P-type Polysilicon Layer Formation via Atomic Layer Deposition
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Solution Overview
Problem
The existing methods for forming a P-type polysilicon layer in semiconductor devices face challenges in achieving precise boron concentration due to the volatility of boron, especially when the thickness of the P-type polysilicon layer is reduced.
Innovation Solution
The method involves alternately depositing silicon atom layers and group IIIA element atom layers by atomic layer deposition, followed by a heat treatment process to diffuse the group IIIA elements into the silicon layers, forming a stable P-type polysilicon layer with controlled resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of the P-type polysilicon layer is reduced, then the device performance is improved, but the boron concentration cannot be precisely obtained due to boron volatility
Solution Approach 1:
The patent divides the polysilicon layer formation into multiple thin alternating layers of silicon and group IIIA elements (Al, Ga, In, Tl) deposited by atomic layer deposition. Each layer is deposited to a controlled thickness (silicon: 5-100 Å, group IIIA: 5-50 Å), allowing precise control of dopant concentration even in thin layers. The segmented structure enables better control of boron diffusion and reduces volatility issues.
Solution Approach 2:
The patent changes the deposition parameters by using atomic layer deposition instead of conventional methods, controlling each atomic layer thickness precisely. The heat treatment parameters are also optimized (temperature: 600-900°C, time: 1-60 minutes) to control boron diffusion while preventing excessive volatility. This parameter control enables precise dopant concentration in thin layers.
2Ease of manufacture
If conventional doping processes are used, then the process is simple, but the boron concentration precision deteriorates due to boron volatility
Solution Approach 1:
The patent replaces the conventional thermal diffusion or ion implantation doping processes with atomic layer deposition followed by heat treatment. This substitution allows for atomic-level precision in controlling dopant concentration while maintaining a relatively simple process flow. The ALD process provides precise thickness control of each layer, translating to precise dopant concentration control.
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 allows for the precise formation of a P-type polysilicon layer with stable resistivity, even when the layer is thin, by controlling the thickness of the deposited layers and the heat treatment process, ensuring consistent dopant concentration.
Implementation Method 1
forming a P-type polysilicon layer by diffusing the plurality of group IIIA element atom layers into the plurality of silicon atom layers
Implementation Method 2
a gate stack is formed by alternately depositing a plurality of silicon atom layers and a plurality of group IIIA element atom layers on the gate insulating layer by atomic layer deposition
Data Source
AI summary
A P-type polysilicon layer having a stable and desired resistivity is formed by alternately depositing a plurality of silicon atom layers and a plurality of group IIIA element atom layers on a semiconductor substrate by atomic layer deposition, and thereafter forming a P-type polysilicon layer by thermally diffusing the plurality of group IIIA element atom layers into the plurality of silicon atom layers. The plurality of group IIIA element atom layers may comprise Al, Ga, In, and/or Tl.