Laser Pulse Dopant Diffusion With Oxygen-Controlled Annealing
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Solution Overview
Problem
Current doping methods for semiconductor devices suffer from poor dopant uniformity, repeatability, defects in the dopant profile, undesired shape modification, and excessive dopant diffusion, often deforming the device structure due to high temperatures and multiple anneal cycles.
Innovation Solution
A method involving the use of rapid high temperature anneal pulses with controlled oxygen partial pressure and laser annealing to diffuse dopants into semiconductor substrates, reducing the number of anneal cycles and temperatures while maintaining dopant concentration and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional doping methods with high temperature anneal cycles are used, then dopant diffusion into the substrate occurs, but substrate deformation and structural damage occur
Solution Approach 1:
The patent applies periodic laser pulses instead of continuous heating to achieve dopant diffusion. The pulsed nature allows rapid heating and cooling cycles that prevent substrate deformation while maintaining effective dopant activation, directly resolving the contradiction between achieving uniform dopant profiles and preserving substrate integrity
Solution Approach 2:
The invention changes the temperature parameter by using extremely high peak temperatures (above melting point) for very short durations through laser pulsing, rather than sustained moderate temperatures. This parameter transformation enables dopant diffusion without the cumulative thermal damage that occurs in conventional annealing processes
2Manufacturing precision
If multiple anneal cycles are used to achieve desired dopant concentration, then dopant uniformity improves, but processing time and thermal damage increase
Solution Approach 1:
Multiple rapid laser pulses are applied in sequence, each contributing to dopant activation and diffusion. This periodic puling approach achieves the desired dopant uniformity in a single processing step rather than requiring multiple separate anneal cycles, thereby reducing total processing time while maintaining concentration uniformity
Solution Approach 2:
The laser pulses are applied in rapid succession with minimal cooling between pulses, maintaining the useful action of dopant activation continuously. This eliminates the idle time between separate anneal cycles while ensuring uniform dopant distribution through cumulative pulsed energy input
3Reliability
If high temperature annealing is used to activate dopants, then dopant diffusion occurs, but dopant profile shape distortion occurs
Solution Approach 1:
The periodic laser pulsing creates rapid thermal cycles that activate dopants through brief high-temperature exposure without allowing excessive diffusion that would distort the profile shape. The rapid cooling between pulses 'freezes' the dopant distribution, preserving the intended profile geometry while achieving sufficient activation
Solution Approach 2:
By changing from sustained moderate temperature to extreme peak temperature for ultra-short durations, the invention achieves dopant activation through a different thermal mechanism that does not allow the gradual profile distortion that occurs in conventional annealing, thereby maintaining profile shape integrity
4Reliability
If conventional RTP annealing is used for dopant diffusion, then dopant activation occurs, but dopant diffuses beyond desired region
Solution Approach 1:
The rapid pulsed heating and cooling prevents dopant atoms from diffusing beyond the desired region while still providing sufficient thermal energy for activation. The short duration of each pulse limits the diffusion distance, and the rapid cooling immediately after each pulse stops further diffusion, thereby controlling the dopant depth precisely
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
Achieves controlled dopant diffusion with reduced substrate deformation and strain, improving dopant uniformity and repeatability, and enabling precise dopant placement in complex structures like fin and gate all around transistors.
Implementation Method 1
exposing a portion of a substrate within the process volume to one or more laser pulses to heat the portion of the substrate to a temperature of greater than about 850° C.
Implementation Method 2
flowing an oxygen gas into the process volume such that an oxygen partial pressure of the oxygen gas is about 0.1% to about 10% within the process volume
Data Source
AI summary
A method and apparatus for diffusing a dopant within a semiconductor device is described. The method includes performing a dynamic surface anneal in which a substrate is placed inside of a process volume with a mixture of an inert gas and a small amount of oxygen gas. The surface of the substrate is then exposed to one or more rapid laser pulses. The rapid laser bursts diffuse dopant from a doped layer into the substrate. The doped layer is formed during a previous process operation. The temperature and number of laser pulses control the amount of diffusion of the dopant into the substrate. Other dynamic surface anneal operations may be optionally performed before or after the oxygenated dynamic surface anneal operation.