阅读说明：本技术 一种mems环行器的封装方法 (Packaging method of MEMS circulator ) 是由 王伟强 汪蔚 翟晓飞 周嘉 侯凯强 于 2019-10-29 设计创作，主要内容包括：本发明提供了一种MEMS环行器的封装方法,属于环行器封装技术领域,包括以下步骤：在晶圆的正面制备金属电路层,在晶圆的背面制备金属焊接层,获得成一体结构的多个芯片单元；在晶圆的背面制备焊料层；在背面向上的晶圆上每个芯片单元对应的位置放置金属载体,并将金属载体和晶圆背面焊接为一体；在正面向上的晶圆上每个芯片单元对应的位置点胶,将永磁体贴装在胶层表面,并将贴装了永磁体的晶圆上的胶层进行固化；将焊接了金属载体和贴装了永磁体的晶圆进行切割,获得独立的MEMS环行器。本发明提供的一种MEMS环行器的封装方法获得的MEMS环行器精度高、体积小、一致性好,并能够适用于批量封装制造。(The invention provides a packaging method of an MEMS circulator, belonging to the technical field of circulator packaging and comprising the following steps: preparing a metal circuit layer on the front side of the wafer, and preparing a metal welding layer on the back side of the wafer to obtain a plurality of chip units in an integrated structure; preparing a solder layer on the back of the wafer; placing a metal carrier at a position corresponding to each chip unit on the wafer with the upward back surface, and welding the metal carrier and the back surface of the wafer into a whole; dispensing glue at the position corresponding to each chip unit on the wafer with the front surface upward, attaching the permanent magnet on the surface of the glue layer, and curing the glue layer on the wafer attached with the permanent magnet; and cutting the wafer welded with the metal carrier and pasted with the permanent magnet to obtain the independent MEMS circulator. The MEMS circulator obtained by the packaging method of the MEMS circulator provided by the invention has the advantages of high precision, small volume and good consistency, and can be suitable for batch packaging and manufacturing.)

1. A packaging method of a MEMS circulator is characterized by comprising the following steps:

preparing a metal circuit layer on the front side of a wafer, and preparing a metal welding layer on the back side of the wafer to obtain a plurality of chip units in an integrated structure;

preparing a solder layer on the back side of the wafer;

placing a metal carrier at a position corresponding to each chip unit on the wafer with the back surface upward, and welding the metal carrier and the back surface of the wafer into a whole;

dispensing glue at a position corresponding to each chip unit on the wafer with the front surface facing upwards, attaching a permanent magnet on the surface of a glue layer, and curing the glue layer on the wafer attached with the permanent magnet;

and cutting the wafer welded with the metal carrier and pasted with the permanent magnet to obtain the independent MEMS circulator.

2. The method for packaging a MEMS circulator of claim 1, wherein before placing a metal carrier at a position corresponding to each of the chip units on the wafer with the back surface facing upward, the method further comprises:

pre-cutting the back surface of the wafer along a first scribing mark pre-manufactured on the back surface of the wafer; the precut depth is 50-100 μm.

3. The method for packaging a MEMS circulator of claim 2, wherein the dicing the wafer on which the metal carrier is bonded and the permanent magnet is mounted comprises:

re-cutting the front surface of the wafer along a second scribing mark pre-manufactured on the front surface of the wafer; wherein the re-cut position corresponding to the second dicing mark is identical to the pre-cut position corresponding to the first dicing mark.

4. The method of claim 3, wherein: the re-cutting depth is the difference value between the thickness of the wafer and the pre-cutting depth plus a preset correction value;

wherein the preset correction value ranges from 40 μm to 60 μm.

5. The method of claim 3, wherein: the width of the first scribing mark is larger than that of the cutting blade in precutting, and the width of the second scribing mark is larger than that of the cutting blade in re-cutting.

