Reducing Photolithography Steps in CMOS Image Sensor Fabrication
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Solution Overview
Problem
The high number of photolithography steps required in manufacturing CMOS image sensors leads to substantial manufacturing costs and cycle times, necessitating a cost-effective reduction in the process without compromising device performance.
Innovation Solution
A process involving blanket implants and reduced mask layers is implemented, where a first-type semiconductor substrate is implanted with a second-type blanket layer, followed by mask-defined wells and isolations, allowing for fewer photolithography steps and compensatory implants to form a CMOS image sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photolithography steps are used to define different regions and structures, then device performance and precision are maintained, but manufacturing cost and cycle time increase substantially
Solution Approach 1:
The patent combines multiple photolithography steps into a single photolithography process by using a unified mask pattern that defines both pixel regions and logic regions. This merging approach maintains the precision needed for device performance while substantially reducing manufacturing cost and cycle time by eliminating redundant photolithography cycles.
Solution Approach 2:
The single photolithography mask serves multiple functions by simultaneously defining pixel regions, logic regions, and various structural features. This multi-functional approach allows one photolithography step to accomplish what traditionally required multiple separate steps, thereby reducing overall process complexity and cost.
2Productivity
If the number of photolithography steps is reduced to lower manufacturing cost, then productivity improves, but device performance may be degraded
Solution Approach 1:
The patent merges the definition of multiple device regions into a single photolithography mask, allowing cost reduction through fewer process steps while maintaining performance through careful mask design that preserves all necessary structural definitions in one patterning operation.
Solution Approach 2:
The patent transitions from multiple sequential photolithography steps (time dimension) to a single spatially optimized mask design that accomplishes the same patterning goals. This dimensional shift from temporal to spatial optimization maintains precision while improving productivity.
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 reduces manufacturing costs and cycle time while maintaining device performance by minimizing the number of photolithography processes and mask layers, enabling a more efficient production method.
Implementation Method 1
The semiconductor substrate is second-type blanket implanted to form a second-type implant layer therein
Data Source
AI summary
A process of forming a semiconductor device includes second-type blanket implanting a first-type semiconductor substrate to form a second-type implant layer therein; second-type implanting the semiconductor substrate through a first mask to form second-type wells in a second region of the semiconductor substrate; and first-type implanting the semiconductor substrate through a second mask to form isolations in a first region of the semiconductor substrate and to compensate complementary sub-regions of the second region.