JPH0613465A - Semiconductor device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide a fuse that can be stably and reliably cut in a semiconductor integrated circuit and that has high reliability. [Structure] The structure of a fuse 102 is such that a fuse material is crossed and has four terminals 104 to 106, a high voltage is applied to a pair of terminals facing each other, and another terminal is electrically cut. A fuse material intersecting the current path is electrically cut by insulating layers formed on both sides of the current path flowing by the high voltage. [Effect] Since the thickness of the insulating layer is about 0.2 μm, the fuse is an inexpensive fuse having a sufficient withstand voltage, high long-term reliability, and no special process step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuse circuit for a semiconductor integrated circuit.

[0002]

2. Description of the Related Art In a semiconductor integrated circuit (hereinafter referred to as an IC), the characteristics and functions of the IC may be changed by performing some operation from outside the IC. For example, a programmable logic device or a PROM can perform a user's own desired function by a write operation. Further, even when the characteristics of the analog ICs are matched, there is one in which the characteristics can be matched individually by an operation peculiar to the IC. When the adjustment or the change of the function is performed after the IC is completed in this way, there have been FAMOS and fuses as the conventional main techniques.
As a fuse, conventional metal such as NiCr, T, which is easily sublimated,
iW, PtSi, etc. are used. Fig. 6 shows a typical view
Circuit. Here, 600 is AL wiring and 601 is PO.
In the LY Si fuse, 602 is a contact. AL
When a high voltage is applied to both ends of the wiring 600, POLY Si
A large current flows through the fuse 601 and the fuse blows.

[0003]

This conventional fuse is the most general one, but the material of the fuse is, as mentioned above, a metal that easily sublimes, and requires a step which is not in the standard IC process. There are two ways to do this, or to use a conductive material (eg, POLY Si) in standard process steps. However, when a special metal is used here, the number of process steps increases and the wafer cost increases. Furthermore, a new capital investment is required for the special metal process, which is very unsuitable for fuses of only a few bits. When POLY Si is used as a fuse in a CMOS IC or the like, the fuse is CVD.
When it is covered with a protective film such as POLY Si, it becomes very difficult to melt down. Therefore, the PO of the fuse part
CVD is left open on LY Si. In this case, because of the reliability problem, the space around the CVD open part needs to be wide enough to make the fuse circuit very large. Also, there is no problem when cutting the fuse in the wafer inspection, but after mounting the mold, the mold material blocks the CVD open of the fuse part, so POL
Y Si will not melt. Thus, the prior art was not optimal for products with a small number of bits and to be programmed after mounting in the mold. Also the conventional POLY
In the Si fuse, when an attempt is made to cut with a large current, the flow of electrons pushes the AL atom along the current path in the fuse, causing a shot rather than a break. The present invention is intended to solve such a problem, and provides a reliable and inexpensive fuse that can be electrically cut without requiring a special step in the standard process. .

[0004]

[Means for Solving the Problems] In a fuse, a fuse material is crossed to form a fuse shape having four terminals, and a disconnection voltage is applied between a pair of terminals to make a logical disconnection / non-disconnection determination between another pair of terminals. It is characterized by performing.

In the fuse, the fuse material is crossed 4
It is characterized in that it has a fuse shape having a terminal, and the intersection is offset to one of the four terminals.

The fuse has a wiring metal that is connected to the fuse material, and the fuse material is connected to a portion that is connected to the wiring metal that applies a positive voltage and a wiring metal that applies a negative voltage when the fuse is cut. A fuse portion for disconnecting the portion and a portion for connecting with the wiring metal for applying the negative voltage, and a portion for connecting with the wiring metal for applying the positive voltage is increased in area. To do.

In the fuse, the size of the contact for connecting the wiring metal to which a negative voltage is applied and the connection portion of the fuse is set to 6 μm × 4 μm or more, and the shape of the contact is vertical to the fuse portion. And

[0008]