6. The method of packaging a MEMS circulator of claim 1, wherein: the solder layer comprises a plurality of solder areas distributed in an array mode, and each solder area is arranged corresponding to the chip unit on the front surface of the wafer; the area of each solder region is smaller than that of the corresponding chip unit, and each solder region is positioned right below the corresponding chip unit.

7. The method as claimed in claim 1, wherein the dispensing at the position corresponding to each of the chip units on the wafer with the front surface facing upward comprises:

and dispensing glue in a glue dispensing identification pattern preset on each chip unit on the wafer with the front surface upward, wherein the roughness of the glue dispensing identification pattern is less than 1 mu m.

8. The method of packaging a MEMS circulator of claim 1, wherein: the metal carrier is kovar alloy or molybdenum-copper alloy, and a metal coating is manufactured on the welding surface of the metal carrier.

9. The method of packaging a MEMS circulator of claim 8, wherein: the metal welding layer and the metal coating are both Ni-Au coatings; the solder layer is Au-Sn solder.

10. The method of packaging a MEMS circulator of claim 1, wherein said soldering the metal carrier and the back side of the wafer together includes:

placing the wafer with the metal carrier on the back side in a graphite clamp;

placing the graphite clamp with the wafer and the metal carrier in a vacuum sintering furnace for welding, wherein the gas in the welding process comprises the following steps: formic acid.

Technical Field

The invention belongs to the technical field of circulator packaging, and particularly relates to a packaging method of an MEMS circulator.

Background

With the development of modern electronic technology, communication transceiving systems tend to be miniaturized, and a pressing demand for miniaturization of circulator products at the front end of radio frequency is provided. Compared with the traditional circulator product, the MEMS (Micro-Electro-Mechanical System) circulator realizes transmission and reverse isolation of electromagnetic waves in the circulator according to a certain annular direction by means of the magnetic material in the circulator under the combined action of an external microwave field and a direct-current steady magnetic field, has the advantages of small volume, high precision, high power, good reliability and the like, and has better application prospect in the fields of 5G communication and the like.

At present, the packaging of the MEMS circulator is mainly a chip-scale packaging manner, and a chip structure of the MEMS circulator is processed on a silicon wafer by an MEMS processing Process (micro fabrication Process) such as photolithography, development, etching, wafer bonding, and the like, then the silicon wafer is cut into an independent MEMS circulator by a scribing Process, then the back surface of the MEMS circulator and the surface of a metal carrier are welded into a whole by melting eutectic of a solder piece at a high temperature, and finally a permanent magnet is dispensed and bonded on the front surface of the MEMS circulator, and the MEMS circulator is obtained after the glue is cured.

In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art: the welding process of the back surface of the MEMS circulator and the surface of the carrier is easy to generate dislocation of the welding flux sheet, so that the welding flux overflows or the defect of a cavity is caused; the chip has low alignment operation efficiency and high difficulty, and the front-bonded permanent magnet has poor alignment precision and low efficiency, thereby seriously restricting the production efficiency.

Disclosure of Invention

The invention aims to provide a packaging method of an MEMS circulator, and aims to solve the problems of high packaging difficulty and low efficiency of the MEMS circulator in the prior art.

In order to achieve the purpose, the invention adopts the technical scheme that: a packaging method of a MEMS circulator is provided, which comprises the following steps:

preparing a metal circuit layer on the front side of the wafer, and preparing a metal welding layer on the back side of the wafer to obtain a plurality of chip units in an integrated structure;

preparing a solder layer on the back of the wafer;

placing a metal carrier at a position corresponding to each chip unit on the wafer with the upward back surface, and welding the metal carrier and the back surface of the wafer into a whole;

dispensing glue at the position corresponding to each chip unit on the wafer with the front surface upward, attaching a permanent magnet on the surface of the glue layer, and curing the wafer attached with the permanent magnet;

and cutting the wafer welded with the metal carrier and pasted with the permanent magnet to obtain the independent MEMS circulator.

