Interlayer Dielectric Gap-Fill via SACVD and Buffer Layer
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Solution Overview
Problem
The existing deposition techniques for forming dielectric interlayers in integrated circuits, such as PECVD, struggle to reliably fill the gaps between densely packed circuit elements, leading to void formation and reliability concerns, especially as feature sizes shrink below 30 nm, and result in non-uniformities and inferior material characteristics.
Innovation Solution
A method involving a sub-atmospheric CVD process for enhanced gap filling, combined with a conformal buffer layer and controlled etch processes to reduce excess material and uniformity issues, ensuring reliable and uniform deposition of interlayer dielectric materials with improved mechanical stability and reduced moisture absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high rate PECVD techniques are used for deposition of silicon dioxide, then deposition rate is improved, but gap-fill capability deteriorates leading to void formation
Solution Approach 1:
The dielectric interlayer is divided into multiple deposition stages using different techniques. First, a low-k dielectric material is deposited by PECVD at a high rate to cover most of the structure. Then, a gap-fill dielectric material is deposited by a different technique (such as spin-on-glass or flowable CVD) specifically to fill the remaining gaps between closely spaced lines. This segmentation allows each material to perform its specialized function without compromising the other.
Solution Approach 2:
An intermediary gap-fill dielectric material is introduced between the high-rate PECVD deposited dielectric and the closely spaced lines. This intermediary material has superior gap-fill capability and is deposited using a technique specifically suited for filling narrow spaces, thereby mediating between the high productivity requirement and the reliability requirement for complete gap filling.
2Length of moving object
If feature sizes are reduced below 30 nm, then device scaling is improved, but gap-fill capability deteriorates due to insufficient deposition techniques
Solution Approach 1:
Different regions of the structure receive different dielectric materials with locally optimized properties. The regions between closely spaced lines (where gap-filling is critical) receive a specialized gap-fill dielectric material with superior flow and fill characteristics, while other regions receive the standard low-k dielectric material. This local quality differentiation ensures that each region gets the material best suited for its specific requirements.
Solution Approach 2:
The dielectric interlayer is formed as a composite structure combining multiple dielectric materials. The composite includes a primary low-k dielectric material deposited by PECVD and a secondary gap-fill dielectric material deposited by a specialized technique. The combination of these materials provides both the low dielectric constant properties needed for high-speed devices and the superior gap-fill capability required for sub-30 nm features.
3Manufacturing precision
If PECVD techniques are used for silicon dioxide deposition, then conformality is improved, but gap-fill capability deteriorates
Solution Approach 1:
The dielectric deposition process is segmented into two distinct steps: first, a conformal dielectric layer is deposited by PECVD to ensure uniform coverage and good adhesion; second, a gap-fill dielectric material is deposited using a technique specifically designed for filling narrow gaps. This segmentation allows each deposition step to optimize for its specific purpose without compromise.
Solution Approach 2:
An intermediary gap-fill dielectric material is introduced that acts as a mediator between the conformal PECVD dielectric layer and the closely spaced lines. This intermediary material has superior gap-fill properties and is deposited using a technique optimized for filling narrow spaces, thereby resolving the contradiction between conformality and gap-fill capability.
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 maintains enhanced gap filling capabilities while minimizing the negative effects of inferior material characteristics and deposition-specific non-uniformities, resulting in more reliable and uniform interlayer dielectric structures, thereby improving the overall performance and stability of semiconductor devices.
Implementation Method 1
forming a first interlayer dielectric material above the circuit elements and the etch stop material by a first deposition process designed to substantially fill spaces formed between the densely packed line features
Implementation Method 2
forming a conformal buffer layer
Data Source
AI summary
By removing excess material of an interlayer dielectric material deposited by SACVD, the gap filling capabilities of this deposition technique may be exploited, while, on the other hand, negative effects of this material may be reduced. In other aspects, a buffer material, such as silicon dioxide, may be formed prior to depositing the interlayer dielectric material on the basis of SACVD, thereby creating enhanced uniformity during the deposition process when depositing the interlayer dielectric material on dielectric layers having different high intrinsic stress levels. Consequently, the reliability of the interlayer dielectric material may be enhanced while nevertheless maintaining the advantages provided by an SACVD deposition.