Alignment method of bonding body wafer on non-infrared exposure machine and preparation method of semiconductor device

Abstract

The invention provides a method for aligning a bonding body wafer on a non-infrared exposure machine, which comprises the following steps of: providing the bonding body wafer which comprises a plurality of wafers in bonding connection, and forming alignment marks on the bonding surfaces of the wafers which are mutually bonded; manufacturing an alignment photomask, wherein the alignment photomask is provided with an alignment mark window pattern; forming an alignment mark window on the surface of the bonding body wafer by utilizing photoetching and etching processes through an alignment photomask, and exposing the alignment mark on the bonding surface through the alignment mark window; and carrying out photoetching alignment through the exposed alignment mark. According to the method, the alignment problem when the alignment mark on the non-infrared exposure machine is positioned in the bonding body wafer is solved. The invention further provides a preparation method of the semiconductor device, the alignment method is adopted for alignment after the front face and the back face of a bonding body wafer are thinned, then the pattern face of the device is processed, and possible pollution to the bonding face and possible damage to the pattern face are avoided.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing, and in particular to a method for aligning a bonded wafer on a non-infrared exposure machine and a method for preparing a semiconductor device. Background Art

[0002] Wafer bonding is widely used in MEMS (Micro-Electro-Mechanical System) technology. Figure 1 A typical application scenario is shown. After the first substrate 1 and the second substrate 2 are bonded, it may be necessary to thin both sides of the bonded wafer and then perform subsequent photolithography and etching processes. During this process, the alignment mark 3 formed on the substrate surface will be hidden between the two substrates due to bonding, which will have a great impact on the alignment work in the subsequent process, that is, since there are no alignment marks 3 on the upper and lower surfaces of the bonded wafer, the next step of photolithography alignment operation cannot be performed.

[0003] In order to solve the above problem, an exposure machine with infrared alignment function can be used to achieve alignment between the bonded wafer and the mask by infrared transmission. If the exposure machine does not have infrared alignment function, a common practice is to transfer the alignment mark 3. Figure 2 As shown, before bonding, the first substrate 1 is photolithographically etched once, and alignment marks 3 are also formed on the other side of the first substrate 1; then bonding is performed, and the upper surface of the bonded second substrate 2 is thinned and subjected to subsequent photolithographic etching processes, and then the bonded substrate is turned over and the first substrate 1 is thinned.

[0004] However, the above process has two problems: first, during the preparation of the alignment mark 3 on the other side of the first substrate 1, the bonding surface may be contaminated, resulting in problems with the bonding strength; second, since the surface of the second substrate 2 has been subjected to a photolithography process, the subsequent process of turning over and thinning the first substrate 1 may affect the pattern surface of the second substrate 2. Therefore, it is necessary to provide a method that can align the bonded wafer with the alignment mark 3 between the two substrates without affecting the product performance. Summary of the invention

[0005] The present invention aims to solve all or part of the problems of the prior art. In a first aspect, a method for aligning a bonded wafer on a non-infrared exposure machine is provided, comprising:

[0006] S1. Providing a bonded wafer, wherein the bonded wafer comprises a plurality of bonded wafers, and alignment marks are formed on bonding surfaces of the mutually bonded wafers;

[0007] S2, making an alignment mask, wherein the alignment mask is provided with an alignment mark window pattern;

[0008] S3, forming an alignment mark window on the surface of the bonding body wafer by using the alignment mask and photolithography and etching processes, and exposing the alignment mark on the bonding surface through the alignment mark window;

[0009] S4. Perform photolithography alignment using the exposed alignment marks.

[0010] The present invention makes an alignment mask and uses photolithography and etching processes to expose the alignment marks inside the bonded wafer for subsequent photolithography alignment, thereby realizing the alignment requirements when the alignment marks are inside the bonded wafer on a non-infrared exposure machine; and this alignment method can avoid possible damage to the bonding surface and the graphic surface in traditional methods.

[0011] In some embodiments, the alignment mark on the bonding surface is obtained by photolithography and etching of the alignment mark pattern of the first mask; the position of the alignment mark window pattern on the alignment mask is consistent with the position of the alignment mark pattern on the first mask, and the size of the alignment mark window pattern is larger than the size of the alignment mark pattern. By controlling the correspondence between the alignment mask and the pattern on the mask used to form the alignment mark, it is more convenient to find the alignment mark to be revealed.

