Spin-on Glass and Particle Incorporation

Thomas Stratton

Purdue MSREU 2002

Advisor: Dr. Kvam

Introduction

Microcapacitors are vital to the operation of today’s computers, radios and other microelectronics

In this project we hope to study the effects of ceramic particle incorporation within a low-k material

MSSQ

Methylsilsequioxane (MSSQ) is a silicon-based organic polymer

Has strong resistance to cracking Low dielectric constant

Manufacturer quote 2.6 @ 1MHz Experimental result 1.85 @ 10kHz

Good planarizing qualities Forms a flat, even, consistent layer

Manufacturer 4000 Angstroms Experimental 8000 Angstroms

MSSQ General Structure

Objectives

Spin an even, flat, defect-free layer of MSSQTest the dielectric properties of capacitors

formed by MSSQ between two platinum electrodes

Suspend ceramic particles with the MSSQSpin the suspension on slidesTest the dielectric properties of the MSSQ-

ceramic suspension

Procedure

Sputter a layer of platinum on glass laboratory slides

Ready the MSSQ (or suspension)Spin on layer of MSSQ (or suspension)Bake on hot plate (varying temperatures)Cure in oven at 425 degrees CSputter a top contact pointTest properties

Reducing Defects

Due to non-ideal conditions, many surface defects appeared during initial spinning

Original attempts to reduce spin defects were focused on improving cleanliness and reducing processing impurities

After improving cleanliness failed to reduce defects, reducing the total spinning time to below manufacturer’s suggestion was conceived and implemented with immediate results

Pictures of MSSQ slides

Table of Results

Slide 1 Slide 2 Slide 3 Slide 4 Slide 5 Slide 6 Slide 7

Initial 3100 rpm 7s 9s 9s 9s 6s 7s 7s

1500 rpm 10s 8s 11s 11s 4s 8s 0s

“Dry” 3100 rpm 0s 9s 9s 9s 8s 0s 0s

MSQ drops used 6 12 15 16 7 9 8

Cleanliness

(comparative)

Fair Fair Good Very

Good

Very

Good

Very

Good

Very

Good

Errors per cm2 33.5 50.2 141.0 78.8 145.0 30.47 20

Chart of Results

0

50

100

150

1 2 3 4 5 6 7

Major ErrorsTotal Errors

Barium Titanate Powder

High Dielectric Constant (k=233)Readily available due to other students in

the lab using BaTiO3 in REU projects

Particles ranged between 70 nm and 1900 nm, high purity

Suspending

Suspended 2.9496 grams of Barium Titanate powder in 1.55 grams of MSSQ

Made white liquid that hardened very quickly and tended to clump after dispersal

Suspension was then applied to glass slides

Difficulties with the Suspension

Suspension did not spread evenly, surface was “boulder-strewn terrain”

Suspension tended to harden very quicklyContact pads did not sputter on the cured

suspension very wellCapacitor leakage and error was a

significant problem

Boulder-strewn terrain

Results

Found minimum k-values of 4.51 and 4.01 (both at 10kHz)

These minimum values are greater than the MSSQ’s k-value at 10 kHz of 1.85, which shows that the Barium Titanate powder must be having some effect

Future Work

Changing the percentages of BaTiO3 and MSSQ in the suspension

Studying effects of other ceramic suspensionsStudying how particle size, orientation, and

composition affect dielectric propertiesFinding a suitable dispersant to achieve a more

balanced distribution of ceramic