Device and system for wafer bonding alignment detection

Abstract

The invention relates to a device and a system for wafer bonding alignment detection. The invention provides a chuck for wafer bonding alignment detection in one aspect, and the chuck comprises a chuck body which is provided with an upper surface and a lower surface opposite to the upper surface; the air channel is arranged on the upper surface and is used for providing adsorption force to adsorb a wafer to be detected on the upper surface, and the air channel is sunken downwards from the upper surface and is provided with a bottom surface and a side wall inclined relative to the bottom surface.

Description

Technical Field

[0001] The present application relates generally to the field of semiconductor equipment manufacturing, and more particularly to an apparatus and system for wafer bonding alignment detection. Background Art

[0002] Wafer bonding alignment detection is usually illuminated by an infrared light source. In some designs, the carrier (such as a chuck) that carries the wafer to be inspected is made of a material that is transparent to infrared light. The infrared light can pass through the carrier to image the marks on the wafer. The wafer can be adsorbed on the carrier by forming a vacuum negative pressure in the air channel provided on the carrier so that the wafer has an acceptable flatness, thereby improving the detection accuracy and detection efficiency. However, the setting of the air channel may affect the strength and transmittance of the carrier itself. Therefore, it is necessary to provide an improved solution for wafer bonding alignment detection. Summary of the invention

[0003] According to one aspect of the present application, a chuck for wafer bonding alignment detection includes: a chuck body having an upper surface and a lower surface opposite to the upper surface; and an air channel, which is arranged on the upper surface and is used to provide an adsorption force to adsorb the wafer to be inspected on the upper surface, wherein the air channel is recessed downward from the upper surface and has a bottom surface and a side wall inclined relative to the bottom surface.

[0004] In some embodiments, the airway includes annular airways and radial airways.

[0005] In some embodiments, the air channel includes an annular air channel and three radial air channels, and the three radial air channels divide the area enclosed by the annular air channel into three equal parts.

[0006] In some embodiments, the bottom surface is parallel to the upper surface.

[0007] In some embodiments, the cross-section of the airway is generally a trapezoid that is wider at the top and narrower at the bottom.

[0008] In some embodiments, a ratio of a width of an upper end of the airway to a depth of the airway is greater than or equal to 5.

[0009] In some embodiments, an R angle is provided at a transition point between the upper surface and the side wall, and / or an R angle is provided at a transition point between the side wall and the bottom surface.

[0010] In some embodiments, the R angle is greater than 0.1.

[0011] In some embodiments, an angle between the bottom surface and the side wall is greater than or equal to 110 degrees and less than 180 degrees.

[0012] In some embodiments, the air channel is cold blasted.

[0013] According to another aspect of the present application, a system for wafer bonding alignment detection includes: a chuck according to any of the above embodiments, the chuck is used to carry a wafer to be inspected; a light source, which is configured to emit illumination light; a lens assembly, which is configured to guide the illumination light to the chuck; and an imaging assembly, which is configured to receive the illumination light passing through the chuck and the wafer to image the wafer.

[0014] According to another aspect of the present application, a method for manufacturing a chuck for wafer bonding alignment detection includes: forming an air channel on the chuck, wherein the air channel is recessed downward from the upper surface of the chuck and has a bottom surface and a side wall inclined relative to the bottom surface; and cold polishing the surface of the air channel.

[0015] The details of one or more examples of the present application are set forth in the following drawings and description. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The disclosure in this specification refers to and includes the following figures:

[0017] Figure 1 is a schematic diagram of a system for wafer bonding alignment detection according to an embodiment of the present application.

[0018] Figure 2 yes Figure 1 A top view of a chuck used to hold a wafer in the system shown.

[0019] Figure 3a It is a schematic diagram of a chuck airway.

[0020] Figure 3b is a schematic diagram of a chuck airway according to an embodiment of the present application.

[0021] Figure 4 It is a partial cross-sectional view near the chuck air passage according to an embodiment of the present application.

[0022] Figure 5a to Figure 5c It is a schematic diagram of the light path when the illumination light is irradiated on different chuck adsorption surfaces.

[0023] Figures 6a to 6c are respectively corresponding to Figure 5a to Figure 5c Imaging effect diagram of the optical path shown.

[0024] Figure 7 is a flow chart of an exemplary method for manufacturing a chuck for wafer bonding alignment detection according to an embodiment of the present application.

