Progressive UV Cure for Porous ULK Films
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Solution Overview
Problem
Current methods for treating dielectric films with UV radiation to achieve desired mechanical properties and low dielectric constants are limited by high temperature requirements and potential damage to copper-containing devices, necessitating improved UV curing techniques that can modulate film properties at lower temperatures and reduce processing time.
Innovation Solution
The method involves sequential exposure of dielectric films to UV radiation at progressively shorter wavelengths, with the first exposure at wavelengths longer than 220 nm to remove porogen and minimize silicon-carbon bond formation, and a second exposure at 185 nm or longer to increase mechanical properties, allowing for a balance between dielectric constant and hardness without compromising film integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal processing is used to cure low-k dielectric films, then film stress and dielectric properties can be improved, but substrate temperature must be high (greater than 400-500°C) and exposure time is long (many hours), which may damage copper containing devices and limit temperature for temperature sensitive materials
Solution Approach 1:
The patent replaces thermal processing (heat-based curing) with UV radiation processing (light-based curing). This substitution allows the low-k dielectric film to be cured at lower temperatures (below 400-500°C) while still achieving the desired film stress and dielectric properties, thereby avoiding damage to copper containing devices and temperature sensitive materials.
Solution Approach 2:
The patent changes the curing parameter from temperature (thermal energy) to UV radiation wavelength and intensity (electromagnetic energy). By controlling UV exposure conditions such as wavelength, intensity, and duration, the film can be cured effectively without requiring high substrate temperatures, thus resolving the contradiction between achieving proper film properties and avoiding thermal damage.
2Reliability
If thermal processing is used to cure low-k dielectric films, then film stress and dielectric properties can be improved, but exposure time is long (many hours), which is unsuitable for mass manufacturing
Solution Approach 1:
The patent replaces thermal processing with UV radiation processing, which significantly reduces the curing time from many hours to much shorter durations. UV curing is a photochemical process that occurs rapidly upon exposure to UV light, making it suitable for mass manufacturing while still achieving the desired film stress and dielectric properties.
Solution Approach 2:
The patent employs controlled UV radiation exposure with specific wavelengths and intensities applied in a timed sequence. This periodic action allows precise control over the curing process, achieving complete film stress and dielectric property optimization in a fraction of the time required by thermal processing.
3Quantity of substance
If more porogen is removed and more pores are created to achieve lower dielectric constant, then k value decreases, but film becomes weaker and more likely damaged in subsequent processing
Solution Approach 1:
The patent uses UV radiation wavelength as a control parameter to selectively affect different chemical bonds in the film. By choosing specific UV wavelengths, the process removes porogen and creates pores (reducing dielectric constant) while simultaneously inducing cross-linking reactions that strengthen the film backbone, thus resolving the contradiction between achieving low k value and maintaining film strength.
Solution Approach 2:
The patent creates a composite structure within the dielectric film where porous regions (low k) are embedded in a cross-linked polymer matrix (high strength). The UV curing process selectively forms this composite architecture, where the cross-linked network provides mechanical strength while the porous regions maintain low dielectric constant, thus resolving the contradiction between porosity and strength.
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 results in a ULK film with up to 24% higher hardness and up to 3% lower dielectric constant compared to conventional UV curing, while maintaining the desired mechanical properties and reducing processing time, thus optimizing film performance for semiconductor manufacturing.
Implementation Method 1
A first exposure at wavelengths longer than about 220 nm or about 240 nm removes porogen while minimizing silicon-carbon bond formation and methyl group removal
Implementation Method 2
A second exposure at shorter wavelengths increases the mechanical properties to the desired level
Data Source
AI summary
Porous ULK film is cured with UV radiation at progressively shorter wavelengths to obtain ULK films quickly at a desired dielectric constant with improved mechanical properties. At longer wavelengths above about 220 nm or about 240 nm, porogen is removed while minimizing silicon-carbon bond formation. At shorter wavelengths, mechanical properties are improved while dielectric constant increases.