Semiconductor Wafer Oxygen Reduction via Bonding and Thermal Treatment
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Solution Overview
Problem
Current semiconductor wafer manufacturing methods, particularly the Czochralski process, face challenges in achieving a low concentration of interstitial oxygen and uniform resistivity, leading to doping gradients and increased costs due to the segregation effect and higher oxygen content.
Innovation Solution
A method involving high-temperature processes to reduce oxygen content in semiconductor wafers, followed by bonding with a carrier wafer and subsequent thinning, which allows for the integration of semiconductor components and achieves a specific oxygen concentration distribution, enabling the use of previously discarded wafers and reducing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the Czochralski process is used to manufacture large-diameter ingots, then the ingot size can be increased to 300 mm or larger, but the interstitial oxygen concentration becomes inherently higher due to oxygen addition from the quartz crucible
Solution Approach 1:
The patent applies preliminary action by performing a first high-temperature process before bonding to reduce oxygen content in the device wafer, and then performing a second high-temperature process after bonding to further reduce oxygen content. This preliminary and sequential treatment prepares the material in advance to achieve the desired low oxygen concentration while maintaining large ingot size.
Solution Approach 2:
The carrier wafer acts as an intermediary element in the bonding process. By bonding the device wafer to the carrier wafer and performing the second high-temperature process with the carrier wafer in place, the system enables controlled oxygen reduction while the carrier wafer protects and supports the device wafer during processing.
2Quantity of substance
If dopants are added to adjust the resistivity of CZ ingots, then the resistivity can be adjusted to a given range, but the segregation effect causes a doping gradient of 50% or more in the longitudinal direction
Solution Approach 1:
The patent performs the first high-temperature process before bonding to preliminarily reduce oxygen content and stabilize the doping distribution. By addressing oxygen reduction early in the process, the subsequent bonding and second heat treatment can focus on achieving uniform resistivity without the complicating factor of oxygen variations.
Solution Approach 2:
The patent changes the thermal parameters by performing two distinct high-temperature processes at different stages (before and after bonding). This parameter change approach allows for controlled diffusion and uniformization of dopant distribution, reducing the segregation effect and achieving more uniform resistivity throughout the ingot.
3Quantity of substance
If the Float-Zone process is used to achieve low interstitial oxygen concentration, then the oxygen content can be reduced to sufficient levels, but the ingot diameter is limited to about 200 mm and manufacturing costs increase
Solution Approach 1:
The patent extracts the oxygen reduction function from the ingot growth process itself and separates it into distinct post-growth high-temperature processes. By taking out the oxygen reduction step from the growth phase, the system can use the Czochralski process for large-diameter growth and then independently reduce oxygen content through controlled heat treatment, achieving both large size and low oxygen concentration.
Solution Approach 2:
The patent changes the physical state and thermal parameters of the ingot after growth by applying high-temperature processes. This parameter change allows the system to overcome the inherent high oxygen content of CZ-grown large-diameter ingots by thermally treating them to reduce oxygen concentration, thereby achieving the desired material properties without limiting the ingot diameter.
4Length of stationary object
If the device wafer is thinned by processing the first side, then the thickness can be reduced to a second thickness, but the oxygen content remains high in the remaining bulk material
Solution Approach 1:
The patent performs the first high-temperature process as a preliminary action before thinning to reduce oxygen content in the bulk material. By addressing oxygen reduction early, the subsequent thinning process removes less oxygen-containing material, and the second high-temperature process after bonding further reduces the remaining oxygen content in the thinned wafer.
Solution Approach 2:
The patent maintains continuity of useful action by performing oxygen reduction processes both before and after thinning. This continuous approach ensures that oxygen content is reduced throughout the entire process, compensating for the fact that thinning only removes a portion of the oxygen-containing bulk material.
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 significantly reduces interstitial oxygen concentration, achieves a desired resistivity range, and increases the yield of usable semiconductor wafers, thereby improving the efficiency and cost-effectiveness of semiconductor device production.
Implementation Method 1
subjecting the device wafer to a first high temperature process for reducing the oxygen content of the device wafer
Implementation Method 2
subjecting the device wafer to a first high temperature process for reducing the oxygen content of the device wafer
Implementation Method 3
bonding the second side of the device wafer to a first side of a carrier wafer
Implementation Method 4
bonding the second side of the device wafer to a first side of a carrier wafer
Implementation Method 5
processing the first side of the substrate wafer, which is formed by the first side of the device wafer, to reduce the thickness of the device wafer
Implementation Method 6
subjecting the substrate wafer to a second high temperature process for reducing the oxygen content at least of the device wafer bonded to the carrier wafer
Implementation Method 7
subjecting the substrate wafer to a second high temperature process for reducing the oxygen content
Data Source
AI summary
A semiconductor device includes: a semiconductor substrate having a first side, a second side opposite the first side, and a thickness; at least one semiconductor component integrated in the semiconductor substrate; a first metallization at the first side of the semiconductor substrate; and a second metallization at the second side of the semiconductor substrate. The semiconductor substrate has an oxygen concentration along a thickness line of the semiconductor substrate which has a global maximum at a position of 20% to 80% of the thickness relative to the first side. The global maximum is at least 2-times larger than the oxygen concentrations at each of the first side and the second side of the semiconductor substrate.