Back-illuminated Sensor Boron Layer Defect Reduction
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Solution Overview
Problem
Conventional image sensors for detecting high-energy photons and charged particles in deep UV, vacuum UV, and extreme UV wavelengths face challenges such as reduced efficiency due to silicon dioxide layer defects, carbon buildup, and the inability to create large numbers of detector elements with high efficiency, leading to sensitivity loss and degradation over time.
Innovation Solution
The development of back-illuminated image sensors with a pure boron coating, which eliminates the need for metal interconnects on the front surface, allowing for increased sensitivity and longer lifespan by forming an epitaxial layer, gate layers, and circuit elements without metal, and depositing a thin pure boron layer on the back surface to enhance penetration and reduce surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional image sensors with silicon dioxide layers are used for detecting high-energy photons and charged particles, then the sensors can be manufactured with standard processes, but the quantum efficiency decreases due to defects and impurities in the silicon dioxide layer that absorb photons
Solution Approach 1:
The patent removes the silicon dioxide layer entirely from the sensor structure. By eliminating this defective layer that absorbs high-energy photons, the sensor achieves high quantum efficiency without the harmful absorption effects caused by defects and impurities in the oxide layer
Solution Approach 2:
The patent employs a composite structure consisting of a semiconductor substrate (such as silicon or silicon-germanium) combined with a protective coating layer. This composite design provides both the detection functionality of the semiconductor and the protection needed, without requiring the problematic silicon dioxide interface layer
2Ease of manufacture
If metal interconnects are used on the front surface of the sensor, then electrical connections can be established, but the number of detector elements that can be created with high efficiency is limited due to surface area occupation by metal structures
Solution Approach 1:
The patent inverts the conventional sensor architecture by placing metal interconnects and readout circuitry on the back surface of the semiconductor substrate rather than the front detection surface. This backside-illuminated design allows the front surface to be fully dedicated to photon detection, maximizing detector element density and efficiency
Solution Approach 2:
The patent moves electrical connection structures from the two-dimensional front surface plane to the three-dimensional back surface of the substrate. This spatial reorganization allows simultaneous high-density detector elements on the front surface and functional interconnects on the back surface without mutual interference
3Productivity
If sensors operate under high flux conditions for extended periods, then inspection productivity increases, but sensitivity degradation occurs due to carbon buildup and radiation damage
Solution Approach 1:
The patent changes the material parameters of the protective coating to use carbon-resistant materials that do not accumulate carbon under high-energy radiation. This parameter change in material composition prevents sensitivity degradation during extended high-flux operation
Solution Approach 2:
The patent applies a protective coating layer beforehand that serves as a barrier against carbon buildup and radiation-induced damage. This pre-applied protective layer cushions the sensor against degradation effects that would otherwise occur during prolonged high-flux inspection operations
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 solution results in high-quantum-efficiency image sensors capable of long-life operation under high flux conditions, maintaining sensitivity and reducing degradation, enabling better detection of DUV, VUV, and EUV radiation and charged particles with improved resolution and longer sensor lifetime.
Implementation Method 1
A pure boron layer is formed on the back surface of the semiconductor substrate. The boron layer enhances the sensor's ability to detect high-energy photons and charged particles by reducing surface defects and improving penetration
Implementation Method 2
The image sensor is capable of detecting high-energy photons and charged particles in the deep UV, vacuum UV, and extreme UV wavelength ranges. The boron layer facilitates charged particle detection by minimizing surface interference
Implementation Method 3
The circuit elements are formed in an epitaxial layer on a front surface of a semiconductor substrate. A pure boron layer is deposited on the back surface, eliminating the need for metal interconnects on the front surface
Implementation Method 4
An epitaxial layer is formed on the semiconductor substrate, providing a foundation for circuit elements that can be processed without metal contamination on the light-receiving surface
Data Source
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Figure 3A~3C
AI summary
An image sensor for short-wavelength light and charged particles includes a semiconductor membrane, circuit elements formed on one surface of the semiconductor membrane, and a pure boron layer on the other surface of the semiconductor membrane. This image sensor has high efficiency and good stability even under continuous use at high flux for multiple years. The image sensor may be fabricated using CCD (charge coupled device) or CMOS (complementary metal oxide semiconductor) technology. The image sensor may be a two-dimensional area sensor, or a one-dimensional array sensor. The image sensor can be included in an electron-bombarded image sensor and/or in an inspection system.