Wafer defect analysis device and wafer defect analysis method

Abstract

To provide a wafer defect analysis device.SOLUTION: A wafer defect analysis device comprises: an imaging mechanism including a light source for placing a wafer and emitting infrared light, a camera for pointing to the light source and photographing the wafer, a microscope objective lens located between the camera and the light source, a filter element located between the camera and the microscope objective lens, and a gain element located between the camera and the filter element; a height adjustment mechanism connected to the imaging mechanism and including a motor; and a processor signal-connected to the imaging mechanism. The height adjustment mechanism moves the imaging mechanism vertically, and the imaging mechanism photographs an image of the wafer, which is then received and analyzed by the processor to analyze defects on the wafer. Thereby, the defects can be accurately analyzed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a defect analysis apparatus and a defect analysis method, and more particularly to an apparatus and a method for analyzing wafer defects.

Background Art

[0002] With the progress of technology, single-crystalline silicon wafers are widely used in the semiconductor and optical industries. However, wafers are prone to subsurface defects during the manufacturing process, which causes problems in the stability and reliability of subsequent semiconductors. Therefore, how to detect subsurface defects on wafers is very important.

[0003] Known subsurface defect detection methods include a laser light emitter and a detector. The laser light emitter irradiates laser light at an angle below the surface of the wafer. In this way, when the laser light passes through a defect, it scatters and is received by the detector. However, since the energy of the scattered laser light is small and detection is difficult, there is still a deficiency in defect detection. In addition, there are other subsurface defect detection methods, but all of them have limitations in detection. For example, it is required that the sample to be detected is transparent or the requirement for the surface roughness of the sample to be detected is high, and it is difficult to accurately detect the depth of the defect in any case.

[0004] In view of this, how to improve such an apparatus for detecting and analyzing subsurface defects on wafers and improve its defect detection performance has become the goal of efforts by related practitioners.

Summary of the Invention

Means for Solving the Problems

[0005] To solve the above problems, the present invention provides an apparatus and a method for analyzing wafer defects that can improve their defect detection performance through their structural arrangements.

[0006] According to an embodiment of the present invention, there is provided an imaging mechanism including a light source for placing a wafer and emitting infrared light, a camera for facing the light source and photographing the wafer, a microscope objective lens located between the camera and the light source, a filter element located between the camera and the microscope objective lens, and a gain element located between the camera and the filter element, a height adjustment mechanism connected to the imaging mechanism and including a motor, and a processor signal-connected to the imaging mechanism. The height adjustment mechanism moves the imaging mechanism in the vertical direction. After photographing an image of the wafer, the imaging mechanism receives and analyzes it by the processor to provide an apparatus for analyzing wafer defects for analyzing defects on the wafer.

[0007] Thereby, infrared light can penetrate the wafer, especially a silicon wafer. In this way, the imaging mechanism can photograph a real image of the wafer and clearly recognize defects. Further, by moving the imaging mechanism in the vertical direction by the height adjustment mechanism, the focal position of the imaging mechanism can be moved to focus and photograph images at different positions in the vertical direction of the wafer, which can further contribute to analyzing the characteristics of defects, such as analyzing the depth of defects.

[0008] According to an embodiment of the above apparatus for analyzing wafer defects, the wavelength of the infrared light may be in the range of 1100 nm to 1500 nm.

[0009] According to an embodiment of the above apparatus for analyzing wafer defects, the motor may have a high-precision stepping motor structure.

[0010] According to an embodiment of the above apparatus for analyzing wafer defects, it may further include a pattern layer located between the light source and the wafer.

[0011] According to an embodiment of the above apparatus for analyzing wafer defects, the filter element may have a pinhole slit plate structure.

