Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2003-09-03
2004-08-24
Jackson, Jerome (Department: 2815)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S026000, C438S029000, C438S064000, C438S098000, C438S613000, C438S614000, C438S615000, C257S021000, C257S081000, C257S085000, C257S457000, C257S459000
Reexamination Certificate
active
06780750
ABSTRACT:
This application claims priority to an application entitled “PHOTODIODE FOR ULTRA HIGH SPEED OPTICAL COMMUNICATION AND FABRICATION METHOD THEREFOR,” filed in the Korean Industrial Property Office on Jan. 8, 2002 and assigned Serial No. 02-959, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical receiving element, and particularly to a photodiode used in an optical communication system.
2. Description of the Related Art
In the optical communication, an electrical signal is converted into an optical signal at the transmitting end using a light emitting element and then transmitted through a transmission line, such as an optical fiber. The converted optical signal is converted back into an electrical signal at the receiving end using a light receiving element, such as a photodiode. Most widely used photodiodes have a mesa type structure.
FIG. 1
is a cross-sectional view of a conventional photodiode
10
having a mesa type structure. As shown in
FIG. 1
, the non-doped InGaAs and p-InP are sequentially stacked at one end of an InP substrate
11
by means of a single crystal growing process. An u-InGaAs absorption layer
12
of a mesa type and a p-InP window layer
13
are formed by etching. Thereafter, silicon nitride(SiNx) is stacked on the p-InP window layer
13
so that an insulation layer
14
is formed, and a predetermined portion of the insulation layer
14
is etched so that a part of the p-InP window layer
13
has an opening. A p-type electrode
15
is provided on the open portion of the p-InP window layer
13
. Meanwhile, a non-reflection coating is applied to the position corresponding to the p-InP window layer
13
on the other side of the InP substrate
11
, so that a light receiving region
17
having a predetermined size and an n-type electrode
16
are formed.
In the method of fabricating a photodiode of a mesa type as described above, the non-doped InGaAs and p-InP layers are stacked through the single crystal growth process. Further, the undesirable spreading of a p-type dopant, such as Zn or Cd, is not necessary.
The conventional photodiode having the mesa type structure, however, has several drawbacks in that the non-doped InGaAs and the p-InP are formed as layers in the form of a mesa type, then exposed to the atmosphere. As such, the non-doped InGaAs and the p-InP materials can be oxidized during a fabrication process. This oxidation may cause a deterioration in the quality of the optical element. In addition, a current leakage may occur on the surface that is mesa-etched, i.e., the surface facing the insulation layer, thereby reducing the life of the optical component. Moreover, the InGaAs film whose energy band gap is small, may have a larger current leakage, thus further deteriorating the reliability of the optical circuit.
Furthermore, in an ultra high-speed optical communication, the capacitance of the optical circuit must be small which can be achieved by reducing the spreading region of the p-InP. The photodiode of a related art, however, makes wire bonding by providing a p-type electrode connected directly to the spreading region of the p-InP. Therefore, it is difficult to reduce the area of the spreading region of the p-InP.
SUMMARY OF THE INVENTION
The present invention overcomes the above-described problems, and provides additional advantages, by providing a photodiode used in an ultra high-speed optical communication and its fabrication method capable of improving reliability and lowering the capacitance thereof, by preventing a current leakage and enabling easier subsequent wire bonding.
According to one aspect of the invention, a photodiode for ultra high speed optical communication includes: a substrate; an absorption layer formed on an upper surface of the substrate; a window layer stacked on the absorption layer; an insulation layer stacked on the window layer and having a predetermined hole formed thereon; a spreading region in which a predetermined dopant is spread on the part of the window layer facing the hole; and, an upper electrode connected to the spreading region through the hole and formed in a mushroom shape above the insulation layer.
According to another aspect of the invention, a photodiode for ultra high speed optical communication includes: an InP substrate; an InGaAs absorption layer stacked on one side of the InP substrate; an InP window layer stacked on the InGaAs absorption layer; an insulation layer stacked on the InP window layer and having a predetermined hole formed thereon; a p-InP spreading region in which a p-type dopant is doped on the part of the InP window layer facing the hole; a metal of electrical conductivity electrically connected to the p-InP spreading region through the hole and formed in a mushroom shape above the insulation layer.
According to a further aspect of the invention, a method for fabricating a photodiode for ultra high speed optical communication includes the steps of: preparing a predetermined semiconductor substrate in which a spreading region is included, wherein an absorption layer, a window layer, and an insulation layer are stacked in sequence on the predetermined substrate, and the spreading region is formed by spreading a predetermined dopant on the window layer through an opening formed on the part of the insulation layer; forming a photoresist layer on the insulation layer; forming a hole on the photoresist layer by means of a photoetching method so that the hole is connected to the opening of the insulation layer; forming a metal plated layer connected to the spreading region through the hole formed on the photoresist layer; and, removing the photoresist layer.
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Cha & Reiter L.L.C.
Fenty Jesse A.
Jackson Jerome
Samsung Electronics Co,. Ltd.
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