[0012] In some embodiments, in step S3, it includes:

[0013] S301, coating a photoresist on the surface of the bonded wafer, pre-aligning the alignment mask and the bonded wafer, and performing photolithography to obtain a patterned photoresist;

[0014] S302, performing etching using the patterned photoresist as a mask to etch the bonded wafer, and forming an alignment mark window on the surface of the bonded wafer to expose the alignment mark on the wafer bonding surface.

[0015] In some embodiments, the size of the alignment mark window is larger than the size of the alignment mark, and the size deviation between the alignment mark window and the alignment mark is larger than the accuracy of the pre-alignment. By properly setting the size of the alignment mark window pattern, the size of the formed alignment mark window can be changed, and as long as the size deviation between the formed alignment mark window and the alignment mark is larger than the accuracy of the pre-alignment, the alignment mark can be fully exposed.

[0016] In some embodiments, in step S1, the front and back surfaces of the bonded wafer have been thinned. The alignment method can be used to perform thinning before processing the pattern surface to avoid the influence of flipping on the device pattern surface.

[0017] In some embodiments, the alignment mark pattern is a cross shape, and the alignment mark window pattern is a square shape.

[0018] On the other hand, the present invention also provides a method for preparing a semiconductor device, comprising:

[0019] S1. providing at least two substrates to be bonded and a first photomask, wherein the substrates include a first substrate, the first photomask is provided with an alignment mark pattern, and an alignment mark is formed on a bonding surface of the first substrate by using the first photomask;

[0020] S2, bonding the substrates to form a bonded wafer, and thinning the front and back surfaces of the bonded wafer;

[0021] S3, making an alignment mask, wherein the alignment mask is provided with an alignment mark window pattern;

[0022] S4, forming an alignment mark window on the bonded body wafer by using the alignment mask and photolithography and etching processes to expose the alignment mark of the first substrate;

[0023] S5, aligning the bonded wafer and the pattern surface mask through the exposed alignment mark, patterning the surface of the bonded wafer to form a pattern surface through photolithography and etching processes, and obtaining a semiconductor device.

[0024] The present method adopts the alignment method provided in the first aspect to prepare semiconductor devices, so that the photolithography process can be completed on a non-infrared exposure machine; and compared with the prior art, the present method does not need to perform photolithography and etching on the front and back sides of the substrate to form alignment marks, thereby avoiding possible contamination of the bonding surface and ensuring the bonding strength of the bonded wafer; in addition, the present method completes the thinning of the front and back surfaces of the bonded wafer before performing the graphic surface processing of the device, thereby avoiding the possible damage to the graphic surface caused by turning over and thinning after the graphic surface processing is completed in the prior art, thereby improving the overall performance and yield of the device.

[0025] In some embodiments, in step S3, the position of the alignment mark window pattern on the alignment mask is consistent with the position of the alignment mark pattern on the first mask, and the size of the alignment mark window pattern is larger than the size of the alignment mark pattern.

[0026] In some embodiments, in step S4, it includes:

[0027] S401, coating a photoresist on the surface of the bonded wafer, pre-aligning the alignment mask and the bonded wafer, and performing photolithography to obtain a patterned photoresist;

[0028] S402, performing etching using the patterned photoresist as a mask until the bonding surface of the first substrate is reached to form an alignment mark window, thereby exposing the alignment mark of the first substrate.

[0029] In some embodiments, a size of the alignment mark window is larger than a size of the alignment mark, and a size deviation between the alignment mark window and the alignment mark is larger than an accuracy of the pre-alignment.

[0030] Compared with the prior art, the beneficial effects of the present invention mainly include the following: 1) This method solves the problem of realizing precise alignment when the alignment mark is located inside the bonded wafer on a non-infrared exposure machine; 2) This method does not require photolithography and etching on the front and back sides of the substrate to form alignment marks, thereby avoiding possible contamination of the bonding surface and ensuring the bonding strength of the bonded wafer; 3) This method completes the thinning of the front and back surfaces of the bonded wafer before processing the graphic surface of the device, thereby avoiding possible damage to the graphic surface caused by turning over and thinning after the graphic surface processing is completed in the prior art, thereby improving the overall performance and yield of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is a typical application scenario of wafer bonding process.

[0033] Figure 2 The figure is a schematic diagram of a front and back surface photolithography process of a bonded wafer in the prior art.

[0034] Figure 3 A schematic diagram of an alignment method for a bonded wafer on a non-infrared exposure machine provided in Embodiment 1 of the present invention.

