Reverse RIE Lag Etch Planarization for Sub-36 nm Pitches
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Solution Overview
Problem
Chemical Mechanical Polishing (CMP) is a harsh and expensive process that cannot be used for certain microfabrication steps, such as transistor fabrication, and reduces the yield of functional integrated circuits due to its abrasive nature and limitations in planarization, especially when dealing with structures like gate oxides.
Innovation Solution
A dry etch-based planarization process using plasma-based etching with a reverse RIE lag process is employed to normalize the coating height on substrates with varying feature densities and structure heights, allowing for the deposition of a first layer that is then etched to create a planar surface, followed by a second layer to achieve a highly planar surface without the need for CMP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Chemical Mechanical Polishing (CMP) is used for planarization, then a planar surface can be achieved, but the process becomes harsh, expensive, and reduces yield
Solution Approach 1:
The patent replaces the mechanical CMP process with a plasma-based etching process. Instead of using mechanical abrasion and chemical slurries to remove material, the invention uses controlled plasma etching to selectively remove fill material, achieving planarization through chemical and physical vapor phase reactions rather than mechanical contact.
Solution Approach 2:
The patent changes the fundamental process parameters from mechanical/chemical (CMP) to plasma-based etching parameters. This includes controlling plasma power, gas flow rates, pressure, and etch chemistry to achieve the desired planarization effect without the harmful mechanical abrasion of CMP.
2Manufacturing precision
If CMP is used for planarization, then surface flatness can be improved, but the process becomes expensive and complex
Solution Approach 1:
The patent replaces the complex multi-step CMP process (including spin-on glass application, slurry delivery, polishing pad mechanics, and chemical slurry management) with a simpler plasma etching process that uses standard semiconductor manufacturing equipment and well-controlled plasma chemistry.
Solution Approach 2:
The patent extracts and eliminates the unnecessary components of the CMP process, such as spin-on glass, polishing pads, and chemical slurries, retaining only the essential planarization function through a more direct plasma etching approach.
3Loss of substance
If conventional etching is used, then material can be removed, but etch lag causes non-uniform etching across different density areas
Solution Approach 1:
The patent inverts the conventional etching approach by using a reverse RIE lag process. Instead of accepting that dense areas etch slower than open areas (conventional RIE lag), the process parameters are adjusted so that dense areas etch faster, compensating for the initial non-planarity and achieving a planar final surface.
Solution Approach 2:
The patent changes the etch process parameters (power, pressure, gas composition, temperature) to reverse the typical etch lag behavior. By optimizing these parameters, the process achieves faster etching in dense areas compared to open areas, thereby planarizing the surface rather than exacerbating non-uniformity.
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 provides an accurate, economical, and non-damaging planarization technique suitable for advanced microfabrication processes, including sub-36 nm pitch features, by reversing the typical etch lag effect to ensure uniform etching across substrates with different density areas, resulting in a surface with z-height differences of less than three nanometers.
Implementation Method 1
A dry etch-based planarization process, such as with plasma-based etching
Implementation Method 2
modifying a substrate coating using a reverse RIE (reactive ion etch) lag process to normalize coating height
Data Source
AI summary
Techniques herein provide an etch-based planarization technique. An initial film is deposited on a substrate. Deposition of this initial film results in a non-planar film because of differences in area density of underlying structures (for example, open areas compared to closely spaced trenches). Etch processes are executed that use a reverse lag RIE process to planarize the initial film, and then another coat of the film material can be deposited, resulting in a planar surface. Such techniques can planarized substrates without using chemical mechanical polishing (CMP).