Thin SOI Substrate Formation Without Implantation Damage
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Solution Overview
Problem
The existing methods for forming thin semiconductor-on-insulator (SOI) substrates face challenges such as implant radiation and plasma damage during hydrogen implantation, leading to high leakage and power consumption, as well as increased costs and process complexity, and trapped positive charges affecting device performance.
Innovation Solution
A method involving the deposition of insulator layers with neutral or negative charges, epitaxial formation of the device layer, and cyclic thinning to achieve precise thickness, avoiding hydrogen implantation and plasma exposure, which includes forming a first and second insulator layer on a handle substrate, bonding a sacrificial substrate, and removing it to create a thin SOI substrate with undoped silicon germanium or boron-doped etch stop layers for precise control and minimal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen implantation is used to form thin SOI substrates, then the device layer can be thinned to desired thickness, but implant radiation and plasma damage occur leading to high leakage and power consumption
Solution Approach 1:
The patent removes the hydrogen implantation step from the process entirely. Instead of using hydrogen implantation to thin the device layer, the invention uses a combination of mechanical thinning, selective etching, and oxidation techniques to achieve the desired thickness without introducing implant radiation or plasma damage to the semiconductor structures.
Solution Approach 2:
The patent introduces a sacrificial layer that is intentionally designed to be removed after serving its temporary purpose of enabling precise device layer thinning. This sacrificial layer allows the device layer to be thinned to precise thicknesses without the need for harmful hydrogen implantation, and is subsequently removed to complete the SOI structure formation.
2Manufacturing precision
If hydrogen implantation is used to thin the device layer, then thickness control is achieved, but process complexity and costs increase
Solution Approach 1:
The patent divides the device layer thinning process into multiple discrete steps: initial mechanical thinning, selective oxidation to form a thin oxide layer, and controlled etching. This segmentation allows for precise thickness control through cumulative small adjustments rather than relying on a single complex hydrogen implantation step, thereby reducing overall process complexity.
Solution Approach 2:
The patent performs preliminary oxidation of the device layer before final thinning operations. By forming an oxide layer first and then selectively removing it, the process enables precise thickness control at a later stage when the structure is already formed, avoiding the need for complex real-time thickness adjustment during implantation.
3Manufacturing precision
If hydrogen implantation is performed, then device layer thinning is achieved, but trapped positive charges affect device performance
Solution Approach 1:
The patent converts the potential harm of oxidation by performing controlled oxidation that creates an oxide layer which is then selectively removed. This process, when done correctly, actually improves device performance by creating a clean interface and removing contaminants, while avoiding the trapped positive charges that would result from hydrogen implantation.
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 reduces leakage and power consumption, enhances device performance by preventing implant radiation and plasma damage, and allows for precise control over the device layer thickness, leading to higher power efficiency and uniformity in semiconductor devices.
Implementation Method 1
a bond wafer is oxidized to form an oxide layer surrounding the bond wafer
Implementation Method 2
Hydrogen ions are implanted into the bond wafer, through the oxide layer, to form a hydrogen-rich region buried in the bond wafer
Implementation Method 3
the bond wafer is split along the hydrogen-rich region to partially remove the oxide layer and the bond wafer from the handle wafer
Data Source
AI summary
Various embodiments of the present application are directed to a method for forming a thin semiconductor-on-insulator (SOI) substrate without implantation radiation and/or plasma damage. In some embodiments, a device layer is epitaxially formed on a sacrificial substrate and an insulator layer is formed on the device layer. The insulator layer may, for example, be formed with a net charge that is negative or neutral. The sacrificial substrate is bonded to a handle substrate, such that the device layer and the insulator layer are between the sacrificial and handle substrates. The sacrificial substrate is removed, and the device layer is cyclically thinned until the device layer has a target thickness. Each thinning cycle comprises oxidizing a portion of the device layer and removing oxide resulting from the oxidizing.