CN114551246A

CN114551246A - Wafer and method for improving height uniformity of electroplating bumps

Info

Publication number: CN114551246A
Application number: CN202210436394.XA
Authority: CN
Inventors: 李春阳; 方梁洪; 彭祎; 罗立辉
Original assignee: Ningbo Chipex Semiconductor Co ltd
Current assignee: Ningbo Chipex Semiconductor Co ltd
Priority date: 2022-04-25
Filing date: 2022-04-25
Publication date: 2022-05-27
Anticipated expiration: 2042-04-25
Also published as: CN114551246B

Abstract

The application relates to a wafer and a method for improving the height uniformity of an electroplated bump, which relate to the field of semiconductor packaging and comprise the following steps: acquiring height difference information; sputtering on the product wafer to form an electroplating seed layer; forming an initial photoresist layer; electroplating at the opening of the initial photoresist layer to form a metal pad; forming a final light resistance layer, wherein the final light resistance layer is provided with an opening to expose the bonding pads corresponding to all the formed metal bumps; electroplating at the opening of the final photoresist layer to form a preliminary metal bump, wherein the preliminary metal bump comprises a copper pillar and a tin cap, and the tin cap is arranged on one side of the copper pillar, which is far away from the electroplating seed layer; removing the final photoresist layer and the electroplating seed layer; and reflowing the product wafer to form a molded metal bump. The electroplating bump height adjusting method has the advantages that the final heights of the electroplating bumps among different sizes of reflowing after electroplating are made to be the same, and the uniformity of the heights of the electroplated metal bumps is improved.

Description

Wafer and method for improving height uniformity of electroplating bumps

Technical Field

The present disclosure relates to the field of semiconductor packaging, and more particularly, to a wafer and a method for improving uniformity of height of plated bumps.

Background

Wafer level packaging belongs to a mode of cutting after wafer packaging, and a wafer operation mode in an integrated circuit chip manufacturing factory is adopted, namely packaging is completed on a whole wafer and then cutting is carried out, and a large number of finished chips are obtained at one time.

Wafer Bumping (Bumping) is one of the key technologies for wafer level packaging. Flip Chip (FC) is to form a layer of metal bumps (Bump) arranged in an array on the surface of an electrical layer of a Chip by a Bump process of wafer level packaging, and then directly connect the metal bumps with a substrate to form electrical interconnection. With the development of wafer manufacturing processes, the chip size is smaller and smaller, and the I/O density on the surface of the chip is higher and higher along with the increase of the functional requirements of products. Due to multiple considerations of chip space and product electrical performance, the design schemes of designing metal bumps with different sizes according to different pin functions in a single chip are increasingly applied and developed

In view of the above-mentioned related art, the inventors believe that the electroplated metal bumps (Cu + n) have a height difference after reflow due to the difference in the sizes of the metal bumps, and the height difference of the metal bumps is larger when the size difference of the metal bumps is larger. When the height difference of the metal bumps exceeds the process capability of flip chip, insufficient soldering is generated, and the chip cannot be used.

Disclosure of Invention

In order to solve the problem that the larger the size difference of the metal bumps is, the larger the height difference of the metal bumps is, insufficient solder is generated, and a chip cannot be used, the application provides a wafer and a method for improving the height uniformity of electroplated bumps.

In a first aspect, the method for improving the uniformity of the height of the plated bump provided by the present application adopts the following technical scheme:

a method for improving the uniformity of the height of an electroplated bump is applied to a wafer with the same chip, and comprises the following steps:

acquiring height difference information among the molded metal lugs with different sizes, defining the molded metal lug with the highest height as a target metal lug, and defining the rest molded metal lugs as distinguishing metal lugs;

sputtering on the product wafer to form an electroplating seed layer;

coating glue, exposing and developing on the electroplating seed layer to form an initial photoresist layer, wherein an opening is formed in the initial photoresist layer to expose a bonding pad corresponding to the metal bump;

electroplating at the opening of the initial photoresist layer to form a metal cushion block, wherein the height of the metal cushion block is equal to the height value corresponding to the height difference information;

removing the initial photoresist layer, coating glue, exposing and developing on the electroplating seed layer again to form a final photoresist layer, wherein the final photoresist layer is provided with openings to expose the bonding pads corresponding to all the formed metal bumps;

electroplating at the opening of the final photoresist layer to form a preliminary metal bump;

removing the final photoresist layer and the electroplating seed layer;

and reflowing the product wafer to form a molded metal bump.

By adopting the technical scheme, the metal cushion block with the height difference information can be compensated by electroplating the height on the bonding pad of the metal bump with the smaller size, then the metal bump with the small size is electroplated on the basis of the metal cushion block, and the metal bump with the large size is electroplated on the original bonding pad, so that the final heights of the electroplated bumps with different sizes reflowed after electroplating are the same, and the uniformity of the heights of the electroplated metal bumps is improved.

Optionally, the method for obtaining height difference information of the formed metal bump includes:

sputtering a test wafer to form a plating seed layer;

coating glue, exposing and developing on the electroplating seed layer to form a final light resistance layer, wherein the final light resistance layer is provided with an opening to expose the bonding pads corresponding to all the formed metal bumps;

removing the final photoresist layer and reflowing the test wafer to form a formed metal bump;

and measuring the height of the formed metal bump and then calculating to obtain height difference information.

By adopting the technical scheme, the metal bump without the metal cushion block is formed on the test wafer by electroplating in advance, the height difference is measured in advance, the subsequent product is not required to be measured, the measuring process is consistent with the actual condition, the measuring process is real, and the accuracy of height measurement is improved.

Optionally, the openings of the initial photoresist layer correspond to the distinguishing metal bumps one to one, the sizes of the openings are larger than the sizes of the distinguishing metal bumps, and the size of the opening of the final photoresist layer is equal to the sizes of all the corresponding metal bumps.

By adopting the technical scheme, the size of the initial photoresist layer is larger than that of the final photoresist layer, so that the size of the metal cushion block formed by the initial photoresist layer is larger than that of the metal lug formed by electroplating above the initial photoresist layer, the metal lug is more stable in the electroplating process and is not easy to incline or even bend, and the electroplating reliability of the metal lug is improved.

Optionally, before forming a plating seed layer on the test wafer or the product wafer by sputtering, the method includes the following steps: and forming a PI protective layer through gluing, exposing, developing and curing, wherein an opening is formed in the PI protective layer to expose the bonding pads corresponding to all the formed metal bumps.

By adopting the technical scheme, the PI protective layer has certain protective effect and buffering effect on the surface of the wafer, so that the wafer is not easily damaged when subsequent operation is performed on the surface of the wafer, and certain stability is provided.

