High Aspect Ratio Contact Etching Using Helium Plasma
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Solution Overview
Problem
High aspect ratio openings in insulating layers during semiconductor fabrication often experience a 'twisting' phenomenon, leading to reduced efficiency and difficulty in filling with conductive material due to increased aspect ratios, which existing etching processes using heavy ions cannot effectively mitigate.
Innovation Solution
The use of a gaseous etchant with at least 50% helium (He) or a mixture of He and argon (Ar) to etch high aspect ratio contacts, transitioning from heavy ions to light ions once the aspect ratio reaches 15:1, reduces twisting and maintains constant etch rates by neutralizing charge imbalances and reducing energy disparities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heavy ion plasma etching is used to etch high aspect ratio contacts, then the etching process can proceed, but twisting phenomenon occurs reducing etching precision
Solution Approach 1:
The patent changes the physical parameters of the plasma etching process by transitioning from heavy ion plasma to light ion plasma at a specific aspect ratio threshold (15:1). This parameter change in ion mass and energy fundamentally alters the etching mechanism to eliminate twisting while maintaining vertical profile control in high aspect ratio contacts
Solution Approach 2:
The patent implements a dynamic etching process where the plasma type is adjusted based on the real-time aspect ratio of the contact being etched. The system transitions from heavy ion plasma for lower aspect ratios to light ion plasma for higher aspect ratios, adapting the etching conditions to the current state of the structure to prevent twisting
2Manufacturing precision
If the aspect ratio of contacts is increased to meet minimum feature dimensions, then device scaling is achieved, but twisting phenomenon increases reducing contact efficiency
Solution Approach 1:
The patent applies parameter changes by switching plasma conditions based on aspect ratio thresholds, enabling precise control of contact dimensions even at high aspect ratios. This dynamic adjustment prevents twisting that would otherwise compromise dimensional accuracy in scaled devices
3Productivity
If high aspect ratio contacts are etched with conventional plasma, then openings can be formed, but etch rate becomes inconsistent
Solution Approach 1:
The patent employs dynamic plasma condition adjustment where the ion type and energy are modified as the contact aspect ratio increases. This maintains consistent etch rates throughout the deep etching process by preventing the twisting that causes etch rate variability, ensuring both productivity and precision
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 reduces twisting and maintains consistent etch rates, enabling the formation of high aspect ratio contacts with aspect ratios of at least 20:1, improving the efficiency and accuracy of semiconductor device fabrication.
Implementation Method 1
maintains constant etch rates by neutralizing charge imbalances
Implementation Method 2
The use of a gaseous etchant with at least 50% helium (He) or a mixture of He and argon (Ar) to etch high aspect ratio contacts
Implementation Method 3
reduces twisting and maintains constant etch rates by neutralizing charge imbalances and reducing energy disparities
Data Source
AI summary
A contact formed in accordance with a process for etching a insulating layer to produce an opening having an aspect ratio of at least 15:1 by first exposing the insulating layer to a second plasma of a second gaseous etchant comprising Ar, Xe, and combinations thereof to form an opening having an aspect ratio of less than 15:1. Secondly, the insulating layer is exposed to a first plasma of a first gaseous etchant having at least fifty percent helium (He) to etch the opening having an aspect ratio of at least 15:1, thereby increasing the aspect ratio to greater than 15:1, where the first gaseous etchant has a lower molecular weight than the second gaseous etchant.