Spin-on Glass and Particle Incorporation

Thomas R. Stratton

University of Chicago

Advising Professor: Eric P. Kvam

Introduction

Capacitors are vital to the operation of microelectronics today. A thin-film capacitor-transistor comprises the primary unit of many modern DRAM modules. One limit to the speed of such devices is the RC (Resistance times Capacitance) delay, the time required to charge the capacitor up to a desired voltage. There are two ways to tackle this problem: either to reduce the resistance or the capacitance of the materials involved. A number of compounds are currently being analyzed to determine their possible value as future dielectrics. One of these compounds is (poly)Methylsilsequioxane, which was the primary dielectric studied in this project. MSSQ, as Methylsilsequioxane is frequently truncated to, is a silicone-based polymer. Instead of the usual four oxygen atoms bonded to each silicon atom, three oxygen atoms and one methyl-type (CH2 or CH3) are bonded to each silicon atom. MSSQ is very resistant to cracking and has a low dielectric constant (between 1.8-3.0 depending on the processing method), but due to the prevalence of organic methyl- groups it has a tendency to break down at higher temperatures.

Spin processing or spin-on processing is a cheap and effective way of coating surfaces with an evenly distributed layer. In this project we used a research spinner to spin the layers of MSSQ on the glass slides, after sputtering the slides with a platinum layer. A second layer of platinum applied after the spinning gave us the electrodes required to test the dielectric properties of our MSSQ layers. The final goal of the project was to incorporate ceramic particles into the MSSQ layer and study any changes in dielectric properties.

Program Objectives

  • Spin an even, relatively error-free, flat, and dielectrically consistent layer of MSSQ onto a glass slide
  • Test the dielectric properties of our consistent MSSQ layer
  • Incorporate ceramic particles in the MSSQ, achieve a homogenous distribution, and test the dielectric properties of this new layer, looking for differences from the pure MSSQ.

Experimental Approach

  • Plasma sputtered a layer of platinum onto a glass slide
  • Spun a layer of MSSQ (and later, MSSQ with ceramic additive) onto the glass slide
  • Used profilometer to measure the thickness of film and size of edge effects
  • Plasma sputtered a second layer of platinum onto glass slide
  • Tested Capacitance of MSSQ layer on microelectronics test bench

Research Findings

  • Lowered the number of errors by increasing cleanliness and decreasing spinning time
  • Created a flatter layer of MSSQ by increasing tempering time and decreasing errors
  • Achieved consistent spinning of 0.8 micron MSSQ layer with a k-value of approximately 1.88


Optical Microscopy of MSSQ layer with errors.


Optical Microscopy of later MSSQ layer after error-prevention techniques were mastered and applied.

Final Research Presentation