JP2002134616A - Method for cutting fuse and apparatus for cutting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for cutting a fuse where the fuse of a multilayer structure is certainly cut. SOLUTION: By irradiating a plurality of laser beams, which have more than one wave length, on the fuse 1 of the multilayer structure comprising a heating layer 2, a conductive layer 3, a barrier layer, etc., the fuse 1 is cut.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuse cutting method and a fuse cutting apparatus. For example, the present invention relates to a laser beam for cutting a fuse having a multilayer structure used for a redundant circuit or function switching with good reproducibility. The present invention relates to a fuse cutting method and a fuse cutting device which are characterized by irradiation conditions.

[0002]

2. Description of the Related Art With the recent progress in miniaturization and high integration of semiconductor integrated circuit devices, the influence of defective elements on the production yield cannot be ignored, and in particular, 64 Mbi.
A redundant configuration has been introduced in which a large-capacity LSI memory such as a tDRAM (dynamic random access memory) or a memory cell constituting a system LSI is provided with a plurality of spare rows and a plurality of spare columns in a memory cell.

In the case of replacing a row or a column containing a defective bit with a spare row or a spare column, or in the case of selecting a function, generally, a method of blowing a fuse made of Al, polycrystalline silicon, or the like with a laser, That is, the laser blow method is employed.

In such a laser blow method, generally, a laser pulse cutting device for a fuse having a laser of a single wavelength is used, and the fuse is cut by irradiating the fuse once with a laser pulse.

When a laser pulse is applied to the upper surface of the fuse, a sudden change in volume occurs when the fuse is heated and melted, and the fuse is coated with a protective film such as a SiO ₂ film by utilizing the change in volume. Exploded and was blown.

[0006]

However, in recent years, as fuses have been configured with a multilayer structure,
Irradiation with only a single-wavelength laser pulse has the problem that the fuse is not completely removed depending on the laser irradiation conditions, resulting in defective cutting.

That is, in recent years, a structure has been adopted in which a wiring layer is sequentially laminated with a barrier metal layer such as TiN, a conductive layer such as Al, and an antireflection film such as TiN. , The fuse is TiN / A
1 / TiN has a three-layer structure, but the TiN film as an antireflection film on the upper surface becomes a heat generating layer when a fuse is cut,
The heat generated by the light absorption in the heat generating layer is transferred to the conductive layer to melt the conductive layer, and blow using the rapid volume change accompanying the melting.

In this case, as a result of the melting simulation by the computer simulation, it was found that the heat generating layer was melted and removed in a short time after the laser pulse irradiation, and that the subsequently irradiated laser pulse was directly applied to the exposed conductive layer. did.

Conventionally, laser irradiation conditions such as a laser wavelength and a pulse width are set so that the heat generating layer below the cover film generates heat most efficiently, that is, the laser light is absorbed most efficiently in the heat generating layer. Because we have set conditions,
When the conductive layer is exposed as described above, the conductive layer having different heating conditions is irradiated with a laser pulse, so that the conductive layer does not efficiently generate heat, and there is a problem that a cutting failure occurs.

Accordingly, an object of the present invention is to reliably and reliably cut a fuse having a multilayer structure with good reproducibility.

[0011]

FIG. 1 is an explanatory view of the principle configuration of the present invention. Referring to FIG. 1, means for solving the problems in the present invention will be described. See FIG. 1 In order to achieve the above-mentioned object, in the present invention, a plurality of lasers having at least one wavelength different from others for a fuse 1 having a multilayer structure such as a heating layer 2 / a conductive layer 3 / a barrier layer 4. The fuse 1 is cut by irradiating light.

As described above, the wavelength of the laser beam applied to the fuse 1 used for switching the function of the redundant circuit or the semiconductor integrated circuit device is set to a suitable wavelength in accordance with the material constituting each layer of the multilayer fuse 1. Thereby, each layer can be completely cut.

In this case, the heat-generating layer 2 made of TiN, TaN, WN or the like has a cover made of at least one of an interlayer insulating film mainly composed of SiN and an interlayer insulating film mainly composed of SiO _2. By selecting the wavelength so that the absorptivity after passing through the film 5 becomes 60% or more, the heat generating layer 2 and a part of the conductive layer 3 thereunder are melted, and a sudden change in volume causes an extremely short time. Can be blown reliably.

For the conductive layer 3 made of Al, Cu, or an alloy containing one of them as a main component, when the absorption rate is Al-based, the absorption rate is 4.6% or more. In this case, by selecting the wavelength so as to be 2.7% or more, it is possible to completely cut the fuse 1 by vaporizing and evaporating the remaining portion of the conductive layer 3. In addition, TiN,
For the barrier layer 4 made of TaN, WN, or the like, the wavelength may be selected so that the absorptance is 60% or more.

When the fuse 1 cutting device is constructed, a plurality of lasers 6, 7, 8 oscillating at a suitable wavelength in accordance with the material constituting each layer of the multilayer fuse 1 are provided.
What is necessary is just to arrange so that an optical axis may be aligned on the same optical axis via optical elements 9 and 10, such as a prism type reflection mirror. When the material of the heat generating layer 2 and the material of the barrier layer 4 are the same, one laser may be used in common, or two same lasers may be used.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for cutting a fuse according to an embodiment of the present invention will now be described with reference to FIGS. FIG. 2 is a conceptual configuration diagram of a fuse cutting device used in the embodiment of the present invention, and shows three lasers 11, 13, and 15.
Are arranged via the two prism-type reflecting mirrors 17 and 18 so that the optical axes of the lasers 11, 13 and 15 coincide with each other, and are sequentially irradiated on the fuse 20. Laser for irradiation 11,1
Switching between 3 and 15 is performed.

