Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
2000-01-24
2002-04-02
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C257S533000, C257S536000, C257S538000, C257S154000
Reexamination Certificate
active
06365956
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resistor element and, particularly, to a high precision resistor element to be used in an impedance matching.
2. Description of the Prior Art
With a recent speed up of a system control, various systems for high-speed interface have been proposed and standardized in semiconductor devices. In many of these interface systems, resistor elements are used for terminating transmission lines.
It has been usual that such resistor element is mounted on a substrate together with a semiconductor device. However, with the recent popularization of high speed interface, it has been requested to incorporate such resistor element in the semiconductor device since the resistor element tends to increase the mounting area.
FIG. 5
is an illustrative plan view of a conventional resistor element incorporated in a semiconductor device. In
FIG. 5
, a first terminal
48
formed by a first wiring layer
47
is connected to one end of a resistor layer (WSi layer)
41
formed in a semiconductor device through a first contact
46
and a second terminal
49
formed by a second wiring layer
45
is connected to the other end thereof through a second contact
42
.
However, it is required that a resistance value of a resistor element for impedance matching or termination is highly precise.
FIG. 6
is a circuit diagram including a resistor element connected in series between a buffer and a wiring of a mounting substrate. Considering, for example, a case where a resistor element
51
formed in a semiconductor device such as shown in
FIG. 6
is series-connected between an output buffer
52
in the semiconductor device and a wiring
53
on a mounting substrate, the purpose of the resistor element
51
is to correct an internal impedance of the output buffer
52
to thereby match it with a characteristics impedance of the wiring
53
. It becomes possible to restrict noise caused by reflection due to increase of signal speed, by precisely performing this impedance matching. Therefore, the resistance value of the resistor element must be highly precise.
When such resistor element is incorporated within the semiconductor device, it is difficult in a conventional layout shown in
FIG. 5
to guarantee the resistance value. That is, since the resistance value R of the resistor element having layout shown in
FIG. 5
is determined by a formula R=&rgr;s×L/W where L is length of the WSi layer, W is width of the WSi layer and &rgr;s is sheet resistance, a change of outer configuration (L and W) due to variation of process such as etching process influences the resistance value directly.
BRIEF SUMMARY OF THE INVENTION
Object of the Invention
An object of the present invention is to provide a highly precise resistor element, which is hardly influenced by variation of size thereof due to process.
Summary of the Invention
A resistor element according to the present invention comprises a resistive layer provided on a semiconductor substrate through a first insulating film, a first wiring layer provided on the resistive layer through a second insulating film, a second wiring layer provided on the first wiring layer through a third insulating film, a group of first contact regions provided in the second and third insulating films for electrically connecting the resistive layer to the second wiring layer and a group of second contact regions provided in the second insulating film for electrically connecting the resistive layer to the first wiring layer. The second contact regions are provided on and along a circular line or a polygonal line having a center registered with a center point of the first contact region group.
REFERENCES:
patent: 4001865 (1977-01-01), Voss
patent: 4008484 (1977-02-01), Maekawa et al.
patent: 5446311 (1995-08-01), Ewen et al.
patent: 5541442 (1996-07-01), Keil et al.
patent: 6023092 (2000-02-01), Tung
Fenty Jesse A.
NEC Corporation
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