Two-Slope Contact Structure for Semiconductor Short Isolation
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Solution Overview
Problem
Semiconductor devices are prone to electrical shorts due to conductive materials connecting directly or across thin insulating materials, leading to device failure during manufacturing and usage, especially when transient high voltages cause insulating materials to break down, increasing parasitic power consumption and contact resistance.
Innovation Solution
Implementing a two-slope contact structure with a lower sidewall slope of 85° to 89.5° and an upper sidewall slope of 45° to 85°, decoupling the contact from the gate structure through a barrier layer, which helps in reducing the likelihood of electrical shorts and improving contact filling, thereby reducing resistance and parasitic power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional contact structure with uniform slope is used, then the manufacturing process is simpler, but the separation distance between contact and gate structure is insufficient, leading to electrical shorts
Solution Approach 1:
The contact structure is divided into two distinct segments: a lower portion with a first slope (85°-89.5°) and an upper portion with a second slope (45°-85°). This segmentation allows each portion to serve different functions - the lower portion provides adequate separation distance to prevent electrical shorts, while the upper portion facilitates proper contact filling and electrical connection.
Solution Approach 2:
The contact structure employs asymmetric slopes on different portions rather than a uniform slope throughout. The lower portion has a steeper slope (85°-89.5°) to maximize separation from the gate structure and prevent shorts, while the upper portion has a gentler slope (45°-85°) to optimize filling and electrical connection, creating an asymmetric profile that resolves the contradiction between short prevention and manufacturing simplicity.
2Area of stationary object
If the contact is placed closer to the gate structure, then the device area is reduced, but the insulating material thickness decreases, causing breakdown under transient high voltages
Solution Approach 1:
The solution transitions from considering only horizontal separation distance to incorporating vertical dimension through the two-slope configuration. By varying the slope angles in the vertical dimension, the contact structure achieves adequate electrical isolation (through the lower steep slope portion) while maintaining reduced horizontal footprint, effectively utilizing three-dimensional space to resolve the area versus reliability contradiction.
3Reliability
If a steep slope contact structure is used, then the separation distance is maximized, but the contact filling is poor, increasing contact resistance
Solution Approach 1:
The contact structure is segmented into two functional portions: the lower portion with steep slope (85°-89.5°) optimized for electrical isolation and separation distance, while the upper portion with gentler slope (45°-85°) optimized for contact filling quality. This segmentation allows each portion to excel at its specific function without compromising the other, resolving the contradiction between isolation and filling quality.
Solution Approach 2:
Different portions of the contact structure are given different local qualities through varying slope angles. The lower portion has a steep slope locally optimized for maximum separation and electrical isolation, while the upper portion has a gentler slope locally optimized for material flow and complete filling. This local differentiation of structural quality resolves the contradiction between isolation and filling.
Data Source
AI summary
Methods for making semiconductor device having improve contact structures including the operations of depositing a first dielectric material, depositing a barrier material over the first dielectric material, depositing a second dielectric material over the barrier material, etching a two-slope contact opening with an upper sidewall angle of the opening through the second dielectric material that is less than a lower sidewall angle of the opening through the first dielectric material, and filling the two-slope contact opening with a conductive material, the conductive material.