CN111341663A - Method of forming a radio frequency device - Google Patents

Abstract

The invention provides a method for forming a radio frequency device, which comprises the steps of forming a first opening and a second opening in a semiconductor substrate; forming oxide layers in the first opening and the second opening respectively, wherein the surfaces of the oxide layers are lower than the surface of the semiconductor substrate; and forming a polysilicon layer on the oxide layer to form a source electrode and a drain electrode. That is, by forming the oxide layer between the semiconductor substrate and the polysilicon layer, the semiconductor substrate and the polysilicon layer are isolated by the oxide layer to form a barrier between the substrate and the polysilicon layer through the oxide layer, thereby reducing the parasitic capacitance between the polysilicon layer and the semiconductor substrate, that is, reducing the parasitic capacitance of the source and the drain. Furthermore, the parasitic capacitance of the radio frequency device is reduced, so that the performance of the radio frequency device is improved.

Description

Method of forming a radio frequency device

technical field

The present invention relates to the technical field of semiconductors, in particular to a method for forming a radio frequency device.

Background technique

RF switch device is a device used for signal switching in the field of communication. It has the advantages of simple structure, wide application range, low cost, low power consumption, easy installation, high reliability, etc. It can be widely used in carrier telephone switching, cable TV signal switch, cable TV signal switch and other fields. During its operation, some regions are in an on state, and some regions are in an off state. Radio frequency device is a kind of device that has a very good market. Especially with the wide application of communication technology, it will get more and more attention as a new type of power device. There are parasitic capacitances in radio frequency devices. Generally, low parasitic capacitances are required in radio frequency devices to meet the performance requirements of radio frequency devices. However, in the existing process of radio frequency device, there is a large parasitic capacitance in the formed radio frequency device, and the large parasitic capacitance will seriously affect the performance of the device, and the radio frequency device, as a power switching type processing device, if there is a large parasitic capacitance The parasitic capacitance will degrade the performance of the RF device, thereby affecting the processing capability.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for forming a radio frequency device, so as to solve the problem of large parasitic capacitance in the radio frequency device in the prior art.

In order to solve the above technical problems, the present invention provides a method for forming a radio frequency device, comprising:

provide semiconductor substrates;

forming a first opening and a second opening in the semiconductor substrate;

forming an oxide layer in the first opening and the second opening respectively, and the surface of the oxide layer is lower than the surface of the semiconductor substrate;

forming a polysilicon layer on the oxide layer to form source and drain electrodes; and,

A gate structure is formed on the semiconductor substrate between the source and the drain.

Optionally, in the method for forming a radio frequency device, the method for forming an oxide layer in the first opening and the second opening respectively includes:

forming a first oxide material layer in the first opening and the second opening, respectively;

grinding the first oxide material layer to form a second oxide material layer;

A partial thickness of the second oxide material layer is removed to form the oxide layer.

Optionally, in the method for forming a radio frequency device, a part of the thickness of the second oxide material layer is removed by a dry etch-back method to form the oxide layer.

Optionally, in the method for forming a radio frequency device, the oxide layer is a silicon oxide layer.

Optionally, in the method for forming a radio frequency device, the thickness of the oxide layer is 1000 angstroms-2000 angstroms.

Optionally, in the method for forming a radio frequency device, a dielectric layer is formed on the surface of the semiconductor substrate, and both the first opening and the second opening extend through the dielectric layer.

Optionally, in the method for forming a radio frequency device, the dielectric layer includes a silicon oxide layer and a silicon nitride layer on the silicon oxide layer.

Optionally, in the method for forming a radio frequency device, after forming a polysilicon layer on the oxide layer, the method for forming a radio frequency device further includes: removing the dielectric layer to expose the semiconductor substrate .

Optionally, in the method for forming a radio frequency device, in the step of forming a polysilicon layer on the oxide layer to form a source electrode and a drain electrode, the surface of the formed polysilicon layer is higher than the semiconductor liner. bottom surface.

Optionally, in the method for forming a radio frequency device, the polysilicon layer has a thickness of 100 angstroms to 500 angstroms.