Optionally, if there are metal bumps of at least three sizes, the method for obtaining height difference information includes the following steps:

sorting the molding metal bumps with different sizes from large to small according to the sizes to form a molding metal bump sequence;

calculating the target height difference between the formed metal bumps in the formed metal bump sequence and the target metal bumps one by one to form a target height difference sequence;

an average between the target height differences in the sequence of target height differences is calculated to form target height difference information.

By adopting the technical scheme, when the metal bumps are in a plurality of sizes, all the metal bumps and the metal bump with the largest size are subjected to numerical subtraction to obtain height difference information, and then the average height difference value is calculated to reduce the height difference among the metal bumps with different sizes and improve the uniformity of the height of the electroplated metal bumps.

Optionally, if there are metal bumps of at least three sizes, electroplating at the opening of the initial photoresist layer to form a metal pad, removing the initial photoresist layer, coating glue, exposing, and developing on the electroplating seed layer again to form a final photoresist layer, and the step of providing an opening on the final photoresist layer to expose the pads corresponding to all the formed metal bumps may further include the following steps:

calculating adjacent height difference information according to adjacent formed metal bumps in the formed metal bump sequence to form an adjacent height difference sequence;

sequentially executing a photoresist layer forming step and a metal cushion block forming step according to a current formed metal lug in the formed metal lug sequence and adjacent height difference information in an adjacent height difference sequence corresponding to the current formed metal lug;

wherein the step of forming the photoresist layer comprises:

coating glue, exposing and developing on the electroplating seed layer to form a light resistance layer, wherein an opening is formed in the light resistance layer to expose a bonding pad corresponding to a formed metal bump behind a current formed metal bump in the formed metal bump sequence;

wherein, the metal cushion block molding step includes:

electroplating at the opening of the photoresist layer to form a corresponding metal cushion block according to the adjacent height difference information corresponding to the current forming metal bump and the current forming metal image;

and repeating the forming step of the light resistance layer and the forming step of the metal cushion block in sequence according to the formed metal bumps in the formed metal bump sequence and the adjacent height difference information in the adjacent height difference sequence until a final light resistance layer is formed.

By adopting the technical scheme, the photoresist layer with the height difference of the metal lugs with the adjacent sizes is gradually formed, then the metal cushion blocks with the same information as the adjacent height difference are gradually formed, and finally the metal cushion blocks meeting the requirements are arranged below the metal lugs with different sizes so as to make up the difference between all the metal lugs and the first metal lug and improve the uniformity of the height of the electroplated metal lug.

Optionally, the size of the opening of the photoresist layer is gradually reduced at the position corresponding to the metal pad, and finally the size of the opening of the photoresist layer is equal to the size of all the corresponding metal bumps.

By adopting the technical scheme, the opening size of the photoresist layer is gradually reduced, so that all the electroplating base points of the metal cushion blocks have certain stability, and the stability and the reliability of the electroplated metal bump are improved.

Optionally, the step of sequentially performing photoresist layer formation further comprises:

and forming a next corresponding photoresist layer on the photoresist layer directly through gluing, exposing and developing, wherein the height of the next corresponding photoresist layer is greater than the adjacent height difference information in the corresponding adjacent height difference sequence.

By adopting the technical scheme, the next photoresist layer is directly formed, and the height is greater than the height value of the adjacent height difference information, so that the photoresist layer is not required to be removed in the forming process, the step of removing the middle photoresist layer and the glue amount required by gluing are reduced, the middle step of the operation flow for improving the height uniformity is reduced, and the wafer packaging speed of the product is improved.

In a second aspect, the method for improving the uniformity of the height of the plated bump provided by the present application adopts the following technical scheme:

a method for improving the uniformity of the height of an electroplated bump is applied to a wafer with at least two chips, and comprises the following steps:

acquiring height difference information among the molded metal lugs on different chips, defining the molded metal lug with the highest height as a target metal lug, and defining the rest molded metal lugs as distinguishing metal lugs;

sputtering on the product wafer to form an electroplating seed layer;

removing the final photoresist layer and the electroplating seed layer;

and reflowing the product wafer to form a molded metal bump.

By adopting the technical scheme, the metal cushion block with the height difference information can be compensated by electroplating the height on the chip with the metal bump with the smaller size, then the metal bump with the small size is electroplated on the basis of the metal cushion block, and the metal bump with the large size is electroplated on the chip with the metal bump with the larger size, so that the final heights of the electroplated bumps with different sizes reflowed after electroplating are the same, and the uniformity of the heights of the electroplated metal bumps on different chips is improved.

In a third aspect, the present application provides a wafer, which adopts the following technical solution:

a wafer, comprising:

the chip is used as a bearing base and is provided with a bonding pad of a plated metal bump;

the PI protective layer is arranged on the chip and is provided with an opening so as to expose the bonding pads corresponding to all the formed metal bumps;

the electroplating seed layer is arranged at the openings of the PI protective layer and is electrically connected with the bonding pad on the chip;

the metal cushion block is arranged on the opening of the PI protective layer and is electrically connected with the electroplating seed layer which is connected with the distinguishing metal bump so as to make up for height difference information;

the target metal bump comprises a target copper pillar and a target tin cap, the target copper pillar is arranged on the electroplating seed layer and positioned at the opening of the PI protective layer, and the target tin cap is arranged on one side, away from the electroplating seed layer, of the target copper pillar;

and distinguishing the metal bump, including distinguishing the copper column and distinguishing the tin cap, the distinguishing copper column is arranged on one side of the metal cushion block, which is far away from the electroplating seed layer, and the distinguishing tin cap is arranged on one side of the distinguishing copper column, which is far away from the electroplating seed layer.

By adopting the technical scheme, the metal cushion block is arranged on the bonding pad of the metal lug with smaller size, so that the final heights of the electroplated lugs among different sizes reflowed after electroplating are the same, and the uniformity of the heights of the electroplated metal lugs is improved.

In summary, the present application includes the following beneficial technical effects:

1. the uniformity of the height of the electroplated metal bump is improved.

Drawings

Fig. 1 is a schematic structural diagram of a wafer in embodiment 1 of the present application.

Fig. 2 is a top view of a wafer according to example 1 of the present application.

Fig. 3 is a schematic structural diagram of a chip in embodiment 1 of the present application.

Fig. 4 is a schematic diagram of forming a PI protection layer on a chip in embodiment 1 of the present application.

Fig. 5 is a schematic diagram of forming a plating seed layer on a chip in embodiment 1 of the present application.

Fig. 6 is a schematic structural diagram of a test wafer in embodiment 1 of the present application.

