阅读说明：本技术 一种高可靠性晶圆级封装的声表滤波器结构及其制备方法 (High-reliability wafer-level packaged acoustic surface filter structure and preparation method thereof ) 是由 金中 彭雄 吴良臣 于 2021-08-27 设计创作，主要内容包括：本发明公开了一种高可靠性晶圆级封装的声表滤波器结构及其制备方法,其中声表滤波器结构为,在晶圆工作表面粘贴有PI底膜,PI底膜形成有腔体和通孔,通孔内填充有金属以形成电极通道；在腔体上粘贴有PI顶膜将腔体开口封闭。在PI底膜与晶圆外周的结合界面处以及PI底膜和PI顶膜外周的结合界面处设有保护层,该保护层将对应位置的结合界面包覆以与外界隔离。制备时,将底膜与晶圆外周的结合界面以及底膜和顶膜外周的结合界面作为电镀区域进行电镀并与其他电镀区域隔离,通过电镀即得到保护层。本发明可有效避免水汽通过PI膜结合界面侵入器件内,提高器件在可靠性方面的表现,特别适用于高可靠性应用场景。(The invention discloses a high-reliability wafer-level packaged surface acoustic wave filter structure and a preparation method thereof, wherein the surface acoustic wave filter structure is characterized in that a PI bottom film is adhered to the working surface of a wafer, a cavity and a through hole are formed in the PI bottom film, and a metal is filled in the through hole to form an electrode channel; and a PI top film is adhered on the cavity to seal the opening of the cavity. And protective layers are arranged at the combination interface of the PI bottom film and the periphery of the wafer and the combination interface of the PI bottom film and the periphery of the PI top film, and the protective layers coat the combination interfaces at corresponding positions to be isolated from the outside. During preparation, a bonding interface between the bottom film and the periphery of the wafer and a bonding interface between the bottom film and the periphery of the top film are used as electroplating areas to be electroplated and isolated from other electroplating areas, and the protective layer is obtained through electroplating. The invention can effectively prevent water vapor from invading into the device through the PI film combined interface, improves the performance of the device in the aspect of reliability, and is particularly suitable for high-reliability application scenes.)

1. A high-reliability wafer-level packaged surface acoustic wave filter structure comprises a wafer, wherein a PI bottom film is adhered to the working surface of the wafer, a cavity and a through hole are formed in a hollow part of the PI bottom film, and the rest parts of the PI bottom film form a wall structure; the through hole is filled with metal to form an electrode channel; a bonding pad is formed at the upper end of the electrode channel, and a welding ball is arranged at the bonding pad; a PI top film is adhered to the cavity opening, the periphery of the PI top film is lapped on a wall structure, and the PI top film completely seals the cavity opening; the method is characterized in that: protective layers are arranged at the combination interface of the peripheries of the PI bottom film and the wafer and at the combination interface of the peripheries of the PI bottom film and the PI top film, and the protective layers coat the combination interfaces at corresponding positions to be isolated from the outside.

2. The highly reliable wafer level packaged acoustic surface filter structure of claim 1, wherein: the protective layer at the joint interface of the PI bottom film and the periphery of the wafer and the protective layer at the joint interface of the PI bottom film and the periphery of the PI top film are connected into a whole to form a fence with a certain height.

3. The highly reliable wafer level packaged acoustic surface filter structure of claim 2, wherein: the enclosure is an electroplating enclosure formed by electroplating, and the electroplating enclosure is insulated from the pattern layer and the solder balls on the top die.

4. A preparation method of a high-reliability wafer-level packaged acoustic surface filter is characterized by comprising the following steps: the method comprises the following steps:

1) adhering a layer of bottom film on the working surface of the wafer;

2) removing the unnecessary film layer by a photoetching process, forming a through hole and a cavity at the photoetching position, and forming a wall structure by the reserved bottom film after photoetching;

3) a layer of top film is adhered on the wall structure, and the top film seals the through hole and the cavity formed by the last step of photoetching;

4) removing the top mold corresponding to the through hole through a photoetching process, and reserving the top mold above the cavity;

5) forming a seed layer on the surface of the product obtained in the step 4) through magnetron sputtering;

6) protecting the seed layer of the part which does not need to be electroplated by photoresist, and only exposing the seed layer of the part which needs to be electroplated; the part needing electroplating comprises a combination interface of the bottom film and the periphery of the wafer and a combination interface of the bottom film and the periphery of the top film;

7) forming a conducting structure in the through hole by electroplating and forming a required plating layer structure in other electroplating areas;

8) removing the photoresist in the step 6);

9) removing the seed layer protected by the photoresist in the step 6) by corrosion; during corrosion, protecting the electroplating part obtained in the step 7) by photoresist, and only exposing a region needing corrosion; the electroplating part protected by the photoresist comprises an electroplating part at a combination interface of the bottom film and the periphery of the wafer and an electroplating part at a combination interface of the bottom film and the periphery of the top film; after the etching is finished, removing the corresponding photoresist;

10) and brushing solder paste on the through holes to form solder balls.