As another embodiment of the present application, before placing the metal carrier at a position corresponding to each chip unit on the wafer with the back side facing upward, the method further includes: pre-cutting the back surface of the wafer along a first scribing mark pre-manufactured on the back surface of the wafer; the precut depth is 50-100 μm.

As another embodiment of the present application, the dicing the wafer to which the metal carrier and the permanent magnet are bonded are soldered includes: carrying out re-cutting on the front surface of the wafer along a second scribing mark pre-manufactured on the front surface of the wafer; and the corresponding re-cutting position of the second scribing mark is consistent with the corresponding pre-cutting position of the first scribing mark.

As another embodiment of the present application, the re-cutting depth is the difference between the thickness of the wafer and the pre-cutting depth plus a preset correction value; wherein the preset correction value ranges from 40 μm to 60 μm.

As another embodiment of the present application, the width of the first scribe mark is greater than the width of the cutting blade at the time of precutting, and the width of the second scribe mark is greater than the width of the cutting blade at the time of recutting.

As another embodiment of the present application, the solder layer includes a plurality of solder regions distributed in an array, each solder region being disposed corresponding to a chip unit on the front surface of the wafer; each solder region has an area smaller than that of the corresponding chip unit, and each solder region is located directly below the corresponding chip unit.

As another embodiment of the present application, the dispensing at the position corresponding to each chip unit on the wafer with the front surface facing upward includes: and dispensing glue in a glue dispensing identification graph preset on each chip unit on the wafer with the front surface upward, wherein the roughness of the glue dispensing identification graph is less than 1 mu m.

As another embodiment of the present application, the metal carrier is a kovar alloy or a molybdenum-copper alloy, and the welding surface of the metal carrier is made with a metal coating.

As another embodiment of the present application, the metal solder layer and the metal plating layer are both Ni — Au plating layers; the solder layer is Au-Sn solder.

As another embodiment of the present application, soldering the metal carrier and the back side of the wafer together includes: placing the wafer with the metal carrier on the back surface in a graphite clamp; placing the graphite clamp with the wafer and the metal carrier in a vacuum sintering furnace, and welding, wherein gas in the welding process comprises the following steps: formic acid.

The packaging method of the MEMS circulator provided by the invention has the beneficial effects that: compared with the prior art, the packaging method of the MEMS circulator comprises the steps of manufacturing a plurality of chip units which are integrated into a whole on a wafer in advance, placing and welding a metal carrier at the position corresponding to each chip unit on the wafer with the back surface upward, dispensing and bonding a permanent magnet at the position corresponding to each chip unit on the wafer with the front surface upward, wherein the welding of the metal carrier and the bonding of the permanent magnet realize wafer-level operation, the problems that in the chip-level packaging and welding process of the prior art, due to the fact that welding solder sheets are difficult to align and are prone to misplace, welding fluxes overflow or welding cavity defects and the like are caused are solved, and the packaging quality and the packaging efficiency are improved; in addition, due to the adoption of a wafer-level bonding mode, the bonding of the permanent magnet can be ensured to be rapid and efficient, and the production efficiency is high;

after the metal carrier is welded and the permanent magnet is bonded, the wafer is cut to obtain the independent MEMS circulator, the obtained MEMS circulator is small in size, high in precision and good in consistency, is suitable for miniaturization and large-batch packaging and manufacturing, and has important significance for popularization and application of the MEMS circulator in the field of 5G communication.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a process flow diagram of a packaging method of a MEMS circulator according to an embodiment of the present invention;

fig. 2 to fig. 8 are schematic process flow diagrams of a packaging method of a MEMS circulator according to an embodiment of the present invention;

fig. 9 is an exploded view of a MEMS circulator fabricated by a method for packaging a MEMS circulator according to an embodiment of the present invention.

