CN102786026B - Film sealing cap packaging structure for MEMS optical device and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a thin-film sealing cap packaging structure and a manufacturing method thereof, in particular to a thin-film sealing cap packaging structure for MEMS optical devices and a manufacturing method thereof. Specifically, the prepared thin-film sealing cap can satisfy wafer-level and The requirements for chip-level packaging belong to the technical field of MEMS packaging. According to the technical solution provided by the present invention, the thin-film cap packaging structure for MEMS optical devices includes a substrate and a MEMS optical structure on the substrate; a thin-film cap is set on the substrate, and the thin-film The end edge of the sealing cap is bonded and fixedly connected to the substrate through the bonding layer; a cavity for containing the MEMS optical structure is formed between the thin film sealing cap and the substrate, and the MEMS optical structure is located in the cavity. The invention has the advantages of compact structure, convenient manufacture, reduced manufacturing cost, good air tightness, wide application range, safety and reliability.

Description

A thin-film sealing cap packaging structure for MEMS optical devices and its manufacturing method

technical field

The present invention relates to a thin-film sealing cap packaging structure and a manufacturing method thereof, in particular to a thin-film sealing cap packaging structure for MEMS optical devices and a manufacturing method thereof. Specifically, the prepared thin-film sealing cap can meet requirements of wafer-level and The requirements for chip-level packaging belong to the technical field of MEMS packaging.

Background technique

Since Faraday first observed the phenomenon of thin film deposition in 1857, thin film manufacturing technology has been widely used. From the earliest application in toys and textile industries to the ubiquitous integrated circuits now, thin film preparation technology has almost penetrated into our daily life. In every corner of the world, according to statistics, the global annual sales of thin-film equipment alone can reach tens of billions of dollars, and the sales of products manufactured using these thin-film equipment are more than 100 times. Not only are they widely used, but the technology of thin-film deposition It has also made rapid progress and developed many types. The IC manufacturing industry will update its equipment every 5 years. There are a large number of thin film preparation equipment. A few millimeters, it can be seen that the thin film preparation technology has been making rapid progress, and the corresponding theoretical research is very in-depth and extensive, from the classical thermodynamic theory to the nucleation theory based on atomic-level observations, almost involving every aspect of thin film science, MEMS The planar process in LIGA can be said to be a combination of thin film deposition technology, photolithography and etching technology. The masking layer, sacrificial layer, and electroplating in LIGA technology are all inseparable from thin film preparation technology.

As far as MEMS (Micro-Electro-Mechanical Systems) packaging is concerned, depending on the product, the packaging cost of MEMS accounts for 40% to 80% of the entire MEMS product; at the same time, the performance and reliability of MEMS devices and their packaging forms and packaging Technology is inextricably linked. Due to the special structure of MEMS devices, its packaging is much more complicated than that of traditional integrated circuit packaging: first, it is necessary to consider the equally important electrical and mechanical components in MEMS devices; second, some MEMS devices need to be in contact with the external environment or with the outside world The environment is completely isolated; finally, as the size of MEMS structures and the circuits accompanying MEMS are getting smaller and smaller.

The earliest capping patents on MEMS were proposed by some established semiconductor companies that have been engaged in MEMS research for many years in the late 1980s and early 1990s. The most commonly used process is to manufacture the cap array by etching the silicon wafer, etch the cap array area, and pre-cut it so as to be divided into individual caps, and then bond the cap array to the MEMS wafer. to combine. After capping, the MEMS wafer can be divided and cleaned, and the protected wafer can be packaged or assembled in a packaging foundry. At the same time, it is also possible to introduce a conductor on the sealing cap by using the through-hole technology, so as to realize the communication with the external bonding pad on the sealing cap.

