CN112769031A

CN112769031A - Back integrated active device and preparation method thereof

Info

Publication number: CN112769031A
Application number: CN202011641052.9A
Authority: CN
Inventors: 张燕; 刘思旸; 翟文豪
Original assignee: United Microelectronics Center Co Ltd
Current assignee: United Microelectronics Center Co Ltd
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2021-05-07
Anticipated expiration: 2040-12-31
Also published as: CN112769031B

Abstract

The invention provides a back integrated active device and a preparation method thereof, belonging to the technical field of semiconductor devices and comprising a silicon substrate layer, a silicon waveguide structure and an active device layer; further comprising a thermal shunt layer and a cladding material layer; the thermal shunt layer is located between the silicon substrate layer and the active device layer, and is located on the outer side of the cladding material layer and is in contact with the cladding material layer to form a thermal flow channel. According to the invention, on the basis of a back-to-back process, the cladding material with heat conductivity is filled in the front surface of the silicon waveguide, and the thermal shunt layer structure is arranged between the silicon substrate layer and the active device layer, so that the heat dissipation effect of the back-to-back integrated active device is greatly improved, and the technical defects of high thermal resistance and poor heat conduction effect of the thermal shunt in the existing integrated active device are effectively overcome.

Description

Back integrated active device and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductor devices, in particular to a back integrated active device and a preparation method thereof.

Background

Silicon is used as an indirect band gap material, the luminous efficiency is low, and the current mainstream method at home and abroad is to realize the integration of a III-V laser and a silicon wafer by a heterogeneous bonding or off-chip packaging method. Although the off-chip package has good heat-conducting property, the requirement on alignment precision is high, mass production cannot be realized, and the packaging cost is high; the heterogeneous bonding integration can effectively reduce the packaging cost and improve the yield and the reliability, and is a key direction for research and development of various companies in recent years.

Since a thicker SiO layer is required for silicon waveguide₂The layer (1-2 μm) of cladding material limits the optical field distribution, making integrated active devices (e.g., lasers, modulators, etc.) very poor in heat dissipation. At present, the silicon dioxide can be prepared by reacting at SiO₂The grooves are dug and filled with materials with high thermal conductivity coefficients to form a thermal shunt to improve the heat dissipation performance of the integrated laser, so that the thermal resistance of the device is reduced.

In the existing integration process of a back-to-back integrated active device, due to the influence of a subsequent heterogeneous bonding process, a filling material in the thermal shunt is polycrystalline silicon, the thermal conductivity coefficient of the thermal shunt is greatly influenced by the size of crystal grains and is 15-60W/m/K, the thermal conductivity coefficient is far smaller than that of a metal material, and the thermal conductivity effect is limited; similarly, in the direct hetero-bonding approach, the bonding interface of the silicon layer and the active device layer should be as large as possible to enhance the bonding strength, but the existing hetero-bonding process limits the size of the thermal shunt, and the width is only a few microns to a dozen microns, thereby limiting its ability to dissipate heat.

Disclosure of Invention

The invention aims to overcome the defect of poor heat dissipation of an integrated active device in the prior art, and provides a backward integrated active device capable of effectively reducing the thermal resistance of the integrated device and a preparation method thereof.

The invention provides a back integrated active device, which comprises a silicon substrate layer, a silicon waveguide structure and an active device layer, wherein the silicon substrate layer is provided with a plurality of silicon waveguides; further comprising a thermal shunt layer and a cladding material layer; the thermal shunt layer is located between the silicon substrate layer and the active device layer, and is located on the outer side of the cladding material layer and is in contact with the cladding material layer to form a thermal flow channel. The cladding material with heat conductivity is filled in the front face of the silicon waveguide structure, and the thermal shunt layer structure is arranged between the silicon substrate layer and the active device layer, so that the heat dissipation effect of the integrated active device facing away from the silicon waveguide structure is greatly improved, and the technical defects of high thermal resistance and poor thermal conduction effect of the thermal shunt in the conventional integrated active device are effectively overcome.

