Solar Cell Pre-Amorphization Ion Implantation
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Solution Overview
Problem
Conventional solar cell manufacturing processes face challenges in simultaneously heat-treating different dopants with varying suitable temperatures, leading to excessive diffusion and increased costs due to higher temperatures required for heat-treatment.
Innovation Solution
A method involving ion-implantation of pre-amorphization elements and conductivity type dopants into a semiconductor substrate, allowing for low-temperature activation through solid phase epitaxy, enabling simultaneous heat-treatment of dopants with different suitable temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat-treatment is performed at higher temperature to activate dopants requiring high temperature, then the dopants are activated, but other dopants are excessively diffused and cost increases
Solution Approach 1:
The patent applies pre-amorphization by implanting heavy ions (such as xenon or germanium) into the semiconductor substrate before doping. This creates an amorphous layer that serves as a template for subsequent dopant implantation. The pre-amorphization step prepares the lattice structure in advance, enabling low-temperature activation of dopants while preventing excessive diffusion, thus resolving the contradiction between dopant activation and diffusion control.
Solution Approach 2:
The patent changes the physical state of the semiconductor lattice from crystalline to amorphous through pre-amorphization ion implantation. This parameter change enables dopant activation at lower temperatures (below 900°C) while maintaining precise dopant profile control. The amorphous structure allows for uniform dopant distribution and activation without the excessive diffusion that occurs in conventional crystalline silicon at high temperatures.
2Reliability
If heat-treatment temperature is increased to activate all dopants, then all dopants can be activated, but manufacturing cost increases and process complexity increases
Solution Approach 1:
The pre-amorphization step creates a uniform amorphous structure that enables subsequent low-temperature dopant activation. This preliminary preparation allows all dopants to be activated at a single low temperature (below 900°C) without requiring multiple heat-treatment steps at different temperatures, thereby simplifying the manufacturing process while maintaining reliable dopant activation.
Solution Approach 2:
The amorphous layer created by pre-amorphization serves multiple functions: it acts as a template for dopant implantation, enables low-temperature dopant activation, and prevents excessive dopant diffusion. This multi-functional approach allows a single low-temperature heat-treatment step to activate all dopant types simultaneously, simplifying the manufacturing process while maintaining effectiveness.
3Ease of manufacture
If conventional ion-implantation is used without pre-amorphization, then the process is simpler, but dopants cannot be effectively activated at low temperature
Solution Approach 1:
The pre-amorphization step creates an amorphous layer that serves as a template for subsequent dopant implantation and activation. This preliminary preparation enables effective dopant activation at low temperatures (below 900°C), overcoming the limitation of conventional ion-implantation that requires high temperatures for dopant activation while maintaining process simplicity through a standardized sequence of steps.
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 approach enhances the efficiency and reduces the cost of solar cell production by minimizing dopant diffusion and controlling the doping profile, thereby improving the solar cell's performance and manufacturing ease.
Implementation Method 1
ion-implanting a pre-amorphization element into a front surface of the semiconductor substrate to form an amorphous layer
Implementation Method 2
forming an emitter layer by ion-implanting a second conductivity type dopant into the front surface of the semiconductor substrate
Implementation Method 3
allowing for low-temperature activation through solid phase epitaxy
Data Source
AI summary
A method for manufacturing a solar cell according to an embodiment of the present invention includes preparing a semiconductor substrate having a first conductivity type dopant; ion-implanting a pre-amorphization elements into a front surface of the semiconductor substrate to form an amorphous layer; and forming an emitter layer by ion-implanting second conductivity type dopant into the front surface of the semiconductor substrate. The method then further includes heat-treating the layers to activate the second conductivity type dopant. The method further includes forming a back surface field layer at a back surface of the semiconductor substrate by ion-implanting a first conductivity type dopant.