Pre-alignment method and pre-alignment device

Abstract

The invention relates to the technical field of semiconductors, and provides a pre-alignment method and a pre-alignment device.The pre-alignment method comprises the steps that S1, edge information of a wafer is collected to obtain eccentricity, and the position of the wafer is adjusted to compensate the eccentricity of the wafer; s2, collecting image information of a scribing groove in the upper surface of the wafer, obtaining the actual direction of the scribing groove, and rotating the wafer to adjust the direction of the scribing groove of the wafer to a specified direction; and S3, collecting edge image information of the edge of the upper surface of the wafer in the illumination area, and matching the edge image information with the notch of the template to obtain the position of the notch of the wafer to complete orientation. The method is suitable for the pre-alignment of the wafer of which the notch morphology changes drastically, the working efficiency can be improved, and the automatic alignment operation can be realized.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a pre-alignment method and a pre-alignment device. Background Art

[0002] Wafer pre-alignment is an important module of the transmission subsystem. The transmission robot takes the wafer from the wafer storage, and after the wafer is centered and oriented by the wafer pre-alignment equipment, the wafer is loaded onto the worktable by the robot, and then moved to the alignment station for alignment. It is required that after the wafer is initially positioned by the pre-alignment equipment, the mark on the wafer can enter the alignment field of view. Since the wafer mark has a higher positional accuracy relative to the geometric features of the wafer, wafer pre-alignment is based on the geometric features of the outer circle of the wafer to achieve wafer centering, and based on geometric features such as edge notches or flat edges to achieve wafer orientation. The corresponding orientation method is generally to provide light to the edge of the wafer from top to bottom, and identify the notch by the difference in light and dark.

[0003] During the wafer processing, certain processes may cause changes in the appearance of the notches on the wafer.

[0004] Taking the TSV (through silicon via) process as an example, TSV is the latest technology that realizes interconnection between chips by making vertical conductions between chips and between wafers. It has the advantages of small package size, fast signal transmission and low power consumption.

[0005] After the standard wafer has gone through each TSV process, the edge of the wafer becomes: inconsistent bonding, non-concentricity, edge wear, scribe grooves, sputtered metal or residual glue on the wafer surface, and wafer warping. Wafer notches are manifested as: notches that are not penetrating, damaged, filled or covered with metal or glue, and metal lines.

[0006] Therefore, when the wafer notch morphology changes dramatically due to the processing technology, the conventional method of identifying the notch by light intensity cannot meet the wafer pre-alignment accuracy requirements.

[0007] Currently, for wafers with drastic changes in wafer notch morphology, an aligner is generally used to achieve wafer exposure. The aligner does not consider the changes in the notch appearance of the wafer, and directly aligns the mark for exposure. The wafer pre-alignment method has problems such as low efficiency and low pre-alignment accuracy. The pre-alignment accuracy is easily affected by human interference and cannot achieve automated operation.

[0008] On this basis, a pre-alignment method and a pre-alignment device are proposed. The method is suitable for pre-alignment of wafers whose notch morphology has undergone drastic changes, helps to improve work efficiency, and helps to realize automated alignment operations. Summary of the invention

[0009] The invention provides a pre-alignment method and a pre-alignment device. The method is suitable for pre-alignment of wafers with drastic changes in notch morphology, helps to improve work efficiency, and helps to realize automated alignment operations.

[0010] The pre-alignment method comprises the following steps:

[0011] S1: Collect edge information of the wafer to obtain eccentricity, and adjust the wafer position to compensate for the wafer eccentricity;

[0012] S2: collecting image information of the scribe groove on the upper surface of the wafer, obtaining the actual direction of the scribe groove, and rotating the wafer to adjust the direction of the scribe groove of the wafer to a specified direction;

[0013] S3: Collect edge image information of the edge of the upper surface of the wafer within the illumination area, and match the edge image information with the notch of the template to obtain the notch position of the wafer to complete orientation.

[0014] Optionally, in step S3, lateral lighting is provided for the edge of the wafer, and the edge image information in the lighting area is collected.

[0015] Optionally, in step S3, the wafer is rotated so that the edge of the wafer passes through the illumination area in sequence, and the edge image information of the edge of the upper surface of the wafer located in the illumination area is collected.

[0016] Optionally, in step S3, edge image information collection includes the following steps:

[0017] S3-1: using the relative position relationship between the scribe groove and the notch in the template as a reference, obtaining several target positions where the wafer edge may have a notch, determining one of the target positions as an initial acquisition position, and making the initial acquisition position located within the illumination area;

[0018] S3-2: edge image information is collected and image matching is performed on the initial collection position. If the matching is successful, the wafer orientation is completed; if the matching is unsuccessful, step S3-3 is executed;

[0019] S3-3: rotating the wafer so that the next target position of the wafer is located within the illumination area, and collecting edge image information of the target position and performing image matching;

[0020] S3-4: If the matching is successful, the wafer orientation is completed; if the matching is unsuccessful, execute step S3-3.

[0021] Optionally, the target positions are spaced apart at a central angle of 90°.

[0022] Optionally, the designated direction is a direction in which the scribe groove is horizontally and vertically relative to the information collection unit.

[0023] Optionally, in step S3, image gradient information of the edge image information is calculated, and the gradient information is layered;

[0024] The amount of gradient information contained in each layer increases successively;

[0025] Arrange the layers from small to large according to the amount of gradient information contained therein, and match the gradient information of each layer with the gradient information of the template in turn;

[0026] If the gradient information of this layer matches the template, the gradient information of the next layer is matched;

[0027] If the gradient information of the current layer does not match the template, the edge image information of other positions at the edge of the wafer is re-collected.

[0028] Optionally, in step S1, illumination is provided to the edge of the wafer from bottom to top, and the light intensity at the edge of the wafer is detected from above the wafer to extract edge information.