[0035] Figure 4 A schematic diagram of the corresponding relationship between the alignment mark window pattern and the alignment mark pattern provided in the first embodiment of the present invention.

[0036] Figure 5 A schematic diagram of a method for preparing a semiconductor device provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0037] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

[0038] The following will describe the various embodiments of the present application in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are provided in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in the present application can be implemented.

[0039] In the manufacturing process of some special semiconductor devices, two substrates are first bonded and their upper and lower surfaces are thinned and then patterned. Figure 1 As shown, in this type of process, the alignment mark 3 formed on the substrate surface will be hidden between the two substrates due to bonding. Since there are no alignment marks 3 on the upper and lower surfaces of the bonded wafer, the next lithography alignment operation cannot be performed.

[0040] In the prior art, an exposure machine with an infrared alignment function can be used to achieve alignment between the bonded wafer and the corresponding mask by infrared transmission. If the exposure machine does not have an infrared alignment function, the alignment mark 3 is usually transferred, referring to Figure 2 The specific process is as follows:

[0041] Step 1: Provide a first substrate 1 and a second substrate 2, and transfer the alignment mark 3 on the front side to the back side of the first substrate 1 by front- and back-side photolithography.

[0042] First of all, it is well known that the definition of the pattern on the substrate is completed through photolithography and etching processes. That is, the required pattern is set on the mask, including the alignment mark pattern, and then the pattern on the mask is transferred to the photoresist through the photolithography process (including the steps of photoresist coating, exposure, and development) to form a photoresist pattern; then, the photoresist is used as a barrier layer, and the pattern on the mask is finally transferred to the substrate through the etching process.

[0043] It can be understood that in the usual process, only one side of the alignment mark will be prepared on a substrate. Here, alignment marks are prepared on both the front and back sides of the first substrate 1 to meet the subsequent photolithography alignment requirements. Specifically, the alignment mark pattern is first transferred to the front side of the first substrate 1 through a photomask, so that an alignment mark 3 is formed on the front side of the first substrate 1. Afterwards, the alignment mark 3 is formed on the back side of the first substrate 1 in the same way, that is, the first substrate 1 is turned over, and then the alignment mark 3 on the front side of the first substrate 1 and the alignment mark pattern on the photomask are respectively aligned with the alignment mark on the exposure machine, thereby realizing the alignment of the first substrate 1 and the photomask, and then the alignment mark 3 can also be formed on the back side of the first substrate 1 through photolithography and etching processes.

[0044] It should be noted that, because the front side of the first substrate 1 , ie, the subsequent bonding surface, will be in contact with the machine during the process of forming the alignment mark 3 on the back side of the first substrate 1 , the bonding surface may be contaminated, thus affecting the subsequent bonding strength.

[0045] Step 2: Bond the first substrate 1 and the second substrate 2, and thin the second substrate 2.

[0046] The front side of the first substrate 1 and the front side of the second substrate 2 are bonded to obtain a bonded wafer. As described above, in the process of forming the alignment mark on the back side of the first substrate 1, the front side of the first substrate 1, i.e., the bonding surface, may be contaminated, affecting the bonding strength of the resulting bonded wafer, and further affecting the performance of the final device. After the bonding is completed, the surface of the second substrate 2 is thinned, and the thinned surface is the back side of the second substrate 2.

[0047] As mentioned above, regardless of whether there are alignment marks on the front and back of the second substrate 2, there must be no alignment marks on the back due to the thinning process, and the front of the two substrates is the bonding surface, so the alignment marks on the front are inside the bonding sheet, and alignment is impossible when the exposure machine does not have an infrared alignment function. Therefore, only the alignment marks on the back of the first substrate 1 can be used for alignment.

[0048] Step three: perform photolithography and etching on the surface of the second substrate 2 to obtain the desired pattern.

[0049] As described in step 2, alignment is performed using the alignment marks on the back of the first substrate 1, and photolithography and etching are performed on the surface of the second substrate 2 (ie, the back of the second substrate 2) using a corresponding pattern mask to obtain the desired pattern.

[0050] Step 4: Flip the bonded wafer and perform thinning on the surface of the first substrate 1 .

[0051] At this time, the second substrate 2 has been thinned and the required pattern is formed on its surface. When the first substrate 1 is thinned, the surface of the second substrate 2 with the required pattern (i.e., the pattern surface) is facing downward and in contact with the machine. During the thinning process, the pattern surface may be damaged, affecting the performance of the final device.

