Porous Low-k Layer Density Gradient for Etching Profile Control
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Solution Overview
Problem
Porous low-k layers in interconnect structures often cause undesired etching profiles, such as kink profiles, due to their low density and differing etching rates with adjacent non-porous materials, which can interfere with the filling of conductive materials in damascene processes.
Innovation Solution
A CVD process is used to form a porous low-k layer with a top portion and bottom portion having higher densities than the body portion, ensuring the etching rates match those of the hard mask and cap layers, thereby preventing kink profiles. This is achieved by adjusting deposition parameters like porogen precursor flow rates or sizes in different stages of the CVD process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a porous low-k layer is formed with low density to achieve low dielectric constant, then the dielectric constant is reduced below 2.0, but an undesired etching profile (kink profile) occurs due to etching rate difference with adjacent films
Solution Approach 1:
The patent applies local quality by creating a density gradient within the porous low-k layer, where the top portion has higher density (closer to non-porous) and the bottom portion has lower density (more porous). This spatial variation in density allows the top portion to match the etching rate of adjacent hard mask layers, preventing kink profiles, while the bottom portion maintains low dielectric constant for RC delay reduction.
Solution Approach 2:
The patent changes the density parameter of the porous low-k layer by controlling porogen precursor flow rates during CVD deposition. By adjusting the porogen precursor flow rate to be higher in early stages (creating lower density) and lower in later stages (creating higher density), the patent achieves a density gradient that resolves the etching profile issue while maintaining low dielectric constant.
2Quantity of substance
If a porous low-k layer with uniform low density is formed, then the dielectric constant is reduced, but the etching rate difference between the porous low-k layer and adjacent non-porous materials causes kink profiles that interfere with conductive material filling
Solution Approach 1:
The patent creates a density gradient where the top portion has higher density matching adjacent layers, ensuring smooth etching profiles that facilitate proper conductive material filling in damascene processes, while the bottom portion maintains low density for low dielectric constant.
3Quantity of substance
If the porogen precursor flow rate is increased to create more porous structure, then the dielectric constant is reduced, but the etching rate difference with adjacent films increases causing worse etching profiles
Solution Approach 1:
The patent applies periodic action by varying the porogen precursor flow rate in stages during CVD deposition: higher flow rates in early stages to create porous structure for low dielectric constant, and lower flow rates in later stages to create higher density top portion for matching etching rates with adjacent films.
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
The method prevents kink profiles during etching, allowing for smoother filling of conductive materials and improving the quality of interconnect structures by ensuring consistent etching rates across layers.
Implementation Method 1
A CVD process in which a framework precursor and a porogen precursor are supplied is performed to a substrate
Data Source
AI summary
A structure of a porous low-k layer is described, comprising a bottom portion and a body portion of the same atomic composition, wherein the body portion is located on the bottom portion, and the bottom portion has a density higher than the density of the body portion. An interconnect structure is also described, including the above porous low-k layer, and a conductive layer filling up a damascene opening in the porous low-k layer.