Airgap Formation in SiCOH ILD Layers Using UV Beam Masking
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Solution Overview
Problem
The existing airgap formation processes in semiconductor structures using etch back techniques face challenges such as unwanted oxidation of copper surfaces and nanocolumn transfer issues, along with conflicting requirements for dielectric constant and mechanical strength in ILD layers, which are not adequately addressed by current e-beam or UV beam exposure methods.
Innovation Solution
The method involves using a UV beam or e-beam in conjunction with blocking masks to selectively alter the properties of SiCOH ILD layers, allowing for region-specific exposures to optimize electrical and mechanical performance by de-methylating the material and controlling the dosage of energy exposure, thereby forming airgaps with reduced damage to the cap layer and improved mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxidizing plasma is used to damage SiCOH for airgap formation, then airgaps can be formed, but copper surface oxidation occurs as an unwanted side effect
Solution Approach 1:
A cap layer is introduced as an intermediary between the plasma etch process and the copper surface. This cap layer absorbs the plasma damage that would otherwise oxidize the copper, allowing airgap formation to proceed while protecting the metal surface from harmful oxidation effects.
Solution Approach 2:
The process segments the airgap formation into distinct stages: first forming nanocolumns through self-aligned etching, then using these nanocolumns as masks for subsequent plasma damage to the SiCOH. This segmentation allows selective damage while protecting copper regions through the cap layer intermediary.
2Manufacturing precision
If nanocolumns are transferred through cap material and ILD material for airgap formation, then airgaps can be created, but the transfer mask may not survive the imaging process and etch process becomes self-limiting
Solution Approach 1:
The nanocolumns formed in the cap layer serve a dual function: they act as the patterned mask structure and simultaneously protect the underlying ILD material during plasma damage. The self-aligned nature of the process means the nanocolumns automatically position themselves as the etch mask, eliminating the need for separate mask layers that would otherwise be consumed during imaging.
Solution Approach 2:
The nanocolumns are formed in advance through self-aligned etching before the plasma damage step. This preliminary formation ensures the mask structure is already in place and properly positioned, allowing it to survive the subsequent imaging and etch processes without requiring additional mask layers.
3Reliability
If e-beam or UV beam exposure is used to minimize dielectric constant for best electrical performance, then electrical performance is optimized, but mechanical strength of the ILD layer decreases
Solution Approach 1:
Different regions of the ILD layer are exposed to different e-beam or UV beam dosages to achieve locally optimized properties. Areas requiring optimal electrical performance receive exposure doses that minimize dielectric constant, while areas requiring mechanical strength receive lower doses or no exposure, preserving the material's cohesive strength in those regions.
Solution Approach 2:
The exposure dosage parameter is varied across different regions of the ILD layer. By controlling the energy dose delivered to specific areas, the material properties are tuned to achieve the desired balance between electrical performance (low dielectric constant) and mechanical strength, with each region optimized for its specific functional requirements.
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 enables the formation of airgaps with enhanced electrical and mechanical properties by minimizing unwanted damage and optimizing the properties of ILD layers, allowing for better performance in dense wiring and kerf regions, while maintaining the integrity of the cap layer and reducing the need for expensive processing methods.
Implementation Method 1
exposing a portion of a substrate which is not blocked to an energy source
Implementation Method 2
using a UV beam or an e-beam in conjunction with a mask to selectively alter the mechanical, chemical, and/or electrical properties of a substrate
Implementation Method 3
exposing a region of the substrate to an energy source... de-methylating the material and controlling the dosage of energy exposure
Data Source
AI summary
A method of forming airgaps is provided where a blocking mask is applied to a substrate to shield a portion of the substrate from a beam of energy. After irradiation, the blocking mask is removed and a capping material is applied to the substrate. Alternatively, the capping material may be applied before irradiation. The capping material is perforated to allow an etchant to pass therethrough to the substrate below the capping material. The exposed portions of the substrate are removed from underneath the capping material by etching. The capping material is then sealed leaving sealed airgaps within the substrate.