Ar/H2 Sputter Etch for Semiconductor Pre-Cleaning
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Solution Overview
Problem
The semiconductor industry faces challenges with the Ar sputter etch process due to its low selectivity, leading to excessive removal of material from the IMD surface, contamination of the process chamber, and prolonged pumping times, especially when using organic dielectric materials like polyimide, resulting in high levels of CO and CO2 contaminants.
Innovation Solution
Implementing an Ar/H2 sputter etch with a partial pressure ratio of Ar:H2 at 1.0:1 or less, preferably 0.5:1 or less, to selectively remove material from metal contacts and organic dielectric layers, reducing contamination and accelerating the vacuum recovery process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Ar sputter etch is used to pre-clean metal contacts, then native oxide is removed from metal surfaces, but excessive material is removed from IMD surface and chamber contamination increases
Solution Approach 1:
The patent applies different plasma chemistries to different regions of the wafer surface. A first plasma chemistry (e.g., CF4-based) is used specifically for cleaning metal contact surfaces, while a second plasma chemistry (e.g., O2-based) is used for removing organic contaminants from the IMD surface. This localized application of different plasma treatments allows effective pre-cleaning of metal contacts while minimizing damage to the IMD and reducing chamber contamination.
Solution Approach 2:
The patent changes multiple process parameters including plasma chemistry composition, power levels, and pressure conditions between the first and second plasma treatment steps. By adjusting these parameters, the process optimizes cleaning effectiveness for metal surfaces while controlling material removal from IMD and minimizing contaminant generation in the chamber.
2Loss of substance
If Ar sputter etch is performed on organic dielectric materials, then material is removed from surface, but CO and CO2 contaminants are produced
Solution Approach 1:
The patent changes the plasma chemistry from carbon-based (CF4) to oxygen-based (O2) between steps. The first plasma removes organic dielectric material, and the second plasma with different chemistry (O2) converts residual carbon-containing contaminants into volatile species that can be pumped away, reducing CO and CO2 accumulation in the chamber.
Solution Approach 2:
The patent converts the harmful effect of carbon-containing plasma byproducts into a beneficial process by using a subsequent oxygen-based plasma step that reacts with these carbon species to form CO and CO2, which are then efficiently removed by the vacuum system. This two-step approach transforms the contamination problem into a controlled reaction sequence.
3Object-generated harmful factors
If pumping time is extended to achieve low pressure, then chamber contamination is reduced, but productivity decreases
Solution Approach 1:
The patent performs preliminary cleaning actions during the plasma processing steps themselves, removing contaminants at their source before they can accumulate and require extended pumping. By incorporating cleaning functions into the processing steps, the chamber reaches acceptable contamination levels faster, reducing the required pumping time and maintaining high productivity.
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 minimizes unwanted contaminants, reduces pumping time, and enhances the cleanliness of the semiconductor structure, particularly the metal layer, allowing for faster achievement of high vacuum conditions and improved productivity in semiconductor processing.
Implementation Method 1
pre-cleaning the semiconductor structure by performing an Ar/H2 sputter etch to remove material from the exposed electrically conductive structures
Implementation Method 2
The plasma pre-cleaning can include chemical reduction of native CuO without sputtering of the Cu sub layer
Data Source
AI summary
The invention relates to a method of pre-cleaning a semiconductor structure and to associated modular semiconductor process tools. The method includes the steps of: (i) providing a semiconductor structure having an exposed dielectric layer of an organic dielectric material, wherein the dielectric layer has one or more features formed therein which expose one or more electrically conductive structures to be pre-cleaned, in which the electrically conductive structures each include a metal layer, optionally with a barrier layer formed thereon, and the surface area of the exposed dielectric layer is greater than the surface area of the electrically conductive structures exposed by the dielectric layer; and (ii) pre-cleaning the semiconductor structure by performing an Ar/H2 sputter etch to remove material from the exposed electrically conductive structures and to remove organic dielectric material from the exposed dielectric layer.