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In this paper, we report on the development of Cu pillars and their impact on the subsequent thinning process for 3D applications. As the Cu pillars have a height of tens of microns (typically between 50–100µm), controlling the total thickness variation (TTV) after wafer thinning is becoming even more challenging. The Cu pillars are processed after completion of the Back End of Line (BEOL) with a...
Two different material-selective Self assembled monolayers (SAMs) were successfully deposited on Cu and SiO2 structures that mimic the Dual Damascene integration scheme. A two-step SAM coating process is presented. First, a “sacrificial” SAM is deposited at the Cu bottom and secondly, a “barrier” SAM at the SiO2 surface. The order in the SAMs deposition sequence and the differential thermal release...
The establishment of a cost-effective Through Silicon Vias (TSV) fabrication process integrated to a CMOS flow with industrially available tools is of high interest for the electronics industry because such process can produce more compact systems. We present a 300mm industry-compliant via-middle TSV module, integrated to an advanced high-k/metal gate CMOS process platform. TSVs are fabricated by...
As scaling becomes increasingly difficult, 3D integration has emerged as a viable alternative to achieve the requisite bandwidth and power efficiency challenges. However mechanical stress induced by the through silicon vias (TSV) is one of the key constraints in the 3D flow that must be controlled in order to preserve the integrity of front end devices. For the first time an extended and comprehensive...
Thin wafer handling has become a very challenging topic of emerging 3D technologies, and temporary wafer bonding to a carrier support wafer is one way to guarantee the required mechanical stability and rigidity to the thin wafer during subsequent backside processing. The temporary bonding approach followed by Imec is based on the adhesive material HT10.10 from Brewer Science (WaferBond® HT-10.10)...
In this study, we report a new concept of through silicon via for 3D applications requiring ultra-low coupling capacitance. The challenges linked to the integration of such structure, as well as preliminary results on stress level and distribution in the TSV are addressed in details below.
We describe the design challenges for a low-cost 130nm 3D CMOS technology with 5μm diameter at 10μm pitch Cu-TSV. We investigate electrical, thermal and thermo-mechanical issues encountered in 3D. The electrical yield and ESD of TSVs is reviewed and designers are advised how to ensure yield and reliability. For thermal and thermo-mechanical we'll indicate based on experimental characterization, the...
3D integration has the potential to alleviate the performance limitations that CMOS scaling is facing provided that it preserves the integrity of both front end and back end devices and constituting materials. The impact of wafer thinning and of the proximity of through silicon via on active devices, back end structures, ring oscillators and mixed signal circuit are reported for the first time for...
In this paper, we investigate the electrical behavior of TSV with increasing temperatures (25-150°C). TSV capacitance, leakage current and TSV resistance with varying temperatures are reported. TSV C-V characteristics are analyzed to extract the oxide charges. It is confirmed that the depletion behavior of TSV can be exploited to reduce TSV capacitance even at higher temperatures. In addition, lumped...
The paper describes the design challenges for a low-cost 3D Cu-TSV technology. Based on experimental characterization, we'll indicate the importance of extending the chip package co-design flow with thermo-mechanical simulations of the chip stack. We propose a new design flow hereto which leverages information captured by “smart mechanical samples” .
We investigate key design issues of a low-cost 3D Cu-TSV technology: impact of TSV on MOS devices and interconnect, reliability, thermal hot spots, ESD, signal integrity and impact on circuit performance. We experimentally verify their importance and propose changes in current design practices to enable low-cost systems.
In this paper we demonstrate functional 3D circuits obtained by a 3D Stacked IC approach using both Cu Through Silicon Vias (TSV) First and cost effective solution Die-to-Wafer Hybrid Collective bonding. The Cu TSV-First process is inserted between contact and M1. The top die is thinned down to 25 ??m and bonded to the landing wafer by Hybrid Bonding. Measurements and simulations of the power delay...
In this study, we report on the processing and the electrical characterization of a 3D-WLP TSV flow, using a polymer-isolated, Cu-filled TSV, realized on thinned wafers bonded to temporary carriers. A Cu/Sn microbump structure is integrated in the TSV process flow and used for realizing a two-die stack. Before TSV processing, the Si wafers are bonded to temporary carriers and thinned down to 50 mum...
In this paper we demonstrate functional 3D circuits obtained by a 3D Stacked IC approach using Die-to-Wafer Hybrid Collective bonding with Cu Through Silicon Vias (TSV). The Cu TSV process is inserted between contact and M1 of our reference 130 nm CMOS process on 200 mm wafers. The top die is thinned down to 25 mum and bonded to the landing wafer by a combination of polymer bonding and copper to copper...
The interest in 3D packaging and specifically TSV processes has grown significantly in the past few years, with nearly every major chip manufacturer announcing plans to develop and implement this technology. As TSV process flows become stabilized, a number of metrology and inspection issues and opportunities have arisen. Many of these challenges are novel to the industry due to the relatively large...
The concept of 3D integration aims at low cost and high yield processes. For this reason, cleanliness is a concern in process steps such as bonding. However, preceding process steps like dicing and die-level handling are traditionally associated with high levels of contamination. Usually a clean prior to the bonding step will be required. We discuss the requirements of the cleaning process, and explore...
The time and temperature dependence of Stress-Induced-Voiding below and in copper VIA's with a diameter of 80 nm integrated in a k = 2.5 material was studied. The focus was on the early phase of the voiding process. To accelerate the degradation, test structures with big metal plates below and/or above the VIA were used. We found two degradation mechanisms in which one dominated below and the other...
Interconnect solutions for advanced technology nodes using PECVD techniques for low-k deposition require the use of porogen-based process with post deposition UV cure. By using two different UV cure lamps (A, B) in combination with different porogen loads, three different micro-porous low-k films are developed: Aurora?? ELK HM (k~2.5; porosity (P) ~25%), Aurora?? ELK A (k~2.3; P~34%) and Aurora??...
Surface hydrophilisation of pristine low-k (ULK) is known as a CMP-induced damage mechanism. This phenomenon already enhanced by several factors (e.g. mechanical polishing action, solid content in the slurry, pH of the slurry solution, presence of organic residues, etc ...) extends to bulk hydrophilisation when polishing metal/ULK systems. The degree of bulk hydrophilisation depends on the nature...
Novel in-line characterization techniques such as SAWs and a near-field microwave probe are combined to more widely studied physical and electrical off-line methodologies for the evaluation of dielectric damage. Physical characterization of the damage with EFTEM and SAWs and capacitance evaluation at 100kHz and 4GHz point out the presence of different types of low-k damage depending on the chosen...
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