Lateral PNP Transistor Base Region Molybdenum Diffusion
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Solution Overview
Problem
Conventional semiconductor devices face issues with deteriorated breakdown voltage characteristics and increased device size due to high impurity concentrations in the base region of lateral PNP transistors, and metallic contamination affects current-amplification factor variability during manufacturing.
Innovation Solution
Molybdenum (Mo) is diffused into the semiconductor layer as the base region, allowing for adjustment of the current-amplification factor without increasing device size and reducing variability caused by metallic contamination through a manufacturing method involving a molybdenum-containing solution and thermal diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first N type impurity region as the base region is formed with high impurity concentration (two to three times higher than the N type epitaxial region), then the current-amplification factor of the lateral PNP transistor is stabilized, but the breakdown voltage characteristic is deteriorated
Solution Approach 1:
The patent applies local quality by introducing molybdenum diffusion specifically in the base region (N type epitaxial region) rather than uniformly across the entire device. This localized modification allows the base region to have different electrical properties (controlled current-amplification factor through molybdenum-induced recombination centers) while the collector region maintains its original high breakdown voltage characteristics. The molybdenum diffusion is confined to where it is needed to adjust transistor parameters without compromising overall device performance.
Solution Approach 2:
The patent changes the physical-chemical parameters of the base region by diffusing molybdenum atoms into the N type epitaxial region. This introduces recombination centers that modify the carrier lifetime and current-amplification factor. By controlling the molybdenum diffusion conditions (temperature, time, concentration), the current-amplification factor can be precisely adjusted to desired levels without requiring high impurity concentrations that would harm breakdown voltage.
2Reliability
If the first N type impurity region as the base region is formed with high impurity concentration, then the current-amplification factor is stabilized, but the device size increases
Solution Approach 1:
The patent uses local quality by applying molybdenum diffusion treatment specifically to the base region where it is needed to control current amplification, rather than increasing the physical dimensions of the device. This localized parameter modification allows achieving stable current-amplification factor without expanding the overall device footprint, maintaining compact device size while improving electrical characteristics.
3Ease of operation
If platinum (Pt) is used as a lifetime killer substance in the diffusion-source film, then the current-amplification factor can be controlled, but metallic contamination increases variability in the current-amplification factor
Solution Approach 1:
The patent replaces platinum (a precious, expensive metal) with molybdenum (a more abundant, cheaper metal) as the lifetime killer substance in the diffusion-source film. Molybdenum provides the same functional effect of controlling carrier lifetime and current-amplification factor, but with better manufacturing precision and reduced variability. The molybdenum diffusion-source film can be applied using standard semiconductor manufacturing techniques, providing cost-effective and reliable parameter control.
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 diffusion of molybdenum into the semiconductor layer reduces the current-amplification factor to a desired level, prevents breakdown voltage deterioration, and minimizes device size, while also reducing variability in the current-amplification factor and avoiding increases in specific resistance.
Implementation Method 1
molybdenum (Mo) is diffused in the semiconductor layer (3) used as a base region
Implementation Method 2
the boron (B) and platinum (Pt) are diffused from the diffusion-source film into the substrate by heat treatment at 1000° C. to 1050° C. in a non-oxidation atmosphere
Data Source
AI summary
A conventional semiconductor device, for example, a lateral PNP transistor has a problem that it is difficult to obtain a desired current-amplification factor while maintaining a breakdown voltage characteristic without increasing the device size. In a semiconductor device, that is a lateral PNP transistor, according to the present invention, an N type epitaxial layer is formed on a P type single crystal silicon substrate. The epitaxial layer is used as a base region. Moreover, molybdenum (Mo) is diffused in the substrate and the epitaxial layer. With this structure, the base current is adjusted, and thereby a desired current-amplification factor (hFE) of the lateral PNP transistor is achieved.