The thermal shunt layer is made of a silicon layer and a thermal conductive material layer; the heat conduction material layer in the heat diverter layer is made of metal heat conduction materials or nonmetal heat conduction materials. The metal heat conducting material is copper or gold, for example. As the heat conductivity of the metal material is far greater than that of the polysilicon material (the thermal conductivity of copper is 401W/m/K, the thermal conductivity of gold is 317W/m/K, and the thermal conductivity of polysilicon is 15-60W/m/K), the metal material is used as the heat conduction material layer of the heat shunt layer, so that the heat conductivity of the heat shunt layer can be greatly improved. The non-metal heat conduction material is one or more of aluminum nitride, aluminum oxide, magnesium fluoride, polycrystalline silicon and monocrystalline silicon.

The cladding material layer is directly adjacent to the silicon substrate layer.

Preferably, the refractive index of the cladding material is lower than that of the silicon material; more preferably, the cladding material is a heat conducting medium material, such as one or more of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide. The cladding material layer is made of a heat-conducting medium material, so that the heat dissipation effect of the back-integrated active device can be further improved.

Preferably, the active device layer is one of a laser, a modulator and a detector.

In another aspect of the present invention, the present invention provides a method for manufacturing a backside integrated active device, comprising the steps of:

etching a silicon waveguide structure on a first silicon layer of an SOI substrate according to a preset pattern, and depositing a cladding material on the etched silicon layer to form a cladding material layer;

etching the cladding material to form a filling structure, depositing a heat conduction material layer in the filling structure to form a heat conduction material layer, wherein the heat conduction material layer and the silicon layer form a heat shunt layer;

bonding a carrier wafer on the surface of the thermal shunt layer, wherein the carrier wafer becomes a silicon substrate layer and is in contact with the cladding material layer; removing the silicon layer and the silicon dioxide layer on the second surface of the SOI substrate;

and step four, bonding an active device layer to the second silicon layer of the SOI substrate.

Preferably, after the step of bonding the carrier wafer on the surface of the thermal shunt layer, the method further comprises the step of turning over the carrier wafer.

Compared with the prior art, the technical scheme provided by the invention has the following advantages:

1. according to the back integrated active device and the preparation method thereof, on the basis of a back process, the cladding material with heat conduction performance is filled in the front surface of the silicon waveguide, and a metal or nonmetal heat shunt structure is adopted, so that the heat dissipation effect of the back integrated active device is greatly improved.

2. According to the back-side integrated active device and the preparation method thereof, the size of the thermal shunt layer can be unlimited, the transverse width of the thermal shunt layer between the silicon layer and the carrier wafer can be greatly improved, and the heat conduction effect of the thermal shunt layer is greatly improved.

3. The back integrated device and the preparation method thereof provided by the invention have the characteristic of being compatible with the subsequent process of CMOS.

Drawings

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

FIG. 1 is a schematic cross-sectional view of a prior art forward integrated active device;

FIG. 2 is a schematic cross-sectional view of a prior art forward integrated active device;

fig. 3 is a schematic cross-sectional view of a back-integrated active device in example 1;

fig. 4 is a schematic cross-sectional view of the fabrication process of fig. 3 for a backside integrated active device.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

FIG. 1 shows a schematic cross-sectional view of a forward integrated device fabricated using a heterogeneous bonding process in the prior art; in fig. 1, active device 20 is bonded directly to silicon layer 21, and thermal shunt 30 partially contacts active device 20, thereby directing heat generated by active device 20 through thermal shunt 30 made of polysilicon to silicon substrate layer 23, thereby achieving dissipation of heat from active device 20. However, the size of the thermal shunt 30 prepared by the existing heterogeneous bonding process is limited, the size is relatively small, only several micrometers to dozens of micrometers is required, the heat dissipation capability is limited, and the heat conduction effect is relatively poor.

