Method and system for reducing dead pixels on back of crystal

Abstract

The invention provides a method and system for reducing dead pixels on a wafer back, and belongs to the field of semiconductors. The method for reducing the dead pixels on the back of the wafer comprises the following steps: acquiring data information of positions and sizes of the dead pixels on the back of the wafer; and performing fixed-point cleaning on the dead pixels of the wafer back by adopting a PVA brush based on the data information of the positions and the sizes of the dead pixels of the wafer back. And carrying out polishing treatment on the wafer back at the fixed-point cleaning position based on the data information of the position and the size of the wafer back dead pixel. According to the method, the data information of the specific positions and sizes of the dead pixels of the wafer back is firstly obtained, then the dead pixels are subjected to fixed-point cleaning by adopting the PVC brush based on the positions and sizes of the replacement points, and then the positions subjected to fixed-point cleaning are polished by adopting the carborundum polishing pieces, so that the number of the dead pixels of the wafer back can be reduced, the flatness of the wafer back is improved, and the production efficiency of the wafer back is improved. Therefore, the rework rate of a photoetching process is reduced, and the performance and yield of a product are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method and system for reducing backside bad spots. Background Art

[0002] Photolithography is an important step in the semiconductor device manufacturing process. This step uses exposure and development to depict geometric structures on the photoresist layer, and then uses an etching process to transfer the pattern on the photomask to the substrate. The substrate here includes not only silicon wafers, but also other metal layers and dielectric layers, such as glass and sapphire in SOS.

[0003] The photolithography process has very high requirements for the flatness of the wafer. When there are particles on the back of the wafer, bad spots will be generated, which will cause defocusing during exposure, so that the image formed during exposure cannot be accurately focused on the predetermined plane, resulting in blurred edges of the pattern, which will affect the final performance and yield of the product. The current detection is to add a flatness detection sensor to the scanner to measure the height of the crystal surface reflection to measure the flatness of the back of the crystal. However, when the bad spots are detected, it is already a step before exposure in the scanner. The scanner can compensate for small bad spots, but it cannot compensate for large bad spots. Therefore, for wafers with large bad spots, they can only be reworked. The rework rate caused by bad spots in the photolithography process is very high.

[0004] It should be noted that the information disclosed in the background technology section of the invention is only intended to deepen the understanding of the general background technology of the invention, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0005] The object of the present invention is to provide a method and system for reducing bad spots on the wafer backside, so as to solve the problems of low wafer backside flatness and high rework rate of the lithography process caused by bad spots in the lithography process.

[0006] In order to solve the above technical problems, the present invention provides a method for reducing wafer backside bad spots, comprising:

[0007] Obtain data information on the location and size of bad spots on the back of the wafer;

[0008] Based on the location and size of the bad spots on the back of the wafer, a PVA brush is used to perform fixed-point cleaning on the bad spots on the back of the wafer.

[0009] Based on the data information of the position and size of the bad spot on the crystal back, the crystal back at the fixed cleaning position is polished.

[0010] Preferably, the step of obtaining the data information of the location and size of the bad spot on the back of the wafer includes:

[0011] The location and size of the bad spots on the back of the wafer are obtained through the automatic wafer scanner.

[0012] Preferably, between using a PVA brush to perform spot cleaning on the bad spots on the back of the crystal and polishing the back of the crystal at the spot cleaning position, the method for reducing bad spots on the back of the crystal also includes:

[0013] The back of the wafer was cleaned with deionized water.

[0014] Preferably, in the polishing process of the crystal back at the fixed-point cleaning position based on the data information of the position and size of the bad spot on the crystal back, diamond abrasive is used to polish the crystal back at the fixed-point cleaning position.

[0015] Based on the same inventive concept, the present invention also provides a system for reducing wafer backside bad spots, comprising:

[0016] An acquisition unit, used to acquire data information on the position and size of a bad spot on the back of a wafer;

[0017] The cleaning unit is used to perform fixed-point cleaning of the bad spots on the crystal back using a PVA brush based on the data information of the position and size of the bad spots on the crystal back; and polish the crystal back at the fixed-point cleaning position based on the data information of the position and size of the bad spots on the crystal back.

[0018] Preferably, the acquisition unit comprises a photographing module and an output module, the photographing module is used to acquire data information on the location and size of bad spots on the back of the wafer, and the output module is used to transmit the data information to the washing unit.

[0019] Preferably, the washing unit comprises a cleaning mechanism, a receiving module and a control module;

[0020] The receiving module is used to receive the data information and transmit the data information to the control module;

[0021] The control module is used to receive data information and issue control instructions to the cleaning mechanism.

