Straight Sidewall Substrate Contact via Selective Polymer Protection
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Solution Overview
Problem
The existing reactive ion etch (RIE) process for removing silicon dioxide liners in deep trench semiconductor devices widens the top portion of the trench, necessitating thicker liner deposition and increased fabrication costs, as it removes dielectric material from the sidewalls.
Innovation Solution
A two-step process involving a pre-etch deposition of a protective polymer to prevent dielectric material removal from the sidewalls, followed by a main etch process that selectively removes the liner at the bottom of the trench while maintaining the polymer on the top, thereby preserving the sidewall liner thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a reactive ion etch (RIE) process is used to remove the silicon dioxide liner at the bottom of the trench, then the liner at the bottom is effectively removed to make contact to the substrate, but the high ion energies also remove dielectric material from the liner at the top of the deep trench, which undesirably widens a top portion of the deep trench
Solution Approach 1:
A protective polymer layer is deposited onto the top surface of the substrate and the sidewalls of the deep trench before the RIE process. This preliminary protective action prevents the high ion energies from removing dielectric material from the liner at the top of the trench, thereby preventing unwanted widening of the trench top portion while still allowing effective removal of the liner at the bottom.
Solution Approach 2:
The protective polymer provides selective protection: it covers the top surface and sidewalls where protection is needed, but allows the RIE process to effectively remove the liner at the bottom where contact is desired. This local differentiation of protection quality enables precise control over where material is removed and where it is preserved.
2Manufacturing precision
If the top portion of the deep trench is widened due to dielectric material removal, then the RIE process can effectively remove the liner, but a thicker layer of deposited silicon dioxide is required in the liner, which disadvantageously increases fabrication cost
Solution Approach 1:
The protective polymer is deposited in advance to prevent unwanted dielectric material removal from the top portion of the trench. By preventing the widening that would occur without protection, the original, thinner liner thickness is maintained, thereby avoiding the increased fabrication cost associated with depositing thicker silicon dioxide layers.
3Productivity
If high ion energies are used in the RIE process to remove the liner at the bottom, then effective liner removal is achieved, but dielectric material is also removed from the liner at the top of the deep trench
Solution Approach 1:
The protective polymer creates a local quality difference: areas covered by the polymer (top surface and sidewalls) are protected from dielectric material loss, while areas not covered (bottom of the trench) undergo effective liner removal. This spatial differentiation allows high ion energies to be used efficiently at the bottom while preventing material loss at the top.
Solution Approach 2:
The protective polymer is applied beforehand to prevent dielectric material loss from the top portion. This preliminary protective measure enables the use of high ion energies in the RIE process without the harmful side effect of removing dielectric material from the top, thereby maintaining productivity while reducing unwanted material loss.
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 the removal of the dielectric liner at the bottom of the deep trench without widening the top portion, reducing fabrication costs and maintaining the desired sidewall liner thickness, thus enhancing the efficiency and cost-effectiveness of the semiconductor device fabrication process.
Implementation Method 1
A pre-etch deposition step of the two-step process forms a protective polymer on an existing top surface of the semiconductor device, and on the dielectric liner proximate to a top surface of the substrate
Implementation Method 2
A reactive ion etch (RIE) process used to remove the silicon dioxide liner at the bottom of the trench to make contact to the substrate
Data Source
AI summary
A semiconductor device with a deep trench has a dielectric liner formed on sidewalls and a bottom of the deep trench. A pre-etch deposition step of a two-step process forms a protective polymer on an existing top surface of the semiconductor device, and on the dielectric liner proximate to a top surface of the substrate. The pre-etch deposition step does not remove a significant amount of the dielectric liner from the bottom of the deep trench. A main etch step of the two-step process removes the dielectric liner at the bottom of the deep trench while maintaining the protective polymer at the top of the deep trench. The protective polymer is subsequently removed.