[0012] According to an embodiment of the present invention, there is provided a method for analyzing wafer defects, including: an illumination step of placing a wafer on a light source and transmitting infrared light emitted from the light source through the wafer; a motor of a height adjustment mechanism driving an imaging mechanism to move along the vertical direction toward the wafer and causing the imaging mechanism to capture a plurality of images of a shooting area on the wafer at a plurality of focal positions, the imaging mechanism including a camera, a gain element, a filter element, and a microscope objective lens in order along the vertical direction, and a processor performing a defect depth analysis step of confirming the depth of a defect in the shooting area based on the plurality of focal positions and the plurality of images.

[0013] According to an embodiment of the above method for analyzing wafer defects, the motor may further include a surface position confirmation step of driving the imaging mechanism to capture an image of the surface of the wafer, finding a focal position corresponding to the surface, and confirming the surface position of the wafer.

[0014] According to an embodiment of the above method for analyzing wafer defects, in the defect depth analysis step, using the surface position as a calculation reference point, when the average gradation value of one of the plurality of images is equal to or greater than a threshold value, the processor can obtain the numerical difference between the focal position corresponding to the one image and the surface position as the depth of the defect.

[0015] According to an embodiment of the above method for analyzing wafer defects, a pattern layer may be placed between the bottom surface of the wafer and the light source, and the motor may further include a bottom surface position confirmation step of driving the imaging mechanism to capture an image of the pattern layer, finding a focal position corresponding to the pattern layer, and confirming the bottom surface position of the wafer.

[0016] According to an embodiment of the above method for analyzing wafer defects, the motor may have a high-precision stepping motor structure.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For the sake of clear explanation, many practical details are described in conjunction with the following description. However, the reader should understand that these practical details are not intended to limit the present invention. That is, in some embodiments of the present invention, these practical details are not necessary. Also, to simplify the drawings, some well-known conventional structures and elements are shown simply and schematically in the drawings, and overlapping elements may be represented by the same number or similar numbers.

[0019] Also, in this specification, when an element (or mechanism or module, etc.) is "connected", "installed", or "coupled" to another element, it may mean that the element is directly connected, directly installed, or directly coupled to the other element, or it may mean that an element is indirectly connected, indirectly installed, or indirectly coupled to another element, that is, it means that other elements are interposed between the element and the other element. When it is explicitly stated that an element is "directly connected", "directly installed", or "directly coupled" to another element, it is shown that no other element is interposed between the element and the other element. Terms such as first, second, and third are only for explaining different elements or components and do not limit the elements / components themselves, so the first element / component can be read as the second element / component. Also, the combinations of elements / components / mechanisms / modules in this specification are not the generally well-known, ordinary, or well-known combinations in this field, and whether the combination relationship can be easily achieved by those skilled in the art in the technical field can be determined depending on whether the elements / components / mechanisms / modules themselves are well-known.

[0020] Please refer to FIG. 1. FIG. 1 shows a structural schematic diagram of a wafer defect analysis apparatus 100 according to an embodiment of the present invention. The wafer defect analysis apparatus 100 includes a light source 130, an imaging mechanism 120, a height adjustment mechanism 140, and a processor 150. The light source 130 is used to emit infrared light with the wafer W1 placed thereon. The imaging mechanism 120 includes a camera 121, a microscope objective lens 124, a filter element 123, and a gain element 122. The camera 121 is used to photograph the wafer W1 facing the light source 130. The microscope objective lens 124 is located between the camera 121 and the light source 130. The filter element 123 is located between the camera 121 and the microscope objective lens 124. The gain element 122 is located between the camera 121 and the filter element 123. The height adjustment mechanism 140 is connected to the imaging mechanism 120 and includes a motor 141. The processor 150 is signal-connected to the imaging mechanism 120. The height adjustment mechanism 140 moves the imaging mechanism 120 in the vertical direction Z. After the imaging mechanism 120 photographs an image of the wafer W1, it is received and analyzed by the processor 150 to analyze the defect D1 on the wafer W1.