[0022] Preferably, the cleaning mechanism includes a PVA brush, a diamond polishing piece, a connecting part, and a driving device, the driving end of the driving device is connected to the connecting part, the PVA brush and the diamond polishing piece are installed on the connecting part and distributed radially along the connecting part.

[0023] Preferably, the cleaning unit also includes a moving mechanism, which is connected to the control module and the cleaning mechanism, and is used to receive control instructions output by the control module and drive the cleaning mechanism to move arbitrarily along a first direction, a second direction and a third direction, and the first direction, the second direction and the third direction are perpendicular to each other.

[0024] Preferably, the system for reducing bad spots on the wafer backside further comprises: a cleaning unit for cleaning the wafer backside with deionized water.

[0025] Compared with the prior art, the method for reducing wafer backside bad spots of the present invention has the following advantages:

[0026] The method for reducing bad spots on the crystal back provided by the present invention first obtains data information on the specific position and size of the bad spots on the crystal back, then uses a PVC brush to perform fixed-point cleaning on the bad spots based on the position and size of the bad spots, and then uses a diamond polishing piece to polish the fixed-point cleaning position, thereby reducing the number of bad spots on the crystal back and improving the flatness of the crystal back, thereby reducing the rework rate of the photolithography process and improving the performance and yield of the product.

[0027] The system for reducing bad spots on the crystal back provided by the present invention and the method for reducing bad spots on the crystal back provided by the present invention belong to the same inventive concept. Therefore, the system for reducing bad spots on the crystal back provided by the present invention has at least all the advantages of the method for reducing bad spots on the crystal back provided by the present invention, and can reduce the number of bad spots on the crystal back and improve the flatness of the crystal back, so as to reduce the rework rate of the lithography process and improve the performance and yield of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flow chart of a method for reducing wafer backside bad spots in one embodiment of the present invention;

[0029] Figure 2 It is a schematic diagram of the connection structure of the cleaning mechanism in one embodiment of the present invention;

[0030] In the figure,

[0031] 10-driving device; 20-connecting part;

[0032] 30-PVA brush; 40-emery polishing parts. DETAILED DESCRIPTION

[0033] In order to make the purpose, advantages and features of the present invention clearer, the method and system for reducing backside bad spots proposed by the present invention are further described in detail in combination with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be understood that the drawings in the specification do not necessarily show the specific structure of the present invention in proportion, and the illustrative features used to illustrate certain principles of the present invention in the drawings in the specification will also be slightly simplified. The specific design features of the present invention disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific application and use environment. And, in the embodiments described below, sometimes the same figure mark is used in common between different drawings to represent the same part or a part with the same function, and its repeated description is omitted. In this specification, similar numbers and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0035] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0036] In order to reduce the impact of bad pixels on the photolithography process, the wafer back is usually cleaned and polished by first using a PVC brush and then using diamond polishing. However, this treatment method is prone to scratching the wafer back. At the same time, it also further increases the rework rate. In the existing treatment method, in order to avoid scratching the wafer back, only a PVC brush is used to clean the wafer back. Therefore, in the existing treatment method, there is still a situation where the bad pixel treatment effect is not ideal.

[0037] The core idea of ​​the present invention is to provide a method for reducing bad spots on the back of a wafer, which can reduce the bad spots on the back of a wafer and reduce the rework rate, and at the same time, can avoid the risk of scratching the back of the wafer.

[0038] In order to realize the above idea, the present invention provides a method for reducing the backside bad points of the wafer. Figure 1 to Figure 2 A specific implementation of a method for reducing wafer backside bad spots is disclosed. The method for reducing wafer backside bad spots includes the following steps S1 to S3.

[0039] Step S1: Obtaining data information on the location and size of a bad spot on the back of a wafer.

[0040] Specifically, refer to Figure 1 As shown, the data information of the location and size of the bad spots on the back of the wafer is obtained by an automatic wafer scanner.

[0041] Step S2: Based on the data information of the position and size of the bad spot on the wafer back, the bad spot on the wafer back is cleaned at a fixed point using a PVA brush 30 .

[0042] Specifically, refer to Figure 1 and Figure 2 As shown, based on the data information of the location and size of the bad spots on the back of the crystal, a cleaning mechanism is used to perform fixed-point cleaning on the bad spots on the back of the crystal. The cleaning mechanism includes a PVA brush 30, a diamond polishing piece 40, a connecting part 20, and a driving device 10. The driving end of the driving device 10 is connected to the connecting part 20. The PVA brush 30 and the diamond polishing piece 40 are installed on the connecting part 20 and are distributed along the radial direction of the connecting part 20 (i.e., the direction perpendicular to the central axis of the driving device 10). The driving device 10 drives the connecting part 20 to rotate while driving the PVA brush 30 and the diamond polishing piece 40 to rotate. The control module connected to the driving device 10 first controls the PVA brush 30 to the location of the bad spots on the back of the crystal to perform positioning cleaning on the bad spots on the back of the crystal. The PVA brush 30 is a soft-bristled brush that can avoid scratching the wafer. For the specific time of cleaning the PVA brush 30, the engineer can set it through the control module to meet the cleaning requirements and remove the bad spots as a requirement.

