CMOS Image Sensor Microlens Trench for Uniform Photoresist Coating
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Solution Overview
Problem
Conventional CMOS image sensor manufacturing methods result in non-uniform photoresist layer coating due to vertical profiles of interlayer dielectric and passivation layers, leading to striation and increased light path to photodiodes, which affects photosensitivity.
Innovation Solution
A CMOS image sensor with a trench formed in the interlayer dielectric and an insulating layer sidewall at a 40-70 degree slope, reducing the light path to photodiodes and ensuring uniform photoresist layer coating by forming microlenses within the trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a vertical profile interlayer dielectric and passivation layer are used, then the manufacturing process is simple, but the photoresist layer coating becomes non-uniform causing striation
Solution Approach 1:
The patent applies curvature by forming the sidewall of the interlayer dielectric with a predetermined slope (40-70 degrees) instead of a vertical profile. This curved sidewall allows the photoresist layer to coat uniformly without striation, while the microlens formed within the trench maintains its optical function. The sloped sidewall creates a gradual transition that prevents coating defects.
2Device complexity
If a vertical profile interlayer dielectric is used, then the device structure is simple, but the light path to photodiodes is increased reducing photosensitivity
Solution Approach 1:
The patent introduces a dimensional change by forming a trench with a sloped sidewall in the interlayer dielectric layer. This creates a three-dimensional structure that reduces the light path length to the photodiodes while maintaining structural integrity. The trench configuration allows light to reach the photodiode more directly, improving photosensitivity without significantly complicating the overall device structure.
3Reliability
If the light path to photodiodes is reduced, then photosensitivity is improved, but the photoresist coating uniformity becomes difficult to maintain
Solution Approach 1:
The sloped sidewall (40-70 degrees) of the trench creates a curved surface that enables uniform photoresist coating. This curvature prevents the vertical profile problem that causes striation, while the trench structure simultaneously reduces the light path to the photodiodes. The specific angle range optimizes both coating uniformity and light efficiency.
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 enhances light efficiency by reducing the light path to photodiodes and prevents striation during photoresist layer coating, resulting in improved photosensitivity and uniform microlens formation.
Implementation Method 1
form a microlens at an upper portion thereof, and to receive more light in a photodiode region
Implementation Method 2
the CMOS image sensor is composed of a photodiodes for sensing light and a CMOS logic circuit for processing the sensed light into electric signals
Data Source
AI summary
A CMOS image sensor and a method for manufacturing the same are provided. The CMOS image sensor may be capable of improved thickness uniformity form microlenses formed at a reduced distance from the photodiodes. The CMOS image sensor can include: a semiconductor substrate on which a pixel array is formed, the pixel array including photodiodes formed on the semiconductor substrate to different depths for sensing red, green, and blue signals, respectively; an interlayer dielectric formed on the semiconductor substrate and having a trench at an upper portion of the pixel array; an insulating layer sidewall formed at a side of the trench; and a plurality of microlenses formed on the interlayer dielectric in the trench at predetermined intervals.