In the method for forming a radio frequency device provided by the present invention, a first opening and a second opening are formed in a semiconductor substrate; an oxide layer is formed in the first opening and the second opening respectively, and the oxide layer is The surface is lower than the surface of the semiconductor substrate; a polysilicon layer is formed on the oxide layer to form source and drain electrodes. That is, by forming the oxide layer between the semiconductor substrate and the polysilicon layer, the semiconductor substrate and the polysilicon layer are isolated by the oxide layer, so that the substrate and the polysilicon layer are separated from each other. A barrier is formed therebetween, thereby reducing the parasitic capacitance between the polysilicon layer and the semiconductor substrate, thereby reducing the parasitic capacitance of the source electrode and the drain electrode. Further, since the source electrode and the drain electrode are formed by an oxide layer and a polysilicon layer, the thickness of the polysilicon layer can be controlled, thereby reducing the thickness of the polysilicon layer, thereby reducing the thickness of the polysilicon layer. The size of the section in the horizontal direction. The parasitic capacitance of the source electrode and the drain electrode is reduced, and further, low parasitic capacitance is formed, and the performance of the radio frequency device is improved.

Description of drawings

1 is a schematic flowchart of a method for forming a radio frequency device provided by a specific embodiment of the present invention;

2-7 are schematic diagrams of structures formed in a method for forming a radio frequency device provided by a specific implementation of the present invention;

Among them, the reference numerals are described as follows:

100-semiconductor substrate; 110-dielectric layer; 111-silicon oxide layer; 112-silicon nitride layer; 113-second oxide material layer; 120-oxide layer; 130-polysilicon layer; 140-gate structure; 150- side wall layer.

Detailed ways

The method for forming a radio frequency device proposed by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that, the accompanying drawings are all in a very simplified form and in inaccurate scales, and are only used to facilitate and clearly assist the purpose of explaining the embodiments of the present invention.

The core idea of the present application is to provide a method for forming a radio frequency device, by forming a first opening and a second opening in a semiconductor substrate; forming an oxide layer in the first opening and the second opening respectively, so that the The surface of the oxide layer is lower than the surface of the semiconductor substrate; a polysilicon layer is formed on the oxide layer to form a source electrode and a drain electrode. That is, by forming the oxide layer between the semiconductor substrate and the polysilicon layer, the semiconductor substrate and the polysilicon layer are isolated by the oxide layer, so that the substrate can be separated from the substrate by the oxide layer. A barrier is formed between the polysilicon layer and the polysilicon layer, thereby reducing the parasitic capacitance between the polysilicon layer and the semiconductor substrate, thereby reducing the parasitic capacitance of the source electrode and the drain electrode. Further, the cross-sectional size of the polysilicon layer in the horizontal direction is reduced by controlling the thickness of the polysilicon layer, so as to reduce the parasitic capacitance of the source electrode and the drain electrode, thereby solving the problem that the radio frequency device in the prior art has a large size. the parasitic capacitance problem.

Next, the present application will be further described with reference to specific embodiments.

Please refer to FIG. 1 , which is a schematic flowchart of a method for forming a radio frequency device according to an embodiment of the present invention. As shown in FIG. 1, the formation method of the radio frequency device includes:

Step S1: providing a semiconductor substrate;

Step S2: forming a first opening and a second opening in the semiconductor substrate;

Step S3: respectively forming an oxide layer in the first opening and the second opening, and the surface of the oxide layer is lower than the surface of the semiconductor substrate;

Step S4: forming a polysilicon layer on the oxide layer to form a source electrode and a drain electrode;

Step S5: forming a gate structure on the semiconductor substrate between the source electrode and the drain electrode.

