CN111785678A - Semiconductor device and method of making the same - Google Patents

Abstract

A semiconductor device and a preparation method thereof, wherein the preparation method of the semiconductor device comprises the steps of: providing a silicon-on-insulator wafer, the silicon-on-insulator wafer including a top layer silicon; forming a plurality of silicon photons in the top layer silicon The multiple silicon optical devices include lasers; the top layer silicon in the region where the lasers are located is thickened to meet the thickness requirement of the top layer silicon due to the mode matching effect.

Description

Semiconductor device and method of making the same

technical field

The invention relates to the field of semiconductor preparation, in particular to a semiconductor device and a preparation method thereof.

Background technique

The silicon photonics process on a silicon-on-insulator wafer itself has a relatively complete set of optical components, including various passive devices, electro-optic modulators, and photodetectors. However, as an indirect bandgap material, silicon cannot directly emit light, which makes the integration of silicon-based light sources one of the important challenges for the development of silicon-based optoelectronic technology.

In the prior art, lasers are often fabricated using a silicon-on-insulator wafer photonics process. However, when a silicon-on-insulator wafer is used to manufacture the laser, a higher manufacturing cost is required, which is not conducive to the promotion of the laser.

SUMMARY OF THE INVENTION

The invention provides a semiconductor device and a preparation method thereof, which can reduce the preparation cost of the laser.

In order to solve the above problems, a semiconductor device is also provided below, comprising: a silicon-on-insulator wafer; a silicon-optical device formed on the top layer of the silicon-on-insulator wafer, the silicon-optical device comprising a laser; a thickened region , which is formed on the upper surface of the laser to thicken the laser so as to achieve the thickness requirement of the top layer silicon for the mode matching effect.

Optionally, the method further includes: a protective layer covering the silicon optical device and the thickened region.

Optionally, the protective layer includes a silicon dioxide layer.

Optionally, the thickness of the thickened region is at least 180 nm.

Optionally, the thickened region includes at least one of a polysilicon thickened region and an amorphous silicon thickened region.

In order to solve the above problems, a method for fabricating a semiconductor device is also provided below, including the following steps: providing a silicon-on-insulator wafer, the silicon-on-insulator wafer includes a top layer silicon; forming a plurality of silicon photons in the top layer silicon The multiple silicon optical devices include lasers; the top layer silicon in the region where the lasers are located is thickened, so as to thicken the lasers so as to meet the thickness requirement of the top layer silicon for the mode matching effect.

Optionally, before thickening the top layer silicon in the region where the laser is located, the method further includes forming a dielectric layer covering the upper surfaces of the plurality of silicon optical devices.

Optionally, before thickening the top layer silicon in the region where the laser is located, a step of removing the dielectric layer corresponding to the region to be thickened is further included.

Optionally, the dielectric layer includes a silicon dioxide layer covering the surfaces of the multiple silicon optical devices, and before thickening the top silicon in the region where the laser is located, the silicon dioxide layer corresponding to the region to be thickened is removed.

Optionally, after thickening the top layer of silicon in the region where the laser is located, secondary etching is performed on the surface of the thickened region.

Optionally, the multiple silicon optical devices further include one or more of a modulator and a waveguide.

Optionally, the laser includes a laser waveguide and a laser grating.

Optionally, the step of thickening the top layer silicon is to use polysilicon or amorphous silicon material for thickening.

Optionally, by at least one of chemical vapor deposition, physical vapor deposition and atomic layer deposition, polysilicon or amorphous silicon material is deposited on the top layer of silicon in the region where the laser is located, so as to achieve thickening.

Optionally, after the secondary etching is performed on the surface of the thickened region, the following step is further included: forming a protective layer covering the silicon optical device.

In the semiconductor device and the manufacturing method thereof of the present invention, the top layer of silicon in the region where the laser is located is thickened, so that the laser can be prepared by using a thin layer of top layer silicon without the need to specially prepare a thicker layer of top layer silicon. The silicon-on-insulator wafer reduces the difficulty of preparing the silicon-on-insulator wafer and reduces the manufacturing cost of the laser. In addition, the preparation method can also reduce the etching times of other silicon optical devices except the laser in the process of laser preparation, ensure the surface smoothness of other silicon optical devices, and prevent the rough surface of other silicon optical devices from causing transmission loss.

Description of drawings

FIG. 1 is a schematic flow chart of steps of a method for fabricating a semiconductor device according to an embodiment of the present invention.

FIG. 2 to FIG. 8 are schematic structural diagrams corresponding to each step of the manufacturing method of the semiconductor device in one embodiment.

