CN114267665A - Anti-irradiation reinforced structure based on air gaps and preparation method thereof - Google Patents

Abstract

The invention discloses an air-gap-based anti-irradiation reinforcing structure and a preparation method thereof, belonging to the field of preparation and anti-irradiation reinforcement of semiconductor devices. The air gap structure is positioned in a buried oxide layer of the SOI substrate; the isolation structure is positioned on the SOI substrate; the channel region is positioned on the SOI substrate and is isolated by the isolation structure; the insulating medium layer is positioned on the channel region; the grid is positioned on the insulating medium layer; the side wall structures are positioned at two sides of the grid and the insulating medium layer; the source and drain electrodes are on the SOI substrate and located on two sides of the channel region, and the grid and the insulating medium layer are isolated from the source and drain electrodes through the side wall structure. According to the invention, the air gap is introduced to replace the buried oxide layer below the device channel, and holes of the buried oxide layer are accumulated due to immune irradiation; the back gate effect of the substrate is immunized by removing the buried oxide layer, the formation of a parasitic channel is isolated, and the leakage current is effectively reduced.

Description

Anti-irradiation reinforced structure based on air gaps and preparation method thereof

Technical Field

The invention relates to the technical field of semiconductor device preparation and irradiation-resistant reinforcement, in particular to an air-gap-based irradiation-resistant reinforcement structure and a preparation method thereof.

Background

With the continuous development of aerospace industry, the requirement of the space irradiation environment on the irradiation resistance of devices is continuously improved, and new requirements on the single particle resistance and total dose resistance indexes of the devices are continuously provided. With the development of the process preparation technology, the selection of the processing scheme of the anti-radiation device becomes various, but the reasonable selection of the processing scheme still has many challenges, such as device compatibility, to meet the requirement of anti-radiation performance.

At present, the preparation of an anti-radiation device is mainly based on a bulk silicon or SOI substrate, wherein the bulk silicon or SOI substrate has better resistance to the total dose effect, but is obviously influenced by the single event effect; the latter can achieve single particle immunity, but the presence of a buried oxide layer makes it more susceptible to the total dose effect; the total dose effect can be inhibited to a certain extent by carrying out buried oxide layer reinforcement on a device based on an SOI substrate, but the method needs to carry out special design on ion implantation or substrate preparation process and has the problems of complex process or higher specificity.

Disclosure of Invention

The invention aims to provide an air-gap-based anti-radiation reinforced structure and a preparation method thereof, so as to realize a novel device structure with higher resistance to single event effect and total dose effect, and simultaneously reduce the preparation requirement of the device on a substrate.

In order to solve the technical problem, the invention provides an air-gap-based anti-irradiation reinforced structure, which comprises an SOI substrate, an air-gap structure, an isolation structure, a channel region, an insulating medium layer, a grid, a side wall structure and a source electrode and a drain electrode, wherein the SOI substrate is provided with a plurality of air-gap structures;

the air gap structure is positioned in a buried oxide layer of the SOI substrate; the isolation structure is positioned on the SOI substrate; the channel region is positioned on the SOI substrate and is isolated by the isolation structure;

the insulating medium layer is positioned on the channel region; the grid electrode is positioned on the insulating medium layer;

the side wall structures are positioned on two sides of the grid and the insulating medium layer; the source and drain electrodes are positioned on the SOI substrate and positioned on two sides of the channel region, and the grid electrode and the insulating medium layer are isolated from the source and drain electrodes through a side wall structure.

Optionally, the SOI substrate includes a top silicon layer and a buried oxide layer, where the top silicon layer has a thickness of 2 to 1000 nm, and the buried oxide layer has a thickness of 5 to 1000 nm.

Optionally, the air gap structure is formed by etching the top silicon layer of the SOI substrate and then performing isotropic etching.

