My dear friend it is illegal. You can not hold anybody with this type of systems. If you want to obtain a Bond it should be two way ie., if you want a person to continue with you for three years, the same is applicable from the employee side also ie., you can not ask him to go out for a minimum of three years which is not possible. Except in case of huge investment on employee for his development / Training which is very visible and can be proved in court of law if require only can bind other wise you can not. Hence pl concentrate on making employee owning their responsibilities and job with your organization rather than this bonded labour system.
Pl. work out an action plan on how to retain an employee starting from job description, role and responsibility, growth/ career patterns , training, development, happy work place, family orientation, incentives, reward and recognition, delegation of authority, worklife balance. For all this you should have patience, information inflow mechanism, openness etc.,
Thanks and regards - kameswarao