Fig. 2 is a schematic cross-sectional view of the forward integrated device in fig. 1 prepared by a heterogeneous bonding process, wherein in fig. 2, steps (a) to (d) are included, and an SOI substrate is first selected, and comprises a silicon layer 21, a silicon substrate layer 23 and a silicon dioxide layer 22 sandwiched between the silicon layer 21 and the silicon substrate layer 23; then, etching the silicon layer 21 to obtain a silicon waveguide shape, as shown in step (b) in fig. 2; then trenching and filling with polysilicon material at a distance of at least 5 microns from the silicon waveguide to form a thermal shunt 30, as shown in step (c) of fig. 2, but the thermal conductivity of polysilicon is greatly affected by the grain size, typically 15-60W/m/K, which is much smaller than that of metallic material; the active device layer 20 is then bonded to complete the fabrication of the forward integrated device.

Example 1

Referring to fig. 3, embodiment 1 provides a back-integrated active device comprising a silicon substrate layer 1, a silicon waveguide structure, an active device layer 10, a thermal shunt layer, and a cladding material layer 12; the thermal shunt layer is located between the silicon substrate layer 1 and the active device layer 10, is located outside the cladding material layer 12, and is in contact with the cladding material layer 12 to form a thermal flow channel.

According to the invention, on the basis of a back-to-back process, the cladding material with heat conductivity is filled in the front surface of the silicon waveguide structure, and the thermal shunt layer structure is arranged between the silicon substrate layer and the active device layer, so that the heat dissipation effect of the back-to-back integrated active device is greatly improved, and the technical defects of high thermal resistance and poor heat conduction effect of the thermal shunt in the existing integrated active device are effectively overcome.

The active device layer 10 may be one of a laser, a modulator, and a detector, and the embodiment adopts a laser as the active device layer.

The heat diverter layer is made of a silicon layer 11 and a heat conducting material layer 40, the heat conducting material layer 40 in the heat diverter layer is located on both sides of the cladding material layer 12 and is in a non-groove-shaped structure, and the heat conducting material layer 40 is made of a non-metal heat conducting material or a metal heat conducting material, wherein the metal heat conducting material can be copper or gold, and the embodiment is preferably made of a metal material copper; in other embodiments, thermally conductive materials such as aluminum nitride, aluminum oxide, magnesium fluoride, polysilicon, and single crystal silicon may also be used.

As the heat conductivity of the metal material is far greater than that of the polysilicon material (the thermal conductivity of copper is 401W/m/K, the thermal conductivity of gold is 317W/m/K, and the thermal conductivity of polysilicon is 15-60W/m/K), the metal material is adopted as the heat conduction material layer 40 of the heat shunt layer, so that the heat conductivity of the heat shunt layer can be greatly improved. The heat conduction material layer 40 and the silicon layer 11 form a heat flow channel, and the heat conduction performance of the silicon layer 11 and the heat conduction material layer 40 is much higher than that of silicon dioxide; therefore, the heat dissipation effect is greatly enhanced. Meanwhile, under the structure, the formed heat conduction channel is in a non-groove-shaped structure, and compared with a groove-shaped heat dissipation channel in the prior art, the heat dissipation effect is further improved.

The cladding material layer 12 is arranged between the silicon layer 11 and the silicon substrate layer 1, the refractive index of the cladding material 12 is lower than that of the silicon material, the cladding material layer 12 is directly adjacent to the silicon substrate layer 1, and no silicon dioxide layer is arranged in the middle. The cladding material is a heat conducting medium material, the heat conducting medium material may be at least one or any combination of silicon dioxide, silicon nitride, aluminum nitride and aluminum oxide, and in this embodiment, an aluminum oxide material is preferably used. The cladding material layer 12 is made of a heat conducting medium material, so that the heat dissipation effect of the back integrated active device can be further improved.

Example 2

Embodiment 2 provides a method for manufacturing a backside integrated active device, which specifically includes the following steps with reference to (a) to (g) in fig. 4:

the method comprises the following steps: as shown in fig. 4 (a), a silicon waveguide structure is etched on the first side of the SOI substrate, i.e., the silicon layer 11, according to a predetermined pattern, as shown in fig. 4 (b).

Step two: referring to (c) in fig. 4, a cladding material is deposited on the etched silicon layer 11 to form a cladding material layer 12, where the cladding material is a heat-conducting medium material, and may be at least one or any combination of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide, and in this embodiment, is preferably aluminum oxide.

