Semiconductor Gate Cut Etching for Transistor Isolation Integrity
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Solution Overview
Problem
Existing etching processes for semiconductor manufacturing can damage transistor devices and logic structures, particularly affecting the profiles of metal gates during the formation of cuts to isolate transistors, leading to negative alterations and damage.
Innovation Solution
A controlled and multi-stage etching process, known as CPODE, is employed to safely remove material from transistor structures without damaging them, utilizing different etching parameters at various depths and incorporating a CPODE technique to define profiles that aid in the adherence of semiconductor device components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional etching process is used to form cuts to isolate transistors, then the transistors can be electrically isolated, but the metal gate profiles are damaged and negative alterations occur
Solution Approach 1:
The etching process is divided into multiple sequential stages with different etching conditions. The first stage uses a first set of etching conditions to etch through the polysilicon layer, and the second stage uses a second set of etching conditions to etch through the dielectric layer. This segmentation allows each stage to be optimized for its specific task, preventing damage to the metal gate profile while achieving complete isolation.
Solution Approach 2:
Different etching conditions are applied at different stages of the process. The first etching stage uses conditions optimized for removing polysilicon without damaging the metal gate, while the second stage uses conditions optimized for etching the dielectric layer. This local quality approach ensures that each region of the process has the appropriate etching characteristics for its specific material and function.
2Reliability
If etching is performed to remove polysilicon and dielectric layers, then transistor isolation is achieved, but damage occurs to transistor devices and logic structures
Solution Approach 1:
The first etching stage is performed as a preliminary action to remove the polysilicon layer before the second stage etches the dielectric layer. This preliminary removal of polysilicon prevents it from interfering with the second etching process and reduces the risk of damage to underlying transistor structures during the more aggressive second stage etching.
Solution Approach 2:
The two-stage etching process acts as an intermediary approach between complete isolation and device safety. By introducing an intermediate stage with different etching conditions, the process achieves both complete isolation and protection of transistor devices, serving as a mediator between these two requirements.
3Productivity
If a single-stage etching process is used, then the process is simpler and faster, but it cannot safely remove material at different depths without damaging structures
Solution Approach 1:
The etching process is made dynamic by changing the etching conditions between stages. The first stage uses etching conditions optimized for polysilicon removal, and the second stage uses different conditions optimized for dielectric layer removal. This dynamic adjustment of process parameters allows precise control over material removal at different depths, achieving both efficiency and precision.
Data Source
AI summary
A semiconductor device includes a first channel region extending in a first lateral direction, and comprising a first epitaxial structure; a second channel region extends in the first lateral direction, next to the first channel region along a second lateral direction, and comprising a pair of second epitaxial structures; a third channel region formed over the substrate, extending in the first lateral direction, disposed next to the first channel region along the second lateral direction, and comprising a pair of third epitaxial structures; first and second metal gate structures extend in the second lateral direction and traverse the second and third channel regions, respectively. A first upper portion of the dielectric structure has its opposite sidewalls tilted away from each other along a vertical direction extending from a top surface of the dielectric structure toward the substrate.