UBM Electrode Structure for Radiation Detectors
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Solution Overview
Problem
Conventional UBM electrode structures for CdTe-based radiation detectors face issues with peeling due to insufficient adhesion between the semiconductor and the Pt layer, particularly during solder jointing and signal line bonding, leading to poor electrode adhesion and reliability.
Innovation Solution
The UBM electrode structure for radiation detectors incorporates a Pt electrode layer with enhanced adhesion (>0.5 N/cm) on a CdTe or CdZnTe substrate, featuring a Ni layer and an Au layer, formed using electroless plating and specific cleaning processes to minimize oxygen content and improve substrate wettability, ensuring strong bonding and preventing peeling during manufacturing and bonding processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Pt electrode layer is formed on a CdTe-based substrate using conventional methods (vacuum deposition or plating), then the electrode can be formed on the substrate surface, but adhesion between the Pt layer and substrate is insufficient causing peeling during solder jointing and signal line bonding
Solution Approach 1:
The patent applies preliminary action by performing specific surface cleaning treatments (acetone cleaning, alcohol cleaning) and oxygen plasma treatment before forming the Pt electrode layer. These preliminary steps remove organic contaminants and reduce oxygen content on the substrate surface, creating an optimal surface state that ensures strong adhesion of the subsequent Pt layer, preventing peeling during later solder jointing and bonding processes
Solution Approach 2:
The patent applies parameter changes by controlling the oxygen content on the substrate surface to be 40 at% or less through cleaning and plasma treatment. It also optimizes the Pt layer thickness to 50-100 nm and controls the deposition conditions (substrate temperature 50-150°C, deposition rate 0.01-0.1 nm/s). These parameter optimizations ensure sufficient adhesion strength while preventing peeling during subsequent processing
2Reliability
If a thick Ni layer and thin Au layer are formed above the Pt electrode to prevent solder permeation, then solder protection is improved, but the complexity of the electrode structure increases
Solution Approach 1:
The patent applies segmentation by dividing the electrode structure into multiple functional layers: a Pt layer (50-100 nm) for adhesion and electrical contact, a Ni layer (50-200 nm) for solder barrier and structural support, and an Au layer (10-50 nm) for wire bonding compatibility. Each layer performs a specific function, creating a segmented structure that provides comprehensive protection while maintaining manufacturability
Solution Approach 2:
The patent applies composite materials by combining Pt, Ni, and Au layers to create a multi-material electrode structure. The Pt layer provides adhesion to the CdTe substrate, the Ni layer provides solder resistance and mechanical strength, and the Au layer provides compatibility with wire bonding processes. This composite structure leverages the complementary properties of different materials to achieve multiple functions simultaneously
3Ease of manufacture
If conventional cleaning methods are used before Pt deposition, then the substrate surface is prepared, but oxygen content remains high causing insufficient adhesion and peeling
Solution Approach 1:
The patent applies inert atmosphere by using oxygen plasma treatment and performing deposition in a controlled vacuum environment. The oxygen plasma treatment removes adsorbed gases and organic contaminants while the vacuum deposition environment prevents re-contamination, maintaining a clean, low-oxygen surface state that ensures strong Pt layer adhesion
Solution Approach 2:
The patent replaces conventional mechanical cleaning methods with chemical and plasma-based cleaning. Instead of physical abrasion or simple solvent wiping, the patent uses acetone and alcohol ultrasonic cleaning followed by oxygen plasma treatment, which more effectively removes contaminants and reduces surface oxygen content, resulting in superior adhesion
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 provides a radiation detector with high electrode adhesion, preventing peeling during UBM structure formation, solder jointing, and signal line bonding, thereby enhancing the reliability and performance of the detector.
Implementation Method 1
a means such as plating or sputtering is used in the formation of a Pt layer and UBM structure
Implementation Method 2
specific cleaning processes to minimize oxygen content and improve substrate wettability
Implementation Method 3
adhesion between a CdTe-based semiconductor and the Pt layer is insufficient, and even when formed, peeling of the electrode sometimes occurs
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
An UBM electrode structure body for a radiation detector and a radiation detector arranged with the UBM electrode structure body are provided for suppressing peeling and having high electrode adhesion. In addition, a manufacturing method of an UBM electrode structure body for a radiation detector and a manufacturing method of a radiation detector using the UBM electrode structure body are provided in which peeling does not occur during UBM structure formation, a solder bonding process or bonding of a signal line to a Pt layer. The UBM electrode structure body for a radiation detector of the present invention is arranged with a CdTe substrate or CdZnTe substrate and a Pt electrode layer arranged on the CdTe substrate or CdZnTe substrate, adhesion of the Pt electrode layer with respect to the CdTe substrate or the CdZnTe substrate being 0.5 N/cm or more.