[0025] As a matter of practice, the various features illustrated in the drawings may not be drawn to scale. Therefore, the sizes of the various features may be arbitrarily enlarged or reduced for clarity. The shapes of the components illustrated in the drawings are exemplary shapes only and do not define the actual shapes of the components. In addition, the embodiments illustrated in the drawings may be simplified for clarity. Therefore, the drawings may not illustrate all components of a given device or apparatus. Finally, the same reference numerals may be used throughout the specification and the drawings to represent the same features. DETAILED DESCRIPTION

[0026] In order to better understand the spirit of the present application, it is further described below in conjunction with some embodiments of the present application.

[0027] The words "in one instance" or "according to one instance" used in this specification do not necessarily refer to the same specific embodiment, and the words "in other (some / certain) instances" or "according to other (some / certain) instances" used in this specification do not necessarily refer to different specific embodiments. The purpose is, for example, that the claimed subject matter includes a combination of all or part of the exemplary specific embodiments. The meaning of "upper" and "lower" referred to herein is not limited to the relationship directly presented in the drawings, which may include other clear corresponding relationships, such as "left" and "right", or the opposite of "upper" and "lower". The term "connected" or "coupled" referred to herein should be understood to cover "directly connected" and "connected via one or more intermediate components". The names of the various components used in this specification are for illustrative purposes only and do not have a limiting effect. Different manufacturers may use different names to refer to components with the same function.

[0028] Various embodiments of the present application are discussed in detail below. Although specific implementations have been discussed, it should be understood that these embodiments are for illustrative purposes only. Those skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the present application. The implementation of the present application may not necessarily include all components or steps in the embodiments described in the specification, and the execution order of each step may also be adjusted according to actual application.

[0029] Figure 1 A system 100 for wafer bonding alignment detection according to an embodiment of the present application is shown. The system 100 has a light source 101, a lens assembly 102, a chuck 103 and an imaging assembly 107.

[0030] Light source 101 may emit illumination light toward lens assembly 102 . In some embodiments, light source 101 may emit infrared light. In other embodiments, light source 101 may emit visible light or other types of illumination light. The illumination light from light source 101 is guided to chuck 103 via lens assembly 102 .

[0031] The chuck 103 is made of a material that can transmit illumination light, such as a glass material. The chuck 103 has an upper surface 111 and a lower surface 121 opposite to the upper surface 111. The chuck 103 has an airway (for example, on the upper surface 111), which is connected to the negative pressure device ( Figure 1 The negative pressure device enables the airway to provide an adsorption force (e.g., forming a vacuum negative pressure in the airway) by, for example, evacuating the airway, so that the wafers to be inspected (e.g., wafers 104 and 105) are adsorbed on the upper surface 111 of the chuck 103. The system 100 can use common negative pressure devices in the art (e.g., vacuum pumps), which will not be described in detail here.

[0032] The illumination light may further pass through the chuck 103, the wafer 105, and the wafer 104, and finally be received by the imaging component 107. The lower surface of the wafer 104 and the upper surface of the wafer 105 may be bonded to form a bonding surface 106. The lower surface of the wafer 104 has a mark 108, and the upper surface of the wafer 105 has a mark 109. The imaging component 107 images the marks 108 and 109 to detect whether the bonding surface 106 between the wafer 104 and the wafer 105 meets the standard (for example, detect whether the marks 108 and 109 are aligned).

[0033] In some embodiments of the present application, the chuck 103 is fixed, and the light source 101, the lens assembly 102, and the imaging assembly 107 can be synchronously moved relative to the chuck 103 to detect different positions of the bonded wafer. In other embodiments, the chuck 103 is movable. Figure 1 The device or component for moving the light source 101, the lens assembly 102, the imaging assembly 107 or the chuck 103 is not shown. Those skilled in the art should understand that various devices or components can be used to fix the light source 101, the lens assembly 102, the imaging assembly 107 or the chuck 103 or to move these components without departing from the spirit and scope of protection of the present application. It should be understood that various suitable light sources, lens assemblies and imaging assemblies can be used, which does not affect the implementation of the present invention.

[0034] exist Figure 1 In the illustrated system 100, the light source 101 and the lens assembly 102 are located below the chuck 103, the bonded wafer is adsorbed on the upper surface 111 of the chuck 103, and the imaging assembly 107 is located above the bonded wafer, and the illumination light passes through the bonded wafer from bottom to top. In other embodiments of the present application, the imaging assembly 107 of the system 100 may be located below the chuck 103, and the light source 101 and the lens assembly 102 may be located above the bonded wafer, and the illumination light passes through the bonded wafer from top to bottom.

