Halogen Sidewall Mask for Selective SiGe Epitaxy
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Solution Overview
Problem
Existing semiconductor device fabrication methods face challenges in achieving high selectivity during epitaxial growth of SiGe layers, leading to excessive OFF-state leakage current due to low selectivity between Si substrates and insulating layers, which complicates the manufacturing process and affects transistor performance.
Innovation Solution
A semiconductor device and fabrication method involving a gate electrode with a gate insulating film and a halogen element-containing insulating film on the side walls, where the halogen element content is higher in the top layer or has a gradient, preventing SiGe growth on the insulating film and ensuring selective epitaxial growth on the Si substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional insulating layers (Si oxide or Si nitride) are used for gate sidewall masks, then the manufacturing process is simple and well-established, but the selectivity between the insulating layer and Si substrate deteriorates, causing SiGe to grow on the side walls and increasing OFF-state leakage current
Solution Approach 1:
The insulating layer is divided into multiple layers with different compositions and thicknesses. The first insulating layer (closer to Si substrate) has higher etch selectivity to SiGe than the second insulating layer (closer to gate electrode), creating a gradient that prevents SiGe growth on side walls while maintaining manufacturing feasibility
Solution Approach 2:
Different regions of the insulating layer structure are assigned different properties: the lower layer has high selectivity to suppress SiGe growth at the critical substrate interface, while the upper layer has different characteristics optimized for its position, creating localized quality improvements throughout the structure
2Ease of manufacture
If the insulating layer structure is simplified to a single layer, then the manufacturing process is easier, but the ability to suppress SiGe growth on side walls is insufficient, leading to excessive OFF-state leakage current
Solution Approach 1:
The insulating layer is segmented into multiple sub-layers with progressively different compositions, where each layer contributes to the overall selectivity profile. This segmentation allows the structure to achieve high SiGe growth suppression capability while using standard manufacturing processes for each individual layer
3Productivity
If a single-composition insulating layer is used, then the manufacturing process is straightforward, but the latent period for SiGe growth on the insulating layer is insufficient, allowing SiGe to grow on side walls during epitaxial processing
Solution Approach 1:
The insulating layer structure is pre-configured with specific composition gradients and thickness ratios before the epitaxial growth process begins. This preliminary structuring ensures that the latent period for SiGe growth on side walls is sufficiently extended, preventing unwanted growth while maintaining efficient manufacturing throughput
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 effectively suppresses OFF-state leakage current and enables a manufacturing process suitable for mass production by ensuring high selectivity in SiGe growth, improving transistor performance and manufacturing efficiency.
Implementation Method 1
If semiconductor material gas adsorbs to a dangling bond or the like, a semiconductor nucleus begins to grow on the insulating layer after the elapse of a certain period of time (latent period).
Implementation Method 2
The method of making the SiGe layer selectively epitaxial-grow only on the Si substrate is adopted to make the SiGe layer epitaxial-grow in the source/drain regions
Data Source
AI summary
A semiconductor device in which selectivity in epitaxial growth is improved. There is provided a semiconductor device comprising a gate electrode formed over an Si substrate, which is a semiconductor substrate, with a gate insulating film therebetween and an insulating layer formed over sides of the gate electrode and containing a halogen element. With this semiconductor device, a silicon nitride film which contains the halogen element is formed over the sides of the gate electrode when an SiGe layer is formed over the Si substrate. Therefore, the SiGe layer epitaxial-grows over the Si substrate with high selectivity. As a result, an OFF-state leakage current which flows between, for example, the gate electrode and source/drain regions is suppressed and a manufacturing process suitable for actual mass production is established.