For MEMS optical devices, such as micromirrors, infrared sensors, etc., they usually need to work normally in a certain vacuum environment. All manufacturers are looking for packaging solutions with smaller packaging volume, better airtightness, and higher reliability. Chip-level or even wafer-level MEMS packaging has become an important research direction in the research field. Among them, the chip-level or wafer-level packaging process based on thin-film technology has been vigorously developed. For example, many RF devices are now widely used Thin film technology for die capping. In the field of infrared imaging sensors, thin-film vacuum capping technology based on sacrificial layer technology is regarded as the key to realizing the "fourth generation - pixel-level packaging". Many scientific research institutions and commercial companies continue to propose new ideas and concepts.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a thin film sealing cap packaging structure and manufacturing method for MEMS optical devices, which has compact structure, convenient manufacture, reduced manufacturing cost, and good airtightness. Wide adaptability, safe and reliable.

According to the technical solution provided by the present invention, the thin-film cap packaging structure for MEMS optical devices includes a substrate and a MEMS optical structure on the substrate; a thin-film cap is arranged on the substrate, and the thin-film The end edge of the sealing cap is bonded and fixedly connected to the substrate through the bonding layer; a cavity for containing the MEMS optical structure is formed between the thin film sealing cap and the substrate, and the MEMS optical structure is located in the cavity.

The outer surface of the film sealing cap is covered with a first optical anti-reflection film, the inner surface of the film sealing cap is covered with a second optical anti-reflection film, and the second optical anti-reflection film is located directly above the MEMS optical structure.

A getter layer is arranged on the inner surface of the thin film cap, and the getter layer is activated when the thin film cap is bonded to the substrate through the bonding layer.

The substrate is provided with an electrical connection through hole penetrating the substrate, and the electrical connection through hole is electrically connected with the MEMS optical structure.

A method for manufacturing a thin-film cap packaging structure for MEMS optical devices, the method for manufacturing a thin-film cap packaging structure comprises the following steps:

a. Provide a transfer wafer, and polish the two opposite surfaces of the transfer wafer; deposit an anti-sticking layer on one surface of the transfer wafer after surface polishing, and set a transfer support protection layer on the anti-sticking layer ;

b. selectively masking and etching the transit support protection layer to form desired pits in the transit support protection layer;

c. Depositing a thin film material on the surface of the transfer support protective layer corresponding to the pits to obtain the required film cap, and the film cap covers the surface of the transfer support protective layer;

d, making a bonding layer on the above-mentioned film sealing cap, the bonding layer is located at the outer ring of the pit and is formed on the end edge of the film sealing cap;

e, providing a substrate, on which the required MEMS optical structure is set;

f. In a vacuum state, the above-mentioned film cap is bonded to the substrate through the bonding layer, and the MEMS optical structure is located in the cavity formed between the film cap and the substrate;

g. Remove the transfer support protection layer, the anti-adhesive layer and the transfer wafer on the film cap to obtain the required film cap packaging structure.

In the step c, before forming a thin-film cap on the surface of the transit support protective layer, a first optical anti-reflection film is first formed on the bottom of the pit, the thin-film cap is covered in the first optical anti-reflection film, and the thin-film cap is A second optical anti-reflection film is arranged on the cap, and the second optical anti-reflection film is distributed correspondingly to the first optical anti-reflection film.

The material of the film sealing cap includes aluminum oxide, silicon oxide, silicon nitride, polysilicon, zinc selenide, zinc sulfide, calcium fluoride, zinc oxide, germanium, selenium, magnesium oxide or titanium oxide.

The thickness of the thin film sealing cap is 500nm, and the material of the first optical anti-reflection film includes titanium oxide.

The transit support protective layer is photoresist, and the anti-adhesive layer is silicon dioxide.

The substrate is provided with an electrical connection through hole penetrating the substrate, and the electrical connection through hole is electrically connected with the MEMS optical structure.

Advantages of the present invention:

1. The thin-film sealing cap structure for MEMS optical devices proposed in the present invention adopts the method of transfer wafer transfer bonding, and the material selection of the thin-film sealing cap is more flexible and diverse, which can meet the needs of various optical applications.

