HF-HCl Etching Solution for Polymer Removal in High-K Gate Stack
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Solution Overview
Problem
In the gate-first process for manufacturing nanometer-scale semiconductor devices, a polymer layer remains after etching a high-K gate dielectric/metal gate stack structure, which must be removed to prevent performance issues, but existing methods lack effective solutions for complete removal without damaging the silicon substrate.
Innovation Solution
A method involving a dilute HF solution with added HCl is used to etch the polymer layer, maintaining the vertical profile of the gate stack and avoiding substrate damage, with specific etching steps and gas compositions for different materials in the stack structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to etch the gate stack structure, then the gate stack profile is obtained, but polymer layer remains on both sides of the gate stack and on the silicon substrate surface
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by adding HCl to HF solution, adjusting the composition ratio to achieve selective removal of polymer while preserving the gate stack profile. This parameter modification enables the solution to differentiate between polymer material and the gate stack materials.
Solution Approach 2:
The HCl acts as an intermediary substance that enhances the HF solution's ability to remove polymer. The combination of HF and HCl creates a synergistic effect where HCl facilitates the breakdown of polymer while HF provides the primary etching capability, allowing selective polymer removal without damaging the gate stack.
2Object-generated harmful factors
If strong etching solution is used to remove polymer, then polymer removal is effective, but the silicon substrate and field SiO2 are damaged
Solution Approach 1:
The etching solution is designed with local quality characteristics by creating a selective chemical environment where HCl and HF concentrations are optimized to target polymer specifically. The solution exhibits different etching rates for different materials: high etching rate for polymer, low etching rate for field SiO2, and negligible etching rate for silicon substrate, achieving selective removal without damage.
Solution Approach 2:
The patent uses a controlled amount of HF (0.2-1% by volume) combined with HCl (5-15% by volume) to achieve sufficient polymer removal without excessive etching that would damage the substrate. The partial action principle is applied by using just enough etching capability to remove polymer while stopping before substrate damage occurs.
3Object-generated harmful factors
If HF solution is used to remove polymer, then polymer etching is facilitated, but field SiO2 corrosion increases
Solution Approach 1:
HCl serves as an intermediary that modifies the HF solution's behavior. The HCl facilitates polymer etching through chemical reactions that break down polymer bonds, while simultaneously forming a protective layer or altering the solution chemistry to reduce HF's corrosive effect on field SiO2. This intermediary action enables selective etching.
Solution Approach 2:
The etching solution is a composite chemical system combining HF and HCl in specific ratios. This composite solution exhibits properties that neither component alone possesses: enhanced polymer etching capability from HCl combined with controlled SiO2 corrosion from the HF-HCl interaction, creating a synergistic etching system with selective removal characteristics.
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
The method effectively removes polymer residues from both sides of the gate stack and the silicon substrate surface, ensuring device performance and compatibility with CMOS processes while being cost-efficient.
Implementation Method 1
immersing the resultant structure of step 3) in an etching solution of HF/HCl/water to remove the polymer
Implementation Method 2
HCl is added in a dilute HF solution to suppress corrosion to the field SiO2
Data Source
AI summary
The present invention provides a method for removing polymer after etching a gate stack structure of high-K gate dielectric/metal gate. The method mainly comprises the following steps: 1): forming a gate stack structure of interface Si2/high-K gate dielectric/metal gate/poly-silicon/hard mask in sequence on a silicon substrate with device isolations formed thereon; 2): forming a resist pattern by the lithography; 3): etching the gate stack structure; and 4): immersing the resultant structure of the step 3) in an etching solution to remove the polymer, wherein the etching solution consists of HF, HCl and water, the ratio of HF by volume is 0.2˜1% and the ratio of HCl by volume is 5˜15%.