Mike Kottke

Characteristics of spin-on ferroelectric SrBi 2 Ta 2 O 9 thin film capacitors for ferroelectric random access memory applications

We report on the properties and characterization of SrBi 2 Ta 2 O 9 (SBT, or Y − 1) thin film capacitors for ferroelectric random access memory (FERAM) applications. The films were prepared by spin-coating from carboxylate precursors. The remanent polarization ( P r ) was 5−6 μ C/cm 2 and the coercive field was ∼55 kV/cm. Excellent fatigue endurance was observed up to 10 11 cycles. Auger analysis indicates bismuth diffusion through the Pt electrode after capacitor anneal which might require excess Bi in the precursor solution for stoichiometry control. No detectable amount of α emission was found from SBT films, which reduces the possibility of soft error when used in the memory devices.

Solderability degradation models for fusible tin alloy coatings on copper substrates

Ion milling is used to investigate the role of surface corrosion products in degrading solderability of tin and tin alloy coatings over oxygen-free high-conductivity copper substrates. The coatings were applied by electroplating from a low organic stannous sulfate bath and by dipping into molten 300 degrees C Sn and Sn-40Pb alloy. Ageing took place in an 85% relative humidity, 85 degrees C environment for 100 days, and in a 190 degrees C environment with less than 6 mm (Hg) of water vapor for 10 hours. Solderability was measured by edge dipping the samples into molten 260 degrees C Sn-40Pb alloy. The effectiveness of ion-mill cleaning in removing the surface corrosion products was determined using Auger depth profiles. A small reduction in solderability due to surface corrosion is seen regardless of the coating type or ageing condition. The majority of the solderability degradation is due to the modification of the metal system below the surface corrosion layers, and surface corrosion plays only a small role. >

Stoichiometric Effects of Sputtered Barium Strontium Titanate Films

Barium Strontium Titanate films have been deposited by rf magnetron sputtering and have been studied with respect to Ba/Sr ratio. Physical and electrical characterization has been done as a function of temperature, thickness, and composition, and results show that dielectric constant increases with increasing temperature, thickness (up to ∼80 nm), and Ba/Sr ratio for the compositions studied. The lattice parameters for the sputtered films are larger than those expected for powder samples and also increase with increasing Ba/Sr ratio.

An analysis of high temperature (1150 °C) furnace annealing of buried oxide wafers formed by ion implantation

Silicon-on-insulator films were formed by ion implantation of oxygen and were treated with various annealing cycles at peak temperatures of 1150 °C, 1200 °C, and 1250 °C in a conventional diffusion furnace. The objective of this study was to examine the structural effects on samples with similar oxygen diffusion lengths (from 17 to 33 μm) achieved by annealing at different times and temperatures. The oxygen and silicon distributions, as well as the residual damage and precipitate size and distribution, were measured by Auger electron microscopy, Rutherford backscattering spectroscopy, and transmission electron microscopy. In agreement with previous findings, higher temperatures produced a larger and less defective, “precipitate-free” superficial Si region. The buried oxide layer thickened from 0.33 μm to a maximum of 0.43 μm as some precipitates were incorporated into the buried oxide while others adjacent to the buried oxide grew in size (up to 47 nm) and decreased in relative number. A new result of this systematic study of annealing conditions was that the peak temperature has a greater effect on the morphology and crystal quality of the superficial Si structure than does time at temperature. Structural changes for longer anneals at 1150 °C are not equivalent to shorter anneals at 1250 °C even though the diffusion length of oxygen for these treatments is the same.

High depth resolution Secondary Ion Mass Spectrometry (SIMS) analysis of Si1−xGex:C HBT structures

Low energy Secondary Ion Mass Spectrometry (SIMS) was employed to study graded-base Si1−xGex:C heterostructure bipolar transistors (HBTs) structural properties. Using an O2+ beam at 500 eV with normal incident angle, Ge profiles can be quantified by minimizing the influence of matrix effect. This is achieved with a correction based on the linearity of the ratio (IGe/ISi) with respect to the ratio (x/1−x). The SIMS results showed an excellent correlation with the graded Auger Ge profile in 5–20% range. Moreover, SIMS analysis revealed an enhanced Ge diffusion with the carbon incorporation, which was used to suppress base boron diffusion during the rapid thermal annealing (RTA) process. Based on the SIMS Ge profile, device simulation can be used to design Ge profile shape in order to optimize process throughput without impact on the device performance. The high depth resolution SIMS data is essential for Si1−xGex:C HBTs structural characterization and process optimization.

Physical and chemical characterization of barium strontium titanate thin films

Thin films of barium strontium titanate (BST) are under consideration as a replacement for silicon dioxide as the dielectric in advanced memory devices. The major attraction of BST is its very high dielectric constant compared to SiO2. Integral to the development and implementation of a new materials system such as BST is physical and chemical characterization. To achieve optimal electrical performance with a robust process requires an in-depth understanding of the relationships between materials/process variables, physical/chemical properties and the electrical behavior of the BST films. This paper covers specifics of many of these inter-relationships.

Characterization techniques for high-mobility strained Si CMOS

This paper discusses critical characterization techniques for strained Si technology, especially to determine the strain state, thickness, and Ge content in the underlying Si/sub 1-x/Ge/sub x/ alloy pseudosubstrate.

Root‐Cause Analysis and Statistical Process Control of Epilayers for SiGe:C Hetero‐Structure Bipolar Transistors

The SiGe:C hetero‐structure bipolar transistor (HBT) has turned into a key technology for wireless communication. This paper describes various critical analytical techniques to bring up and maintain the SiGe:C epi‐process. Two types of analysis are critical, (1) routine monitoring SiGe base and Si cap thickness, doping dose, Ge composition profile, and their uniformity across the wafer; and (2) root‐cause analysis on problems due to non‐optimized process and variation in process conditions. A transmission electron microscopy (TEM) technique has been developed allowing a thickness measurement with a reproducibility better than 3 A. Charge‐compensated low‐energy secondary ion mass spectrometry (SIMS) using optical conductivity enhancement (OCE) allows a Ge composition measurement to a required precision of 0.5 at. %.