CMOS Image Sensor Micro Lens Resolution via DUV Photoresist
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Solution Overview
Problem
The existing methods for manufacturing CMOS image sensors face challenges in maintaining high resolution and uniformity of micro lenses due to the use of MUV photoresist, which results in increased micro lens size and reduced fill factor, leading to decreased photosensitivity and image quality.
Innovation Solution
The method involves forming a CMOS image sensor with micro lenses using a DUV photoresist material layer and a micro lens material layer, where the DUV photoresist layer is patterned and developed to improve resolution and linearity, and the micro lenses are formed with a gap of 50 nm or less between them, enhancing uniformity and photosensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MUV photoresist is used to form micro lenses, then the manufacturing process is simpler, but the resolution and uniformity of micro lenses deteriorate
Solution Approach 1:
The patent changes the wavelength parameter of the photoresist from MUV (middle ultraviolet) to DUV (deep ultraviolet). This parameter change enables higher resolution patterning with better linearity, allowing micro lenses to be formed with uniform sizes and smaller gaps (50 nm or less) while maintaining manufacturing feasibility through standard photolithography processes.
2Volume of moving object
If pixel size is reduced, then the image sensor can be miniaturized, but the fill factor of light sensing portion decreases
Solution Approach 1:
The patent forms micro lenses with curved (spheroidal) surfaces over the color filters. This curvature allows the micro lenses to efficiently focus incident light onto the photodiode active area. By improving the focusing capability through proper curvature, the fill factor effect is enhanced, allowing more light to be concentrated on the light sensing portion even as pixel size decreases.
3Manufacturing precision
If micro lens gap is increased, then manufacturing uniformity is easier to achieve, but light focusing efficiency and photosensitivity reduce
Solution Approach 1:
The patent reduces the gap parameter between adjacent micro lenses to 50 nm or less. This parameter change is achieved through improved photolithography using DUV photoresist, which provides better resolution and linearity control. The smaller gap enhances light focusing efficiency and photosensitivity while the advanced photoresist technology ensures that uniformity is maintained despite the reduced spacing.
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 results in improved resolution and uniformity of micro lenses, maintaining high photosensitivity and image quality by overcoming the limitations of MUV photoresist usage, allowing for more efficient light focusing and better photoelectric conversion.
Implementation Method 1
a first material layer is formed over the second planarization layer. Next, a second material layer is formed over the first material layer. Then, a micro lens is formed out of the first and second material layers
Implementation Method 2
a focusing technology has been developed that changes a path of light incident on regions other than the light sensing portion and focuses the incident light on the light sensing portion
Implementation Method 3
CMOS image sensors employ a switching way for forming MOS transistors corresponding to a quantity of unit pixels in a semiconductor substrate
Data Source
AI summary
A Complementary Metal Oxide Semiconductor (CMOS) image sensor and methods for fabricating the same. In one example embodiment of the invention, a method for manufacturing a Complementary Metal Oxide Semiconductor (CMOS) image sensor includes several acts. First, a metal pad is formed over a semiconductor substrate. Next, a protection film is formed over the semiconductor substrate and the metal pad. Then, the protection film is selectively removed to expose a surface of the metal pad. Next, a first planarization film is formed over the protection film. Then, a color filter layer is formed over the first planarization film. Next, a second planarization layer is formed over the color filter layer. Then, a first material layer is formed over the second planarization layer. Next, a second material layer is formed over the first material layer. Then, a micro lens is formed out of the first and second material layers.