Deposition Essentials

• Deposition is when a thin layer of material is added to the surface of a chip
• Each deposition process varies depending on the material and the purpose it serves on a chip

Microchips are fabricated by repeating thousands of steps. During the fabrication process, very thin layers of materials are deposited onto a silicon wafer, then etched [Etch Essentials] to create a path through which electricity travels. As the deposition and etch processes are repeated, a complex series of these paths are created to control the flow of electricity that allows a chip to perform its function. Lam has been in the deposition market for nearly 45 years and remains one of the top suppliers in the world for deposition tools.

• Deposition refers to the manufacturing process by which a thin layer of material is added to a chip.

Deposition processes are primarily used for two purposes:

• Metal deposition: A layer of conductive material is deposited on a wafer to create a path through which electricity can travel freely.
  
• Dielectric deposition: A layer of non-conductive material is deposited on a wafer to ensure electricity is blocked from traveling where it should not flow.

Think of metal deposition as the process of laying roads where cars are allowed to travel, and dielectric deposition as the process of setting up guidelines and barriers to control the flow of traffic.

Common Methods

Some of the more common methods of deposition in semiconductor manufacturing include:

Chemical vapor deposition (CVD), the process by which the material to be deposited is heated to a very high temperature, transforming it to its gaseous state. The material and the wafer are then placed in a chamber, and the gaseous material reacts with and condenses on the surface of the wafer, forming a thin layer.

• CVD is similar to what happens when you take something cold out of a refrigerator, put it in a warm room, and water from the air condenses on the cold surface.
  
• Unlike other techniques, CVD can create layers of conductive, non-conductive, or semiconductive materials, making it ideal for semiconductor manufacturing.

Electrochemical deposition (ECD), the process by which a wafer is submerged in a liquid containing positive ions of a conductive material, then connected to a power source. When the wafer is charged, ions in the liquid are attracted and adhere to the wafer, forming a thin layer of the conductive material.

• Compared to PVD (explained below), ECD is more like dipping an item in a can of paint.
  
• ECD is used to create copper connections-interconnects-that link devices in an integrated circuit.

Physical vapor deposition (PVD), the process by which a thin film is deposited by vaporizing a conductive material in a vacuum, then allowing that vapor to cool, settle, and condense on a wafer's surface.

• PVD is like spray painting, in that it is hard to control precisely where the material lands.

Ultraviolet thermal processing (UVTP), the process by which patterns on a wafer are exposed to ultraviolet (UV) light that emits high-energy photons. The UV light is absorbed by the exposed atoms or molecules on the wafer's surface, which excites them and causes them to heat up. The combination of UV light and heat modify the exposed surface, rapidly creating a non-conductive pattern.

• Picture a magic wand that emits ultraviolet light. The UV light zaps specific areas on the wafer.

Pulsed laser deposition (PLD) is a variation of the PVD process that uses a high-powered pulsed laser to strike a target material causing a plasma plume. The plume is directed toward and is deposited on a substrate. This process allows for the deposited material to form ultra-thin films over time.

• Go Deeper: The Advantages of Pulsed Laser Deposition (PLD)

Depending on the desired speed and precision of the final product, a manufacturer will employ any number of the above deposition methods.

CVD Variations

Because CVD requires extremely high temperatures, variations of the CVD process have emerged:

Plasma-enhanced CVD (PECVD) is a chemical vapor deposition process that uses plasma to deposit dielectric thin films from a gas state to a solid state on a substrate. By using plasma to provide energy for deposition reactions, it reduces stress between different layers of thin films.

• PECVD allows lower temperature processing rather than purely thermal methods, which is advantageous because it can help avoid potential damage to the substrate due to elevated temperatures.

Atomic-layer deposition (ALD) is a highly precise process that deposits a few layers of atoms at a time. This is done by putting the wafer in a reactor chamber and then alternating its exposure to different gases. ALD is useful in creating uniform coatings with sub-nanometer thickness control.

• During ALD, precursor molecules react with the surface until all available sites are consumed, resulting in self-limiting growth. This controlled process ensures uniformity and prevents overgrowth.

High-density plasma CVD (HDP-CVD) works much like PECVD, the difference being that greater amounts of electricity are applied, creating a super-charged, faster-traveling plasma that coats small gaps in the wafer's surface more effectively.

• HDP-CVD is most useful in coating complex structures thoroughly.

All these methods listed play important roles in the fabrication of high-performance, high-density, and energy-efficient chips that will power the AI era.

Lam's Role

Lam offers many families of deposition systems:

VECTOR^®- Dielectric Film Deposition - Plasma enhanced CVD with high productivity multi-station reactor and isolated walls for improved particle control.

Striker^® - Dielectric ALD - Multi-station temporal reactor design (fixed wafer location) enabling atomic layer deposition of thin, conformal films with leading uniformity and repeatability at high productivity.

ALTUS^®- Metal ALD/CVD - Multi-station ALD/CVD deposition tool enabling leading productivity with superior fill and resistivity performance.

SABRE^®& SABRE^® 3D - Metal ECD/ELD - Electrochemical deposition (ECD) and electroless deposition systems (ELD) for metallization. Advanced cell design with innovations in chemistry, waveform, and process control enabling for high deposition rate electrochemical deposition (ECD) of large geometry TSV metallization with excellent fill rate and stability.

SOLA^®- UVTP - Treatment of insulating materials that are otherwise easily damaged. SOLA's post-deposition film treatments stabilize insulating material, improving chip performance.

SPEED^®- HDP-CVD - Deposits insulation layers between conductive areas of a chip by filling gaps of varying sizes. SPEED products' precise filling of these gaps ensures electrical paths within a chip remain separate, resulting in a higher level of control over that chip's processes.

Pulsus^TM- PLD - Supports deposition of a wide range of materials. Pulsus delivers scandium aluminum nitride (ScAlN) films with the highest scandium content available. Pulsus products are especially effective for Specialty Technologies applications

Reliant^®- CVD, HDP-CVD, PECVD, PLD - Supports a wide variety of manufacturing requirements by addressing numerous material and performance needs. By supporting these different technologies in a single offering, Reliant products extend fabs' productive capabilities.

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