Silicon Wafer Gettering via Oxygen Peak Diffusion
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Solution Overview
Problem
The challenge is to manufacture a silicon single crystal wafer with a uniform gettering layer close to the device forming region, as the reduction in epitaxial layer thickness leads to increased oxygen striation, resulting in adverse effects such as increased dark current, stripe image noise, and degradation of electrical characteristics in solid-state image pickup devices and memory devices.
Innovation Solution
A method involving a first heat treatment in an oxygen-containing atmosphere followed by rapid cooling to form an oxygen concentration peak region near the surface, and a second heat treatment to agglomerate oxygen, creating a radially uniform oxygen concentration peak for effective gettering, with specific conditions for temperature, time, and atmosphere to prevent oxygen diffusion and defect formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the epitaxial layer thickness is reduced, then the device integration density is improved, but oxygen striation increases causing dark current increase and stripe image noise
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment in an oxygen-containing atmosphere before epitaxial growth to inwardly diffuse oxygen into the silicon substrate, creating a uniform oxygen concentration distribution in advance. This pre-diffusion prevents oxygen striation that would otherwise occur when the epitaxial layer thickness is reduced, thereby eliminating dark current and stripe image noise while maintaining high device integration density.
Solution Approach 2:
The patent utilizes parameter changes by controlling the oxygen concentration distribution through specific heat treatment parameters (temperature, time, atmosphere composition) during the first heat treatment. By adjusting these parameters, a uniform oxygen concentration is achieved in the substrate before epitaxial growth, preventing the formation of oxygen striation patterns that cause harmful effects in thin epitaxial layers.
2Reliability
If conventional heat treatment is performed to form gettering layer, then metal contamination is removed, but oxygen diffuses outward causing depletion in surface layer and defect formation
Solution Approach 1:
The patent applies preliminary action by performing the first heat treatment in an oxygen-containing atmosphere before the conventional heat treatment. This pre-diffusion of oxygen into the substrate creates a reservoir of oxygen that prevents outward diffusion during subsequent gettering processes, thereby eliminating surface layer oxygen depletion and defect formation while maintaining effective metal contamination removal.
Solution Approach 2:
The patent applies preliminary anti-action by inwardly diffusing oxygen into the substrate during the first heat treatment, which counteracts the outward oxygen diffusion that occurs during conventional heat treatment. This preliminary opposite action prevents oxygen depletion in the surface layer and subsequent defect formation, while still allowing the gettering layer to effectively remove metal contamination.
3Manufacturing precision
If multiple heat treatment steps are added to control oxygen distribution, then oxygen uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies merging by combining the oxygen inward diffusion process with the gettering layer formation process into a single integrated heat treatment sequence. The first heat treatment in oxygen-containing atmosphere serves dual purposes: it inwardly diffuses oxygen to create uniform distribution, and it prepares the conditions for subsequent gettering. This merging reduces the number of separate process steps compared to conventional methods while achieving superior oxygen uniformity.
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 approach results in a high-quality silicon single crystal wafer with a uniform gettering layer that suppresses oxygen diffusion and defect formation, improving the electrical characteristics and reducing noise in image pickup devices and memory devices.
Implementation Method 1
a first heat treatment for holding a silicon single crystal wafer in an oxygen containing atmosphere at a first heat treatment temperature for 1 to 60 seconds and cooling it to 800° C. or less at a temperature falling rate of 1 to 100° C./second by using a rapid heating/rapid cooling apparatus and thereby inwardly diffusing oxygen
Implementation Method 2
subsequently the silicon single crystal wafer is subjected to a second heat treatment for agglomerating oxygen in the silicon single crystal wafer to the oxygen concentration peak region
Implementation Method 3
cooling it to 800° C. or less at a temperature falling rate of 1 to 100° C./second by using a rapid heating/rapid cooling apparatus
Data Source
AI summary
According to the present invention, there is provided a method for manufacturing a silicon single crystal wafer, wherein a first heat treatment for holding a silicon single crystal wafer in an oxygen containing atmosphere at a first heat treatment temperature for 1 to 60 seconds and cooling it to 800° C. or less at a temperature falling rate of 1 to 100° C./second by using a rapid heating/rapid cooling apparatus is performed to inwardly diffuse oxygen and form an oxygen concentration peak region near a surface of the silicon single crystal wafer, and then a second heat treatment is performed to agglomerate oxygen in the silicon single crystal wafer into the oxygen concentration peak region. As a result, it is possible to provide the method for manufacturing a silicon single crystal wafer that enables forming an excellent gettering layer close to a device forming region.