Advantages and disadvantages of [exposure machine]:
Disadvantages: photoresist contamination mask; mask wear, easy to damage, low life (only 5 to 25 times); easy to accumulate defects; industrial level in the 1970s has gradually approached The exposure method has been eliminated, and the domestic lithography machines are all contact exposure. The development mechanism of domestic lithography machines cannot provide the productization of non-contact exposure with higher process requirements.
[Exposure machine] exposure classification:
a, Contact Printing : The mask is in direct contact with the photoresist layer. The exposed image is comparable to the graphic resolution on the mask and the device is simple. Contact type, according to the way of applying force, is divided into : soft contact, hard contact and vacuum contact.
1. Soft contact is to suck the substrate through the tray (similar to the placement of the substrate of the homogenizer), and the mask is placed on the substrate;
2, hard contact is to pass the substrate through a gas pressure (nitrogen), top up, so that it is in contact with the mask;
3. Vacuum contact is to draw air between the mask and the substrate to make it fit better (think of the way the vacuum is placed on the quilt);
Soft & Hard; Harder The tighter the vacuum contact, the higher the resolution, and of course the closer the contact, the greater the damage to the mask and material.
b. Proximity Printing: The mask layer and the photoresist base layer retain a slight gap (Gap), and the Gap is about 0-200 μm. The mask damage caused by direct contact with the photoresist can be effectively avoided, and the mask and the photoresist substrate can be used for a long time; the mask has a long life (more than 10 times) and less pattern defects. Proximity is the most widely used in modern lithography processes.
c. Projection Printing : Use optical system to collect light between the mask and the photoresist to achieve exposure . Generally, the size of the mask will be 4 times that of the transfer pattern. Advantages : Increased resolution :Mask board making is easier : The effect of defects on the mask is reduced.
[Exposure machine] Generally, it is divided into three types according to the simplicity of operation. Manual, semi-automatic, and fully automatic, the lithography machine is also known as: mask alignment exposure machine, exposure system, lithography system, and the like. The general lithography process is subjected to the steps of cleaning, drying, coating, spin coating, soft baking, alignment exposure, post-baking, development, hard baking, etching, etc. of the wafer surface.
Photolithography is the process of using light to make a pattern (process), homogenizing the surface of the wafer, and then transferring the pattern on the reticle to the photoresist to temporarily "copy" the device or circuit structure onto the wafer. .