What are the requirements to get certified in SAP Sales and Distribution (SAP SD) and is it worthy certification?

SAP SD is indeed a good certification and I would quote it as - the place where you start your SAP journey on the CRM side. 

It is the core for moving on to another module in SAP. If you already have enough experience in SAP then you can target for SAP HANA, SAP Supply Chain Management etc. 

In order to get certified in SAP SD , we should get training from authorized SAP centers and write the certification exam for SAP SD module.

Need to prepare  SAP Enterprise Resource Planning for clearing SAP SD Certificaiton 

SAP sd is the base to proceed any further advanced technologies like S/4 Hana enterprise management, and Front Fiore application, either in the cloud or on premise.

SAP sd will teach you the processess all about Order 2 Cash functionalities, intgration with other modules like MM, FI, PP etc