There is no particular need for any subject or any course to be undertaken to become an IAS officer. You just need to finish your graduation course in any of the field like Engineering, medical, bcom, BA, BSc, etc. There is nothing to be particular about any stream in IAS exam.

I will tell the subjects asked in the UPSC IAS examination - General Studies, English, Essay writing, any language of your choice, optional subject of your choice (includes agriculture, chemistry, economics, civil, electrical;, mechanics, etc.)

Refer to the link below for more details..

https://competition.careers360.com/articles/upsc-ias-exam-pattern

Best wishes. Thank you.