Low-Field SIMS Metrology for Beam Deflection Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current Secondary Ion Mass Spectrometry (SIMS) systems face challenges in inline process control for semiconductor manufacturing due to high costs, measurement time, tool availability, and unpredictable grounding issues leading to sample charging and beam deflection, which affect accuracy and precision.
Innovation Solution
A SIMS system design with a low extraction voltage, multiple detectors, and a magnetic sector spectrograph for parallel mass species measurement, combined with charge compensation mechanisms and internal calibration features to ensure precise and efficient analysis on product wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional SIMS system with high extraction voltage is used, then secondary ion collection efficiency is improved, but beam deflection and sample charging increase, reducing measurement precision
Solution Approach 1:
The patent inverts the conventional approach by using a low extraction voltage (0-10 V) instead of high voltage to extract secondary ions. This counterintuitive solution reduces beam deflection and sample charging effects while maintaining sufficient ion collection through optimized detector geometry and position, directly resolving the contradiction between ion collection efficiency and measurement precision.
Solution Approach 2:
The patent changes the extraction voltage parameter from conventional high values to a low range (0-10 V), and simultaneously adjusts related parameters such as detector position, detector area, and acceleration voltage to compensate. This parameter optimization maintains measurement precision while minimizing harmful beam deflection effects.
2Measurement precision
If SIMS measurement time is extended to improve analysis accuracy, then measurement precision is improved, but tool availability and productivity decrease
Solution Approach 1:
The patent enables continuous SIMS measurements by using a low extraction voltage regime that prevents sample charging, allowing the primary ion beam to continuously sputter and analyze the sample without interruption for charge neutralization. This continuous operation improves both analysis accuracy and tool availability simultaneously.
Solution Approach 2:
The low extraction voltage system inherently prevents sample charging, making the system self-regulating without requiring external charge neutralization systems or interruption of the measurement process. This self-service characteristic enables uninterrupted continuous measurement, improving both precision and productivity.
3Measurement precision
If multiple mass species are measured sequentially, then measurement precision is improved, but measurement time increases, reducing productivity
Solution Approach 1:
The patent segments the detection function into multiple detectors positioned at different angles and locations, each optimized for detecting specific mass species or ion types. This parallel detection architecture enables simultaneous measurement of multiple mass species without sequential scanning, improving both precision and measurement speed.
Solution Approach 2:
The patent transitions from sequential one-dimensional mass analysis to parallel multi-dimensional detection by positioning multiple detectors in different spatial locations and angles. This dimensional expansion allows simultaneous detection of multiple ion species, eliminating time-consuming sequential measurement while maintaining identification accuracy.
4Quantity of substance
If a high extraction field is used to enhance secondary ion emission, then ion yield is improved, but sample charging and beam deflection increase, worsening measurement reliability
Solution Approach 1:
The patent optimizes the extraction field parameter by reducing voltage to 0-10 V and compensates for lower ion yield through increased detector area, optimized detector positioning, and adjusted acceleration voltage. This parameter transformation maintains sufficient ion yield while eliminating sample charging and beam deflection, improving measurement reliability.
Solution Approach 2:
The low extraction voltage system serves multiple functions simultaneously: it extracts secondary ions, prevents sample charging, minimizes beam deflection, and enables continuous measurement. This multi-functionality achieves reliable measurements without requiring high extraction fields, resolving the contradiction between ion yield and reliability.
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 system enables high-precision, cost-effective, and non-destructive inline process control in semiconductor manufacturing by minimizing beam deflection, reducing measurement time, and maintaining tool availability, while addressing sample charging and improving depth resolution.
Implementation Method 1
SIMS is a technique used to analyze the composition of solid surfaces and thin films by sputtering the surface of the specimen with a focused primary ion beam and collecting and analyzing ejected secondary ions
Implementation Method 2
A sector field mass spectrometer uses a combination of an electrostatic analyzer and a magnetic analyzer to separate the secondary ions by their mass to charge ratio
Implementation Method 3
A sector field mass spectrometer uses a combination of an electrostatic analyzer and a magnetic analyzer to separate the secondary ions by their mass to charge ratio
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Systems and approaches for semiconductor metrology and surface analysis using Secondary Ion Mass Spectrometry (SIMS) are disclosed. In an example, a secondary ion mass spectrometry (SIMS) system includes a sample stage. A primary ion beam is directed to the sample stage. An extraction lens is directed at the sample stage. The extraction lens is configured to provide a low extraction field for secondary ions emitted from a sample on the sample stage. A magnetic sector spectrograph is coupled to the extraction lens along an optical path of the SIMS system. The magnetic sector spectrograph includes an electrostatic analyzer (ESA) coupled to a magnetic sector analyzer (MSA).