5. The method for manufacturing the acoustic surface filter of the high-reliability wafer level package according to claim 4, wherein: and 7) in the step, a plating layer obtained from the bonding interface of the bottom film and the periphery of the wafer is connected with a plating layer obtained from the bonding interface of the bottom film and the periphery of the top film into a whole to form an electroplating enclosure with a certain height.

6. The method for manufacturing the acoustic surface filter of the high-reliability wafer level package according to claim 5, wherein: the seed layer part protected by the photoresist in the step 6) also comprises a seed layer of an isolation area for isolating the electroplating enclosure to be formed from the pattern layer and the solder ball on the top mold to be formed; and 4) completely corroding the seed layer in the isolation area in the step 9), thereby realizing the isolation of the electroplating enclosure from the pattern layer and the solder balls on the top die.

7. The method for manufacturing the acoustic surface filter of the high-reliability wafer level package according to claim 4, wherein: the bottom film and the top film are both PI films.

Technical Field

The invention relates to a surface acoustic wave filter packaging technology, in particular to a high-reliability wafer-level packaged surface acoustic wave filter structure and a preparation method thereof, and belongs to the technical field of surface acoustic wave filters.

Background

The surface acoustic wave filter wafer level packaging utilizes a PI film to form a protection cavity through a photoetching method to protect the surface acoustic wave filter. The specific packaging steps are as follows: 1. a layer of PI bottom film 2 is adhered to the working surface of the wafer 1; 2. removing the unnecessary film layer by a photoetching process, forming a through hole 3 and a cavity 4 at the photoetching position, and forming a wall structure by the PI bottom film left after photoetching; 3. a layer of PI top film 5 is adhered on the wall structure, and the through hole formed by cutting in the previous step and the cavity 4 are sealed by the top film; 4. removing the top mold corresponding to the through hole through a photoetching process, and leaving the top mold 5 including the upper part of the cavity; 5. forming a seed layer on the surface of the product obtained in the step 4 through magnetron sputtering; 6. protecting the seed layer of the part which does not need to be electroplated by photoresist, and only exposing the seed layer of the part which needs to be electroplated; 7. forming a conducting structure in the through hole by electroplating and forming a required pattern structure 6 in other electroplating areas; 8. removing the photoresist in the step 6; 9. removing the seed layer protected by the photoresist in the step 6 by corrosion; during corrosion, protecting the electroplating part obtained in the step 7 by photoresist, and only exposing a region needing corrosion; after the etching is finished, removing the corresponding photoresist; 10. and brushing solder paste on the through holes 3 to form solder balls 7. Fig. 1 is a schematic diagram of a prior art packaged acoustic surface filter structure.

According to the process, the construction of the cavity is completed by adopting a mode of two layers of PI films in WLP packaging of the traditional surface acoustic wave filter, and the two films are bonded by adopting a film sticking machine. Due to inherent influences such as warping of the wafer during film pasting and the characteristics of the PI film material, the interface layer (including the interface layer between the bottom film and the wafer and the interface layer between the top film and the bottom film, namely the position indicated by an arrow in FIG. 1) at the film pasting position is relatively weak, a certain proportion of delamination phenomenon occurs, attacks of various external conditions such as water vapor cannot be resisted, and the use scene with high reliability requirements cannot be met. Once moisture ingress, there is a risk of failure in high reliability application scenarios.

Disclosure of Invention

Aiming at the risk of water vapor invasion in a film pasting interface after the surface acoustic wave filter wafer level packaging in the prior art, the invention aims to provide a high-reliability wafer level packaged surface acoustic wave filter structure and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a high-reliability wafer-level packaged surface acoustic wave filter structure comprises a wafer, wherein a PI bottom film is adhered to the working surface of the wafer, a cavity and a through hole are formed in a hollow part of the PI bottom film, and the rest parts of the PI bottom film form a wall structure; the through hole is filled with metal to form an electrode channel; a bonding pad is formed at the upper end of the electrode channel, and a welding ball is arranged at the bonding pad; a PI top film is adhered to the cavity opening, the periphery of the PI top film is lapped on a wall structure, and the PI top film completely seals the cavity opening; the method is characterized in that: protective layers are arranged at the combination interface of the peripheries of the PI bottom film and the wafer and at the combination interface of the peripheries of the PI bottom film and the PI top film, and the protective layers coat the combination interfaces at corresponding positions to be isolated from the outside.

The protective layer at the joint interface of the PI bottom film and the periphery of the wafer and the protective layer at the joint interface of the PI bottom film and the periphery of the PI top film are connected into a whole to form a fence with a certain height.