[0029] Optionally, in step S2, the scribing groove image information corresponding to a cross scribing groove is extracted, and image integration is performed on the scribing groove image information along a straight line trajectory, and the actual direction of the scribing groove is obtained based on the peak value of the image integration.

[0030] The present invention also provides a pre-alignment device, comprising an information acquisition unit, a pre-alignment motion unit and an information processing unit;

[0031] The information acquisition unit is used to acquire edge information, scribe groove image information and edge image information of the wafer;

[0032] The information processing unit is used to process edge information and calculate the eccentricity of the wafer, to process the scribe groove image information to obtain the actual direction of the scribe groove of the wafer, and to process the edge image information to obtain the notch position of the wafer;

[0033] The pre-alignment motion unit is used to drive the wafer to move to compensate for the eccentricity and adjust the direction of the scribe groove of the wafer to a specified direction.

[0034] Optionally, the pre-alignment device further comprises a lateral light source;

[0035] The lateral light source is used to provide lighting to the edge of the wafer, and the information acquisition unit acquires the edge image information at the edge of the upper surface of the wafer that is located within the illumination area of ​​the lateral light source.

[0036] Optionally, the side light source provides oblique downward illumination toward the edge of the wafer.

[0037] Optionally, the pre-alignment device further includes a bottom light source, which is used to provide illumination for the edge of the wafer from bottom to top, and to obtain edge information of the wafer by identifying the light intensity at the edge of the wafer from top to bottom through the information acquisition unit.

[0038] Optionally, the pre-alignment motion unit comprises a vertical portion, a rotational portion and a translational portion;

[0039] The vertical portion is used to drive the wafer to move vertically;

[0040] The rotating part is used to drive the wafer to rotate along an axis perpendicular to its upper surface;

[0041] The translation part is used to drive the wafer to perform horizontal movement.

[0042] Optionally, the pre-alignment device also includes a point light source, which is used to provide illumination for the scribe grooves on the upper surface of the wafer from top to bottom, and obtain image information of the scribe grooves on the upper surface of the wafer within the illumination area of ​​the point light source through the information acquisition unit.

[0043] Optionally, the information acquisition unit includes an acquisition unit and a driving unit;

[0044] The collecting unit is used to collect edge information, scribe groove image information and edge image information of the wafer;

[0045] The driving part is used to drive the collecting part to move;

[0046] And / or, the driving unit is used to drive the lateral light source to move;

[0047] And / or, when the pre-alignment device includes a bottom light source, the driving unit is used to drive the bottom light source to move;

[0048] And / or, when the pre-alignment device includes a point light source, the driving unit is used to drive the point light source to move.

[0049] Configured in this way, the present invention uses the above-mentioned orientation method to collect edge information of the wafer to fit the edge of the wafer, obtain the position of the actual center of the circle, thereby obtaining the eccentricity, and then realizing the centering of the wafer. By collecting the information of the scribe groove on the surface of the wafer, the actual direction of the scribe groove is obtained, and the scribe groove is rotated to the specified direction to adjust the initial posture of the wafer. And based on the relative position relationship between the scribe groove and the notch in the actual template, several target positions where there may be notches at the edge of the wafer can be preliminarily determined, which is convenient for obtaining the notch position of the wafer. Then, the edge of the wafer is illuminated from top to bottom to collect edge image information in the illumination area, and the feature of the height difference at the edge of the wafer notch is used to extract the image feature for matching with the template to obtain the notch position of the wafer, thereby realizing wafer orientation. The alignment method is suitable for pre-alignment of wafers whose notch morphology has undergone drastic changes, improves the pre-alignment accuracy of wafers whose notch morphology has undergone drastic changes, improves the pre-alignment orientation pass rate of wafers, reduces orientation time, and helps to improve work efficiency. The alignment method does not require human participation, helps to realize automated alignment operations, and eliminates human interference factors during the alignment process, solving the problems of low pre-alignment efficiency, low pre-alignment accuracy and inability to realize automated operations for wafers whose notch morphology has undergone drastic changes in existing methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic structural diagram of a pre-alignment device according to an embodiment of the present invention;

[0051] Figure 2 A schematic diagram of the local structure of a pre-alignment device according to an embodiment of the present invention Figure 1 ;

[0052] Figure 3 A state diagram of wafer alignment according to an embodiment of the present invention;

[0053] Figure 4 Image integration data along the straight line trajectory in the scribe groove image information Figure 1 ;

[0054] Figure 5 Image integration data along the straight line trajectory in the scribe groove image information Figure 2 ;

[0055] Figure 6 This is the pre-alignment flow chart.

[0056] The reference numerals are as follows:

[0057] 10-information acquisition unit; 11-acquisition unit; 111-pre-alignment camera; 112-pre-alignment lens; 12-driving unit;

[0058] 20-pre-alignment motion unit; 21-vertical part; 22-rotation part; 23-translation part; 231-second adsorption structure;

[0059] 30-side light source;

[0060] 40- bottom light source;

[0061] 50-point light source;

[0062] 60-wafer. DETAILED DESCRIPTION

[0063] The pre-alignment method and pre-alignment device proposed in the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0064] As used in the invention, the singular forms "one", "a", and "the" include plural objects, the term "or" is usually used to include the meaning of "and / or", the term "several" is usually used to include the meaning of "at least one", and the term "at least two" is usually used to include the meaning of "two or more". In addition, the terms "first", "second", and "third" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", and "third" can explicitly or implicitly include one or at least two of the features. In addition, as used in the invention, "installed", "connected", "connected", and one element "set" to another element should be understood in a broad sense, usually only indicating that there is a connection, coupling, matching or transmission relationship between the two elements, and the connection, coupling, matching or transmission between the two elements can be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element can be in any orientation such as inside, outside, above, below or on one side of another element, unless the content clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the invention can be understood according to specific circumstances. In addition, directional terms such as above, below, up, down, upward, downward, left, right, etc. are used with respect to the exemplary embodiments as they are shown in the figures, with the upward or upper direction toward the top of the corresponding figure, and the downward or lower direction toward the bottom of the corresponding figure.

