Semiconductor Device Recess Design for Crack Prevention
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Solution Overview
Problem
The semiconductor device experiences cracks in the third interlayer insulating film due to the formation of recesses during the anisotropic dry etching process of thick aluminum wiring layers, leading to reduced reliability.
Innovation Solution
The introduction of a recess with inclined side surfaces in the interlayer insulating film between the wiring layers, where the side surfaces of the recess decrease in width from the upper surface to the lower surface, helps to relax residual stress and prevent crack formation by modifying the dry etching process to include multiple overetching steps with varying high-frequency power and etching conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If anisotropic dry etching is performed to form thick aluminum wiring layers, then the wiring layer thickness is increased to allow large current, but cracks are generated in the interlayer insulating film due to recess formation, reducing device reliability
Solution Approach 1:
A protective film is formed on the interlayer insulating film before the dry etching process. This protective film prevents crack generation during the etching process that forms recesses for thick aluminum wiring layers. The protective film is removed after etching is complete, having served its protective function throughout the critical process step.
Solution Approach 2:
The protective film acts as a cushioning layer that absorbs or mitigates the harmful effects of the dry etching process on the interlayer insulating film. By placing this protective layer beforehand, the film prevents stress concentration and crack propagation that would otherwise occur during recess formation for thick wiring layers.
2Ease of manufacture
If overetching is performed to form recesses in the interlayer insulating film between adjacent wirings, then wiring separation is improved to prevent short-circuiting, but cracks are generated from the recess starting points, lowering reliability
Solution Approach 1:
The protective film is formed on the interlayer insulating film before the overetching process begins. This preliminary protective layer prevents crack generation during the overetching step that creates recesses for wiring separation. The protective film remains in place throughout the entire etching and overetching sequence, protecting the underlying insulating film from stress-induced cracking.
Solution Approach 2:
The protective film serves as an intermediary layer between the etching process and the interlayer insulating film. It mediates the interaction by absorbing the mechanical stress and chemical effects of overetching, preventing direct damage to the insulating film while still allowing the recess formation to proceed for proper wiring separation.
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 reduces the stress applied to the corner portions of the wiring, preventing cracks and enhancing the reliability of the semiconductor device by ensuring proper connection and preventing short-circuiting between adjacent wirings.
Implementation Method 1
the aluminum layer is processed by the anisotropic dry etching method, and in the anisotropic dry etching process, the aluminum layer is processed to form a large number of wirings, and then overetching is performed to form recesses in the surface of the interlayer insulating film between adjacent wirings
Data Source
AI summary
The semiconductor device has a wiring M 2, an interlayer insulating film IL3 formed on the wiring M 2, and two wirings M 3 formed on the interlayer insulating film IL3, and the wiring M 3 is connected to the wiring M 2 by a conductor layer PG2 formed in the interlayer insulating film IL3. A recess CC3 is formed on the upper surface IL3a of the interlayer insulating film IL3, and the recess CC3 is defined by a side surface S 31 connected to the upper surface IL3a and a side surface S 32 connected to the side surface S 31, and the side surface S 32 is inclined so that the width WC3 of the recess CC3 decreases in the direction from the upper surface IL3a of the interlayer insulating film IL3 toward the upper surface IL2a of the interlayer insulating film IL2.