Multi-layered polysilicon and oxygen-doped polysilicon design for RF SOI trap-rich poly layer

Patent metadata

Field	Value
Publication number	US-12074036-B2
Application number	US-202117519765-A
Country	US
Kind code	B2
Filing date	Nov 5, 2021
Priority date	Sep 11, 2019
Publication date	Aug 27, 2024
Grant date	Aug 27, 2024

Abstract

In some embodiments, the present disclosure relates to a high-resistivity silicon-on-insulator (SOI) substrate, including a first polysilicon layer arranged over a semiconductor substrate. A second polysilicon layer is arranged over the first polysilicon layer, and a third polysilicon layer is arranged over the second polysilicon layer. An active semiconductor layer over an insulator layer may be arranged over the third polysilicon layer. The second polysilicon layer has an elevated concentration of oxygen compared to the first and third polysilicon layers.

First claim

What is claimed is:

1. A method comprising:
depositing a first layer of polysilicon over a substrate at a first temperature in a chamber;
introducing oxygen into the chamber to dope a top surface of the first layer of polysilicon at a second temperature less than the first temperature to form a first layer of oxygen-doped polysilicon over the first layer of polysilicon;
depositing a second layer of polysilicon over the first layer of oxygen-doped polysilicon at the first temperature in the chamber;
introducing oxygen into the chamber to dope a top surface of the second layer of polysilicon at the second temperature to form a second layer of oxygen-doped polysilicon over the second layer of polysilicon; and
depositing a capping layer of polysilicon over the second layer of oxygen-doped polysilicon in the chamber at the first temperature;
wherein the first layer of oxygen-doped polysilicon comprises polycrystalline grains and a concentration of oxygen between 10%-20%, wherein the introducing of oxygen into the chamber to dope the top surface of the first layer of polysilicon comprises flowing a premixed gas of helium and oxygen into the chamber at a flow rate of 500 standard cubic centimeters per minute (SCCM), wherein the premixed gas has 0.1-1 atomic percent oxygen, and wherein the first and second layers of polysilicon, the first and second layers of oxygen-doped polysilicon, and the capping layer partially form a semiconductor-on-insulator (SOI) substrate.

2. The method of claim 1 , wherein the depositing of the first layer of polysilicon and the second layer of polysilicon are each conducted over a first time period, and wherein the depositing of the capping layer is conducted over a second time period that is greater than the first time period.

3. The method of claim 1 , wherein the chamber is an epi chamber, and wherein the method further comprises cleaning the chamber with hydrogen gas after the second layer of oxygen-doped polysilicon is formed and before the deposition of the capping layer.

4. The method of claim 3 , further comprising:
forming a native oxide layer over the substrate before forming the first layer of polysilicon.

5. The method according to claim 1 , wherein the second temperature is 550-750 degrees Celsius.

6. The method according to claim 4 , wherein the first and second layers of polysilicon are deposited using a first precursor gas of dichlorosilane (DCS) for 20 seconds at the first temperature, which is 850 degrees Celsius, wherein the first and second layers of oxygen-doped polysilicon are deposited using the premixed gas for 20 seconds at the second temperature, which is 650 degrees Celsius, wherein the capping layer of polysilicon is deposited using another precursor gas of DCS for 20 minutes at the first temperature, and wherein a silicon dioxide layer overlies and directly contacts the capping layer and further partially forms the SOI substrate.

7. The method of claim 6 , wherein an average grain size of polycrystalline grains in the first layer of polysilicon is substantially uniform from a bottom surface of the first layer of polysilicon to the top surface of the first layer of polysilicon.

8. The method of claim 1 , wherein the introducing of oxygen into the chamber to dope the top surface of the first layer of polysilicon further comprises flowing hydrogen gas into the chamber at a flow rate of 50 standard liters per minute, and wherein the flowing of the premixed gas and the flowing of the hydrogen gas yields 10 parts per million (PPM) oxygen, relative to hydrogen, within the chamber.