Detailed ways

The study found that the reason for the higher fabrication cost when using a silicon-on-insulator wafer to fabricate a laser is that the silicon optical device used in the laser has a large thickness, usually around 400nm, to achieve the effect of mode matching. The thickness of the top layer of the silicon-on-insulator wafer is usually around 200 nm, so an additional silicon-on-insulator wafer needs to be prepared to prepare the laser, which increases the production cost required for preparing the laser.

Moreover, the manufacturing difficulty of silicon-on-insulator wafers will increase with the increase of the thickness of the top layer silicon. Therefore, when preparing silicon photonics devices for laser-related devices, the increase in the thickness of the top layer silicon will lead to an increase in the difficulty of production, resulting in The decline in production yield, which further leads to an increase in the cost of laser production.

A semiconductor device and a preparation method thereof are proposed below, and the semiconductor device and its preparation method are further explained and elaborated with reference to the drawings.

Please refer to FIGS. 1 to 8 , wherein FIG. 1 is a schematic flow chart of the steps of a method for manufacturing a semiconductor device in an embodiment of the present invention, and FIGS. 2 to 8 are schematic diagrams of the semiconductor device in an embodiment of the present invention. Each step of the preparation method corresponds to a schematic diagram of the structure formed.

In this specific embodiment, a semiconductor device is provided, comprising: a silicon-on-insulator wafer 100; a silicon-optical device formed on the top layer silicon 101 of the silicon-on-insulator wafer 100 (the silicon-optical device includes reference numeral 104 , 105, and 106), the silicon optical device includes a laser 106; a thickened region 109 is formed on the upper surface of the laser 106 to thicken the laser 106, so that the mode matching effect is achieved for the Thickness requirements of the top layer silicon 101.

In this specific implementation manner, since the top layer silicon 101 in the region where the laser 106 is located is thickened by the thickened region 109, the laser 106 can be prepared by using a thin layer of the top layer silicon 101, and there is no need to prepare specially The silicon-on-insulator wafer 100 with the thick top layer silicon 101 can effectively reduce the manufacturing cost required for laser manufacturing using the semiconductor device, and reduce the cost of manufacturing the silicon-on-insulator wafer 100 for laser.

In fact, in addition to the laser 106, other active devices such as modulators and detectors also have high thickness requirements for the top layer silicon 101. Therefore, in some specific embodiments, the silicon optical device also includes modulation The thickening region is also formed to the upper surface of the modulator, the detector, etc., so as to realize the thickening of the modulator, the detector, and the like.

In a specific implementation manner, the top layer silicon 101 of the silicon-on-insulator wafer 100 is a layer of monocrystalline silicon, which is used to form a silicon optical device, the middle layer is a layer of insulating silicon dioxide, and the supporting substrate 103 is a layer of silicon dioxide. It is used to provide mechanical support for the top layer silicon 101 and the middle layer. In other specific embodiments, the insulating layer 102 of other materials may also be provided.

In a specific embodiment, the method further includes: a protective layer 110 covering the silicon optical device and the thickened region. In a specific embodiment, the protective layer 110 includes a silicon dioxide layer. In fact, the specific material of the protective layer 110 can also be selected as required.

In a specific embodiment, the thickened region has a thickness of at least 180 nm. This is because the thickness of the top layer of a general silicon-on-insulator wafer is about 220nm, while the thickness of a general laser needs to be above 400nm. When a general silicon-on-insulator wafer is used to prepare a silicon optical device including a laser, the thickened area of the single-crystal silicon material needs to be above 180 nm to achieve the effect of mode matching.

In a specific embodiment, the thickened region includes at least one of a thickened region of polysilicon and a thickened region of amorphous silicon. It should be noted that the polycrystalline silicon material or amorphous silicon material used here needs to match the refractive index of single crystal silicon, and the polycrystalline silicon material or amorphous silicon material used here can be deposited by chemical vapor deposition, physical vapor deposition or atomic layer deposition. at least one of them.

In this specific embodiment, a method for preparing a semiconductor device is provided, including the following steps: S11 providing a silicon-on-insulator wafer 100, the silicon-on-insulator wafer 100 including a top layer silicon 101, please refer to FIG. 2 here; S12 forming a plurality of silicon photonics devices in the top layer silicon 101 (the silicon photonics devices include all the components shown by reference numerals 104, 105, 106), the silicon photonics devices including a laser 106, please refer to FIG. 3 here; S13 is to thicken the top layer silicon 101 in the region where the laser is located, so as to meet the thickness requirement of the top layer silicon 101 for the mode matching effect, please refer to FIG. 7 here.

