Source: China Semiconductor Forum
One of the reasons why wafer manufacturing plants are extremely expensive is the need for a cleanroom. Why is a cleanroom necessary?
Answer: Because tiny particles can cause defects in electronic components and circuits.
What is a semiconductor?
Answer: The electrical properties of semiconductor materials lie between good conductors like metals (copper, aluminum, tungsten, etc.) and insulators like rubber, plastic, and dry wood. The most commonly used semiconductor materials are silicon and germanium. One of the most important properties of semiconductors is the ability to deliberately add certain impurities through a process called doping and to control their conductivity using an electric field.
What are the commonly used semiconductor materials?
Answer: Silicon (Si), Germanium (Ge), and Gallium Arsenide (GaAs).
What is VLSI?
Answer: VLSI (Very Large Scale Integration) refers to ultra-large scale integrated circuits.
In the semiconductor industry, what is commonly referred to as insulating layer material?
Answer: Dielectric.
What is the main function of the thin film area equipment?
Answer: To deposit dielectric layers and metal layers.
What is CVD (Chemical Vapor Deposition)? What are the types of CVD?
Answer: CVD is a process that utilizes gaseous chemical source materials to create chemical deposits on the wafer surface. It is mainly divided into PE-CVD (Plasma Enhanced CVD) and Thermal-CVD (Thermal CVD).
Why use aluminum-copper (AlCu) alloy for wires?
Answer: It is a good conductor, second only to copper.
What is the function of dielectric materials?
Answer: To act as isolation between metal layers.
What is PMD (Pre-Metal Dielectric)?
Answer: It is the dielectric layer before metal deposition, which lies between polysilicon and the first metal layer dielectric.
What is IMD?
Answer: The dielectric layer between metal layers.
What is USG?
Answer: Undoped Silicate Glass.
What is FSG?
Answer: Fluorinated Silicate Glass.
What is BPSG?
Answer: Borophosphosilicate Glass.
What is TEOS?
Answer: Tetraethoxysilane is used for depositing silicon dioxide.
What form does TEOS exist in at room temperature?
Answer: Liquid.
What does the K value of 3.9 for silicon dioxide indicate?
Answer: It indicates that the dielectric constant of silicon dioxide is 3.9 times that of vacuum.
What is the application of fluorine in the CVD process?
Answer: As a cleaning chemical gas for the reaction chamber.
Briefly describe the principle of operation of an Endpoint detector.
Answer: During the clean process, the change in the concentration of products or reactants is detected by the detector when the intensity of light at a specific wavelength increases or decreases. When it exceeds a certain set intensity, the process is defined as complete, and that point is the endpoint.
What materials are the tubing used in the equipment mainly made of?
Answer: Stainless steel, brass, PVC (plastic), and Teflon.
Why should a maintenance notice be placed on the equipment during repairs?
Answer: To inform everyone not to operate the machine to avoid danger.
Why is it required to have at least two people cooperate during machine maintenance?
Answer: To assist in removing heavy objects and to be on guard for possible accidents.
After replacing any parts on the gas pipeline, what action must be taken?
Answer: Use a helium leak detector to check for leaks.
What kind of gloves should be worn when handling a reaction chamber that has not yet cooled to room temperature?
Answer: Asbestos thermal gloves, which should only be used below 80 degrees Celsius.
What is vacuum? What is the common unit of vacuum used in the semiconductor industry?
Answer: The semiconductor industry commonly uses Torr as the unit of vacuum pressure. One atmosphere is equivalent to 760 Torr, and environments with pressures below 760 Torr are referred to as vacuum.
What is the function of a vacuum pump?
Answer: To reduce the gas density and pressure inside the reaction chamber.
What is interlock?
Answer: Interlocks on machines serve to protect the safety of operators and to provide specifications for water, electricity, and gas signals to protect the machine.
What is the purpose of setting many interlocks on machines?
Answer: To mainly prevent operational errors by personnel and to prevent unrelated personnel from operating the machine.
What is the function of a Wafer Scrubber?
Answer: To remove contaminant particles from the chip surface.
ETCH
What is etching?
Answer: It is the process of removing all or specific areas of the thin film formed on the wafer surface to the required thickness.
Types of etching:
Answer: (1) Dry etching (2) Wet etching
Etching objects can be divided by thin film types:
Answer: poly, oxide, metal.
What are the common metal wire materials in semiconductors?
Answer: Tungsten (W)/ Aluminum (Al)/ Copper (Cu).
What is dielectric etching?
Answer: Oxide etch and nitride etch.
What are the common dielectric materials in semiconductors?
Answer: Silicon dioxide / Silicon nitride.
