Deep Trench Etching in Microelectronic Substrates
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Solution Overview
Problem
Existing etching methods for deep trenches in microelectronic components either produce slow results with surface defects or quickly produce irregular sidewalls, making it difficult to achieve deep trenches with low form factors and smooth, passivated sidewalls necessary for efficient component operation.
Innovation Solution
A method involving pulsed plasma anisotropic ion etching with a series of elementary cycles, including deposition of a passivation layer and two etch sequences: a high-power sequence to access the substrate and a lower-power sequence to control the trench profile, using fluorinated plasma and specific power and frequency settings to prevent over-etching and ensure smooth sidewalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma-based ion etching is used to etch trenches quickly for mass production, then productivity is improved, but the sidewalls become irregular with overhangs and notches that block subsequent treatments
Solution Approach 1:
The etching process is divided into multiple sequential elementary cycles, each consisting of a deposition step followed by an etching step. This segmentation allows the process to build the trench incrementally while maintaining sidewall regularity through repeated thin layer deposition and removal, preventing the formation of large overhangs and notches that would block subsequent treatments.
Solution Approach 2:
The method employs periodic alternation between deposition and etching phases within each elementary cycle. This periodic action creates a self-regulating process where each deposited layer is subsequently etched away, preventing accumulation of material that would form blocking overhangs, while maintaining continuous forward progress of the trench etching.
2Manufacturing precision
If dry etching is used to restrict formation of surface defects, then sidewall quality is improved, but the etching process becomes very slow and incompatible with mass production
Solution Approach 1:
The method changes the parameters of plasma-based ion etching by controlling the deposition thickness to be very thin (on the order of nanometers) and using specific plasma conditions that allow for anisotropic etching with reduced sidewall damage. This enables faster etching rates while maintaining sidewall quality through precise parameter control rather than using slow dry etching methods.
Solution Approach 2:
The process creates a composite structure during each elementary cycle by depositing a passivation layer that is then partially removed by etching. This composite approach of combining deposition and etching in sequence allows the trench to be etched faster while the deposited material protects sidewalls from excessive damage, improving both speed and quality.
3Reliability
If the trench form factor is reduced to improve component isolation, then component performance is improved, but sidewall surface defects increase and become more problematic
Solution Approach 1:
A passivation layer is deposited on the trench sidewalls before the etching step in each elementary cycle. This preliminary action protects the sidewalls from damage during etching, reducing the formation of surface defects. The passivation layer is then partially removed by the etching process, allowing the trench to be formed while maintaining clean, defect-free sidewalls suitable for low form factor applications.
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
Enables rapid production of deep trenches with very low form factors and smooth, passivated sidewalls, facilitating subsequent treatments like passivation layer deposition and improving component performance by reducing noise and quantum efficiency loss.
Implementation Method 1
deposition of a passivation layer on the sidewalls and the bottom of the trench portion etched during previous cycles
Implementation Method 2
deposition of a passivation layer on the sidewalls and the bottom of the trench portion etched during previous cycles
Implementation Method 3
pulsed plasma anisotropic ion etching of the trench portion etched during previous cycles
Implementation Method 4
pulsed plasma anisotropic ion etching of the trench portion etched during previous cycles
Data Source
AI summary
A method for producing a deep trench in a substrate includes a series of elementary etch cycles each etching a portion of the trench. Each elementary cycle includes deposition of a passivation layer on the sidewalls and the bottom of the trench portion etched during previous cycles; followed by pulsed plasma anisotropic ion etching of the trench portion etched during previous cycles, the etching; being implemented in an atmosphere comprising a passivating species; and including a first etch sequence followed by a second etch sequence of less power than the power of the first etch sequence. The first etch sequence etches the passivation layer deposited in the bottom of the portion so as to access the substrate and etches the free substrate at the bottom of the portion while leaving a passivation layer on sidewalls of the portion.