Cap Oxide Layer Thickness Control for AEI CD Precision
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Solution Overview
Problem
As semiconductor feature sizes shrink, the difference between After-Develop-Inspection CD (ADI CD) and After-Etch-Inspection CD (AEI CD) increases, making precise control of AEI CD critical to prevent malfunctions in devices like SRAM, where slight deviations can cause contact-gate shorting.
Innovation Solution
A method involving the deposition of a dielectric layer and a cap oxide layer with a controlled thickness, followed by a CMP process to planarize and form a contact hole, where the ADI CD is altered based on the cap oxide layer thickness to achieve a standard AEI CD, using a lithographic process and dry etching with the photoresist as an etching hard mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the feature size of semiconductor devices is reduced, then the device dimension shrinks to nano scale, but the difference between ADI CD and AEI CD becomes larger, making it difficult to precisely control AEI CD
Solution Approach 1:
The patent introduces a cap oxide layer deposition step before lithography to preliminarily adjust the structure. By controlling the cap oxide layer thickness, the system pre-compensates for etching variations, ensuring that the final AEI CD meets specifications even as device dimensions shrink to nano scale.
Solution Approach 2:
The patent changes the parameter being controlled from direct AEI CD control to indirect control via cap oxide layer thickness. By adjusting the cap oxide layer thickness parameter, the system influences the etching process outcome, thereby achieving precise AEI CD control through parameter transformation.
2Manufacturing precision
If a cap oxide layer is deposited to control AEI CD, then AEI CD precision is improved, but the process complexity increases due to additional deposition and measurement steps
Solution Approach 1:
The cap oxide layer serves multiple functions: it acts as an etch stop layer, a thickness reference for control, and a means to adjust the etching profile. By making this single layer multi-functional, the patent reduces overall process complexity despite adding the cap oxide deposition step.
Solution Approach 2:
The system uses the cap oxide layer itself as the reference standard for thickness measurement and control. Instead of requiring external reference structures or complex measurement systems, the cap oxide layer provides self-referential control data, simplifying the overall measurement and control architecture.
3Reliability
If the ADI CD is altered based on cap oxide layer thickness, then AEI CD specification compliance is improved, but the number of process parameters to control increases
Solution Approach 1:
The patent implements a feedback mechanism where the measured cap oxide layer thickness is used to determine the appropriate ADI CD target. This closed-loop feedback ensures that the process automatically adjusts to maintain specification compliance, improving reliability while keeping parameter control manageable through automated feedback control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for precise control of AEI CD, ensuring device reliability by maintaining the desired dimensions and preventing contact-gate shorting, while adjusting ADI CD and etching recipes as needed to meet specifications.
Implementation Method 1
A CMP process is performed to planarize the dielectric layer
Implementation Method 2
A dry etching process is performed using the photoresist layer as an etching hard mask to etch the cap oxide layer and the dielectric layer through the opening
Data Source
AI summary
Automatic process control of after-etch-inspection critical dimension. A dielectric layer is deposited over a substrate and is then planarized to a first thickness. A cap oxide layer having a second thickness is deposited, wherein the combination of the first thickness and the second thickness is substantially constant. An ADI CD of a contact hole to be formed on the substrate is altered and pre-determined based on the second thickness of the cap oxide layer. A photoresist layer is formed on the cap oxide layer. An opening having the predetermined ADI CD is formed in the photoresist layer. Using the photoresist layer as an etching mask, the cap oxide layer and the dielectric layer is etched through the opening to form a contact hole having an AEI CD.