In this specific embodiment, in the preparation method of the semiconductor device, the top layer silicon 101 in the region where the laser 106 is located is thickened, and on the premise that the laser 106 can achieve the effect of mode matching, the The laser 106 can be fabricated by using a thin top layer silicon 101 without specially preparing a silicon-on-insulator wafer 100 with a thicker top layer silicon 101, which can effectively reduce the fabrication cost required when using the semiconductor device to fabricate a laser , and reduce the cost of fabricating the silicon-on-insulator wafer 100 for the laser.

Moreover, the study found that the smoothness of the surface of the silicon optical device greatly affects the light transmission efficiency of the silicon optical device. A surface roughness of 2 nm for a silicon photonics device will result in a waveguide transmission loss of 2 to 3 dB/cm. In this specific embodiment, since a silicon-on-insulator wafer 100 with a thinner top layer silicon 101 is used to fabricate the laser, when the laser 106 is realized by etching, it is possible to reduce the impact on other silicon optical devices other than the laser 106. The number of etchings ensures the surface smoothness of other silicon optical devices and prevents transmission loss caused by the rough surface of other silicon optical devices.

In a more preferred embodiment, before thickening the top layer silicon 101 in the region where the laser is located, it further includes forming a dielectric layer 107 covering the upper surfaces of the plurality of silicon optical devices. The dielectric layer 107 can play the role of protecting other silicon photonics devices, preventing the material layer used to cover the upper surface of other silicon photonics devices when the silicon photonics devices are thickened, so that when forming other silicon photonics devices, the layer of material used is also covered. In the process, multiple etchings are still needed, which affects the smoothness of the surface of other silicon optical devices.

Referring to FIG. 2 , the top layer silicon 101 and the supporting substrate 103 of the silicon-on-insulator wafer 100 are tightly bonded, and an insulating layer 102 is formed in the middle to separate the top layer silicon 101 and the supporting substrate 103 . The insulating layer 102 can realize full dielectric isolation between the top layer silicon 101 and the supporting substrate 103, so as to reduce parasitic capacitance and improve the running speed. Moreover, since the parasitic capacitance is reduced, the leakage current can also be reduced, and the power consumption of the device implemented on the top layer silicon 101 can be reduced. In addition, using the silicon-on-insulator wafer 100 to realize the silicon photonics process can also eliminate the latch-up effect, suppress the interference of the pulse current in the support substrate 103 to the top layer silicon 101, reduce soft errors, etc., and can also be compatible with existing Some silicon processes are compatible.

In a specific implementation manner, the top layer silicon 101 of the silicon-on-insulator wafer 100 is a layer of monocrystalline silicon, which is used to form a silicon optical device, the middle layer is a layer of insulating silicon dioxide, and the supporting substrate 103 is a layer of silicon dioxide. It is used to provide mechanical support for the top layer silicon 101 and the middle layer. In other specific embodiments, the insulating layer 102 of other materials may also be provided.

In a specific embodiment, the thickness of the top layer silicon 101 is less than 230 nm. This can effectively reduce the difficulty of preparing the silicon-on-insulator wafer 100 . In fact, the thickness of the top layer silicon 101 of the silicon-on-insulator wafer 100 conventionally produced in the prior art is 220 nm, which meets this requirement. Therefore, the silicon-on-insulator wafer 100 commonly used in the prior art can be directly used to prepare the semiconductor device without specially preparing some silicon-on-insulator wafers 100 with extra thick top layer silicon 101 .

In this specific embodiment, after thickening, the laser 106 can reach the thickness required for the mode matching effect, and the laser has better transmission effect when the laser is transmitted in the laser 106, such as lower transmission loss. Generally speaking, to achieve mode matching, a laser needs a thickness of about 400 nm. The thickness mentioned here refers to the thickness in the direction perpendicular to the surface of the top layer silicon 101 . Please refer to FIG. 2 and FIG. 3. In FIG. 2, the thickness of the top layer silicon 101 is d1. Before thickening, the thickness of the laser 106 is d2, and d2 is less than or equal to d1. After thickening, the thickness of the laser 106 can meet the mode matching requirements of the laser 106 .

In this specific embodiment, since the top layer silicon 101 in the region where the laser is located is thickened, there is no need to use a silicon-on-insulator wafer 100 with a thicker top layer silicon 101 when preparing the laser, and there is no need for such a The top layer silicon 101 of the silicon-on-insulator wafer 100 with the thicker top layer silicon 101 is etched multiple times to realize the preparation of the laser, so the smoothness of the surface of other silicon optical devices with smaller thickness can be ensured.