[0021] Thereby, infrared light can penetrate the wafer W1, particularly the wafer W1 made of a single crystal silicon component. In this way, the imaging mechanism 120 can photograph a real image of the wafer W1 and clearly recognize the defect D1. Further, by moving the imaging mechanism 120 in the vertical direction Z by the height adjustment mechanism 140, the focal position of the imaging mechanism 120 can be moved to focus on and photograph images of different positions of the wafer W1 in the vertical direction Z, which can further contribute to analyzing the characteristics of the defect D1, such as the depth H1 of the defect D1 (shown in FIG. 2). Details of the wafer defect analysis apparatus 100 will be described later.

[0022] The wafer defect analysis apparatus 100 may further include a base 160 and a horizontal movement mechanism 110. The base 160 includes a workbench 161 and a stand 162 vertically connected to the workbench 161. The horizontal movement mechanism 110 may include a stage 111 and a horizontal slide rail 112. The horizontal slide rail 112 is fixed to the workbench 161. The stage 111 is provided on the horizontal slide rail 112 and moves the wafer W1 placed thereon in the horizontal direction X. Preferably, the stage 111 is made of a transparent material. In other embodiments, no stage is provided, and the light source may be directly provided on the horizontal slide rail, but it is not limited thereto. The horizontal slide rail 112 may be, for example, a slide rail structure having linear balls, and the slide base of the horizontal slide rail 112 can be driven to move the stage 111 relative to the workbench 161. In other embodiments, the wafer defect analysis apparatus may include two horizontal movement mechanisms, which are used to move the wafer in two horizontal directions (for example, the length direction and the width direction perpendicular to each other) relative to the workbench, or one horizontal movement mechanism moves the stage in one horizontal direction, and the other horizontal movement mechanism moves the imaging mechanism in the other horizontal direction, but it is not limited to the above disclosure.

[0023] The height adjustment mechanism 140 may include a motor 141, a vertical slide rail 142, and a controller 143. The vertical slide rail 142 is provided on the stand 162, and the motor 141 is also provided on the stand 162. The vertical slide rail 142 may be a slide rail structure having, for example, linear balls. The controller 143 drives the motor 141 to move the slide base of the vertical slide rail 142 so as to move the imaging mechanism 120 connected to the slide base in the vertical direction Z. In the embodiment of FIG. 1, the motor 141 may have a high-precision stepping motor structure, and can accurately control minute movement in the vertical direction Z of the imaging mechanism 120, for example, 0.1 μm, and can further avoid vibration during movement that may interfere with optical focusing. The controller 143 may also be signal-connected to the processor 150 to receive instructions from the processor 150.

[0024] The imaging mechanism 120 is connected to the slide base of the vertical slide rail 142. In the imaging mechanism 120, the camera 121, the gain element 122, the filter element 123, and the microscope objective lens 124 are provided in order from top to bottom along the vertical direction Z. That is, the microscope objective lens 124 is closest to the wafer W1, and the camera 121 is farthest from the wafer W1. The camera 121 may have an infrared CCD or CMOS camera structure and can capture high-pixel images. The gain element 122 may be, for example, a gain element for light rays, for example, a photodiode array. The filter element 123 may have a pinhole slit plate structure, but is not limited thereto. The filter element 123 can be used to filter non-focused light rays (for example, light ray L2) and allow focused light rays (for example, light ray L1) to pass through and enter the camera 121, thereby avoiding the data of the non-focused surface and the focused surface included in the captured image overlapping each other and interference occurring so that the defect D1 cannot be clearly seen. After filtering and removing the non-focused light rays, the intensity of the light rays becomes weak, so the gain element 122 can enhance the light rays to avoid the captured image being too dark.

[0025] The imaging mechanism 120 may have a modular structure that is pre-assembled and fixed, and the distance between each element is fixed, thereby fixing the focus of the imaging mechanism 120. Since the focus of the imaging mechanism 120 is fixed, when the height adjustment mechanism 140 moves the imaging mechanism 120 and moves it in the vertical direction Z, the focus also moves in the vertical direction Z, and different focus positions are formed.