[0065] Wafer pre-alignment is an important module of the transmission subsystem. The transmission robot takes the wafer from the wafer storage, and after the wafer is centered and oriented by the wafer pre-alignment equipment, the wafer is loaded onto the worktable by the robot, and then moved to the alignment station for alignment. It is required that after the wafer is initially positioned by the pre-alignment equipment, the mark on the wafer can enter the alignment field of view. Since the wafer mark has a higher positional accuracy relative to the geometric features of the wafer, wafer pre-alignment is based on the geometric features of the outer circle of the wafer to achieve wafer centering, and based on geometric features such as edge notches or flat edges to achieve wafer orientation. The corresponding orientation method is generally to provide light to the edge of the wafer from top to bottom, and identify the notch by the difference in light and dark.

[0066] During the wafer processing, certain processes may cause changes in the appearance of the notches on the wafer.

[0067] Taking the TSV (through silicon via) process as an example, TSV is the latest technology that realizes interconnection between chips by making vertical conductions between chips and between wafers. It has the advantages of small package size, fast signal transmission and low power consumption.

[0068] After the standard wafer has gone through each TSV process, the edge of the wafer becomes: inconsistent bonding, non-concentricity, edge wear, scribe grooves, sputtered metal or residual glue on the wafer surface, and wafer warping. Wafer notches are manifested as: notches that are not penetrating, damaged, filled or covered with metal or glue, and metal lines. The wafer notch morphology has deteriorated dramatically.

[0069] Therefore, when the wafer notch morphology changes dramatically due to the processing technology, the conventional method of identifying the notch by light intensity cannot meet the wafer pre-alignment accuracy requirements.

[0070] Currently, for wafers with drastic changes in wafer notch morphology, an aligner is generally used to achieve wafer exposure. The aligner does not consider the changes in the notch appearance of the wafer, and directly aligns the mark for exposure. The wafer pre-alignment method has problems such as low efficiency and low pre-alignment accuracy. The pre-alignment accuracy is easily affected by human interference and cannot achieve automated operation.

[0071] On this basis, a pre-alignment method and a pre-alignment device are proposed. The method is suitable for pre-alignment of wafers whose notch morphology has undergone drastic changes, helps to improve work efficiency, and helps to realize automated alignment operations.

[0072] First reference Figure 1 The structure of the pre-alignment device is introduced.

[0073] The pre-alignment device includes an information acquisition unit 10 , a pre-alignment movement unit 20 , an information processing unit, a lateral light source 30 , a bottom light source 40 and a point light source 50 .

[0074] The information acquisition unit 10 is used to acquire edge information, scribe groove image information and edge image information of the wafer;

[0075] When it collects the edge information of the wafer, it can calculate the actual center of the wafer, and then calculate the eccentricity by comparing it with the reference center, providing a basis for centering.

[0076] The actual direction of the scribe groove can be obtained through the scribe groove image information, and then compared with the specified direction of the scribe groove, providing a basis for adjusting the direction of the scribe groove;

[0077] The edge image information is used to match the notch of the template. When the match is successful, the notch position of the wafer is obtained. At this time, the actual direction of the wafer notch can be obtained, and the orientation can be completed.

[0078] The information acquisition unit 10 includes a collection unit 11 and a driving unit 12;

[0079] The collecting unit 11 is used to collect edge information, scribe groove image information and edge image information of the wafer;

[0080] The acquisition unit 11 includes a pre-alignment camera 111 and a pre-alignment lens 112. The alignment camera may include a line array camera and a surface array camera.

[0081] In other alternative embodiments, the alignment camera may use only area array cameras or only line array cameras.

[0082] The acquisition unit can be used to acquire an image of the wafer 60 and obtain corresponding information based on the image, obtain edge information of the wafer through the light and dark contrast of the light intensity in the image, identify the notch on the edge of the wafer through the image, and identify the direction of the scribe groove through the image.

[0083] The collection unit 11 can be implemented using an existing camera. The collection principle and collection method are existing technologies and will not be described in detail here.

[0084] In other alternative embodiments, the acquisition unit 11 may further include a laser sensor, which may identify the edge contour of the wafer by identifying the position of the sudden change in distance from the wafer, and then fit the edge of the wafer to calculate the actual center of the circle.

[0085] The point light source 50 is mounted on the pre-alignment lens 112 and is used to provide illumination for the collection field of view of the collection unit 11. Since the collection field of view of the collection unit 11 is generally at the millimeter level, the point light source 50 can meet the illumination requirements of its collection field of view by using point illumination. The point light source 50 moves with the pre-alignment lens 112 and is used to provide illumination for the scribe groove on the upper surface of the wafer from top to bottom, and obtains the image information of the scribe groove on the upper surface of the wafer within the illumination area of ​​the point light source 50 through the collection unit 11.

[0086] Please continue to refer to Figure 1 As shown, the collecting part 11, the lateral light source 30, the bottom light source 40 and the point light source 50 are all installed on a bracket, and the bracket is driven to move by the driving part 12, so that the collecting part 11, the lateral light source 30, the bottom light source 40 and the point light source 50 can be driven away from or close to the pre-alignment motion unit 20.

[0087] In this embodiment, the side light source 30, the bottom light source 40 and the point light source 50 are all LED lamps. In other alternative embodiments, each light source can select an existing lighting device based on actual use requirements.

[0088] The driving unit 12 can drive each component to move horizontally. Specifically, the driving unit 12 can drive each component to move horizontally in the Y direction through a horizontal Y-direction motor, or it can drive each component to move horizontally in the Y direction through a hydraulic driving structure. The driving unit 12 can select an existing driving structure based on actual use requirements.