[0035] Figure 2 yes Figure 1A top view of the chuck 103 in the illustrated system 100 shows specific details of the upper surface 111 of the chuck 103. The upper surface 111 of the chuck 103 is a generally flat surface and has a plurality of grooves sunken downward from the surface, which constitute air channels on the upper surface 111 of the chuck 103. The air channels on the chuck 103 may include an annular air channel 201 and a radial air channel 202. The annular air channel 201 takes the center position of the chuck 103 as the center of the circle. The radial air channel 202 is a straight air channel extending from the center position of the chuck 103 to the edge position of the chuck 103. The annular air channel 201 may be connected to the radial air channel. Figure 2 In the example, the chuck 103 has an annular air channel 201 and three radial air channels 202, and the three radial air channels 202 divide the area enclosed by the annular air channel 201 into three equal parts. It should be understood that other numbers of annular air channels (for example, multiple concentric annular air channels with different diameters) and other numbers of radial air channels can be set without departing from the spirit and scope of protection of the present application, and the present application does not intend to limit the specific distribution of the annular air channels and radial air channels. As mentioned above, these air channels can be connected to a negative pressure device to adsorb the wafer on the upper surface 111 of the chuck 103 by providing negative pressure.

[0036] The air channels on the chuck need to be designed to provide a standard suction force for the wafer. One solution is to increase the number of air channels on the chuck so that the wider the air channels are, the flatter the wafer can be sucked. Figure 2 Taking the chuck 103 as an example, additional annular air channels and / or radial air channels can be added, and these additional air channels are evenly distributed on the upper surface 111 of the chuck 103 together with the original annular air channels 201 and radial air channels 202, thereby increasing the adsorption force of the chuck 103 and the flatness of the adsorbed wafer. However, the increase in the number of air channels will reduce the overall strength of the chuck and affect the uniformity of the light transmission of the chuck.

[0037] Another approach is to modify the shape of the airway.

[0038] Conventional airways usually have Figure 3a For simplicity and clarity, Figure 3a Only the suction surface (eg, upper surface) of the chuck and the cross-sectional outline of one air channel 301 are shown, while other parts of the chuck in the cross-sectional view are omitted. Figure 3aThe air channel 301 shown has two side walls 310 and a bottom surface 311, the two side walls 310 are perpendicular to the bottom surface 311, and the bottom surface 311 is substantially parallel to the upper surface of the chuck. In other words, the cross-section of the air channel 301 is substantially rectangular. In the cross-sectional view, the horizontal distance between the two side walls 310 defines the width W1 of the air channel 301, and the vertical distance between the upper surface of the chuck and the bottom surface 311 of the air channel 301 defines the depth D1 of the air channel 301. The ratio of the width W1 and the depth D1 of the air channel 301 is generally about 1. In order to obtain a standard adsorption force, the depth D1 of the air channel 301 is generally deep, which reduces the overall strength of the chuck and makes the light transmittance of the chuck uneven.

[0039] Therefore, it is necessary to improve the shape of the air channel so as to meet the chuck adsorption force requirement without increasing the number of air channels while ensuring that the chuck has sufficient strength and uniform light transmittance.

[0040] Some embodiments of the present application provide an airway that can meet the above requirements. Figure 3b A schematic diagram of an airway according to an embodiment of the present application is shown. For simplicity and clarity, Figure 3b Only the suction surface of the chuck is shown (eg Figure 1 and Figure 2 The top surface 111 of the chuck 103 and the cross-sectional outline of one gas channel 302 are shown, while other parts of the chuck in the cross-sectional view are omitted.

[0041] Figure 3b The air channel 302 shown has two side walls 320 and a bottom surface 321. The two side walls 320 are inclined in a direction away from the bottom surface 321, so that the opening width of the air channel 302 at the upper surface 111 of the chuck is greater than the width of the bottom surface 321. The bottom surface 321 can be substantially parallel to the upper surface 111 of the chuck. In other words, Figure 3a Unlike the airway 301 shown, the cross section of the airway 302 is generally a trapezoid that is wide at the top and narrow at the bottom. The two side walls 320 are inclined surfaces and the angle α formed relative to the bottom surface 321 is greater than 90 degrees. In some embodiments of the present application, the angle α is greater than or equal to 110 degrees and less than 180 degrees. Figure 3b In the cross-sectional view shown, the horizontal distance between the intersection of the two side walls 320 and the upper surface 111 of the chuck defines the width W2 of the upper end of the airway 302 (i.e., the opening width of the airway 302 at the upper surface 111 of the chuck, also referred to as the width of the airway 302), and the vertical distance between the upper surface 111 of the chuck and the bottom surface 321 of the airway 302 defines the depth D2 of the airway 302.