In this specific implementation manner, before the step of thickening the top layer silicon 101, the step of removing the dielectric layer 107 corresponding to the region to be thickened is further included. This is because the shape of the structure formed after thickening is likely to be inconsistent with the shape actually required by the laser.

In a specific implementation manner, after thickening the top layer silicon 101 in the region where the laser is located, secondary etching is performed on the surface of the thickened region 109 .

In a specific embodiment, the step of secondary etching and forming includes at least one of dry etching or wet etching.

In a specific implementation manner, after the secondary etching is performed on the surface of the thickened region 109, the following step is further included: forming a protective layer covering the silicon photonics device. See Figure 8 here. In the specific embodiment shown in FIG. 8 , the silicon dioxide layer is used as the protective layer 110 . In this way, the protective layer 110 is made of the same material as the dielectric layer 107 , and light passes between the protective layer 110 and the dielectric layer 110 . When propagating between layers 107, no refraction occurs.

In a specific implementation manner, the dielectric layer 107 includes a silicon dioxide layer covering the surfaces of the plurality of silicon optical devices, and before thickening the top layer silicon 101 in the region where the laser is located, remove the region that needs to be thickened 109 the corresponding silicon dioxide layer. In a specific embodiment, the silicon dioxide layer corresponding to the region to be thickened is removed by etching.

Specifically, when the silicon dioxide layer is removed by etching, a mask layer is first formed on the upper surface of the silicon dioxide layer, and the mask layer is patterned so that the area that needs to be thickened is exposed to the mask. After that, dry or wet etching can be performed on the silicon dioxide layer in the region until the upper surface of the region that needs to be thickened is exposed.

In some other specific implementation manners, other materials may also be provided as the dielectric layer 107 as required.

Please refer to FIG. 4 and FIG. 5 . In FIG. 4 , the situation in which the upper surfaces of the plurality of silicon optical devices are covered with a dielectric layer 107 is depicted. The dielectric layer 107 covers the upper surfaces of all the silicon optical devices, which can effectively protect the silicon optical devices. In FIG. 5 , the situation of removing the silicon dioxide layer corresponding to the thickened region 109 is described. Here, a through hole is opened on the upper surface of the silicon dioxide layer, and the upper surface of the laser is exposed to the through hole. The size of the via is related to the size of the area where the laser needs to be thickened.

Please refer to FIG. 6 to FIG. 7 , wherein FIG. 6 depicts a schematic structural diagram of a device formed after thickening the top layer silicon 101 in the region corresponding to the laser. FIG. 7 depicts a schematic structural diagram of a device formed by performing secondary etching on the thickened structure.

In a specific embodiment, the laser includes a laser waveguide and a laser grating. In fact, the laser may also comprise other structures.

In a specific embodiment, the laser waveguide and the laser grating have the same thickness in a direction perpendicular to the surface of the top layer silicon 101 , and in some other specific embodiments, the laser waveguide and the laser grating are perpendicular to the top layer. The thickness in the surface direction of the silicon 101 is different. This can be set according to actual needs.

In a specific implementation manner, the step of thickening the top layer silicon 101 is to use polysilicon or amorphous silicon material for thickening. It should be noted that the polycrystalline silicon material or amorphous silicon material used here needs to match the refractive index of single crystal silicon. In fact, different materials can also be used to thicken the top layer silicon 101 according to specific requirements.

In a specific embodiment, polysilicon or amorphous silicon material is deposited on the top layer silicon 101 in the region where the laser is located by at least one of chemical vapor deposition, physical vapor deposition, and atomic layer deposition, so as to achieve thickening.

In a specific embodiment, the plurality of silicon optical devices further include one or more of a modulator and a waveguide. The thickness of other silicon optical devices other than the laser in the direction perpendicular to the surface of the top layer silicon 101 is less than or equal to the thickness of the top layer silicon 101 . Please see Figure 2. In the specific embodiment shown in FIG. 2 , the thicknesses of the modulator 105 and the waveguide 104 are less than 220 nm, which is compatible with the thickness of the conventional top layer silicon 101 with a thickness of 220 nm, so there is no need for additional adjustments to the modulator 105 and the thickness of the top layer silicon 101 . The area corresponding to the waveguide 104 is thickened.

Please see the following examples for steps in forming a silicon-based III-V laser using the semiconductor device in this embodiment. The semiconductor devices formed in this embodiment can be used to fabricate III-V lasers.