Specifically, please refer to FIG. 2 to FIG. 7 , which are schematic structural diagrams formed in a method for forming a radio frequency device provided by a specific embodiment of the present invention. As shown in FIG. 2 , in step S1, a semiconductor substrate 100 is provided, and the material of the semiconductor substrate 100 may include but not limited to: Si (silicon), SiC (silicon carbon), SiGe (silicon germanium), SiGeC ( Carbon germanium silicon), Ge alloy, GeAs (arsenic germanium), InAs (indium arsenide) and InP (indium phosphide) one or more combinations thereof. A dielectric layer 110 is formed on the semiconductor substrate 100 . The dielectric layer 110 includes a silicon oxide layer 111 and a silicon nitride layer 112 on the silicon oxide layer 111 . The dielectric layer 110 can protect the semiconductor substrate 100 in subsequent processes.

As shown in FIG. 3 , in step S2 , a first opening and a second opening are formed in the semiconductor substrate 100 ; and both the first opening and the second opening extend through the dielectric layer 110 . Preferably, the depth of the opening may be 1000 angstroms to 5000 angstroms, so as to facilitate the filling of materials in the subsequent process and the formation of a material layer of a certain thickness in the opening in the subsequent process. The first opening and the second opening may be formed in the semiconductor substrate 100 by dry etching. The etching gas used in the dry etching process can be one or more combinations of chlorine, hydrogen bromide, boron trichloride and argon, but is not limited to this, and other gases can also be used to The oxide layer 120 is subjected to the dry etching.

As shown in FIG. 5, in step S3, an oxide layer 120 is formed in the first opening and the second opening respectively, and the surface of the oxide layer 120 is lower than the surface of the semiconductor substrate 100; specifically , the method for forming the oxide layer 120 in the first opening and the second opening respectively includes: forming a first oxide material layer in the first opening and the second opening respectively; as shown in FIG. 4 , The first oxide material layer is ground to form the second oxide material layer 113; the first oxide material layer can be ground by chemical mechanical polishing to form the second oxide material layer 113, so as to ensure The flatness of the subsequently formed layers. Then, as shown in FIG. 5 , a partial thickness of the second oxide material layer 113 is removed to form the oxide layer 120 . Preferably, a part of the thickness of the second oxide material layer may be removed by a dry etch-back method to form the oxide layer 120 . Preferably, the oxide layer 120 is a silicon oxide layer 111, and the thickness of the oxide layer 120 is 1000 angstroms-2000 angstroms. The semiconductor substrate 100 is isolated by the oxide layer 120 .

As shown in FIG. 6 , in step S4 , a polysilicon layer 130 is formed on the oxide layer 120 to form a source electrode and a drain electrode; the method for forming the polysilicon layer includes depositing a polysilicon material on the oxide layer 120 layer, and planarizing the polysilicon material layer. Specifically, chemical mechanical polishing may be used to planarize the polysilicon material layer to form the polysilicon layer 130 having a flat surface, thereby ensuring the flatness of the surface of the polysilicon layer 130 . And the surface of the polysilicon layer 130 is higher than the surface of the semiconductor substrate 100 .

Preferably, the thickness of the polysilicon layer 130 is 100 angstroms to 500 angstroms. Since the source electrode and the drain electrode are formed by the oxide layer 120 and the polysilicon layer 130 , the thickness of the polysilicon layer 130 is set to 100 angstroms to 500 angstroms by controlling the thickness of the polysilicon layer 130 Egypt. Therefore, the cross-sectional size of the polysilicon layer 130 in the horizontal direction is reduced, thereby reducing the parasitic capacitance of the source electrode and the drain electrode. Further, a smaller parasitic capacitance is formed to improve the performance of the device. Moreover, the thickness of the oxide layer 120 is greater than the thickness of the polysilicon layer 130 . Therefore, the semiconductor substrate 100 and the polysilicon layer 130 are isolated by the oxide layer 120, that is, a barrier is formed between the substrate and the polysilicon layer 130 by the oxide layer 120, so as to reduce the amount of The parasitic capacitance between the semiconductor substrate 100 and the polysilicon layer 130 is reduced, thereby reducing the parasitic capacitance of the source electrode and the drain electrode. Further, the parasitic capacitance in the radio frequency device is reduced, and the performance of the radio frequency device is improved.

