Auto-doping reduction in semiconductor structure
The present disclosure generally relates to reducing auto-doping in a semiconductor structure. In an example, semiconductor device structure includes a semiconductor substrate, a first epitaxial layer, and a second epitaxial layer. The semiconductor substrate has a first region and a second region. The first region includes a doped layer doped with a first dopant in the semiconductor substrate. The first epitaxial layer is on the doped layer in the first region. The second epitaxial layer is on the first epitaxial layer in the first region and on the semiconductor substrate in the second region.
1 . A semiconductor device structure, comprising:
a semiconductor substrate having a first region and a second region, the first region including a doped layer doped with a first dopant in the semiconductor substrate;
a cap layer on the doped layer in the first region; and
an epitaxial layer on the cap layer in the first region and on the semiconductor substrate in the second region, wherein the epitaxial layer is in direct contact with the semiconductor substrate in the second region.
2 . The semiconductor device structure of claim 1 , wherein:
a concentration of the first dopant in the semiconductor substrate in the second region distal from an interface between the epitaxial layer and the semiconductor substrate is represented in a form c×10 m cm −3 , wherein c is greater than or equal to one and less than ten, and m is an integer; and
a concentration of the first dopant in the epitaxial layer at the interface is equal to or less than greater of: (i) (c+5)×10 m cm −3 and (ii) 8×10 14 cm −3 .
3 . The semiconductor device structure of claim 1 , wherein:
a concentration of the first dopant in the epitaxial layer distal from an interface between the epitaxial layer and the semiconductor substrate is represented in a form c×10 m cm −3 , wherein c is greater than or equal to one and less than ten, and m is an integer; and
a concentration of the first dopant in the epitaxial layer at the interface is equal to or less than greater of: (i) (c+5)×10 m cm −3 and (ii) 8×10 14 cm −3 .
4 . The semiconductor device structure of claim 1 , wherein a concentration of the first dopant in the epitaxial layer at an interface between the epitaxial layer and the semiconductor substrate is less than seventy percent of a concentration of a second dopant in the epitaxial layer in the second region.
5 . The semiconductor device structure of claim 1 , wherein no doped layer doped with the first dopant is in the semiconductor substrate in the second region.
6 . The semiconductor device structure of claim 1 , wherein the first dopant includes antimony, arsenic, or a combination thereof.
7 . The semiconductor device structure of claim 1 , wherein the first dopant includes boron.
8 . The semiconductor device structure of claim 1 , wherein the epitaxial layer includes a second dopant having a conductivity type opposite from the first dopant, and a concentration of the second dopant proximate an interface between the epitaxial layer and the semiconductor substrate is greater than thirty percent of a concentration of the second dopant in the epitaxial layer in the second region distal from the interface.
9 . The semiconductor device structure of claim 1 , wherein the epitaxial layer includes a second dopant having a conductivity type same as the first dopant, and a concentration of the second dopant proximate an interface between the epitaxial layer and the semiconductor substrate is less than one hundred seventy percent of a concentration of the second dopant in the epitaxial layer in the second region distal from the interface.
10 . The semiconductor device structure of claim 1 , further comprising:
a first device including a first doped region in the epitaxial layer in the first region, the first doped region being disposed over the doped layer; and
a second device including a second doped region in the epitaxial layer in the second region, the second doped region being doped with a second dopant of a same conductivity type as the first dopant, the epitaxial layer being doped with a third dopant having a conductivity type opposite from the first dopant.
11 . A semiconductor device structure, comprising:
a silicon substrate having a first region and a second region, the silicon substrate including in the first region a buried layer;
a silicon cap layer on the silicon substrate over the buried layer in the first region; and
a p-type silicon layer on the silicon cap layer in the first region and on the silicon substrate in the second region.
12 . The semiconductor device structure of claim 11 , further comprising:
a first device in the first region, the first device including a doped region in the p-type silicon layer, wherein the first device includes an n-type metal-oxide-semiconductor (MOS) transistor, a p-type MOS transistor, an NPN bipolar junction transistor (BJT), or a PNP BJT; and
a second device in the second region, the second device including a doped region in the p-type silicon layer, wherein the second device includes a laterally-diffused MOS (LDMOS) transistor or a junction field effect transistor (JFET).
13 . The semiconductor device structure of claim 11 , further comprising:
an NPN bipolar junction transistor (BJT) in the first region, wherein the buried layer forms at least a portion of a collector of the NPN BJT; and
a PNP BJT in the second region.
14 . The semiconductor device structure of claim 11 , wherein the buried layer is doped with antimony, arsenic, or a combination thereof.
15 . The semiconductor device structure of claim 11 , wherein the buried layer is doped with boron.