EXAMPLES The present invention will be specifically described with reference to examples.
One embodiment of the present invention is shown in FIG. In FIG. 1, 101 is a wiring AL, 102 is a fuse, and here is POLY S.
i is used. 103 is AL101 and POLY Si
The contacts connecting 102 are shown. Where 10
Reference numerals 4, 105, 106, and 107 denote connection terminals for respective signals, which are connected to each other via the low resistance of POLY Si 102. The fuse of the present invention can electrically disconnect the terminals 105 and 107 by applying a high voltage between the terminals 104 and 106 and passing a current. FIG. 2 shows a state of the fuse according to the present invention as seen from the top surface after passing a current. Reference numerals 104 to 107 correspond to the terminals having the same numbers in FIG. Here, 201 is a trace of current flow and 202 is an insulating layer on the side surface of the current path. Further, FIG. 3 shows a cross-sectional structure of a portion indicated by a dashed-dotted line 203. FIG. 3A is a sectional view before fuse cutting, and FIG. 3B is a sectional view after cutting. When the fuse of the present invention is cut and then observed, a trace such as 201 in FIG. 2 can be clearly seen. You can also see that a groove-like line runs on both sides of this current path. The cross section is enlarged and observed to see how the current path and the groove are formed. In FIG. 3, 301 is LOCOS, 302 is POLY Si, and 303 is POLY SiLIGHT.
OXIDE and 304 are CVD protective films. 305.3
Reference numeral 07 denotes a POLY Si portion where current does not pass, and 306 denotes a POLY Si portion after passing current. POLY
When a large current is applied to Si, the temperature rises partly to 1000 ° C. or higher, and POLY Si having a high impurity concentration has a melting temperature of 10
It melts because the temperature is close to 00 degrees. It expands due to melting, and due to this expanding force, the current flowing portion becomes round and evenly applies pressure to the surrounding oxide film.
When the electric current is cut off, the expanded part cools and contracts. The surrounding oxide film, which was under pressure due to expansion, is POLY Si
POLY Si305, in which the electric current did not flow
It enters between the 307 and the POLY Si 306 where the current has flowed, and completely separates them and electrically cuts them. After a large current flows due to such a phenomenon, the current path is
The insulating layer is formed on the side surface of the OLYSi portion. When viewed from above, this insulating layer looks like a groove on the side surface of the current path. The thickness of this insulating layer is about 0.2 to 0.3 μm, and it can be said that the withstand voltage with respect to a normal operating voltage is sufficient. In FIG. 2, the terminal 107 is completely separated from the other terminals 104, 105 and 106 by the insulating layer 202 and electrically disconnected. FIG. 4 shows an example of a circuit using the fuse of the present invention. In this circuit, a high voltage is applied to the external terminal, and the fuse is selected and cut by an internal selection switch. After cutting, pull up P before and after the fuse
ch MOS transistor and pull down Pc
h HIGH or LOW by MOS transistor
Signal is determined. More specifically, reference numeral 401 denotes a fuse of the present invention, which applies a high voltage to an external terminal indicated by 406 to turn on a fuse selection switch 402 (here, an NPN bipolar transistor is used). . Select switch 402 from VDD, fuse 401
A large current flows through the path to the external terminal 406 via. Further, the pull-up PchMOS transistor 404 and the fuse 401 are connected to each other, and the fuse 401 is connected to the pull-up PchMOS transistor 404.
ll downPch MOS transistor V
Connect to SS. Here, the terminal 104 of the fuse 401 is connected to the emitter of the selection switch 402, and the terminal 106 is connected to the external terminal 406. The terminal 107 is pullup
It is connected to the Pch MOS transistor 404, and the terminal 105 is connected to the pull down Pch MOS transistor 403. VDD-selection transistor 402-
Fuse 401-A large current flows to external terminal 406, and terminal 107 of fuse 401 and other terminal 10
4.105.106 are electrically disconnected. Where pu
The connection point between the ll up Pch MOS transistor 404 and the terminal 107 of the fuse 401 is indicated by 407.
The potential of the connection point 407 is pull up Pch MOS
Transistor 404, fuse 401, and pull d
It is determined by the ratio of each resistance of the down Pch MOS transistor 403. pull up Pch MOS transistor 404 ON resistance is pulled down Pc
By making it larger than the ON resistance of the hMOS transistor 403, the connection point 407 is set before the fuse is disconnected.
Potential becomes LOW and becomes HIGH after the fuse is cut off because the fuse impedance becomes infinite. In this way, the fuse using the present invention is the conventional POL
As compared with a type in which YSi is cracked and electrically cut, a thick insulating layer enters into the cut portion for insulation, so that insulation is surely performed and extremely high reliability can be obtained.

In FIG. 1, terminals 104, 105 and 106
・ When the POLY Si connecting 107 is orthogonal,
In rare cases, it may not be completely disconnected depending on the running condition of the electric current. That is, the terminals 104 to 10 in FIG.
When a current runs through the central portion of POLY Si connected to 6, the area near the terminals is not insulated and a low impedance region is formed.

The cut state of the fuse of the present invention will be described with reference to FIG. Since the current runs along the path with the lowest impedance, it is possible to control the place where the current runs to some extent by devising the shape. As shown in FIG. 2, P connecting the terminal 104 and the terminal 106
POL connecting OLY Si, terminal 105 and terminal 107
When the intersection point of YSi is biased to the opposite side of the terminal 107 to be cut with respect to the terminals 104 and 106, the terminals 104 to 1
The path with the lowest impedance to 06 is a path like 201, and the terminal to be cut is surely cut. In addition, the cutting shape of the conventional fuse may change in various cases depending on the case, and sometimes it is not cut, but by devising the shape of the fuse and controlling the current path in this way, it can be surely and almost the same. It is possible to obtain various cut shapes.

