Static information storage and retrieval – Read/write circuit – Having fuse element
Reexamination Certificate
2002-11-06
2004-10-12
Dinh, Son T. (Department: 2824)
Static information storage and retrieval
Read/write circuit
Having fuse element
C361S111000
Reexamination Certificate
active
06804159
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Application No. 2001-340872, filed on Nov. 6, 2001, 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 semiconductor device with fuses and its manufacture method, and more particularly to techniques regarding fuse elements used in a trimming circuit or a redundancy circuit of a semiconductor integrated circuit.
B) Description of the Related Art
A trimming circuit and a redundancy circuit are often formed in a semiconductor integrated circuit. If a fuse circuit having fuse elements is used as a trimming circuit or a redundancy circuit, a trimming process and the like can be performed during or after the manufacture of a semiconductor integrated circuit so that the characteristics of the circuit can be improved as much as possible.
Japanese Patent Laid-open Publication HEI-7-307389 discloses in
FIG. 1
a circuit having a plurality of parallel connections of a serial connection of a fuse element and a MOS transistor. It discloses that a current drive ability necessary for obtaining a breakdown current for breaking down a fuse element is given by a function of the gate width W of a selection transistor:
I
D
=&mgr;C
ox
(
W/L
)×(½)×(
V
GS
−V
Y
)
2
where I
D
is a drain current of a selection transistor in a saturation region, and &mgr; is a mobility of carriers. C
ox
is a gate capacitance of the selection transistor, W is a gate width and L is a gate length. V
GS
is a gate-source voltage and V
Y
is a threshold voltage.
If the value I
D
of a saturation drain current necessary for breaking down a fuse element is known, the gate width W (size) of the transistor capable of breaking down the fuse element can be estimated from the above-described equation. This analysis adopts the assumption that the saturation current of a MOS transistor is used for breaking down a fuse.
In order to melt and break down a fuse element, it is necessary to flow current through the fuse element and heat it to a temperature over the melting point thereof. For example, if single crystal silicon or polysilicon is used as the material of a fuse element, a relatively large current is required because the melting point of silicon is as high as about 1420° C. It is therefore necessary to make large the size of a selection transistor, which hinders high integration of device elements. According to the above-described Publication, a bipolar transistor having a high current drive ability is used as a selection transistor to obtain a large current.
Most of recent integrated circuits are MOS type ICs using MOS FETs as fundamental device elements. If a bipolar transistor is required to be formed in a MOS type IC, the element structure becomes complicated and additional processes are necessary.
SUMMARY OF THE INVENTION
An object of this invention is to reduce an area occupied by a fuse circuit having a fuse element and a selection transistor and fabricated in a MOS IC, by using a MOSFET as the selection transistor and reducing the area occupied by the selection transistor.
According to one aspect of the present invention, there is provided a semiconductor device comprising: a fuse element capable of being electrically broken down by flowing current therethrough, a first voltage being applied to one end of the fuse element; and a MOS type transistor having source, gate and drain terminals and a connection point between the other end of the fuse element and one of the source and drain terminals, a second voltage lower than the first voltage being applied to the other of the source and drain terminals, wherein: the first and second voltages, characteristics of the MOS type transistor and a resistance value of the fuse element are selected so that the fuse element can be broken down when a predetermined program voltage is applied to the gate terminal; and the resistance value of the fuse element is set to such a value as a voltage difference between a voltage at the connection point and the second voltage is lower than a drain voltage of the MOS type transistor at which a drain current starts saturating, when the program voltage is applied to the gate terminal
According to another aspect of the present invention, there is provided a semiconductor device comprising: a fuse element capable of being electrically broken down by flowing current therethrough, a first voltage being applied to one end of the fuse element; and a MOS type transistor having source, gate and drain terminals and a connection point between the other end of the fuse element and one of the source and drain terminals, a second voltage lower than the first voltage being applied to the other of the source and drain terminals, wherein: the first and second voltages, characteristics of the MOS type transistor and a resistance value of the fuse element are selected so that the fuse element can be broken down when a predetermined program voltage is applied to the gate terminal; and the resistance value of the fuse element is further set to such a value as a minimum power capable of breaking down the fuse element is not smaller than 90% of a maximum consumption power of the fuse element calculated from current-voltage characteristics of the MOS type transistor.
According to another aspect of the present invention, there is provided a semiconductor device comprising: a fuse element capable of being electrically broken down by flowing current therethrough, a first voltage being applied to one end of the fuse element; and a MOS type transistor having source, gate and drain terminals and a connection point between the other end of the fuse element and one of the source and drain terminals, a second voltage lower than the first voltage being applied to the other of the source and drain terminals, wherein: the first and second voltages, characteristics of the MOS type transistor and a resistance value of the fuse element are selected so that the fuse element can be broken down when a predetermined program voltage is applied to the gate terminal; and the resistance value of the fuse element is further set to such a value as a breakdown current of the fuse element is in a range from 80% to 98% of a saturation drain current of the MOS type transistor.
A power supplied to the semiconductor device can be used efficiently for breaking down the fuse element.
According to a further aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising steps of: forming on a substrate a serial connection of a fuse element and a MOS type transistor, the fuse element being capable of being electrically broken down by flowing current therethrough, and the MOS type transistor having source, gate and drain terminals and a connection point between one end of the fuse element and one of the source and drain terminals; and applying a voltage higher than a drain voltage of the MOS type transistor at which a drain current starts saturation, between another end of the fuse element and the other of the source and drain terminals, applying a predetermined program voltage to the gate terminal, and breaking down the fuse element by setting a voltage at the connection point between the fuse element and the MOS type transistor to a voltage lower than a drain voltage of the MOS type transistor in a saturation region in which a drain current saturates.
According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising steps of: forming on a substrate a serial connection of a fuse element and a MOS type transistor, the fuse element being capable of being electrically broken down by flowing current therethrough, a first voltage being applied to one end of the fuse element, the MOS type transistor having source, gate and drain terminals and a connection point between one end of the fuse element and one of the source and drain terminals, and a second voltage lower than
Kamiya Takayuki
Omura Masayoshi
Dickstein, Shapiro, Morin & Oshinsky L.L.P.
Dinh Son T.
Yamaha Corporation
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