Silicon Oxide Recess Etching with Stop-Layer Protective Deposition
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Solution Overview
Problem
Existing etching methods for silicon oxide films struggle with achieving high etching selectivity and minimizing shape distortion when forming recesses that reach etching stop layers, particularly due to the lack of effective control over the etching process and the deposition of substances from the plasma.
Innovation Solution
The method involves disposing a substrate with tungsten or molybdenum etching stop layers within a silicon oxide film, using a processing gas containing tungsten or molybdenum hexafluoride, carbon, and oxygen to generate plasma, which forms recesses that reach the etching stop layers, thereby depositing a substance that reduces the etching rate of these layers and improves selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to form recesses in silicon oxide film, then the etching process can be completed, but the etching selectivity between silicon oxide film and etching stop layers is insufficient and shape distortion occurs
Solution Approach 1:
The etching process is divided into multiple distinct steps with different gas compositions: a first etching step using CF4/O2 plasma for initial recess formation, and a second etching step using NF3 plasma for precise depth control and stop layer protection. This segmentation allows each step to be optimized for its specific function, achieving high selectivity without excessive process complexity
Solution Approach 2:
The method employs periodic alternation between different etching gases and plasma conditions. The CF4/O2 plasma is used periodically for high-rate etching, then switched to NF3 plasma for controlled termination at the stop layer. This periodic action enables the system to achieve both high etching rates and precise selectivity control
2Productivity
If high etching rate is achieved for silicon oxide film, then productivity increases, but shape distortion of the recesses increases
Solution Approach 1:
The method changes plasma chemistry parameters by switching between CF4/O2 and NF3 gases. CF4/O2 provides high etching rate with good anisotropy, while NF3 provides lower etching rate with excellent selectivity and shape control. By adjusting gas flow rates, pressure, and power parameters in each step, the process achieves both high productivity and minimal shape distortion
Solution Approach 2:
The two etching steps are performed in continuous sequence without breaking vacuum or removing the substrate. The CF4/O2 etching continues until the stop layer is reached, then NF3 plasma immediately takes over to complete the recess formation with precise depth control. This continuous action maintains productivity while ensuring shape accuracy throughout the process
3Length of moving object
If the etching process is extended to reach deeper etching stop layers, then the recess depth increases, but the mask and etching stop layers suffer from excessive etching
Solution Approach 1:
The etching stop layers (tungsten or molybdenum) serve as intermediary protective barriers between the mask and the substrate. These stop layers have high etching resistance to CF4/O2 plasma, allowing the recess to be etched deeply through the silicon oxide film while the stop layer protects underlying structures. The NF3 plasma further protects the stop layer during the final depth adjustment phase
Solution Approach 2:
The etching stop layers are formed in advance before the recess etching process. This preliminary action creates protective barriers that prevent excessive etching of underlying structures during the deep recess formation. The stop layers are strategically positioned to provide protection exactly where needed during the high-rate CF4/O2 etching step
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 enhances the etching selectivity of the silicon oxide film with respect to the etching stop layers, reduces shape distortion, and increases the etching rate of the silicon oxide film while minimizing the etching of the mask and etching stop layers.
Implementation Method 1
generating plasma from the processing gas to etch the silicon oxide film
Implementation Method 2
a substance generated from the gas containing at least one of tungsten and molybdenum in the plasma is deposited on the bottoms of the recesses
Data Source
AI summary
An etching method includes (a) disposing a substrate having a silicon oxide film on a substrate support in a chamber. The substrate includes a plurality of etching stop layers arranged inside the silicon oxide film. The plurality of etching stop layers are arranged at different positions in a thickness direction of the silicon oxide film. Each of the plurality of etching stop layers is formed of at least one of tungsten and molybdenum. The etching method (b) supplying a processing gas into the chamber, the processing gas including a gas containing at least one of tungsten and molybdenum, a gas containing carbon and fluoride, and an oxygen-containing gas; and (c) generating plasma from the processing gas to etch the silicon oxide film, thereby forming a plurality of recesses that reach the plurality of etching stop layers, respectively, in the silicon oxide film.