[0026] The light source 130 may have a flat light source structure that emits uniform infrared light and can transmit through the wafer W1. In the embodiment of FIG. 1, the wavelength of the infrared light may be in the range of 1100 nm to 1500 nm. In this way, it can contribute to transmitting through the wafer W1 of single crystal silicon component. The wavelength of the infrared light may be, for example, 1200 nm, and the transmittance when it transmits through the wafer W1 of single crystal silicon component is the maximum.

[0027] Please refer to FIG. 2 and also refer to FIG. 1 in conjunction. FIG. 2 is a diagram of different images taken by the wafer defect analysis apparatus 100 according to the embodiment of FIG. 1 at different focus positions. As shown at the top of FIG. 2, the stage 111 can be first moved to correspond the imaging mechanism 120 to the imaging area on the wafer W1. The height adjustment mechanism 140 can move and relocate the imaging mechanism 120 and find a focus position that can be clearly focused on the surface of the wafer W1. This focus position is defined as the surface position P1 of the wafer W1 and can be recorded. In particular, when the imaging mechanism 120 is in focus, the captured image becomes clear and the defect D1 on the surface of the wafer W1 can be clearly seen. It should be noted that whether there is a clear focus can be determined by the processor 150 analyzing the image. The processor 150 may be, for example, a central processing unit (CPU), a digital signal processor (DSP), a microprocessor (MPU), and a microcontroller (MCU), etc., and the processor 150 can be programmed to achieve specific functions.

[0028] The height adjustment mechanism 140 can continuously move the imaging mechanism 120 downward along the vertical direction Z, that is, move it toward the wafer W1. On the other hand, as described above, the imaging mechanism 120 is a module with a fixed focus, and the focus moves downward accordingly, so different focus positions can be generated within the range of the vertical direction Z in this imaging area. In this way, the imaging mechanism 120 can continuously capture images of the wafer W1 at different focus positions. In the embodiment of FIG. 1, each time the height adjustment mechanism 140 moves by a set distance, the imaging mechanism 120 may automatically capture an image, thereby recording the correspondence between the focus position and the image.

[0029] Since the defect D1 extends in the horizontal direction X and the vertical direction Z, when the defect D1 cannot be seen or can hardly be seen in the image corresponding to a certain focus position (for example, the focus position P2), it is shown that the defect D1 ends without extending further downward.

[0030] Generally, as shown in FIG. 2, the image includes a plurality of defects D1, and the depths H1 of the respective defects D1 do not necessarily match, with some being deep and some being shallow. Therefore, when the focal position is further downward, only the deep defects D1 will be photographed. As a result, the number of defects D1 visible in the image will become fewer and fewer. The processor 150 can calculate the average gradation value of the entire image. Since the defects D1 are dark in color, when the number of defects D1 is large, as shown at the surface position P1, the image becomes dark and the average gradation value becomes low. At this time, the average gradation value may be, for example, 64. Conversely, when the number of defects D1 is small, that is, as shown at the focal position P2, the image becomes bright and the average gradation value becomes high. At this time, the average gradation value may be, for example, 240. Therefore, in this embodiment, by setting a threshold value (which is between 220 and 255, for example, 240), the situation of the defects D1 can be confirmed. When the number of defects D1 decreases and the average gradation value becomes equal to or greater than the threshold value, it is indicated and recorded that there are no defects D1 at this focal position (that is, the focal position P2), or even if there are defects D1, they no longer affect reliability, performance, etc. Since the imaging mechanism 120 is moved by the height adjustment mechanism 140, the moving distance can be grasped, the numerical value in the vertical direction Z of this focal position (that is, the focal position P2) can be grasped, the numerical value in the vertical direction Z of the surface position P1 can also be grasped, the difference between the two numerical values can be calculated, and the depth H1 in the vertical direction Z of the deepest defect D1 in this imaging area can be obtained. A plurality of imaging areas can be set on the wafer W1, and the one with the largest depth H1 among these imaging areas can be regarded as the depth H1 of the defect D1 of the wafer W1, which can be used to determine whether it is necessary to perform a polishing process on the subsequent wafer W1 and the value of the polishing depth in the polishing process.

