JPH08330430A - Anti-fusing element and its manufacture - Google Patents

Abstract

PURPOSE: To obtain a good programming characteristic and provide a highly reliable anti-fusing element and its manufacturing method, by reducing the variations in the breakdown voltage of an anti-fusing layer. CONSTITUTION: An anti-fusing element comprises a first wiring 12 made of aluminum or an aluminum compound, an interlayer insulation film 13 formed on the first wiring 12, a connection hole 17 formed in the interlayer insulation film 13 which reaches the first wiring 12, an aluminum fluoride anti-fusing layer 14 formed in the bottom portion of the connection hole 17, a tungsten 15 filled into the connection hole 17 on the anti-fusing layer 14, and a second wiring 16 formed on both the tungsten 15 and the interlayer insulation film 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifuse element used in a semiconductor integrated circuit and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, as a prototype of a gate array or its substitute, the logic which can be programmed at hand has been developed.
PGA (Field-Programmable Gate Array) is used. In the antifuse method, which is the main programming method of FPGA, in order to achieve high speed and high integration,
The anti-fuse element has been developed as a structure sandwiched between metal wires as an alternative to the structure sandwiched between polycrystalline silicon and a silicon substrate.

The anti-fuse element is normally in a high resistance state and changes to a low resistance state by an electric programming signal. Here, in the case of an antifuse having a structure sandwiched between metal wirings, the thickness of the antifuse layer is not formed because the antifuse layer is formed in the connection hole after forming the connection hole between the lower wiring and the upper wiring. Had a problem of uniformity. Therefore, there has been proposed a method of forming an anti-fuse layer before forming the contact hole and then forming the contact hole (see Japanese Patent Application No. 3-275816).

A conventional anti-fuse element will be described below with reference to the drawings. FIG. 3 is a sectional view showing a conventional antifuse element. 1 is an insulating substrate, 2 is a first wiring made of an aluminum alloy, 3 is an anti-fuse layer, 4 is an interlayer insulating film, 5 is a recess of the anti-fuse layer generated when a connection hole is opened, 6 is tungsten, and 7 is The second wiring is made of an aluminum alloy. The operation of the antifuse element having the above structure will be described below.

The antifuse element normally insulates between the first wiring 2 and the second wiring 7 via the antifuse layer 3. Here, when forming a circuit including the first wiring 2 and the second wiring 7 electrically insulated by the anti-fuse layer 3, first, the first wiring 2 and the second wiring 7 are electrically insulated. External programming signals. A voltage is applied between the first wiring 2 and the second wiring 7 through the anti-fuse layer 3 by the programming signal provided from the outside. When the critical value of the voltage applied between the first wiring 2 and the second wiring 7 is established through the antifuse layer 3, the antifuse layer 3 causes a dielectric breakdown. As a result, the resistance between the first wiring 2 and the second wiring 7 becomes low, and a new circuit including the first wiring 2 and the second wiring 7 is formed.

A method of manufacturing the conventional antifuse element shown in FIG. 3 will be described below. 4A to 4F are process cross-sectional views showing the manufacturing process of the conventional antifuse element. 1 is an insulating substrate, 2 is an aluminum alloy first
Wiring, 3 is an anti-fuse layer, 4 is an interlayer insulating film, 5 is a recess of the anti-fuse layer generated when a connection hole is opened,
6 is tungsten and 7 is an aluminum alloy second
Wiring, 8 is a conductive film made of an aluminum alloy, 9 is an anti-fuse film, and 10 is a connection hole.

First, a conductive film 8 made of an aluminum alloy is deposited on the insulating substrate 1 by a sputtering method, and then an antifuse film 9 is deposited (FIG. 4A). Next, masking with a photoresist and dry etching are performed to form the first wiring 2 and antifuse layer 3 made of an aluminum alloy (FIG. 4B).

Next, an interlayer insulating film 4 is formed by depositing an insulating film on the first wiring 2 and the antifuse layer 3 by a plasma CVD method and then flattening it by a resist etch back method (FIG. 4C). ). Next, the interlayer insulating film 4 is masked with a photoresist and dry-etched to open a connection hole 10 for forming an anti-fuse element and expose the anti-fuse layer 3. The etching at this time causes a recess 5 in the antifuse layer 3 (FIG. 4D).