[0042] and Figure 3aCompared with the air channel 301 shown in the figure, under the condition of providing the same adsorption force, the depth D2 of the air channel 302 can be significantly smaller than the depth D1, and the width W2 can be significantly larger than the width W1. In some embodiments of the present application, the ratio of the width W2 of the air channel 302 to the depth D2 is greater than or equal to 5. Obviously, the reduction of the air channel depth can enhance the strength of the chuck. On the other hand, compared with the vertical side wall 310, the inclined side wall 320 can improve the sudden change of the refraction of the illumination light at the turning point, thereby improving the uniformity of the light transmission of the chuck.

[0043] Further, such as Figure 3b As shown, a rounded corner (i.e., R angle) may be provided at the turning point between the upper surface 111 of the chuck and the side wall 320 of the airway 302; additionally or alternatively, an R angle may also be provided at the turning point between the bottom surface 321 of the airway 302 and the side wall 320. The R angles at different turning points may be the same or different. The setting of the R angle may further moderate the change in the refraction angle of the illumination light at the turning point, which may further improve the uniformity of light transmission of the chuck. In some embodiments of the present application, the R angle is greater than 0.1. In one embodiment of the present application, the R angle is equal to 0.5.

[0044] In other embodiments of the present application, the turning point of the cross-sectional profile of the air channel 302 may not be rounded, or may be provided with other transition structures. For example, the turning point between the upper surface 111 of the chuck and the side wall 320 of the air channel 302 may be chamfered, and the turning point between the bottom surface 321 of the air channel 302 and the side wall 320 may also be chamfered.

[0045] Figure 4 Shows Figure 3b The partial cross-sectional view of the airway 302 shown in FIG. In addition to the side wall 320 and the bottom surface 321 of the airway 302, Figure 4 Also shown in FIG. 1 are the upper surface 111 and a portion of the chuck body 103 .

[0046] For reference Figure 5a-5c as well as Figure 6a-6c The improvement of the light transmittance of the chuck by air channel 302 compared with air channel 301 is illustrated. For simplicity and clarity, Figure 5a-5c Only the suction surface of the chuck and the cross-sectional outline of one air channel are shown, while other parts of the chuck are omitted in the cross-sectional view.

[0047] Figure 5a The light path when the illumination light is irradiated on the adsorption surface of the chuck without the air channel is shown. In this case, the illumination light can be converged on the adsorption surface of the chuck, and uniform illumination can be achieved. Figure 6a is corresponding to Figure 5a The imaging effect diagram of the optical path shown in the figure, in which the black stripes are images representing the marks on the wafer. Figure 6aAs shown, since the light transmittance of the chuck is uniform, the brightness of each part in the obtained image is basically uniform.

[0048] Figure 5b The illumination light is shown as Figure 3a The light path of the air channel 301 when the chuck is attached to the surface. Since the side wall 310 of the air channel 301 is perpendicular to the bottom surface, the refraction direction of light irradiated at different positions of the air channel 301 will change suddenly, so that the light cannot be effectively converged, which leads to uneven illumination and affects the final imaging effect. Figure 6b is corresponding to Figure 5b The imaging effect diagram of the optical path shown in the figure, in which the black stripes are images representing the marks on the wafer. Figure 6b As shown, the air duct 301 with vertical sidewalls 310 may cause the obtained image to be darker overall and have uneven brightness, for example, Figure 6b The brightness of a large area in the upper left corner is too low, so that the specific details of the target object in the area cannot be clearly distinguished.

[0049] Figure 5c The illumination light is shown as Figure 3b The optical path of the airway 302 when the chuck is attached to the surface. Figure 5c It can be seen that the light irradiated at different positions of the airway 302 can generally still maintain a convergent state. Figure 5c The imaging effect diagram of the optical path shown in the figure, in which the black stripes are images representing the marks on the wafer. Figure 6c As shown, the obtained image brightness and its uniformity are Figure 6a The images shown are not much different. That is, the presence of the air channel 302 does not substantially affect the uniformity of light transmission of the chuck.

