Semiconductor Fin Formation Using Oxide Mask Etching
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Solution Overview
Problem
Conventional methods for forming semiconductor fins in integrated circuits face challenges such as pitch walking, leading to uneven spacing and difficulty in controlling critical dimensions, which affects transistor performance as integrated circuits scale down.
Innovation Solution
A method involving a stack of layers including a first oxide, a first nitride, a second oxide, and a first hardmask, where the hardmask is patterned and oxidized to form oxide fins, which are used as masks to etch underlying layers, allowing for precise formation of fins with reduced substrate gouging and increased critical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithographic or anisotropic etching processes are used to form fins, then the fin structures can be formed from the substrate, but pitch walking occurs resulting in unequal spacing and poor control of critical dimensions
Solution Approach 1:
The patent applies preliminary action by first forming a sacrificial mandrel structure and depositing spacer materials before final fin formation. The mandrel is patterned with precise dimensions, and spacers are deposited conformally to define fin spacing. This preliminary structuring establishes uniform pitch before the actual fin etching, preventing pitch walking and ensuring consistent critical dimensions across all fins.
2Productivity
If transistor size is decreased to increase transistor density, then more transistors can be packed into the integrated circuit, but controlling critical dimensions and maintaining transistor performance becomes difficult
Solution Approach 1:
The patent utilizes parameter changes by controlling the thickness of deposited spacer materials and the dimensions of the sacrificial mandrel to precisely define fin critical dimensions. By adjusting deposition parameters and mandrel geometry, the fin width and spacing can be accurately controlled at scaled dimensions, enabling high transistor density while maintaining precise critical dimension control.
3Productivity
If fins are formed with smaller critical dimensions to increase density, then transistor size decreases, but process margins are reduced and variability increases
Solution Approach 1:
The patent introduces a sacrificial mandrel and spacer materials as intermediary structures that mediate between the patterning process and final fin formation. These intermediary elements provide well-defined geometric templates with controlled dimensions, creating process margins that buffer against variability in subsequent etching steps. The mandrel-spacer-mandrel structure acts as a self-aligned template that ensures consistent fin dimensions even at small scales.
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 method results in semiconductor fins with larger and more uniform critical dimensions, reduced substrate gouging, and improved process margins, addressing the limitations of conventional fin formation processes.
Implementation Method 1
oxidizing the first set of hardmask fins to convert the first set of hardmask fins into a set of oxide fins
Implementation Method 2
etching the second oxide and the first nitride to expose portions of the first oxide thereunder
Data Source
AI summary
The disclosure is directed to methods for forming a set of fins from a substrate. One embodiment of the disclosure includes: providing a stack over the substrate, the stack including a first oxide over the substrate, a first nitride over the pad oxide, a second oxide over the first nitride, and a first hardmask over the second oxide; patterning the first hard mask to form a first set of hardmask fins over the second oxide; oxidizing the first set of hardmask fins to convert the first set of hardmask fins into a set of oxide fins; using the set of oxide fins as a mask, etching the second oxide and the first nitride to expose portions of the first oxide thereunder such that remaining portions of the second oxide and the first nitride remain disposed beneath the set of oxide fins thereby defining a set of mask stacks; and using the set of mask stacks as a mask, etching the exposed portions of the first oxide and the substrate thereby forming the set of fins from the substrate.