A method for forming a SiGe HBT, which combines a SEG and Non-SEG growth, is
disclosed.
The SiGe base layer is deposited by a Non-SEG method. Then, the first-emitter layer
is developed directly upon the SiGe base layer that has a good interface quality
between the base-emitter. Next, a second poly silicon layer, which has a dopant
concentration range within 1E19 to 1E21 (atom/cc), is deposited by SEG method.
It not only reduces the resistance of the SiGe base layer, but also avoids the
annealing that may influence the performance of the device.