[0052] In order to solve the problem in the prior art that the alignment mark is inside the bonded wafer and improve the performance of the device finally prepared, improvements are made based on the above-mentioned prior art, and the steps in the following embodiments do not correspond one to one with the content of the invention.

[0053] Embodiment 1:

[0054] The present invention provides a method for aligning a bonded wafer on a non-infrared exposure machine, and the alignment method comprises the following steps:

[0055] Step 1: Provide a bonded wafer, wherein the alignment mark of the bonded wafer is located inside the bonded wafer.

[0056] In this embodiment, refer to Figure 3 In a, the provided bonding body wafer includes a first substrate 1 and a second substrate 2, and alignment marks 3 are respectively formed on the bonding surfaces of the first substrate 1 and the second substrate 2, that is, the alignment marks 3 are located inside the bonding body wafer.

[0057] It is understood that the specific structure of the bonded wafer and its preparation process are not limited in this method, nor is the number of wafers used to form the bonded wafer limited. For example, the bonded wafer provided in this embodiment is formed by bonding two wafers, and in other embodiments, the number may be 3 or more. The following is only an example for easy understanding.

[0058] In this embodiment, the first substrate 1 and the second substrate 2 are both single crystal silicon substrates; in other embodiments, the first substrate 1 and / or the second substrate 2 may also be other semiconductor substrates, such as a germanium substrate, a silicon nitride substrate or an SOI substrate.

[0059] In this embodiment, the alignment mark 3 is formed by first transferring its pattern to the front surface of the first substrate 1 through a first mask (not shown in the figure), wherein the pattern of the first mask includes the alignment mark pattern, and thus the alignment mark 3 is formed on the front surface of the first substrate 1. Similarly, the pattern is transferred to the front surface of the second substrate 2 through a second mask, wherein the pattern of the second mask includes the alignment mark pattern, and thus the alignment mark 3 is also formed on the front surface of the second substrate 2. This method does not limit the bonding process of the bonded wafer and the method for forming the alignment mark 3 thereon.

[0060] In this embodiment, the exposure machine used may be a proximity exposure machine or a contact exposure machine, and this patent does not limit this.

[0061] In this embodiment, the surfaces of the first substrate 1 and the second substrate 2 of the provided bonded wafer are both formed with alignment marks 3. In other embodiments, the alignment mark 3 may be formed on the surface of one of them, for example, the alignment mark 3 is formed only on the first substrate 1.

[0062] In this embodiment, it is not limited whether there are other patterns on the patterns on the first mask and the second mask used to form the alignment mark 3 except for the alignment mark pattern.

[0063] In the present embodiment, the position and size of the alignment mark patterns on the first photomask and the second photomask used to form the alignment mark 3 are the same. In other embodiments, the position and size of the alignment mark patterns on the first photomask and the second photomask used to form the alignment mark 3 may be the same or different. In other embodiments, if the position and size of the alignment mark patterns on the first photomask and the second photomask used to form the alignment mark 3 are the same, that is, the first photomask and the second photomask are the same, then only one photomask may be used as the first photomask and the second photomask, that is, the alignment mark 3 is formed on the surfaces of the first substrate 1 and the second substrate 2 respectively by the first photomask (also referred to as the second photomask).

[0064] In this embodiment, two alignment marks 3 are formed on each substrate; in other embodiments, the number of alignment marks formed on each substrate may be other numbers, such as only one, or at least two.

[0065] In this embodiment, the upper and lower surfaces of the provided bonded wafer have been thinned. The method does not limit the specific thinning method of the bonded wafer. In this embodiment, the provided bonded wafer is first thinned on the front side of the bonded wafer (i.e., the surface of the second substrate 2), and then thinned on the back side of the bonded wafer (i.e., the surface of the first substrate 1). The final result is shown in FIG. Figure 3 a in.

[0066] It can be understood that in this embodiment, the provided bonded wafer does not use the front and back side lithography steps in the prior art on any substrate, so it will not cause additional contamination to the bonding surface, and will not affect the bonding strength of the resulting bonded wafer, thereby improving the performance and overall yield of the resulting final device.

[0067] Step 2: Prepare the corresponding alignment mask 5 according to the alignment mark 3 to be revealed.

[0068] Since the alignment mark 3 is located inside the provided bonded wafer, in order to achieve the subsequent photolithography alignment requirement, the technical solution adopted in this application is to expose the alignment mark 3 inside the bonded wafer by etching, and perform subsequent alignment with the exposed alignment mark 3.