FIG. 7 is a schematic diagram of an initial photoresist layer formed on a chip in example 1 of the present application.

Fig. 8 is a schematic diagram of forming a metal pad on a chip in embodiment 1 of the present application.

FIG. 9 is a schematic diagram of removing the initial photoresist layer on the chip in the embodiment 1 of the present application.

FIG. 10 is a schematic diagram of a final photoresist layer formed on a chip in example 1 of the present application.

Fig. 11 is a schematic diagram of forming a preliminary metal bump on a chip in embodiment 1 of the present application.

Fig. 12 is a schematic diagram of the chip in example 1 of the present application for removing the final photoresist layer and the plating seed layer.

Fig. 13 is a schematic structural diagram of a test wafer in embodiment 6 of the present application.

Fig. 14 is a schematic structural diagram of a wafer according to embodiment 6 of the present application.

Description of reference numerals: 1. a chip; 2. distinguishing metal bumps; 21. distinguishing copper columns; 22. distinguishing tin caps; 3. a target metal bump; 31. a target copper pillar; 32. a target tin cap; 4. a pad; 5. an incoming material passivation layer; 6. a PI protective layer; 7. electroplating a seed layer; 8. an initial photoresist layer; 9. a metal cushion block; 10. and finally, forming a photoresist layer.

Detailed Description

The present application is described in further detail below with reference to fig. 1-14.

The embodiment of the application discloses a wafer.

Referring to fig. 1, a wafer includes a chip 1, a PI protection layer 6, a plating seed layer 7, a metal pad 9, a target metal bump 3, and a discrimination metal bump 2.

The chip 1 is located on a wafer as a carrier base, and has pads 4 with plated metal bumps and a incoming passivation layer 5 thereon. The PI protective layer 6 is positioned on the chip 1 and is provided with an opening so as to expose the bonding pads 4 corresponding to all the formed metal bumps; a plating seed layer 7 is formed on the openings of the PI protection layer 6 and the PI protection layer 6 in a sputtering mode and is electrically connected with the bonding pad 4 on the chip 1; and electroplating a metal cushion block 9 on the opening of the PI protective layer 6, wherein the metal cushion block 9 is positioned at the opening of the PI protective layer 6 and is used for being electrically connected with the area of the electroplating seed layer 7 corresponding to the distinguishing metal bump 2 so as to make up the height difference between the distinguishing metal bump 2 and the target metal bump 3 after reflow.

Referring to fig. 1 and 2, the metal bumps on the chip 1 are different in size, and therefore, the target metal bump 3 includes a target copper pillar 31 and a target tin cap 32, the target copper pillar 31 is plated on the plating seed layer 7 and is located at the opening of the PI protection layer 6, and the target tin cap 32 is plated on one side of the target copper pillar 31 away from the plating seed layer 7. The distinguishing metal bump 2 comprises a distinguishing copper pillar 21 and a distinguishing tin cap 22, the distinguishing copper pillar 21 is electroplated on one side of the metal cushion block 9 far away from the electroplating seed layer 7, and the distinguishing tin cap 22 is arranged on one side of the distinguishing copper pillar 21 far away from the electroplating seed layer 7.

The embodiment of the application also discloses a method for improving the height uniformity of the electroplated bump.

Example 1

A method for improving the uniformity of the height of an electroplated bump is applied to a wafer with the same chip 1, and comprises the following steps:

step 100: and forming a PI protective layer 6 on the test wafer through gluing, exposing, developing and curing, wherein an opening is formed in the PI protective layer 6 to expose the bonding pad 4 corresponding to all the formed metal bumps.

Referring to fig. 3 and 4, the coating process is to apply photoresist on the surface of the test wafer. The exposure process needs to be realized through a mask plate, light is transmitted on the photoresist through a design pattern on the mask plate, so that the photoresist at the opening of the corresponding pad keeps small molecules, and the photoresist at other positions is polymerized into large molecules. And the development is to dissolve and wash out the micromolecules at the opening of the corresponding bonding pad through a developing solution, so that the photoresist coated on the test wafer can be provided with an opening of a design pattern corresponding to the mask plate, and the opening exposes all the bonding pads 4 corresponding to the formed metal bumps, thereby facilitating the metal bumps to be electroplated on the bonding pads 4 and connected with the chip 1 in the subsequent process. And then, curing the photoresist to form a PI protective layer 6 on the surface of the wafer, so as to protect the wafer and the buffer layer. It should be noted that the function of the test wafer is to simulate an actual product, and may also be implemented virtually directly on simulation software, and the simulation software is used to simulate the actual product so as to implement single verification, so as to obtain the height difference between metal bumps of different sizes on the actual wafer.

Step 101: a plating seed layer 7 is formed on the test wafer by sputtering.

Referring to fig. 5, the plating seed layer 7 is formed by sputtering, and the openings of the PI protection layer 6 and the PI protection layer 6 are sputtered to form 1000A Ti +4000A Cu, which facilitates subsequent formation of metal bumps on the plating seed layer 7 by plating.

Step 102: and gluing, exposing and developing the electroplating seed layer 7 to form a final photoresist layer 10, wherein an opening is formed in the final photoresist layer 10 to expose the bonding pad 4 corresponding to all the formed metal bumps.

The final photoresist layer 10 is similar to the PI protection layer 6, and is intended to facilitate subsequent metal bump plating. The difference from the PI protective layer 6 is that the photoresist layer does not need to be cured, so that the subsequent removal is convenient. The electroplating seed layer 7 is coated with glue, and then exposure and development are carried out through the mask plate, so that openings of corresponding design patterns on the mask plate can be formed on the photoresist coated on the electroplating seed layer 7, the openings expose the electroplating seed layer 7 corresponding to all formed metal bumps, and the metal bumps can be conveniently electroplated on the electroplating seed layer 7 and connected with the chip 1 in the subsequent process. In the present embodiment, the opening size of the final photoresist layer 10 is the same as the opening size of the corresponding metal bump, so that the metal bump formed in the final photoresist layer 10 is limited by the final photoresist layer 10.

Step 103: and electroplating at the opening of the final photoresist layer 10 to form a preliminary metal bump.

Referring to fig. 6, a preliminary metal bump conforming to the product design is formed at the opening on the wafer after the preparation work is completed in the above steps 100-102, where the preliminary metal bump includes a copper pillar electrically connected to the plating seed layer 7 and a tin cap above the copper pillar for facilitating soldering, and it should be noted that the tin cap is in an unmolded state and can be formed only by a subsequent reflow operation.

Step 104: after removing the final photoresist layer 10, the test wafer is reflowed to form the formed metal bumps.