What is wet etching?
Answer: It uses liquid acids or solvents to remove unwanted thin films.
What is plasma?
Answer: Plasma is the fourth state of matter. It consists of a combination of charged and neutral particles, including electrons, positive ions, negative ions, neutral molecules, reactive species, and emitted photons. Plasma can be generated using high temperatures or high voltages.
What is dry etching?
Answer: It uses plasma to remove unwanted thin films.
What is under-etching?
Answer: It refers to when the material being etched stops during the etching process, causing the thin film that should be removed to remain.
What is over-etching?
Answer: It refers to excessive etching that damages the underlying layer.
What is etch rate?
Answer: The thickness or depth of etching material that can be removed in a unit of time.
What is seasoning?
Answer: It is a process that uses dummy wafers to perform several etching cycles to stabilize the process conditions after cleaning the etching chamber or replacing parts.
What is the main use of Asher?
Answer: To remove photoresist.
What is the function of a wet bench dryer?
Answer: To remove moisture from the wafer surface.
List the current wet bench drying methods:
Answer: (1) Spin Dryer (2) Marangoni dry (3) IPA Vapor Dry.
What is a Spin Dryer?
Answer: It uses centrifugal force to remove moisture from the wafer surface.
What is a Marangoni Dryer?
Answer: It uses surface tension to remove moisture from the wafer surface.
What is an IPA Vapor Dryer?
Answer: It removes moisture from the wafer surface using the principle of IPA (isopropanol) and water miscibility.
What instrument is used to measure particles?
Answer: Tencor Surfscan.
What instrument is used to measure etch rate?
Answer: Film thickness gauge, measuring the difference in film thickness.
What is AEI?
Answer: After Etching Inspection.
What items must be checked during AEI visual inspection of wafers?
Answer: (1) Whether the front color is abnormal or scratched (2) Whether there are any missing corners or particles (3) Whether the etching number is correct.
How should a metal etching machine be processed when switching to a non-metal etching machine?
Answer: Clean the machine to prevent metal contamination issues.
What is the function of the Asher machine for metal etching?
Answer: To remove photoresist and prevent corrosion.
Why should general sulfuric acid baths not be used for cleaning after metal etching?
Answer: Because metal wires will dissolve in sulfuric acid.
What is the purpose of the machine?
Answer: Baking.
What is the baking temperature of the Hot Plate?
Answer: 90~120 degrees Celsius.
What gas is primarily used for Poly ETCH?
Answer: Cl2, HBr, HCl.
What are the main gases used for Al metal etching?
Answer: Cl2, BCl3.
What is the main gas used for W metal etching?
Answer: SF6.
What gas is primarily used for oxide via/contact ETCH?
Answer: C4F8, C5F8, C4F6.
The chemical composition of the sulfuric acid bath is:
Answer: H2SO4/H2O2.
The chemical composition of the AMP bath is:
Answer: NH4OH/H2O2/H2O.
What is UV curing used for?
Answer: To perform pre-treatment of photoresist using UV light to enhance the strength of the photoresist.
What layer is “UV curing” used for?
Answer: Metal layers.
What is EMO?
Answer: Emergency switch on the machine.
What is the function of EMO?
Answer: To be pressed in case of concerns about danger or when the machine is out of control.
What warning signs are posted on the wet etching door?
Answer: (1) Warning: There is a serious danger inside. Do not open this door (2) Mechanical arm danger. Do not open this door (3) Chemical hazard. Do not open this door.
What should be done in case of chemical solution leakage?
Answer: Do not test the leaked liquid with hands. Test with pH paper and locate the leaking pipeline.
What should be done if there is a fire in the IPA tank?
Answer: Immediately close the IPA supply pipeline and extinguish the fire with the machine’s fire extinguisher and notify the emergency response team.
What are the main components of the BOE tank?
Answer: HF (hydrofluoric acid) and NH4F (ammonium fluoride).
What do the three letters BOE stand for?
Answer: Buffered Oxide Etcher.
What is the function of the toxic gas valve cabinet (VMB)?
Answer: To use an exhaust device to remove toxic gas in case of leakage and to prevent toxic gas from escaping.
Why is the plasma frequency generally set at 13.56 MHz instead of other frequencies?
Answer: To avoid affecting communication quality, only specific frequencies are allowed for generating plasma, such as 380~420KHz, 13.56MHz, 2.54GHz, etc.
What is ESC (electrical static chuck)?
Answer: It uses the principle of electrostatic adsorption to fix the wafer on the substrate plate.
The main gas for Asher is
Answer: O2.
What is the most critical parameter for etching in the Asher machine?
Answer: Temperature.
To be continued…
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