram of the light sensor 410 and the light sensor sensing area SA, and is not used to limit the detailed structure or relative positional relationship of each element.

As shown in FIG. 1, the carrier platform 500 is used to carry the wafer W, and moves the wafer W relative to the condensing point S and the defect detection range, thereby changing the concentrating point S and the defect detection range on the surface of the wafer W , So that the defect detection range can be swept across the surface of the wafer W completely.

In order to improve the projection state of the visible light V on the beam splitter 200, an optical assembly 110 is arranged between the visible light source 100 and the beam splitter 200 to collimate the visible light V so that the divergent visible light V is converted into collimated light and then projected to Spectroscope 200. The optical component 110 can also filter the visible light V to reduce the wavelength distribution range of the visible light V, for example, only allow red light with a wavelength between 622 nm and 760 nm to pass. Therefore, the optical component 110 may be a combination of a collimating lens and a filter, but it does not exclude that only one of them is used or other optical elements are used to produce different optical effects. Moreover, if the visible light source 100 itself can directly project the visible light V in a collimated light state, or the visible light V generated is limited to a specific wavelength range, the optical assembly 110 can be partially or completely omitted.

In a specific embodiment, the range of the condensing point S can be set to a circular area with a diameter greater than 5 mm. The photo sensor matrix assembly 400 is a CCD matrix (Charge-Coupled Device Array, CCD Array) or a CMOS matrix (Complementary Metal-Oxide-Semiconductor Array, CMOS Array), with 2 million pixels, and its light sensing The devices 410 are arranged in a matrix of 2000×1000. The light sensor sensing area SA of each light sensor 410 is 2 μm×2 μm. Therefore, the defect detection range of the photo sensor matrix assembly 400 can reach 4000 μm×2000 μm (4mm×2mm).

As shown in FIG. 1, the data processing device 600 is electrically connected to the photo sensor matrix assembly 400 and the carrier platform 500. The data processing device 600 controls the carrier platform 500 so that the wafer W is relative to the focusing point S and the defect detection range. The data processing device 600 receives the light intensity values I to determine whether there is a defect in the sensing area SA of each light sensor.

As shown in FIG. 1 and FIG. 2, the data processing device 600 groups a plurality of light sensors 410 into a plurality of defect statistical units 420, and each defect statistical unit 420 forms a sub-matrix in the photo sensor matrix assembly 400. The photo sensor matrix assembly 400 is composed of a plurality of defect statistical units 420.

As shown in FIGS. 1, 2 and 4, the light sensor 410 has a light intensity value I output range, and 8 bits are usually used to represent the light intensity value I output. That is, the output range of the light intensity value I will be divided into 256 levels (0~255). The data processing device 600 sets a light intensity value threshold T in the output range of the light intensity value I. When the light intensity value I output by the light sensor 410 is less than the light intensity value threshold T, it is determined that there is no defect in the corresponding light sensor sensing area SA, if the light intensity value I output by the light sensor 410 is greater than the light intensity Value threshold T, the data processing device 600 determines that there is a unit defect in the light sensor sensing area SA.

As shown in FIGS. 2 and 3, the data processing device 600 sequentially determines whether there is a unit defect in each light sensor sensing area SA, and adds the unit defects obtained in each defect statistical unit 420 to obtain the defect Area statistics.

In a specific embodiment, a standard sample test can be used to establish the light intensity threshold T and the corresponding unit defect. For example, assuming that the light intensity value I is the 19th level of the 256 levels as the light intensity value threshold T, the corresponding unit defect is 1 μm ² ; the defect statistical unit 420 is composed of a 20×20 light sensor 410. At this time, the statistical value of the defect area will fall between 0 ~ 40μm ² , and the smallest detectable defect area is 1μm ² .

After that, the data processing device 600 sequentially determines the statistical value of the defect area obtained by each defect statistical unit 420 to obtain the number, area, and relative position of the defect in the defect detection range. Finally, the data processing device 600 controls the carrier platform 500, changes the position of the defect detection range, and re-executes the determination of the statistical value of the defect area of each defect statistical unit 420 until the defect detection range sweeps the entire surface of the wafer W , You can get the number, area and relative position of the flaws. In the foregoing embodiment, the data processing device 600 can calibrate a flaw area of 1 μm ² at least and a flaw area of 40 μm ² at a maximum. This defect area is sufficient to determine whether the wafer W is good.