Next, the connection hole 1 on the antifuse layer 5
Only 0 is filled with tungsten by the selective CVD method (FIG. 4E). Then, an aluminum alloy is deposited by a sputtering method, and the antifuse layer is covered by masking and dry etching with a photoresist.
The wiring 7 is formed (FIG. 4F).

[0010]

However, in the conventional anti-fuse element as described above, the thickness of the anti-fuse layer 3 is thin due to the formation of the depression 5 in the anti-fuse layer 3 when the connection hole 10 is formed. In addition, there is a problem that the depth of the recess 5 of the anti-fuse layer 3 is different for each connection hole due to the variation in the film thickness of the interlayer insulating film 4. Here, since the electric field that causes the dielectric breakdown of the antifuse layer 3 mainly depends on the film thickness of the antifuse layer 3, the thinning or variation of the thickness of the antifuse layer directly causes the variation of the dielectric breakdown voltage of the antifuse layer 3. Becomes Therefore, when the anti-fuse element is used as the program element of the FPGA, the variation in the dielectric breakdown voltage of the anti-fuse layer 3 becomes a serious problem in programming and reliability.

The present invention solves the above-mentioned conventional problems, and provides an antifuse element having a uniform film thickness of an insulator used as an antifuse layer, and a method of manufacturing the same.

[0012]

An antifuse element according to claim 1 has a first wiring made of aluminum or an aluminum compound, an interlayer insulating film formed on the first wiring, and an interlayer insulating film. The formed connection hole reaching the first wiring, the antifuse layer made of aluminum fluoride formed at the bottom of the connection hole, the metal filled on the antifuse layer, the metal and the interlayer insulating film And a second wiring formed on the above.

According to another aspect of the antifuse element of the present invention, a first wiring made of titanium or a titanium compound, an interlayer insulating film formed on the first wiring, and a first wiring formed on the interlayer insulating film. And the connection hole reaching
The antifuse layer made of titanium fluoride is formed on the bottom of the connection hole, the metal filled on the antifuse layer, and the second wiring formed on the metal and the interlayer insulating film. .

A method of manufacturing an anti-fuse element according to a third aspect of the present invention comprises the steps of depositing a conductive film made of aluminum or an aluminum compound and patterning it to form a first wiring, and forming an interlayer insulating film on the first wiring. A step of forming, a step of patterning the interlayer insulating film to form a connection hole, and exposing a part of the first wiring at the bottom of the connection hole,
A step of forming aluminum fluoride by a chemical reaction between a metal fluoride gas and aluminum at the bottom of the connection hole to form an antifuse layer; a step of filling a metal on the antifuse layer; and a metal and interlayer insulating film A step of depositing a conductive film thereon and patterning it to form a second wiring.

According to a fourth aspect of the present invention, there is provided a method of manufacturing an anti-fuse element, which comprises a step of depositing a conductive film made of titanium or a titanium compound and patterning it to form a first wiring, and an interlayer insulating film on the first wiring. A step of forming, a step of forming a connection hole by patterning the interlayer insulating film to expose a part of the first wiring at the bottom of the connection hole, and a step of chemistry of metal fluoride gas and titanium at the bottom of the connection hole. A step of forming titanium fluoride by reaction to form an antifuse layer; a step of filling a metal on the antifuse layer; and a step of depositing and patterning a conductive film on the metal and the interlayer insulating film to form a second film. And a step of forming wiring.

A method for manufacturing an antifuse element according to a fifth aspect is the method for manufacturing an antifuse element according to the third or fourth aspect, wherein the step of forming the antifuse layer is performed using a metal fluoride gas and a reducing gas. Flow ratio 1 or more,
CV under conditions where temperature is below 300 ° C and pressure is above 1 mTorr
This is performed by the D method.

