Originally posted by: shortylickens
Hynix Semiconductor.
I worked in Photolithography.
After a monthly maintenance action on a machine that exposes wafers, I made some little little error while performing minor calibrations with a test wafer. After the procedure was done it apparantly had an offset of 1 or 10 or 100 microns, I forget which.
Anyway it was bad. The kind that make a microchip useless. About 20 or 21 casettes went through before a process tech caught the error. Luckily, Etch was running slow that night and none of them had been processed. If they had, we estimate that about One million, five hundred and seventy five thousand dollars worth of silicon would have been ruined.
As such, the time required to reprocess those wafers only cost us about one-hundred thousand.
In my defense I had been on the night shift for about 17 months and had never caught up on my sleep. I was making mistakes left and right. For that matter, so were most of the rest of the folks in the place. I simply dont do that well on a 12-hour night job. I had to learn that the hard way. Of course, I had already learned in the Navy I am useless when tired, but I always assumed that was because I never slept. Turns out that not all sleep is the same.
In Psychology class we learned that there are 5 stages of sleep, and you body cycles through stages 2,3,4, and 5 throughout the night. If you dont get plenty of each stage, you're mental alertness will fail you througout the day.
Apparently, since I was sleeping days and working nights, I was NEVER getting proper sleep, ever. Nor were most of my coworkers, but some of them were better than others at faking alertness.
Statistically in a group of 1200 people, only about 3 or 4 of them are truly nocturnal. The rest are normal people trying to get by.