Optionally, the isolation structure is formed by etching top silicon of the SOI substrate and then filling an insulating material, where the insulating material is SiO₂Nitrogen oxide, Al₂O₃Or Si₃N₄。

Optionally, the channel region is obtained by doping top silicon of the SOI substrate, the doping type is P-type or N-type, the doping element is phosphorus, boron, indium or arsenic, and the doping concentration is 0-1e²⁰/cm^-3。

Optionally, the insulating medium layer is SiO₂Nitrogen oxide, TiO₂、HfO₂、Si₃N₄、ZrO₂、Ta₂O₅Barium strontium titanate BST, lead zirconate titanate piezoelectric ceramics PZT or Al₂O₃One or a combination of a plurality of the above, and the thickness is 0.1-20 nm.

Optionally, the gate is polysilicon, tantalum, tungsten, tantalum nitride or titanium nitride, and the thickness is 2-000 nm.

Optionally, the side wall structure is SiO₂Or SiO₂/Si₃N₄/SiO₂The sandwich structure has a transverse thickness of 5-300 nm.

Optionally, the source and drain electrodes are obtained by self-aligned injection or epitaxy of top silicon of the SOI substrate (1), and the source and drain electrodes (8) are externally interconnected by silicide including titanium silicide, cobalt silicide, nickel silicide, and rubidium silicide.

The invention also provides a preparation method of the anti-irradiation reinforced structure based on the air gap, which comprises the following steps:

step 1: providing an SOI substrate, and opening a hole on top silicon of the SOI substrate by etching;

step 2: removing a portion of the buried oxide layer by isotropic etching via the opening;

and step 3: filling the opening with an insulating medium to form an air gap structure, and then carrying out chemical mechanical polishing or etching to remove the surface insulating medium layer to form an isolation structure;

and 4, step 4: carrying out ion implantation or diffusion on top silicon of the SOI substrate to form a channel region;

and 5: forming an insulating medium layer on the top silicon surface of the SOI substrate through deposition or oxidation;

step 6: depositing a grid electrode material on the insulating medium layer, and performing anisotropic etching to form a grid electrode;

and 7: depositing a side wall material and etching to form a side wall structure;

and 8: and performing source-drain self-aligned ion implantation or an epitaxial process on the top silicon of the SOI substrate to prepare a source-drain electrode and finish the structure preparation.

The invention has the following beneficial effects:

(1) an air gap is introduced to replace a buried oxide layer below a device channel, and holes of the buried oxide layer are accumulated due to immune irradiation; the back gate effect of the substrate is immunized by removing the buried oxide layer, the formation of a parasitic channel is isolated, and the leakage current is effectively reduced;

(2) the preparation of the air gap is realized through controllable isotropic corrosion, and the development cost is low by adopting the prior art;

(3) the structure is suitable for a fully-depleted SOI device and a partially-depleted SOI device, and has a certain application range.

Drawings

FIG. 1 is a schematic view of an air-gap-based irradiation-resistant reinforcing structure provided by the present invention;

FIG. 2 is a schematic structural view of an SOI substrate;

FIG. 3 is a schematic illustration of an opening in the top silicon of an SOI substrate by etching;

FIG. 4 is a schematic illustration of a partial removal of a buried oxide layer by isotropic etching;

fig. 5 is a schematic diagram of the air gap structure formed by filling the opening with an insulating medium.

Detailed Description

The following will further describe in detail an air-gap-based irradiation-resistant reinforcing structure and a method for manufacturing the same according to the present invention with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

The invention provides an anti-irradiation reinforced structure based on an air gap, which is structurally shown in figure 1 and comprises an SOI (silicon on insulator) substrate 1, an air gap structure 2, an isolation structure 3, a channel region 4, an insulating medium layer 5, a grid electrode 6, a side wall structure 7 and a source electrode and a drain electrode 8, wherein the side wall structure is provided with a plurality of side walls; the air gap structure 2 is positioned in a buried oxide layer of the SOI substrate 1; the isolation structure 3 is positioned on the SOI substrate 1; the channel region 4 is positioned on the SOI substrate 1 and is isolated by the isolation structure 3; the insulating medium layer 5 is positioned on the channel region 4; the grid electrode 6 is positioned on the insulating medium layer 5; the side wall structures 7 are positioned at two sides of the grid electrode 6 and the insulating medium layer 5; the source and drain electrodes 8 are located on the SOI substrate 1 and located on two sides of the channel region 4, and the grid 6 and the insulating medium layer 5 are isolated from the source and drain electrodes 8 through a side wall structure 7.