[0031] The wafer defect analysis apparatus 100 may further include a pattern layer 170. The pattern layer 170 may be located between the light source 130 and the wafer W1. As shown in FIG. 2, the height adjustment mechanism 140 moves the imaging mechanism 120 to find a focal position where it can be clearly focused on the pattern layer 170, and the processor 150 can define this focal position as the bottom surface position P3 of the wafer W1. In some cases, after first finding the bottom surface position P3, the imaging mechanism 120 is moved to the surface position P1, and the difference between the bottom surface position P3 and the surface position P1 is first taken to determine whether it matches the thickness of the wafer W1, so as to initially confirm whether the wafer defect analysis apparatus 100 is normal, but it is not limited to this.

[0032] Please refer to FIG. 3. FIG. 3 shows a block flowchart of a wafer defect analysis method S200 according to another embodiment of the present invention. The wafer defect analysis method S200 includes an illumination step S210 and a defect depth analysis step S240. For details of the wafer defect analysis method S200, reference will be made to the wafer defect analysis apparatus 100 in FIGS. 1 and 2 and described later.

[0033] In the illumination step S210, the wafer W1 is placed on the light source 130, and the infrared light emitted from the light source 130 passes through the wafer W1.

[0034] In the defect depth analysis step S240, the motor 141 of the height adjustment mechanism 140 drives the imaging mechanism 120 to move toward the wafer W1 along the vertical direction Z, and the imaging mechanism 120 takes a plurality of images of the imaging area on the wafer W1 at a plurality of focal positions respectively. The imaging mechanism 120 sequentially includes a camera 121, a gain element 122, a filter element 123, and a microscope objective lens 124 along the vertical direction Z. The processor 150 confirms the depth H1 of the defect D1 in the imaging area based on the plurality of focal positions and the plurality of images.

[0035] Specifically, the wafer defect analysis method S200 may further include a surface position confirmation step S230 in which the motor 141 drives the imaging mechanism 120 to capture an image of the surface of the wafer W1, finds the focal position corresponding to the surface, and confirms the surface position P1 of the wafer W1. Thereafter, in the defect depth analysis step S240, the surface position P1 can be used as a calculation reference point. When the average gradation value of the defect D1 in one of the plurality of images is equal to or greater than the threshold value, the processor 150 can obtain the numerical difference between the focal position (focal position P2) corresponding to the one image and the surface position P1 as the depth H1 of the defect D1.

[0036] As described above, since the height adjustment mechanism 140 can move the imaging mechanism 120 in the vertical direction Z, the focal position can be continuously changed, different focal positions are formed on the wafer W1. That is, the imaging mechanism 120 can move in the vertical direction Z1 to focus at different focal positions and capture a clear image at this focal position. In this way, the processor 150 can accurately recognize the defect D1 from the clear image, confirm whether the defect D1 exists in the image, and obtain the average gradation value of the image. In this way, the depth H1 of the defect D1 can be obtained based on the distance that the height adjustment mechanism 140 moves, that is, the numerical difference in the vertical direction Z between the focal position (for example, focal position P2) and the surface position P1.

[0037] The wafer defect analysis method S200 may further include a bottom surface position confirmation step S220 in which a pattern layer 170 is placed between the bottom surface of the wafer W1 and the light source 130, and the motor 141 drives the imaging mechanism 120 to capture an image of the pattern layer 170, finds the focal position corresponding to the pattern layer 170, and can confirm the bottom surface position P3 of the wafer W1. In this way, as described above, the thickness of the wafer W1 can be calculated based on the numerical difference in the vertical direction Z between the bottom surface position P3 and the surface position P1, compared with the known thickness of the wafer W1, and it can be confirmed whether all elements operate normally.

