Pixel Isolation Film Polysilicon Composition to Prevent Seams and Voids
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image sensors face performance issues due to the formation of seams and voids in the buried conductive layer within pixel trenches, which can lead to increased dark current and noise levels, particularly during heat treatment processes.
Innovation Solution
Incorporating polysilicon with fining elements such as oxygen, carbon, or fluorine into the buried conductive layer, which helps maintain a small grain size and prevents grain growth or coalescence, thereby avoiding the formation of seams and voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon is used in the buried conductive layer without a fining element, then the manufacturing process is simpler, but voids and seams form during manufacturing leading to increased noise and dark current
Solution Approach 1:
The patent changes the chemical composition parameters of the polysilicon by incorporating fining elements (oxygen, carbon, or fluorine) at specific concentrations (0.1-20 atomic percent). This parameter modification prevents void and seam formation during the buried conductive layer manufacturing process, thereby improving image sensor performance by reducing noise and dark current while maintaining manufacturing feasibility
Solution Approach 2:
The patent creates a composite material structure by combining polysilicon with fining elements to form a modified polysilicon composition. This composite approach, where the fining element acts as an additive within the polysilicon matrix, prevents defects during deposition while maintaining the electrical conductivity function of the buried conductive layer
2Object-affected harmful factors
If the polysilicon grain size is allowed to grow, then the manufacturing process is easier, but grains coalesce forming voids that increase noise levels
Solution Approach 1:
The patent implements precise control of polysilicon grain size by incorporating fining elements that act as grain growth inhibitors. The fining element concentration (0.1-20 atomic percent) is optimized to maintain small grain sizes throughout the manufacturing process, preventing grain coalescence and void formation while keeping the manufacturing process manageable
Solution Approach 2:
The patent employs feedback mechanisms during the manufacturing process to monitor and control grain size development. By adjusting process parameters based on observed grain growth trends and maintaining appropriate fining element concentrations, the system prevents grain coalescence before voids can form, thereby controlling noise levels
3Productivity
If the buried conductive layer is deposited without fining elements, then the deposition process is faster, but seams form increasing dark current
Solution Approach 1:
The patent modifies the deposition parameters by incorporating fining elements into the polysilicon composition. This composition modification prevents seam formation during the buried conductive layer deposition process, reducing dark current generation while maintaining deposition efficiency through optimized process conditions
Solution Approach 2:
The fining element acts as an intermediary substance within the polysilicon matrix that prevents direct contact and bonding between polysilicon grains that would otherwise form seams. This intermediary role of the fining element (oxygen, carbon, or fluorine) blocks defect formation during deposition, reducing dark current without significantly impacting deposition speed
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 solution effectively prevents the formation of seams and voids in the buried conductive layer, enhancing the image sensor's performance by reducing dark current and noise levels, and ensuring improved reliability.
Implementation Method 1
the buried conductive layer includes polysilicon containing a fining element at a first concentration, and the fining element includes oxygen, carbon, or fluorine
Data Source
AI summary
An image sensor including a semiconductor substrate having a first surface and a second surface; and a pixel isolation film extending from the first surface of the semiconductor substrate into the semiconductor substrate and defining active pixels in the semiconductor substrate, wherein the pixel isolation film includes a buried conductive layer including polysilicon containing a fining element at a first concentration; and an insulating liner between the buried conductive layer and the semiconductor substrate, and wherein the fining element includes oxygen, carbon, or fluorine.