Semiconductor Trench Insulation Structure for Pixel Crosstalk Isolation
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Solution Overview
Problem
Existing methods for forming insulation structures in integrated circuits, particularly in image sensors, are inadequate in ensuring effective electrical and optical insulation between pixels and semiconductor areas, leading to potential crosstalk and mechanical stress issues during bonding processes.
Innovation Solution
A method involving the formation of trenches in a semiconductor substrate, filling with polysilicon, and subsequent metal filling after substrate transfer and bonding, which includes steps of forming electrically-insulating layers, deposition of polysilicon layers, and removal of sacrificial layers to create insulation structures that provide both electrical and optical insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal filling is performed before substrate transfer and bonding, then the insulation structure is formed early in the process, but contamination and mechanical stress risks increase during bonding
Solution Approach 1:
The trench filling with electrically insulating material is performed as a preliminary action before substrate transfer and bonding. This prepares the insulation structure in advance while avoiding metal filling at this stage, thus preventing contamination and mechanical stress issues during the subsequent bonding process.
Solution Approach 2:
The conventional sequence is inverted by performing substrate transfer and bonding before completing the metal filling of trenches. This reversal ensures that the bonding process occurs without the complications of present metal structures, eliminating contamination and stress risks, while the insulation function is still achieved through the electrically insulating material deposited earlier.
2Strength
If trenches are filled with metal early in the process, then the insulation structure is robust, but crosstalk between pixels may occur
Solution Approach 1:
Different materials with different properties are used in different regions of the trench. The electrically insulating material provides electrical insulation to prevent crosstalk, while metal is selectively deposited only in specific regions after bonding to provide mechanical strength and electrical connection where needed, thus achieving both insulation and structural requirements without crosstalk.
3Manufacturing precision
If polysilicon is deposited on trench walls before filling, then insulation quality is enhanced, but process complexity increases
Solution Approach 1:
The polysilicon deposition on trench walls is performed as a preliminary step before trench filling. This preliminary action ensures that the trench walls are properly coated with electrically insulating material to enhance insulation quality, while the overall process complexity is managed by integrating this step into the early fabrication sequence before substrate transfer and bonding.
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 method effectively reduces contamination and mechanical stress risks during bonding, enhances insulation quality, and prevents crosstalk between pixels by ensuring metal filling occurs after substrate transfer, thereby improving the structural integrity and performance of image sensors.
Implementation Method 1
a step of deposition of a polysilicon layer coating the lateral walls and the bottom of the trench
Implementation Method 2
a step of deposition of a polysilicon layer coating the lateral walls and the bottom of the trench
Implementation Method 3
a step of bonding of the first surface of the first substrate to a surface of a second substrate
Data Source
AI summary
A method of forming an insulation structure inside and on top of a first semiconductor substrate, including the steps of: a) forming a trench vertically extending in the first substrate from a first surface of the first substrate; b) filling the trench, from the first surface of the first substrate, with a polysilicon region; c) thinning the first substrate on the side of a second surface of the first substrate, opposite to the first surface, to expose the polysilicon region at the bottom of the trench; d) removing the polysilicon region from the second surface of the first substrate; and e) filling the trench, from the second surface of the first substrate, with a metal.