FinFET Well Implantation Sequence for Dopant Retention
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Solution Overview
Problem
In the manufacturing of fin-type field effect transistor (FinFET) devices, existing methods face challenges such as dopant ion diffusion, high ion energy requirements, and fin damage during well implantation, particularly when forming N-well and P-well regions.
Innovation Solution
A method involving separate N-type and P-type dopant implantations, where N-type dopants are implanted into a first region to form an N-well, followed by forming fins and filling gap spaces with insulating material, and then P-type dopants are implanted into a second region below the fins to form a P-well, avoiding diffusion and fin damage by controlling implantation sequences and energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If N-well and P-well are formed before forming the fins, then the implantation energy can be reduced, but dopant ions diffuse into the oxide material filling the gap spaces, resulting in loss of implanted dopant ions
Solution Approach 1:
The patent divides the well formation process into two separate stages: N-well formation before fin formation, and P-well formation after fin formation and gap filling. This segmentation allows each implantation to be optimized independently - the N-well implantation can use lower energy since no fins exist yet, while the P-well implantation occurs after the oxide fill is in place to prevent dopant diffusion, thus resolving the contradiction between energy usage and dopant retention.
Solution Approach 2:
The N-well is formed preliminarily before the fins are created, allowing the dopant ions to be implanted into the substrate without the complicating factor of existing fin structures. This preliminary action enables lower implantation energy to be used effectively, while the subsequent formation of fins and gap filling with oxide occurs after the N-well is already established.
2Reliability
If N-well and P-well are formed after the planarization of the STI structure, then the fin structure is protected, but the hardmask over the STI structure requires high ion energy for dopant implantation
Solution Approach 1:
The patent segments the well formation timeline so that P-well formation is delayed until after fin formation and gap filling, but the hardmask is selectively removed from the P-well implantation region before implantation. This allows the fin structures to remain protected during N-well formation, while enabling lower energy P-well implantation after the hardmask is temporarily removed, thus resolving the energy requirement contradiction.
3Manufacturing precision
If N-well and P-well are formed after the formation of the fins, then the implantation can be performed with precise positioning, but the implanted dopant ions cause damage to the fins, especially the N-well implant with high ion energy
Solution Approach 1:
The patent inverts the conventional sequence by forming the N-well before the fins rather than after. This reversal allows the N-well implantation to occur when no fins are present, eliminating fin damage from high-energy N-well implantation. The subsequent fin formation and P-well implantation are then performed with precise positioning capability, thus resolving both the precision and damage concerns.
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 prevents dopant ion loss and fin damage, maintaining implantation precision and stability, thereby enhancing the manufacturing process for FinFET devices.
Implementation Method 1
performing an N-type dopant implantation into a first region of the substrate to form an N-well
Implementation Method 2
performing a P-type dopant implantation into the second region below the second set of fins to form a P-well adjacent the N-well
Implementation Method 3
filling gap spaces between the fins to form an isolation region
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A method for manufacturing a semiconductor device includes providing a substrate, performing an N-type dopant implantation into a first region of the substrate to form an N-well, removing a portion of the substrate to form a first set of fins on the N-well and a second set of fins on a second region of the substrate adjacent the N-well, filling gap spaces between the fins to form an isolation region, and performing a P-type dopant implantation into the second region to form a P-well adjacent the N-well. The N-well and the P-well are formed separately at different times. The loss of the P-type dopant ions due to the diffusion of P-type dopant ions in the P-well into the isolation region can be eliminated, and the damage to the fins caused by N-type dopant ions can be avoided.