In the figure: 1. a wafer; 2. a chip unit; 3. a metal solder layer; 4. a solder layer; 5. pre-cut locations; 6. a metal carrier; 7. a glue layer; 8. a permanent magnet; 9. the position of the re-cut.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1 to fig. 9, a method for packaging a MEMS circulator according to the present invention will now be described. The packaging method of the MEMS circulator comprises the following steps:

step S101, referring to fig. 2, preparing a metal circuit layer on the front surface of the wafer 1, and preparing a metal welding layer 3 on the back surface of the wafer 1 to obtain a plurality of chip units 2 in an integrated structure;

step S102, referring to fig. 3, preparing a solder layer 4 on the back surface of the wafer 1;

step S103, referring to fig. 5, placing a metal carrier 6 at a position corresponding to each chip unit 2 on the wafer 1 with the upward back surface, and welding the metal carrier 6 and the back surface of the wafer 1 into a whole;

step S104, referring to fig. 6 and 7, dispensing at a position corresponding to each chip unit 2 on the wafer 1 with the front surface facing upward, attaching the permanent magnet 8 to the surface of the adhesive layer 7, and curing the adhesive layer 7 on the wafer 1 with the permanent magnet 8 attached thereto;

step S105, referring to fig. 8, the wafer 1 welded with the metal carrier 6 and attached with the permanent magnet 8 is cut to obtain an independent MEMS circulator.

The invention provides a specific description of a packaging method of an MEMS circulator, which comprises the following steps:

in this embodiment, the wafer may be a silicon wafer, or may be a wafer corresponding to other materials capable of manufacturing an MEMS circulator, which is not limited herein; in addition, a plurality of chip units 2 are arranged in a matrix.

The front side of the wafer 1 is manufactured with a metal circuit layer of an MEMS circulator by adopting photoetching, sputtering and electroplating MEMS processing technology (namely, Microsimulation Process, which is a general name of micro-structure processing technology from the bottom to the nanometer scale and from the top to the millimeter scale, and the micromachining technology for manufacturing complex three-dimensional shapes by taking photoetching, epitaxy, film deposition, oxidation, diffusion, injection, sputtering, distillation, etching, scribing, packaging and the like as basic processing steps); manufacturing a metal welding layer 3 on the back surface of the wafer 1 by adopting MEMS processing technologies such as photoetching, sputtering, electroplating and the like;

the metal welding layer 3 is provided with a solder layer 4 by MEMS processing techniques such as photoetching, electroplating and the like.

It should be noted that Wafer Level Package (WLP) uses a Wafer as a processing object, packages, ages, and tests a plurality of chips on the Wafer at the same time, and finally cuts the Wafer into a single device, which can be directly mounted on a substrate or a printed circuit board, thereby reducing the Package size and the production cost.

Compared with the prior art, the packaging method of the MEMS circulator provided by the invention has the advantages that a plurality of chip units 2 which are of an integrated structure are manufactured on a wafer 1 in advance, a metal carrier 6 is placed and welded at the position corresponding to each chip unit 2 on the wafer 1 with the upward back surface, a permanent magnet 8 is dispensed and bonded at the position corresponding to each chip unit 2 on the wafer 1 with the upward front surface, the welding of the metal carrier 6 and the bonding of the permanent magnet 8 realize wafer-level operation, the problem that the welding flux overflows or the welding cavity defect is caused by the fact that the welding flux is easy to misplace due to the difficulty in contraposition of the welding flux in the chip-level packaging process adopted by the prior art is solved, and the packaging quality and the packaging efficiency are improved; in addition, due to the adoption of a wafer-level bonding mode, the permanent magnet 8 can be bonded quickly and efficiently, and the production efficiency is high;

after the metal carrier 6 is welded and the permanent magnet 8 is bonded, the wafer 1 is cut to obtain an independent MEMS circulator, and the obtained MEMS circulator is small in size, high in precision, good in consistency, suitable for miniaturization and large-batch packaging and manufacturing, and has important significance for popularization and application of the MEMS circulator in the field of 5G communication.

