Research Projects

Overview

This page describes selected CMC research that was conducted between 2002 and 2006. Some of these projects and initiatives are ongoing.

The Effect of Medium on Particle Adhesion and Removal

The objects of this task is study : 1) the effect of deposition method on particle adhesion and removal, i.e., to study the effect of way that particle deposits onto the substrate, on the final particle adhesion force; 2) accurate prediction of electrical double layer force; 3) the effect of aging (time) on particle adhesion and removal.

The Effect of Aging (Time) on Particle Adhesion and Removal

The objective of this project is to study the particle adhesion behavior changing with time for different type of particle, of different size, using different deposition method, and on different substrate. Previous study , showed that the contact area between PSL particle and silicon substrate increases with the time and this correlates with the decrease of the removal efficiency with time.

Removal of Nanoparticles Using High Frequency Acoustic Streaming

Study the removal of nanoparticles using high frequency acoustic streaming. Study the effect of power, cleaning time and temperature.

The Effect of Water and Alcohol on the Adhesion of Particles

• Verify models used for particle removal by rolling mechanism,
• Study the effect of different particle deposition methods on particle adhesion and removal,
• Reduce uncertainties in particle adhesion and removal.

Metrology of Nanoparticles in Cleaning Applications

Fluorescent particle imaging allows particle detection to a precision about an order of magnitude greater than the optical light resolution. The use of fluorescent microscopy enables 3D particle detection, which is the only instrument with such capability. The objective of this research is to provide a metrology to enable the investigation of particle removal from structured surfaces.

Modeling Study of Removal of Submicron Particles from Deep Trenches

The objective of this research is to get a better understanding of the mechanism of megasonic cleaning process. Experiments with 500 micron deep trenches and fluorescent particles have been conducted. Computational fluid dynamics (CFD) modeling has been used to investigate the particle-fluid interaction. According to the model, once the particle is detached from the surface, the vortices and circulation zones trap the particle inside the trench and result in a long particle removal

Removal of Sub-Micron and Nano Particles Using Brush Cleaning Process

• Study the removal of submicron and nano particles using brush contact cleaning,
• study the various parameters influencing the removal of sub-micron and nano particles such as pressure, rotational speed and cleaning time,
• optimize SSEC’s Brush Scrubbing equipment for implanted wafers,
• challenge the system using aged Silicon Nitride particles.

The Effect of the Chemistry of the Adhesion for of Ceria Slurry in Post-CMP Cleaning of STI

Determine the reduction in the particle adhesion force due to cleaning chemistry. Specifically, the adhesion force will be measures in DI water and different EKC chemistry to develop a better understanding of the effect of chemistry on particle adhesion. This will also provide a tool to compare different chemistries for many slurries and particles.

Metrology and Removal of Submicron Particles from Structured Substrates

The objective of this research is to use investigate the removal of particles from structured surfaces such as Head Gimbal Assembly (HGA) as well as sliders in the trays. Fluorescent particles are used to evaluate the cleaning process. Cleaning of trenches from 6” AlTiC wafer is investigated. The theoretical removal efficiency of the particles from the HGA is also evaluated calculated.

Global Metrology of the Removal Efficiency of Submicron Particles from Structured Substrates

The objective of this research is to investigate the removal of fluorescent particles from structured surfaces such as trenches using global metrology (using a fluorometer). The main advantage of using a fluorometer is that global particle cleaning efficiency can be obtained in a short time. Cleaning of trenches from 6” AlTiC wafer is also investigated.

Experimental and Modeling Study of Removal of Submicron Particles from Structured Substrates

The objective of this research is to investigate the removal of particles from structured surfaces such as Head Gimbal Assembly (HGA) as well as sliders in the trays. Fluorescent particles are used to evaluate the cleaning process. The removal of submicron particles from trenches in 6” AlTiC wafer is investigated. The theoretical removal efficiency of the particles from the HGA is also calculated. In addition, physical computer modeling is used to:

• Design a slider tray with the most fluid flowing across the slider.
• Modify the slider tray geometry to achieve more than 80 % particle removal from the slider.
• Compare the removal for the oscillating versus steady flow.
• Determine the removal moment for 0.3 and 0.8 micro meter alumina particles.

