Sacrificial Plugs for Through-Substrate Via Formation
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Solution Overview
Problem
The conventional process for forming through-substrate vias in semiconductor devices is prone to variations in hole depth and metal smearing, leading to electrical shorts and increased manufacturing time due to the use of soft metals like copper, which diffuses across the substrate during backgrinding.
Innovation Solution
The introduction of a sacrificial plug, such as a polysilicon plug, is used to compensate for depth variations and protect the via during thinning, which can be removed to form a contact region for a conductive pillar or damascene structure, reducing metal smearing and improving device performance and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft metals like copper are used to form through-substrate vias, then electrical conductivity is improved, but metal smearing occurs during backgrinding causing electrical shorts
Solution Approach 1:
A sacrificial plug made of harder material (such as silicon oxide or silicon nitride) is placed at the bottom of the via hole as an intermediary protective layer. This sacrificial plug prevents the soft metal filling material from smearing during backgrinding by providing a mechanically stable base, while still allowing the via to maintain its electrical conductivity function.
Solution Approach 2:
The sacrificial plug is formed in advance before the metal filling material is deposited. This preliminary action of placing the protective sacrificial plug at the bottom of the via hole prevents metal smearing from occurring during subsequent backgrinding operations, thereby eliminating electrical shorts before they can happen.
2Manufacturing precision
If backgrinding is performed to expose vias through the backside, then via exposure is achieved, but variations in hole depth cause inconsistent via formation
Solution Approach 1:
The sacrificial plug is formed in advance at the bottom of the via hole with a predetermined height that compensates for expected depth variations. This preliminary structure provides a consistent reference plane for subsequent processing steps, ensuring that vias are properly exposed regardless of initial hole depth variations.
Solution Approach 2:
The sacrificial plug changes the physical parameters of the via structure by providing a standardized bottom reference level. This allows the backgrinding process to proceed with consistent depth control, transforming the variable hole depth situation into a controlled process where the sacrificial plug height compensates for initial variations.
3Reliability
If multi-step processing is used to form through-substrate vias, then via formation is achieved, but manufacturing time is increased
Solution Approach 1:
The formation of the sacrificial plug is merged with the existing via formation process flow, combining multiple functions into a integrated sequence. The sacrificial plug formation, metal filling, and backgrinding protection are coordinated as a unified process rather than separate operations, reducing total manufacturing time while maintaining via formation quality.
Data Source
AI summary
Methods for making semiconductor devices are disclosed herein. A method configured in accordance with a particular embodiment includes forming one or more openings in a front side of the semiconductor device and forming sacrificial plugs in the openings that partially fill the openings. The method further includes further filling the partially filled openings with a conductive material, where individual sacrificial plugs are generally between the conductive material and a substrate of the semiconductor device. The sacrificial plugs are exposed at a backside of the semiconductor device. Contact regions can be formed at the backside by removing the sacrificial plugs.