9. A method comprising:
forming a first layer of polysilicon over a semiconductor substrate;
forming a first layer of oxygen-doped polysilicon over and completely covering the first layer of polysilicon;
forming a second layer of polysilicon over and completely covering the first layer of oxygen-doped polysilicon;
forming a second layer of oxygen-doped polysilicon over and completely covering the second layer of polysilicon;
forming a cap polysilicon layer over and completely covering the second layer of oxygen-doped polysilicon;
forming an insulator layer over the cap polysilicon layer; and
forming an active semiconductor layer over the insulator layer;
wherein the first and second layers of oxygen-doped polysilicon each have polycrystalline grains and a higher number of dangling bonds than each of the first layer of polysilicon, the second layer of polysilicon, and the cap polysilicon layer, and wherein the first layer of oxygen-doped polysilicon is poly-crystalline continuously from the first layer of polysilicon to the second layer of polysilicon, wherein the forming of the first layer of oxygen-doped polysilicon comprises flowing a premixed gas of helium and oxygen into an epi chamber at a flow rate of 500 standard cubic centimeters per minute (SCCM), wherein the premixed gas has 0.1-1 atomic percent oxygen, and wherein the first layer of oxygen-doped polysilicon comprises a concentration of oxygen between 10%-20%.

10. The method of claim 9 , wherein the first and second layers of oxygen-doped polysilicon each have a higher concentration of oxygen and a smaller grain size than each of the first layer of polysilicon, the second layer of polysilicon, and the cap polysilicon layer.

11. The method of claim 9 , wherein the first layer of oxygen-doped polysilicon and the second layer of oxygen-doped polysilicon are formed at a lower temperature than the formation of the cap polysilicon layer, the first layer of polysilicon, and the second layer of polysilicon.

12. The method of claim 9 , wherein the first layer of oxygen-doped polysilicon is completely crystalline, wherein a top surface of the first layer of polysilicon is in direct contact with a bottom surface of the first layer of oxygen-doped polysilicon, and wherein a top surface of the first layer of oxygen-doped polysilicon is in direct contact with a bottom surface of the second layer of polysilicon.

13. The method of claim 9 , wherein the forming of the first layer of oxygen-doped polysilicon comprises flowing hydrogen gas into the epi chamber at a flow rate of 50 standard liters per minute, wherein the flowing of the premixed gas and the flowing of the hydrogen gas yields 10 parts per million (PPM) oxygen, relative to hydrogen, within the epi chamber.

14. The method of claim 13 , further comprising:
forming a native oxide layer overlying and directly contacting the semiconductor substrate, wherein the native oxide layer is formed with a bottom surface and a top surface that both have planar profiles, wherein the first layer of polysilicon is formed overlying and directly contacting the native oxide layer, wherein the first layer of polysilicon is formed with a bottom surface that has a planar profile and a top surface that has a wavy profile, and wherein the cap polysilicon layer is formed with a bottom surface that has a wavy profile.

15. A method of forming a high-resistivity silicon-on-insulator (SOI) substrate, the method comprising:
depositing a first layer of polysilicon over a semiconductor substrate in a chamber;
forming a first layer of oxygen-doped polysilicon in the chamber;
depositing a second layer of polysilicon over the first layer of oxygen-doped polysilicon in the chamber;
forming a second layer of oxygen-doped polysilicon in the chamber; and
depositing a capping layer of polysilicon over the second layer of oxygen-doped polysilicon in the chamber,
wherein the first and second layers of oxygen-doped polysilicon comprise polycrystalline grains and have higher concentrations of oxygen compared to the first and

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Cheng Yu-Hung
• Wu Cheng-Ta
• Chiang Chen-Hao
• Kalnitsky Alexander
• Tu Yeur-Luen
• Chen Eugene

Classifications

• H10W10/181

  Semiconductor-on-insulator [SOI] isolation regions, e.g. buried oxide regions of SOI wafers · CPC title

• H10P90/1906

  Preparing SOI wafers · CPC title

• H10W44/20

  at high-frequency [HF] or radio frequency [RF] · CPC title

• H10P36/07 Primary

  of silicon-on-insulator structures · CPC title

• H10P90/1916

  with separation or delamination along an ion implanted layer, e.g. Smart-cut · CPC title