Semiconductor Analysis - Surface Characterisation of Semiconductors Using Secondary Ion Mass Spectrometry (SIMS) by Ceram

Topics Covered

Introduction
Ultra- Shallow Junctions
     Delta- Doped Structures for Shallow SIMS Ddepth Profiling
     Ultra-Low Energy Ions for SIMS Depth Profiling
Gate Dielectrics in Semiconductors
     Characterisation of Ultra-Thin Oxynitride Gate Dielectrics
Characterisation of Silicon - Germanium in Semiconductors
     High Depth Resolution SIMS Analysis of Quantum Wells
     SiGe Tunnelling Diode
     Determination of Ge Fraction
Wafer Contamination in the Semiconductor Industry
     Measuring Metal Contamination with Total Reflection X-ray Fluorescence (TXRF)
     Vapor-Phase Decomposition-Total Reflection X-ray Fluorescence (VPD-TXRF)
     Vapor-Phase Decomposition-Inductively Coupled Plasma Mass Spectrometry (VPD-ICPMS)
III-V Multijunction Solar Cells
     SIMS Analysis of GaAsP/InGaAs Solar Cell
Optoelectronics

Tag Links : Surface analysis | Semiconductor analysis | SIMS Depth Profiling | TXRF | Secondary Ion Mass Spectrometry | Rutherford Back-Scattering (RBS)

Introduction

Ceram is a global expert in materials analysis, research and quality testing, providing customised solutions and consultancy that help clients to measurably improve performance and profitability through safer, regulatory-compliant and better-engineered products. Setting new standards in materials testing, Ceram works as an extension of customers' teams, applying its expertise and capabilities to a wide range of sectors

As device fabrication moves to ever smaller geometries the importance of surface analytical investigations becomes ever more critical to development programmes, process improvement and failure resolution. Ceram has developed a range of investigative techniques which enable customers in the semiconductor and related industries to achieve high quality products and processes and to minimise downtimes by providing rapid response failure studies. The application areas in semiconductor technology addressed by Ceram are described briefly here.

Ultra- Shallow Junctions

Delta- Doped Structures for Shallow SIMS Ddepth Profiling

The development of analytical protocols for shallow SIMS depth profiling with high depth resolution requires the use of delta-doped structures to provide objective measurement of the effects of ion beam mixing and ion-induced topography as a function of depth. The SIMS profile of a boron delta-doped layer structure using 500eV O₂⁺ ions shows the near-surface layers ( 5nm separation) resolved with peak-valley resolution of >one decade. The high depth resolution is maintained throughout the profile.

Ultra-Low Energy Ions for SIMS Depth Profiling

Low energy B implants in Si are fundamental to the increased performance of the emerging generation of devices. Accurate determination of junction depth and retained dose requires the use of ultra-low energy ions for SIMS depth profiling. The example shows the characterization of an anneal sequence on a 1keV boron implant in silicon using 500eV O₂⁺ ions.

Gate Dielectrics in Semiconductors

Characterisation of Ultra-Thin Oxynitride Gate Dielectrics

Characterisation of the new generation of ultra-thin oxynitride gate dielectrics typically requires determination of the nitrogen distribution within a ~2nm thick insulating layer. The profile shows a SIMS depth profiling through the oxynitride layer with quantification of Si, O and N, using a 250eV Cs⁺ primary ion beam at oblique incidence.

Characterisation of Silicon - Germanium in Semiconductors

High Depth Resolution SIMS Analysis of Quantum Wells

Strained Si-Ge permits precise engineering of the semiconductor band gap, offering a route to high–speed devices which are compatible with existing silicon-based fabrication technology. High depth resolution SIMS analysis of a SiGe test structure grown by gas source MBE. The device exhibited excellent optical properties, consistent with high quality Si / SiGe interfaces.

SiGe Tunnelling Diode

SIMS characterization of an Esaki tunnelling diode by low energy SIMS reveals the diffusion of phosphorus through the SiGe layer during annealing (680oC for 60 seconds). This directly reduces the n-type doping and also causes compensation of the carriers in the boron-doped layer.

Determination of Ge Fraction

Rutherford Back-Scattering (RBS) provides an excellent complementary technique to SIMS where absolute quantification of major elements or high concentration dopants is required. In this example the germanium fractional composition is determined for three as-grown devices.

Wafer Contamination in the Semiconductor Industry

Measuring Metal Contamination with Total Reflection X-ray Fluorescence (TXRF)

The measurement of metal contamination on wafers by direct Total Reflection X-ray Fluorescence (TXRF) normally uses five discrete points (of limited area) and is confined to transition and heavy metals. It is not suitable for the detection of light elements.

Vapor-Phase Decomposition - Total Reflection X-ray Fluorescence (VPD-TXRF)

Vapor-Phase Decomposition - Total Reflection X-ray Fluorescence (VPD-TXRF) improves these detection limits by a factor of 300 on 200mm wafers and allows detection of the light elements including Na and Al by use of Cr X-ray excitation. The wafer is exposed to HF in a VPD reactor so dissolving the native oxide. This is collected by scanning with a DI water droplet which is permitted to dry and the residue analysed by TXRF. The information provided is from the entire wafer surface resulting in significantly improved detection limits.

Vapor-Phase Decomposition - Inductively Coupled Plasma Mass Spectrometry (VPD-ICPMS)

Even lower detection limits (including the light elements) can be achieved by use of this technique. Instead of drying the droplet in-situ it is removed after scanning and diluted prior to analysis by ICPMS.

III-V Multijunction Solar Cells

SIMS Analysis of GaAsP/InGaAs Solar Cell

SIMS analysis of a strain balanced high efficiency GaAsP/InGaAs quantum well solar cell using 1keV Cs⁺ primary ions. The structure contains 20 InGaAs layers of 8nm width each separated by 45nm of phosphorous doped GaAs.

Optoelectronics

Quantitative chemical analysis of a red laser structure using combined SNMS (for matrix) and SIMS (for dilute impurity) shows the oxygen concentration associated with doping of the n and p regions.

Source: Ceram

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