As shown in fig. 6, after reflow, the solder caps form arc-shaped solder joints according to the size to form the shaped metal bumps. Finally, the photoresist layer 10 is removed by dissolving the photoresist in the photoresist removing solution, wherein the photoresist removing solution can dissolve macromolecules and micromolecules, and then the test wafer electroplated with the metal bump is reflowed to obtain the formed metal bump with the size.

Step 105: and measuring the heights of the molded metal bumps, and calculating to obtain height difference information, wherein the molded metal bump with the highest height is defined as a target metal bump 3, and the rest molded metal bumps are defined as distinguishing metal bumps 2.

The target metal bump 3 is a molded metal bump having the largest size, and the distinguishing metal bump 2 is a molded metal bump other than the target metal bump 3. The height of the target metal bump 3 is the highest because of its largest size, and the purpose of the definition is to establish the target of the comparison. The height difference information is the difference between the heights of the molded metal bumps with different sizes on the same wafer before processing. The three-dimensional coordinates of the corresponding formed metal bumps can be obtained by scanning through an AOI (automated Optical inspection) automatic scanning machine, then the heights of the corresponding formed metal bumps can be screened out from the contents, and then the heights are numerically subtracted to obtain corresponding height difference information.

Step 106: and forming a PI protective layer 6 on the product wafer through gluing, exposing, developing and curing, wherein an opening is formed in the PI protective layer 6 to expose the bonding pads 4 corresponding to all the formed metal bumps.

Referring to fig. 3 and 4, the PI protection layer 6 is similar to the PI protection layer 100 except that the field of formation is different, and the PI protection layer 100 is formed on a test wafer and is formed on a product wafer for the purpose of protecting the product wafer. Openings are formed in the PI protection layer 6 of the product wafer to expose all the pads 4 corresponding to the formed metal bumps, and the openings are also used for protecting the wafer and the buffer layer.

Step 107: and sputtering to form a plating seed layer 7 on the product wafer.

Referring to fig. 5, similar to the plating seed layer 7 in step 101, sputtering is performed on the PI protection layer 6 and the opening of the PI protection layer 6, and the PI protection layer is composed of 1000A Ti +4000A Cu, so that a metal bump is conveniently formed on the plating seed layer 7 by plating in the subsequent step.

Step 108: and gluing, exposing and developing the electroplating seed layer 7 to form an initial photoresist layer 8, wherein an opening is formed in the initial photoresist layer 8 to expose the bonding pad 4 corresponding to the distinguishing metal bump 2.

Referring to fig. 7, the initial photoresist layer 8 is similar to the final photoresist layer 10 formed for the purpose of facilitating subsequent electroplating of metal bumps. The difference from the final photoresist layer 10 is that the openings expose the openings of the pads 4 corresponding to the formed metal bumps except the target metal bump 3. As with the final photoresist layer 10, it is not required to be cured after formation to facilitate subsequent removal. The electroplating seed layer 7 is coated with glue, and then a new mask plate is used for exposure and development, wherein the mask plate is only provided with openings corresponding to the bonding pads 4 of the small-sized metal bumps and covers the openings corresponding to the bonding pads 4 of the target metal bumps 3, so that the initial photoresist layer 8 is provided with openings at positions corresponding to the bonding pads 4 of the small-sized metal bumps after passing through the developing solution, and the height difference information is conveniently compensated in the subsequent process.

Step 109: and electroplating at the opening of the initial photoresist layer 8 to form a metal pad 9, wherein the height of the metal pad 9 is equal to the height value corresponding to the height difference information.

Referring to fig. 8 and 9, the metal spacers 9 are used to compensate for the height difference between the metal bumps of different sizes, and the metal spacers 9 are plated to ensure the connectivity so as not to affect the connection between the metal bumps and the chip 1. In this embodiment, the size of the opening of the initial photoresist layer 8 is larger than the size of the other formed metal bumps except the target metal bump 3, so that the size of the formed metal pad 9 is larger than the size of the metal bump to be electroplated above the metal pad 9, and the stability and reliability of electroplating are improved.

Step 110: after the initial photoresist layer 8 is removed, glue is applied again on the plating seed layer 7, exposure and development are carried out to form a final photoresist layer 10, and openings are formed in the final photoresist layer 10 to expose the bonding pads 4 corresponding to all the formed metal bumps.

As shown in fig. 9 and 10, after the metal pad 9 is formed by the initial photoresist layer 8, the initial photoresist layer 8 is removed by the photoresist stripper, and then the final photoresist layer 10 is formed again and opened for the subsequent electroplating process of the metal bump. Here, the size of the opening of the final photoresist layer 10 is consistent with the size of the formed metal bump, so as to limit the forming size of the metal bump. Here, exposure and development are performed through the same mask as in step 102, so that openings are formed in the final photoresist layer 10 at the pads 4 corresponding to all the formed metal bumps, so as to allow metal bumps with different sizes to be plated.

Step 111: and electroplating at the opening of the final photoresist layer 10 to form a preliminary metal bump.

As shown in fig. 11, this step is similar to step 103, except that the small-sized metal bumps are not plated directly on the plating seed layer 7, but are plated on the formed metal pads 9, while the large-sized metal bumps are plated directly on the plating seed layer 7, in order that the heights of the metal bumps after reflow are the same.

Step 112: the final photoresist layer 10 and the plating seed layer 7 are removed.

Referring to fig. 12, the final method for removing the photoresist layer 10 is to dissolve and remove photoresist through a photoresist removing solution, where macromolecules and small molecules can be dissolved in the photoresist removing solution, and then the product wafer electroplated with the metal bump is reflowed to obtain a formed metal bump with the size. In order to connect the metal bumps on the product wafer with the chip 1 independently, the plating seed layer 7 needs to be removed to avoid short circuit between the metal bumps. And the removing process of the plating seed layer 7 can be carried out by etching with an etching solution so as to facilitate the reflow.

Step 113: and reflowing the product wafer to form a molded metal bump.

Referring to fig. 1, although the sizes of the formed metal bumps after reflow are not uniform, the heights of the formed metal bumps with small sizes are uniform with those of the formed metal bumps with large sizes under the action of the metal pads 9, so that the uniformity of the heights of the plated metal bumps is improved.

Example 2

The difference between this embodiment and embodiment 1 is that the sizes of the metal bumps are at least three, and the method for acquiring the height difference information includes the following steps:

step 1051: and sorting the forming metal bumps with different sizes from large to small to form a forming metal bump sequence.

