Pseudo Hybrid ULK Interconnect Structure for Trench Depth Control
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Solution Overview
Problem
Conventional dual damascene fabrication processes for low-k interlayer dielectric structures face challenges with inconsistent trench depth control, increased total capacitance, and reliability concerns due to additional interfaces between different dielectric layers.
Innovation Solution
A method involving the deposition of a first ultra low-k dielectric layer, its curing to form a via level layer, and a second uncured trench level layer, where the trench opening is etched using chemical differences between the cured and uncured layers to control depth, followed by curing the trench layer to eliminate interfaces and achieve a homogenous dielectric stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dual damascene fabrication processes use multiple different dielectric layers with different etch rates to control trench depth, then trench depth control is achieved, but total capacitance increases and additional interfaces are introduced that worsen reliability
Solution Approach 1:
The patent changes the physical-chemical state of the dielectric material by introducing a curable low-k material that transitions from uncured to cured state. This parameter change (chemical composition) creates etch selectivity without requiring different dielectric layers, thus controlling trench depth while avoiding additional interfaces that would harm reliability
Solution Approach 2:
The patent utilizes phase transition (curing process) of the low-k dielectric material to create distinct etchable regions. The uncured portion etches at a different rate than the cured portion, enabling precise trench depth control through the etching process while maintaining a homogeneous dielectric structure that eliminates interface-related reliability issues
2Ease of manufacture
If conventional dual damascene processes assume stable etch rate to control trench depth, then process simplicity is maintained, but etch rate sensitivity to chamber condition and material properties causes inconsistent depth control
Solution Approach 1:
The patent introduces a controllable parameter change (curing state) that actively compensates for etch rate sensitivity. By controlling the degree of curing in different regions, the process achieves consistent trench depth control even when absolute etch rates vary due to chamber conditions or material property variations
Solution Approach 2:
The patent performs preliminary curing of the low-k dielectric material in specific regions before the trench etching process. This preliminary action creates the necessary etch selectivity in advance, ensuring that the subsequent etching process achieves consistent depth control regardless of variations in etch rate caused by chamber conditions
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 enhances process control, reduces trench depth variation, and improves device performance by eliminating additional interfaces and maintaining a low dielectric constant, thereby addressing the limitations of conventional processes.
Implementation Method 1
the different chemical composition between the cured via level dielectric layer and the uncured trench level dielectric layer may be used to generate an endpoint signal for enhanced trench etch depth control
Implementation Method 2
at least a portion of the via level dielectric layer is cured to form a cured via level dielectric layer
Data Source
AI summary
A method and apparatus are described for fabricating an ultra low-k interconnect structure by depositing and curing a first via layer (43) of ultra low dielectric constant (ULK) material, depositing a second uncured trench layer (51) of the same ULK material, selectively etching a via opening (62) and trench opening (72) with a dual damascene etch process which uses a trench etch end point signal from the chemical differences between uncured trench layer (51) and the underlying cured via layer (43), and then curing the second trench layer (83) before forming an interconnect structure (91) by filling the trench opening (72) and via opening (62) with an interconnection material so that there is no additional interface or higher dielectric constant material left behind.