In 2020, more than a trillion chips were produced worldwide, which equates to 130 chips owned and used by each person on the planet. Yet even so, the recent chip shortage continues to show that this number has not yet reached its upper limit.
Although chips can already be produced on such a large scale, producing them is not an easy task. The process of manufacturing chips is complex, and today we will cover the six most critical steps: deposition, photoresist coating, lithography, etching, ion implantation, and packaging.
Deposition
The deposition step begins with the wafer, which is cut from a 99.99% pure silicon cylinder (also called a “silicon ingot”) and polished to an extremely smooth finish, and then a thin film of conductor, insulator, or semiconductor material is deposited onto the wafer, depending on the structural requirements, so that the first layer can be printed on it. This important step is often referred to as “deposition”.
As chips become smaller and smaller, printing patterns on wafers becomes more complex. Advances in deposition, etching and lithography are key to making chips ever smaller and thus driving the continuation of Moore’s Law. This includes innovative techniques that use new materials to make the deposition process more precise.
Photoresist Coating
Wafers are then coated with a photosensitive material called “photoresist” (also called “photoresist”). There are two types of photoresists – “positive photoresists” and “negative photoresists”.
The main difference between positive and negative photoresists is the chemical structure of the material and the way the photoresist reacts to light. In the case of positive photoresists, the area exposed to UV light changes structure and becomes more soluble, thus preparing it for etching and deposition. Negative photoresists, on the other hand, polymerize in the areas exposed to light, which makes them more difficult to dissolve. Positive photoresists are the most used in semiconductor manufacturing because they can achieve higher resolution, making them a better choice for the lithography stage. There are now a number of companies around the world that produce photoresists for semiconductor manufacturing.
Photolithography
Photolithography is crucial in the chip manufacturing process because it determines how small the transistors on the chip can be. At this stage, the wafers are put into a photolithography machine and are exposed to deep ultraviolet light. Many times they are thousands of times smaller than a grain of sand.
Light is projected onto the wafer through a “mask plate” and the lithography optics (the lens of the DUV system) shrinks and focuses the designed circuit pattern on the mask plate onto the photoresist on the wafer. As previously described, when the light hits the photoresist, a chemical change occurs that imprints the pattern on the mask plate onto the photoresist coating.
Getting the exposed pattern exactly right is a tricky task, with particle interference, refraction and other physical or chemical defects all possible in the process. That’s why sometimes we need to optimize the final exposure pattern by specifically correcting the pattern on the mask to make the printed pattern look the way we want it to. Our system uses “computational lithography” to combine algorithmic models with data from the lithography machine and test wafers to produce a mask design that is completely different from the final exposure pattern, but that’s what we want to achieve because that’s the only way to get the desired exposure pattern.
Etching
The next step is to remove the degraded photoresist to reveal the desired pattern. During the “etch” process, the wafer is baked and developed, and some of the photoresist is washed off to reveal an open channel 3D pattern. The etching process must form conductive features precisely and consistently without compromising the overall integrity and stability of the chip structure. Advanced etching techniques allow chip manufacturers to use double, quadruple and spacer-based patterns to create the tiny dimensions of modern chip designs.
Like photoresists, etching is divided into “dry” and “wet” types. Dry etching uses a gas to define the exposed pattern on the wafer. Wet etching uses chemical methods to clean the wafer.
A chip has dozens of layers, so etching must be carefully controlled to avoid damaging the underlying layers of a multi-layer chip structure. If the purpose of etching is to create a cavity in the structure, it is necessary to ensure that the depth of the cavity is exactly right. Some chip designs with up to 175 layers, such as 3D NAND, make the etching step particularly important and difficult.
Ion Injection
Once the pattern is etched onto the wafer, the wafer is bombarded with positive or negative ions to adjust the conductive properties of part of the pattern. As a material for wafers, the raw material silicon is not a perfect insulator nor a perfect conductor. Silicon’s conductive properties fall somewhere in between.
Directing charged ions into the silicon crystal so that the flow of electricity can be controlled to create the electronic switches that are the basic building blocks of the chip, the transistors, is called “ionization”, also known as “ion implantation”. After the layer has been ionized, the remaining photoresist used to protect the un-etched area is removed.
Packaging
Thousands of steps are required to create a chip on a wafer, and it takes more than three months to go from design to production. To remove the chip from the wafer, it is cut into individual chips using a diamond saw. These chips, called “bare die,” are split from a 12-inch wafer, the most common size used in semiconductor manufacturing, and because the size of the chips varies, some wafers can contain thousands of chips, while others contain only a few dozen.
These bare wafers are then placed on a “substrate” – a substrate that uses metal foil to direct the input and output signals from the bare wafer to the rest of the system. It is then covered with a “heat sink”, a small, flat metal protective container containing a coolant to ensure that the chip stays cool during operation.
Company Profile
Zhejiang NeoDen Technology Co., Ltd. has been manufacturing and exporting various small pick and place machines since 2010. Taking advantage of our own rich experienced R&D, well trained production, NeoDen wins great reputation from the world wide customers.
with global presence in over 130 countries, the excellent performance, high accuracy and reliability of NeoDen PNP machines make them perfect for R&D, professional prototyping and small to medium batch production. We provide professional solution of one stop SMT equipment.
Add: No.18, Tianzihu Avenue, Tianzihu Town, Anji County, Huzhou City, Zhejiang Province, China
Phone: 86-571-26266266
Post time: Apr-24-2022