[0069] In this embodiment, in order to expose the alignment mark 3 inside the bonded wafer (in this embodiment, the alignment mark 3 formed on the first substrate 1), a special alignment mask 5 is made. The alignment mask 5 is made by opening the position of the alignment mark 3 when making the mask, and the rest of the position is covered with metal. It is at the same position as the alignment mark pattern on the mask used to form the alignment mark 3, but the opened area here is larger than the alignment mark pattern.

[0070] Specifically, refer to Figure 3 b and Figure 4 As shown, an alignment mark window pattern 50 is formed on the alignment mask 5, and the position of the alignment mark window pattern 50 on the mask is consistent with the position of the alignment mark pattern 10 on the first mask on the mask, and the size of the alignment mark window pattern 50 is larger than the alignment mark pattern 10: that is, when the alignment mask 5 and the first mask are aligned up and down, the projection of the alignment mark window pattern 50 on the alignment mask 5 on the plane should cover the projection of the alignment mark pattern 10 on the first mask on the plane, and the result is as shown in FIG. Figure 4 As shown. Figure 4 In the embodiment, the alignment mark pattern 10 is a cross shape, while the alignment mark window pattern 50 is a square shape. The alignment mark pattern 10 is smaller than the alignment mark window pattern 50 and is located at the center of the alignment mark window pattern 50. It can be understood that when the alignment mark 3 to be revealed is different, the alignment mask 5 manufactured accordingly also changes accordingly. For example, when the alignment mark 3 located on the second substrate 2 is to be revealed, the alignment mask 5 manufactured at this time should correspond to the second mask; similarly, the subsequent etching also reveals the alignment mark 3 on the second substrate 2.

[0071] Step 3: Through the alignment mask 5, the surface of the second substrate 2 is photolithographically and etched to reveal the alignment mark 3 inside the bonded wafer. Specifically, a layer of photoresist is first coated on the surface of the second substrate 2 to form a first photoresist layer 4. Figure 3a in the figure; then pre-align the alignment mask 5 and the bonded wafer. Pre-alignment is the preliminary alignment of the wafer before it is sent into the lithography machine or other processing equipment. The main purpose of this pre-alignment step is to ensure that the wafer can be accurately aligned in the subsequent process steps, thereby improving manufacturing accuracy and reducing defects. The completion of this step is a prior art and can be performed by a pre-alignment mechanism or equipment, generally including steps such as adjusting the center of the wafer and finding the V-groove (notch) of the wafer. The key point of the present invention is to reveal the alignment mark 3 inside the bonded wafer through the alignment mask 5. Therefore, in this process, the alignment mask 5 is only used to reveal the position of the alignment mark 3, and it does not have excessive requirements on the accuracy of pattern alignment between different layers (i.e., OVL accuracy). Therefore, by utilizing this feature, the exposure requirement of the alignment mark 3 can be met only by pre-alignment, so that non-aligned exposure can be performed subsequently without affecting the normal process; thereafter, the first photoresist layer 4 is exposed through the alignment mask 5 and subsequently developed, and the alignment mark window pattern 50 on the alignment mask 5 is transferred to the first photoresist layer 4; finally, through the etching process, the photoresist is used as a barrier layer, and the alignment mark window pattern 50 is finally transferred to the surface of the second substrate 2, that is, the alignment mark window 20 is etched on the surface of the second substrate 2 (see Figure 3 c) in.

[0072] It can be understood that, generally speaking, the accuracy of existing pre-alignment is within tens of microns. Through pre-alignment, the initial correspondence between the alignment mark window graphic 50 of the alignment mask 5 and the alignment mark 3 inside the bonded body wafer can be achieved, and because the size of the alignment mark window graphic 50 is larger than the alignment mark graphic 10, the size of the alignment mark window 20 finally formed on the surface of the second substrate 2 will be larger than the alignment mark 3 on the first substrate. Therefore, as long as the exposed area, i.e., the alignment mark window 20, is appropriately enlarged to ensure that the accuracy of the pre-alignment step can be covered, the alignment mark 3 on the first substrate can be exposed. Then, the exposed alignment mark 3 can also be used to achieve precise alignment of the mask and the bonded body wafer. At this point, a method for aligning a bonded body wafer on a non-infrared exposure machine is completed.

