Hey
Biotechnology course shares some of its subject with robotics field like for example
1. Microcontroller and microprocessor
2. Virtual Instrumentation
3. Sensor technology
4. Image processing
5. Circuits and network
6. Control system
7. Artificial intelligence
8. Neural network

The only addition subjects which you will be learning in robotics are

1. Mechatronics
2. Drives for robot
3. Kinematics and dynamic of robot
4. Robot vision
5. Computer numerical program

According to me an average student can take up Mtech in robotic after completing Biotechnology since most of the subject are common