Backscatter Layer for Localized Semiconductor Annealing
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Solution Overview
Problem
Conventional rapid thermal processing methods for semiconductor wafers, such as lamp and laser annealing, often result in uneven heating due to emissivity differences, leading to undesired diffusion of dopant atoms and limited penetration depth of photons, which complicates the annealing process.
Innovation Solution
The use of a backscatter layer that reflects or scatters radiation to prevent unwanted heating in certain areas of the wafer while allowing targeted heating of specific regions, enabling localized and controlled annealing through the use of microwave or other radiation, allowing for micron or nanometer-scale heating and tailored thermal budgets for different layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lamp or laser annealing is used to achieve high temperature heating, then dopant activation and lattice repair are enabled, but uneven heating occurs due to emissivity differences and limited photon penetration depth
Solution Approach 1:
A backscatter layer is introduced as an intermediary component between the radiation source and the semiconductor wafer. This layer selectively backscatters radiation to create a more uniform radiation distribution pattern, mediating the interaction between the lamp/laser and the wafer to eliminate hot spots and uneven heating while maintaining the high temperature capability needed for dopant activation and lattice repair
Solution Approach 2:
The backscatter layer is designed with spatially varying properties to provide different levels of radiation backscattering in different regions of the wafer. This local customization of radiation distribution compensates for emissivity differences across the wafer surface, ensuring uniform heating throughout the entire processing area while maintaining the high temperature regime required for effective annealing
2Duration of action of moving object
If conventional RTP methods are used to minimize dopant diffusion, then heating time is reduced, but penetration depth of photons is limited and uneven heating persists
Solution Approach 1:
The backscatter layer serves as a mediating structure that redistributes the incident radiation before it reaches the wafer. By positioning this layer strategically, the system achieves improved thermal distribution control across the wafer surface during the rapid heating process, ensuring that the shortened heating duration still produces uniform thermal results throughout the entire wafer area
Solution Approach 2:
The introduction of the backscatter layer adds a new dimensional element to the heating system architecture. This additional layer creates a more complex radiation path with multiple interactions (incident radiation, backscattering, re-radiation), transforming the simple direct heating approach into a multi-stage process that achieves both rapid heating and uniform thermal distribution simultaneously
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 allows for more precise and even annealing, reducing unwanted diffusion and enabling higher thermal budgets for upper layers compared to lower layers, facilitating the formation of complex device structures that would be impossible with conventional methods.
Implementation Method 1
a backscatter layer that reflects or scatters radiation to prevent unwanted heating in certain areas of the wafer
Implementation Method 2
The use of a backscatter layer that reflects or scatters radiation to prevent unwanted heating in certain areas of the wafer while allowing targeted heating of specific regions, enabling localized and controlled annealing through the use of microwave or other radiation
Implementation Method 3
The active layer includes an annealed section and a non-annealed section. The annealed section corresponds to a pattern of the backscatter layer. The active layer includes a material absorptive of electromagnetic energy at a predetermined wavelength at which the backscatter layer backscatters the electromagnetic energy
Data Source
AI summary
A method of fabricating an electronic apparatus includes forming an active layer over a wafer, forming a backscatter layer over the wafer, and directing radiation toward the wafer to anneal the active layer. The backscatter layer is not transparent to the radiation, more reflective than absorptive of the radiation, and positioned such that the backscatter layer inhibits exposure of the wafer to the radiation apart from the active layer.