2. The thin-film sealing cap packaging structure for MEMS optical devices proposed in the present invention is prepared on the transfer wafer 3, which increases the flexibility of process integration and emphasizes the separate preparation of thin-film sealing caps and MEMS optical structures. It avoids the mutual adverse influence between the material selection and the process when the film sealing cap 4 and the MEMS optical structure and the substrate are prepared together; by selecting a suitable bonding method, the stress problem between the two can be avoided, and it is suitable for a variety of According to the needs of optical applications, corresponding optical antireflection coating materials can be flexibly coated on the inner and outer surfaces of the film; in addition, adsorbent materials can also be evaporated or sputtered on the inner surface of the film cap, so it can meet high air tightness encapsulation requirements as needed.

3. The transfer support protection layer proposed in the present invention for preparing the entire array of film caps on the transit wafer acts as a protective layer for the film caps during the scribing process, preventing the wafers completed by sealing the film caps from being scratched during scribing. Adverse effects on the film process.

4. The manufacturing method of the thin film sealing cap for MEMS optical devices proposed in the present invention is compatible with commonly used packaging processes and technologies, and is applicable to various MEMS device structures. According to different packaging forms and materials used, it covers chip-level packaging, wafer-level packaging, chip-to-wafer packaging, vacuum packaging, hermetic packaging, and non-hermetic packaging of MEMS devices; suitable for adhesive bonding, glass Paste bonding or eutectic bonding techniques.

Description of drawings

1 to 10 are cross-sectional views of the implementation of specific processes for forming the packaging structure of the present invention, wherein

Fig. 1 is a cross-sectional view of the present invention after forming an anti-adhesive layer and a transfer support protection layer on a transfer wafer.

Fig. 2 is a cross-sectional view of the present invention after forming pits on the intermediate support protection layer.

Fig. 3 is a cross-sectional view of the present invention after forming the first optical anti-reflection film in the pit.

FIG. 4 is a cross-sectional view of the present invention after forming a thin-film cap on the first anti-reflection film.

Fig. 5 is a cross-sectional view of the present invention after forming a bonding layer on the film cap.

Fig. 6 is a cross-sectional view of the present invention after the second optical anti-reflection film is arranged on the film cap.

FIG. 7 is a cross-sectional view of the present invention when the substrate and the MEMS optical structure are provided and the substrate and the thin-film cap are aligned.

Fig. 8 is a cross-sectional view of the film cap of the present invention after being bonded to the substrate through the bonding layer.

FIG. 9 is a cross-sectional view of the present invention after removing the transfer wafer and the anti-sticking layer on the film cap.

FIG. 10 is a cross-sectional view of the present invention after removing the intermediate support protection layer to form the desired packaging structure.

Explanation of reference numerals: 1-transfer support protection layer, 2-anti-adhesive layer, 3-transfer wafer, 4-film sealing cap, 5-bonding layer, 6-first optical anti-reflection film, 7-second optical Anti-reflection coating, 8-MEMS optical structure, 9-substrate, 10-electrical connection through hole and 11-cavity.

Detailed ways

The present invention will be further described below in conjunction with specific drawings and embodiments.

As shown in Figure 10: it is a schematic diagram of the structure of the thin film sealing cap package for MEMS optical devices formed by the present invention, the present invention includes a substrate 9 and a MEMS optical structure 8 located on the substrate 9; Thin film sealing cap 4, the end edge of described thin film sealing cap 4 is bonded and fixedly connected with substrate 9 through bonding layer 5; The cavity 11 that accommodates MEMS optical structure 8 is formed between thin film sealing cap 4 and substrate 9, so The MEMS optical structure 8 is located in the cavity 11 . Wherein, the MEMS optical structure 8 is prepared on the substrate 9 through a required process, which is well known to those skilled in the art, and the specific preparation process will not be described in detail here. The substrate 9 is provided with an electrical connection through hole 10, and the electrical connection through hole 10 penetrates the substrate 9, and the MEMS optical structure 8 can be connected with an external circuit through the electrical connection through hole 10, so that the MEMS optical structure 8 is connected to the external circuit. 3D package connection.

