Effects of electrostatic factors on integrated circuit packaging
With the continuous and stable growth of my country's national economy and the continuous innovation and development of production technology, the requirements of production technology on the production environment are getting higher and higher. In large-scale and ultra-large-scale IC production, the previous and subsequent processes put forward higher requirements on the production environment, not only to maintain a certain temperature, humidity and cleanliness, but also to pay enough attention to electrostatic protection.
As we all know, the packaging industry belongs to the post-production process of the entire IC production. In this process, for plastic packaged IC, hybrid IC or monolithic IC, there are mainly wafer thinning (grinding), wafer cutting (dicing), core bonding (bonding), packaging (package), pre-curing, Plating, printing, post-curing, rib cutting and assembly, each process has different requirements for different process environments.
Effects of electrostatic factors on integrated circuit packaging
First, the causes of static electricity can be seen everywhere. With the rapid development of science and technology and the high degree of automation of industrial production, the harm of static electricity in industrial production is obvious, which will cause various obstacles, limit the improvement of automation level, and affect product quality. According to the actual situation of our factory's IC packaging and production process, the reasons for static electricity are mainly as follows.
1. Most of the building decoration materials in the production workshop use high-resistance materials. The production process requires the use of clean workshops or ultra-clean workshops.
It is required that the particle size of the dust removal particles is changed from 0.3 μm to 0.1 μm, and the dust particle density is about 353 pieces/m3. Therefore, in addition to installing various dust removal equipment, inorganic and organic dust-free materials should also be used to prevent dust. However, the electrical properties of building materials are not considered as an indicator. There are no regulations on the design specifications for clean workshops of industrial enterprises. The interior decoration materials used in the clean workshop of the IC factory mainly include polyurethane elastic floor, polyamide fiber, hard plastic, polyethylene, plastic wallpaper, resin, wood, white porcelain board, enamel, gypsum, etc. Most of the above materials are polymer compounds or insulators. For example, the resistivity of the plexiglass body is 1012 ~ 1014/cm, and the resistivity of the polyethylene body is 1013 ~ 1015/cm, so the conductivity is relatively poor, and the static electricity generated for some reason is not easy to leak to the ground through them, resulting in static electricity. accumulation.
2. Human body static electricity
The different movements and back and forth of the operators in the clean workshop, the close contact and separation between the sole and the ground, as well as the activities and friction of various parts of the human body, whether it is fast walking, slow walking or trotting, will generate static electricity, which is called walking electrification; when the human body moves When standing up, the work clothes worn by the human body are separated from the chair surface after contact, and static electricity will also be generated. If the static voltage of the human body cannot be eliminated and the IC chip is touched, it may cause the IC breakdown unknowingly.
3. Static electricity from air conditioning and air purification
Since IC production is required to be carried out at a relative humidity of 45-55%, air conditioning and air purification should be carried out at the same time. The dehumidified air should be sent to the clean room through the primary filter, intermediate filter, high efficiency filter and air duct. The wind speed of the total air duct is generally 8 ~ 10m/s, and the inner wall of the air duct is painted. Static electricity is created when dry air moves relative to the duct, dry air, and filter. Pay attention to the sensitive relationship between static electricity and humidity.
In addition, semi-finished products and IC products generate static electricity during packaging and transportation, which is one of the factors of electrostatic charging.
Secondly, static electricity is very harmful to ic. Generally speaking, static electricity has the characteristics of high potential and strong electric field. In the process of electrostatic charging-discharge, transient high-current discharges and electromagnetic pulses (EMPs) are sometimes formed, resulting in a wide-spectrum electromagnetic radiation field.
In addition, compared with conventional electrical energy, electrostatic energy is relatively small, and electrostatic discharge (ESD) parameters are uncontrollable, which is a random process that is difficult to repeat, so its role is often overlooked. Especially in the field of microelectronics, the harm it does to us is staggering. It is reported that the direct economic loss caused by static electricity is as high as hundreds of millions of yuan every year, which has become a major obstacle to the development of the microelectronics industry.
In the semiconductor device workshop, the yield of IC, especially VLSI, will be greatly reduced due to the dust adsorbed on the chip. Operators in the Ic production workshop wear clean overalls. If the human body has static electricity, it is easy to absorb dust and dirt. If these dust and dirt are brought to the operation site, it will affect the product quality, deteriorate the product performance, and greatly reduce the IC yield. If the radius of the adsorbed dust particles is greater than 100m, the line width is about 100m, and the film thickness is less than 50m, the product is most likely to be scrapped.
Again, the damage of static electricity to IC has certain characteristics.
(1) Concealment Unless electrostatic discharge occurs, the human body cannot directly perceive static electricity, but the human body may not feel electric shock when electrostatic discharge occurs. This is because the electrostatic discharge voltage perceived by the human body is 2~3kv, so the static electricity is hidden.
(2) Potential Some sinks have no obvious performance degradation after electrostatic damage, but multiple cumulative discharges will cause internal damage to the IC device and cause hidden dangers. So static electricity has potential damage to ic. (3) Under what circumstances will random ICs be damaged by static electricity? It can be said that all the processes of an IC chip from generation to damage are threatened by static electricity, and the generation of these static electricity is also random, and its damage is also random.
(4) Due to the fine, thin and tiny structural features of microelectronic integrated circuit products, the failure analysis of complex electrostatic discharge damage is time-consuming, costly, and technically demanding, and high-precision instruments are often used. Even so, some electrostatic damage phenomena are difficult to distinguish from damage from other causes. It leads people to mistake ESD-damaged failures for other failures, often due to early failures or failures that are unknown before ESD damage is fully understood, thereby unconsciously masking the true cause of the failure. Therefore, analyzing the damage of static electricity to integrated circuits is complicated.
In summary, in the process of IC processing, production and packaging, it is necessary to establish an electrostatic protection system! IC packaging production lines have stricter requirements on static electricity. In order to ensure the normal operation of the production line, the clean workshop should be decorated with anti-static building materials, and all personnel entering and leaving the clean workshop should wear anti-static clothing. In addition, packaging companies can formulate corporate standards or specific anti-static requirements according to relevant national standards and the actual situation of the company to cooperate with the normal operation of the integrated circuit packaging production line. With the expansion of China's integrated circuit packaging production lines, the annual improvement of packaging capacity, the increase of packaging varieties, and the higher requirements for product quality and output, it has become more important to strengthen various software and hardware requirements and the electrostatic protection awareness of all employees. This is also playing a "protagonist" and "invisible killer" that affects the quality of our products. Therefore, electrostatic protection will be the main problem of the entire integrated circuit industry at present and in the future.