Plate Oxide Layer for Bulk Oxide Thickness in Semiconductor Devices
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Solution Overview
Problem
As semiconductor device dimensions shrink, it becomes challenging to grow a thick and robust localized oxidation of silicon (LOCOS) oxide between closely spaced silicon regions, as the oxide layer thins and is further diminished by subsequent processing steps, affecting ion implant blocking and isolation effectiveness.
Innovation Solution
A method involving the formation of a bulk oxide layer with a plate oxide layer over the substrate in active regions, followed by a self-aligned silicide process, which maintains the initial thickness of the bulk oxide layer without additional processing steps, thereby protecting it from subsequent etch steps and enhancing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LOCOS oxide growth is performed between closely spaced silicon regions, then oxide isolation is achieved, but the oxide layer thickness is reduced due to bird's head profile formation
Solution Approach 1:
A thick plate oxide layer is deposited over the entire surface before LOCOS processing. This preliminary action ensures that even when the LOCOS oxide thins due to bird's head profile formation near active regions, the underlying plate oxide maintains the required thickness for isolation and capacitance reduction.
Solution Approach 2:
The isolation structure combines two oxide layers: the LOCOS bulk oxide and the deposited plate oxide. This composite approach allows the plate oxide to compensate for the thinning of LOCOS oxide in critical areas, maintaining effective isolation thickness while enabling closer spacing of active regions.
2Productivity
If subsequent processing steps are performed after LOCOS oxide growth, then device fabrication continues, but the oxide thickness is diminished by etch steps
Solution Approach 1:
The plate oxide layer serves as a protective intermediary over the LOCOS bulk oxide. During subsequent processing steps such as spacer formation and other etch operations, the plate oxide is selectively removed in non-critical areas while protecting the bulk oxide thickness in isolation regions, allowing fabrication to proceed without compromising isolation effectiveness.
3Reliability
If additional processing steps are added to increase bulk oxide thickness, then oxide robustness is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The plate oxide deposition is merged with existing process steps in the fabrication sequence, utilizing standard CVD or PECVD equipment already present in the manufacturing line. This integration allows the bulk oxide thickness to be increased without adding significant processing complexity or cost, as the plate oxide formation is incorporated into the normal fabrication flow.
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 results in improved device performance by reducing capacitance between active devices and the substrate, increasing device-to-device isolation voltage, and maintaining the bulk oxide thickness without additional processing costs or steps.
Implementation Method 1
providing a plate oxide layer over the bulk oxide layer and over the substrate in the active region
Implementation Method 2
The localized oxidation of silicon (LOCOS) isolation method is used in many processes for manufacturing semiconductor integrated circuits
Data Source
AI summary
Semiconductor devices and methods for making such devices are described. The semiconductor devices are made by providing a semiconductor substrate with an active region, providing a bulk oxide layer in a non-active portion of the substrate, the bulk oxide layer having a first thickness in a protected area of the device, providing a plate oxide layer over the bulk oxide layer and over the substrate in the active region, forming a gate structure on the active region of the substrate, and forming a self-aligned silicide layer on a portion of the substrate and the gate structure, wherein the final thickness of the bulk oxide layer in the protected area after these processes remains substantially the same as the first thickness. The thickness of the bulk oxide layer can be increased without any additional processing steps or any additional processing cost. Other embodiments are described.