Poly Directional Etch by Oxidation for Semiconductor Trenches
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Solution Overview
Problem
Current semiconductor etching processes face challenges in achieving high selectivity and minimizing material deformation, especially when dealing with constrained trenches and delicate structures, as they often require protective layers and may damage substrates through electric arcs in plasma etching.
Innovation Solution
The method involves oxidizing a silicon surface in a semiconductor substrate within a processing chamber, forming an inert plasma, and using remote plasma effluents from a fluorine-containing precursor to modify and selectively etch the oxidized silicon, allowing for high selectivity and controlled removal without the need for protective layers, using a helium plasma with low bias power and maintaining pressures below 50 mTorr.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet HF etch is used to remove silicon oxide, then etching speed is improved, but the process cannot penetrate constrained trenches and may deform remaining material
Solution Approach 1:
The patent replaces wet chemical etching with a plasma-based process that uses ion bombardment and chemical reaction to remove silicon oxide. The plasma process substitutes the liquid chemical mechanism with a gas-phase plasma mechanism involving fluorine radicals and ion physical sputtering, enabling penetration into constrained trenches while maintaining control over material removal.
Solution Approach 2:
The patent employs parameter changes by controlling plasma power (below 100 W bias power), pressure (below 50 mTorr), and gas composition to achieve selective etching. By adjusting these parameters, the process achieves high etching rates for modified silicon oxide while minimizing damage to unmodified regions and delicate structures.
2Manufacturing precision
If local plasma is used to etch constrained trenches, then penetration ability is improved, but substrate damage occurs through electric arcs
Solution Approach 1:
The patent extracts the harmful electric arc component from the plasma process by using remote plasma generation. The plasma is generated in a separate region and then transported to the substrate, separating the ionization zone from the processing zone. This removes the source of electric arc damage while maintaining the beneficial etching effects.
Solution Approach 2:
The patent introduces an intermediary transport mechanism to deliver plasma effluents from the remote plasma source to the substrate. This intermediary system (plasma transport through controlled atmosphere) allows the beneficial reactive species to reach the substrate while preventing direct contact with high-energy ions that cause damage.
3Object-affected harmful factors
If protective layers are used in etching processes, then substrate protection is improved, but process complexity increases
Solution Approach 1:
The patent implements self-service protection by using the silicon oxide layer itself as the protective barrier. The selective etching process removes only modified silicon oxide while leaving unmodified silicon oxide and other materials intact. This self-limiting nature provides inherent protection without requiring additional protective layers.
Solution Approach 2:
The patent achieves selectivity through parameter changes in the plasma process. By controlling plasma power, pressure, and gas composition, the process selectively etches modified silicon oxide with high selectivity (>100:1) compared to unmodified materials, providing protection through chemical selectivity rather than physical barriers.
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 enables high selectivity of over 100:1 in etching modified versus unmodified silicon oxide, allowing for precise removal of silicon and nitride materials with minimal substrate damage, reducing the need for protective layers and enhancing the quality of semiconductor features.
Implementation Method 1
oxidizing an exposed silicon surface on a semiconductor substrate within a processing region of a semiconductor processing chamber
Implementation Method 2
forming an inert plasma within the processing region of the processing chamber. Effluents of the inert plasma may be utilized to modify the oxidized silicon
Implementation Method 3
contacting the modified silicon oxide with plasma effluents of a fluorine-containing precursor. The methods may also include etching the modified silicon oxide
Data Source
AI summary
Processing methods may be performed to form recesses in a semiconductor substrate. The methods may include oxidizing an exposed silicon surface on a semiconductor substrate within a processing region of a semiconductor processing chamber. The methods may include forming an inert plasma within the processing region of the processing chamber. Effluents of the inert plasma may be utilized to modify the oxidized silicon. A remote plasma may be formed from a fluorine-containing precursor to produce plasma effluents. The methods may include flowing the plasma effluents to the processing region of the semiconductor processing chamber. The methods may also include removing the modified oxidized silicon from the semiconductor substrate.