Development of a MEMs Based Micro Gas Analysis System

The goal of this project is to develop a novel micro gas analysis system (MGA) consisting of a microplasma source for gas excitation, a microspectrometer to measure the atomic and molecular emission intensity, and an optical system coupling the light source and detector. The MGA will provide a compact, low-cost method for detecting gas impurities such as H2O, O2, H2, CO2, CH4, etc. to be monitored during gas delivery to many processes in semiconductor manufacturing. Develop effluent gas sensors for detection of reactor products (foreline, scrubber, exhaust). Optimize microgas analyzer, 200→1 ppb. Evaluate sensitivity to H2O, fluorocarbons.

Techniques for Finding and Characterizing Defects and Contaminants

Develop new techniques for locating and characterizing surface and buried defects and contaminants. Apply recently developed scanning probe microscopy (SPM) techniques toward this goal and to develop these and other techniques into useful imaging and spectroscopic tools. The effect of contamination on nanoscale electrical transport, dielectric properties, and electronic noise will be studied. Develop SPM techniques into useful tool for locating and characterizing surface and buried defects. Initially we will study insulating layers with well-characterized buried defects (insulating, metallic, voids). Frequency-dependent susceptibility will be used to locate leakage across insulating layers. Wafers and devices with known and unknown contaminants will be studied. Noisy traps will be located and correlated with device noise. Structural relaxation in particles during adhesion will be studied.

Physical Cleaning of Submicron Trenches, a Modeling Study

• Develop an effective cleaning technique for micro and nano scale trenches and vias with high aspect ratios.
• Use physical modeling to study the mechanism contaminant removal process in submicron deep trenches.
• Identify and control the key cleaning parameters for effective cleaning and high rinsing efficiency.
• Study the macro and micro features of the cleaning fluid interaction with a patterned wafer to identify the effect of cleaning fluid direction.

The Mechanics of CMP and Post-CMP Cleaning

The goal of our activities is to conduct a detailed analysis of the mechanics of particle, wafer and pad (or brush) interaction in CMP and post-CMP cleaning processes. We propose to study the real contact pressure at the interface between the pad and wafer, pad and particle or particle and wafer as a function of pad or wafer asperity distribution, deformation and height. The contact pressure variation can also be measured experimentally as a function of engagement height. Consequently, the relation between the real contact pressure and the apparent contact pressure, can be established. The apparent contact pressure over the contact area results from the macro scale force equilibrium of the two contacting bodies. This analysis and model will have the capability to bridge the fluid and solid mechanics at the macro level with the forces required for the interaction of particles with the wafer and pad at the micro level.

Particle Adhesion and Removal for Post-CMP Applications

• Determine the adhesion force for different particles on different substrates in different solutions experimentally.
• Understand and determine the onset of large adhesion force after polishing such as the development of covalent bonds.
• Study the removal and adhesion forces for alumina and silica slurry particles from silicon wafers (with different films, TOX, W, Cu, TaN, BPSG, etc.).
• Develop better cleaning guidelines and techniques to reduce surface defects after polishing.
• Determine the effect of polishing pressure on the slurry particle adhesion force.

The study of the removal and adhesion forces for alumina and silica slurry particles from silicon wafers will be conducted using indirect adhesion measurement technique 1-3. Conditions that give rise to large adhesion forces will be studied and determined to develop a better understanding of particle adhesion in post-CMP applications.

Nano and Microscale Particle Removal

• Develop an effective nanoscale particle removal technique using acoustic streaming.
• Provide a fundamental understanding of the removal mechanism that will be experimentally verified.
• Experimentally measure particle removal of particles in the size range of 10-100 nm from semiconductor wafers.
• Evaluate effect of streaming flow frequency, velocity amplitude and particle size and particle/substrate composition on the removal efficiency experimentally and numerically.

A direct outcome of this research will be a rigorous relation of nanoparticle removal to the flow frequency, velocity and pressure amplitude (intensity). Understanding the fundamental mechanisms underlying nanoscale particle removal will determine the effectiveness and limitations of the proposed approach. Another one of our goals is to create an easy to use a physical model that will indicate the frequency and intensity required for different particles and substrates at the end of this research.