[0043] Furthermore, in order to improve the removal effect of bad spots, the method for reducing bad spots on the wafer backside also includes: using deionized water to clean the wafer backside. When using deionized water to clean the wafer, in order to further improve the cleaning effect, deionized water can be used for cleaning multiple times.

[0044] Step S3: Based on the data information of the position and size of the bad spot on the crystal back, polishing is performed on the crystal back at the fixed cleaning position.

[0045] Specifically, refer to Figure 1 and Figure 2As shown, after the PVA brush 30 has been cleaned for a set time, the control module moves the diamond polishing piece 40 to the position of the bad spot based on the data information of the position and size of the bad spot on the crystal back, and uses the diamond polishing piece 40 to polish and grind the bad spot after cleaning, thereby reducing the number of bad spots on the crystal back and improving the flatness of the crystal back, so as to reduce the rework rate of the photolithography process and improve the performance and yield of the product. The diamond polishing piece 40 is made of diamond material. By using the diamond polishing piece 40 to polish the crystal back only at a fixed point, scratches on the crystal back can be avoided.

[0046] Furthermore, in order to improve the removal effect of the bad spots, after polishing the bad spots, the wafer back can be cleaned again with deionized water once or multiple times.

[0047] The method for reducing bad spots on the crystal back provided in this embodiment first obtains data information on the specific position and size of the bad spots on the crystal back, and then uses a PVC brush to perform fixed-point cleaning on the bad spots based on the position and size of the bad spots. Thereafter, a diamond polishing piece 40 is used to polish the fixed-point cleaning position, thereby reducing the number of bad spots on the crystal back and improving the flatness of the crystal back, thereby reducing the rework rate of the photolithography process and improving the performance and yield of the product.

[0048] To realize the above idea, the embodiment also discloses a system for reducing bad spots on the back of a wafer, including: an acquisition unit for acquiring data information on the position and size of bad spots on the back of a wafer; a cleaning unit for performing fixed-point cleaning of bad spots on the back of a wafer using a PVA brush 30 based on the data information on the position and size of bad spots on the back of a wafer; and polishing the back of a wafer at the fixed-point cleaning position based on the data information on the position and size of bad spots on the back of a wafer.

[0049] The acquisition unit includes a photographing module and an output module, wherein the photographing module is used to acquire data information on the location and size of the bad spots on the back of the wafer, and the output module is used to transmit the data information to the washing unit. The photographing module and the output module can be automatic wafer scanners.

[0050] The washing unit comprises a cleaning mechanism, a receiving module and a control module. The receiving module is used to receive the data information and transmit the data information to the control module. The control module is used to receive the data information and issue a control instruction to the cleaning mechanism.

[0051] The cleaning mechanism includes a PVA brush 30, a diamond polishing piece 40, a connecting part 20, and a driving device 10, wherein the driving end of the driving device 10 is connected to the connecting part 20, and the PVA brush 30 and the diamond polishing piece 40 are installed on the connecting part 20 and distributed along the radial direction of the connecting part 20. The driving device 10 can be a servo motor or the like. The connecting part 20 is used to carry the PVA brush 30 and the diamond polishing piece 40, and is fixedly connected to the driving end of the driving device 10. The connecting part 20 can be a rod-shaped structure, or any structure or combination thereof such as a plate-shaped structure, which is not limited here. The PVA brush 30 is made of soft hair material to avoid scratching the crystal back. The diamond polishing piece 40 is made of diamond material. The PVA brush 30 and the diamond polishing piece 40 are installed on the connecting part 20. The number of the PVA brush 30 and the diamond polishing piece 40 can be one or more respectively. Preferably, the number of the PVA brushes 30 and the number of the diamond polishing pieces 40 are two respectively, and one PVA brush 30 and one diamond polishing piece 40 are grouped together, and the two groups of PVA brushes 30 and diamond polishing pieces 40 are symmetrically arranged on the surface of the connecting portion 20 .

