Well Modulation Using Oxide Step Heights for Defect Inspection
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Solution Overview
Problem
Existing methods struggle to effectively distinguish and inspect defects in integrated circuits due to the lack of clear differentiation between p-well and n-well regions, leading to difficulties in identifying defect locations and causes.
Innovation Solution
A method involving the formation of p-well and n-well regions with controlled step heights by modulating the thickness of pad oxide layers and performing well anneal processes with oxygen-containing gases, followed by selective oxidation, to create distinguishable top surfaces and grooves for defect inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional well formation methods are used, then manufacturing process is simple, but defect inspection accuracy deteriorates due to inability to distinguish p-well and n-well regions
Solution Approach 1:
The patent applies local quality by creating different oxide layer thicknesses over p-well and n-well regions. Specifically, a first oxide layer is formed over the p-well region and a second oxide layer is formed over the n-well region, where the second oxide layer has a different thickness than the first oxide layer. This differential oxidation creates distinct surface topographies that enable clear visual differentiation between p-well and n-well regions during defect inspection, directly improving measurement precision without requiring fundamentally new manufacturing approaches.
2Loss of information
If pad oxide layer thickness is not controlled, then manufacturing process is simpler, but top surface differentiation between p-well and n-well regions is insufficient for defect identification
Solution Approach 1:
The patent applies preliminary action by forming a pad oxide layer with controlled, non-uniform thickness before well formation. The pad oxide layer is prepared such that it has a first thickness over the p-well region and a second thickness over the n-well region. This preliminary differentiation of oxide thicknesses ensures that subsequent processing steps will produce distinguishable surface topographies, preserving defect location information that would otherwise be lost in conventional uniform oxide processes.
3Ease of operation
If uniform oxide layers are used over p-well and n-well regions, then manufacturing process is simpler, but defect position determination becomes difficult
Solution Approach 1:
The patent applies the color changes principle by creating optical contrast differences through differential oxide thicknesses. The first oxide layer over the p-well region and the second oxide layer over the n-well region have different thicknesses, which results in different optical properties when viewed under inspection tools. This allows defect positions to be easily determined through visual or optical inspection, as the different oxide thicknesses create distinguishable contrast patterns that indicate whether a defect is located over a p-well or n-well region.
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
Enables clear differentiation between p-well and n-well regions, allowing for precise defect identification and determination of defect positions through Atomic Force Microscopy, enhancing defect inspection accuracy.
Implementation Method 1
A well anneal process is then performed, with the process gas for the well anneal process including oxygen. The pad oxide layer over the p-well region is made thinner than the portion of the pad oxide layer over the n-well region. Accordingly, in the well anneal process, a thicker surface portion of the n-well region is oxidized than the oxidized surface portion of the p-well region.
Implementation Method 2
A well anneal process is then performed, with the process gas for the well anneal process including oxygen.
Data Source
AI summary
A method includes forming a pad layer. The pad layer includes a first portion over a first part of a semiconductor substrate, and a second portion over a second part of the semiconductor substrate. The first portion has a first thickness, and the second portion has a second thickness smaller than the first thickness. The semiconductor substrate is then annealed to form a first oxide layer over the first part of the semiconductor substrate, and a second oxide layer over the second part of the semiconductor substrate. The pad layer, the first oxide layer, and the second oxide layer are removed. A semiconductor layer is epitaxially grown over and contacting the first part and the second part of the semiconductor substrate.