CN112769031B - Back integrated active device and preparation method thereof - Google Patents

Abstract

The invention provides a back integrated active device and a preparation method thereof, which belong to the technical field of semiconductor devices and comprise 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 positioned between the silicon substrate layer and the active device layer, and is positioned outside the cladding material layer to be in contact with the cladding material layer, so that a heat flow channel is formed. On the basis of a back-to-back process, the cladding material with heat conduction performance is filled on the front surface of the silicon waveguide, and the heat diverter 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 larger heat resistance and poor heat conduction effect of the heat diverter 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 practice at home and abroad is to integrate the III-V laser and the silicon wafer by a heterogeneous bonding or off-chip packaging method. Although the off-chip package has good heat conduction performance, the alignment precision requirement is higher, the mass production cannot be realized, and the package cost is higher; the heterogeneous bonding integration can effectively reduce the packaging cost, improve the yield and the reliability, and is an important direction of research and development of various companies in recent years.

Since silicon waveguides require a thicker layer of SiO ₂ The cladding material is layered (1-2 μm) to limit the optical field distribution, making the heat dissipation of integrated active devices (e.g., lasers, modulators, etc.) very poor. Currently, the method can be realized by the method of preparing a silicon oxide film on SiO ₂ The layers are grooved and filled with high thermal conductivity materials to form thermal shunts to improve the heat dissipation of the integrated laser, thereby reducing the thermal resistance of the device.

In the existing integration process of the back integrated active device, the filling material in the thermal shunt is polysilicon due to the influence of the subsequent heterobonding process, the heat conductivity coefficient of the filling material is greatly influenced by the grain size and is 15-60W/m/K, and the heat conductivity coefficient is far smaller than that of a metal material, so that the heat conductivity effect is limited; also, in the direct heterobonding mode, the bonding interface between the silicon layer and the active device layer should be as large as possible to enhance the bonding strength, but the conventional heterobonding process limits the size of the thermal shunt to only a few micrometers to tens of micrometers, thereby limiting the heat dissipation capability thereof.

Disclosure of Invention

The invention aims to overcome the defect of poor heat dissipation of an integrated active device in the prior art, thereby providing a back 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; further comprising a thermal shunt layer and a cladding material layer; the thermal shunt layer is positioned between the silicon substrate layer and the active device layer, and is positioned outside the cladding material layer to be in contact with the cladding material layer, so that a heat flow channel is formed. The cladding material with heat conducting property is filled on the front surface of the silicon waveguide structure, the heat diverter 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 is greatly improved, and the technical defects of large heat resistance and poor heat conducting effect of the heat diverter in the existing integrated active device are effectively overcome.

The thermal shunt layer is made of a silicon layer and a heat conducting material layer; the heat conducting material layer in the heat shunt layer is a metal heat conducting material or a nonmetal heat conducting material. The metal heat conductive material is, for example, copper or gold. Because the heat conduction performance of the metal material is far greater than that of the polysilicon material (the heat conduction coefficient of copper is 401W/m/K, the heat conduction coefficient of gold is 317W/m/K, and the heat conduction coefficient of polysilicon is 15-60W/m/K), the heat conduction performance of the heat shunt layer can be greatly improved by adopting the metal material as the heat conduction material layer of the heat shunt layer. The non-metallic thermally conductive material is, for example, one or more combinations of aluminum nitride, aluminum oxide, magnesium fluoride, polysilicon, and monocrystalline silicon.

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

Preferably, the cladding material has a lower refractive index than 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 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, the present invention provides a method for fabricating a back-integrated active device, comprising the steps of:

etching a silicon waveguide structure on a first surface 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 conducting material in the filling structure to form a heat conducting material layer, and forming a heat shunt layer by the heat conducting material layer and the silicon layer;

bonding a carrier wafer on the surface of the thermal shunt layer, wherein the carrier wafer is a silicon substrate layer and is contacted 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 first silicon-on-insulator layer of the SOI substrate.

Preferably, after the step of bonding the carrier wafer to the surface of the thermal shunt layer, the method further comprises a step of flipping 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-facing process, the cladding material with heat conduction performance is filled in the front surface of the silicon waveguide, and the metal or nonmetal heat diverter structure is adopted, so that the heat dissipation effect of the back-integrated active device is greatly improved.

2. According to the back integrated active device and the preparation method thereof, the size of the thermal shunt layer is not limited, 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 that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

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

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

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

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

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific 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 explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

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

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

Fig. 2 is a schematic cross-sectional view showing the fabrication process of the forward integrated device of fig. 1 using a heterobonding process, and in fig. 2 steps (a) to (d) are included, wherein a piece of SOI substrate is first selected, comprising 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) of fig. 2; then, a polysilicon material is grooved and filled 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 polysilicon thermal conductivity is greatly affected by the grain size, typically 15-60W/m/K, with a thermal conductivity much smaller than the metal 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, forming a thermal flow channel.

On the basis of a back-to-back process, the cladding material with heat conduction performance is filled on the front surface of the silicon waveguide structure, and the heat diverter 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 larger heat resistance and poor heat conduction effect of the heat diverter 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 laser is used as the active device layer in this embodiment.