[0073] Embodiment 2:

[0074] The present invention also provides a method for preparing a semiconductor device. In this embodiment, a method for preparing a semiconductor device adopts the alignment method provided in the first embodiment to perform alignment and then perform pattern surface etching. Specifically, the preparation method includes the following steps:

[0075] Step 1: Provide a first substrate 1 and a second substrate 2, and form alignment marks 3 on surfaces of the first substrate 1 and the second substrate 2, respectively.

[0076] Reference Figure 5 In a, two substrates are first provided, namely a first substrate 1 and a second substrate 2, and the first substrate 1 and the second substrate 2 are both single crystal silicon substrates. In other embodiments, the first substrate 1 and / or the second substrate 2 may also be other semiconductor substrates, such as a germanium substrate, a silicon nitride substrate, or an SOI substrate.

[0077] It should be noted that the method does not limit the number of wafers provided for subsequent bonding. For example, in this embodiment, two wafers are provided, but in other embodiments, the number may be three or more.

[0078] As mentioned above, the definition of the pattern on the substrate is completed through photolithography and etching processes. That is, the required pattern is set on the mask, including the alignment mark pattern, and then the pattern on the mask is transferred to the photoresist through the photolithography process (including the steps of photoresist coating, exposure, and development) to form a photoresist pattern; then, the photoresist is used as a barrier layer, and the pattern on the mask is finally transferred to the substrate through the etching process.

[0079] It can be understood that in this embodiment, the pattern is first transferred to the front side of the first substrate 1 through a first mask (not shown in the figure), wherein the pattern of the first mask includes an alignment mark pattern, and thus an alignment mark 3 is formed on the front side of the first substrate 1. Similarly, the pattern is transferred to the front side of the second substrate 2 through a second mask, wherein the pattern of the second mask includes an alignment mark pattern, and thus an alignment mark 3 is also formed on the front side of the second substrate 2.

[0080] In this embodiment, the exposure machine used may be a proximity exposure machine or a contact exposure machine, and this patent does not limit this.

[0081] In this embodiment, alignment marks 3 are formed on the surfaces of both the first substrate 1 and the second substrate 2 . In other embodiments, the alignment mark 3 may be formed on the surface of one of them, for example, the alignment mark 3 is formed only on the first substrate 1 .

[0082] In this embodiment, it is not limited whether there are other patterns on the patterns on the first mask and the second mask except the alignment mark pattern.

[0083] In this embodiment, the positions and sizes of the alignment mark patterns on the first photomask and the second photomask are the same. In other embodiments, the positions and sizes of the alignment mark patterns on the first photomask and the second photomask may be the same or different. In other embodiments, if the positions and sizes of the alignment mark patterns on the first photomask and the second photomask are the same, only one photomask may be used as the first photomask and the second photomask, that is, the alignment marks 3 are formed on the surfaces of the first substrate 1 and the second substrate 2 respectively through the first photomask (also referred to as the second photomask).

[0084] In this embodiment, two alignment marks 3 are formed on each substrate. In other embodiments, the number of alignment marks formed on each substrate may be other numbers, such as only one, or at least two.

[0085] Step 2: Bond the first substrate 1 and the second substrate 2 to obtain a bonded wafer, and perform thinning processing on the front and back surfaces of the bonded wafer.

[0086] Reference Figure 5 As shown in a in FIG. 1 , in this embodiment, the front surface of the first substrate 1 and the front surface of the second substrate 2 are used as bonding surfaces for bonding. During the bonding process, the alignment marks 3 on the first substrate 1 and the second substrate 2 can be used to achieve alignment between the two. Since the alignment mark 3 formed in step 1 is located on the front surface of the substrate, after bonding, the alignment mark 3 is located inside the bonded wafer (i.e., on the bonding surface of the bonded wafer).

[0087] In the bonding process of this embodiment, since the front and back photolithography steps in the prior art are not used on any substrate, no additional contamination will be caused to the bonding surface, and the bonding strength of the resulting bonded wafer will not be affected, thereby improving the performance and overall yield of the resulting final device.

[0088] The front and back surfaces of the bonded wafer are thinned, that is, the surface of the first substrate 1 of the bonded wafer and the surface of the second substrate 2 of the bonded wafer are thinned. The present application does not limit the thinning order of the front and back surfaces and the specific thinning process flow. In this embodiment, the front surface of the bonded wafer (that is, the surface of the second substrate 2) is thinned first, and then the back surface of the bonded wafer (that is, the surface of the first substrate 1) is thinned. The final result is shown in FIG. Figure 5 a in.

[0089] Step 3: Prepare the corresponding alignment mask 5 according to the alignment mark 3 to be revealed.

