Bipolar transistor, semiconductor device, and bipolar transistor manufacturing method

Abstract

Disconnection of a base line is suppressed even when a short-side direction of a collector layer is parallel to crystal orientation [011]. A bipolar transistor includes: a collector layer that has a long-side direction and a short-side direction in a plan view, in which the short-side direction is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction has an inverted mesa shape, and a cross-section perpendicular to the long-side direction has a forward mesa shape; a base layer that is formed on the collector layer; a base electrode that is formed on the base layer; and a base line that is connected to the base electrode and that is drawn out from an end in the short-side direction of the collector layer to the outside of the collector layer in a plan view.

What is claimed is: 
     
         1 . A bipolar transistor comprising:
 a collector layer that has a long-side direction and a short-side direction in a plan view, wherein the short-side direction is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction has an inverted mesa shape, and a cross-section perpendicular to the long-side direction has a forward mesa shape;   a base layer that is formed on the collector layer;   a base electrode that is formed on the base layer; and   a base line that is connected to the base electrode and that is drawn out from an end in the short-side direction of the collector layer to the outside of the collector layer in a plan view.   
     
     
         2 . The bipolar transistor according to  claim 1 , wherein the base line is drawn out to be oblique about the short-side direction of the collector layer in a plan view. 
     
     
         3 . The bipolar transistor according to  claim 1 , wherein the base layer has a long-side direction and a short-side direction in a plan view and the base layer has the same crystal orientation as the collector layer has, the short-side direction of the base layer is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction of the base layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the base layer has a forward mesa shape. 
     
     
         4 . The bipolar transistor according to  claim 1  further comprising a sub collector layer that is formed between a substrate and the collector layer, the crystal orientation of the sub collector layer being the same as the crystal orientation of the collector layer, wherein a cross-section perpendicular to the short-side direction of the collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the collector layer has a forward mesa shape. 
     
     
         5 . The bipolar transistor according to  claim 4 , wherein the substrate is a GaAs substrate. 
     
     
         6 . A semiconductor device comprising:
 a first bipolar transistor which is the bipolar transistor according to  claim 1 ; and   a second bipolar transistor including a second collector layer that has a long-side direction and a short-side direction in a plan view, wherein the long-side direction of the second collector layer is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction of the second collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the second collector layer has a forward mesa shape, a second base layer that is formed on the second collector layer, a second base electrode that is formed on the second base layer, and a second base line that is connected to the second base electrode and that is drawn out from an end in the long-side direction of the second collector layer to the outside of the second collector layer in a plan view.   
     
     
         7 . A bipolar transistor manufacturing method comprising the steps of:
 forming a collector layer and a base layer on a substrate;   wet-etching the collector layer and the base layer so that a short-side direction of the collector layer in a plan view is parallel to crystal orientation [011] of the collector layer;   forming a base electrode on the base layer; and   forming a base line, which is connected to the base electrode and is drawn out from an end of the collector layer in the short-side direction of the collector layer to the outside of the collector layer in a plan view, using a physical vapor deposition method.   
     
     
         8 . The bipolar transistor according to  claim 2 , wherein the base layer has a long-side direction and a short-side direction in a plan view and the base layer has the same crystal orientation as the collector layer has, the short-side direction of the base layer is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction of the base layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the base layer has a forward mesa shape. 
     
     
         9 . The bipolar transistor according to  claim 2  further comprising a sub collector layer that is formed between a substrate and the collector layer and that has the same crystal orientation as the collector layer has, wherein a cross-section perpendicular to the short-side direction of the collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the collector layer has a forward mesa shape. 
     
     
         10 . The bipolar transistor according to  claim 3  further comprising a sub collector layer that is formed between a substrate and the collector layer, the crystal orientation of the sub collector layer being the same as the crystal orientation of the collector layer, wherein a cross-section perpendicular to the short-side direction of the collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the collector layer has a forward mesa shape. 
     
     
         11 . A semiconductor device comprising:
 a first bipolar transistor which is the bipolar transistor according to  claim 2 ; and   a second bipolar transistor including a second collector layer that has a long-side direction and a short-side direction in a plan view, wherein the long-side direction of the second collector layer is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction of the second collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the second collector layer has a forward mesa shape, a second base layer that is formed on the second collector layer, a second base electrode that is formed on the second base layer, and a second base line that is connected to the second base electrode and that is drawn out from an end in the long-side direction of the second collector layer to the outside of the second collector layer in a plan view.   
     
     
         12 . A semiconductor device comprising:
 a first bipolar transistor which is the bipolar transistor according to  claim 3 ; and   a second bipolar transistor including a second collector layer that has a long-side direction and a short-side direction in a plan view, wherein the long-side direction of the second collector layer is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction of the second collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the second collector layer has a forward mesa shape, a second base layer that is formed on the second collector layer, a second base electrode that is formed on the second base layer, and a second base line that is connected to the second base electrode and that is drawn out from an end in the long-side direction of the second collector layer to the outside of the second collector layer in a plan view.   
     
     
         13 . A semiconductor device comprising:
 a first bipolar transistor which is the bipolar transistor according to  claim 4 ; and   a second bipolar transistor including a second collector layer that has a long-side direction and a short-side direction in a plan view, wherein the long-side direction of the second collector layer is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction of the second collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the second collector layer has a forward mesa shape, a second base layer that is formed on the second collector layer, a second base electrode that is formed on the second base layer, and a second base line that is connected to the second base electrode and that is drawn out from an end in the long-side direction of the second collector layer to the outside of the second collector layer in a plan view.   
     
     
         14 . A semiconductor device comprising:
 a first bipolar transistor which is the bipolar transistor according to  claim 5 ; and   a second bipolar transistor including a second collector layer that has a long-side direction and a short-side direction in a plan view, wherein the long-side direction of the second collector layer is parallel to crystal orientation [011], a cross-section perpendicular to the short-side direction of the second collector layer has an inverted mesa shape, and a cross-section perpendicular to the long-side direction of the second collector layer has a forward mesa shape, a second base layer that is formed on the second collector layer, a second base electrode that is formed on the second base layer, and a second base line that is connected to the second base electrode and that is drawn out from an end in the long-side direction of the second collector layer to the outside of the second collector layer in a plan view.   
     
     
         15 . A semiconductor device comprising:
 a third bipolar transistor which is the bipolar transistor according to  claim 1 ; and   a fourth bipolar transistor which is the bipolar transistor according to  claim 1 ,   wherein the base electrode and the base line are used in common in the third and fourth bipolar transistors.   
     
     
         16 . An RF power amplifier module comprising:
 a power amplifier having the bipolar transistor according to  claim 1 .