Semiconductor device manufacturing: process – Forming bipolar transistor by formation or alteration of... – Having heterojunction
Reexamination Certificate
2000-12-21
2003-05-13
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Forming bipolar transistor by formation or alteration of...
Having heterojunction
C438S364000
Reexamination Certificate
active
06562688
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention relates to a method of manufacturing a silicon-germanium heterojunction bipolar transistor (SiGe HBT) and a structure thereof, and more particularly, to a method of forming a base layer including silicon-germanium by epitaxial growth and a structure of the SiGe HBT in a heterojunction bipolar transistor used as a high-speed device.
2. Description of the Prior Art
Presently, due to continuous research and development in the field of electronics and telecommunications, optical transmission at a transmission rate of 10 Gbps or more is practicable using a high-speed device of 60 GHz class or more. In near feature, it is expected that a 20-30 Gbps IC for the optical transmission will be developed using the high-speed device of 100 GHz and an optical transmission system of few hundred Gbps class will be commercialized. Thus, an era of personal telecommunication using moving images will be opened soon. In the field of a radio communication terminal such as a personal mobile communication and GPS (global positioning system) terminal, it is essentially required to be much thinner, lighter, and, as the same time, multi-functionalized with lower power consumption. Therefore, RF (radio frequency) components, which have a problem in their size due to a large occupancy rate, should be formed into an IC. By a development of hybrid IC technology and MMIC (monolithic microwave integrated circuit) technology, the RF components may be formed into the IC, and the quality of the terminal and system is improved.
As one of the silicon bipolar devices, the SiGe HBT in which silicon-germanium is used as a base layer has a high operating speed of 100 GHz or more, and is in the limelight as an advanced high-speed device. The SiGe HBT device employs almost all the existing silicon process as it is and forms the base layer having a thin thickness of 0.02 m with the silicon-germanium using the epitaxial growth. Since the base layer (about 0.02 m) to be thinner than that of a conventional junction transistor is formed by the epitaxial growth using the silicon-germanium having a smaller band gap than silicon, there is some advantage to obtain a high current gain and operating speed with lower power consumption.
In the existing silicon bipolar device technology, Siemens and Daimler-Benz in Germany and IBM and HP in US have mainly developed. Meanwhile, in research and development of the SiGe HBT, IBM, Daimler-Benz, and NEC and so forth has mainly developed. A conventional method of manufacturing the SiGe HBT and structure thereof is as follows.
FIG. 1
shows a cross-sectional view of a conventional heterojunction transistor defining a collector area by LOCOS (local oxidation of silicon) method.
Ion-implanting an n type dopant in a p− type silicon substrate
1
forms a buried collector
11
. Depositing n− type silicon on an entire face of the substrate, in which the buried collector is formed, forms a collector thin film. On of the collector thin film, an anti-oxidising dielectric film as a mask covers a collector area and a collector sinker area. Then, the silicon exposed through the mask is locally oxidised by the LOCOS method to form a collector dielectric film
17
. Therefore, on a portion of the buried collector
11
, the collector thin film except the collector area and the collector sinker area is formed into the collector dielectric film (field oxide film)
17
formed of oxide silicon. An n− type dopant is implanted in the collector sinker area and then heat-treated at a high temperature to form a collector sinker
13
. A silicon-germanium thin film for forming the base grows on the entire face of the substrate and then is patterned except the collector
15
and a portion of the collector dielectric film
17
around the collector
15
so as to form a base thin film. Formed on the collector
15
is a monocrystal base
25
. The base
25
is extended laterally on the collector dielectric film
17
. The base
25
on the collector dielectric film
17
is formed into a polycrystalline or amorphous base semiconductor electrode
23
. On the entire face, there is deposited silicon oxide or silicon nitride to form an emitter dielectric film
37
. The emitter dielectric film
37
is patterned so as to be opened a portion thereof corresponding to an active area of the base (
25
), thereby defining an emitter area. On the entire surface of the substrate, there is formed an emitter semiconductor electrode
39
formed of a polycrystalline silicon containing the n− type dopant such as arsenic and phosphorus, and so forth. Then, the emitter semiconductor electrode
39
is heat-treated to diffuse the n− type dopant on the base thin film and thus form an emitter
35
. The silicon oxide or the silicon nitride is deposited on the entire surface of the substrate to form a passivation film
77
. The passivation film
77
is patterned to form a contact window for exposing the emitter semiconductor electrode
39
. Further, the passivation film
77
and the emitter dielectric film
37
are patterned to form the contact windows for exposing the base semiconductor electrode
23
and the collector sinker
13
. Finally, a metal layer is deposited and then patterned to form a base terminal
81
contacted through the contact window with the base semiconductor electrode
23
, an emitter terminal
83
contacted through the contact window with the emitter semiconductor electrode
39
and a collector terminal contacted through the contact window with the collector sinker
13
(FIG.
1
).
In the LOCOS method as described above, between the collector dielectric film containing the silicon oxide and the collector area containing the n− type impurity, there is formed a clean boundary surface without any crystal defect. However, during the local oxidation of a part of the silicon layer, there is formed a bird's beak at a side of the boundary surface. The bird's beak is an obstacle to reducing a size of the device. Further, when the silicon-germanium thin film grows on the substrate of the silicon oxide film (collector dielectric film) and the silicon (collector), there is a problem that the silicon-germanium thin film selectively grows on only the silicon portion of the substrate.
In order to solve the problem, there is provided a selective epitaxial growth (SEG) method for manufacturing a high density and microminiature heterojunction transistor.
FIG. 2
shows a cross-sectional view of a structure of a SiGe HBT manufactured by the SEG method. The manufacturing method will be described more fully.
Ion-implanting an n-type dopant in a p-type silicon substrate
1
forms a buried collector
11
. Formed on an entire surface of the substrate, on which the buried collector is formed, is a collector dielectric film
17
of silicon oxide. After defining a part of the collector dielectric film
17
, some portions of the collector dielectric film
17
corresponding to a collector area and a collector sinker area are removed so as to expose a portion of the buried collector
11
. A pattern shape of the removed collector dielectric film
17
is formed to have a vertical sidewall. The collector area and the collector sinker area formed on a surface of the monocrystal buried collector exposed through the removed portion of the collector dielectric film
17
are filled with the monocrystal silicon by the SEG method. At this time, the monocrystal silicon excessively grows in the form of a mushroom to be higher than the collector dielectric film
17
. Then, a protruded portion of the grown monocrystal silicon is removed by a chemical-mechanical polishing (CMP) method to flat the surface of the substrate. On the substrate on which a collector
15
and a collector sinker
13
are formed to have a vertical sidewall and a flat surface, silicon-germanium grows to form a base thin film. At this time, monocrystal silicon-germanium grows on the monocrystal silicon, i.e. the collector
15
to form a base
25
making a junction with the collector
Cho Deok-Ho
Han Tae-Hyeon
Lee Soo-Min
Ryum Byung Ryul
ASB Inc.
Lattin Christopher
Niebling John F.
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