[0050] The excellent imaging effect brought by the airway 302 is due to the fact that the side wall 320 of the airway 302 is inclined with a small slope, and the depth of the airway 302 is small. The excellent imaging effect brought by the airway 302 is also due to the R angle set at the turning point between the bottom surface of the airway and the side wall of the airway and the turning point between the side wall of the airway and the chuck adsorption surface. The above designs are all to ensure that the shape of the airway does not change drastically and avoid sudden changes in light refraction, so that uniform illumination can be achieved at the airway.

[0051] Usually, after the air channel is formed on the chuck by cutting or other processes, the air channel surface is subjected to fire polishing. However, this polishing method may cause deformation of the air channel, and the air channel produced in this way may affect the imaging quality due to excessive surface roughness.

[0052] In some embodiments, the improved gas channel (such as gas channel 302) provided by the present application can be formed by conventional fire polishing. In other embodiments, the improved gas channel (such as gas channel 302) provided by the present application can be formed by cold polishing (such as mechanical polishing).

[0053] Figure 7 A flow chart of an exemplary method 700 of manufacturing a chuck for wafer bonding alignment detection according to some embodiments of the present application is shown.

[0054] At step 702, an air channel is formed on the chuck. The chuck is made of a material that can transmit illumination light used for wafer bonding alignment detection, such as a glass material. Various methods can be used to form the air channel on the chuck without departing from the spirit and scope of protection of the present application, and the present application is not intended to limit a specific method. In some embodiments, the air channel may have a side wall inclined relative to the bottom surface, such as a side wall having a side wall such as Figure 3b and Figure 4 Shape shown.

[0055] At step 704, the gas channel surface is subjected to cold polishing (e.g., mechanical polishing). The gas channel surface may include a side wall and a bottom surface. Compared with fire polishing, cold polishing is less likely to deform the gas channel, and can also remove microcracks on the gas channel surface, so that the gas channel surface has a lower surface roughness and a higher surface quality.

[0056] In some embodiments of the present application, a custom tool may be used for cold polishing. For example, the shape and size of the custom tool may be adjusted to accommodate the size of the airway and the R angle and α angle.

[0057] The method 700 applies the cold polishing process to the air channel processing on the chuck, which is beneficial to improving the surface quality of the chuck air channel, thereby better meeting the needs of wafer bonding alignment detection.

[0058] The description in this specification is provided to enable persons skilled in the art to make or use the present application. Various modifications to the present application will be readily apparent to those skilled in the art, and the general principles defined in this specification may be applied to other variations without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the examples and designs described in this specification, but is to be given the widest scope consistent with the principles and novel features disclosed in this specification.

Claims

1. A chuck for wafer bonding alignment detection, comprising: a disc body having an upper surface and a lower surface opposite to the upper surface; and The air channel is arranged on the upper surface and is used for providing adsorption force to adsorb the wafer to be inspected on the upper surface, wherein the air channel is recessed downward from the upper surface and has a bottom surface and a side wall inclined relative to the bottom surface.

2. The chuck of claim 1, wherein the gas channel comprises an annular gas channel and a radial gas channel. 3 . The chuck according to claim 2 , wherein the gas channel comprises an annular gas channel and three radial gas channels, and the three radial gas channels divide the area enclosed by the annular gas channel into three equal parts. The chuck of claim 1 , wherein the bottom surface is parallel to the upper surface. The chuck according to claim 1 , wherein a cross section of the air channel is substantially a trapezoidal shape that is wider at the top and narrower at the bottom. 6 . The chuck according to claim 5 , wherein a ratio of a width of an upper end of the air channel to a depth of the air channel is greater than or equal to 5. 7 . The chuck according to claim 1 , wherein an R angle is provided at a turning point between the upper surface and the side wall, and / or an R angle is provided at a turning point between the side wall and the bottom surface. The chuck according to claim 7 , wherein the R angle is greater than 0.

1. 9 . The chuck according to claim 1 , wherein an angle between the bottom surface and the side wall is greater than or equal to 110 degrees and less than 180 degrees.

10. The chuck of claim 1, wherein the air channel is cold polished.

11. A system for wafer bonding alignment detection, comprising: A chuck according to any one of claims 1 to 10, used for carrying a wafer to be inspected; a light source configured to emit illumination light; a lens assembly configured to direct the illumination light toward the chuck; as well as An imaging assembly is configured to receive illumination light that passes through the chuck and the wafer to image the wafer.

12. A method for manufacturing a chuck for wafer bonding alignment detection, comprising: forming an air channel on the chuck, wherein the air channel is recessed downward from the upper surface of the chuck and has a bottom surface and a side wall inclined relative to the bottom surface; and The surface of the air channel is subjected to cold polishing.

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