The thickness of the top silicon layer of the SOI substrate 1 is 2-1000 nanometers, and the thickness of the buried oxide layer is 5-1000 nanometers. The air gap structure 2 is formed by etching the top silicon layer of the SOI substrate 1 and then performing isotropic etching. The isolation structure 3 is formed by etching the top silicon of the SOI substrate 1 and then filling an insulating material, wherein the insulating material is SiO₂Nitrogen oxide, Al₂O₃Or Si₃N₄. The channel region 4 is obtained by doping the top silicon of the SOI substrate 1, the doping type is P type or N type, the doping element is phosphorus, boron, indium or arsenic, and the doping concentration is 0-1e²⁰/cm^-3. The insulating medium layer 5 is SiO₂Nitrogen oxide, TiO₂、HfO₂、Si₃N₄、ZrO₂、Ta₂O₅Barium strontium titanate BST, lead zirconate titanate piezoelectric ceramics PZT or Al₂O₃One or a combination of a plurality of the above, and the thickness is 0.1-20 nm. The gate 6 is polysilicon, tantalum, tungsten, tantalum nitride or titanium nitride, and has a thickness of 2-000 nm. The side wall structure 7 is SiO₂Or SiO₂/Si₃N₄/SiO₂The sandwich structure has a transverse thickness d of 5-300 nm. The source and drain electrodes 8 are obtained by self-aligned injection or epitaxy of the top silicon of the SOI substrate 1, and the source and drain electrodes 8 are interconnected externally by silicide including titanium silicide, cobalt silicide, nickel silicide, and rubidium silicide.

The air-gap-based anti-radiation reinforced structure is prepared by the following method:

as shown in fig. 2, an SOI substrate 1 is provided, said SOI substrate 1 comprising a top layer silicon 11 and a buried oxide layer 12,

as shown in fig. 3, an opening is made in the top silicon 11 of the SOI substrate 1 by etching;

as shown in fig. 4, part of the buried oxide layer 12 is removed by isotropic etching via the opening;

as shown in fig. 5, the openings are filled with insulating medium to form an air gap structure 2, and then the surface insulating medium layer is removed by chemical mechanical polishing or etching to form an isolation structure 3;

as shown in fig. 1, ion implantation or diffusion is performed on the top silicon of the SOI substrate to form a channel region 4; forming an insulating medium layer 5 on the top silicon surface of the SOI substrate through deposition or oxidation; depositing a grid material on the insulating medium layer 5, and performing anisotropic etching to form a grid 6; depositing a side wall material and etching to form a side wall structure 7; and performing source-drain self-aligned ion implantation or an epitaxial process on the top silicon of the SOI substrate 1 to prepare a source-drain electrode 8 and finish the structure preparation.

According to the invention, the air gap is introduced to replace the buried oxide layer below the device channel, and holes of the buried oxide layer are accumulated due to immune irradiation; the back gate effect of the substrate is immunized by removing the buried oxide layer, the formation of a parasitic channel is isolated, and the leakage current is effectively reduced; the preparation of the air gap is realized through controllable isotropic corrosion, and the development cost is low by adopting the prior art; the structure is suitable for a fully-depleted SOI device and a partially-depleted SOI device, and has a certain application range.

The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.

