Methods for forming dense dielectric layer over porous dielectrics

Abstract

Methods for forming a dense dielectric layer over the surface of an opening in a porous inter-layer dielectric having an ultra-low dielectric constant are disclosed. The disclosure provides methods for exposing the sidewall surface and the bottom surface of the opening to a plurality of substantially parallel ultra-violet (UV) radiation rays to form a dense dielectric layer having a substantially uniform thickness over both the sidewall surface and the bottom surface.

Description

BACKGROUND OF THE DISCLOSURE[0001]1. Technical Field[0002]The disclosure relates generally to semiconductor fabrication, and more particularly, to forming a dense dielectric layer over the surface of an opening in a porous inter-layer dielectric having an ultra-low dielectric constant.[0003]2. Background Art[0004]Recent rapid advancement in semiconductor technology has brought the advent of very large scale integrated (VLSI) as well as ultra large scale integrated (ULSI) circuits, resulting in integration of more devices into smaller areas on a single semiconductor substrate. In order to further enhance performance of the VLSI and / or ULSI circuits, ultra-low dielectric constant (ULK) materials, such as porous materials, are being used as inter-level dielectrics (i.e., via level dielectrics) and intra-level dielectrics (i.e., line level dielectrics), both referred to as ILDs, herein. ILDs, alternatively known as inter-metal dielectrics (IMDs), are used to further reduce capacitance s...

AI Technical Summary

Benefits of technology

[0010]A second aspect of the disclosure provides a method comprising: forming an opening in a inter-layer dielectric (ILD) on a wafer, the ILD having an ultra-low dielectric constant, wherein the opening has a sidewall surface and a bottom surface; and exposing the sidewall surface and the bottom surface to a plurality of substantially parallel ultra-violet (UV) radiation rays to form a dense dielectric layer having a substantially uniform thickness over both the sidewall surface and the bottom surface, and wherein the exposing comprises: exposing the bottom surface to the plurality of substantially parallel UV radiation rays at a first angle of incidence; and exposing the sidewall surface to the plurality of substantially parallel UV radiation rays at a second angle of incidence different than the first angle of incidence, the exposure to the bottom surface and the sidewall surface being substantially uniform.

[0011]A third aspect of the disclosure provides a method comprising: forming an opening in an inter-layer dielectric (ILD) on a wafer, the ILD having an ultra-low d

Problems solved by technology

This penetration or intrusion of metal into porous ULK ILDs may cause performance degradation of the metal interconnects formed thereon, as well as degradation of the insulating capability of the ILD.

In a worst case, this insulating degradation causes shorting between neighboring elements of the interconnect structure.

The interconnected porosity poses a challenge for the application of advanced liner processes (e.g., thermal and ion-induced atomic layer deposition (iALD), or plasma-enhanced chemical vapor deposition (PECVD)) due to chemical precursors penetrating into the ILD, resulting in degraded back-end-of-line (BEOL) performance, including increased leakage and reduced reliability.

This approach, however, is not ideal because of the non-uniformity of coverage within and across different features (e.g., sidewall versus the bottom of the opening, different size openings, pattern density dependence, etc.), and the additional burden on the liner process to clean up the bottom of vias to ensure good electrical contact.

In the case that the ULK ILD has no interconnected pores, the densification of the surface layer is ineffective.

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