[0017]

According to the present invention, since the anti-fuse layer is formed at the bottom of the connection hole, the thickness of the anti-fuse layer becomes uniform, and the variation in the dielectric breakdown voltage of the anti-fuse layer can be reduced, which is excellent. The programming characteristics can be obtained. Further, since the antifuse layer is formed only by the bottom of the connection hole by the chemical reaction between the metal fluoride gas and the first wiring, it is not necessary to pattern the antifuse layer.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An antifuse element according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a sectional structure of an antifuse element according to an embodiment of the present invention. 11 is an insulating substrate, 12 is a first wiring made of an aluminum alloy, 13 is an interlayer insulating film, 14 is an antifuse layer made of aluminum fluoride, 15 is tungsten, 16 is a second wiring made of an aluminum alloy, and 17 is It is a connection hole.

As described above, in this antifuse element, the antifuse layer 14 made of aluminum fluoride having a uniform film thickness is formed only on the bottoms of the connection holes 17 of the first wiring 12 and the second wiring 16. Therefore, it is possible to eliminate the variation in the dielectric breakdown voltage during programming due to the variation in the film thickness of the anti-fuse layer 14, and it is possible to obtain good programming characteristics. Further, since the connection hole 17 on the antifuse layer 15 is filled with tungsten, a highly reliable antifuse element having no problem of reliability failure due to thinning of the second wiring in the connection hole 17 is formed. Can be realized.

Next, a method of manufacturing the antifuse element of this embodiment will be described. 2A to 2F are process cross-sectional views showing a manufacturing method according to an embodiment of the present invention, in which 11 is an insulating substrate, 12 is a first wiring made of an aluminum alloy, 13 is an interlayer insulating film, and 14 is an insulating film. Is an antifuse layer made of aluminum fluoride, 15 is tungsten, 16 is a second wiring made of an aluminum alloy, and 17 is a connection hole.

First, an aluminum alloy is deposited on the insulating substrate 11 by a sputtering method, masked with a photoresist, and then dry-etched.
The wiring 12 is formed (FIG. 2A). Next, an insulating film is formed on the insulating substrate 11 by the plasma CVD method and a flattening process using the resist etch back method is performed to form the interlayer insulating film 13 (FIG. 2B).

Next, the connection hole 17 is formed by masking with a photoresist and dry etching (FIG. 2C). Next, a CVD process using tungsten hexafluoride gas which is a metal fluoride gas and silane gas which is a reducing gas is performed, and a flow rate ratio of tungsten hexafluoride and silane gas (the flow rate of tungsten hexafluoride is a molecule, the flow rate of silane gas is The antifuse layer 14 is formed under the condition that the flow rate ratio with denominator is WF ₆ / SiH ₄ ) is 1 or more, the temperature is 300 ° C. or less, and the pressure is 1 mTorr or more. As a result, the tungsten hexafluoride gas reacts with the aluminum of the first wiring to selectively form aluminum trifluoride only on the bottom of the connection hole 17 (FIG. 2D).

When the gas flow rate ratio is less than 1, the reaction between tungsten hexafluoride and aluminum is inhibited, the formation rate of aluminum trifluoride becomes slow, the temperature exceeds 300 ° C., and the pressure is increased. When it is less than 1 mTorr, the formed aluminum trifluoride easily sublimes, and it becomes difficult to form a good antifuse layer. Therefore, it is necessary to process under the above CVD conditions.

Next, a tungsten film is formed only inside the connection hole 17 with the same gas system, and the connection hole 17 is filled with tungsten 1.
Embed with 5. At this time, the CVD conditions may be the same as those for forming the antifuse layer, or even if the conditions are different, there is no problem as long as the tungsten selectivity can be maintained (FIG. 2 (e)). Finally, an aluminum alloy is deposited by the sputtering method, masked with a photoresist, and then the second wiring 16 is formed by dry etching (FIG. 2).
(F)).

