Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-12-01
2003-04-08
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S222000, C257S225000, C257S231000, C257S232000, C257S233000, C257S241000, C257S243000
Reexamination Certificate
active
06545304
ABSTRACT:
This application is based on Japanese Patent Application HEI 11-346479 filed on Dec. 6, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a solid-state image pickup device of CCD type and a method of producing the same.
b) Description of the Related Art
Since a mass-production technique of a charge-coupled device (CCD) has been developed, there have increasingly appeared apparatuses in which a solid-state image pickup device of CCD type (to be simply referred to as a solid-state image pickup device herebelow) is used as a line sensor (linear sensor) or an area image sensor.
A solid-state image pickup device for a line sensor includes a group of photoelectric converter elements formed in a line in a semiconductor substrate, a charge transfer path formed adjacent to the group of photoelectric converter elements on the substrate, and a plurality of readout gates to read signal charge from the photoelectric converter elements to feed the signal charge to the charge transfer path. When necessary, discharge gates are arranged to form an overflow drain of horizontal type.
The photoelectric converter element is generally composed of a photodiode.
The charge transfer path in the solid-state image pickup device for a line sensor is composed, for example, of a CCD of two-phase driving type. The charge transfer path includes a charge transfer channel formed in the semiconductor substrate and a plurality of transfer electrodes intersecting or crossing the charge transfer channel in a plan view.
The charge transfer channel includes, for example, two potential barrier regions and two potential well regions (storage regions) for one photoelectric converter element. The potential barrier and well regions are alternately formed in this order beginning at a position on an upstream side.
In this specification, movement of the charge through the charge transfer path is assumed to be a flow and a relative position of each constituent member or the like of the solid-state image pickup device is expressed as, for example, “downstream of member X” or “upstream of member Y”.
Each transfer electrode constituting the charge transfer path is arranged over the potential barrier or well region. Among four transfer electrodes arranged for one photoelectric converter element, two upstream transfer electrodes are commonly connected to each other and two downstream transfer electrodes are commonly connected to each other.
One readout gate is formed for each photoelectric converter element. Each readout gate includes a readout gate region formed in the semiconductor substrate to be contiguous to the associated photoelectric converter element and an associated charge transfer channel, and a readout gate electrode formed over the readout gate region. The readout gate electrodes are electrically connected to each other to constitute one electrode line.
Signal charge transferred through the charge transfer path is sent from the transfer path, for example, via an output gate or directly to a floating diffusion section or region. The signal charge is fed from the floating diffusion section to a predetermined source follower circuit. The signal charge is amplified by and is then outputted from the source follower circuit.
A reset transistor is formed using the floating diffusion section. The signal charge after the amplification (detection) is absorbed via a drain region of the reset transistor into a power source.
On the other hand, the solid-state image pickup device for an area image sensor includes a plurality of constituent units each of which includes (i) a group of photoelectric converter elements, (ii) a charge transfer channel, and (iii) one readout gate for each photoelectric converter element. A predetermined number of transfer electrodes are formed to intersect the charge transfer channel of each unit in a plan view.
One charge transfer channel and the transfer electrodes intersecting the charge transfer channel of each unit in a plan view constitute one charge transfer path. In an intersection region between each charge transfer channel and each transfer electrode in a plan view, a charge transfer stage is formed.
The transfer electrodes are composed only of transfer electrodes (to be referred to as readout transfer electrodes herebelow) each of which includes a section also serving as a readout gate electrode. Or, the transfer electrodes are composed of a plurality of transfer electrodes (to be referred to as transfer dedicated electrodes herebelow) each of which does not function as a readout gate electrode and a plurality of readout/transfer electrodes. The configuration of the transfer electrodes is decided based on a specification of arrangement of the photoelectric converter elements or the like.
The number of transfer electrodes for each photoelectric converter element is appropriately determined according to a specification of arrangement of the photoelectric converter elements, a method of driving the charge transfer paths, and the like. The charge transfer path is composed of a CCD of, for example, three-phase, four-phase, or eight-phase driving type.
The solid-state image pickup device for an area image sensor further includes an output transfer path. The output transfer path is connected to each of the charge transfer paths. The output transfer path is composed of a CCD of, for example, three-phase or four-phase driving type.
At a downstream end section of the output transfer path, a floating diffusion section is formed. The section is a constituent component of a reset transistor. When necessary, a discharge gate is disposed to form a horizontal overflow drain.
In the solid-state image pickup device for a line sensor, each transfer electrode, each readout gate electrode, each discharge gate electrode, and the gate electrode of the reset transistor are formed on a semiconductor substrate with an electrically insulating film between each of the electrodes and the semiconductor substrate. This also applies to the solid-state image pickup device for an area image sensor.
The semiconductor substrate of the solid-state image pickup device is a silicon substrate or a complex substrate in which a silicon layer is formed on one surface of a substrate made of quartz glass, or the like in general. The electrically insulating film to electrically isolate the semiconductor substrate from each transfer electrode and each gate electrode is, for example, a film made of silicon oxide, an ON film or,an ONO film.
In this specification, the ON film indicates a two-layer electronically insulating film being composed of an oxide layer formed on the semiconductor substrate and a nitride layer formed on the oxide layer. The ONO film indicates a three-layer electronically insulating film being composed of an oxide layer formed on the semiconductor substrate, a nitride layer formed on the oxide layer, and an oxide layer formed on the nitride layer.
Each of the electrodes is made of, for example, a first layer of polycrystalline silicon (1-polysilicon layer) or a second layer of polycrystalline silicon (2-polysilicon layer).
In the electrode constitution, when a film of silicon oxide (to be referred to as “insulating film I” in some cases herebelow) to electrically the electrodes from the semiconductor substrate is beforehand disposed on the semiconductor substrate, two phenomena or events may possibly occur as follows.
In a process to form an oxidized surface-layer of the 1-polysilicon layer to electrically isolate an electrode made of the 1-polysilicon layer from an electrode made of a 2-polysilicon layer, an insulating film I grows at a location in which the 2-polysilicon layer is to be formed. Resultantly, film thickness of the insulating film I below, the electrode made of the 2-polysilicon layer become greater than that of the insulating film I below the electrode made of the 1-polysilicon layer. This phenomenon will be referred to as phenomenon A1 herebelow.
In the process to form the oxidized surface-la
Arent Fox Kintner & Plotkin & Kahn, PLLC
Fuji Photo Film Co. , Ltd.
Jackson Jerome
Nguyen Joseph
LandOfFree
Solid-state image pickup device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solid-state image pickup device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid-state image pickup device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3002383