Silicon Substrate Gettering via Carbon and Oxygen Control
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Solution Overview
Problem
Conventional silicon substrates face challenges in maintaining sufficient gettering performance and preventing cracking or chipping during thinning processes, especially when the device thickness is reduced below 50 µm, leading to device malfunction and yield issues due to heavy-metal contamination.
Innovation Solution
A silicon substrate with a carbon concentration between 1.0×10^16 and 1.6×10^17 atoms/cm^3 and an initial oxygen concentration between 1.4×10^18 and 1.6×10^18 atoms/cm^3, subjected to extrinsic gettering with residual stress between 5 and 200 MPa, achieved by grinding and CMP processing using hard slurries like colloidal silica or diamond-like carbon, to form a random processing-influenced layer and maintain gettering performance during thinning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the device thickness is reduced to 50 μm or less through thinning processes, then the device meets modern size requirements, but heavy-metal contamination increases and gettering performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a damaged layer specifically on the back face of the silicon substrate through controlled mechanical processing. This damaged layer serves as a localized gettering region that captures heavy metal impurities, while the rest of the substrate maintains its structural integrity and electrical properties. The damaged layer is confined to a specific region (back face) with depth control, allowing thinning to proceed while preserving gettering functionality in the affected zone.
Solution Approach 2:
The patent implements preliminary action by forming the damaged layer on the back face before the final thinning process. This pre-formed damaged structure acts as a gettering sink that will capture impurities during subsequent processing steps. By preparing the gettering structure in advance, the substrate can undergo aggressive thinning to achieve 50 μm or less while the pre-positioned damaged layer is already ready to trap any heavy metal contamination that occurs during thinning and device fabrication.
2Stability of the object's composition
If high-temperature heat treatment is performed to reduce crystal defects from carbon injection, then crystal quality improves, but gettering function deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully controlling the temperature and duration of heat treatment to achieve a balance between defect reduction and gettering preservation. Instead of using extremely high temperatures that would anneal out the damaged layer, the patent uses moderate temperature ranges (typically 800-1100°C for controlled periods) that reduce dislocation density and improve crystal quality while maintaining enough damage in the back face layer to serve as effective gettering sinks. This optimized parameter selection resolves the contradiction between crystal quality and gettering function.
3Reliability
If conventional intrinsic gettering method is used, then oxygen precipitates form to trap impurities, but a large portion of the gettering layer is removed during thinning process
Solution Approach 1:
The patent inverts the conventional approach by creating the gettering structure on the back face of the substrate rather than in the bulk material that would be removed during thinning. Instead of forming oxygen precipitates throughout the substrate thickness and losing most of them when thinning to 50 μm, the patent generates a damaged layer specifically on the back surface that remains after thinning. This inverted positioning ensures the gettering layer is preserved rather than removed, directly solving the contradiction between maintaining gettering performance and achieving thin substrate dimensions.
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 approach ensures sufficient gettering performance, reduces metal contamination, and prevents cracking and chipping, thereby improving device yield and manufacturing efficiency for thin silicon substrates used in memory and logic devices.
Implementation Method 1
a first cause of the incorporation of impurities such as heavy metals in the silicon substrate is metal contamination in a silicon substrate manufacturing process
Implementation Method 2
when a high-temperature heat treatment is performed on a substrate into which carbon is injected, crystal defects (crystal lattice distortion and the like) formed by the carbon injection are reduced
Implementation Method 3
an intrinsic gettering (IG) method of forming oxygen precipitates in a silicon substrate
Implementation Method 4
the residual stress on the silicon substrate according to the invention is applied by subjecting the back face of the silicon substrate to grinding and subsequent CMP processing
Data Source
Figure 1a~1c
Figure 2a~2c
Figure 3
AI summary
A silicon substrate is manufactured from single-crystal silicon which is grown to have a carbon concentration equal to or higher than 1.0×1016 atoms/cm3 and equal to or lower than 1.6×1017 atoms/cm3 and an initial oxygen concentration equal to or higher than 1.4×1018 atoms/cm3 and equal to or lower than 1.6×1018 atoms/cm3 by a CZ method. A device is formed on a front, the thickness of the silicon substrate is equal to or more than 5 µm and equal to or less than 40 µm, and extrinsic gettering which produces residual stress equal to or more than 5 Mpa and equal to or less than 200 Mpa is applied to a back face of the substrate.