Yes, one must be prepared to do shift work and lots of OT. Working all weekend is common. So its a matter of personal choice. If u can endure the hardship, the monetary reward is quite substantial as mentioned above.

However, it is not true that semicon in SG is going downhill. On the contrary, many semicon companies have even expanded their local production plants (google for more info). Semicon is the heart of all technological products, unless we stop using these products, semicon industry will not start going downhill or become redundant (or sunset industry).

Technology is improving at a rapid pace, hence the cycle life of a product is getting shorter. Fine tuning the production to run a specific product takes time and it needs to be fast hence engineers work alot of OT during these periods. Since cycle life is shorten, engineers work even harder. The good is more OT pay, the bad is lousy work life balance.

Most entry positions are definitely operations for MSE students. You will be in-charge of a small part of the manufacturing like wafer cleaning, thin film deposition, etc. MSE grads are well trained for all these processes as its a major part of our curriculum. Do note that when you are posted to a particular manufacturing section, you will be expected to stay there for a few years. The reason being it takes some time for fresh engineers to understand and excel.