The enclosure is an electroplating enclosure formed by electroplating, and the electroplating enclosure is insulated from the pattern layer and the solder balls on the top die.

The invention discloses a preparation method of a high-reliability wafer-level packaged acoustic surface filter, which comprises the following steps:

1) adhering a layer of bottom film on the working surface of the wafer;

2) removing the unnecessary film layer by a photoetching process, forming a through hole and a cavity at the photoetching position, and forming a wall structure by the reserved bottom film after photoetching;

3) a layer of top film is adhered on the wall structure, and the top film seals the through hole and the cavity formed by the last step of photoetching;

4) removing the top mold corresponding to the through hole through a photoetching process, and reserving the top mold above the cavity;

5) forming a seed layer on the surface of the product obtained in the step 4) through magnetron sputtering;

6) protecting the seed layer of the part which does not need to be electroplated by photoresist, and only exposing the seed layer of the part which needs to be electroplated; the part needing electroplating comprises a combination interface of the bottom film and the periphery of the wafer and a combination interface of the bottom film and the periphery of the top film;

7) forming a conducting structure in the through hole by electroplating and forming a required plating layer structure in other electroplating areas;

8) removing the photoresist in the step 6);

9) removing the seed layer protected by the photoresist in the step 6) by corrosion; during corrosion, protecting the electroplating part obtained in the step 7) by photoresist, and only exposing a region needing corrosion; the electroplating part protected by the photoresist comprises an electroplating part at a combination interface of the bottom film and the periphery of the wafer and an electroplating part at a combination interface of the bottom film and the periphery of the top film; after the etching is finished, removing the corresponding photoresist;

10) and brushing solder paste on the through holes to form solder balls.

Preferably, in the step 7), the plating layer obtained at the bonding interface between the bottom film and the outer periphery of the wafer and the plating layer obtained at the bonding interface between the bottom film and the outer periphery of the top film are connected into a whole to form a plating enclosure with a certain height.

Further, the seed layer part protected by the photoresist in the step 6) also comprises a seed layer of an isolation area for isolating the electroplating enclosure to be formed from the pattern layer and the solder ball on the top mold to be formed; and 4) completely corroding the seed layer in the isolation area in the step 9), thereby realizing the isolation of the electroplating enclosure from the pattern layer and the solder balls on the top die.

The bottom film and the top film are both PI films.

Compared with the prior art, the invention has the following beneficial effects:

1. the protective layers are arranged at the joint interface of the periphery of the bottom film and the wafer and the joint interface of the periphery of the bottom film and the periphery of the top film, the protective layers coat the joint interfaces at the corresponding positions to be isolated from the outside, and prevent water vapor or other substances from contacting with the side wall at the film pasting interface, so that the water vapor and the like are prevented from entering, the reliability of a sound meter filter WLP product is greatly improved, and the sound meter filter WLP product can be easily coped with even if the sound meter filter WLP product is used in a high-reliability application scene.

2. The protective layer is formed through an electroplating process, and because the surface acoustic wave filter needs to be electroplated in the manufacturing process, the protective layer is obtained along the strip while the device needs to be electroplated, no additional process is needed, and the protective layer is simple to obtain and low in cost. When the position of the bonding pad is electroplated and thickened, the side wall is also electroplated and thickened, so that the side wall of the device is coated by the metal coating, and the metal coating naturally covers the original two layers of PI films and the combination part between the PI films and the wafer, thereby achieving the effect of protection and isolation.

3. The protective layer obtained by the electroplating process has strong bonding property with a device and good sealing property on a bonding interface, and can realize 100% protection on the bonding interface.

Drawings

Fig. 1 is a schematic diagram of a prior art packaged acoustic surface filter structure. The arrows in the figure indicate the PI film bonding interface where moisture can easily penetrate.

Fig. 2 is a schematic diagram of the structure of the packaged acoustic surface filter according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The invention relates to a high-reliability wafer-level packaged surface acoustic wave filter structure, which comprises a wafer 1, wherein a PI bottom film 2 is adhered to the working surface of the wafer 1, a cavity 4 and a through hole 3 are formed at the hollow part of the PI bottom film 2, and the rest parts of the PI bottom film form a wall structure; the through hole 3 is filled with metal to form an electrode channel 8; the upper end of the electrode channel 8 forms a pad and a solder ball is arranged at the pad, and the solder ball is a solder ball 7. A PI top film 5 is adhered to the opening of the cavity 4, the periphery of the PI top film is lapped on a wall structure, and the opening of the cavity 4 is completely sealed by the PI top film 5; protective layers 9 are arranged at the combination interface of the peripheries of the PI bottom film 2 and the wafer 1 and the combination interface of the peripheries of the PI bottom film 2 and the PI top film 5, and the protective layers 9 coat the combination interfaces at corresponding positions to be isolated from the outside.