Claims (10)

1. An air-gap-based anti-radiation reinforced structure is characterized by comprising an SOI substrate (1), an air-gap structure (2), an isolation structure (3), a channel region (4), an insulating medium layer (5), a grid (6), a side wall structure (7) and a source drain electrode (8), wherein the side wall structure is provided with a plurality of air gaps;

the air gap structure (2) is positioned in a buried oxide layer of the SOI substrate (1); the isolation structure (3) is located on the SOI substrate (1); the channel region (4) is located on the SOI substrate (1) and is isolated by the isolation structure (3);

the insulating medium layer (5) is positioned on the channel region (4); the grid electrode (6) is positioned on the insulating medium layer (5);

the side wall structures (7) are positioned on two sides of the grid electrode (6) and the insulating medium layer (5); the source and drain electrodes (8) are arranged on the SOI substrate (1) and located on two sides of the channel region (4), and the grid electrode (6) and the insulating medium layer (5) are isolated from the source and drain electrodes (8) through a side wall structure (7).

2. The air-gap based radiation-resistant reinforcing structure according to claim 1, wherein the SOI substrate (1) comprises a top silicon (11) and a buried oxide layer (12), the top silicon (11) having a thickness of 2 to 1000 nm, the buried oxide layer (12) having a thickness of 5 to 1000 nm.

3. The airgap-based radiation-resistant reinforcing structure as claimed in claim 1, wherein the airgap structure (2) is formed by etching the top silicon of the SOI substrate (1) followed by an isotropic etch.

4. The air-gap-based irradiation-resistant reinforcement structure of claim 1, wherein the isolation structure (3) is formed by etching the top silicon of the SOI substrate (1) and then filling with an insulating material, the insulating material being SiO₂Nitrogen oxide, Al₂O₃Or Si₃N₄。

5. The air-gap-based irradiation-resistant reinforcing structure according to claim 4, wherein the channel region (4) is obtained by doping the top silicon of the SOI substrate (1), the doping type is P-type or N-type, the doping element is phosphorus, boron, indium or arsenic, and the doping concentration is 0-1e²⁰/cm^-3。

6. The air-gap based radiation-resistant reinforcing structure of claim 1, wherein the insulating dielectricThe layer (5) is SiO₂Nitrogen oxide, TiO₂、HfO₂、Si₃N₄、ZrO₂、Ta₂O₅Barium strontium titanate BST, lead zirconate titanate piezoelectric ceramics PZT and Al₂O₃One or a combination of a plurality of the above, and the thickness is 0.1-20 nm.

7. The air-gap-based irradiation-resistant reinforcing structure according to claim 1, wherein the gate (6) is polysilicon, tantalum, tungsten, tantalum nitride or titanium nitride and has a thickness of 2-000 nm.

8. The air-gap-based radiation-proof reinforcing structure of claim 1, wherein the side wall structures (7) are of SiO₂Or SiO₂/Si₃N₄/SiO₂The sandwich structure has a transverse thickness of 5-300 nm.

9. The air-gap-based irradiation-resistant reinforcement structure according to claim 1, wherein the source and drain electrodes (8) are obtained by self-aligned implantation or epitaxy of top silicon of the SOI substrate (1), and the source and drain electrodes (8) are externally interconnected by silicide including titanium silicide, cobalt silicide, nickel silicide, rubidium silicide.

10. A preparation method of an anti-irradiation reinforced structure based on an air gap is characterized by comprising the following steps:

step 1: providing an SOI substrate, and opening a hole on top silicon of the SOI substrate by etching;

step 2: removing a portion of the buried oxide layer by isotropic etching via the opening;

and step 3: filling the opening with an insulating medium to form an air gap structure, and then carrying out chemical mechanical polishing or etching to remove the surface insulating medium layer to form an isolation structure;

and 4, step 4: carrying out ion implantation or diffusion on top silicon of the SOI substrate to form a channel region;

and 5: forming an insulating medium layer on the top silicon surface of the SOI substrate through deposition or oxidation;

step 6: depositing a grid electrode material on the insulating medium layer, and performing anisotropic etching to form a grid electrode;

and 7: depositing a side wall material and etching to form a side wall structure;

and 8: and performing source-drain self-aligned ion implantation or an epitaxial process on the top silicon of the SOI substrate to prepare a source-drain electrode and finish the structure preparation.

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