Semiconductor Gate Oxide Thickness Control via Radical Oxidation
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Solution Overview
Problem
Conventional methods for forming semiconductor gate electrodes result in etching damage and excessive oxidation, leading to punch-through phenomena and whisker formation, which can cause shorts between wirings and reduce semiconductor device reliability.
Innovation Solution
A method involving the use of oxygen radicals at a controlled temperature to form a gate structure, followed by a hydrogen reduction process to convert tungsten oxide back to tungsten, thereby reducing whisker formation and optimizing gate oxide layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a re-oxidation process is performed at high temperature (no less than 800°C) to cure etching damage, then etching damage is sufficiently cured, but the gate oxide layer thickness becomes excessive due to bird's beak and punch-through phenomenon occurs
Solution Approach 1:
The patent changes the temperature parameter from high temperature (800°C or above) to low temperature (below 800°C) for the oxidation process. This parameter change allows the oxidation to proceed at a rate that cures etching damage without causing excessive gate oxide layer growth and punch-through phenomenon
Solution Approach 2:
The patent uses rapid thermal oxidation (RTO) process which provides strong oxidizing conditions at low temperature. This accelerated oxidation method enables sufficient curing of etching damage without requiring high temperature, thereby preventing bird's beak and punch-through issues
2Manufacturing precision
If a radical oxidation process is performed at relatively low temperature to improve punch-through phenomenon, then punch-through is improved, but efficiency for curing etching damage is reduced and gate electrode edge is not sufficiently rounded
Solution Approach 1:
The patent employs rapid thermal oxidation (RTO) which provides intense oxidizing conditions that enable effective curing of etching damage at low temperature. The strong oxidant action ensures sufficient rounding of gate electrode edges while maintaining precise gate oxide layer thickness control
Solution Approach 2:
The patent uses rapid thermal oxidation process which applies oxidation in a controlled, time-limited manner. This periodic action allows sufficient oxidation to cure etching damage and round edges without prolonged exposure that would cause excessive oxide growth
3Shape
If oxygen flux is increased to round the edge of gate electrode, then edge rounding is improved, but tungsten is oxidized to form tungsten oxide (WOx) on surface
Solution Approach 1:
The patent changes the temperature parameter to low temperature (below 800°C) where tungsten oxidation is suppressed. At this temperature, even with increased oxygen flux for edge rounding, tungsten remains stable and does not form oxide whiskers
Solution Approach 2:
The patent creates an oxidation environment controlled at low temperature that is effectively inert to tungsten. By performing oxidation below 800°C, the environment allows oxygen to react with silicon for gate oxide formation and edge rounding, but does not oxidize tungsten
4Shape
If oxidation process is performed at high temperature (no less than 800°C) to round gate electrode edge, then edge rounding is achieved, but bird's beak is generated and punch-through phenomenon occurs
Solution Approach 1:
The patent changes the temperature parameter from high temperature (800°C or above) to low temperature (below 800°C) for the oxidation process. This parameter change enables effective edge rounding while preventing excessive gate oxide layer growth and punch-through phenomenon
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 suppresses whisker growth and punch-through phenomena, improving semiconductor device yield by preventing shorts between wirings and maintaining a rounded edge on the gate electrode.
Implementation Method 1
The first preliminary gate structure is oxidized using oxygen radicals under a first temperature for adjusting a thickness of the gate oxide layer to form a second preliminary gate structure having tungsten oxide that is partially formed on a surface
Implementation Method 2
A gas including hydrogen is applied to the second preliminary gate structure to reduce the tungsten oxide to tungsten
Data Source
AI summary
In a method for forming a gate in a semiconductor device, a first preliminary gate structure is formed on a substrate. The first preliminary gate structure includes a gate oxide layer, a polysilicon layer pattern and a tungsten layer pattern sequentially stacked on the substrate. A primary oxidation process is performed using oxygen radicals at a first temperature for adjusting a thickness of the gate oxide layer to form a second preliminary gate structure having tungsten oxide. The tungsten oxide is reduced to a tungsten material using a gas containing hydrogen to form a gate structure. The tungsten oxide may not be formed on the gate structure so that generation of the whiskers may be suppressed. Thus, a short between adjacent wirings may not be generated.