FinFET Fin Sidewall Smoothing for Low LER and LWR
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Solution Overview
Problem
Conventional FinFET manufacturing processes result in high line edge roughness (LER) and line width roughness (LWR) due to incomplete breaking of organic molecular chains of photoresist, leading to defects and impurities on the fin surface, which increase interface state density and degrade device performance.
Innovation Solution
A method involving epitaxial growth of a semiconductor layer, followed by spacer transfer etching, ozone oxidation to form a thin oxide film, and atomic layer etching to smooth the fin surface, repeated multiple times to achieve a thickness less than 0.7 nm, using HF as a reaction gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a self-aligned multiple-exposure process is used to manufacture fins, then the fin structure can be formed, but the organic molecular chains of photoresist fail to break completely resulting in high line edge roughness (LER) and high line width roughness (LWR)
Solution Approach 1:
The method applies preliminary actions by performing multiple rounds of oxidation and atomic layer etching before final fin formation. Each round of oxidation creates a thin oxide layer that is then precisely removed by atomic layer etching, progressively smoothing the fin surface and reducing LER and LWR before the fin structure is completed
Solution Approach 2:
The method changes physical and chemical parameters by controlling oxidation conditions (ozone exposure) and etching parameters (atomic layer etching cycles) to precisely adjust the fin surface morphology. By varying the number of oxidation-etching cycles and controlling the thickness of oxide layers formed, the surface roughness parameters LER and LWR are systematically reduced
2Reliability
If the fin surface is rough with defects and impurities, then the fin structure is formed, but local energy levels are created near the interface that capture and ionize electrons resulting in high interface state density Dit
Solution Approach 1:
The method performs preliminary surface treatment through multiple oxidation and atomic layer etching cycles before device fabrication. This preliminary action removes surface defects and impurities that would otherwise create interface states, ensuring a clean fin surface that reduces electron capture and ionization events at the interface
Solution Approach 2:
The method converts the potentially harmful oxidation process into a beneficial one by using controlled oxidation to create thin oxide layers that are then precisely removed by atomic layer etching. This process, when applied repeatedly, transforms surface roughness and defects into a smooth, clean surface that reduces interface state density and improves device reliability
3Ease of manufacture
If conventional etching methods are used to form fins, then the manufacturing process is simpler, but the line edge roughness and line width roughness remain high
Solution Approach 1:
The method segments the fin formation process into multiple discrete stages, each consisting of oxidation followed by atomic layer etching. Instead of using a single complex etching step, the process is divided into multiple simpler, repeatable cycles that collectively achieve superior surface precision while maintaining manufacturing feasibility
Solution Approach 2:
The method employs periodic action by repeating the oxidation and atomic layer etching cycles multiple times. Each cycle contributes to progressive surface smoothing and dimension precision improvement, with the periodic repetition of these controlled steps enabling high precision fin formation without excessive process complexity
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
Reduces LER and LWR by 67.4% and 61.3%, respectively, improving surface smoothness and reducing interface state density, enhancing carrier mobility and device performance without high-temperature damage.
Implementation Method 1
oxidizing a sidewall of the fin-shaped portion with ozone, so as to form an oxide film on the sidewall
Implementation Method 2
etching the oxide film by using an atomic layer etching method, so as to remove the oxide film
Implementation Method 3
a reaction gas used in the atomic layer etching method includes HF
Data Source
AI summary
The present disclosure relates to a method of manufacturing a fin in a transistor and a method of manufacturing a fin field effect transistor. The method of manufacturing the fin in the transistor includes: epitaxially growing a semiconductor layer on a substrate; etching the semiconductor layer into a fin-shaped portion by using a spacer transfer technique; oxidizing a sidewall of the fin-shaped portion with ozone, so as to form an oxide film on the sidewall; and etching the oxide film by using an atomic layer etching method, so as to remove the oxide film.