[0038] Although the present invention is disclosed in the embodiments as described above, the above-described embodiments are not intended to limit the present invention, and any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on what is defined by the scope of the appended claims.

Explanation of Reference Numerals

[0039] 100: Wafer defect analysis device 110: Horizontal movement mechanism 111: Stage 112: Horizontal slide rail 120: Imaging mechanism 121: Camera 122: Gain element 123: Filter element 124: Microscope objective lens 130: Light source 140: Height adjustment mechanism 141: Motor 142: Vertical slide rail 143: Controller 150: Processor 160: Base 161: Workbench 162: Stand 170: Pattern layer D1: Defect H1: Depth L1, L2: Light rays P1: Surface position P2: Focus position P3: Bottom surface position S200: Wafer defect analysis method S210: Illumination step S220: Bottom surface position confirmation step S230: Surface position confirmation step S240: Defect depth analysis step W1: Wafer X: Horizontal direction Z: Vertical direction

Claims

1. a light source for placing the wafer and emitting infrared light; an imaging mechanism including a camera aimed at the light source and for imaging the wafer, a microscope objective lens positioned between the camera and the light source, a filter element positioned between the camera and the microscope objective lens, and a gain element positioned between the camera and the filter element; a height adjustment mechanism connected to the imaging mechanism and including a motor; a processor signally connected to the imaging mechanism; Equipped with The height adjustment mechanism moves the imaging mechanism vertically, and the imaging mechanism captures an image of the wafer, which is then received and analyzed by the processor, thereby analyzing defects on the wafer.

2. 2. The wafer defect analysis device according to claim 1, wherein the wavelength of the infrared light is in the range of 1100 nm to 1500 nm.

3. 2. The wafer defect analysis device according to claim 1, wherein the motor has a high-precision stepping motor structure.

4. 10. The apparatus for analyzing wafer defects of claim 1, further comprising a pattern layer positioned between said light source and said wafer.

5. 2. The apparatus for analyzing wafer defects according to claim 1, wherein the filter element has a pinhole slit plate structure.

6. an illumination step in which the wafer is placed on a light source and infrared light emitted from the light source is transmitted through the wafer; a motor of the height adjustment mechanism drives an imaging mechanism to move the imaging mechanism toward the wafer along a vertical direction, and causes the imaging mechanism to capture a plurality of images of an imaging area on the wafer at a plurality of focal positions, the imaging mechanism including a camera, a gain element, a filter element, and a microscope objective lens arranged in that order along the vertical direction, and a processor performs a defect depth analysis step of confirming a depth of a defect in the imaging area based on the plurality of focal positions and the plurality of images; A method for analyzing wafer defects comprising:

7. 7. The method for analyzing wafer defects according to claim 6, further comprising a surface position confirmation step in which the motor drives the imaging mechanism to capture an image of the surface of the wafer, finds the focal position corresponding to the surface, and confirms the surface position of the wafer.

8. 8. The method for analyzing wafer defects according to claim 7, wherein, in the defect depth analysis process, the surface position is used as a calculation reference point, and when an average gradation value of one of the plurality of images becomes equal to or greater than a threshold value, the processor acquires a numerical difference between the focal position and the surface position corresponding to the one image as the depth of the defect.

9. 7. The method for analyzing wafer defects according to claim 6, further comprising a bottom position confirmation step of placing a pattern layer between the bottom surface of the wafer and the light source, the motor driving the imaging mechanism to capture an image of the pattern layer, finding the focal position corresponding to the pattern layer, and confirming the bottom position of the wafer.

10. 7. The method for analyzing defects on a wafer according to claim 6, wherein the motor has a high-precision stepping motor structure.

Images