As traditional optoelectronic application materials, III-V compounds have excellent luminescence properties. However, the lattice constant mismatch between III-V materials and silicon is large, and the III-V materials obtained by direct epitaxial growth on silicon have many defects and poor quality, which is difficult to prepare. A high-performance laser that meets the requirements. Therefore, the mainstream method in the market is still to realize the integration of III-V lasers and silicon wafers through hetero-bonding and off-chip packaging methods. However, off-chip light source packaging requires high-precision alignment coupling. In contrast, hetero-bonding integration can effectively reduce packaging costs, improve yield and reliability, and has been the focus of research and development by companies in recent years. Among them, CEA-Leti is the representative of the back-side hetero-bonding integration method of III-V lasers, which is well compatible with the original silicon photonics front and rear processes.

In this embodiment, the following steps are included:

(1) using the preparation method in the specific embodiment of the present invention to complete the preparation of the silicon photonics device on the silicon-on-insulator wafer 100;

(2) Directly bonding the silicon-on-insulator wafer 100 prepared for the silicon-optical device to the front side of a silicon wafer carrier wafer, and thinning the backside of the silicon-on-insulator wafer 100 to the top layer where the silicon-optical device is located Silicon 101;

(3) directly bonding the backside of the thinned silicon-on-insulator wafer 100 with the III-V material epitaxial wafer, and patterning the III-V material epitaxial wafer to form a laser electrode;

(4) Connecting the silicon optical device on the silicon-on-insulator wafer 100 by means of backside through holes.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can use the methods and technical contents disclosed above to improve the present invention without departing from the spirit and scope of the present invention. The technical solutions are subject to possible changes and modifications. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention belong to the technical solutions of the present invention. protected range.

Claims (15)

1. a semiconductor device, is characterized in that, comprises: silicon-on-insulator wafers; a silicon-optical device formed on the top layer of silicon of the silicon-on-insulator wafer, the silicon-optical device comprising a laser; A thickened region is formed on the upper surface of the laser to thicken the laser so as to meet the thickness requirement of the top layer silicon for the mode matching effect. 2. The semiconductor device of claim 1, further comprising: A protective layer covering the silicon optical device and the thickened region. 3. The semiconductor device of claim 2, wherein the protective layer comprises a silicon dioxide layer. 4. The semiconductor device of claim 1, wherein the thickened region has a thickness of at least 180 nm. 5. The semiconductor device of claim 1, wherein the thickened region comprises at least one of a thickened region of polysilicon and a thickened region of amorphous silicon. 6. a preparation method of a semiconductor device, is characterized in that, comprises the following steps: providing a silicon-on-insulator wafer, the silicon-on-insulator wafer including a top layer silicon; forming a plurality of silicon photonics devices in the top layer silicon, the plurality of silicon photonics devices comprising lasers; The top layer silicon in the region where the laser is located is thickened, so as to thicken the laser so as to meet the thickness requirement of the top layer silicon for the mode matching effect. 7 . The method for manufacturing a semiconductor device according to claim 6 , wherein before thickening the top layer silicon in the region where the laser is located, it further comprises forming a dielectric layer covering the upper surfaces of the plurality of silicon optical devices. 8 . 8 . The method for manufacturing a semiconductor device according to claim 6 , wherein before thickening the top layer silicon in the region where the laser is located, it further comprises the step of removing the dielectric layer corresponding to the region to be thickened. 9 . 9 . The method for manufacturing a semiconductor device according to claim 7 , wherein the dielectric layer comprises a silicon dioxide layer covering the surfaces of the plurality of silicon optical devices, and the top layer of the region where the laser is thickened is located. 10 . Before silicon, remove the silicon dioxide layer corresponding to the area to be thickened. 10 . The method for manufacturing a semiconductor device according to claim 6 , wherein after thickening the top layer silicon in the region where the laser is located, secondary etching is performed on the surface of the thickened region. 11 . 11. The method for fabricating a semiconductor device according to claim 6, wherein the plurality of silicon optical devices further comprise one or more of a modulator and a waveguide. 12 . The method for manufacturing a semiconductor device according to claim 6 , wherein the laser comprises a laser waveguide and a laser grating. 13 . 13 . The method for manufacturing a semiconductor device according to claim 6 , wherein the step of thickening the top layer silicon is to use polysilicon or amorphous silicon material for thickening. 14 . 14. The method for manufacturing a semiconductor device according to claim 13, characterized in that, by at least one of chemical vapor deposition, physical vapor deposition and atomic layer deposition, polysilicon or polysilicon is deposited on the top layer of silicon in the region where the laser is located. Amorphous silicon material to achieve thickening. 15. The method for preparing a semiconductor device according to claim 10, wherein after the secondary etching is performed on the surface of the thickened region, the method further comprises the following steps: A protective layer covering the silicon optical device is formed.

Images