The forming metal bump sequence is an arrangement sequence of the programmed metal bumps after being sorted from large to small in size. And (3) finally forming the product wafer with metal bumps of at least three sizes, and performing simulation in advance in the design process, wherein the simulation process is consistent with the step 101 and the step 104, finally forming the formed metal bumps of different sizes, the heights of the formed metal bumps are different, all the formed metal bumps of different sizes are classified for convenience of identification, the formed metal bumps of the same size are defined as one type, and then the formed metal bumps are numbered from large to small, and the smaller the number is, the larger the size is.

Step 1052: calculating the target height difference between the formed metal bumps in the formed metal bump sequence and the target metal bumps one by one to form a target height difference sequence;

the calculation is numerical subtraction, and the purpose of the calculation is to obtain the height difference between the formed metal bump of each size and the metal bump of the maximum size.

Step 1053: an average between the target height differences in the sequence of target height differences is calculated to form target height difference information.

The calculation mode is that a plurality of height difference values are added, and then the average value is taken to define the height difference information, so that the advantage is that the process of the middle pad metal cushion block 9 is only once, although the height difference exists, the height difference is reduced as far as possible and is basically in a positive and negative range, and the probability of cold joint in the welding process is reduced.

Example 3

The present embodiment is different from embodiment 1 in that,

step 1054: and calculating adjacent height difference information according to adjacent molded metal bumps in the molded metal bump sequence to form an adjacent height difference sequence.

The calculation method comprises the steps of randomly selecting a metal bump with one size, then selecting a metal bump with the size of an adjacent number from the classified numbers, and calculating the height difference between the metal bumps and the adjacent numbers.

Step 1055: and sequentially executing a photoresist layer forming step and a metal cushion block forming step according to the current formed metal lug in the formed metal lug sequence and the adjacent height difference information in the adjacent height difference sequence corresponding to the current formed metal lug.

The step of forming the light resistance layer and the step of forming the metal cushion block are executed in sequence and are executed circularly, when the current formed metal convex block is replaced according to the sequence of the formed metal convex block, the light resistance layer is changed along with the current formed metal convex block, and therefore the light resistance layer and the metal cushion block corresponding to the current formed metal convex block are formed.

Wherein the step of forming the photoresist layer comprises:

step 10551: and gluing, exposing and developing the electroplating seed layer to form a photoresist layer, wherein the photoresist layer is provided with an opening to expose a bonding pad corresponding to the formed metal bump behind the current formed metal bump in the formed metal bump sequence.

The photoresist layer is formed after the processes of gluing, exposing and developing. The difference from the final photoresist layer 10 is that the opening thereof exposes the bonding pad corresponding to the formed metal bump after the current formed metal bump in the formed metal bump sequence. As with the final photoresist layer 10, it is not required to be cured after formation to facilitate subsequent removal. By coating the electroplating seed layer 7 with glue and then exposing and developing through a new mask plate, the mask plate is only provided with openings corresponding to the bonding pads 4 of the formed metal bumps behind the formed metal bumps and covers the openings corresponding to the formed metal bumps behind the formed metal bumps and in front of the formed metal bumps in sequence, so that the photoresist layer is provided with openings at positions corresponding to the bonding pads 4 of the metal bumps with small sizes after passing through the developing solution, and the subsequent compensation of the adjacent height difference information in the adjacent height difference sequence is facilitated.

Wherein, the metal cushion block molding step includes:

step 10552: and electroplating at the opening of the photoresist layer to form a corresponding metal cushion block 9 according to the adjacent height difference information corresponding to the current forming metal bump and the current forming metal image.

The height of the metal cushion block 9 is equal to the adjacent height difference information in the adjacent height difference sequence corresponding to the current forming metal lug.

Step 1056: and repeating the photoresist layer forming step and the metal cushion block forming step in sequence according to the formed metal bumps in the formed metal bump sequence and the adjacent height difference information in the adjacent height difference sequence until the final photoresist layer 10 is formed.

When the formed metal bumps are changed, corresponding photoresist layers and metal cushion blocks are formed in the same way, and then the repeated process is stopped when the final photoresist layer is formed, so that the height difference between the final photoresist layer and the target metal cushion blocks can be made up by the heights of all the metal cushion blocks.

In this embodiment, the opening size of the photoresist layer is gradually reduced at the position corresponding to the metal pad, and the opening size of the final photoresist layer is equal to the size of all the corresponding metal bumps, so as to form the metal pads 9 which are gradually overlapped and gradually reduced in size, so as to gradually support the metal pads 9 above, thereby improving the reliability of the support of the metal pads 9.

Example 4

This embodiment is different from embodiment 3 in that,

step 10553: and coating glue, exposing and developing on the electroplating seed layer 7 to form a photoresist layer, wherein an opening is formed in the photoresist layer, and only the bonding pad 4 corresponding to the currently-formed metal bump is exposed through the opening.

Similarly, this embodiment is also performed on the chip 1 having the metal bumps of three or more sizes. But the difference is that only the opening of the current forming metal bump corresponding to the pad 4 is opened on the photoresist layer, so that the electroplating can be directly performed according to the corresponding height difference in the target height difference sequence.

Step 10554: and electroplating at the opening of the photoresist layer to form a current metal cushion block, wherein the height of the current metal cushion block 9 is equal to the height difference corresponding to the current metal cushion block in the target height difference sequence.

Here, the individual metal pads 9 are plated in each area to a height that compensates for the difference in height between the formed metal bumps and the target metal bumps. Repeated electroplating in other areas is not needed, and electroplating is convenient.

Example 5

This embodiment is different from embodiment 3 in that,

step 10555: and forming a next corresponding photoresist layer on the photoresist layer directly through gluing, exposing and developing, wherein the height of the next corresponding photoresist layer is greater than the adjacent height difference information in the corresponding adjacent height difference sequence.

Because only the opening on the corresponding photoresist layer exposes the bonding pad 4 corresponding to the formed metal bump behind the current formed metal bump in the formed metal bump sequence. Therefore, only the next corresponding photoresist layer needs to be coated on the original basis, so that the opening of the bonding pad 4 corresponding to the current formed metal bump in the formed metal bump sequence is covered.

Example 6

Referring to fig. 13 and 14, a method for improving uniformity of height of plated bumps, applied to a same wafer with different chips 1 having metal bumps with different sizes, includes:

step 200: and forming a PI protective layer 6 on the test wafer through gluing, exposing, developing and curing, wherein an opening is formed in the PI protective layer 6 to expose the bonding pad 4 corresponding to all the formed metal bumps.

