Dielectric Layer Thickness Uniformity in SOI Fabrication
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Solution Overview
Problem
Conventional finishing treatments for silicon-on-insulator substrates result in nonuniform dielectric layer thickness due to oxygen diffusion and oxide dissolution, leading to degraded thickness uniformity, especially for thin layers, which is critical for semiconductor device operation.
Innovation Solution
A process that involves providing an intermediate structure with a dielectric layer thickness profile complementary to the predetermined dissolution profile, allowing nonuniform modification of the dielectric layer thickness during a finishing treatment to achieve controlled uniformity without modifying existing equipment, using treatments like sacrificial oxidation and stabilization anneal in a reducing atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a smoothing anneal treatment is applied to decrease surface roughness, then the roughness of the upper layer is reduced, but the thickness uniformity of the dielectric layer is degraded due to oxide dissolution
Solution Approach 1:
The patent applies a preliminary oxidation step before the smoothing anneal treatment to form an additional oxide layer on the upper semiconductor layer. This pre-formed oxide layer acts as a sacrificial buffer that dissolves during the subsequent anneal, protecting the underlying dielectric layer from excessive dissolution and maintaining its thickness uniformity while still allowing the smoothing effect to occur.
Solution Approach 2:
The patent introduces a counteracting measure by forming a weak plane in the carrier substrate and creating a compensating oxide layer that offsets the harmful dissolution effect. The preliminary oxidation creates a protective oxide layer that counterbalances the oxide dissolution that would otherwise occur during the smoothing anneal, thereby preventing degradation of dielectric layer thickness 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
The process ensures a final dielectric layer with reduced nonuniformity, typically below 3%, even for thin layers, by compensating for the dissolution phenomenon, thereby maintaining precise thickness control and improving the overall quality of the silicon-on-insulator substrates.
Implementation Method 1
smoothing anneal treatments, in which the upper layer or useful layer is exposed to a neutral or reducing atmosphere raised to a high temperature, typically higher than 1,100° C., are known. This treatment, inter alia, allows, the roughness of the layer exposed to the high-temperature atmosphere to be decreased by surface reconstruction.
Implementation Method 2
in the high-temperature reducing or neutral treatment atmospheres, oxygen atoms of the dielectric layer are liable to diffuse through the upper layer and to react with the surface thereof to produce volatile species that are evacuated by the atmosphere of the furnace.
Implementation Method 3
this phenomenon is liable, to modify the properties of the subjacent dielectric layer, such as its thickness via an oxide dissolution effect
Data Source
AI summary
A process is used for fabricating a final structure comprising in succession a useful semiconductor layer, a dielectric layer and a carrier substrate. The process comprises providing an intermediate structure including an upper layer, the dielectric layer and the carrier substrate, and finishing the intermediate structure to form the final structure by performing a treatment nonuniformly modifying the thickness of the dielectric layer following a predetermined dissolution profile. The dielectric layer of the intermediate structure has a thickness profile complementary to the predetermined dissolution profile.