Monocrystalline Silicon Wafer Uniform Denuded Zone
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Solution Overview
Problem
Existing semiconductor wafers with denuded zones exhibit inhomogeneous radial depth and oxygen precipitate density, which is unfavorable for electronic component manufacturing, as the denuded zone can extend too deeply, removing necessary getter centers during back grinding, and the oxygen precipitate density is too low near the center plane.
Innovation Solution
A semiconductor wafer with a denuded zone extending uniformly from the front side to the rear side, averaging 8-18 μm in depth, and a region adjoining the denuded zone with a high density of oxygen precipitates (at least 2×10^9 cm^-3 at 30 μm from the front side), achieved through a two-stage rapid thermal anneal (RTA) treatment in an argon and ammonia atmosphere, ensuring a homogeneous depth and peak oxygen precipitate density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single RTA treatment is used to form a denuded zone, then the process time is short, but the denuded zone depth becomes inhomogeneous radially and oxygen precipitate density is insufficient
Solution Approach 1:
The single RTA treatment is segmented into two sequential treatments: a first RTA treatment that forms a denuded zone with controlled depth, and a second RTA treatment that enhances oxygen precipitate density in a specific region. This segmentation allows each treatment to be optimized for its specific function, achieving both uniform denuded zone depth and sufficient oxygen precipitate density without excessive process time
Solution Approach 2:
The two-stage RTA approach creates different local qualities within the semiconductor wafer: the first RTA creates a denuded zone with specific depth characteristics, while the second RTA creates a region with enhanced oxygen precipitate density. This local differentiation ensures that each region of the wafer has the appropriate properties for its function, resolving the contradiction between uniformity and productivity
2Manufacturing precision
If the denuded zone extends too deeply into the semiconductor wafer, then the front side quality is improved, but getter centers are removed during back grinding
Solution Approach 1:
The second RTA treatment is performed as a preliminary action before back grinding to create a region with high oxygen precipitate density. This preliminary creation of getter centers ensures that even if the denuded zone extends relatively deep, sufficient getter centers remain after back grinding to maintain reliability
Solution Approach 2:
The patent changes the thermal treatment parameters by implementing two distinct RTA treatments with different temperature profiles and atmospheric conditions. The first RTA uses specific parameters to control denuded zone depth, while the second RTA uses different parameters to maximize oxygen precipitate density, thereby resolving the contradiction between front side quality and getter center retention
3Reliability
If oxygen precipitate density is increased to provide sufficient getter centers, then reliability is improved, but the denuded zone depth becomes inhomogeneous
Solution Approach 1:
The patent segments the oxygen precipitate formation process into two distinct RTA treatments: the first treatment focuses on creating a uniform denuded zone with controlled depth, while the second treatment specifically targets increasing oxygen precipitate density in a particular region. This segmentation allows both reliability and manufacturing precision to be optimized without compromise
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 solution ensures a semiconductor wafer with a uniformly deep denuded zone and high oxygen precipitate density, maintaining sufficient getter centers during back grinding, enhancing the semiconductor wafer's performance and manufacturing efficiency.
Implementation Method 1
An RTA treatment is particularly suitable, that is to say a thermal treatment referred to as rapid thermal anneal, since in the course thereof the substrate wafer is heated to a target temperature at a high rate of temperature rise and is cooled after a comparatively short time at a high rate of temperature reduction
Implementation Method 2
If the RTA treatment is carried out in a nitriding atmosphere, this fosters the formation of oxygen precipitates in proximity to the denuded zone, since vacancies are injected in the course of the nitriding and incite the nucleation of oxygen precipitates
Implementation Method 3
A mixture of argon and ammonia is particularly suitable as an RTA atmosphere, since the target temperature of the RTA treatment can thus also be reduced in a range in which the frequency of occurrence of slip is significantly reduced
Data Source
AI summary
Monocrystalline silicon semiconductor wafers have a front side and a rear side, and a denuded zone which extends from the front side to the rear side as far as a depth which between a center and an edge of the semiconductor wafer on average is not less than 8 μm and not more than 18 μm, and having a region adjoining the denuded zone having BMDs whose density at a distance of 30 μm from the front side is not less than 2×109 cm−3. The semiconductor wafers are produced by a method comprising providing a substrate wafer of monocrystalline silicon and an RTA treating the substrate wafer, the treatment subdivided into a first thermal treatment of the substrate wafer in an atmosphere consisting of argon and into a second thermal treatment of the substrate wafer in an atmosphere consisting of argon and ammonia.