In order to improve the working environment of the MEMS optical structure 8, the outer surface of the thin film sealing cap 4 is covered with a first optical antireflection film 6, and the inner surface of the thin film sealing cap 4 is covered with a second optical antireflection film 7. The second optical anti-reflection film 7 is located right above the MEMS optical structure 8 . The thin film sealing cap 4 is transparent, through the first optical anti-reflection film 6 and the second optical anti-reflection film 7 can filter out light of different wavelengths, so that the light matched with the MEMS optical structure 8 can enter the cavity 11 more effectively , and cooperate with the MEMS optical structure 8 . The outer surface of the film cap 4 refers to the side surface away from the substrate 9 , and the inner surface of the film cap 4 refers to the side surface adjacent to the substrate 9 .

A getter layer is provided on the inner surface of the thin film cap 4 and is activated when the thin film cap 4 is bonded to the substrate 9 through the bonding layer 5 . The vacuum degree in the cavity 11 can be ensured by the getter layer, so as to ensure the vacuum degree of the packaging environment of the MEMS optical structure 8 .

As shown in Figures 1 to 10: the thin film sealing cap packaging structure of the above structure is realized through the following process steps, specifically:

a. Provide an intermediary wafer 3, and polish two opposite surfaces of the intermediary wafer 3; deposit an anti-sticking layer 2 on one surface of the intermediary wafer 3 after surface polishing, and Set the transit support protection layer 1;

As shown in Figure 1: the material of the transfer wafer 3 is silicon, the thickness of the transfer wafer 3 is 300 μm, and the silicon dioxide of 2 μm is deposited as the anti-sticking layer 2 by using the plasma-enhanced chemical vapor deposition method, and then coated with The melter coats the photoresist SU-8 with a thickness of 5 μm on the anti-adhesive layer 2 as the transfer support protective layer 1;

b. selectively masking and etching the transit support protection layer 1 to form the required pits in the transit support protection layer 1;

As shown in Figure 2: the shape of the pit is consistent with the shape of the film cap 4 that needs to be formed. In the embodiment of the present invention, the shape of the pit is a direction groove, and the depth of the pit is lower than the transfer support protective layer 1 thickness;

c. Deposit a thin film material on the surface of the transfer support protection layer 1 corresponding to the pits to obtain the required film cap 4, and the film seal cap 4 covers the surface of the transfer support protection layer 1;

In the embodiment of the present invention, before forming the film sealing cap 4 on the surface of the transit support protective layer 1, the first optical anti-reflection film 6 is first formed on the bottom of the pit, and the film sealing cap 4 is covered in the first optical anti-reflection film 6 , and a second optical anti-reflection film 7 is provided on the film cap 4, and the second optical anti-reflection film 7 is distributed correspondingly to the first optical anti-reflection film 6.

The material of the thin film cap 4 includes aluminum oxide, silicon oxide, silicon nitride, polysilicon, zinc selenide, zinc sulfide, calcium fluoride, zinc oxide, germanium, selenium, magnesium oxide or titanium oxide.

In a specific embodiment, the first optical anti-reflection film 6 is prepared on the transit support protective layer 1 with pits by means of electron beam evaporation, and the material of the first optical anti-reflection film 6 is titanium oxide, as shown in FIG. 3 . The first optical anti-reflection film 6 covers the bottom surface of the pit, and then an aluminum oxide film is prepared on the first optical anti-reflection film 6 by magnetron sputtering to form a thin film cap 4, and the thin film cap 4 The thickness is 500nm, as shown in Figure 4.

Coating polyimide on the film cap 4 prepared above, photolithography under the mask of a metal mask, using carbon tetrafluoride process gas to make bonding area patterns, and using electron beam evaporation to prepare respectively Titanium material layer and indium material layer are as bonding layer 5, and the thickness of titanium material layer is 50nm, and the thickness of indium material layer is 2 μ m; As shown in Figure 5; Wherein, titanium material layer is as adhesion layer, improves indium material layer and Adhesion on the film cap 4 , the indium material layer acts as a subsequent bonding function, and the bonding layer 5 is located on the outer ring of the pit, that is, the end edge of the film cap 4 . After the above preparation, the corresponding polyimide is removed.