[0089] In other alternative embodiments, the driving unit 12 may further be provided with an X-direction driving motor based on usage requirements to drive each component to move horizontally along the X-direction. The specific driving direction of the driving unit 12 may be flexibly adjusted based on actual usage requirements.

[0090] In this embodiment, the driving unit 12 synchronously drives the collection unit 11, the side light source 30, the bottom light source 40 and the point light source 50 to move. In other alternative embodiments, the driving unit 12 may include multiple independent driving motors, and the collection unit 11, the side light source 30, the bottom light source 40 and the point light source 50 are each matched with a part of the driving motors to achieve independent driving of the above-mentioned components.

[0091] Please continue to refer to Figure 1 As shown, the side light source 30 is located above the bottom light source 40, and the side light source 30 and the bottom light source 40 are horizontally staggered. In one embodiment, the bottom light source 40 is more protruding in the horizontal direction.

[0092] The lateral light source 30 provides lighting from the side. The lateral light source 30 can provide lighting from the top tilted downward, or can provide lateral lighting in the horizontal direction, or can provide lighting from the bottom tilted upward. The present embodiment provides lighting from the top tilted downward, preferably tilted downward at 45°. When the edge of the wafer 60 is moved to just above the bottom light source 40 and continues to move toward the side of the lateral light source 30, the lateral light source 30 illuminates obliquely downward to the edge of the wafer 60. Since the lateral light source 30 illuminates obliquely downward, the edge of the wafer 60 does not need to be moved to just below the lateral light source 30, and therefore will not block the collection field of view of the collection unit 11. When the wafer 60 moves slightly outward, its edge is directly opposite to the bottom light source 40, and lighting can be provided vertically upward by the bottom light source 40, which also ensures that the lateral light source 30 will not block the collection field of view.

[0093] Of course, in other alternative embodiments, both the side light source 30 and the bottom light source 40 can illuminate the wafer obliquely, and their illumination directions can be adjusted so that they can provide lighting independently without interfering with each other or affecting the information collection of the information collection unit 10.

[0094] Please continue to refer to Figure 1 As shown, the pre-alignment motion unit 20 includes a vertical portion 21 , a rotation portion 22 and a translation portion 23 .

[0095] The rotating part 22 is arranged on the vertical part 21. The vertical part 21, the rotating part 22 and the translation part 23 can be driven by motors respectively.

[0096] The rotating part 22 has a first adsorption structure (not shown in the figure), and the first adsorption structure is, for example, a P-chuck suction cup. A vacuum groove may be provided on the upper surface of the first adsorption structure for adsorbing the wafer on the first adsorption structure. When the rotating part 22 rotates, the first adsorption structure and the wafer adsorbed on the first adsorption structure may be driven to rotate. The first adsorption structure realizes the transfer of wafers through a transfer robot, and the transfer method is that the transfer robot actively takes the wafer, that is, the transfer robot lifts and lowers to take and place the wafer. When the robot places the wafer in the first adsorption structure, it can be vacuum adsorbed by the first adsorption structure. When adsorbing the wafer, it only needs to control the vacuum switch on the first adsorption structure to achieve it.

[0097] In addition, the translation part 23 is also provided with a second adsorption structure 231, which is, for example, a C-chuck suction cup. The first adsorption structure passes through the second adsorption structure 231, and the first adsorption structure can move up and down with the vertical part 21, so the first adsorption structure can move up and down relative to the second adsorption structure 231. The second adsorption structure 231 can be driven by the translation part 23 to move horizontally.

[0098] The first adsorption structure and the second adsorption structure 231 cooperate with the rotating part 22 and the translation part 23 to drive the wafer to rotate and move horizontally, thereby realizing the pre-alignment function of automatically switching the size of 6-inch, 8-inch, 12-inch and other sized wafers.

[0099] When the wafer needs to be rotated to collect its edge position, the wafer can be adsorbed on the first adsorption structure. When the wafer needs to be driven to move horizontally to align the center, the first adsorption structure releases the vacuum. The vertical part 21 drives the first adsorption structure to lower, so that the first adsorption structure is lower than the second adsorption structure 231. The wafer is carried on the second adsorption structure 231, and the second adsorption structure 231 is driven to move horizontally by the translation part 23, thereby driving the wafer to move horizontally.

[0100] In this embodiment, the translation part 23 is used to drive the second adsorption structure 231 to move horizontally along the Y direction. In other alternative embodiments, the translation part 23 can drive the second adsorption structure 231 to move horizontally along the X direction and the Y direction, and the driving direction of the translation part 23 can be adaptively adjusted based on its alignment requirements.

[0101] Please continue to refer to Figure 1 and Figure 2 As shown, the bottom light source 40 is used to provide lighting for the edge of the wafer from bottom to top. A part of the light source irradiates upward through the edge of the wafer, and a part is blocked by the wafer, so that the edge position of the wafer has obvious light and dark contrast when observed from top to bottom. At this time, the image of the edge of the wafer is obtained from top to bottom through the information acquisition unit 10, and the edge information of the wafer is obtained by identifying the light intensity at the edge of the wafer. The actual center of the wafer is calculated by fitting the edge of the wafer. The edge of the wafer can be identified by the bottom light source 40 through the obvious light and dark contrast, and the corresponding actual center of the circle is calculated by fitting its edge.

[0102] In the case where the wafer notch morphology has changed dramatically, for example, for wafers processed by TSV process, there are reasons such as uneven glue coating and different glue coating materials near the wafer notch after glue coating. This causes the notch morphology to change dramatically. Therefore, when the bottom light source 40 is used for illumination, it is impossible to obtain obvious light and dark changes at the edge of the notch. At this time, the bottom light source 40 and the collection unit 11 cannot capture a clear notch from above, resulting in the inability to normally realize the pre-alignment directional function.