Although the first wiring is made of aluminum alloy in this embodiment, the same effect can be obtained even if titanium alloy is used because titanium tetrafluoride is formed by the reaction with the metal fluoride gas. To be Even when the aluminum alloy or titanium alloy is not a single layer or is laminated with another material, the same effect can be obtained if the portion exposed to the connection hole as the first wiring is an alloy containing aluminum or titanium. . Further, although tungsten hexafluoride is used in the examples, a metal fluoride gas (for example, a metal fluoride gas that is more easily dissociated than aluminum trifluoride or titanium tetrafluoride (for example,
The same effect can be obtained by using MoF ₆ ). Also,
Silane was used in the examples, but a reducing gas (H ₂ ,
Similar effects can be obtained by using Si _n H _{2n + 2} silane-based gas, SiH ₂ F _2, etc.).

[0026]

According to the present invention, since the film thickness of the antifuse layer is uniform, variations in the dielectric breakdown voltage of the antifuse layer can be reduced, and good programming characteristics can be obtained. Further, since the connection hole is filled with metal, it is possible to avoid a decrease in reliability due to the thinning of the anti-fuse layer inside the connection hole of the second wiring. Furthermore, since the anti-fuse layer is formed only by the bottom of the connection hole by the chemical reaction between the metal fluoride gas and the first wiring, it is not necessary to pattern the anti-fuse layer and the manufacturing is easy.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of an anti-fuse element according to an embodiment of the present invention.

FIG. 2 is a process sectional view of a method for manufacturing an antifuse element according to an embodiment of the present invention.

FIG. 3 is a structural cross-sectional view of a conventional antifuse element.

FIG. 4 is a process sectional view of a conventional method for manufacturing an anti-fuse element.

[Explanation of symbols]

 1,11 Insulating substrate 2,12 First wiring 3,14 Antifuse layer 4,13 Interlayer insulating film 5 Antifuse layer recess 6,15 Tungsten 7,16 Second wiring 8 Conductive film 9 Antifuse film 10, 17 Connection hole

Claims (5)

[Claims] 1. A first wiring made of aluminum or an aluminum compound, an interlayer insulating film formed on the first wiring, and a connection hole formed in the interlayer insulating film and reaching the first wiring. An antifuse layer made of aluminum fluoride formed at the bottom of the connection hole, a metal filled on the antifuse layer, and a second wiring formed on the metal and the interlayer insulating film. Antifuse element. 2. A first wiring made of titanium or a titanium compound, an interlayer insulating film formed on the first wiring, and a connection hole formed in the interlayer insulating film and reaching the first wiring. An antifuse layer made of titanium fluoride formed at the bottom of the connection hole, a metal filled on the antifuse layer, and a second wiring formed on the metal and the interlayer insulating film. Antifuse element. 3. A step of depositing and patterning a conductive film made of aluminum or an aluminum compound to form a first wiring, a step of forming an interlayer insulating film on the first wiring, and a step of forming the interlayer insulating film. Patterning to form a connection hole and exposing a part of the first wiring at the bottom of the connection hole; and aluminum fluoride generated at the bottom of the connection hole by a chemical reaction between a metal fluoride gas and aluminum. Forming an anti-fuse layer, filling a metal on the anti-fuse layer, and depositing a conductive film on the metal and the interlayer insulating film and patterning to form a second wiring. A method of manufacturing an anti-fuse element including the steps of :. 4. A step of depositing and patterning a conductive film made of titanium or a titanium compound to form a first wiring, a step of forming an interlayer insulating film on the first wiring, and a step of forming the interlayer insulating film. Patterning to form a contact hole and exposing a part of the first wiring at the bottom of the contact hole; and generating titanium fluoride at the bottom of the contact hole by a chemical reaction between metal fluoride gas and titanium. Forming an anti-fuse layer, filling a metal on the anti-fuse layer, and depositing a conductive film on the metal and the interlayer insulating film and patterning to form a second wiring. A method of manufacturing an anti-fuse element including the steps of :. 5. The step of forming the anti-fuse layer comprises forming a metal fluoride gas and a reducing gas at a flow rate ratio of 1 or more and at a temperature of 300.
The method for producing an anti-fuse element according to claim 3 or 4, which is performed by a CVD method under conditions of a temperature of not more than 0 ° C and a pressure of not less than 1 mTorr.