The working principle of a photolithography machine is to form a pattern by concentrating light intensity within a certain range. First, the patterning software converts the circuit pattern data into digital signals and transmits them to the photolithography machine controller. The controller, using a laser and a mirror, forms a raised circuit pattern within the control range of the photolithography machine. Next, the photolithography machine focuses the light onto a semiconductor wafer and then uses photosensitive resin to lithographically pattern the wafer. In this process, the light is focused into extremely small spots and transmitted to the photosensitive material on the semiconductor wafer. As the illumination continues, the photosensitive resin forms a circuit pattern on the semiconductor wafer. After completion, the photosensitive resin is heated and removed, leaving the remaining area on the semiconductor wafer. This creates a tiny and precise circuit pattern.
Modern lithography machines are technologically advanced, capable of producing extremely small circuit patterns and very high resolutions. These advancements also help expand the functionality on circuit boards. However, because they are only suitable for creating high-precision circuit patterns, lithography machines are typically used only during mass production. Furthermore, as the semiconductor industry continues to evolve, even more sophisticated solutions are needed, such as extreme ultraviolet lithography (EUV), which requires even higher energy concentrations.
What is a lithography machine?
A lithography machine (Mask Aligner), also known as a mask alignment exposure machine, exposure system, or lithography system, is commonly used for mask alignment lithography, hence the name Mask Alignment System.
A typical photolithography process involves several steps, including cleaning and drying the silicon wafer surface, applying a primer, spin-coating photoresist, soft baking, alignment and exposure, post-baking, development, hard baking, and etching.
Photolithography means creating a pattern (process) using light.
The process of applying photoresist to a silicon wafer and then transferring the pattern from the photomask onto the photoresist is a temporary "copy" of a device or circuit structure onto the silicon wafer.
What are the uses of a lithography machine?
① Used for chip manufacturing;
② Used for packaging;
③ Used in LED manufacturing;
④ The lithography machines used to produce chips are a weakness in China's semiconductor equipment manufacturing. Domestic wafer fabs rely on imports for the high-end lithography machines they need.
How does a lithography machine work?
In the chip manufacturing process, the lithography machine uses a series of light source energy and shape control methods to transmit a light beam through a mask with a circuit diagram drawn on it. After the objective lens compensates for various optical errors, the circuit diagram is scaled down and mapped onto the silicon wafer. Then, chemical methods are used to develop the circuit diagram to obtain the circuit diagram etched on the silicon wafer.
A typical photolithography process involves several steps, including cleaning and drying the silicon wafer surface, applying a primer, spin-coating photoresist, soft baking, alignment and exposure, post-baking, development, hard baking, and laser etching. A chip that has undergone one photolithography step can then be coated with photoresist and exposed again. More complex chips, with more layers in their circuitry, require more precise exposure control.
What is the structure of a lithography machine?
1. Measurement stage/exposure stage: A worktable that holds silicon wafers.
2. Laser: Light source, one of the core components of a lithography machine.
3. Beam corrector: Corrects the incident direction of the laser beam to make the laser beam as parallel as possible.
4. Energy Controller: Controls the energy that is ultimately irradiated onto the silicon wafer. Insufficient or excessive exposure will seriously affect the image quality.
5. Beam shape setting: Set the beam to different shapes such as circular or ring-shaped. Different beam states have different optical characteristics.
6. Light shield: Prevents light beams from hitting the silicon wafer when exposure is not required.
7. Energy Detector: Detects whether the final incident energy of the beam meets the exposure requirements and feeds back to the energy controller for adjustment.
8. Photomask: A glass plate with a circuit design engraved on its interior.
9. Mask stage: A device that supports the movement of the mask, with motion control precision at the nanometer level.
10. Objective lens: The objective lens is used to compensate for optical errors and to scale down the circuit diagram proportionally.
11. Silicon wafer: A round wafer made of silicon crystal.
12. Internal enclosed frame and vibration damper: isolate the workbench from the external environment, keep it level, reduce external vibration interference, and maintain stable temperature and pressure.
Lithography machines are indispensable equipment in the semiconductor field. No matter what kind of chip is being manufactured, it is impossible to do without lithography machines. If aero engines represent the highest level of human technological development, then lithography machines are the most dazzling jewel in the semiconductor industry. They are characterized by the highest technical difficulty, the highest cost per unit, and the ability to determine integration density.
Today we'll learn about lithography machines.
The working principle of a lithography machine is essential in the entire chip manufacturing process; almost every process relies on lithography technology. Lithography is also the most critical technology in chip manufacturing, accounting for more than 35% of the chip manufacturing cost.
Once the IC design is completed, the chip manufacturing and packaging must be outsourced to a wafer foundry.
In chip manufacturing, wafers are indispensable. Silicon rods are purified from silicon dioxide (SiO2) ore, such as quartz sand, using a series of chemical and physical smelting methods, and then cut into circular single-crystal silicon wafers, which are called wafers.
Wafers cut from silicon rods
Wafers are the foundation for manufacturing various computer chips. We can compare chip manufacturing to building a house with blocks, stacking them layer by layer to achieve the desired shape (i.e., various chips). However, without a good foundation, the house will be crooked and not what we want. To create a perfect house, a stable substrate is needed. In chip manufacturing, this substrate is the wafer.
Photolithography is a precision microfabrication technology. Conventional photolithography uses ultraviolet light with a wavelength of 2000–4500 angstroms as the image information carrier, and photoresist as the intermediate (image recording) medium to realize the transformation, transfer and processing of patterns, and finally transfer the image information to the wafer (mainly silicon wafer) or dielectric layer.
Photolithography is the process of creating the circuitry and functional areas needed for chip manufacturing. Simply put, it's like printing the circuitry and functional areas designed by chip designers onto a wafer, similar to taking a photograph. While a photograph is printed on film, photolithography doesn't create photographs; instead, it creates circuit diagrams and other electronic components.
Just like an empty brain, instructions are put into it through photolithography so that the brain can function. Circuit diagrams and other electronic components are the instructions designed by chip designers.
Photolithography includes two main aspects: photocopying and etching processes.
Photocopying process: The device or circuit pattern pre-made on the mask is precisely transferred to the required position by the exposure system onto the photoresist layer pre-coated on the wafer surface or dielectric layer.
Etching process: Using chemical or physical methods, the unmasked areas of the wafer surface or dielectric layer covered by the photoresist layer are removed, thereby obtaining a pattern on the wafer surface or dielectric layer that perfectly matches the pattern of the photoresist layer. Since the functional layers of an integrated circuit are three-dimensionally overlapping, the photolithography process is always repeated multiple times. For example, a large-scale integrated circuit requires approximately 10 photolithography steps to complete the transfer of patterns across all layers.
Photocopying technology is a photolithography machine, while etching process is an etching machine.
Based on the principles of photolithography, photolithography machines were created. These machines use a series of methods to control the energy and shape of the light source, transmitting a beam of light through a mask depicting a circuit pattern. After the objective lens compensates for various optical errors, the circuit pattern is scaled down and projected onto a wafer. Different photolithography machines have different imaging ratios, some 5:1, others 4:1. Then, chemical methods are used for development to obtain the circuit pattern (i.e., the chip) etched onto the wafer.