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 at two sides of the cladding material layer 12, and is of a non-groove 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 in the embodiment, the metal heat conducting material is preferably copper as a metal material; in other embodiments, thermally conductive materials such as aluminum nitride, aluminum oxide, magnesium fluoride, polysilicon, and monocrystalline silicon may also be used.

Because the heat conduction performance of the metal material is far greater than that of the polysilicon material (the heat conduction coefficient of copper is 401W/m/K, the heat conduction coefficient of gold is 317W/m/K, and the heat conduction coefficient of polysilicon is 15-60W/m/K), the heat conduction performance of the heat shunt layer can be greatly improved by adopting the metal material as the heat conduction material layer 40 of the heat shunt layer. The heat conducting material layer 40 and the silicon layer 11 form a heat flow channel, and the heat conducting property of the silicon layer 11 and the heat conducting material layer 40 is far higher than that of silicon dioxide; therefore, the heat dissipation effect is greatly enhanced. Meanwhile, under the structure, the formed heat conduction channel is of 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.

A layer of cladding material 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, and the cladding material layer 12 is directly adjacent to the silicon substrate layer 1 without a silicon dioxide layer in between. The cladding material is a heat-conducting medium material, and the heat-conducting medium material can be at least one or any combination of silicon dioxide, silicon nitride, aluminum nitride and aluminum oxide, and the aluminum oxide material is preferably adopted in the embodiment. The cladding material layer 12 is made of a heat conducting medium material, so that the heat dissipation effect of the integrated active device can be further improved.

Example 2

Embodiment 2 provides a method for preparing a back-integrated active device, referring to (a) to (g) in fig. 4, which specifically includes the following steps:

step one: as shown in fig. 4 (a), a silicon waveguide structure is etched on the first surface 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 fig. 4 (c), a cladding material is deposited on the etched silicon layer 11 to form a cladding material layer 12, wherein the cladding material is a heat-conducting medium material, and may be at least one of silicon dioxide, silicon nitride, aluminum nitride, and aluminum oxide, or any combination thereof, and in this embodiment, aluminum oxide is preferred.

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

Because the heat conduction performance of the metal material is far greater than that of the polysilicon material (the heat conduction coefficient of copper is 401W/m/K, the heat conduction coefficient of gold is 317W/m/K, and the heat conduction coefficient of polysilicon is 15-60W/m/K), the heat conduction performance of the heat shunt layer can be greatly improved by adopting the metal material as the heat conduction material layer 40 of the heat shunt.

Step four: the carrier wafer 1 is bonded to the surfaces of the heat conductive material layer 40 and the cladding material layer 12, and as shown in fig. 4 (d), the carrier wafer 1 is a silicon substrate layer 1, and contacts with the cladding material layer 12.

Step five: the silicon layer 13 and the silicon oxide 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 subsequent bonding process of the active device layer 10 is convenient to implement, and the bonding process difficulty of the active device layer 10 is reduced.

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

At this time, the heat flow channel is formed by the silicon layer 11 and the heat conductive material layer 40 forming the heat flow diverter layer, and the heat dissipation effect is greatly enhanced because the heat conductive property of the silicon layer 11 and the heat conductive material layer 40 is much higher than that of silicon dioxide. Meanwhile, under the structure, the formed heat conduction channel is of 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 is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.

Claims (10)

1. An integrated active device comprises a silicon substrate layer, a silicon waveguide structure and an active device layer; wherein the thermal shunt comprises a thermal shunt layer and a cladding material layer; the thermal shunt layer is positioned between the silicon substrate layer and the active device layer, is positioned outside the cladding material layer and is in contact with the cladding material layer, so that a heat flow channel is formed; the thermal shunt layer is made of a silicon layer and a heat conducting material layer, and the silicon layer is bonded with the active device layer; the silicon layer is a first surface silicon layer which is reserved after the silicon dioxide layer and the silicon layer of the second surface are removed from the SOI substrate, and a silicon waveguide structure is etched on the first surface silicon layer.

2. The integrated active device of claim 1, wherein the thermally conductive material layer in the thermal shunt layer is a metallic thermally conductive material or a non-metallic thermally conductive material.

3. The back-integrated active device of claim 2, wherein the metallic thermally conductive material is copper or gold.

4. The back-integrated 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 back-integrated active device of claim 1, wherein the layer of cladding material is directly adjacent to the layer of silicon substrate.

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

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

8. The integrated back-active device of claim 7, wherein the thermally conductive dielectric material is one or more of silicon dioxide, silicon nitride, aluminum oxide.

9. The preparation method of the back integrated active device is characterized by comprising the following steps of:

etching a silicon waveguide structure on a first surface 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 conducting material in the filling structure to form a heat conducting material layer; the thermally conductive material layer and the silicon layer form a thermal shunt layer;

bonding a carrier wafer on the surface of the thermal shunt layer, wherein the carrier wafer is a silicon substrate layer and is contacted 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 first silicon-on-insulator layer of the SOI substrate.

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

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