[0103] Therefore, a lateral light source 30 is added to provide illumination to the edge of the wafer from the side, and the edge image information of the edge of the upper surface of the wafer 60 located in the illumination area of ​​the lateral light source 30 is collected through the information acquisition unit 10. The lateral light source 30 is located on the edge side of the wafer, and the height difference at the wafer notch is used to extract the image features for directional processing. The lateral light source 30 is installed on the side of the wafer, and the illumination angle is preferably 45°, so that the information acquisition unit 10 can clearly capture the image of the notch.

[0104] The information processing unit is used to process edge information and calculate the eccentricity of the wafer, to process the scribe groove image information to obtain the actual direction of the scribe groove of the wafer, and to process the edge image information to obtain the notch position of the wafer; then cooperate with the pre-alignment motion unit 20 to drive the wafer to move to compensate for the eccentricity and adjust the direction of the scribe groove of the wafer to the specified direction.

[0105] The information processing unit usually includes at least one processor, which can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0106] The at least one processor can communicate with a plurality of peripheral devices via the bus subsystem. These peripheral devices may include a storage system, a user interface input device, a user interface output device, and a network interface.

[0107] The network interface provides an interface to an external network and / or other devices. The network interface includes one or more interfaces known in the art, such as LAN, WLAN, Bluetooth, other wired and wireless interfaces, and the like.

[0108] User interface input devices may include keyboards, pointing devices such as mice, trackballs, touch pads or graphics tablets, scanners, foot pedals, joysticks, touch screens embedded in displays, audio input devices such as voice recognition systems, microphones, and other types of input devices. In general, the term "input device" is intended to include a variety of conventional and proprietary devices and methods for inputting information into a controller.

[0109] The user interface output device may include a display subsystem, a printer, a fax machine, or a non-visual display such as an audio output device. The display subsystem may be a flat panel device, such as a liquid crystal display (LCD), a light emitting diode (LED) display, a touch screen display, etc. The display subsystem may also provide a non-visual display, such as via an audio output device. In general, the term "output device" is intended to include various conventional and proprietary devices and methods for outputting information from an information processing unit to a user.

[0110] The storage system can store basic programming and data structures that implement various functions of the present invention. For example, as described herein, databases and modules that implement the functions of the method of the present invention can be stored in the storage system. These software modules are usually executed by a processor. In a distributed environment, the software modules can be stored on multiple computer systems and executed by the processors of multiple computer systems. The storage system usually includes a memory subsystem and a file storage system. The memory subsystem usually includes multiple memories, including a main random access memory (RAM) for storing instructions and data during program execution and a read-only memory (ROM) in which fixed instructions are stored. The file storage subsystem provides permanent (non-volatile) storage for program and data files. The file storage system 60 may include a hard disk drive and associated removable media, a compact disk (CD) drive, an optical drive, a DVD, a solid-state memory, and / or other removable media. One or more of these drives may be located at a remote location on other connected computers at other sites connected to the information processing unit. The modules that implement the functions of the present invention can be stored by the file storage system.

[0111] The bus subsystem provides a means for the various components and subsystems of the information processing unit to communicate with each other as expected. The various subsystems and components of the information processing unit do not have to be in the same physical location, but can be distributed at various locations within the distributed network. The bus subsystem can be a single bus or multiple buses can be set up based on demand.

[0112] The information processing unit described above is intended to be used as an example only to illustrate only one embodiment of the present invention. Due to the ever-changing nature of computers and networks, in other alternative embodiments, the information processing unit may also have certain differences from the configuration of the information processing unit described above, which will not be repeated here.

[0113] When the information processing unit processes the image information and calculates the eccentricity of the wafer, the edge information can be an image, and the information processing unit can calculate the gradient information through the image, thereby identifying the edge contour of the wafer and then calculating its actual center. In addition, the edge information can also be the distance from the upper surface of the wafer. When the edge position of the wafer is detected, the detected distance will suddenly change due to the sudden change in the height of the wafer, and the edge of the wafer is detected by the sudden change in distance.

[0114] When the information processing unit processes the scribe groove image information to obtain the actual direction of the scribe groove of the wafer, the scribe groove image information is the image of the scribe groove on the surface of the wafer taken, and then the actual direction of the scribe groove is obtained by calculation. According to the camera field of view, one cross-scribed groove can be captured in the image at one time, and the image is integrated along a straight line trajectory in a small area in the scribe groove image information, and the actual direction of the scribe groove is obtained based on the peak value of the image integration. The integration can be performed, for example, by integrating pixels or gradients. Mathematical integration has a low-frequency filtering effect. Compared with mathematical differentiation, mathematical integration can well suppress high-frequency signals of the image, so that interference information will not have a significant impact on the recognition result. In this way, the uncertainty caused by the previous reliance on high-frequency signals (noise edges) of the image using Hough transform can be better solved.

[0115] Please refer to Figure 4 and Figure 5 As shown, Figure 4 The integrated data diagram represents the recognition of the direction of one of the cross-line grooves. Figure 5 Integrate the data graph for another scribe groove direction identification.

[0116] The approximate direction of the scribe groove can be identified through image acquisition, and then it is predetermined to be integrated on a straight line trajectory perpendicular to the scribe groove to obtain the precise direction.

[0117] Figure 4 and Figure 5 In the figure, the horizontal axis represents the number of subdivisions made by angle, and the number of subdivisions is subdivided within the angle range roughly perpendicular to the scribe groove to accurately determine the direction of the scribe groove. The number of subdivisions calibrates the direction of the straight line trajectory, and the vertical axis represents the pixel accumulation value. Since the position of the scribe groove in the scribe groove image information has a darker color, its gradient or pixel is darker. For example, there are multiple rows of pixel information in the integration area, and the direction of each row is perpendicular to the integration trajectory. If each row is parallel to the direction of the scribe groove, the pixel points in each row are almost all located in the scribe groove, and the pixel superposition after integration along the direction perpendicular to the scribe groove will reach a peak value. If the rows are not parallel to the scribe groove, a part of the pixel points in each row falls outside the scribe groove, so the pixels after integration along the trajectory perpendicular to the rows will not reach a peak value.

