Device and system for wafer bonding alignment test

Abstract

The present application relates to a device and a system which are used for wafer bonding alignment test. Provided in one aspect of the present application is a chuck for wafer bonding alignment test. The chuck comprises: a chuck body, which has an upper surface and a lower surface opposite the upper surface; and an air channel, which is formed on the upper surface and is configured to provide a suction force so as to suction a wafer to be tested on the upper surface, wherein the air channel is recessed from the upper surface, and has a bottom surface and a side wall inclined relative to the bottom surface.

Description

Device and system for wafer bonding alignment detection Technical Field

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

[0002] Wafer bonding alignment detection is usually illuminated using 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 markings 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, there is a need to provide an improved solution for wafer bonding alignment detection.

[0003] Summary of the Invention

[0004] 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 side walls inclined relative to the bottom surface.

[0005] In some embodiments, the airway includes annular airways and radial airways.

[0006] 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.

[0007] In some embodiments, the bottom surface is parallel to the upper surface.

[0008] In some embodiments, the cross-section of the airway is generally trapezoidal, wider at the top and narrower at the bottom.

[0009] 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.

[0010] 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.

[0011] In some embodiments, the R angle is greater than 0.1.

[0012] In some embodiments, an angle between the bottom surface and the sidewall is greater than or equal to 110 degrees and less than 180 degrees.

[0013] In some embodiments, the air channel is cold blasted.

[0014] 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.

[0015] 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 side walls inclined relative to the bottom surface; and cold polishing the surface of the air channel.

[0016] The details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The disclosure in this specification refers to and includes the following figures:

[0018] FIG. 1 is a schematic diagram of a system for wafer bonding alignment detection according to an embodiment of the present application.

[0019] FIG. 2 is a top view of a chuck for carrying a wafer in the system shown in FIG. 1 .

[0020] FIG3 a is a schematic diagram of a chuck airway.

[0021] FIG3 b is a schematic diagram of a chuck air channel according to an embodiment of the present application.

[0022] FIG4 is a partial cross-sectional view of the vicinity of the chuck air passage according to an embodiment of the present application.

[0023] 5a to 5c are schematic diagrams of the light path when the illumination light is irradiated on different chuck adsorption surfaces.

[0024] 6a to 6c are imaging effect diagrams corresponding to the light paths shown in FIG. 5a to 5c , respectively.

[0025] FIG. 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.

[0026] As is customary, various features illustrated in the figures may not be drawn to scale. Therefore, the dimensions of various features may be arbitrarily enlarged or reduced for clarity. The shapes of the components illustrated in the figures are exemplary only and do not define the actual shapes of the components. Furthermore, the embodiments illustrated in the figures may be simplified for clarity. Therefore, the figures may not depict all components of a given device or apparatus. Finally, the same reference numerals may be used throughout the specification and figures to denote the same features. DETAILED DESCRIPTION

[0027] In order to better understand the spirit of this application, it is further described below in conjunction with some embodiments of this application.

[0028] The words "in one instance" or "according to an 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". "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 have no limiting effect. Different manufacturers may use different names to refer to components with the same function.

[0029] 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 order of execution of the steps may also be adjusted according to actual application.

[0030] 1 shows a system 100 for wafer bonding alignment detection according to an embodiment of the present application. The system 100 includes a light source 101 , a lens assembly 102 , a chuck 103 , and an imaging assembly 107 .

[0031] Light source 101 can emit illumination light toward lens assembly 102. In some embodiments, light source 101 can emit infrared light. In other embodiments, light source 101 can 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.

[0032] The chuck 103 is made of a material that is transparent to illumination light, for example, a glass material. The body of the chuck 103 has an upper surface 111 and a lower surface 121 opposite to the upper surface 111. The chuck 103 has an air channel (for example, on the upper surface 111), and the air channel is connected to a negative pressure device (not shown in Figure 1). The negative pressure device enables the air channel to provide an adsorption force (for example, forming a vacuum negative pressure in the air channel) by, for example, vacuuming, so that the wafers to be inspected (for example, wafer 104 and wafer 105) are adsorbed on the upper surface 111 of the chuck 103. The system 100 can use common negative pressure equipment in the art (for example, a vacuum pump), which will not be described in detail here.

[0033] The illumination light may further pass through chuck 103, wafer 105, and wafer 104, and ultimately be received by imaging assembly 107. The lower surface of wafer 104 and the upper surface of wafer 105 may be bonded to form bonding surface 106. Wafer 104 has a mark 108 on its lower surface, and wafer 105 has a mark 109 on its upper surface. Imaging assembly 107 images marks 108 and 109 to detect whether bonding surface 106 between wafers 104 and 105 meets standards (e.g., to detect whether marks 108 and 109 are aligned).