The coating process is to coat photoresist on the surface of the test wafer. The exposure process needs to be realized through a mask plate, light is transmitted on the photoresist through a design pattern on the mask plate, so that the photoresist at the opening of the corresponding pad keeps small molecules, and the photoresist at other positions is polymerized into large molecules. And the development is to dissolve and wash out the micromolecules at the opening of the corresponding bonding pad through a developing solution, so that the photoresist coated on the test wafer can be provided with an opening of a design pattern corresponding to the mask plate, and the opening exposes all the bonding pads 4 corresponding to the formed metal bumps, thereby facilitating the metal bumps to be electroplated on the bonding pads 4 and connected with the chip 1 in the subsequent process. And then, curing the photoresist to form a PI protective layer 6 on the surface of the wafer, so as to protect the wafer and the buffer layer. It should be noted that the test wafer is used to simulate an actual product, and may also be directly implemented virtually on simulation software, and the simulation software is used to perform simulation to implement single verification, so as to obtain the height difference between the metal bumps on different chips 1 on the actual wafer.

Step 201: a plating seed layer 7 is formed on the test wafer by sputtering.

The electroplating seed layer 7 is formed by sputtering, the openings of the PI protective layer 6 and the PI protective layer 6 are sputtered, and the electroplating seed layer is composed of 1000A Ti +4000A Cu, so that metal bumps can be conveniently formed on the electroplating seed layer 7 by electroplating.

Step 202: and gluing, exposing and developing the electroplating seed layer 7 to form a final photoresist layer 10, wherein an opening is formed in the final photoresist layer 10 to expose the bonding pad 4 corresponding to all the formed metal bumps.

The final photoresist layer 10 is similar to the PI protection layer 6, and is intended to facilitate subsequent metal bump plating. The difference from the PI protective layer 6 is that the photoresist layer does not need to be cured, so that the subsequent removal is convenient. The electroplating seed layer 7 is coated with glue, and then exposure and development are carried out through the mask plate which is the same as that in the step 100, so that openings of corresponding design patterns on the mask plate can be formed on the photoresist coated on the electroplating seed layer 7, and the openings expose the electroplating seed layer 7 corresponding to all formed metal bumps, so that the metal bumps can be conveniently electroplated on the electroplating seed layer 7 and connected with the chip 1 in the subsequent process. In the present embodiment, the size of the opening of the final photoresist layer 10 is the same as the size of the opening of the corresponding metal bump, so that the metal bump formed in the final photoresist layer 10 is limited by the final photoresist layer 10.

Step 203: and electroplating at the opening of the final photoresist layer 10 to form a preliminary metal bump.

Then, a preliminary metal bump conforming to the product design is formed at the opening on the wafer after the preparation work is completed in the above step 200, wherein the preliminary metal bump includes a copper pillar electrically connected to the plating seed layer 7 and a tin cap above the copper pillar for facilitating soldering, and it is noted that the tin cap is in an unformed state and can be formed only by a subsequent reflow operation.

Step 204: after removing the final photoresist layer 10, the test wafer is reflowed to form the formed metal bumps.

And after reflowing, the tin cap forms arc-shaped welding spots according to the size to form the formed metal convex blocks. Finally, the photoresist layer 10 is removed by dissolving and removing photoresist through a photoresist removing solution, wherein macromolecules and micromolecules can be dissolved in the photoresist removing solution, and then the test wafer electroplated with the metal bump is reflowed to obtain the formed metal bump with the size.

Step 205: and measuring the height of the molded metal bump, calculating to obtain height difference information, and defining the molded metal bump with the highest height as a target metal bump 3.

The target metal bump 3 is a molded metal bump with the largest size among different chips 1, and the height of the target metal bump 3 is the highest due to the largest size, and the purpose of the definition is to establish a comparison target. The height difference information is the difference between the heights of the molded metal bumps with different sizes before being processed on different chips 1 of the same wafer. The three-dimensional coordinates of the corresponding formed metal bumps can be obtained by scanning through an AOI (automated Optical inspection) automatic scanning machine, then the heights of the corresponding formed metal bumps can be screened out from the contents, and then the heights are numerically subtracted to obtain corresponding height difference information.

Step 205: height difference information between the molded metal bumps on different chips 1 on the same wafer is obtained, and the molded metal bump with the highest height is defined as a target metal bump 3.

The manner of acquisition here is identical to that of step 100-105, except that the measured metal bumps are plated on different chips 1. Here two or more chips 1 are located on the same wafer. The height difference information can be obtained by integrating the height difference information obtained on the two chips 1.

Step 206: and sputtering to form a plating seed layer 7 on the product wafer.

Prior to this step, if necessary, a PI protection layer 6 may be formed to buffer and protect the subsequent package. Similar to the electroplating seed layer 7 in the step 101, sputtering is performed on the PI protection layer 6 and the opening of the PI protection layer 6, and the PI protection layer is composed of 1000A Ti +4000A Cu, so that a metal bump is conveniently formed on the electroplating seed layer 7 by electroplating in the subsequent step.

Step 207: and coating glue, exposing and developing on the electroplating seed layer 7 to form an initial photoresist layer 8, wherein an opening is formed on the initial photoresist layer 8 to expose the bonding pad 4 corresponding to the other formed metal bumps except the target metal bump 3.

The initial photoresist layer 8 is similar to the final photoresist layer 10 formed for the purpose of facilitating subsequent metal bump plating. The difference from the final photoresist layer 10 is that the openings expose the openings of the pads 4 corresponding to the formed metal bumps except the target metal bump 3. As with the final photoresist layer 10, it is not required to be cured after formation to facilitate subsequent removal. By coating the electroplating seed layer 7 with glue and then exposing and developing through a new mask plate, the mask plate is only provided with openings corresponding to the bonding pads 4 of the small-sized metal bumps and covers the openings corresponding to the bonding pads 4 of the target metal bumps 3, so that the initial photoresist layer 8 is provided with openings at positions corresponding to the bonding pads 4 of the small-sized metal bumps after passing through the developing solution, and the height difference information is conveniently compensated in the subsequent process.

Step 208: and electroplating at the opening of the initial photoresist layer 8 to form a metal pad 9, wherein the height of the metal pad 9 is equal to the height value corresponding to the height difference information.

The metal spacers 9 are used for compensating the height difference between the metal bumps with different sizes, and the metal spacers 9 are electroplated at the position so as not to influence the connection between the metal bumps and the chip 1, so as to ensure the connectivity. In this embodiment, the size of the opening of the initial photoresist layer 8 is larger than the size of the other formed metal bumps except the target metal bump 3, so that the size of the formed metal pad 9 is larger than the size of the metal bump to be electroplated above the metal pad 9, and the stability and reliability of electroplating are improved.