In the embodiment of the present application, after the polysilicon layer is formed on the oxide layer, the method for forming the radio frequency device further includes: removing the dielectric layer 110 to expose the semiconductor substrate 100 .

As shown in FIG. 7 , in step S5 , a gate structure 140 is formed, and the gate structure 140 is located on the semiconductor substrate 100 between the source electrode and the drain electrode. The gate structure 140 may include a gate dielectric layer and a gate electrode on the gate dielectric layer. After the gate structure 140 is formed, the method for forming the radio frequency device further includes: forming spacer layers 150 on both sides of the gate structure 140 to protect the gate structure 140 through the spacer layers 150 . Preferably, the material of the spacer layer 150 may be one or more combinations of silicon oxide and silicon nitride.

To sum up, in the method for forming a radio frequency device provided by the present invention, by forming a first opening and a second opening in a semiconductor substrate; and forming an oxide layer in the first opening and the second opening respectively, The surface of the oxide layer is lower than the surface of the semiconductor substrate; a polysilicon layer is formed on the oxide layer to form a source electrode and a drain electrode. That is, by forming the oxide layer between the semiconductor substrate and the polysilicon layer, the semiconductor substrate and the polysilicon layer are isolated by the oxide layer, so that the substrate can be separated from the substrate by the oxide layer. A barrier is formed between the polysilicon layer and the polysilicon layer, thereby reducing the parasitic capacitance between the polysilicon layer and the semiconductor substrate, that is, reducing the parasitic capacitance of the source electrode and the drain electrode. Further, since the source electrode and the drain electrode are formed by an oxide layer and a polysilicon layer, the thickness of the polysilicon layer can be controlled, so that the thickness of the polysilicon layer can be reduced to reduce the polysilicon layer. The cross-sectional size of the layer in the horizontal direction. Therefore, the parasitic capacitance of the source electrode and the drain electrode is reduced, thereby forming a low parasitic capacitance and improving the performance of the radio frequency device.

The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes and modifications made by those of ordinary skill in the field of the present invention based on the above disclosure all belong to the protection scope of the claims.

Claims (10)

1. A method of forming a radio frequency device, comprising:

providing a semiconductor substrate;

forming a first opening and a second opening in the semiconductor substrate;

forming oxide layers in the first opening and the second opening respectively, wherein the surfaces of the oxide layers are lower than the surface of the semiconductor substrate;

forming a polysilicon layer on the oxide layer to form a source electrode and a drain electrode; and the number of the first and second groups,

and forming a gate structure, wherein the gate structure is positioned on the semiconductor substrate between the source electrode and the drain electrode.

2. The method of forming a radio frequency device according to claim 1, wherein the method of forming an oxide layer in each of the first opening and the second opening includes:

forming a first oxide material layer in the first opening and the second opening, respectively;

grinding the first oxide material layer to form a second oxide material layer;

and removing part of the thickness of the second oxide material layer to form the oxide layer.

3. The method for forming a radio frequency device according to claim 2, wherein the second oxide material layer is removed by a dry etching back method to form the oxide layer.

4. The method of claim 3, wherein the oxide layer is a silicon oxide layer.

5. The method of claim 1, wherein the oxide layer has a thickness of 1000 a to 5000 a.

6. The method of claim 1, wherein a dielectric layer is formed on the surface of the semiconductor substrate, and the first opening and the second opening both extend through the dielectric layer.

7. The method of claim 6, wherein the dielectric layer comprises a silicon oxide layer and a silicon nitride layer on the silicon oxide layer.

8. The method of forming a radio frequency device of claim 6, wherein after forming a polysilicon layer on the oxide layer, the method of forming a radio frequency device further comprises: and removing the dielectric layer to expose the semiconductor substrate.

9. The method of forming a radio frequency device according to claim 1, wherein in the step of forming a polysilicon layer on the oxide layer to form the source and the drain, a surface of the polysilicon layer is formed to be higher than a surface of the semiconductor substrate.

10. The method of forming a radio frequency device according to claim 1, wherein the polysilicon layer has a thickness of 100 a to 500 a.

Images