Referring to fig. 4, as an embodiment of the packaging method of the MEMS circulator provided by the present invention, before the placing the metal carrier 6 at the position corresponding to each chip unit 2 on the wafer 1 with the upward back surface, the method further includes: pre-cutting the back surface of the wafer 1 along a first scribing mark pre-manufactured on the back surface of the wafer 1; the precut depth is 50-100 μm.

The back surface of the wafer 1 is subjected to a first scribe mark by using a DRIE (Deep Reactive Ion Etching, a microelectronic dry Etching process, a fluorine-based gas-based high aspect ratio silicon Etching technique) dry Etching process.

In order to avoid damaging the metal carrier 6 when the wafer 1 is cut, the back surface of the wafer 1 is pre-cut, the pre-cutting depth is controlled to be 50-100 mu m, the rigidity of the wafer 1 is not influenced, and the metal carrier 6 is not damaged in the subsequent re-cutting process.

Referring to fig. 8, as an embodiment of the packaging method of the MEMS circulator of the present invention, the dicing the wafer 1 on which the metal carrier 6 is soldered and the permanent magnet 8 is mounted includes: cutting the front surface of the wafer 1 again along a second scribing mark pre-manufactured on the front surface of the wafer 1; wherein the re-cut position 9 corresponding to the second scribing mark coincides with the pre-cut position 5 corresponding to the first scribing mark.

The front side of the wafer 1 is manufactured with a second scribing mark by using a DRIE dry etching process, the metal circuit layer manufactured on the front side of the wafer 1 is divided into a plurality of chip units 2 through the second scribing mark, when the wafer 1 is re-cut along the second scribing mark, because the positions of the second scribing mark and the first scribing mark are consistent, on one hand, the chip units 2 of the independent MEMS circulator formed after the wafer 1 is re-cut can be aligned with the metal carrier 6 in order, on the other hand, the re-cutting position 9 is consistent with the pre-cutting position 5, the cutting dislocation is avoided, and the packaging quality of the MEMS circulator is ensured.

As a specific implementation manner of the packaging method of the MEMS circulator provided in the present invention, the re-cutting depth is a difference between the thickness of the wafer 1 and the pre-cutting depth plus a preset correction value; wherein the preset correction value ranges from 40 μm to 60 μm. And ensuring that the wafer 1 can be cut through by re-cutting to obtain an independent MEMS circulator, wherein the packaging quality of the MEMS circulator obtained after cutting is reliable.

As a specific embodiment of the packaging method of the MEMS circulator provided by the present invention, the width of the first scribe mark is greater than the width of the cutting blade during the pre-cutting, and the width of the second scribe mark is greater than the width of the cutting blade during the re-cutting.

The back of the wafer 1 is precut along the first scribing mark, the front of the wafer 1 is cut along the second scribing mark, because when the wafer 1 is cut by using a cutting blade (installed on a grinding wheel or automatic slicing equipment), the cut width is inevitably larger than the thickness of the cutting blade, the width of the first scribing mark and the width of the second scribing mark are processed to be larger than the thickness of the cutting blade, and therefore the MEMS circulator packaging product can be prevented from being damaged in the cutting process of the wafer 1, and the packaging quality of the independent MEMS circulator product obtained after cutting is guaranteed to be good.

Referring to fig. 3, as an embodiment of the packaging method of the MEMS circulator provided by the present invention, the solder layer 4 includes a plurality of solder areas distributed in an array, and each solder area is disposed corresponding to the chip unit 2 on the front surface of the wafer 1; each solder region has an area smaller than that of the corresponding chip unit 2, and is located directly below the corresponding chip unit 2.

After the solder layer 4 is melted, the solder layer is spread from the center of the independent area to the periphery under the pressure of the metal carrier 6, so that the area of the solder layer 4 is set to be smaller than the area of the corresponding chip unit 2, and the condition that the solder overflows from the independent area to influence the packaging quality can be avoided.

