Controlling ADI-AEI CD Difference Ratio in IC Etching
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Solution Overview
Problem
The challenge in integrated circuit fabrication is controlling the ADI-AEI CD difference ratio of openings with different sizes, as high-resolution photolithographic processes are costly and difficult to manage, leading to issues with contact resistance and misalignment in pattern formation.
Innovation Solution
A method involving a multi-step etching process with specific etching parameters and gas usage to control the ADI-AEI CD difference ratio by forming a patterned photoresist and Si-containing material layers, followed by etching steps using these layers as masks to form openings with precise dimensions, including trimming and polymer deposition to adjust the size differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-resolution photolithographic process is used to reduce pattern size, then manufacturing precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the etching process parameters by introducing a multi-step etching sequence with different gases and conditions. The first etching step uses CF4/O2 gas mixture, the second step uses CHF3 gas, and the third step uses CF4 gas. Each step has specific duration and power parameters that are optimized to achieve the desired CD difference ratio control without requiring high-resolution photolithography
Solution Approach 2:
The patent introduces an intermediary approach by using etching process control as a mediator to achieve the desired opening size control. Instead of relying solely on photolithographic resolution, the etching process with multiple steps and different gas chemistries acts as an intermediary mechanism to fine-tune the critical dimensions and achieve the required precision
2Manufacturing precision
If etching parameters are adjusted to control ADI-AEI CD difference ratio of different sized openings, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The patent segments the etching process into three distinct steps, each with specific functions and parameters. The first step (CF4/O2) addresses initial etching, the second step (CHF3) controls polymer deposition and etching rate, and the third step (CF4) completes the etching. This segmentation allows independent optimization of each step to control the ADI-AEI CD difference ratio for different opening sizes
Solution Approach 2:
The patent introduces dynamic control mechanisms by varying etching parameters (gas flow rates, power, pressure, temperature) across different etching steps and for different opening sizes. The process dynamically adjusts conditions to maintain optimal etching rates and polymer deposition levels, enabling precise control of CD differences for both small and large openings simultaneously
3Manufacturing precision
If size of share contact opening is reduced to avoid misalignment, then manufacturing precision is improved, but electrical conductivity deteriorates
Solution Approach 1:
The patent changes the etching parameters specifically for the share contact opening region to achieve a different CD difference ratio compared to square contacts. By adjusting gas flow rates, power, and etching duration in the multi-step process, the patent optimizes the final opening size to maintain both alignment precision and sufficient electrical conductivity
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 effectively controls the ADI-AEI CD difference ratio within acceptable ranges, reducing the risk of contact misalignment and improving the reliability of the fabrication process while minimizing costs by avoiding the need to amend photomasks.
Implementation Method 1
steps of etching the Si-containing material layer, the etching resistive layer and the target material layer are performed in sequence
Implementation Method 2
generate a polymer layer on sidewalls of the patterned photoresist layer and the patterned Si-containing material layer
Data Source
AI summary
A method for controlling an ADI-AEI CD difference ratio of openings having different sizes is described. The openings are formed through a silicon-containing material layer, an etching resistive layer and a target material layer in turn. Before the opening etching steps, at least one of the opening patterns in the photoresist mask is altered in size through photoresist trimming or deposition of a substantially conformal polymer layer. A first etching step forming thicker polymer on the sidewall of the wider opening pattern is performed to form a patterned Si-containing material layer. A second etching step is performed to remove exposed portions of the etching resistive layer and the target material layer. At least one parameter among the parameters of the photoresist trimming or polymer layer deposition step and the etching parameters of the first etching step is controlled to obtain a predetermined ADI-AEI CD difference ratio.