HCB Chapter 717 The Story of Engraving the Mask Plate?
Chapter 717 The Story of Engraving the Mask Plate?
Yes, the lithography machine that is still being assembled is a contact lithography machine.
What does "contact type" mean?
If you want to hear more, I could write over ten chapters...
What? You don't want to hear it?
No, you guys should still listen to this, let me just fill in a couple of cents. I still need to go and change the highlighted parts...
Simply put, contact lithography is like developing a photograph; the photomask needs to be in direct, close contact with the silicon wafer surface coated with photoresist. Besides the photomask, alignment is the biggest challenge. Technicians have to manually fine-tune it under a microscope, moving the mask and silicon wafer position bit by bit. This process is extremely inefficient and can easily damage the expensive mask.
Imagine you're trying to draw an extremely complex circuit diagram on a tiny, tiny stamp using the finest pen. How tiny is this stamp? About the size of your little fingernail! And this 'pen' isn't an ordinary pen; it's light!
Contact lithography is exactly what it does!
How do we do it?
First, you need a 'mold,' or more professionally, a photomask. This mold is like a transparent glass plate on which a circuit pattern, magnified many times, is engraved using extremely precise processes, such as hand-drawing and photolithography.
Then, you have a processed 'little stamp'—a silicon wafer coated with photoresist. Photoresist is a magical thing; when exposed to light of a specific wavelength (such as ultraviolet light), its chemical properties change, and it can be washed away with a specific solution.
Here comes the crucial step!
You have to press this glass mold with the large pattern engraved on it, perfectly fitting without any gaps, directly onto that silicon wafer coated with photoresist! Just like stamping!
Then, the light source is turned on—the high-pressure mercury lamp Dr. Lan Ying mentioned earlier—allowing light to pass through the transparent part of the glass mold and shine onto the photoresist underneath. The areas illuminated by the light 'soften' the photoresist. The areas not illuminated (blocked by the opaque chromium layer on the mold) remain unchanged.
Finally, a wash with a chemical solution removes the photoresist that has been exposed to light and softened, revealing the silicon underneath. In areas not exposed to light, the photoresist remains, acting as a protective film.
In this way, the circuit pattern on the glass mold is precisely "printed" onto the silicon wafer! After subsequent steps such as etching and ion implantation, transistors and circuits can be made.
It sounds pretty simple?
Pooh!
The biggest challenge lies in the word 'press'!
Imagine trying to perfectly bond two pieces of glass, thinner than paper and flatter than a mirror, to a silicon wafer, without the slightest gap! If that gap were even a hair's breadth (a few micrometers), the printed pattern would be blurry! It would look double! The circuit would be ruined!
Therefore, this "pressing" action, or the process of alignment and fitting, is the most difficult, delicate, and critical part of the entire contact lithography process!
Yes, as you can see from the many adjectives I used to emphasize this, you can tell how tedious contact lithography is...
Oh, and that's not all... What's even worse is that silicon wafers and glass molds expand and contract with temperature changes! A slight change in temperature will cause their size to change slightly as well!
This tiny difference makes a world of difference when it comes to micrometer-level precision! The alignment might have been perfect just moments ago, but a change in temperature can cause it to become misaligned!
Now you understand, right?! Why Master Weng's 'ghost hands' are so important! So precious!
He was practically made for this job!
hoo hoo hoo!
This is what we call the collision between old craftsmen and new techniques!
What does it mean for our civilization to have a long and rich history? This is it!
Just think about Master Weng's craftsmanship! He can hand-grind a mirror finish of Ra0.1mm onto hard alloy steel! He can use his own strange, homemade blade to carve perfectly precise tooth shapes on gears the size of a grain of rice!
How steady are his hands? So steady that he can carve words on a strand of hair!
So stable that it can sense the most subtle 'temperament' of metal!
It's so stable that it can ignore the subtle effects of temperature changes!
This is what you call a real treasure!
This is what a true master craftsman is like!
……
Jiang Xia shouted those last few sentences. His voice was so loud that even Dr. Lan Ying couldn't help but hold the microphone a little further away.
Thanks to the Ministry of Posts and Telecommunications' improvements in microphone technology, the words "National Craftsman" resonated like a pebble dropped into a calm lake, clearly spreading throughout the entire experimental area and being heard by technicians from other factories who were assisting in the work.
