Doped Semiconductor Layer Structure for Low-Resistance Ge Contacts
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Solution Overview
Problem
Conventional methods for forming doped semiconductor layers face challenges in achieving low contact resistance, particularly for p-type MOS devices, due to low boron solubility in germanium and the difficulty in maintaining layer quality during high-temperature annealing processes.
Innovation Solution
The method involves forming a first doped semiconductor layer with a first dopant and a second dopant, followed by the formation of a second doped semiconductor layer with the first dopant, all done at relatively low temperatures without the need for annealing. This approach allows for selective deposition of doped semiconductor material with specific dopant combinations, such as boron and gallium, to enhance carrier mobility and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high boron concentration is used in silicon germanium film to reduce contact resistance, then contact resistance decreases, but manufacturing precision deteriorates due to low boron solubility in germanium
Solution Approach 1:
The patent introduces carbon as an intermediary element that mediates between boron and germanium. Carbon forms a carbon-boron complex that enhances boron solubility in germanium matrix, enabling high boron concentration (1×10^20 to 1×10^21 atoms/cm³) without precipitation or clustering. This intermediary mechanism resolves the solubility limitation while maintaining manufacturing precision.
Solution Approach 2:
The patent creates a composite doped semiconductor layer containing four elements: silicon, germanium, boron, and carbon. This composite material structure leverages the beneficial properties of each element: silicon provides the base semiconductor properties, germanium enhances carrier mobility, boron provides p-type doping, and carbon enhances boron solubility. The composite approach enables achieving high boron concentration with controlled precision.
2Reliability
If high-temperature annealing is used to improve dopant solubility and reduce contact resistance, then contact resistance decreases, but structural integrity deteriorates due to dopant clustering at surface
Solution Approach 1:
The patent fundamentally changes the temperature parameter from conventional high-temperature annealing (>800°C) to low-temperature processing (400°C to 650°C). This parameter change is made possible by the carbon-mediated boron incorporation mechanism, which maintains dopant solubility at lower temperatures. The low temperature prevents dopant diffusion and clustering while still achieving the desired dopant concentration and low contact resistance, thus preserving compositional stability.
Solution Approach 2:
The patent replaces the thermal activation mechanism (high-temperature annealing) with a chemical mechanism (carbon-mediated dopant incorporation during deposition). Instead of relying on thermal energy to overcome solubility limits and activate dopants, the process uses chemical interactions between carbon and boron during the deposition phase to achieve dopant incorporation. This substitution eliminates the need for high-temperature annealing and its associated harmful effects.
3Reliability
If conventional doping methods are used to achieve high dopant concentration, then contact resistance decreases, but device complexity increases due to multiple processing steps
Solution Approach 1:
The patent merges the dopant incorporation step with the semiconductor layer deposition step into a single atomic layer deposition (ALD) process. By introducing carbon-containing precursors and boron-containing precursors simultaneously during ALD, the process achieves both high-quality film deposition and high-concentration doping in one step. This merging eliminates separate doping steps and reduces overall process complexity while maintaining low contact resistance.
Solution Approach 2:
The atomic layer deposition process is made multi-functional by enabling it to perform both film deposition and dopant incorporation simultaneously. The ALD process universally handles the incorporation of silicon, germanium, carbon, and boron in a single cyclic process, achieving multiple objectives (film formation, composition control, dopant incorporation) through a unified mechanism. This universality reduces the number of processing steps and simplifies the overall manufacturing process.
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 method effectively forms doped semiconductor layers with low contact resistance and maintains the structural integrity of the deposited layers, even at low temperatures, thereby addressing the limitations of conventional techniques.
Implementation Method 1
One approach to improve semiconductor device performance is to enhance the carrier mobility, and consequently the transistor drive current, utilizing strain induced effects
Implementation Method 2
The method involves forming a first doped semiconductor layer with a first dopant and a second dopant, followed by the formation of a second doped semiconductor layer with the first dopant, all done at relatively low temperatures without the need for annealing
Data Source
AI summary
Methods and systems for depositing material, such as doped semiconductor material, are disclosed. An exemplary method includes providing a substrate, forming a first doped semiconductor layer overlying the substrate, and forming a second doped semiconductor layer overlying the first doped semiconductor layer, wherein the first doped semiconductor layer comprises a first dopant and a second dopant, and wherein the second doped semiconductor layer comprises the first dopant. Structures and devices formed using the methods and systems for performing the methods are also disclosed.