Plasma Etching High Aspect Ratio Openings
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Solution Overview
Problem
Conventional reactive ion etch technologies face decreased etch rates and undesirable bowed sidewalls as aspect ratios of openings increase in semiconductor device fabrication, hindering the formation of high aspect ratio structures necessary for advanced memory devices like 3D NAND Flash memory.
Innovation Solution
The method involves generating a plasma with a hydrogen-based gas and a fluorine-based gas, cooling the electrostatic chuck to low temperatures, and applying a non-sinusoidal low-frequency RF waveform to increase etch rates and reduce bowing, enabling the formation of high aspect ratio openings in semiconductor device structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional reactive ion etch technologies are used to form openings with high aspect ratios, then the depth of openings can be increased, but the etch rate decreases significantly
Solution Approach 1:
The patent applies parameter changes by modifying the RF waveform from sinusoidal to non-sinusoidal (e.g., square or triangular waveforms) and adjusting process parameters such as pressure, gas composition, and power levels. These parameter changes optimize the plasma chemistry and ion bombardment characteristics to achieve high etch rates while maintaining the ability to form deep openings with high aspect ratios
Solution Approach 2:
The patent utilizes dynamic control of the RF waveform parameters during the etching process. By dynamically adjusting the waveform shape, frequency, and power levels, the process can adapt to maintain optimal etch rates throughout the formation of deep openings, preventing the etch rate from decreasing as depth increases
2Length of stationary object
If conventional reactive ion etch technologies are used to form openings with high aspect ratios, then the depth of openings can be increased, but bowed sidewalls are formed
Solution Approach 1:
The patent modifies process parameters including RF waveform shape (non-sinusoidal), pressure, and gas composition to control the plasma chemistry and ion angular distribution. These parameter changes result in more vertical sidewalls by reducing the lateral etching that causes bowing, while still achieving the required opening depths
Solution Approach 2:
The patent replaces conventional sinusoidal RF control with non-sinusoidal RF waveform control to fundamentally change the plasma dynamics and ion bombardment patterns. This substitution transforms the etching mechanism to produce straighter sidewalls without requiring mechanical modifications to the etch chamber or mask structures
3Quantity of substance
If the aspect ratio of openings is increased to increase memory density, then more memory cells can be packed, but additional process steps are required
Solution Approach 1:
By changing the RF waveform parameters and process conditions, the patent achieves a single etch process that can form high aspect ratio openings in one step, eliminating the need for multiple sequential etching steps that would otherwise be required to achieve the same memory cell density
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 significantly enhances etch rates, increases the depth of openings, and reduces bowing, allowing for the formation of high aspect ratio structures with improved uniformity and productivity in semiconductor device fabrication.
Implementation Method 1
generating a plasma of a gas comprising a hydrogen-based gas and a fluorine-based gas
Implementation Method 2
forming an opening in the semiconductor device structure with the plasma
Implementation Method 3
cooling an electrostatic chuck on which the semiconductor device structure is positioned to a temperature of about −30° C. or less
Data Source
AI summary
Methods of processing a semiconductor device structure comprise cooling an electrostatic chuck (ESC) for the semiconductor device structure, which comprises tiers of alternating materials including at least one dielectric material, to a temperature of −30° C. or less, forming an opening in the semiconductor device structure with a plasma of a gas comprising a hydrogen-based gas and a fluorine-based gas in which the hydrogen-based gas comprises between about 10 vol % and 90 vol %. Other methods of processing a semiconductor device structure comprise cooling an ESC for the semiconductor device structure to a temperature of −30° C. or less, applying a low frequency radio frequency (RF) having a non-sinusoidal waveform to the ESC, and forming an opening in the semiconductor device structure with a generated plasma. A processing system includes an ESC, a coolant system, and a low frequency RF power source generating a non-sinusoidal waveform comprising a combination of multiple sinusoidal waveforms.