"Hiss... Who is this? Saying such a name out loud, aren't they afraid of breaking their teeth in the wind?" A middle-aged technician wearing work clothes with different factory logos couldn't help but mutter under his breath.
His gaze swept back and forth between Dr. Lan Ying, who was holding the microphone, and Master Weng, who looked unremarkable and even a little hunched over, in the corner.
"Who is this young man? Which company does he work for? He's got a big mouth than he's strong!" Another voice said with obvious disdain. "If this master craftsman's skills are so good, how come I've never heard of him? The title of 'National Craftsman'... tsk tsk, aren't you afraid of biting off more than you can chew? You can't just throw that label around like that."
"Exactly, with such a heavy workload at Lanzhou University of Technology, how come there are still people here shouting slogans?" someone whispered in agreement, their tone revealing dissatisfaction.
These key personnel, drawn from various cooperating factories, were already overwhelmed with the progress of the experiment. When they heard Jiang Xia's earth-shattering shout, they felt it was both jarring and abrupt.
They didn't know Jiang Xia; they just thought he had suddenly come out with an incredibly loud voice and spoke wildly.
These hushed whispers spread like tiny ripples in the stifling air of the laboratory.
The center of the discussion—Master Weng—was standing awkwardly a short distance behind the lithography machine. His usually steady, rock-solid hands, capable of sensing the "temperament" of metal, were now awkwardly rubbing the faded corner of his work clothes. His bronze cheeks were flushed, his head was slightly lowered, and his eyes darted around, as if he wanted to shrink into a corner.
The greatest praise he had ever heard in his life was nothing more than "Good work, reward him!" But more often it was "If you dare to delay again, you'll get twenty lashes and be sent to the kiln to do hard labor!" or "You'll be stripped of your craftsman status, and your son can forget about ever making a living like this again!"
The words "craftsman of the nation" weighed heavily on him like a mountain, making him feel both apprehensive and at a loss, and even making him feel that he had caused trouble for Jiang Xia, who had uttered those words.
Unfortunately, the microphone was too far away. Jiang Xia, who was still marveling at his good fortune that Master Weng had suddenly appeared to help him solve his problem, suddenly became inspired to write a poem:
"There is a man named Weng Dehai who is very skilled. He can use the tin on his fingertips to make circuits, pins, thin wires, chips, solder pads, and digital tubes. He can make the most of every opportunity and achieve exquisite results. He once helped me make a calculator, which was a test instrument made in Jiangxia."
"Master Weng's hands, like withered pine branches, could twist a hair into a thread and thread a needle. At that time, the circuit board was densely covered with hundreds of solder joints, as fine as stars; the ten pins of the LED tubes were uneven, as thin as spider legs. An ordinary person would shake the soldering iron slightly, causing the two wires to stick together and all previous work to be wasted. Master Weng held his breath and concentrated, steadying the soldering iron with his thumb and forefinger. The solder wire touched it lightly, and in an instant, the solder melted like dew, solidifying on the solder joint, smooth as a bead, perfectly even."
"His skill in connecting the jumper wires was even more evident: the wires were as thin as silkworm silk, less than an inch long, and needed to span two or three solder pads while avoiding seven or eight pins. Master Weng ignored this, relying solely on his feel, sticking and picking at the wires with ease, making them connect seamlessly like a snake entering its hole, without the slightest error. Once the entire device was soldered and powered on for decoding, the digital tubes lit up with red lights, and the numbers rotated freely, all thanks to Master Weng's 'ghostly hand'."
coax……
Xiao Daimao's pretentious words immediately ignited the scene.
"Hahaha, how about it? Does it provide enough emotional value? Of all the lyrics I've written, I think this is my masterpiece!"
Hearing the excited voices on the other end of the line, Xiao Daimao looked smugly at the copy of "Yu Chu Xin Zhi" on the table. He had taken it from the bookshelf in the train carriage out of boredom while waiting for the call to connect, and it was covered in notes made by someone.
“Full! It’s almost overflowing…” Dr. Lan Ying pulled the microphone back to her side, looked at the excited crowd with some helplessness, and sighed.
"You've taken your pretentious writing to a whole new level..."
"You little brat, if you can't appease them, you'll be waiting for your ahoge to be plucked out!"