[0118] like Figure 4As shown in , the pixel peak is obtained at a position where the angle subdivision number is slightly less than 400, and the straight line trajectory corresponding to this peak is perpendicular to one of the scribed grooves. Therefore, the direction of the scribed groove can be determined. Figure 5 As shown in FIG. 1 , a pixel peak is obtained at a position where the angle subdivision number is slightly greater than 400, and the straight line trajectory corresponding to this peak is perpendicular to one of the scribed grooves. Therefore, the direction of the scribed groove can be determined.

[0119] After obtaining the direction of the scribe groove, it can be compared with the specified direction. When the error between the two is greater than a threshold, the rotation direction required for the wafer to rotate when the scribe groove rotates to the specified direction is calculated. The wafer can then be rotated to adjust the scribe groove to the specified direction.

[0120] When the information processing unit processes the edge image information to obtain the notch position of the wafer, it selects a template image with the notch of the wafer of this specification from the edge data set of the template image, and then matches the edge image information with the template image. The gradient and direction of the image are found in the edge image information, and the edge information is extracted using non-maximum suppression, which can filter out those pixels with insufficient gradients, and the dual threshold algorithm is used to detect and connect the edges, which can limit the image within a certain grayscale range to be the real notch information.

[0121] When matching images, the image gradient information of the edge image information is calculated and the gradient information is layered;

[0122] The amount of gradient information contained in each layer increases successively;

[0123] Arrange each layer from small to large according to the amount of gradient information it contains, and match the gradient information of each layer with the gradient information of the template in turn; that is, similar to pyramid sampling of edge image information, perform coarse matching at the top of the pyramid, locate a position value, and then finely locate layer by layer downward. If the gradient information of this layer matches the template, match the gradient information of the next layer; if the gradient information of this layer does not match the template, re-collect edge image information at other positions on the edge of the wafer. The matching calculation method can, for example, be to calculate the average dot product of the gradient vectors corresponding to the edge points of the template and the edge image information.

[0124] Combination Figures 1 to 3 The pre-alignment device, combined with Figure 6 As shown, the alignment process is as follows:

[0125] After the pre-alignment starts, the transfer robot transfers the wafer to the first adsorption structure, the vertical part 21 moves to the pre-alignment station, the first adsorption structure adsorbs the wafer, the bottom light source 40 is turned on, the rotating part 22 rotates the wafer at a uniform speed for one circle, the upper control information acquisition unit 10 starts image acquisition through the area array camera, collects the edge of the wafer, and the information processing unit calculates the eccentricity of the wafer. Then the vertical part 21 is lowered to the junction with the translation part 23. The first adsorption structure (P-chuck) releases the vacuum, and the second adsorption structure 231 (C-chuck) opens the vacuum to adsorb the wafer. After the vertical part 21 drives the first adsorption structure to lower to the low position of the junction, the translation part 23 moves horizontally, and the translation part 23 drives the second adsorption structure 231 (C-chuck) to move horizontally, thereby compensating for the eccentricity of the wafer. After compensation is completed, the vertical part 21 rises to the junction position of the translation part 23, the second adsorption structure 231 (C-chuck) releases the vacuum to release the wafer, the first adsorption structure (P-chuck) opens the vacuum to adsorb the wafer, the vertical part 21 rises to the pre-alignment position, the rotating part 22 rotates one circle with the wafer, the information acquisition unit 10 collects information, and calculates the residual deviation of the eccentricity through the information processing unit.

[0126] If the residual meets the error window index requirement, the driving unit 12 drives the collecting unit 11 to move toward the pre-alignment motion unit 20, so that the collecting unit 11 moves to the inner side of the edge of the wafer. At the same time, the upper layer controls the information collecting unit 10 to shoot the scribe groove inside the upper surface of the wafer through the linear array camera, calculates the actual direction of the scribe groove, and calculates the required rotation angle of the wafer through the actual direction and the set direction. Then the rotating unit 22 rotates the wafer to compensate for the angle, so that the scribe groove rotates to the specified direction. In one embodiment, the specified direction is the direction in which the scribe groove is horizontally perpendicular to the information collecting unit 10. As shown in the figure, the scribe groove is generally in the shape of a cross, that is, the specified direction of the scribe groove adjustment is that the horizontal groove is parallel to the information collecting unit 10, and the longitudinal groove is perpendicular to the information collecting unit 10.

[0127] like Figure 3 Then the driving unit 12 drives the collecting unit 11 to move away from the pre-alignment moving unit 20, so that the collecting unit 11 moves to the edge of the wafer. The lateral light source 30 is turned on, and the rotating unit 22 drives the wafer to rotate. The collecting unit 11 collects the edge graphic information of the wafer, and performs image matching to identify the direction of the notch.

[0128] In the process of collecting edge image information at the edge of the wafer, since the edge of the wafer is circular and the scribe groove of the wafer is a grid structure, the direction of the scribe groove is known at this time, and the relative position relationship between the wafer notch and the scribe groove can be known through the template. Therefore, the target position where the notch exists on the periphery of the wafer can be roughly calculated, and the geometric template matching algorithm is used to calculate at which angle of the wafer the notch exists to complete the orientation function. There are four target positions where the notch exists on the periphery of the wafer, so it is only necessary to collect images at a maximum of four target positions to identify the location of the notch.

[0129] First, the first target position of the wafer edge is rotated to the field of view of the acquisition unit 11 to collect edge image information. If the match is not successful, the wafer is rotated 90° to continue the acquisition and matching. If the match is unsuccessful, it is continued to be rotated 90° and 180° relative to the initial position, and so on. If the match is unsuccessful, it is continued to be rotated 90° and 270° relative to the initial position until all target positions are collected.

[0130] If no gap is found at the above target positions, edge image information acquisition and matching can be performed within a range of ±10 mrad near these target positions to solve the asymmetry between the gap and the scribe groove.

