Fin Cut Process for Vertical Transistor Source/Drain Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in forming stacked transistor devices is the separation of source/drain regions between the lower and upper transistors, which existing methods fail to address effectively, leading to non-uniformities in the final device structure.
Innovation Solution
A method involving the selective formation of a sacrificial spacer to cover upper channel layer end surfaces, allowing for the formation of lower source/drain regions while preventing growth on the upper layer, followed by the removal of the spacer to form upper source/drain regions, integrated within the fin cut process to avoid additional deposition and etch steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional fill material deposition and etch back steps are introduced to form the sacrificial spacer, then the sacrificial spacer can be formed selectively, but non-uniformities are introduced in the final device structure
Solution Approach 1:
The patent merges the sacrificial spacer formation process with the fin cut process by using the same etch steps for both operations. The fin cut etch simultaneously creates the fin recess and defines the sacrificial spacer location, eliminating the need for separate fill material deposition and etch back steps. This integration maintains manufacturing precision while reducing process complexity.
Solution Approach 2:
The fin cut etch process serves multiple functions: it creates the fin recess, defines the sacrificial spacer position, and prepares the structure for subsequent source/drain formation. This multi-functional approach eliminates redundant steps and ensures uniformity by using a single etch process for multiple purposes.
2Reliability
If a sacrificial spacer is formed to separate source/drain regions of lower and upper transistors, then selective formation is achieved, but the process becomes more complex
Solution Approach 1:
The sacrificial spacer formation is merged with the fin cut process, using the same etch steps to create both the fin recess and the sacrificial spacer structure. This integration achieves reliable source/drain region separation without adding complex separate formation steps.
Solution Approach 2:
The sacrificial spacer is formed preliminarily during the fin cut process, before source/drain region formation. This preliminary action ensures proper separation is established early in the process, enabling subsequent source/drain formation to proceed with reliable spatial definition.
3Ease of manufacture
If the fin cut process is partitioned into preliminary and final stages with sacrificial spacer formation in between, then selective sacrificial spacer formation is enabled, but additional process steps are required
Solution Approach 1:
The patent merges the preliminary fin cut, sacrificial spacer formation, and final fin cut into an integrated process sequence. The same etch steps perform multiple functions across what would traditionally be separate stages, enabling selective sacrificial spacer formation without requiring additional independent process stages.
Solution Approach 2:
The etch process is designed to perform multiple functions: creating the fin recess, forming the sacrificial spacer, and preparing for source/drain formation. This multi-functional approach enables selective sacrificial spacer formation while maintaining productivity by avoiding redundant process stages.
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
According to an aspect there is provided a method comprising: forming a fin cut mask above a semiconductor fin structure extending horizontally along a substrate, the fin structure comprising lower and upper channel layers separated by an intermediate layer, wherein the fin cut mask covers the fin structure in a channel region and exposes the fin structure in fin cut regions on opposite sides of the channel region, forming preliminary fin cuts in the fin structure by partially etching through the fin structure in the fin cut regions, wherein the partial etching extends through the upper layer in the fin cut regions to define an upper channel layer portion in the channel region, forming a sacrificial spacer covering end surfaces of the upper channel layer portion which are exposed in the fin cut regions on opposite sides of the channel region, forming final fin cuts in the fin structure by further etching through the fin structure in the fin cut regions, wherein the further etching extends into the lower layer in the fin cut regions to define a lower channel layer portion in the channel region, forming epitaxial lower source/drain regions on end surfaces of the lower channel layer portion which are exposed in the fin cut regions on opposite sides of the channel region, and removing the sacrificial spacer, thereby exposing the end surfaces of the upper channel layer portion, and forming epitaxial upper source/drain regions on the end surfaces of the upper channel layer portion.