The data processing device 600 uses the defect statistical unit 420 to determine the number, area, and relative position of the defects one by one, instead of using the light sensor matrix assembly 400 to judge at a time, which can effectively reduce the amount of calculation. Therefore, the matrix density can be quite high. A camera chip such as CCD or CMOS is used as the photo sensor matrix assembly 400 to increase the defect detection range and speed up the detection process. Moreover, the data processing device 600 estimates the defect area based on the light intensity value I instead of judging the defect through image analysis, which also speeds up the defect detection process. In the above-mentioned specific embodiment, a general personal computer or industrial computer is used as the data processing device 600, and the inspection of an 8-inch wafer W (diameter 203.2 mm) can be completed in only 30 seconds.

100: Visible light source 110: Optical components 200: Spectroscope 300: Objective lens group 400: Light sensor matrix assembly 410: Light Sensor 420: Defect Statistics Unit 500: bearing platform 600: data processing device I: light intensity value R: reflected light S: Spotlight SA: light sensor sensing area T: Threshold of light intensity value V: Visible light W: Wafer

FIG. 1 is a schematic side view of a wafer surface defect detection device in an embodiment of the present invention. Fig. 2 is a schematic front view of a light sensor matrix assembly in an embodiment of the present invention. 3 is a schematic diagram of a light sensor and a sensing area of the light sensor in an embodiment of the present invention. FIG. 4 is a schematic diagram of the light intensity value output range and the light intensity value threshold in the embodiment of the present invention.

100: Visible light source

110: Optical components

200: Spectroscope

300: Objective lens group

400: Light sensor matrix assembly

410: Light Sensor

500: bearing platform

600: data processing device

R: reflected light

S: Spotlight

V: Visible light

W: Wafer

Claims (7)

A wafer surface defect detection device for detecting defects on a wafer surface; the wafer surface defect detection device includes: a visible light source for projecting a visible light to be reflected by the wafer as a reflected light; A light sensor matrix assembly is formed by arranging a plurality of light sensors, and the light sensors are respectively used to receive the reflected light to obtain a light intensity value; wherein, the light sensor The matrix combination system is configured such that each photo sensor detects each light intensity value in a photo sensor sensing area on the wafer surface, and a defect detection of the photo sensor matrix assembly The measurement range is composed of the light sensor sensing areas; a data processing device is electrically connected to the light sensor matrix assembly; the data processing device receives the light intensity values to determine each light sensor Whether the defect exists in the sensor sensing area; wherein the data processing device groups the plurality of light sensors into a plurality of defect statistical units, and each of the defect statistical units forms one in the photo sensor matrix assembly A sub-matrix; and a carrier platform, the data processing device controls the carrier platform, the carrier platform is used to carry the wafer, and move the wafer relative to the defect detection range, thereby changing the defect detection range in the wafer The position of the circular surface allows the flaw detection range to sweep the surface of the wafer completely; wherein each of the light sensors has a light intensity value output range, and the data processing device sets the light intensity value output range A light intensity value threshold; when the light intensity value output by each light sensor is greater than the light intensity value threshold, the data processing device determines that there is a unit defect in the sensing area of the light sensor; and the data The processing device sequentially determines whether the unit defect exists in each of the light sensor sensing areas, and sums the unit defects in each of the defect statistical units, A statistical value of defect area is obtained; the data processing device sequentially determines the statistical value of the defect area of each defect statistical unit to obtain the number, area and relative position of the defect in the defect detection range. The wafer surface defect detection equipment according to claim 1, wherein the data processing device controls the carrier platform, changes the position of the defect detection range, and re-executes the judgment operation of the statistical value of the defect area of each defect statistical unit, Until the defect detection range sweeps across the entire surface of the wafer. The wafer surface defect detection equipment according to claim 1, further comprising a beam splitter and an objective lens group for reflecting the visible light to the objective lens group, and the objective lens group condenses the visible light on the wafer surface A condensing spot is formed, and the visible light reflected by the surface of the wafer is the reflected light, penetrates the objective lens group and the beam splitter, and is projected to the photo sensor matrix assembly. The wafer surface defect detection equipment according to claim 3 further includes an optical component arranged between the visible light source and the beam splitter for collimating the visible light. The wafer surface defect detection equipment according to claim 3 further includes an optical component disposed between the visible light source and the beam splitter for filtering the visible light and reducing a wavelength distribution range of the visible light. The wafer surface defect detection device according to claim 3, wherein the defect detection range falls within the condensing point and is smaller than the condensing point. The wafer surface defect detection device according to claim 1, wherein the photo sensor matrix assembly is a CCD matrix or a CMOS matrix.

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