In this embodiment, the area of the solder layer 4 is set to 2/3 of the area of the corresponding chip unit 2, and the matched melting eutectic time is adopted, so that the metal carrier 6 acts on the appropriate pressure (which can be obtained through tests and calculations) of the solder layer 4, and it is ensured that the soldering surface of the metal carrier 6 is filled after the solder is melted eutectic, thereby ensuring stable soldering, and preventing the solder from overflowing the metal carrier 6 to affect the packaging quality. It will be appreciated that by testing the area and thickness of the solder layer 4 selected, the optimum soldering process temperature, time and pressure, and thus the optimum soldering quality, can be achieved.

As a specific implementation manner of the packaging method of the MEMS circulator provided by the present invention, the dispensing at the position corresponding to each chip unit 2 on the wafer 1 with the front surface facing upward includes: and dispensing glue in a glue dispensing identification pattern preset on each chip unit 2 on the wafer 1 with the front surface upward, wherein the roughness of the glue dispensing identification pattern is less than 1 mu m.

Each chip unit 2 on the wafer 1 is provided with a dispensing identification pattern which is round, annular, rectangular or square by adopting MEMS processing technologies such as photoetching, sputtering, electroplating and the like, so that the identification and the positioning of automatic dispensing equipment are facilitated, the dispensing position precision can be ensured, and the bonding position precision of the permanent magnet 8 is ensured;

because the height measurement function of the automatic dispensing equipment needs to be specific to the surface with certain roughness, in the embodiment, the surface roughness of the dispensing identification pattern is less than 1 μm, so that the surface quality of the dispensing identification pattern can be ensured, the dispensing identification pattern can be suitable for the height measurement function of the automatic dispensing equipment, and the dispensing height is ensured to be accurate, the glue amount is moderate, and the efficiency is high;

therefore, the process of dispensing and bonding the permanent magnet 8 can be performed by using automatic equipment aiming at all the chip units 2 arranged on the front surface of the wafer 1 in a matrix manner, so that wafer-level bonding operation is realized, the problem that the efficiency of dispensing and bonding operation performed on each independent chip unit 2 by using a chip-level operation method in the prior art is low is solved, the production operation efficiency is greatly improved, and the MEMS circulator can be suitable for batch production.

As a specific implementation manner of the packaging method of the MEMS circulator provided by the present invention, the metal carrier 6 is kovar alloy or molybdenum-copper alloy, and the bonding surface of the metal carrier 6 is made with a metal plating layer. Good electric and heat conducting performance and low thermal expansion coefficient.

As a specific implementation manner of the packaging method of the MEMS circulator provided by the present invention, the metal welding layer 3 and the metal plating layer are both Ni-Au plating layers; the solder layer 4 is Au — Sn solder. The melting eutectic time of the solder layer 4 is short, and the welding efficiency is high; after the solder layer 4 is molten and eutectic, the connection between the metal plating layer and the metal welding layer 3 is stable.

As a specific embodiment of the packaging method of the MEMS circulator provided in the present invention, the step of welding the metal carrier 6 and the back surface of the wafer 1 into a whole includes: placing the wafer 1 with the metal carrier 6 on the back surface in a graphite clamp; placing the graphite clamp with the wafer 1 and the metal carrier 6 in a vacuum sintering furnace, and carrying out fusion welding, wherein the gas in the welding process comprises the following components: formic acid.

By utilizing the high thermal conductivity of the graphite clamp, heat is conducted to the wafer 1, a certain pressing force is provided for the metal carrier 6, and the residual oxygen in the vacuum sintering furnace and the oxide layer on the surface of the metal are reduced by utilizing formic acid, so that the welding voidage is reduced, and the welding quality is ensured.

It should be understood that, in this embodiment, the welding process gas may also be hydrogen or other reducing gas, and the reducing gas may not be used in the absolute vacuum state in the vacuum sintering furnace.

It should be noted that, the steps in the embodiment of the present application are only used for identifying each step, and do not represent the sequence of each step, and the sequence of each step should be determined by the inherent logical relationship between each step.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.