[0034] 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. FIG1 does not show a device or component for moving the light source 101, the lens assembly 102, the imaging assembly 107, or the chuck 103. Those skilled in the art will appreciate that, without departing from the spirit and scope of protection of the present application, various devices or components may 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. It should be understood that various suitable light sources, lens assemblies, and imaging assemblies may be used, and this does not affect the implementation of the present invention.

[0035] In the system 100 shown in FIG1 , the light source 101 and lens assembly 102 are located below the chuck 103, the bonded wafer is attached to the upper surface 111 of the chuck 103, and the imaging assembly 107 is located above the bonded wafer, with illumination light passing 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 lens assembly 102 may be located above the bonded wafer, with illumination light passing through the bonded wafer from top to bottom.

[0036] FIG2 is a top view of the chuck 103 in the system 100 shown in FIG1 , illustrating specific details of the upper surface 111 of the chuck 103. The upper surface 111 of the chuck 103 is generally flat and has a plurality of grooves recessed downward therefrom. These grooves constitute the gas channels on the upper surface 111 of the chuck 103. The gas channels on the chuck 103 may include an annular gas channel 201 and radial gas channels 202. The annular gas channel 201 is centered at the center of the chuck 103. The radial gas channels 202 are straight gas channels extending from the center of the chuck 103 to the edge of the chuck 103. The annular gas channel 201 may communicate with the radial gas channels. In the example of FIG2 , the chuck 103 has one annular gas channel 201 and three radial gas channels 202. The three radial gas channels 202 divide the area enclosed by the annular gas channel 201 into three equal parts. It should be understood that other numbers of annular air channels (e.g., multiple concentric annular air channels with different diameters) and other numbers of radial air channels may be provided without departing from the spirit and scope of the present application, and the present application is not intended to limit the specific distribution of the annular air channels and radial air channels. As previously mentioned, these air channels may be connected to a negative pressure device to provide negative pressure to hold the wafer against the upper surface 111 of the chuck 103.

[0037] 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 distributed, the smoother the wafer can be sucked. Taking the chuck 103 shown in Figure 2 as an example, additional annular air channels and / or radial air channels can be added, and these newly added air channels can be 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 suction force of the chuck 103 and the flatness of the sucked wafer. However, the increase in the number of air channels will reduce the overall strength of the chuck and will also affect the uniformity of the light transmittance of the chuck.

[0038] Another approach is to modify the shape of the airway.

[0039] Conventional air channels typically have a shape as shown in Figure 3a. For simplicity and clarity, Figure 3a only shows the suction surface (e.g., the top surface) of the chuck and the cross-sectional outline of one air channel 301, omitting the remaining portions of the chuck in the cross-sectional view. The air channel 301 shown in Figure 3a has two sidewalls 310 and a bottom surface 311. The sidewalls 310 are perpendicular to the bottom surface 311, and the bottom surface 311 is generally parallel to the top surface of the chuck. In other words, the cross-section of the air channel 301 is generally rectangular. In the cross-sectional view, the horizontal distance between the two sidewalls 310 defines the width W1 of the air channel 301, and the vertical distance between the top 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 to the depth D1 of the air channel 301 is typically approximately 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.

[0040] Therefore, it is necessary to improve the shape of the air channel so as to meet the chuck adsorption force requirements without increasing the number of air channels while ensuring that the chuck has sufficient strength and uniform light transmittance.

[0041] Some embodiments of the present application provide air passages that can meet the above requirements. FIG3 b shows a schematic diagram of an air passage according to an embodiment of the present application. For simplicity and clarity, FIG3 b only shows the suction surface of the chuck (e.g., the upper surface 111 of the chuck 103 shown in FIG1 and FIG2 ) and the cross-sectional outline of one air passage 302, while omitting other portions of the chuck in the cross-sectional view.

[0042] The air channel 302 shown in Figure 3b 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 its bottom surface 321. The bottom surface 321 may be substantially parallel to the upper surface 111 of the chuck. In other words, unlike the air channel 301 shown in Figure 3a, the cross-section of the air channel 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 with respect 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. In the cross-sectional view shown in Figure 3b, 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, which can also be 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.

[0043] Compared to the air channel 301 shown in Figure 3a, while providing the same suction 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, reducing the air channel depth can enhance the strength of the chuck. Furthermore, compared to the vertical sidewall 310, the inclined sidewall 320 can improve the sudden refraction of the illumination light at the turning point, thereby improving the uniformity of light transmission through the chuck.

[0044] Furthermore, as shown in FIG3b , 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 air channel 302; additionally or alternatively, an R angle may also be provided at the turning point between the bottom surface 321 of the air channel 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, thereby further improving 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.

