High-k Metal Gate Etching Selectivity via Additive Gas
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Solution Overview
Problem
The existing methods for etching high-k metal gate stacks face challenges such as low etch selectivity, damage to high-k materials, and defects like substrate recessing or undercutting, making it difficult to efficiently pattern high-k metal gate structures in semiconductor devices.
Innovation Solution
A method involving a two-step etching process using inductively coupled plasma with a main etch gas like BCl3 and an additive gas like argon, applied at different temperatures, to enhance etch selectivity and prevent substrate damage, along with subsequent wet cleaning to remove residues, is employed to etch high-k metal gate stacks effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etchants are used to etch high-k material, then the etching process can be performed, but etch selectivity is low causing substrate recessing or undercutting
Solution Approach 1:
The patent changes the chemical composition parameters of the etching plasma by introducing additive gases (CF4, C2F6, or C3F8) into the BCl3-based etching gas mixture. This parameter change modifies the etching chemistry to achieve higher selectivity between high-k material and substrate, preventing substrate recessing and undercutting while maintaining effective high-k material etching.
2Productivity
If plasma etching is used to etch high-k material, then etching can be performed, but the high-k material is likely to be damaged
Solution Approach 1:
The patent optimizes plasma etching parameters by controlling the ratio of additive gas to BCl3 within 5-50%, maintaining bias power between 10-30W, and setting source power between 100-300W. These parameter changes enable effective etching while minimizing plasma-induced damage to the high-k material by balancing etching aggressiveness with material protection.
Solution Approach 2:
The additive gases (CF4, C2F6, or C3F8) act as intermediaries in the etching process, modifying the plasma chemistry to reduce direct plasma damage to the high-k material while maintaining etching capability. These intermediary substances mediate between the plasma environment and the high-k material surface.
3Manufacturing precision
If a single etching process is used, then the process is simple, but it cannot achieve high etch selectivity for high-k material
Solution Approach 1:
The patent segments the etching process into two distinct stages: a first etching process using BCl3-based plasma for initial high-k material removal, and a second etching process using BCl3 combined with additive gases for selective etching with enhanced precision. This segmentation allows each process to be optimized for its specific function, achieving high overall selectivity.
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 achieves high etch selectivity and prevents defects like substrate recessing, enabling precise patterning of high-k metal gate structures without damage, thus improving the manufacturing process for semiconductor devices.
Implementation Method 1
performing a second etching process using inductively coupled plasma including a main etch gas and an additive gas, to etch the high-k material layer
Implementation Method 2
using inductively coupled plasma including a main etch gas like BCl3 and an additive gas like argon
Implementation Method 3
a method for etching a gate stack, capable of having a high etch selectivity with respect to the other materials during an etching process for a high-k material
Implementation Method 4
subsequent wet cleaning to remove residues
Data Source
AI summary
A method for etching a gate includes forming a high-k material layer over a substrate; forming an overlying layer over the high-k material layer; performing a first etching process for etching the overlying layer to form an overlying layer pattern; forming a spacer on a sidewall of the overlying layer pattern; and performing a second etching process using plasma including a etch gas and an additive gas, to etch the high-k material layer, wherein an amount of the additive gas is substantially the same as the main etch gas to increase an etch selectivity with respect to the substrate.