[0131] By extension, as long as the pre-alignment component has mechanisms such as the vertical portion 21, the rotating portion 22, the translation portion 23 and the information collection unit, and has a lateral light source 30 and a bottom light source 40, it can achieve pre-alignment of wafers with drastic changes in notch morphology.

[0132] The present invention also provides a pre-alignment method, comprising the following steps:

[0133] S1: Collect edge information of the wafer, obtain the eccentricity of the actual center of the circle relative to the reference center of the circle, and adjust the wafer position to compensate for the wafer eccentricity.

[0134] Specifically, the bottom light source 40 is used to provide illumination to the edge of the wafer from bottom to top, and the information acquisition unit 10 detects the light intensity at the edge of the wafer from above the wafer, extracts the edge information, and calculates the actual center of the circle and then the eccentricity through the information processing unit. The acquisition process and information processing process are described in detail above and will not be repeated here.

[0135] S2: collecting image information of the scribe groove on the upper surface of the wafer, obtaining the actual direction of the scribe groove, and rotating the wafer to adjust the direction of the scribe groove of the wafer to a specified direction;

[0136] During the extraction process, the point light source 50 can be used to provide local illumination, extract the scribe groove image information corresponding to a cross scribe groove, and perform image integration along the straight line trajectory in the scribe groove image information, and obtain the actual direction of the scribe groove based on the peak value of the image integration. The integration can be performed, for example, by integrating pixels or gradients. After obtaining the direction of the scribe groove, it can be compared with the specified direction. When the error between the two is greater than the threshold, the rotation direction required by the wafer when the scribe groove rotates to the specified direction is calculated, and the wafer can be rotated to adjust so that the scribe groove rotates to the specified direction.

[0137] S3: collecting edge image information at the edge of the upper surface of the wafer, matching the edge image information with the notch of the template to obtain the notch position of the wafer to complete orientation.

[0138] Provide lateral lighting for the edge of the wafer. Preferably, the lateral light source illuminates the edge of the wafer obliquely downward from the upper side, rotate the wafer so that the edge of the wafer passes through the illumination area in sequence, and collect the edge image information of the edge of the upper surface of the wafer within the illumination area.

[0139] Furthermore, since the direction of the scribe groove is known, the grid structure of the scribe groove, and the relative positional relationship between the direction of the scribe groove and the notch can be known through the template.

[0140] Therefore, four target positions where the notch may exist can be obtained at the edge of the wafer, and the center angles of the target positions are 90° apart.

[0141] Therefore, it is only necessary to collect edge image information in the above four target positions, and take one of the target positions as the collection target to collect edge image information. If the matching is unsuccessful, the wafer is rotated in sequence so that the next target position passes through the information collection unit 10 .

[0142] In summary, edge image information collection can be summarized into the following steps:

[0143] S3-1: Using the position of the scribe groove relative to the notch in the template as a reference, obtain several target positions where the wafer edge may have a notch, determine one of the target positions as the initial acquisition position, and make the initial acquisition position located within the illumination area. Since the direction of the scribe groove is known at this time, and the relative position relationship between the notch and the scribe groove of the wafer can be known through the template. Therefore, the target position where the notch exists on the periphery of the wafer can be roughly calculated. Since the edge of the existing wafer is circular and the scribe groove of the wafer is a grid structure, based on the existing wafer structure and the relative position relationship between the notch and the scribe groove collected in the template, it can be known that there are four target positions where the notch exists on the periphery of the wafer. Therefore, it is only necessary to perform image acquisition at a maximum of four target positions to identify the location of the notch.

[0144] S3-2: edge image information is collected and image matching is performed on the initial collection position. If the matching is successful, the wafer orientation is completed; if the matching is unsuccessful, step S3-3 is executed;

[0145] S3-3: rotating the wafer so that the next target position of the wafer is located within the illumination area, and collecting edge image information of the target position and performing image matching;

[0146] S3-4: If the matching is successful, the wafer orientation is completed; if the matching is unsuccessful, execute step S3-3.

[0147] Furthermore, in the template matching process, image gradient information of edge image information is calculated, and the gradient information is layered;

[0148] The amount of gradient information contained in each layer increases successively;

[0149] Arrange each layer from small to large according to the amount of gradient information it contains, and match the gradient information of each layer with the gradient information of the template in turn; that is, similar to pyramid sampling of edge image information, perform coarse matching at the top of the pyramid, locate a position value, and then finely locate layer by layer downward. If the gradient information of this layer matches the template, match the gradient information of the next layer; if the gradient information of this layer does not match the template, re-collect edge image information at other positions on the edge of the wafer. The matching calculation method can, for example, be to calculate the average dot product of the gradient vectors corresponding to the edge points of the template and the edge image information.

[0150] The above-mentioned orientation method collects the edge information of the wafer to fit the edge of the wafer, obtains the position of the actual center of the circle, and thereby obtains the eccentricity, thereby realizing the centering of the wafer. By collecting the information of the scribe groove on the surface of the wafer, the actual direction of the scribe groove is obtained, and the scribe groove is rotated to the specified direction to adjust the initial posture of the wafer. And based on the relative position relationship between the scribe groove and the notch in the actual template, several target positions where the notch may exist at the edge of the wafer can be preliminarily determined, which facilitates the acquisition of the notch position of the wafer. Then, the edge of the wafer is illuminated from top to bottom to collect edge image information in the illumination area, and the feature of the height difference at the edge of the wafer notch is used to extract the image feature for matching with the template to obtain the notch position of the wafer, thereby realizing wafer orientation. The alignment method is suitable for pre-alignment of wafers whose notch morphology has undergone drastic changes, improves the pre-alignment accuracy of wafers whose notch morphology has undergone drastic changes, improves the pre-alignment orientation pass rate of wafers, reduces orientation time, and helps to improve work efficiency. The alignment method does not require human participation, helps to realize automated alignment operations, and eliminates human interference factors during the alignment process, solving the problems of low pre-alignment efficiency, low pre-alignment accuracy and inability to realize automated operations for wafers whose notch morphology has undergone drastic changes in existing methods.

