Home Tech Library Best tool-SIMS for calculating P/N dopant concentration

Best tool-SIMS for calculating P/N dopant concentration

Home Tech Library Best tool-SIMS for calculating P/N dopant concentration

Best tool-SIMS for calculating P/N dopant concentration

by ruby

Issued Date: 2017/12/26
Issued By: iST

Semiconductor process controls current and P / N electrical characteristics with ion implantation / diffusion process,How to accurately calculate the doping concentration and depth?
LED epitaxy may end up with a P/N type due to the doping of impurity atoms, so how to identify the dosage?

P- and N-types of LED / semiconductors are regulated by a concentration of impurities doped. Amid approaching the limit of Moore’s Law, increasingly shrinking to the next nano grade, and ever changing wafer / LED process, the first step is to control the semiconductor process parameter and maintain component / epitaxial stability. Otherwise current/voltage characteristics may be hampered and IC/LED performance deteriorated.

The iST Tech Classroom of this month is aimed to share the secrecy of the indispensable P/N doping concentration profile identify tool – the secondary ion mass spectrum analysis technique – with each wafer/LED process engineer.

SIMS in a glance

Samples are analyzed with mass spectrum over secondary ions sputtered by sputtering / etching over the samples with primary ions. This mechanism executes quantitative analysis over micro contamination, doping, and ion implantation as well as junction diffusion behavior study with high resolution detection capacity based on the high sensitivity of ions.

There are some common questions about SIMS as below.

  • Is it applicable with any element?

    SIMS may analyze any element in the periodic table. Most semiconductor process requires analyzing P-type boron ions (B), N-type phosphorus (P) or arsenic (As) ions while the LED P-type magnesium (Mg) and N-type silicon (Si) ones.

    The lowest detection limit of most elements may go down to ppma (1E-6) while some of them may go down another three order of magnitude to ppba (1E-9). This makes it ideal for trace detection and analysis over semiconductor and thin film material detection and analysis.

  • What messages are SIMS analysis providing?

    In addition to doping concentration analysis the high mass resolving capacity of iST SIMS may be employed in P/N junction depth analysis and conc P/N junction depth analysis entration analysis over trace elements in bulk material.

  • Is there any limits to analysis samples?

    SIMS is aimed at destructive analysis for samples of LED, panel, solar, PCB and basic Si wafer process. To get the optimum results and better resolution it’s better to have samples of size at 10mm, flat surface, and analysis depth from tens of nanometers (nm) to micrometers (um).

Let’s review some actual element analysis chart

  • Case 1: detection limit ppba level analysis

    • Analysis sample: semiconductor silicon wafer
    • See the chart below for the highest limit of iST SIMS device in terms of implanting concentration of arsenic (As) ions in semiconductor silicon wafer is analyzed. It tells the detection limit of SIMS may reach up to 0.2 ppba.

    Depth profiling of As ions (N type) implanted in Si chips

  • Case 2: high resolving SIMS analysis

    • Analysis sample: semiconductor silicon wafer
    • Find out SIMS depth resolution with multi-layers of nano-thick boron (B) implant analysis. The minimum depth resolution of depth profile analysis is 1.65nm by iST SIMS based on this special high-resolution analysis technology.

    Depth profiling of B ions (P type) implanted in Si chips

  • Case 3: LED epitaxial concentration analysis

    • Analysis sample: LED epitaxial
    • LEDs samples usually need to observe 7 or 8 trace elements during SIMS analysis. Figures below tell concentration profile of Mg (P type) and Si (N type) in epitaxial; combining with the TEM analysis and relative position of elements in epitaxial can be identified.

    Upper figure: identify concentration profile through SIMS analysis
    Lower figure: identify relative position of elements through TEM analysis

This article is aimed to share our detection and verification experiences with honorable clients like you. Should there be any sample abnormalities requiring determination or inspection or you need to know more about the aforementioned techniques, just contact Mr. Johnson Chang at +886-3-579-9909 Ext. 6613 or email him at sa_tw@istgroup.com

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