SOI Semiconductor Device Etching Process Divot Reduction
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Solution Overview
Problem
The reliability of semiconductor devices manufactured using SOI substrates is not adequately improved by existing techniques, as they face challenges in device isolation and etching processes that lead to defects such as divots in the device isolation region, affecting the overall performance and reliability.
Innovation Solution
A method of manufacturing semiconductor devices that involves a specific etching process sequence using different etching liquids to selectively remove and thin insulating layers and semiconductor layers, embedding a device isolation region in a trench, and controlling impurity implantation to prevent excessive etching and reduce divot formation, thereby enhancing the reliability of the semiconductor device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single etching liquid is used to remove insulating layers and semiconductor layers, then the etching process is simple, but it causes excessive etching and divot formation in the device isolation region
Solution Approach 1:
The etching process is divided into multiple sequential steps using different etching liquids. First, a boron-containing etching liquid is used to selectively etch the semiconductor layer while sparing the insulating layer. Then, a fluorine-containing etching liquid is used to etch the insulating layer. This segmentation allows precise control over which layer is etched at each step, preventing divot formation in the device isolation region while maintaining manufacturing feasibility.
Solution Approach 2:
Different etching liquids with specific chemical properties are applied at different stages to achieve local etching effects. The boron-containing etching liquid provides selective etching for semiconductor material, while the fluorine-containing etching liquid targets insulating layer material. This local quality approach ensures that etching occurs precisely where needed without affecting adjacent regions, thereby improving manufacturing precision.
2Ease of operation
If the insulating layer is completely removed to expose the semiconductor substrate, then subsequent processing is simplified, but divots form in the device isolation region reducing reliability
Solution Approach 1:
The semiconductor layer is selectively removed in advance using a boron-containing etching liquid before the insulating layer is etched. This preliminary action creates a protective configuration where the insulating layer remains intact in the device isolation region, preventing divot formation during subsequent etching steps. The preliminary selective removal simplifies later processing while maintaining reliability.
3Reliability
If existing STI techniques are used on SOI substrates, then device isolation is achieved, but reliability is not adequately improved due to divot defects
Solution Approach 1:
The chemical composition parameters of the etching liquids are changed between etching steps. A boron-containing etching liquid is used first to etch semiconductor material, followed by a fluorine-containing etching liquid to etch the insulating layer. This parameter change in etching chemistry enables selective removal of materials without causing divot defects, thereby improving device reliability while maintaining effective isolation.
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 method improves the reliability of semiconductor devices by reducing the occurrence and depth of divots in the device isolation region, ensuring precise etching and optimal layer thickness, which enhances the performance and reliability of the semiconductor device.
Implementation Method 1
In the step (c), the semiconductor layer in the first region is removed by wet etching using a first etching liquid
Implementation Method 2
In the step (d), the insulating layer in the first region and the first insulating film in the second region are removed by wet etching using a second etching liquid different from the first etching liquid
Implementation Method 3
implanting an impurity into the semiconductor substrate in the second region to form a first semiconductor region
Data Source
AI summary
Reliability of a semiconductor device is improved. Prepared is a substrate in which an insulating layer, a semiconductor layer, and an insulating film are laminated on a semiconductor substrate, and a device isolation region is embedded in a trench. The insulating film in a bulk region is removed; the semiconductor layer in the bulk region is removed by using a first etching liquid; and thereafter the insulating film in the SOI region and the insulating layer in the bulk region are thinned by using a second etching liquid different from the first etching liquid. An impurity is implanted into the semiconductor substrate in the SOI region, and thereafter the insulating film in the SOI region and the insulating layer in the bulk region are removed. An etching speed of each of the insulating film and the insulating layer due to the first etching liquid is smaller than an etching speed of the semiconductor layer by using the first etching liquid. An etching speed of each of the insulating film and the insulating layer due to a second etching liquid is higher than the etching speed of each of the insulating film and the insulating layer due to the first etching liquid.