Step 209: after the initial photoresist layer 8 is removed, glue is applied again on the plating seed layer 7, exposure and development are carried out to form a final photoresist layer 10, and openings are formed in the final photoresist layer 10 to expose the bonding pads 4 corresponding to all the formed metal bumps.

After the metal pad 9 is formed by the initial photoresist layer 8, the initial photoresist layer 8 is removed by the photoresist removing solution, and then the final photoresist layer 10 is formed again and opened for the subsequent electroplating process of the metal bump. Here, the size of the opening of the final photoresist layer 10 is consistent with the size of the formed metal bump, so as to limit the forming size of the metal bump. Here, exposure and development are performed through the same mask as in step 102, so that openings are formed in the final photoresist layer 10 at the pads 4 corresponding to all the formed metal bumps, so as to allow metal bumps with different sizes to be plated.

Step 210: and electroplating at the opening of the final photoresist layer 10 to form a preliminary metal bump.

This step is similar to step 203, except that the small-sized metal bumps are not plated directly on the plating seed layer 7, but on the formed metal pads 9, while the large-sized metal bumps are plated directly on the plating seed layer 7, in order to make the height of the metal bumps after reflow the same.

Step 211: the final photoresist layer 10 and the plating seed layer 7 are removed.

Finally, the photoresist layer 10 is removed by dissolving and removing photoresist through a photoresist removing solution, wherein macromolecules and micromolecules can be dissolved in the photoresist removing solution, and then the product wafer electroplated with the metal bump is refluxed to obtain the formed metal bump with the size. In order to make the metal bumps on the product wafer independent and connected to the chip 1, the plating seed layer 7 needs to be removed to avoid short circuit between the metal bumps. And the removing process of the plating seed layer 7 may be performed by etching with an etching solution.

Step 212: and reflowing the product wafer to form a molded metal bump.

Although the sizes of the formed metal bumps are not consistent after reflow, the heights of the formed metal bumps with small sizes are consistent with those of the formed metal bumps with large sizes under the action of the metal cushion blocks 9, so that the uniformity of the heights of the plated metal bumps is improved.

The method of embodiments 2-5 can also be used in this embodiment to obtain the final packaged wafer.

The difference between this embodiment and embodiment 6 is that the sizes of the metal bumps are at least three, and the method for acquiring the height difference information includes the following steps:

step 2051: and sorting the forming metal bumps with different sizes from large to small to form a forming metal bump sequence.

The forming metal bump sequence is an arrangement sequence of the programmed metal bumps after being sorted from large to small in size. And finally, simulating the metal bumps with at least three sizes in the finally-formed product wafer in advance in the design process, wherein the simulation process is consistent with the steps 101-104, finally forming the formed metal bumps with different sizes, the heights of the formed metal bumps are different, for the convenience of identification, all the formed metal bumps with different sizes are classified, the formed metal bumps with the same size are defined as one type, and then the formed metal bumps are numbered from large to small, and the smaller the number is, the larger the size is.

Step 2052: calculating the target height difference between the formed metal bumps in the formed metal bump sequence and the target metal bumps one by one to form a target height difference sequence;

Step 2053: an average between the target height differences in the sequence of target height differences is calculated to form target height difference information.

The calculation mode is that a plurality of height difference values are added, and then the average value is taken to define the height difference information, so that the advantage is that the process of the middle pad metal cushion block 9 is only once, although the height difference is still existed, the height difference is reduced as much as possible, and the height difference is basically in a positive and negative range, thereby reducing the probability of false welding in the welding process.

In another embodiment, the method for acquiring height difference information includes the following steps:

step 2054: and calculating adjacent height difference information according to adjacent molded metal bumps in the molded metal bump sequence to form an adjacent height difference sequence.

Step 2055: and sequentially executing a photoresist layer forming step and a metal cushion block forming step according to the current formed metal lug in the formed metal lug sequence and the adjacent height difference information in the adjacent height difference sequence corresponding to the current formed metal lug.

Wherein the step of forming the photoresist layer comprises:

step 20551: and gluing, exposing and developing the electroplating seed layer to form a photoresist layer, wherein the photoresist layer is provided with an opening to expose a bonding pad corresponding to the formed metal bump behind the current formed metal bump in the formed metal bump sequence.

The photoresist layer is formed after the processes of gluing, exposing and developing. The difference from the final photoresist layer 10 is that the openings on the final photoresist layer expose the bonding pads corresponding to the formed metal bumps after the formed metal bumps in the formed metal bump sequence. As with the final photoresist layer 10, it is not required to be cured after formation to facilitate subsequent removal. The electroplating seed layer 7 is coated with glue, and then exposure and development are carried out through a new mask plate, only openings corresponding to the bonding pads 4 of the forming metal bumps behind the current forming metal bumps are arranged on the mask plate, and the openings corresponding to the forming metal bumps behind the current forming metal bumps and in front of the sequence are covered, so that openings are formed in the positions, corresponding to the bonding pads 4 of the metal bumps with small sizes, of the light resistance layer after the light resistance layer passes through the developing solution, and therefore adjacent height difference information in an adjacent height difference sequence can be conveniently compensated in the follow-up process.

Wherein, the metal cushion block molding step includes:

step 20552: and electroplating at the opening of the photoresist layer to form a corresponding metal cushion block 9 according to the adjacent height difference information corresponding to the current forming metal bump and the current forming metal image.

Step 2056: and repeating the photoresist layer forming step and the metal cushion block forming step in sequence according to the formed metal bumps in the formed metal bump sequence and the adjacent height difference information in the adjacent height difference sequence until the final photoresist layer 10 is formed.

In another embodiment, the photoresist layer forming step includes:

step 20553: and coating glue, exposing and developing on the electroplating seed layer 7 to form a photoresist layer, wherein an opening is formed in the photoresist layer, and only the bonding pad 4 corresponding to the currently-formed metal bump is exposed through the opening.

Similarly, this embodiment is also performed on the chip 1 having metal bumps of three or more sizes. But the difference is that only the opening of the current forming metal bump corresponding to the pad 4 is opened on the photoresist layer, so that the electroplating can be directly performed according to the corresponding height difference in the target height difference sequence.

Step 20554: and electroplating at the opening of the photoresist layer to form a current metal cushion block, wherein the height of the current metal cushion block 9 is greater than the height difference corresponding to the current metal cushion block in the target height difference sequence.

