Silicon Substrate Analysis for Thick Nitride Film ICP-MS Accuracy
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Solution Overview
Problem
Current methods for analyzing silicon substrates with thick nitride films (200 nm or more) using ICP-MS are unable to achieve high accuracy due to the formation of Si(NH4)xFy instead of ideal Si(NH4)2F6, leading to excessive Si concentration in the analysis liquid, which interferes with the detection of small metal impurities.
Innovation Solution
A method involving vapor phase decomposition with hydrofluoric acid, followed by scanning with a recovery liquid and subsequent treatment with a strong acid or alkali solution to convert Si(NH4)xFy into SiF4, reducing Si concentration and enabling accurate analysis with ICP-MS, using a silicon substrate analysis apparatus with specific chambers and nozzles for each step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vapor phase decomposition is performed with hydrofluoric acid to extract impurities from silicon substrate with thick nitride film, then impurities can be transferred to analysis liquid, but Si concentration in analysis liquid becomes excessively high (1000 ppm or more) interfering with accurate detection
Solution Approach 1:
The patent applies preliminary action by performing heating treatment at 100-130°C for 5-30 minutes before the analysis liquid scanning step. This pre-treatment converts Si(NH4)xFy into SiF4 gas that is removed, reducing Si concentration in the analysis liquid from 1000 ppm or more to 10 ppm or less, thereby enabling accurate metal impurity detection without Si interference
Solution Approach 2:
The patent changes physical parameters by controlling heating temperature (100-130°C) and time (5-30 minutes) to optimize the conversion of Si(NH4)xFy to SiF4. By adjusting these parameters, the Si concentration is reduced to an acceptable level while maintaining the ability to detect trace metal impurities accurately
2Reliability
If nitride film thickness is increased to 200 nm or more for device fabrication, then device performance is improved, but analysis accuracy deteriorates due to formation of Si(NH4)xFy instead of ideal Si(NH4)2F6
Solution Approach 1:
The patent converts the harmful effect of Si(NH4)xFy formation (which causes high Si concentration and poor analysis accuracy) into a beneficial process. By heating at 100-130°C, Si(NH4)xFy is converted to SiF4 gas that can be easily removed, transforming the analysis problem into a solution that enables accurate metal impurity detection even on substrates with thick nitride films of 200 nm or more
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 high-accuracy analysis of small metal impurities in nitride films thicker than 200 nm, reducing Si concentration to about 10 ppm, thereby overcoming the limitations of previous techniques.
Implementation Method 1
subjecting the silicon substrate to vapor phase decomposition treatment with an etching gas in the vapor phase decomposition chamber
Implementation Method 2
drying the silicon substrate by heating
Implementation Method 3
Heating of the compound causes the following reaction, so that Si can be removed as a SiF4 gas
Implementation Method 4
performing inductive coupling plasma analysis on the analysis liquid into which the analysis target is transferred
Data Source
AI summary
The present invention provides a method for analyzing a silicon substrate, by which impurities such as a very small amount of metal in a silicon substrate provided with a thick nitride film can be analyzed with high accuracy with ICP-MS, and is characterized by use of a silicon substrate analysis apparatus including an analysis scan port having a load port, a substrate conveyance robot, an aligner, a drying chamber, a vapor phase decomposition chamber, an analysis stage and a nozzle for analysis of a substrate; an analysis liquid collection unit; and an analyzer for performing inductive coupling plasma analysis.