With the rapid development of the optoelectronics industry, microelectronics industries such as semiconductors have ushered in a golden period of development, which makes product performance and quality become the pursuit of microelectronics technology companies. High precision, high performance, and high quality are industry standards in many high-tech fields and product inspection standards for enterprises. During the entire microelectronic packaging process, various particles and other contaminants will adhere to the surface of the semiconductor device . The presence of these contaminants will seriously affect the reliability and service life of microelectronic devices.
The quality of the packaging process directly affects the output of microelectronic products, and the biggest problem in the entire packaging process is the contaminants attached to the surface of the product. Plasma cleaning can be applied to the front end of each process according to different links of contaminants. Typically distributed prior to pasting, wire bonding and plastic packaging. The role of plasma cleaning in the entire packaging process mainly includes preventing packaging delamination, improving the quality of welding wire , improving bonding strength, improving reliability, improving yield and saving costs.
Since dry cleaning methods can remove contaminants without damaging the material properties and conductive properties of the chip surface, it has obvious advantages among many cleaning methods. Among them, plasma cleaning has obvious advantages. It has the characteristics of simple operation, high control precision, no heat treatment, no pollution in the whole process, safety and reliability. It has been widely used in advanced packaging fields.
Plasma cleaning technology principle
Plasma is a state of material aggregation in which charged particles have sufficient positive and negative charges in the colloid, or a non-agglomerated system composed of a large number of charged particles. Plasma is composed of positively and negatively charged and metastable molecules and atoms.
On the one hand, when various active particles come into contact with the surface of the object to be cleaned, the various active particles will react with impurities on the surface of the object to form volatile gases and other substances, and then these volatile substances will be sucked away by the vacuum pump . For example, reactive oxygen plasma reacts with organic matter on the surface of the material.
On the other hand, various active particles will bombard and clean the material surface, so that the contaminated impurities on the material surface will be sucked away by the vacuum pump with the air flow. This cleaning method has no chemical reaction and there are no oxides on the surface of the cleaned material, so it can well maintain the purity of the cleaned material and ensure the anisotropy of the material.
( transistor shape), that is, the shape of the transistor. Most early transistors used coaxial packaging, which was later borrowed into optical communications and is called packaging, that is, coaxial packaging. Currently, coaxial devices have dominated the mainstream optical device market due to their ease of manufacturing and cost advantages.
In the development and production of optoelectronic devices, packaging often accounts for 60% to 90% of the cost, of which 80% of the manufacturing cost comes from the assembly and packaging process. Therefore, packaging plays an important role in reducing costs and has gradually become a research hotspot.
Problems in packaging mainly include welding delamination, virtual welding or insufficient bonding strength. The culprit of these problems is contaminants on the lead frame and chip surfaces, which mainly include particulate contamination, oxide layers, organic residues, etc. These contaminants cause the copper lead connections between the chip and the frame substrate to be incomplete or weakly soldered. How to solve pollutants such as particulate oxide layers and improve packaging quality is particularly important.
Plasma cleaning technology mainly uses active plasma to carry out single-effect or double-effect effects such as physical bombardment or chemical reaction on the material surface to achieve the removal or modification of contaminants on the material surface at the molecular level. When used in the packaging process, it can effectively remove organic residues, particulate pollution, thin oxide layers, etc. on the surface of materials, improve the surface activity of the workpiece, and avoid bonding delamination or false welding.
Plasma cleaning can not only greatly improve the bonding performance and bonding strength of the lead frame, but also avoid secondary pollution caused by long-term contact with the lead frame by human factors.
After plasma cleaning technology, the results of product treatment are usually measured by water drop angle or dyne value.The picture below is a comparison of the water droplet angle before and after plasma cleaning technology of a company's silicon photosensitive triode.
According to the test data results before and after experimental cleaning, after the material was cleaned by the plasma cleaning machine , the contact angle of the product surface dropped from 97.363° before cleaning to less than 10° after cleaning, indicating that the plasma cleaning method can effectively remove the product surface Various impurities and contaminants, thereby improving the strength of material bonding and wiring, and effectively eliminating the delamination phenomenon that occurs in the subsequent chip packaging process.
The biggest advantage of plasma cleaning is that it can clean products of various sizes and structures without waste liquid and pollution sources.
