Monthly Archives: April 2015

How Standard Clean Particle Removal (SC1 Clean) is Supported in a Wet Bench Process

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How Standard Clean Particle Removal (SC1 Clean) is Supported in a Wet Bench ProcessSC1 Clean is the first step in the RCA clean, the procedure required before the high-temperature processing of silicon wafers. Organic impurities attached to silicon, oxide and quartz surfaces by the solvating and oxidizing actions of NH4OH and H2O2 respectively are eliminated by the particle removing solution, SC1 Clean. This solution starts a slow regeneration process whereby the silicon wafer’s original surface layer of oxide is broken down and replaced with a new layer. This regeneration process is a highly significant part of particle removal.

SC1 solution is used at 75 or 80°C for approximately 10 minutes. It is composed of:

  • 5 parts deionized water
  • 1 part NH4OH
  • 1 part H2O2

The cleaning procedure begins by heating a mixture of the deionized water and NH4OH up to 75°C. Then, add H2O2 and allow the mixture to bubble violently before using. The silicon wafer will then be soaked in the solution for 15 minutes. After, rinse the silicon wafer in a container of deionized water in order to clean off the solution. You should change the water several times in order to prevent any removed residue from clinging back on to the surface of the silicon wafer. Remember, with the new oxide layer on the surface comes ionic contamination that should be cleaned off in the following steps of the RCA clean.

Modutek Megasonic Cleaning Equipment and Features

The particular demands of the semiconductor, FPD, hard disk, solar and crystal industries are met by Modutek’s precision megasonic cleaning system. In addition, partnering with Kaijo Corporation allows Modutek to supply engineers with cutting-edge high precision cleaning technology.

You can clear 0.1 µm particles while working up to 140°C with Modutek’s Indirect (MSI Series) bath design. Or, Modutek’s Direct (MSD Series) can give you identical results with the Teflon coated Megasonic transducer. Placed in the tank, the transducer plate is ideal for using SC1 Clean and is easily accessible for installation and upgrades. With the help of Modutek’s engineers, your manufacturing equipment will be designed to work according to the requirements of your application.

Modutek’s Megasonic cleaning features include:

  • Automatic frequency tracking system
  • High efficiency generator
  • Upper and lower limit controls
  • Available frequencies: 950kHz, 2MHz, 750kHz, 430kHz and 200kHz

Modutek’s Experience

Modutek has been in the business of supplying semiconductor manufacturing equipment for 30+ years. This history is sustained by associates who will work with you from design to final installation. For a free quote call 866-803-1533.

How the Silicon Nitride Etch Process Is Supported By Modutek

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The silicon nitride etch process is used in the manufacture of integrated circuits to selectively remove silicon nitride with respect to silicon oxide. Engineers and process specialists in the industry who work with semiconductor equipment manufacturers owe a great deal of their expertise to the quality of the etching equipment at their disposal today.

Background

Integrated circuit fabrication processes include selectively removing silicon nitride using wet or dry etching. Selectivity between materials removed and not removed should be high. However, selectivity is not the only consideration, in a manufacturing environment a process engineer needs consistent and repeatable results from high quality and reliable equipment.

Field Oxides Provide Mask Layer

Field oxides deposit a dielectric mask layer over silicon using a patterning mask layer exposing the silicon or oxide, and growing the thick oxide called field oxide. The preferred choice of dielectric for the mask layer is silicon nitride. This process is LOCOS, Localized Oxidation of Silicon. A poly silicon layer is frequently present beneath the nitride. This is a Poly Buffered LOCOS stack. Thus, both silicon nitride and poly silicon must be removed without affecting the silicon oxide.

Aging Effects and High Particle Count

Wet etching techniques are used for stripping nitride and silicon when oxides are present. Silicon nitride is etched in phosphoric acid that is boiling. Amounts of nitric acid may be in the bath. These baths are susceptible to aging and having higher particle counts because the silicate concentration in the bath increases. Others use separate baths for nitride and poly silicon. This increases the number of baths required and can lead to pitting of the pad oxide, which engineers overcome by using a bath with phosphoric, hydrofluoric, and nitric acids. Bath life is extended by hydrofluoric and nitric acids. Nitric acid is required to oxidize silicon. The initial etching selectivity of nitride to oxide may be undesirably low, selectivities of 9:1 observed, and depends on fluorine concentration. Higher initial etch selectivities are preferred.
Before etching silicon nitride or poly silicon to silicon oxide, you should add silicon to the etch process bath. The silicon enhances initial etch selectivity. Fluorosilicates also can be used. These compounds dissolve readily in phosphoric acid without particles. The compounds increase the etch selectivities to 40:1 and 33:1 for silicon nitride and poly silicon. The additional silicon stabilizes may be in the bath from initial use until its use is terminated. Variations of this procedure are tested and reviewed by engineers and researchers.

Equipment Innovations

IC equipment suppliers provide manufacturers and researchers with leading edge products required for producing smaller geometry semiconductors, thin-film heads, and MEMS, and also need to offer service, support, and retrofitted systems. These products are usually designed to meet specific requirements of manufacturers.

Silicon Nitride Etch Baths that Provide Safety, Control and Flexibility

The Nb Series Operation Process used with Modutek’s silicon nitride etch bath guarantees process control, safety and flexibility with a two-level diagnostic system monitoring temperature while maintaining acid to water ratio through D.I. water supplementation. By using a new remote metering system, the Nb Series is easy to install and service in new or existing stations. Process engineers know that this kind of equipment needs to be manufactured and supported by a company that:

  • Has extensive experience and expertise;
  • Uses the latest technology;
  • Meets specific customer requirements;
  • Provides high quality and reliable equipment;
  • Offers excellent technical support and onsite repairs

Modutek has over 30years of experience providing high quality and reliable equipment to support the silicon nitride etch process and is a leader among semiconductor equipment manufacturers. If you need to discuss your process requirements or would like a free quote, call Modutek at 866-803-1533 or visit www.modutek.com.