Coating polyimide again, photolithography under the mask of a metal mask, using carbon tetrafluoride process gas to make an anti-reflection film pattern, and again using electron beam evaporation to prepare a titanium oxide anti-reflection film to form The second optical anti-reflection coating 7 is shown in FIG. 6 .

d. Make a bonding layer 5 on the above-mentioned film sealing cap 4, the bonding layer 5 is located at the outer ring of the pit and is formed on the end edge of the film sealing cap 4;

Above-mentioned specific embodiment has illustrated the preparation process of bonding layer 5, when the first optical anti-reflection film 6, the second optical anti-reflection film 7 are not arranged on the thin film sealing cap 4, after the equipment obtains the thin film sealing cap 4, directly on the The support plate bonding layer 5 is on the film sealing cap 4 .

e, providing a substrate 9, on which the required MEMS optical structure 8 is set;

As shown in Figure 7: the corresponding MEMS optical structure 8 is prepared by the required process on the substrate 9, and the optical function is realized through the MEMS optical structure 8. The substrate 9 is provided with an electrical connection through hole 10, and through the electrical connection through hole 10 can electrically connect the MEMS optical structure 8 with the outside.

f. In a vacuum state, the above-mentioned film cap 4 is bonded to the substrate 9 through the bonding layer 5, and the MEMS optical structure 8 is located in the cavity 10 formed between the film cap 4 and the substrate 9;

As shown in Figure 8: use EVG501 wafer bonding machine, use the alignment mark to align and bond the transfer wafer 3 with the film cap 4 and the substrate 9, and the bonding temperature is 180 degrees Celsius, which meets the bonding requirements. The bonding conditions of the material indium; the vacuum degree of the bonding chamber is 0.1 Pa, the bonding pressure is 1 MPa, and the bonding time is 15 minutes; as shown in Figure 7 and Figure 8;

g. Remove the transfer support protection layer 1, the anti-adhesive layer 2 and the transfer wafer 3 on the film cap 4 to obtain the required film cap packaging structure.

Use wet etching to remove the anti-sticking layer 2 on the transfer wafer 3, and separate the transfer wafer 3; as shown in Figure 9; use a mechanical dicing machine to cut the wafer, so that each MEMS device is separated and independent; Remove the transfer support protective layer 1 by dry method to release the film capping structure; as shown in FIG. 10 .

The thin-film capping structure for MEMS optical devices proposed in the present invention adopts the method of transfer bonding of the transfer wafer 3, and the material selection of the thin-film capping 4 is more flexible and diverse, which can meet the needs of various optical applications.

The thin-film sealing cap packaging structure for MEMS optical devices proposed in the present invention is prepared on the transfer wafer 3, which increases the flexibility of process integration and emphasizes the separate preparation of the thin-film sealing cap 4 and the MEMS optical structure 8, as far as possible It avoids the adverse influence between the material selection and the process when the thin film sealing cap 4 and the MEMS optical structure 8 and the substrate 9 are prepared together; by selecting a suitable bonding method, the stress problem between the two can be avoided. According to the needs of various optical applications, corresponding optical anti-reflection coating materials can be flexibly coated on the inner and outer surfaces of the film; in addition, the adsorbent material can also be evaporated or sputtered on the inner surface of the film cap 4, so it can meet high The need for hermetic packaging requirements.

The photoresist bottom mold proposed in the present invention that is used to prepare the entire array of thin film caps on the transfer wafer 3 acts as a protective layer for the thin film caps 4 during the scribing process, preventing the wafers from being sealed by the film caps 4. Adverse effects on the scribing process.

The manufacturing method of the thin film sealing cap for MEMS optical devices proposed in the present invention is compatible with commonly used packaging process flow and technology, and is applicable to various MEMS device structures. According to different packaging forms and materials used, it covers chip-level packaging, wafer-level packaging, chip-to-wafer packaging, vacuum packaging, hermetic packaging, and non-hermetic packaging of MEMS devices; suitable for adhesive bonding, glass Paste bonding or eutectic bonding techniques. Among the above bonding types, chip-level packaging, wafer-level packaging, and chip-to-wafer packaging are classified according to the size of the package; vacuum packaging, hermetic packaging, and non-hermetic packaging are classified according to the airtightness of the packaging cavity; Adhesive bonding, glass paste bonding, and eutectic bonding are classified according to bonding materials; if a certain packaging form is classified differently, it can be classified into multiple types.

