Semiconductor Substrate With Shallow And Deep Trench Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The integration of photonic and electronic devices on a common semiconductor substrate is hindered by the need for different oxide thicknesses for electrical and optical isolation, leading to complex processing and increased costs due to the use of silicon-on-insulator (SOI) substrates, which are expensive and limited in supply.
Innovation Solution
A method is developed to form a semiconductor substrate with shallow trench electrical isolation and deep trench optical isolation using a common reticle to create a hard mask for etching, allowing for the fabrication of both electronic and photonic devices on a non-SOI substrate with a single etch process, utilizing a pad oxide, hard mask, and selective oxide filling and etching to achieve the necessary isolation depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick buried oxide (BOX) is used in SOI substrate for photonic devices, then optical isolation is improved, but heat dissipation is worsened
Solution Approach 1:
The substrate is divided into two distinct regions: an SOI region with thin BOX for electronic devices requiring good heat dissipation, and a non-SOI region with thick oxide for photonic devices requiring optical isolation. This segmentation allows each device type to have optimized substrate conditions without compromising the other.
Solution Approach 2:
Different oxide thicknesses are provided in different locations on the same substrate. The SOI region has thin BOX (100-200 nm) for electrical isolation suitable for electronic devices, while the non-SOI region has thick oxide (2.0-3.0 μm) for optical isolation suitable for photonic devices. This local quality variation resolves the contradiction by providing location-specific substrate properties.
2Temperature
If a thin buried oxide (BOX) is used in SOI substrate for electronic devices, then heat dissipation is improved, but optical isolation is worsened
Solution Approach 1:
The substrate is divided into two distinct regions: an SOI region with thin BOX for electronic devices requiring good heat dissipation, and a non-SOI region with thick oxide for photonic devices requiring optical isolation. This segmentation allows each device type to have optimized substrate conditions without compromising the other.
Solution Approach 2:
Different oxide thicknesses are provided in different locations on the same substrate. The SOI region has thin BOX (100-200 nm) for electrical isolation suitable for electronic devices, while the non-SOI region has thick oxide (2.0-3.0 μm) for optical isolation suitable for photonic devices. This local quality variation resolves the contradiction by providing location-specific substrate properties.
3Reliability
If SOI substrates are used for integration of photonic and electronic devices, then substrate support is improved, but production cost is worsened
Solution Approach 1:
A single non-SOI substrate serves multiple functions: it provides mechanical support for the entire device structure, enables formation of both SOI and non-SOI regions, and facilitates integration of both electronic and photonic devices. This universal substrate approach eliminates the need for separate SOI substrates, reducing costs while maintaining structural integrity.
Solution Approach 2:
Instead of using expensive pre-fabricated SOI substrates, the patent creates the necessary SOI structure with thin BOX on a standard non-SOI substrate through a specialized fabrication process. This 'copies' the functional benefits of SOI substrates without the associated cost and supply limitations.
4Reliability
If different oxide thicknesses are provided for electronic and photonic devices, then device performance is improved, but process complexity is worsened
Solution Approach 1:
A pad oxide layer is formed on the non-SOI substrate before creating the isolation trenches. This preliminary oxide layer serves as a foundation for subsequent processing steps and enables controlled formation of different oxide thicknesses in different regions through selective etching and filling operations.
Solution Approach 2:
A hard mask layer is used as an intermediary tool to define and control the patterns of isolation trenches during fabrication. The hard mask enables precise patterning of trenches that will eventually contain different oxide thicknesses, simplifying the overall process by providing a controllable intermediate step in the fabrication sequence.
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 simplifies the substrate formation process, reduces production costs, and enables effective electrical and optical isolation for both electronic and photonic devices on a common substrate, overcoming the limitations of SOI substrates by allowing for the integration of CMOS circuits and photonic devices with reduced optical signal loss and improved heat dissipation.
Implementation Method 1
forming a pad oxide on the non-SOI substrate
Implementation Method 2
The oxide filling material may be deposited using physical vapor deposition (PVD) or chemical vapor deposition (CVD
Implementation Method 3
The oxide filling material may be deposited using physical vapor deposition (PVD) or chemical vapor deposition (CVD
Data Source
Figure 1~5
Figure 6~8
AI summary
A method of forming a substrate with isolation areas suitable for integration of electronic and photonic devices is provided. A common reticle and photolithographic technique is used to fabricate a mask defining openings for etching first and second trench isolation areas in a substrate, with the openings for the second trench isolation areas being wider than the openings for the first trench isolation areas. The first and second trench isolation areas are etched in the substrate through the mask. The second trench isolation areas are further etched to the deeper than the first trench isolation areas. The trench isolation areas are filled with oxide material. Electrical devices can be formed on the substrate and electrically isolated by the first trench isolation areas and photonic devices can be formed over the second trench isolation areas and be optically isolated from the substrate.