Single-Crystal Silicon Defect Detection With Low-Roughness RIE
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for identifying crystal defects on single-crystal silicon wafers are complex, alter the morphology of defects, and lead to high surface roughness, making it difficult to accurately determine defect positions and sizes, especially on larger areas.
Innovation Solution
A method involving reactive ion etching with a specific gas mixture of oxygen and halogenated compounds, followed by light scattering measurement, which minimizes defect geometry alteration and enables sensitive defect detection without additional thermal or chemical treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RIE methods are used to remove defect-free material, then defects can be identified as raised areas, but the surface roughness becomes high which reduces measurement sensitivity
Solution Approach 1:
The patent modifies the RIE process parameters by using a specific gas mixture composition (CF4, O2, and He in a volume ratio of 10:1:80 to 10:1:20) and controlling the etching depth to 0.5-5 μm, which changes the etching characteristics to produce less surface roughness while still revealing defects as raised areas, thereby maintaining measurement sensitivity
Solution Approach 2:
The patent uses a composite gas mixture of CF4, O2, and He that combines the advantages of each component: CF4 provides silicon etching capability, O2 helps remove organic contaminants and passivate silicon surfaces to reduce roughness, and He enhances ion mean free path for more uniform etching, together achieving defect revelation with minimal surface roughness
2Measurement precision
If additional thermal and chemical treatments are applied before and after RIE, then defect morphology can be enhanced for detection, but the original defect geometry is significantly altered making cause identification difficult
Solution Approach 1:
The patent extracts only the essential RIE step with optimized parameters from the conventional multi-step process that includes thermal and chemical treatments, removing the additional treatments that alter defect morphology while maintaining the ability to detect defects as raised areas through the optimized etching process itself
Solution Approach 2:
By changing the RIE gas mixture composition and etching parameters, the patent achieves sufficient defect revelation without needing additional thermal or chemical treatments, thereby preserving the original defect geometry while still enabling detection
3Reliability
If a large amount of material is removed during RIE, then defects are clearly revealed, but the surface geometry changes significantly reducing measurement accuracy
Solution Approach 1:
The patent applies partial etching by limiting the material removal to only 0.5-5 μm depth, which is sufficient to reveal subsurface defects as raised areas on the surface without excessively altering the overall surface geometry, achieving the right balance between defect revelation and geometry preservation
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 high-sensitivity detection of defects on large areas with minimal surface roughness, allowing for efficient process control and identification of defect causes.
Implementation Method 1
Reactive ion etching (RIE) removes defect-free single-crystal material from the surface of a single-crystal silicon workpiece, while defects, such as oxides, remain as etch residues in the form of raised areas on the surface
Implementation Method 2
The raised areas can be detected using a light microscope or a scanning electron microscope. Their number can be measured by a data processor or a particle counter
Data Source
Figure 1~2
Figure 3a~3b
Figure 4
AI summary
A method for determining crystal defects in a workpiece made of single-crystal silicon, comprising the following steps: (i) reactive ion etching of at least one surface of the workpiece in a gas mixture comprising oxygen and one or more halogenated compounds selected from the group consisting of elemental halogen X2, hydrogen halide HX and nitrogen halide NHnX3-n, wherein X is selected from the group of Cl and Br, and 0 ≤ n ≤ 2, the flux rate of oxygen and of each of the one or more halogenated compounds is not less than 5 sccm and not more than 100 sccm, and the at least one surface of the workpiece to be etched is exposed to the gas mixture for not less than 10 seconds and not more than 20 minutes; and (ii) identification of defects on the etched surface of the workpiece by light scattering measurement.