Bluetooth is a promising technology for short-range wireless communication and networking, mainly used as a replacement for connected cables. The specification defines how to build a piconet and there are several existing solutions to construct a scatternet from the piconets. The process to construct a scatternet is called scatternet formation. We find that a tree shape scatternet called bluetree has three defects: First, it lacks efficiency in routing because the bluetree may form a skewed tree, not a balanced tree, resulting in longer routing paths. Second, the parent nodes in bluetree are very likely to become the bottlenecks of communication. Third, it lacks reliability. When a parent node is lost, it could cause several separated subtrees. In this paper we introduce an algorithm to generate the bluetree hierarchically; namely, the algorithm grows nodes in the bluetree level by level. This resolves the foregoing defects in scatternet formation. We construct the bluetree, keeping it balanced, to achieve the shorter routing paths, and establish the connection pairs between the siblings to provide another path to route. As a result, the traffic load at parent nodes can be greatly improved. Besides, once a parent node is lost, only two separated parts will be caused. A better reliability is therefore obtained.