[0045] In other embodiments of the present application, the transition points 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 transition point between the upper surface 111 of the chuck and the sidewall 320 of the air channel 302 may be chamfered, and the transition point between the bottom surface 321 of the air channel 302 and the sidewall 320 may also be chamfered.

[0046] Figure 4 shows a partial cross-sectional view of the vicinity of the air channel 302 shown in Figure 3b. In addition to the sidewall 320 and bottom surface 321 of the air channel 302, Figure 4 also shows the upper surface 111 of the chuck 103 and a portion of the chuck body.

[0047] 5a-5c and 6a-6c illustrate how air channel 302 improves the light transmittance of the chuck compared to air channel 301. For simplicity and clarity, FIG5a-5c only show the suction surface of the chuck and the cross-sectional outline of one air channel, while omitting other parts of the chuck in the cross-sectional view.

[0048] Figure 5a shows the optical path of illumination light when it is directed onto the suction surface of a chuck without air channels. In this case, the illumination light converges on the suction surface of the chuck, achieving uniform illumination. Figure 6a shows the resulting image corresponding to the optical path shown in Figure 5a, where the black stripes represent the image of the wafer markings. As shown in Figure 6a, due to the uniform light transmittance of the chuck, the brightness of each part of the resulting image is essentially uniform.

[0049] Figure 5b shows the optical path of the illumination light when it is irradiated on the chuck adsorption surface having the air channel 301 as shown in Figure 3a. Since the side wall 310 of the air channel 301 is perpendicular to the bottom surface, the refraction direction of the light irradiated at different positions of the air channel 301 will change suddenly, resulting in the inability to effectively converge the light, which leads to uneven illumination and affects the final imaging effect. Figure 6b is an imaging effect diagram corresponding to the optical path shown in Figure 5b, in which the black stripes are images representing the marks on the wafer. As shown in Figure 6b, the air channel 301 with vertical side walls 310 will cause the obtained image to be darker as a whole and uneven brightness. For example, the brightness of the large area in the upper left corner of Figure 6b is too low, making it impossible to clearly distinguish the specific details of the target object in this area.

[0050] Figure 5c shows the optical path of illumination light when it is directed onto the chuck's adsorption surface, which has air channels 302 as shown in Figure 3b. As can be seen from Figure 5c, light directed onto different locations along air channels 302 generally remains convergent. Figure 6c shows the resulting image corresponding to the optical path shown in Figure 5c, where the black stripes represent the image of the wafer markings. As shown in Figure 6c, the brightness and uniformity of the resulting image are comparable to those of the image shown in Figure 6a. In other words, the presence of air channels 302 has little impact on the uniformity of light transmission through the chuck.

[0051] The excellent imaging quality achieved by airway 302 is due to the gently inclined sidewalls 320 of airway 302 and the relatively shallow depth of airway 302. This excellent imaging quality is also due to the rounded corners at the transitions between the airway bottom and the airway sidewalls, as well as at the transitions between the airway sidewalls and the chuck's suction surface. These designs are designed to prevent abrupt changes in the airway shape and avoid sudden changes in light refraction, thereby achieving uniform illumination within the airway.

[0052] Typically, after forming the air channel on the chuck through a process such as cutting, 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 have excessive surface roughness, affecting imaging quality.

[0053] In some embodiments, the improved gas channel (e.g., gas channel 302) provided herein can be formed by conventional fire polishing. In other embodiments, the improved gas channel (e.g., gas channel 302) provided herein can be formed by cold polishing (e.g., mechanical polishing).

[0054] FIG. 7 shows a flow chart of an exemplary method 700 for manufacturing a chuck for wafer bonding alignment detection according to some embodiments of the present application.

[0055] At step 702, an air channel is formed on the chuck. The chuck is made of a material, such as glass, that is transparent to illumination light used for wafer bonding alignment inspection. Various methods can be used to form the air channel on the chuck without departing from the spirit and scope of this application, and this application is not intended to be limited to a particular method. In some embodiments, the air channel may have sidewalls that are inclined relative to the bottom surface, such as those shown in Figures 3b and 4.

[0056] At step 704, the gas channel surface is cold polished (e.g., mechanically polished). The gas channel surface may include the sidewalls and bottom surface. Compared to fire polishing, cold polishing is less likely to deform the gas channel and can also remove microcracks on the gas channel surface, resulting in a lower surface roughness and higher surface quality.

[0057] In some embodiments of the present application, a custom cutter can be used for cold polishing. For example, the shape and size of the custom cutter can be adjusted to accommodate the size of the airway and the R angle and α angle.

[0058] 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.

[0059] The description in this specification is provided to enable one 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 accorded the widest scope consistent with the principles and novel features disclosed herein.

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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