Silicon is purified to around 99.9999999%! Then it is sliced into very thin round sheets called wafers.
The type used in the Skywater 130nm process is doped to become p-type.
Here’s a great video about how silicon wafers are made.
And these great videos are about the birth of the Japanese semiconductor industry. Jump to about 12 minutes in to see
how they pull the silicon ingot out of the molten material.
After the wafers are ready, they can be patterned using the photolithographic process, using a series of masks.
This is probably the best course you can get your hands on for practical stuff. If you're a hands-on guy like me it's really worth it to have the course. You can do it hand in hand with whatever theory that you're following as well. Hands-on is king for me, I mean what's the point of reading if you can't experiment - this is the mindset of an engineer.