What is laser bonding and debonding? What other applications does laser bonding have?

What is laser bonding and debonding?

The bonding technologies commonly used at present are: eutectic bonding technology and anodic bonding technology. Eutectic bonding technology has been used in the manufacture of various MEMS devices, such as pressure sensors, micro pumps, etc., which require mechanical support structures to be bonded on the substrate. Silicon molten bonding is mostly used in SOI technology, such as Si-SiO2 bonding and Si-Si bonding, but this bonding method requires a higher annealing temperature. Anodic bonding does not require high temperature, but requires a strong electric field of 1000-2000V for effective bonding, and such a strong electric field will affect the performance of the wafer. Therefore, many researchers introduced the bonding method of laser-assisted bonding, the principle of which is to focus the pulsed laser on the bonding interface and use the local thermal effect of the short-pulse laser to achieve local heating bonding. This bonding method has many advantages, such as no need for pressure, no high-temperature residual stress, and no need for strong electric field interference.

As the wafer size gradually increases and the thickness decreases, the wafer is easy to break during the tape-out process, so the carrier layer is introduced. Bond the thin wafer to the carrier layer to prevent the wafer from being damaged during the tape-out process. Compared with other debonding methods, laser debonding can use polyimide as a bonding agent. This method can withstand temperatures above 400掳C, while general bonding agents will denature at 200掳C, which makes general bonding agents fail when the wafer undergoes high and low temperature cycles. Since laser debonding technology requires the laser to act on the adhesive between the carrier and the wafer, the carrier needs to be able to transmit the laser of the corresponding wavelength. Currently, the most commonly used laser is ultraviolet laser, and the carrier is a glass wafer substrate. Laser debonding technology is mostly used for the peeling of various thin silicon wafers.

Laser BondingWhat other applications are there?

1. Laser Annealing

Laser annealing technology is mainly used to repair semiconductor materials, especially silicon. The traditional heating annealing technology is to place the entire wafer in a vacuum furnace and anneal it at a certain temperature (usually 300-1200鈩? for 10-60min. This annealing method cannot completely eliminate defects, but high temperature leads to the degradation of material properties and precipitation of dopant substances. Therefore, since the end of the last century, the research on laser annealing has become very active, and a variety of laser annealing methods have been developed, such as millisecond pulse laser annealing, nanosecond pulse laser annealing and high-frequency Q-switched pulse laser annealing. In recent years, laser annealing has achieved some mature applications at home and abroad. The main advantages of laser annealing are:

(1) Short heating time, can obtain a high-concentration doping layer;

(2) Heating is limited to the local surface layer and will not affect the physical properties of surrounding components;

(3) It can reach a very deep hemispherical contact area;

(4) Since the laser beam can be shaped to be very fine, it provides the possibility for micro-area thin layer annealing.

2. Laser drilling

Laser drilling is widely used in metal, PCB, glass panel and other fields. Laser drilling is still an emerging application in the semiconductor field. Due to the high precision and high surface finish requirements of the semiconductor industry, our company currently uses the short pulse high-speed optical drilling process. With the rise of 3D packaging technology, through silicon via (TSV) technology has gradually developed, and the demand for laser drilling is becoming increasingly strong. At present, laser drilling has obvious advantages and disadvantages. The advantages are low drilling cost, no consumables, and the ability to drill different materials, etc.; the disadvantages are mainly the rough inner wall of the hole, low efficiency of dense drilling, damage to the strength of the drilling material, etc. Of course, researchers are also studying new drilling technologies to overcome the shortcomings of current drilling, such as laser combined with chemical drilling, etc.