Super-β Bipolar Transistor Base Doping for Punch-Through Resistance
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Solution Overview
Problem
Existing bipolar junction transistors face a high risk of base region punch-through and low current gain due to shallow base regions and uniform base region concentration, leading to leakage currents and reduced efficiency.
Innovation Solution
A super-β bipolar junction transistor is manufactured with a doped island of higher doping concentration on the peripheral side of the base region, forming a concentration gradient that reduces recombination and prevents punch-through, while maintaining sufficient base transport factor and increasing common emitter current gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the base region is made shallow to improve switching speed, then the switching speed is improved, but the base region becomes prone to punch-through and leakage currents increase
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping concentration distribution within the base region. Specifically, a high-concentration doped island is formed at the bottom of the base region while the upper portion maintains lower doping concentration. This local variation allows the base region to simultaneously achieve shallow depth for fast switching while the high-concentration island prevents punch-through and reduces leakage currents, thus resolving the contradiction between switching speed and base region stability.
2Productivity
If the base region doping concentration is reduced to improve current gain, then the common emitter current gain is improved, but the base region becomes more susceptible to punch-through
Solution Approach 1:
The patent implements local quality by introducing a high-concentration doped island at the bottom of the base region. This allows the majority of the base region to maintain low doping concentration for high current gain, while the localized high-concentration island provides the necessary electrical stability to prevent punch-through. The selective placement of high doping concentration only where needed resolves the contradiction between improving current gain and maintaining base region stability.
Solution Approach 2:
The patent applies parameter changes by varying the doping concentration parameter within the base region. The doping concentration is changed from uniform to non-uniform, with a specific high-concentration zone introduced at the bottom of the base region. This parameter modification enables the base region to achieve both low average doping concentration (for high current gain) and localized high doping concentration (for preventing punch-through), thus resolving the contradiction.
3Ease of manufacture
If the base region is made uniform in concentration to simplify manufacturing, then the manufacturing process is simplified, but leakage currents increase and current gain is reduced
Solution Approach 1:
The patent applies local quality by introducing a high-concentration doped island at the bottom of the base region while keeping the rest of the base region uniform. This localized modification can be achieved through targeted ion implantation or diffusion processes, which are standard semiconductor manufacturing techniques. The result is a structure that maintains manufacturing simplicity while significantly improving current gain and reducing leakage currents compared to a completely uniform base region.
4Reliability
If the base region depth is increased to prevent punch-through, then base region stability is improved, but switching speed decreases due to longer carrier transit time
Solution Approach 1:
The patent resolves this contradiction by applying local quality through a high-concentration doped island positioned at the bottom of the base region. This localized high-concentration zone provides the electrical stability needed to prevent punch-through without requiring an increase in the overall base region depth. The carrier transit time remains short because the base region remains shallow, while the high-concentration island provides the necessary barrier against punch-through, thus simultaneously improving stability and maintaining fast switching speed.
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 effectively reduces the risk of base region punch-through, minimizes current leakage, and enhances current gain by creating a high P-type concentration in the non-working base region, thereby improving the device's performance and efficiency.
Implementation Method 1
forming a concentration gradient that reduces recombination and prevents punch-through
Data Source
AI summary
A manufacturing method for a super-β bipolar junction transistor includes providing a substrate, and forming a first conductive type isolation buried layer and a first conductive type doped layer based on the substrate. The isolation buried layer is located at a bottom of the doped layer. The method also includes forming a second conductive type base region in the doped layer and forming a second conductive type doped island on a peripheral side of the base region. A doping concentration of the doped island is greater than that of the base region. Additionally, the method includes forming a first conductive type collector region in the doped layer, and the collector region is spaced from the base region. Further, the method includes forming a first conductive type emitter region in the base region.