Germanium Microelectronic Element Fabrication via Anisotropic Etching
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Solution Overview
Problem
Current methods for producing device parts, such as germanium, using lateral epitaxial growth on silicon substrates often result in defects due to isotropic etching, leading to poor quality and orientation issues, especially in the proximity of the silicon interface.
Innovation Solution
A method involving selective etching with a surface reaction limitation system to create a confinement volume with a square cross-section, favoring etching speeds in the [110] and [1-10] directions over [010] and [100] directions, reducing defects by orienting the cavity walls along less defect-prone directions, and using epitaxial growth to fill the cavity with materials like germanium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If isotropic etching is used to create the confinement volume, then the etching process is simpler and more isotropic, but the resulting cavity has poor shape definition and generates defects at the silicon interface
Solution Approach 1:
The patent changes the etching parameters by using anisotropic etching conditions that exploit the crystallographic structure of silicon. By controlling etching direction and speed along specific crystal planes ([110], [1-10], [010], [100]), the method achieves precise square cross-section cavities with well-defined facets, eliminating the shape definition problems caused by isotropic etching while maintaining manufacturing feasibility
2Productivity
If lateral epitaxial growth is performed on silicon substrates, then germanium elements can be produced, but defects occur in the proximity of the silicon interface due to orientation problems
Solution Approach 1:
The patent applies local quality by creating cavities with specific local facet orientations that are optimized for defect-free epitaxial growth. The square cross-section geometry with well-defined crystallographic facets ensures that the germanium growth occurs along favorable orientations away from the silicon interface, locally eliminating defect formation zones while maintaining overall production efficiency
3Reliability
If additional lithography and etching steps are used to remove defective parts, then defect-free germanium portions can be obtained, but the manufacturing process becomes more complex with numerous steps
Solution Approach 1:
The patent applies preliminary action by pre-configuring the cavity geometry and orientation before epitaxial growth occurs. By creating the square cross-section confinement volume with properly oriented facets in advance, the method prevents defect formation during germanium growth, eliminating the need for subsequent defect removal steps and significantly simplifying the overall manufacturing process
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 defects and improves the shape definition of the germanium elements, achieving better quality and orientation by confining the growth to the least defect-prone facets, resulting in well-defined square cross-section elements with reduced defects compared to isotropic etching methods.
Implementation Method 1
an etching of the layer selectively inserted at the base layer and at the covering layer... by a surface reaction limitation etching system
Implementation Method 2
the etching is configured to produce an etching speed at least 25% greater in the crystallographic directions [110] and [1-10] than in the crystallographic directions [010] and [100]
Implementation Method 3
a filling is carried out, by a filling material constituting the element, of at least one part of the confinement volume by an epitaxial growth of the material from the side wall
Data Source
AI summary
The present invention relates to a method for producing an element of a microelectronic device on a support comprising a base layer, an inserted layer and a covering layer. The method includes forming a confinement volume including an etching of the inserted layer selectively to the base layer and to the covering layer, and filling, by a filling material constituting the element, of at least one part of the confinement volume by an epitaxial growth of the material from the side wall. The formation of the confinement volume comprises a formation of a hole through the whole thickness of the covering layer, and the etching is an anisotropic etching done by applying an etching on the inserted layer through the hole.