The protective layer is arranged to coat the bonding interface at the corresponding position so as to isolate the bonding interface from the outside, and water vapor or other substances are prevented from contacting with the side wall at the film pasting interface, so that the water vapor and the like are prevented from entering, and the reliability of a WLP product of the acoustic surface filter is greatly improved.

The protective layer at the joint interface of the PI bottom film and the periphery of the wafer and the protective layer at the joint interface of the PI bottom film and the periphery of the PI top film are connected into a whole to form a fence with a certain height. The two protective layers are connected into a whole, so that the processing is convenient, and the protective effect on the bonding interface is enhanced.

The enclosure is an electroplating enclosure formed by electroplating, and the electroplating enclosure is insulated from the pattern layer and the solder balls on the top die. The enclosure formed by electroplating has strong binding force with the substrate and better fitting property, and is more beneficial to protecting the binding interface.

A preparation method of a high-reliability wafer-level packaged acoustic surface filter comprises the following steps:

1) a layer of bottom film 2 is stuck on the working surface of the wafer 1;

2) removing the unnecessary film layer by photoetching process, forming a through hole 3 and a cavity 4 at the photoetching position, and forming a wall structure by the reserved bottom film after photoetching;

3) a layer of top film 5 is adhered on the wall structure, and the through hole formed by the last step of photoetching and the cavity 4 are sealed by the top film;

4) removing the top mold corresponding to the through hole by a photoetching process, and leaving the top mold 5 above the cavity 4;

5) forming a seed layer on the surface of the product obtained in the step 4) through magnetron sputtering;

6) protecting the seed layer of the part which does not need to be electroplated by photoresist, and only exposing the seed layer of the part which needs to be electroplated; the part needing electroplating comprises a combination interface of the bottom film and the periphery of the wafer and a combination interface of the bottom film and the periphery of the top film;

7) forming a conducting structure in the through hole by electroplating and forming a required plating layer structure in other electroplating areas; the conducting structure forms the electrode channel 8 and the plating structure forms the desired circuit pattern structure 6.

8) Removing the photoresist in the step 6);

9) removing the seed layer protected by the photoresist in the step 6) by corrosion; during corrosion, protecting the electroplating part obtained in the step 7) by photoresist, and only exposing a region needing corrosion; the electroplating part protected by the photoresist comprises an electroplating part at a combination interface of the bottom film and the periphery of the wafer and an electroplating part at a combination interface of the bottom film and the periphery of the top film; after the etching is finished, removing the corresponding photoresist;

10) and brushing solder paste on the through holes to form solder balls 7.

Fig. 2 is a schematic diagram of the structure of the packaged acoustic surface filter according to the present invention.

And 7) in the step, a plating layer obtained from the bonding interface of the bottom film and the periphery of the wafer is connected with a plating layer obtained from the bonding interface of the bottom film and the periphery of the top film into a whole to form an electroplating enclosure with a certain height.

The seed layer part protected by the photoresist in the step 6) also comprises a seed layer of an isolation area for isolating the electroplating enclosure to be formed from the pattern layer and the solder ball on the top mold to be formed; and 4) completely corroding the seed layer in the isolation area in the step 9), thereby realizing the isolation of the electroplating enclosure from the pattern layer and the solder balls on the top die. The isolation region is designated by reference numeral 10 in fig. 2. Although the protective layer is also formed simultaneously by the plating process, the protective layer and the original plating structure of the device are spaced apart from each other, and the reliability of the original plating structure of the device is not affected.

In the wafer-level packaging of the acoustic surface filter, the seed layer is established by magnetron sputtering, then photoresist is used for protection, the side wall and the through hole are contacted with electroplating solution, a layer of metal grows on the side wall while filling hole copper, the side wall of the acoustic surface filter packaged by the film is covered by the layer of metal, even if a gap exists between films, a metal isolation layer can be formed to prevent substances such as water vapor from invading into the cavity of the filter along the interface of the film, and the reliability of the wafer-level acoustic surface filter packaged by the film is greatly improved.

The protective layer is formed through an electroplating process, and because the surface acoustic wave filter needs to be electroplated in the manufacturing process, the protective layer is obtained along the strip while the device needs to be electroplated, no additional process is needed, and the protective layer is simple to obtain and low in cost. When the welding disc is electroplated and thickened, the side wall is also electroplated and thickened, so that the side wall of the device is coated by the metal coating, and the metal coating naturally covers the original two film layers and the joint part between the bottom film and the wafer, thereby achieving the effect of protection and isolation.

The above examples of the present invention are merely illustrative of the present invention and are not intended to limit the embodiments of the present invention. Variations and modifications in other variations will occur to those skilled in the art upon reading the foregoing description. Not all embodiments are exhaustive. All obvious changes and modifications of the present invention are within the scope of the present invention.