ONO Stack Through-Hole Etching With Upper-Layer Protective Film
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Solution Overview
Problem
Existing methods struggle to selectively etch the lower portion of silicon nitride layers in an ONO stack while minimizing etching of the upper portion and silicon oxide layers, leading to uneven etching profiles and damage to the silicon oxide layer.
Innovation Solution
A method involving the use of a carbon-rich gas to form a protective film on the upper portion of the ONO stack, followed by selective etching with a fluorine-containing gas to etch the lower portion, using specific plasma conditions to control the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching gases (CF4, NF3) are used to selectively etch silicon nitride layers, then selectivity is improved, but etching rate of the lower portion becomes too slow
Solution Approach 1:
A protective film is formed on the upper portion of the ONO stack before the etching process. This preliminary action prevents the upper portion from being etched during the main etching process, enabling selective etching of the lower portion without compromising the upper portion, thus resolving the contradiction between selectivity and etching rate
Solution Approach 2:
The patent changes the etching gas parameters by using a carbon-rich gas (CH2F2 or CHF3) instead of conventional CF4 or NF3. This parameter change enables higher etching rates for the lower portion while the protective film maintains selectivity, resolving the contradiction between etching rate and selectivity
2Productivity
If the upper portion of the ONO stack is etched first, then etching progress is improved, but control of etching profile in thickness direction becomes difficult
Solution Approach 1:
The protective film is formed in advance on the upper portion, which serves as a mask during the etching process. This preliminary protective action ensures that only the lower portion is etched, providing precise control over the etching profile in the thickness direction while maintaining efficient etching progress
Solution Approach 2:
The protective film is selectively formed only on the upper portion of the ONO stack, creating different properties in different regions. The upper portion has protective coverage while the lower portion is exposed for etching, enabling precise local control of the etching profile
3Productivity
If hydrogen-containing etching gases are used, then etching activity is improved, but thick polymer film is generated reducing etching rate
Solution Approach 1:
The patent uses a carbon-rich etching gas (CH2F2 or CHF3) with specific hydrogen content rather than conventional CF4 or NF3. This parameter change provides sufficient etching activity while controlling polymer film formation, as the specific hydrogen-containing gas formulation balances reactivity with reduced polymer generation
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 allows for controlled etching profiles in the substrate thickness direction, reducing damage to the silicon oxide layers and minimizing the formation of regrowth oxides, while increasing the etching rate of the lower portion of the ONO stack.
Implementation Method 1
supplying a first processing gas to a through-hole to expose an oxide-nitride-oxide (ONO) stack to the first processing gas
Implementation Method 2
supplying a second processing gas to the through-hole to expose the ONO stack to the second processing gas to dry-etch the silicon nitride layers of the ONO stack
Data Source
AI summary
Disclosed is a substrate processing method which may easily adjust an etching profile in a thickness direction of a substrate. In the method, the substrate has an ONO stack formed thereon, wherein the ONO stack includes a stack structure in which silicon oxide layers and silicon nitride layers are alternately stacked on top of each other, wherein a through-hole extends through the ONO stack such that side surfaces of the silicon oxide layers and the silicon nitride layers are exposed. The method includes: (a) supplying a first processing gas to the through-hole to expose the ONO stack to the first processing gas; and (b) supplying a second processing gas to the through-hole to expose the ONO stack to the second processing gas to dry-etch the silicon nitride layers of the ONO stack, wherein the first processing gas includes CxFy, wherein a x/y is 0.5 or greater.