CN-121985746-A - Field oxide structure and forming method thereof

CN121985746ACN 121985746 ACN121985746 ACN 121985746ACN-121985746-A

Abstract

The invention discloses a field oxide structure and a forming method thereof, belonging to the technical field of semiconductors, wherein the forming method of the field oxide structure is used for preparing an LDMOS device and comprises the steps of providing a substrate, wherein a first conduction type drift region is formed in the substrate; coating a photoresist on the surface of the substrate, patterning the photoresist, forming an opening on the first conductive type drift region, performing at least one oxygen ion implantation on the first conductive type drift region through the opening to form an oxygen ion doped region, removing the photoresist, and performing annealing treatment on the oxygen ion doped region at a preset temperature to form an in-situ oxide with an arc-shaped cross-section bottom surface. Oxygen ions with controllable dosage are injected into the first conductive type drift region, high-temperature annealing is performed, in-situ oxide with arc edges is generated in the first conductive type drift region in situ, stress concentration is reduced, an electron migration path is improved, oxide is generated in situ by means of ion injection, damage caused by etching is avoided, and reliability of a device is enhanced.

Inventors

LUO PENGCHENG
HU LIBING
LI YECHAO
HUANG RENDE

Assignees

重庆芯联微电子有限公司

Dates

Publication Date: 20260505
Application Date: 20251219

Claims (10)

1. The forming method of the field oxide structure is characterized by comprising the following steps of: providing a substrate, wherein a first conductive type drift region is formed in the substrate; coating a photoresist on the surface of the substrate, patterning the photoresist, and forming an opening on the first conductivity type drift region; Performing at least one oxygen ion implantation on the first conductive type drift region through the opening to form an oxygen ion doped region; and removing the photoresistance, and carrying out annealing treatment on the oxygen ion doped region at a preset temperature to form the in-situ oxide with the bottom surface in an arc-shaped cross-section shape.
2. The method of claim 1, wherein a second conductivity type body region is further formed on one side of the first conductivity type drift region.
3. The method according to claim 2, wherein a gate structure is formed at an interface between the first conductivity type drift region and the second conductivity type body region after the oxygen ion doped region is annealed at a predetermined temperature.
4. The method of forming a field oxide structure of claim 3, wherein a drain region is formed in the first conductivity type drift region after the gate structure is formed.
5. The method of claim 4, wherein a source region is formed in the second conductivity type body region after the gate structure is formed, the in-situ oxide being located in the first conductivity type drift region between the source region and the drain region.
6. The method of claim 1, wherein the first conductivity type is N-type, the second conductivity type is P-type, or the first conductivity type is P-type, the second conductivity type is N-type.
7. A field oxide structure prepared by the method of forming a field oxide structure according to any one of claims 1-6, comprising: A substrate; a first conductivity type drift region in the substrate; and the in-situ oxide is positioned in the first conductive type drift region, and the bottom surface is in an arc-shaped cross-section shape.
8. The field oxide structure of claim 7, wherein one side of the first conductivity type drift region is further provided with a second conductivity type body region, and wherein an active region is further formed in the second conductivity type body region.
9. The field oxide structure of claim 8, wherein a drain region is further disposed in the first conductivity type drift region.
10. The field oxide structure of claim 9, wherein the in-situ oxide is located in the first conductivity type drift region between the source region and the drain region, and wherein a gate structure is further provided at an interface of the first conductivity type drift region and the second conductivity type body region.

Description

Field oxide structure and forming method thereof Technical Field The invention relates to the technical field of semiconductors, in particular to a field oxide structure and a forming method thereof. Background In a conventional LDMOS (Lateral Double Diffused MOSFET, lateral double-diffused metal oxide semiconductor field effect transistor) device, a field oxide structure is fabricated in a drift region by a photolithography-dry etching-Liner oxidation (Liner oxide: oxide generated by a thermal oxidation method for repairing etching damage) -HARP (HIGH ASPECT Ratio Process) Process to regulate and control an electric field, so as to improve the voltage-withstanding capability of the device. As shown in fig. 1 and 2, under the influence of such a field oxide structure, current does not flow through the surface, and thus the electric field at the surface of the device is greatly reduced. But this structure also brings problems: 1. Stress concentration at the corners of the field oxide structure generates defects, resulting in drift of electrical parameters. Meanwhile, high electric fields exist at corners, so that high-energy carriers are easy to enter the field oxide structure to form defects, and the reliability of the device is influenced. 2. The trapezoid-like field oxide structure prolongs the path of electron transfer, leads to an increase in specific on-resistance and reduces the efficiency of the device. 3. The damage caused by the field oxide dry etching stage will aggravate the degree of hot carrier injection, and significantly affect the performance of the device. 4. The process is complex and the cost is high. It should be noted that the information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. Disclosure of Invention The invention aims to provide a field oxide structure and a forming method thereof, which are used for solving the problem of stress concentration caused by a trapezoid-like field oxide structure. In order to solve the above technical problems, the present invention provides a method for forming a field oxide structure, for preparing an LDMOS device, including: providing a substrate, wherein a first conductive type drift region is formed in the substrate; coating a photoresist on the surface of the substrate, patterning the photoresist, and forming an opening on the first conductivity type drift region; Performing at least one oxygen ion implantation on the first conductive type drift region through the opening to form an oxygen ion doped region; and removing the photoresistance, and carrying out annealing treatment on the oxygen ion doped region at a preset temperature to form the in-situ oxide with the bottom surface in an arc-shaped cross-section shape. Preferably, a second conductivity type body region is further formed at one side of the first conductivity type drift region. Preferably, after the oxygen ion doped region is annealed at a predetermined temperature, a gate structure is formed at the interface of the first conductivity type drift region and the second conductivity type body region. Preferably, after forming the gate structure, a drain region is formed in the first conductivity type drift region. Preferably, after forming the gate structure, a source region is formed in the second conductivity type body region, the in-situ oxide being located in the first conductivity type drift region between the source region and the drain region. Preferably, the first conductivity type is N-type, the second conductivity type is P-type, or the first conductivity type is P-type, and the second conductivity type is N-type. The field oxide structure is prepared by adopting the method for forming the field oxide structure, and comprises the following steps: A substrate; a first conductivity type drift region in the substrate; and the in-situ oxide is positioned in the first conductive type drift region, and the bottom surface is in an arc-shaped cross-section shape. Preferably, a second conductivity type body region is further provided at one side of the first conductivity type drift region, and an active region is further formed in the second conductivity type body region. Preferably, a drain region is also arranged in the first conductivity type drift region. Preferably, the in-situ oxide is located in the first conductivity type drift region between the source region and the drain region, and a gate structure is further arranged at the junction of the first conductivity type drift region and the second conductivity type body region. In the method for forming the field oxide structure, the in-situ oxide with the arc-shaped edge can be generated in situ in the first conductive type drift region by injecting oxygen ions with controllable dosage into the f