Crystalline Protective Polysilicon Layer to Prevent Recrystallization Voids
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Solution Overview
Problem
Polysilicon layers deposited at 540-560°C are amorphous and recrystallize at higher processing temperatures, leading to increased grain size and formation of defective voids, making semiconductor layers and devices susceptible to process damages.
Innovation Solution
A method involving the deposition of polysilicon layers at 600-700°C for initial layers, followed by a lower temperature deposition of 540-560°C for protective layers to prevent recrystallization and void formation, using a specific sequence of dielectric and polysilicon layer deposition and patterning steps to form semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polysilicon layers are deposited at 540-560°C, then deposition cost and time are reduced, but the layers recrystallize at higher processing temperatures causing grain size increase and void formation
Solution Approach 1:
The patent applies preliminary action by depositing a first polysilicon layer at a higher temperature (600-700°C) before the main polysilicon layer. This initial layer is deposited in advance to establish a stable, non-recrystallizing foundation that prevents void formation during subsequent high-temperature processing, thereby solving the reliability issue while maintaining productivity
Solution Approach 2:
The patent changes the deposition temperature parameter for the first polysilicon layer to 600-700°C, which is higher than the conventional 540-560°C. This parameter change ensures the first layer remains inert to recrystallization at processing temperatures, preventing grain boundary void formation while maintaining overall process efficiency
2Productivity
If polysilicon layers are processed at higher temperatures, then device fabrication is completed, but recrystallization causes increased grain size and defective voids
Solution Approach 1:
The first polysilicon layer is deposited preliminarily at 600-700°C to create a stable, non-recrystallizing barrier layer before the main device fabrication processes. This preliminary structure prevents quality degradation during subsequent high-temperature processing steps
Solution Approach 2:
The first polysilicon layer acts as an intermediary protective barrier between the processing environment and the main polysilicon layer. It mediates the interaction by absorbing thermal stress and preventing direct heat-induced recrystallization of the main layer, thereby maintaining manufacturing precision
3Productivity
If amorphous polysilicon layers are used, then deposition is faster and cheaper, but they are susceptible to process damages from plasma and etching
Solution Approach 1:
A crystalline first polysilicon layer is deposited preliminarily at 600-700°C to create a damage-resistant protective layer before the amorphous main polysilicon layer. This preliminary crystalline structure provides resistance to plasma and etching damage while allowing the main layer to be deposited quickly at lower temperatures
Solution Approach 2:
The patent creates a composite structure with a crystalline first polysilicon layer (600-700°C deposition) and an amorphous main polysilicon layer (540-560°C deposition). The crystalline component provides damage resistance while the amorphous component maintains deposition efficiency, achieving both productivity and harm resistance
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 effectively protects semiconductor layers and devices from process damages by preventing recrystallization and void formation, reducing defects and improving the reliability of semiconductor devices.
Implementation Method 1
a first polysilicon layer is deposited on the substrate under a first deposition condition, wherein the first deposition condition comprises a first temperature in a range of 600-700 degree Celsius
Implementation Method 2
a second polysilicon layer is deposited on the first polysilicon layer under a second deposition condition, wherein the second deposition condition comprises a second temperature in a range of 540-560 degree Celsius
Data Source
AI summary
Disclosed is a method for forming a crystalline protective polysilicon layer which does not create defective voids during subsequent processes so as to provide effective protection to devices underneath. In one embodiment, a method for forming a semiconductor device, includes: depositing a protective coating on a first polysilicon layer; forming an epitaxial layer on the protective coating; and depositing a second polysilicon layer over the epitaxial layer, wherein the protective coating comprises a third polysilicon layer, wherein the third polysilicon layer is deposited at a first temperature in a range of 600-700 degree Celsius, and wherein the third polysilicon layer in the protect coating is configured to protect the first polysilicon layer when the second polysilicon layer is etched.