In another embodiment, the step of forming the photoresist layer may further include the steps of:

step 20555: and forming a next corresponding photoresist layer on the photoresist layer directly through gluing, exposing and developing, wherein the height of the next corresponding photoresist layer is greater than the adjacent height difference information in the corresponding adjacent height difference sequence.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims

1. A method for improving the uniformity of the height of an electroplated bump is applied to a wafer with the same chip (1), and is characterized by comprising the following steps:

acquiring height difference information among the molded metal lugs with different sizes, defining the molded metal lug with the highest height as a target metal lug (3), and defining the rest molded metal lugs as distinguishing metal lugs (2);

sputtering and forming a plating seed layer (7) on the product wafer;

coating glue, exposing and developing on the electroplating seed layer (7) to form an initial photoresist layer (8), wherein an opening is formed in the initial photoresist layer (8) to expose a bonding pad (4) corresponding to the distinguishing metal bump (2);

electroplating at the opening of the initial photoresist layer (8) to form a metal cushion block (9), wherein the height of the metal cushion block (9) is equal to the height value corresponding to the height difference information;

removing the initial photoresist layer (8), coating glue, exposing and developing on the electroplating seed layer (7) again to form a final photoresist layer (10), wherein an opening is formed in the final photoresist layer (10) to expose the bonding pad (4) corresponding to all the formed metal bumps;

electroplating at the opening of the final photoresist layer (10) to form a preliminary metal bump;

removing the final photoresist layer (10) and the electroplating seed layer (7);

and reflowing the product wafer to form a molded metal bump.

2. The method as claimed in claim 1, wherein the step of obtaining the height difference information of the formed metal bump comprises:

sputtering and forming a plating seed layer (7) on the test wafer;

coating glue, exposing and developing on the electroplating seed layer (7) to form a final light resistance layer (10), wherein an opening is formed in the final light resistance layer (10) to expose the bonding pad (4) corresponding to all the formed metal bumps;

removing the final photoresist layer (10) and then reflowing the test wafer to form a formed metal bump;

3. The method of claim 1, wherein the step of increasing the uniformity of the height of the plated bumps comprises: the openings of the initial light resistance layer (8) correspond to the distinguishing metal bumps (2) one by one, the sizes of the openings are larger than the sizes of the distinguishing metal bumps (2), and the sizes of the openings of the final light resistance layer (10) are equal to the sizes of all the corresponding metal bumps.

4. The method of claim 2, wherein the step of increasing the uniformity of the height of the plated bumps comprises: before a plating seed layer (7) is formed on a test wafer or a product wafer by sputtering, the method comprises the following steps: forming a PI protective layer (6) through gluing, exposing, developing and curing, wherein an opening is formed in the PI protective layer (6) to expose the bonding pads (4) corresponding to all the formed metal bumps.

5. The method of claim 1, wherein the step of increasing the uniformity of the height of the plated bumps comprises: if there are metal bumps with at least three sizes, the method for acquiring the height difference information comprises the following steps:

calculating the target height difference between the formed metal bumps in the formed metal bump sequence and the target metal bump (3) one by one to form a target height difference sequence;

6. The method as claimed in claim 5, wherein the step of increasing the uniformity of the height of the plated bump comprises: if there are metal bumps with at least three sizes, the steps of forming a metal pad (9) at the opening of the initial photoresist layer (8) by electroplating, removing the initial photoresist layer (8), coating glue, exposing and developing on the electroplating seed layer (7) again to form a final photoresist layer (10), wherein the steps of forming openings on the final photoresist layer (10) to expose the bonding pads (4) corresponding to all the formed metal bumps further include the following steps:

calculating adjacent height difference information according to adjacent molded metal bumps in the molded metal bump sequence to form an adjacent height difference sequence;

sequentially executing a photoresist layer forming step and a metal cushion block (9) forming step according to a current formed metal lug in the formed metal lug sequence and adjacent height difference information in an adjacent height difference sequence corresponding to the current formed metal lug;

wherein the step of forming the photoresist layer comprises:

coating glue, exposing and developing on the electroplating seed layer (7) to form a light resistance layer, wherein an opening is formed in the light resistance layer to expose a bonding pad (4) corresponding to a molded metal bump behind a current molded metal bump in the molded metal bump sequence;

wherein, the metal cushion block (9) forming step comprises:

electroplating at the opening of the photoresist layer to form a corresponding metal cushion block (9) according to the adjacent height difference information corresponding to the current forming metal bump and the current forming metal image;

and sequentially and repeatedly executing the photoresist layer forming step and the metal cushion block (9) forming step according to the formed metal bumps in the formed metal bump sequence and the adjacent height difference information in the adjacent height difference sequence until a final photoresist layer (10) is formed.

7. The method as claimed in claim 6, wherein the step of increasing the uniformity of the height of the plated bump comprises: the opening size of the light resistance layer is gradually reduced at the position corresponding to the metal cushion block (9), and finally the opening size of the light resistance layer (10) is equal to the sizes of all the corresponding metal bumps.

8. The method of claim 7, wherein the step of increasing the uniformity of the height of the plated bumps comprises: the step of sequentially performing the photoresist layer forming further comprises:

9. A method for improving the uniformity of the height of an electroplated bump is applied to a wafer with at least two chips (1), and is characterized by comprising the following steps:

acquiring height difference information among the forming metal bumps on different chips (1), defining the forming metal bump with the highest height as a target metal bump (3), and defining the rest forming metal bumps as distinguishing metal bumps (2);

sputtering and forming a plating seed layer (7) on the product wafer;

electroplating at an opening of the initial photoresist layer (8) to form a metal cushion block (9), wherein the height of the metal cushion block (9) is equal to a height value corresponding to the height difference information;

and reflowing the product wafer to form a molded metal bump.

10. A wafer, comprising:

the chip (1) is used as a bearing base and is provided with a bonding pad (4) of a metal bump in an electroplating way;

the PI protective layer (6) is arranged on the chip (1) and is provided with an opening so as to expose the bonding pads (4) corresponding to all the molded metal bumps;

the electroplating seed layer (7) is arranged at the openings of the PI protective layer (6) and is electrically connected with the bonding pad (4) on the chip (1);

the metal cushion block (9) is arranged on the opening of the PI protective layer (6) and is electrically connected with the electroplating seed layer (7) connected with the distinguishing metal bump (2) so as to make up height difference information;

the target metal bump (3) comprises a target copper pillar (31) and a target tin cap (32), the target copper pillar (31) is arranged on the electroplating seed layer (7) and is positioned at the opening of the PI protective layer (6), and the target tin cap (32) is arranged on one side, away from the electroplating seed layer (7), of the target copper pillar (31);

distinguish metal lug (2), including distinguishing copper post (21) and distinguishing tin cap (22), distinguish one side that metal cushion (9) kept away from electroplating seed layer (7) is located to copper post (21), distinguish tin cap (22) and set up in distinguishing one side that electroplating seed layer (7) was kept away from to copper post (21).