[0090] Since the alignment mark 3 is located inside the bonded wafer, in order to achieve the subsequent photolithography alignment requirement, the technical solution adopted in this application is to expose the alignment mark 3 inside the bonded wafer by etching, and perform subsequent alignment with the exposed alignment mark 3.

[0091] In this embodiment, in order to expose the alignment mark 3 inside the bonded wafer (in this embodiment, the alignment mark 3 formed on the first substrate 1), a special alignment mask 5 is made. The alignment mask 5 is a mask in which the position of the alignment mark 3 is opened when making the mask, and the rest of the position is covered with metal. The alignment mark pattern on the mask used to form the alignment mark 3 is in the same position, but the opened area here is larger than the alignment mark pattern. For details, refer to Figure 5 b and Figure 4 As shown, an alignment mark window pattern 50 is formed on the alignment mask 5, and the position of the alignment mark window pattern 50 on the mask is consistent with the position of the alignment mark pattern 10 on the first mask on the mask, and the size of the alignment mark window pattern 50 is larger than the alignment mark pattern 10: that is, when the alignment mask 5 and the first mask are aligned up and down, the projection of the alignment mark window pattern 50 on the alignment mask 5 on the plane should cover the projection of the alignment mark pattern 10 on the first mask on the plane, and the result is as shown in FIG. Figure 4 As shown. Figure 4 In the embodiment, the alignment mark pattern 10 is in a cross shape, and the alignment mark window pattern 50 is in a square shape. The alignment mark pattern 10 is smaller than the alignment mark window pattern 50 and is located at the center of the alignment mark window pattern 50.

[0092] Step 4: By aligning the mask 5, photolithography and etching are performed on the surface of the second substrate 2 to reveal the alignment mark 3 inside the bonded wafer.

[0093] Specifically, a layer of photoresist is first coated on the surface of the second substrate 2 to form a first photoresist layer 4. Figure 5a in the figure; then the alignment mask 5 and the bonded wafer are pre-aligned. Pre-alignment is the preliminary alignment of the wafer before it is sent into the lithography machine or other processing equipment. The main purpose of this pre-alignment step is to ensure that the wafer can be accurately aligned in the subsequent process steps, thereby improving manufacturing accuracy and reducing defects. The completion of this step is a prior art and can be performed by a pre-alignment mechanism or equipment, generally including steps such as adjusting the center of the wafer and finding the V-groove (notch) of the wafer; thereafter, the first photoresist layer 4 is exposed to the alignment mask 5 and subsequently developed, and the alignment mark window pattern 50 on the alignment mask 5 is transferred to the first photoresist layer 4; finally, through an etching process, using the photoresist as a barrier layer, the alignment mark window pattern 50 is finally transferred to the surface of the second substrate 2, that is, an alignment mark window 20 is etched on the surface of the second substrate 2 (see Figure 5 c) in.

[0094] It can be understood that, generally speaking, the accuracy of existing pre-alignment is within tens of microns. Through pre-alignment, the alignment mark window pattern 50 of the alignment mask 5 and the alignment mark 3 inside the bonded body wafer can be initially aligned, and since the size of the alignment mark window pattern 50 is larger than the alignment mark pattern 10, the size of the alignment mark window 20 finally formed on the surface of the second substrate 2 will be larger than the alignment mark 3 on the first substrate. Therefore, as long as the exposed area, i.e., the alignment mark window 20, is appropriately enlarged to ensure that the accuracy of the pre-alignment step can be covered, the alignment mark 3 on the first substrate can be exposed.

[0095] Step 5: Perform photolithography and etching on the surface of the second substrate 2 through the pattern surface mask 7 to achieve processing of the pattern surface of the device.

[0096] Reference Figure 5 As shown in d, firstly, a second photoresist layer 6 is formed on the surface of the second substrate 2; then, the alignment mark 3 on the exposed first substrate is used to realize the precise alignment of the pattern surface mask 7 and the bonded body wafer; then, referring to Figure 5 As shown in FIG. 5 , the second photoresist layer 6 is exposed to light through the pattern surface mask 7 and subsequently developed and processed to transfer the pattern on the pattern surface mask 7 to the second photoresist layer 6; finally, the pattern is transferred to the surface of the second substrate 2 by etching process using the photoresist as a barrier layer, that is, the surface of the second substrate 2 is patterned to obtain the pattern surface required by the device. The result is referred to FIG. Figure 5 As shown in f.

