Polysilicon Film Grain Size Control via Adjusting Gas
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Solution Overview
Problem
Conventional methods for forming poly-silicon films doped with phosphorous or boron have limitations in achieving fine crystal grains, which hinder micro-fabrication due to a lower limit of crystal grain size of about 300 nm.
Innovation Solution
A poly-silicon film formation method involving the use of a silicon film formation gas, a doping gas, and a grain size adjusting gas containing C2H4, N2O, or NO to retard columnar crystal formation and promote miniaturization, with specific flow rates and temperature conditions to deposit and anneal amorphous silicon films into poly-silicon films with fine crystal grains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional low-pressure CVD is used to form poly-silicon film, then the film can be formed with good controllability, but the crystal grain size cannot be reduced below about 300 nm
Solution Approach 1:
The patent introduces a grain size adjusting gas (C2H4, N2O, or NO) into the reaction chamber during CVD processing. This gas reacts with silicon to form Si-C, Si-N, or Si-O bonds that inhibit columnar crystal growth and promote fine grain formation. By changing the chemical composition parameters of the reaction atmosphere, the patent achieves crystal grain sizes of 100 nm or less while maintaining the simplicity of the CVD process
Solution Approach 2:
The grain size adjusting gas acts as an intermediary substance that mediates between the silicon film formation and the crystal growth process. The C2H4, N2O, or NO gas molecules interact with the depositing silicon atoms to form compound bonds (Si-C, Si-N, Si-O) that disrupt the formation of large columnar crystals, thereby controlling the crystal grain size without requiring additional processing steps
2Reliability
If ion implantation is used to dope poly-silicon film, then doping can be achieved, but damage is generated to the target substrate
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical vapor deposition process. Instead of physically bombarding the substrate with ions, the doping elements are introduced through gaseous precursors that deposit and incorporate into the silicon film during CVD. This substitution eliminates mechanical damage to the substrate while achieving uniform doping through controlled chemical reactions
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 method achieves poly-silicon films with crystal grains of 100 nm or less, facilitating improved micro-fabrication capabilities in semiconductor devices by forming Si-C, Si-N, and Si-O bonds that retard columnar crystal growth and promote random, miniaturized crystal formation.
Implementation Method 1
forming Si-C, Si-N, and Si-O bonds that retard columnar crystal growth and promote random, miniaturized crystal formation
Implementation Method 2
performing a heat process on the amorphous silicon film, while setting the interior of the reaction container accommodating a target substrate at a second pressure higher than the first pressure and a second temperature of 550 to 1,100° C. and higher than the first temperature, thereby transforming the amorphous silicon film into a poly-silicon film
Implementation Method 3
transforming the amorphous silicon film into a poly-silicon film
Implementation Method 4
depositing a silicon film doped with phosphorous or boron on the target substrate
Data Source
AI summary
A poly-silicon film formation method for forming a poly-silicon film doped with phosphorous or boron includes heating a target substrate placed in a vacuum atmosphere inside a reaction container, and supplying into the reaction container a silicon film formation gas, a doping gas for doping a film with phosphorous or boron, and a grain size adjusting gas containing a component to retard columnar crystal formation from a poly-silicon crystal and to promote miniaturization of the poly-silicon crystal, thereby depositing a silicon film doped with phosphorous or boron on the target substrate.