Wafer Slope SIMS Analysis for Accurate Doping Depth Profiling
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Solution Overview
Problem
Existing SIMS methods for analyzing doped elements in wafers suffer from inaccurate results due to surface contamination and sidewall effects caused by ion beam bombardment, leading to mixed ions that interfere with doping depth analysis.
Innovation Solution
A wafer sample analysis method using a secondary-ion-mass spectroscope (Sims) that includes a slope with a protective layer and a doped layer, allowing for accurate imaging and analysis of doping depth and concentration without continuous ion beam bombardment, thereby preventing sidewall effects and surface contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If ion beam bombardment is used to analyze elements in wafer sample, then element detection capability is improved, but surface contamination and sidewall effects occur causing mixed ions that reduce analysis accuracy
Solution Approach 1:
The patent applies preliminary action by forming a protective layer on the wafer sample surface before SIMS analysis. This protective layer is prepared in advance to prevent surface contamination during the ion beam bombardment process, thereby maintaining measurement precision while enabling element detection.
Solution Approach 2:
The protective layer serves as an intermediary between the ion beam and the wafer sample surface. It allows the ion beam to analyze elements while preventing direct contact between the ion beam and the sample surface, thus avoiding surface contamination and sidewall effects that would otherwise create mixed ions and reduce analysis accuracy.
2Loss of information
If continuous ion beam bombardment is performed to obtain doping depth information, then doping depth analysis is enabled, but sidewall effects increase causing mixed ions that interfere with analysis
Solution Approach 1:
The protective layer is formed in advance before SIMS analysis to prevent sidewall effects during continuous ion beam bombardment. This preliminary protective measure allows doping depth information to be obtained while preventing the generation of mixed ions from sidewall regions.
Solution Approach 2:
The protective layer acts as an intermediary that enables continuous ion beam bombardment for doping depth analysis while preventing the sidewall effects that would otherwise generate mixed ions and interfere with the accuracy of doping depth information.
3Ease of manufacture
If wafer surface is exposed to air before analysis, then sample preparation is simplified, but surface contamination occurs affecting signal collection
Solution Approach 1:
The protective layer is formed on the wafer surface in advance during normal fabrication processes, before SIMS analysis. This preliminary protection allows the surface to be exposed to air during handling and preparation without causing contamination, as the protective layer barrier is already in place.
Solution Approach 2:
The protective layer serves as an intermediary barrier between the wafer surface and the ambient air. It allows simplified sample preparation with air exposure while preventing surface contamination that would otherwise affect signal collection during SIMS analysis.
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
The method provides more accurate analysis of doping depth and concentration by preventing sidewall effects and surface contamination, resulting in precise determination of element distributions and concentrations in the wafer sample.
Implementation Method 1
The Sims uses a high-energy primary ion beam to bombard a surface of a sample, so that atoms or atomic groups on the surface of the sample absorb energy and are sputtered from the surface to generate secondary ions
Implementation Method 2
These charged ions can be obtained after passing through a mass analyzer, so that a map of the surface information of the sample can be obtained
Data Source
AI summary
A wafer sample analysis method includes: providing a wafer sample, the wafer sample at least including a slope configured to expose a substrate, a first protective layer and a first doped layer on a same surface, the first protective layer being formed on the substrate, and the first doped layer being formed on the first protective layer; and acquiring and analyzing a slope image of the slope to obtain a doping depth and a doping concentration of elements in the wafer sample in the slope image.