Whats your Aim for joining my company

To be frank ... Your answer should convince the interviewer. You should say like, By utilizing your skills efficiently to grow as an individual and by supporting the team development to grow as an organization. you want to become a good team player in the company.

With such a broad question, the only possible answer is: "the stars" But, seriously, it depends on the company and your personal goals. If the company is Microsoft, then maybe you are looking to participate in developing the next round of tools for developers or learn from the best. The answer to this question really depends on you.