This embodiment can be used to illustrate the structure and manufacturing process of the present invention, but the implementation of the present invention is by no means limited to this embodiment. Various substitutions, changes and modifications are possible without departing from the scope of the invention and the appended claims. Therefore, the protection scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims (2)

1., for a film sealing cap encapsulating structure for MEMS optics, comprise substrate (9) and be positioned at the MEMS optical texture (8) on described substrate (9); It is characterized in that: described substrate (9) is arranged film sealing cap (4), the end edge of described film sealing cap (4) is fixedly connected with substrate (9) bonding by bonded layer (5); Form the cavity (11) holding MEMS optical texture (8) between film sealing cap (4) and substrate (9), described MEMS optical texture (8) is positioned at cavity (11);

The outer surface of described film sealing cap (4) is coated with the first optical anti-reflective film (6), the inner surface of film sealing cap (4) is coated with the second optical anti-reflective film (7), described second optical anti-reflective film (7) is positioned at directly over MEMS optical texture (8);

The inner surface of described film sealing cap (4) arranges getter layer, and at film sealing cap (4) by bonded layer (5) and activated degasser layer during substrate (9) bonding;

Be provided with the electrical connection vias (10) of Through-substrate (9) in described substrate (9), described electrical connection vias (10) is electrically connected with MEMS optical texture (8).

2. for a film sealing cap encapsulating structure manufacture method for MEMS optics, it is characterized in that, described film sealing cap encapsulating structure manufacture method comprises the steps:

(a), transfer wafer (3) is provided, and polishing is carried out to two opposite face of described transfer wafer (3); A deposited on silicon adherent layer (2) of the transfer wafer (3) after surface finish, and transfer support protective layer (1) is set on adherent layer (2);

(b), optionally shelter and etch transfer and support protective layer (1), to support the pit in protective layer (1) needed for formation in transfer;

(c), support protective layer (1) correspondence in transfer and form the surface deposition thin-film material of pit, obtain required film sealing cap (4), described film sealing cap (4) covers the surface that transfer supports protective layer (1);

(d), on above-mentioned film sealing cap (4), make bonded layer (5), described bonded layer (5) is positioned at the outer ring of pit, is formed at the end edge of film sealing cap (4);

(e), substrate (9) is provided, described substrate (9) is arranged required MEMS optical texture (8);

(f), under vacuum conditions, above-mentioned film sealing cap (4) is carried out bonding by bonded layer (5) and substrate (9), and MEMS optical texture (8) is positioned at the cavity (10) formed between film sealing cap (4) and substrate (9);

G (), the transfer of removing on film sealing cap (4) support protective layer (1), adherent layer (2) and transfer wafer (3), obtain required film sealing cap encapsulating structure;

In described step (c), surface formation film sealing cap (4) supporting protective layer (1) in transfer is front, first form the first optical anti-reflective film (6) in the bottom of pit, film sealing cap (4) is covered in the first optical anti-reflective film (6), and the second optical anti-reflective film (7) is set on film sealing cap (4), described second optical anti-reflective film (7) is corresponding with the first optical anti-reflective film (6) to be distributed;

The material of described film sealing cap (4) comprises aluminium oxide, silica, silicon nitride, polysilicon, zinc selenide, zinc sulphide, calcirm-fluoride, zinc oxide, germanium, selenium, magnesium oxide or titanium oxide;

The thickness of described film sealing cap (4) is 500nm, and the material of the first optical anti-reflective film (6) comprises titanium oxide;

It is photoresist that described transfer supports protective layer (1), and adherent layer (2) is silicon dioxide;

Be provided with the electrical connection vias (10) of Through-substrate (9) in described substrate (9), described electrical connection vias (10) is electrically connected with MEMS optical texture (8).