SiC Device Polysilicon Electrode Step Coverage
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Solution Overview
Problem
Existing silicon carbide semiconductor devices face challenges in improving the breakdown voltage of interlayer insulating films due to suboptimal step coverage and dielectric strength, particularly when using plasma CVD and reflow processing, which can degrade the silicon carbide and gate insulating film interface, and isotropic dry etching methods are ineffective for silicon carbide substrates.
Innovation Solution
A silicon carbide semiconductor device with polysilicon electrodes doped with N, P, As, Sb, B, Al, and Ar, featuring a first inclination angle of 60° or lower and a second inclination angle of 100° or greater, is manufactured using ion implantation and isotropic dry etching, with controlled dopant concentration and temperature to enhance step coverage and dielectric strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma CVD is used to form the interlayer insulating film, then the film can be deposited, but the film overhangs along the periphery of the polysilicon electrode forming a V-shaped depression, degrading dielectric strength
Solution Approach 1:
The patent changes the inclination angle parameter of the polysilicon electrode side face from the conventional steep angle to specifically 60° or lower. This parameter change in the electrode geometry fundamentally alters how the interlayer insulating film deposits, enabling it to cover the step properly without forming overhangs or V-shaped depressions, thus improving both step coverage shape and dielectric strength
Solution Approach 2:
The patent performs preliminary action by pre-forming the polysilicon electrode with a controlled inclination angle of 60° or lower before depositing the interlayer insulating film. This preliminary shaping of the electrode ensures that subsequent film deposition proceeds with proper step coverage, preventing the formation of harmful V-shaped depressions and eliminating the need for post-deposition reflow processing
2Manufacturing precision
If reflow processing is performed at 930°C to smooth the step coverage, then the step shape is improved, but the silicon carbide and gate insulating film interface deteriorates
Solution Approach 1:
The patent performs preliminary action by pre-forming the polysilicon electrode with a controlled inclination angle of 60° or lower before depositing the interlayer insulating film. This preliminary shaping of the electrode ensures that subsequent film deposition proceeds with proper step coverage, preventing the formation of harmful V-shaped depressions and eliminating the need for post-deposition reflow processing
Solution Approach 2:
The patent extracts and eliminates the reflow processing step from the manufacturing process. By changing the electrode inclination angle to 60° or lower, the patent removes the requirement for high-temperature reflow processing, thereby avoiding the deterioration of the silicon carbide and gate insulating film interface that occurs during such processing
3Manufacturing precision
If isotropic dry etching is performed at 50-100°C to incline the polysilicon electrode side face, then the step coverage is improved for silicon substrates, but the method is ineffective for silicon carbide substrates with maximum inclination angle of 68°
Solution Approach 1:
The patent changes the inclination angle parameter from the conventional steep angle to specifically 60° or lower, which is achievable on silicon carbide substrates through controlled isotropic dry etching. This parameter change enables proper step coverage while maintaining substrate compatibility
Solution Approach 2:
The patent applies local quality by selectively doping the polysilicon electrode with specific dopants (B, Al, or Ar) at controlled concentrations (1×10^14 to 1×10^21 atoms/cm²). This local modification of the polysilicon electrode properties enables effective isotropic dry etching to achieve the desired 60° or lower inclination angle on silicon carbide substrates
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 approach improves the step coverage shape of the interlayer insulating film, reduces electric field concentration, and enhances dielectric strength without compromising electrical characteristics, achieving better performance than conventional methods.
Implementation Method 1
The polysilicon electrode contains one or two or more dopants selected from N, P, As, Sb, B, Al, and Ar
Implementation Method 2
isotropic dry etching, with controlled dopant concentration and temperature to enhance step coverage and dielectric strength
Implementation Method 3
If plasma CVD (chemical vapor deposition) is used to form the interlayer insulating film
Data Source
AI summary
The present invention provides a process for producing a semiconductor device having a breakdown voltage heightened by improving the step coverage properties of the interlayer dielectric for covering polysilicon electrodes. The process includes a step in which a gate insulating film is formed on a silicon carbide substrate, a step in which a polysilicon film is formed on the gate insulating film, a step in which one or more dopants of N, P, As, Sb, B, Al, and Ar are ion implanted into the polysilicon film, and a step in which a mask is selectively formed on the polysilicon film. The exposed portions of the polysilicon film are removed by isotropic dry etching. Thus, polysilicon electrodes can be formed so that in each polysilicon electrode, the hem part sandwiched between the bottom surface and the lateral surface of the polysilicon electrode has an inclination angle of 60° or less.