[0052] The cleaning unit further includes a moving mechanism, which is connected to the control module and the cleaning mechanism, and is used to receive the control instruction output by the control module, and drive the cleaning mechanism to move arbitrarily along the first direction, the second direction and the third direction, wherein the first direction, the second direction and the third direction are perpendicular to each other. That is, the cleaning mechanism can move arbitrarily in a plane parallel to the back of the wafer, and can also move arbitrarily along the first direction, the second direction and the third direction. Figure 2 The moving mechanism can be a moving structure such as a gantry, and the driving device of the moving mechanism is connected to the control module to receive the control command output by the control module, and then drive the cleaning mechanism to move arbitrarily in a plane parallel to the back of the crystal, or move arbitrarily in the direction of the dotted line a. The specific structure of the moving mechanism and the specific control process of the moving mechanism and the control module are already familiar to those skilled in the art, and will not be described in detail here.

[0053] The system for reducing bad spots on the wafer backside also includes: a cleaning unit for cleaning the wafer backside with deionized water. The cleaning unit may be a spray system for spraying deionized water on the wafer to rinse the wafer backside.

[0054] The system for reducing bad spots on the crystal back provided in this embodiment and the method for reducing bad spots on the crystal back provided in this embodiment belong to the same inventive concept. Therefore, the system for reducing bad spots on the crystal back provided in this embodiment has at least all the advantages of the method for reducing bad spots on the crystal back provided in the present invention, and can reduce the number of bad spots on the crystal back and improve the flatness of the crystal back, so as to reduce the rework rate of the lithography process and improve the performance and yield of the product.

[0055] In summary, the above embodiments have detailed descriptions of different configurations of the method and system for reducing backside bad spots. Of course, the above description is only a description of the preferred embodiments of the present invention, and is not any limitation to the scope of the present invention. The present invention includes but is not limited to the configurations listed in the above implementations. Those skilled in the art can draw inferences based on the contents of the above embodiments. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosures shall fall within the scope of protection of the claims.

Claims

1. A method for reducing wafer backside bad spots, characterized in that: include: Obtain the location and size of the bad spots on the back of the wafer; Based on the location and size of the bad spots on the back of the wafer, a PVA brush is used to perform fixed-point cleaning on the bad spots on the back of the wafer. Based on the data information of the position and size of the bad spot on the crystal back, the crystal back at the fixed cleaning position is polished.

2. The method for reducing wafer backside bad spots according to claim 1, characterized in that: The data information of obtaining the position and size of the bad spot on the back of the wafer includes: The location and size of the bad spots on the back of the wafer are obtained through the automatic wafer scanner.

3. The method for reducing wafer backside bad spots according to claim 1, characterized in that: Between using a PVA brush to perform fixed-point cleaning on the bad spots on the back of the crystal and polishing the back of the crystal at the fixed-point cleaning position, the method for reducing the bad spots on the back of the crystal also includes: The back of the wafer was cleaned with deionized water.

4. The method for reducing wafer backside bad spots according to claim 1, characterized in that: In the polishing process of the crystal back at the fixed-point cleaning position based on the data information of the position and size of the bad spot on the crystal back, diamond sand is used to polish the crystal back at the fixed-point cleaning position.

5. A system for reducing wafer backside bad spots, characterized in that: include: An acquisition unit, used to acquire data information on the location and size of a bad spot on the back of a wafer; The cleaning unit is used to perform fixed-point cleaning of the bad spots on the crystal back using a PVA brush based on the data information of the position and size of the bad spots on the crystal back; and polish the crystal back at the fixed-point cleaning position based on the data information of the position and size of the bad spots on the crystal back.

6. The system for reducing wafer backside bad spots according to claim 5, characterized in that: The acquisition unit includes a photographing module and an output module. The photographing module is used to acquire data information on the location and size of bad spots on the back of the wafer, and the output module is used to transmit the data information to the washing unit.

7. The system for reducing wafer backside bad spots according to claim 6, characterized in that: The washing unit includes a cleaning mechanism, a receiving module and a control module; The receiving module is used to receive the data information and transmit the data information to the control module; The control module is used to receive data information and issue control instructions to the cleaning mechanism.

8. The system for reducing wafer backside bad spots according to claim 7, characterized in that: The cleaning mechanism includes a PVA brush, a diamond polishing piece, a connecting part, and a driving device. The driving end of the driving device is connected to the connecting part. The PVA brush and the diamond polishing piece are installed on the connecting part and distributed along the radial direction of the connecting part.

9. The system for reducing wafer backside bad spots according to claim 8, characterized in that: The cleaning unit also includes a moving mechanism, which is connected to the control module and the cleaning mechanism. The moving mechanism is used to receive the control instructions output by the control module and drive the cleaning mechanism to move arbitrarily along a first direction, a second direction and a third direction. The first direction, the second direction and the third direction are perpendicular to each other.

10. The system for reducing wafer backside bad spots according to claim 5, characterized in that: The system for reducing bad spots on the wafer back also includes a cleaning unit for cleaning the wafer back with deionized water.

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