Semiconductor Wafer Fabrication: The Process of Creating Integrated Circuit Devices


Semiconductor Wafer Fabrication
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The term semiconductor wafer fabrication refers to the process by which a semiconductor device is manufactured. These devices are usually integrated circuits, or “chips” that are used in electrical and electronic devices. Some of the processes involved in the process include optical lithography, etching, and the use of equipment for throughput.

Processes involved

Silicon wafer fabrication involves a number of different processes. This process begins with the preparation of silicon, then continues through several stages of semiconductor manufacturing. It includes the removal of chemical and physical contaminants, followed by the growth of dielectric film and patterning of device structures.

Silicon ingots are cut into thin wafers. Typically, they are 0.75 mm thick, and range in size from 300 mm to 12 inches. In some cases, wafers can hold a few dozen chips.

The wafer is shaped and polished to form a smooth surface. A coating of photoresist is applied to the wafer. It is then exposed to ultraviolet light. Once the resist layer dissolves, the photoresist is removed, leaving a pattern on the surface of the wafer.

Next, the silicon wafer is sliced into ‘dies’, and the drain and source regions are patterned. These dies are then stacked together to form a transistor. After the dicing is completed, the silicon wafer is set in a carrier cage. The carrier then spins between lapping plates.

Optical lithography

Photolithography is a process that produces minutely patterned thin films on a silicon wafer. It is a common method for manufacturing semiconductor devices. However, there are a few limitations to photolithography. Specifically, the ability to produce nanometre-sized structures is limited by the wavelength of light used.

The wavelength of light used in optical lithography is 193 nm. Current state-of-the-art tools use this wavelength, which allows for production of feature sizes down to 50 nm. Another important limitation of this type of lithography is that it requires a large number of wafers to be processed.

In order to be able to achieve high throughput, the size of the die needs to be chosen carefully. Currently, most leading-edge lithography tools are capable of producing 1.8T pixels per hour. This makes it possible to create 150 to 300 mm patterned wafers in an hour.

In order to prevent contact issues, proximity exposure involves exposing the wafer in a step-and-repeat pattern. This enlarges the reticle structures and prevents any contact with the resist.

Etching

Etching semiconductor wafers is an important step of semiconductor manufacturing. Etching is done to remove the layers of the wafer’s surface and to improve the flatness of the surface. It is also used to create interconnections. This technique is widely applied in the production of integrated circuits.

In etching, a semiconductor wafer is immersed in a flowing etchant. Etchant is typically made from hydrofluoric acid or a diluent. The etching rate is controlled through temperature and time. During etching, the wafer’s front and back surfaces are separated, and a thin layer of the wafer’s surface is etched to remove microcracks.

Chemical etching is an isotropic process, wherein the flow of etchant from one end of the tank is generally transverse to the axis of rotation of the wafers. A typical etchant flow rate is between 7 and 15 standard liters per minute. Alkaline etching is another etching technique, and it can be performed on the back side of the wafer. During alkaline etching, the wafer’s flatness is improved and its surface irregularity is reduced.

Equipment throughput

Equipment throughput is one of the most important parameters of a semiconductor wafer fabrication plant. It is the basis of capacity management and production planning. There are many ways to estimate throughput. The most common method is through the use of spreadsheets with macro programs. However, it is not ideal for the next generation of manufacturing systems.

Throughput is calculated by calculating the number of wafers processed per hour. For example, a modern Fab can process eight wafers per run. Similarly, a Fab can produce five lots from different families at the same time.

Throughput is usually calculated by optimization techniques. A fab can improve its throughput by lowering the overall cycle time. In addition, a Fab can reduce the variability of its throughput. The equipment throughput of a fab can be affected by the following factors. These factors include the capacity of the equipment, the equipment’s efficiency, the technology used, and the dispatching policy.

As a result, it is difficult to develop a reliable estimation of equipment throughput. An inaccurate ETH can affect the expected profit of a semiconductor wafer fabrication plant. To avoid this, a fab needs to have a systematic approach for calculating throughput.


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