Step three: etching the cladding material to form a filling structure, and depositing a heat conductive material in the filling structure to form a heat conductive material layer 40, as shown in (d) of fig. 4; the heat conduction material can be selected from metal heat conduction materials or nonmetal heat conduction materials, and the metal materials are preferably copper or gold; the non-metal heat conduction material is preferably at least one of aluminum nitride, aluminum oxide, magnesium fluoride, polycrystalline silicon and monocrystalline silicon; the heat conductive material in this embodiment is preferably a metal material such as copper.

As the heat conductivity of the metal material is far greater than that of the polysilicon material (the thermal conductivity of copper is 401W/m/K, the thermal conductivity of gold is 317W/m/K, and the thermal conductivity of polysilicon is 15-60W/m/K), the metal material is adopted as the heat conduction material layer 40 of the heat shunt, so that the heat conductivity of the heat shunt layer can be greatly improved.

Step four: bonding the carrier wafer 1 on the surfaces of the heat conductive material layer 40 and the cladding material layer 12, as shown in fig. 4 (d), wherein the carrier wafer 1 is the silicon substrate layer 1 and is in contact with the cladding material layer 12.

Step five: the silicon layer 13 and the silicon dioxide layer 14 on the second side of the SOI substrate are removed, as shown with reference to (e) in fig. 4.

Step six: turning over of the carrier wafer 1 is performed as shown in (f) of fig. 4; the carrier wafer 1 is turned over, so that the implementation of a subsequent bonding process of the active device layer 10 is facilitated, and the process difficulty of bonding the active device layer 10 is reduced.

Step seven: the active device layer 10 is bonded to the silicon layer 11 to complete the fabrication of the back-integrated active device, as shown in (g) of fig. 4. The active device layer 10 may be a laser, a modulator or a detector, and a laser is used in this embodiment.

At this time, the heat flow path formed by the silicon layer 11 and the heat conductive material layer 40 is a heat flow path, and the heat conductive performance of the silicon layer 11 and the heat conductive material layer 40 is much higher than that of silicon dioxide, so that the heat dissipation effect is greatly enhanced. Meanwhile, under the structure, the formed heat conduction channel is in a non-groove-shaped structure, and compared with a groove-shaped heat dissipation channel in the prior art, the heat dissipation effect is further improved.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims

1. A back integrated active device comprises a silicon substrate layer, a silicon waveguide structure and an active device layer; the heat-transfer device is characterized by further comprising a heat diverter layer and a cladding material layer; the thermal shunt layer is located between the silicon substrate layer and the active device layer, located outside the cladding material layer and in contact with the cladding material layer to form a thermal flow channel.

2. The active device of claim 1, wherein the thermal shunt layer is made of a layer of silicon and a layer of thermally conductive material; the heat conduction material layer in the heat diverter layer is made of metal heat conduction materials or nonmetal heat conduction materials.

3. The active device of claim 2, wherein the metal thermal conductive material is copper or gold.

4. The active device of claim 2, wherein the non-metallic thermally conductive material is one or more of aluminum nitride, aluminum oxide, magnesium fluoride, polysilicon, and single crystal silicon.

5. The active device of claim 1, wherein the cladding material layer is directly adjacent to the silicon substrate layer.

6. The active device of claim 5, wherein the cladding material layer has a lower refractive index than the silicon material.

7. The active device of claim 6, wherein the cladding material is a thermally conductive dielectric material.

8. The active device of claim 7, wherein the thermal conductive material is one or more selected from the group consisting of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide.

9. A method for preparing a back-to-back integrated active device is characterized by comprising the following steps:

etching a silicon waveguide structure on a first silicon layer of an SOI substrate according to a preset pattern, and depositing a cladding material on the etched silicon layer;

etching the cladding material to form a filling structure, and depositing a heat conduction material layer in the filling structure; the layer of thermally conductive material and the layer of silicon form a thermal shunt layer;

10. The method of claim 9, further comprising turning the carrier wafer over after the step of bonding the carrier wafer to the surface of the thermal shunt layer.