[0151] The pre-alignment method has been described in detail in conjunction with the pre-alignment device in the above-mentioned introduction to the structure of the pre-alignment device, and will not be elaborated on here.

[0152] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0153] The above description is only a description of the preferred embodiments of the invention, and is not intended to limit the scope of the invention. Any changes or modifications made by a person of ordinary skill in the art based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A pre-alignment method, characterized in that: The steps include: S1: Collect edge information of the wafer to obtain eccentricity, and adjust the wafer position to compensate for the wafer eccentricity; S2: collecting image information of the scribe groove on the upper surface of the wafer, obtaining the actual direction of the scribe groove, and rotating the wafer to adjust the direction of the scribe groove of the wafer to a specified direction; S3: Collect edge image information of the edge of the upper surface of the wafer within the illumination area, and match the edge image information with the notch of the template to obtain the notch position of the wafer to complete orientation.

2. The pre-alignment method according to claim 1, characterized in that: In step S3, lateral lighting is provided for the edge of the wafer, and the edge image information in the lighting area is collected.

3. The pre-alignment method according to claim 1, characterized in that: In step S3, the wafer is rotated so that the edge of the wafer passes through the illumination area in sequence, and the edge image information of the edge of the upper surface of the wafer located in the illumination area is collected.

4. The pre-alignment method according to claim 1, characterized in that: In step S3, edge image information collection includes the following steps: S3-1: using the relative position relationship between the scribe groove and the notch in the template as a reference, obtaining several target positions where the wafer edge may have a notch, determining one of the target positions as an initial acquisition position, and making the initial acquisition position located within the illumination area; S3-2: edge image information is collected and image matching is performed on the initial collection position. If the matching is successful, the wafer orientation is completed; if the matching is unsuccessful, step S3-3 is executed; S3-3: rotating the wafer so that the next target position of the wafer is located within the illumination area, and collecting edge image information of the target position and performing image matching; S3-4: If the matching is successful, the wafer orientation is completed; if the matching is unsuccessful, execute step S3-3.

5. The pre-alignment method according to claim 4, characterized in that: The target positions are spaced apart at a central angle of 90°.

6. The pre-alignment method according to claim 1, characterized in that: The specified direction is the direction in which the scribe groove is horizontal and vertical relative to the information collection unit.

7. The pre-alignment method according to claim 1, characterized in that: In step S3, the image gradient information of the edge image information is calculated, and the gradient information is layered; The amount of gradient information contained in each layer increases successively; Arrange the layers from small to large according to the amount of gradient information contained therein, and match the gradient information of each layer with the gradient information of the template in turn; If the gradient information of this layer matches the template, the gradient information of the next layer is matched; If the gradient information of the current layer does not match the template, the edge image information of other positions at the edge of the wafer is re-collected.

8. The pre-alignment method according to claim 1, characterized in that: In step S1, illumination is provided to the edge of the wafer from bottom to top, and the light intensity at the edge of the wafer is detected from above the wafer to extract edge information.

9. The pre-alignment method according to claim 1, characterized in that: In step S2, the scribing groove image information corresponding to a cross scribing groove is extracted, and image integration is performed along a straight line trajectory in the scribing groove image information, and the actual direction of the scribing groove is obtained based on the peak value of the image integration.

10. A pre-alignment device, characterized in that: It includes an information acquisition unit, a pre-alignment motion unit and an information processing unit; The information acquisition unit is used to acquire edge information, scribe groove image information and edge image information of the wafer; The information processing unit is used to process edge information and calculate the eccentricity of the wafer, to process the scribe groove image information to obtain the actual direction of the scribe groove of the wafer, and to process the edge image information to obtain the notch position of the wafer; The pre-alignment motion unit is used to drive the wafer to move to compensate for the eccentricity and adjust the direction of the scribe groove of the wafer to a specified direction.

11. The pre-alignment device according to claim 10, characterized in that: The pre-alignment device also includes a side light source; The lateral light source is used to provide lighting to the edge of the wafer, and the information acquisition unit acquires the edge image information at the edge of the upper surface of the wafer that is located within the illumination area of ​​the lateral light source.

12. The pre-alignment device according to claim 11, characterized in that The side light source provides oblique downward illumination to the edge of the wafer.

13. The pre-alignment device according to claim 10, characterized in that: The pre-alignment device also includes a bottom light source, which is used to provide lighting for the edge of the wafer from bottom to top, and to obtain edge information of the wafer by identifying the light intensity at the edge of the wafer from top to bottom through the information acquisition unit.

14. The pre-alignment device according to claim 10, characterized in that: The pre-alignment motion unit comprises a vertical portion, a rotation portion, and a translation portion; The vertical portion is used to drive the wafer to move vertically; The rotating part is used to drive the wafer to rotate along an axis perpendicular to its upper surface; The translation part is used to drive the wafer to perform horizontal movement.

15. The pre-alignment device according to claim 10, characterized in that: The pre-alignment device also includes a point light source, which is used to provide illumination for the scribe groove on the upper surface of the wafer from top to bottom, and obtain image information of the scribe groove on the upper surface of the wafer within the illumination area of ​​the point light source through an information acquisition unit.

16. The pre-alignment device according to any one of claims 10 to 15, characterized in that: The information acquisition unit includes an acquisition unit and a driving unit; The collecting unit is used to collect edge information, scribe groove image information and edge image information of the wafer; The driving part is used to drive the collecting part to move; And / or, the driving unit is used to drive the lateral light source to move; And / or, when the pre-alignment device includes a bottom light source, the driving unit is used to drive the bottom light source to move; And / or, when the pre-alignment device includes a point light source, the driving unit is used to drive the point light source to move.

Images