By the way, in fuse cutting, the higher the voltage and the higher the current applied, the more reliably the fuse can be cut. However, in the conventional fuse shape, A
Fuse POLY Si due to L migration
The phenomenon that the AL runs and runs along the current path in the inside often occurs. This phenomenon easily occurs at a considerably low voltage depending on the shape of the fuse.

An improvement of this situation is shown in FIG. 5 as another embodiment of the present invention. Here, 501 is AL wiring and 502 is AL wiring.
And 503, 50 by the contact connecting POLY Si
Although 5 and 506 are the same POLY Si, the numbers are assigned according to the parts for convenience of explanation. Reference numeral 503 denotes a fuse portion, 505 denotes a high voltage negative side voltage, and 506 denotes a POLY Si portion to which a high voltage positive side voltage is applied. Fifty
Reference numeral 4 denotes a contact that connects the POLY Si portion 505 and the AL wiring, and is a contact opening that is flat and wide in the direction orthogonal to the current path so that the electric field is not concentrated as compared with the contact 502. Since the migration occurs due to the high current density, if the current density at the connection portion with the AL is lowered, the migration becomes very difficult to occur. Here, the current is the POLY Si portion 506.
From the side to the POLY Si portion 505 side, but the electrons move in the opposite direction. Therefore, in order to reduce the current density on the POLY Si portion 505 side, the POLY Si portion 505 side
Lower the resistance of. Further, the distance to the contact with AL is increased, and the contact opening is widened by the lateral side as described above. This causes P via contact 504.
The current density of the current flowing through the AL in contact with OLY Si is low, and migration is much less likely to occur as compared with the conventional fuse structure. According to an experiment conducted by the author, it was found that the contact size of 6 μm × 4 μm or more is very effective. As a result, a considerably high voltage can be applied to the fuse portion 503 which is originally desired to be cut, and the fuse portion 503 can be cut more reliably.

[0013]

As described above, when the fuse of the present invention is used, it is not necessary to newly add a special process step.
Cost performance is sufficient even with only a few bit of fuse
Good monthly cost and very cheap. Further, this is comparable in size to the case where a special fuse metal is used, and can be easily applied to a large-capacity fuse array. Also as a program characteristic, a normal POL
A more reliable writing characteristic can be realized as compared with the Y Si fuse. Further, compared with the conventional fuse which makes a destructive cut which hardly allows control, the control of the current path allows the cutting to always have the same cutting shape, so that stable characteristics can be obtained. A very high reliability is obtained for a long period of time because a thick insulating layer is inserted into the fuse. Also, fuse cutting conditions can be set in a wide range from relatively low voltage to high voltage. Furthermore, because of the relatively low energy of cutting, a protective film (CVD)
It is also very beneficial to the reliability of the IC since it does not have a destructive effect on the IC.

As described above, by using the present invention, it is possible to provide a fuse which can be easily manufactured in terms of price, characteristics and quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuse according to an embodiment of the present invention.

FIG. 2 is a cut state diagram of a fuse of the present invention.

FIG. 3 is a sectional view of the fuse in a cut state.

FIG. 4 is a fuse circuit diagram using the present invention.

FIG. 5 is a configuration diagram of a fuse of another embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional fuse.

[Explanation of symbols]

 101 AL wiring 102 Fuse 103 Contact 104 One terminal of fuse 105 One terminal of fuse 106 One terminal of fuse 107 One terminal of fuse

Claims (5)

[Claims] 1. A semiconductor device comprising a fuse having three or more terminals. 2. A fuse material is crossed in a fuse.
A semiconductor device having a fuse shape having terminals, wherein a disconnection voltage is applied between a pair of terminals to perform logical disconnection / non-disconnection determination between the other pair of terminals. 3. The fuse material is crossed in a fuse.
A semiconductor device having a fuse shape having a terminal, wherein the intersection is offset to one of the four terminals. 4. A fuse has a wiring metal that is connected to a fuse material, and the fuse material includes a portion that is connected to a wiring metal that applies a positive voltage when the fuse is cut and a wiring metal that applies a negative voltage. It has a connecting portion and a fuse portion for disconnecting, and the area for connecting to the wiring metal for applying the negative voltage is made larger than the area for connecting to the wiring metal for applying the positive voltage. Characteristic semiconductor device. 5. The fuse according to claim 4, wherein the size of the contact for connecting the wiring metal to which a negative voltage is applied and the connecting portion of the fuse is 6 μm × 4 μm or more, and the contact is perpendicular to the fuse portion. A semiconductor device having the shape of.