[0097] Since the method adopts the alignment step provided in the first embodiment and does not use the front and back photolithography processes commonly used in the prior art, the possibility of bonding surface contamination can be reduced, thereby ensuring the bonding strength of the bonded wafer; in addition, the thinning processes of the two substrates are completed before the processing of the graphic surface, and there is no need to worry about damage to the graphic surface during flipping and thinning, further ensuring the performance of the device.

[0098] In order to facilitate the description, some common English nouns or letters used in the present invention are only used for exemplary reference rather than restrictive interpretation or specific usage, and the protection scope of the present invention should not be limited by their possible Chinese translations or specific letters.

[0099] It should also be noted that, in this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

Claims

1. A method for aligning a bonded wafer on a non-infrared exposure machine, characterized in that: include: S1. Providing a bonded wafer, wherein the bonded wafer comprises a plurality of bonded wafers, and alignment marks are formed on bonding surfaces of the mutually bonded wafers; S2, making an alignment mask, wherein the alignment mask is provided with an alignment mark window pattern; S3, forming an alignment mark window on the surface of the bonding body wafer by using the alignment mask and photolithography and etching processes, and exposing the alignment mark on the bonding surface through the alignment mark window; S4. Perform photolithography alignment using the exposed alignment marks.

2. The method for aligning a bonded wafer on a non-infrared exposure machine according to claim 1, characterized in that: The alignment mark on the bonding surface is obtained by photolithography and etching of the alignment mark pattern of the first photomask; The position of the alignment mark window pattern on the alignment mask is consistent with the position of the alignment mark pattern on the first mask, and the size of the alignment mark window pattern is larger than the size of the alignment mark pattern.

3. The method for aligning a bonded wafer on a non-infrared exposure machine according to claim 2, characterized in that: In step S3, it includes: S301, coating a photoresist on the surface of the bonded wafer, pre-aligning the alignment mask and the bonded wafer, and performing photolithography to obtain a patterned photoresist; S302, performing etching using the patterned photoresist as a mask to etch the bonded wafer, and forming an alignment mark window on the surface of the bonded wafer to expose the alignment mark on the wafer bonding surface.

4. The method for aligning a bonded wafer on a non-infrared exposure machine according to claim 3, characterized in that: The size of the alignment mark window is larger than the size of the alignment mark, and the size deviation between the alignment mark window and the alignment mark is larger than the accuracy of the pre-alignment.

5. The method for aligning a bonded wafer on a non-infrared exposure machine according to claim 1, characterized in that: In step S1 , the front and back surfaces of the bonded wafer have been thinned.

6. The method for aligning a bonded wafer on a non-infrared exposure machine according to claim 2, characterized in that: The alignment mark pattern is a cross shape, and the alignment mark window pattern is a square shape.

7. A method for preparing a semiconductor device, characterized in that: include: S1. providing at least two substrates to be bonded and a first photomask, wherein the substrates include a first substrate, the first photomask is provided with an alignment mark pattern, and an alignment mark is formed on a bonding surface of the first substrate by using the first photomask; S2, bonding the substrates to form a bonded wafer, and thinning the front and back surfaces of the bonded wafer; S3, making an alignment mask, wherein the alignment mask is provided with an alignment mark window pattern; S4, forming an alignment mark window on the bonded body wafer by using the alignment mask and photolithography and etching processes to expose the alignment mark of the first substrate; S5, aligning the bonded wafer and the pattern surface mask through the exposed alignment mark, patterning the surface of the bonded wafer to form a pattern surface through photolithography and etching processes, and obtaining a semiconductor device.

8. The method for preparing a semiconductor device according to claim 7, characterized in that: In step S3, the position of the alignment mark window pattern on the alignment mask is consistent with the position of the alignment mark pattern on the first mask, and the size of the alignment mark window pattern is larger than the size of the alignment mark pattern.

9. The method for preparing a semiconductor device according to claim 8, characterized in that: In step S4, it includes: S401, coating a photoresist on the surface of the bonded wafer, pre-aligning the alignment mask and the bonded wafer, and performing photolithography to obtain a patterned photoresist; S402, performing etching using the patterned photoresist as a mask until the bonding surface of the first substrate is reached to form an alignment mark window, thereby exposing the alignment mark of the first substrate.

10. The method for preparing a semiconductor device according to claim 9, characterized in that: The size of the alignment mark window is larger than the size of the alignment mark, and the size deviation between the alignment mark window and the alignment mark is larger than the accuracy of the pre-alignment.

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