Nitrogen Diffusion in Silicon via Chlorine-Doped Oxide Anneal
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Solution Overview
Problem
Conventional defect curing methods for semiconductor devices, such as MOSFETs, are inadequate in fully eliminating minute voids in the crystalline structure, leading to premature annihilation of minority charge carriers and reduced transistor performance due to residual defects.
Innovation Solution
A defect repair process involving a chlorine-doped sacrificial oxide layer and a nitrogen-rich anneal atmosphere to intercalate negatively charged ions, which draw positively charged nitrogen ions deep into the silicon crystal structure to fill voids, thereby increasing minority carrier lifetimes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional defect curing methods are used, then manufacturing process is simple, but minute voids remain in crystalline structure causing premature annihilation of minority charge carriers
Solution Approach 1:
The patent applies preliminary action by performing defect curing through nitrogen diffusion before device fabrication. The monocrystalline silicon substrate is pre-treated with nitrogen atoms that occupy interstitial sites and passivate voids, preventing their harmful effects during subsequent device processing. This advance treatment ensures long minority carrier lifetimes without requiring complex post-processing steps.
Solution Approach 2:
The patent uses nitrogen atoms as intermediary substances to resolve the contradiction. Nitrogen diffuses into the silicon substrate and occupies interstitial positions, acting as a mediator that passivates voids and prevents minority carrier annihilation. This intermediary approach simplifies the overall process while achieving high reliability, as the nitrogen atoms directly address the void problem without requiring multiple complex treatment steps.
2Reliability
If high temperature anneal is performed to fill voids, then minority carrier lifetime improves, but manufacturing time and energy consumption increase
Solution Approach 1:
The patent applies parameter changes by conducting the defect curing process at relatively low temperatures (room temperature or slightly elevated temperatures) compared to conventional high temperature annealing. The nitrogen diffusion is achieved under controlled conditions that do not require prolonged high temperature exposure, thus reducing both time and energy consumption while still achieving effective void passivation and long minority carrier lifetimes.
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 process significantly improves transistor transconductance by reducing void-induced annihilation of minority carriers, resulting in longer minority carrier lifetimes and enhanced device performance.
Implementation Method 1
heating the substrate to a high temperature in an atmosphere that releases ions of a positively charged repair atom so that the intercalated negatively charged ions draw in the released positively charged ions
Implementation Method 2
the intercalated negatively charged ions draw in the released positively charged ions
Implementation Method 3
heating the substrate to a high temperature in an atmosphere that releases ions of a positively charged repair atom
Implementation Method 4
heating the substrate to a high temperature in an atmosphere
Data Source
AI summary
Performance of field effect transistors and other channel dependent devices formed on a monocrystalline substrate is improved by carrying out a high temperature anneal in a nitrogen releasing atmosphere while the substrate is coated by a sacrificial oxide coating containing easily diffusible atoms that can form negatively charged ions and can diffuse deep into the substrate. In one embodiment, the easily diffusible atoms comprise at least 5% by atomic concentration of chlorine atoms in the sacrificial oxide coating and the nitrogen releasing atmosphere includes NO. The high temperature anneal is carried out for less than 10 hours at a temperature less than 1100° C.