Voltage regulator chips (such as LDOs, switching regulators, etc.) serve as the "voltage guardians" of electronic devices, and their manufacturing process integrates cutting-edge technology from the modern semiconductor industry. The entire process is highly complex, precise, and automated, and can be mainly divided into the following core stages:
Silicon wafer preparation: the cornerstone of everything
Raw material purification: Starting from ordinary quartz sand (silicon dioxide), a series of chemical reduction and purification processes are used to obtain highly pure (99.99999999% or higher, known as "electronic grade") polycrystalline silicon.
Single crystal growth: High purity polycrystalline silicon is melted in a special furnace (such as the Czochralski method or suspension zone melting method), seed crystals are inserted, and slowly rotated and pulled to grow cylindrical single crystal silicon ingots with a perfect lattice structure.
Slicing and Grinding: Silicon ingots are cut into thin circular pieces with a thickness of approximately 0.5-0.8mm using a diamond wire saw, known as "wafers". Then grind the wafer surface to eliminate cutting damage and obtain preliminary flatness.
Polishing: Chemical mechanical polishing of the wafer surface to achieve atomic level smoothness and flatness, laying the foundation for subsequent precision lithography processes. The wafer obtained at this point is the "canvas" for manufacturing chips.
Previous process: "Carving" circuits on the wafer
Oxidation: Growing a dense layer of silicon dioxide film on the surface of a wafer as an insulating layer, masking layer, or transistor gate dielectric.
Photolithography: This is one of the most essential steps, just like taking a photo on a wafer.
Glue coating: Spin coat a layer of photosensitive resist (photoresist) evenly on the surface of the wafer.
Exposure: Using deep ultraviolet light of a specific wavelength, the pattern is projected onto the photoresist through a designed circuit pattern mask. The photoresist in the exposed area undergoes a chemical reaction.
Development: Dissolve the photoresist in the exposed (or unexposed, depending on the photoresist type) area with a chemical solvent, thereby accurately transferring the circuit pattern on the mask to the photoresist layer on the wafer.
Etching: Using photoresist as a protective mask, precise removal of silicon oxide, silicon or other materials in areas not covered by photoresist is achieved through chemical (wet etching) or physical/chemical combination (dry etching, such as plasma etching) methods, thereby forming a three-dimensional structure on the wafer.
Ion implantation: Accelerating ions of specific elements (such as boron, phosphorus, arsenic) to high energy and bombarding the wafer surface. The photoresist and the previously formed structure are used as masks to control the area and depth of ion implantation, thereby changing the conductivity type of silicon (P-type or N-type), forming the source/drain region, resistance, well region, etc. of the transistor.
Diffusion: At high temperatures, doping atoms are moved within the silicon lattice to achieve deeper or more uniform doping distribution, sometimes used in conjunction with ion implantation.
Thin film deposition:
Chemical vapor deposition: Deposition of insulating layers (such as silicon oxide, silicon nitride) or polycrystalline silicon layers (used for gate electrodes, resistors, capacitors, etc.) on the surface of a wafer.
Physical vapor deposition: mainly used for depositing metal layers (such as aluminum, copper, titanium, tungsten), forming interconnects, filling contact holes, etc.
Chemical mechanical polishing: After depositing multiple layers of thin films and metals, CMP technology is used to globally flatten the wafer surface to ensure the accuracy and reliability of subsequent photolithography steps.
Repetitive cycle: The above steps (photolithography, etching, injection/diffusion, deposition, CMP) need to be repeated dozens or even hundreds of times, layer by layer, to construct complex components such as transistors, resistors, capacitors, diodes, and their interconnection structures. Both analog circuits (such as error amplifiers and reference voltage sources) and power devices (such as power transistors) in voltage regulator chips require precise process control.
Post process: connection, packaging, and testing
Wafer testing: Prior to wafer cutting, a precision probe station is used to conduct preliminary electrical performance tests (such as basic functions and key parameters) on each individual chip (Die). Mark chips with poor functionality.
Thinning and Scratching: Grind the backside of the wafer to the desired thickness (usually 100-200 μ m) to facilitate heat dissipation and packaging. Then use a diamond knife or laser to cut the wafer into individual chips along the Scribe Line between the chips.
Chip mounting: Accurately bond qualified chips (Die) to lead frames or packaging substrates (Substrate) through conductive adhesives, solder, or eutectic soldering.
Bonding: Using extremely fine gold, copper, or aluminum wires (or using flip chip bump technology), the solder pads on the chip are connected to the corresponding pins on the lead frame or substrate through methods such as hot press bonding and ultrasonic bonding, establishing electrical connections.
Encapsulation: Place the connected chip and lead frame/substrate into a specific plastic (epoxy resin) or ceramic casing for molding or sealing to provide mechanical protection, heat dissipation channels, and electrical insulation. Common voltage regulator chip packages include SOT-23, SOT-223, TO-220, SOIC, DFN, QFN, etc.
Post curing and electroplating: Heat curing treatment is applied to the plastic package. Electroplating the outer pins of the lead frame (such as tin, tin lead alloy) to improve solderability and corrosion resistance.
Cutting and shaping: Separate multiple packaging units connected together from the lead frame and bend the pins into the final desired shape (such as gull wing shape, J-shape).
Final testing: Conduct comprehensive and realistic electrical performance testing on the packaged voltage regulator chip. This includes key voltage regulation performance indicators: input/output voltage range, load regulation rate, linear regulation rate, static current, ripple suppression ratio, temperature characteristics, overcurrent/over temperature protection function, etc. Only chips that have passed all rigorous tests can be shipped out of the factory.
Summarize the logical chain:
Prepare substrate: high-purity silicon ->monocrystalline silicon ingot ->polished wafer.
Building microstructure: Repeatedly photolithography, etching, doping, deposition, and polishing are carried out on the wafer to manufacture transistors, resistors, capacitors, and other components and their interconnection lines layer by layer like building blocks (previous process).
Segmentation and Interconnection: Testing wafers ->Cutting into chips ->Fixing chips on carriers ->Connecting chip pads and external pins with metal wires (bonding).
Protection and molding: Encapsulate the chip with a casing ->Curing ->Pin electroplating ->Separate individual components ->Pin molding.
Strict inspection: Conduct comprehensive functional and performance testing on the packaged chips to ensure that each voltage regulator chip meets specification requirements (final testing).
The entire process involves hundreds of steps and is completed by automated equipment in a highly clean cleanroom, requiring extremely precise control and strict quality management. Ultimately, only a tiny voltage regulator chip can shoulder the responsibility of providing stable and reliable voltage for electronic devices.