In this case, as the laser 11 and the laser 15, a laser having a wavelength having a large absorptivity in the heating layer and the barrier layer may be used. For example, when the heating layer and the barrier layer are made of TiN, the absorption for TiN is used. A pulsed YAG laser having a wavelength of 1047 nm may be used so as to increase the rate.

The laser 13 is selected according to the material of the conductive layer.
When 1 is used, the wavelength is 827 nm (absorptivity 13.
2%), and when using Cu, a pulse laser having a wavelength of 413 nm (absorption rate 49%) may be used.

FIG. 3 is a schematic configuration diagram of the fuse 20 to be irradiated with the laser according to the embodiment of the present invention, which is shown as a cross-sectional view perpendicular to the longitudinal direction of the fuse. Fuse 20
Is provided on an interlayer insulating film 21 made of SiO _{2 serving as} a base and has a thickness of, for example, 10 nm.
2. An Al conductive layer 23 having a thickness of, for example, 780 nm, and a TiN heating layer 24 having a thickness of, for example, 10 nm.
This fuse 20 has a layer structure, and is covered with a cover film 25 having a multilayer structure such as a SiO ₂ film and a SiN film. In this case, the length of the fuse 20 is, for example, 20 μm, the width is 1.4 μm, and the thickness is 0.8 μm as described above.

The cover film 25 is a multi-layered insulating film formed in the process of forming the storage electrode portion of the memory cell and the peripheral circuit. In the laser irradiation window portion of the fuse,
The upper insulating film is removed, and usually, only the SiO ₂ film remains on the fuse in the laser irradiation window.

In this case, the SiO 2 covering the fuse 20
_TwoThe wavelength in the TiN heating layer 24 is 1 depending on the thickness of the film.
The absorptance (1-R) of 047 nm laser light is 27% to 7%.
Since it takes a value of 3%, SiO_TwoAbsorption after permeation through membrane of 6
SiO so that it becomes 0% or more _TwoControl the thickness of the film. What
Here, R is the reflectance.

4A, when the fuse 20 is blown with a laser, first,
With the shutters 14 and 16 closed, only the shutter 12 is opened, and a laser pulse having a wavelength of 1047 nm is emitted from the laser 11 at a total energy of, for example, 2.5 μJ. In this case, after laser irradiation, about 10 ns (nanosecond)
An explosion occurs later, and the TiN heating layer 24 and a part of the Al conductive layer 23 are removed together with the cover film 25.

FIG. 5 shows that when the fuse 20 is irradiated with a laser beam having an energy of 0.25 μJ to 2.5 μJ,
4 shows a change in the amount of melting when the Al conductive layer 23 is melted by generating heat and transferring the heat to the Al conductive layer 23. The amount of melting (μm ³ ) on the left vertical axis is the absolute amount of melting. And the melting amount (%) on the right vertical axis is 20 μm as described above.
The melting ratio to the volume of the fuse 20 of m × 1.4 μm × 0.8 μm (= 22.4 μm ³ ) is shown. As is clear from the figure, melting starts around 10 ns after laser irradiation, and the melting start time becomes shorter as the irradiation energy increases.

FIG. 6 is a diagram showing a pressure change due to a phase change of the molten portion of the Al conductive layer 23 of the fuse 20, and as shown in FIG. As a result, the pressure also rises sharply.

The strength of the SiO ₂ film constituting the cover film 25 is several GPa, for example, about 8 GPa.
When a laser beam having an energy of μJ is irradiated, the laser beam reaches 8 GPa in about 10 ns after the laser irradiation and explodes, that is, a laser blow occurs.

Referring to FIG. 4B, 10 ns after the irradiation of the laser 11, the shutter 12 is closed and the shutter 14 is opened.
The remaining portion of the exposed Al conductive layer 23 is irradiated with a pulsed laser beam of 27 nm to melt and vaporize Al and cut it.

When the laser beam of 1047 nm is applied to the Al conductive layer 23, the absorptance (1-R) in the Al conductive layer 23 is 4.6%, and the heat generation efficiency of the TiN heat generating layer 24 is 1%. / 16 to 1/6, but by irradiating a laser beam of 827 nm as in the present invention, A
The absorptivity in the 1-conducting layer 23 is 13.2%, which is about 3 times, and the heat generation of the Al-conducting layer 23 is also tripled, so that the Al-conducting layer 23 can be efficiently melted and vaporized.

Next, by closing the shutter 14 and opening the shutter 16, the wavelength of the laser 15 is 1047 nm.
By irradiating the exposed portion of the TiN barrier layer 22 with the pulsed laser light, the TiN barrier layer 22 is vaporized and cut.

As described above, in the embodiment of the present invention, the fuse 20 having the three-layer structure of the heat generating layer / the conductive layer / the barrier layer is provided with the heat generating layer, the conductive layer and the fuse.
Since the laser light having a wavelength having a good absorption rate in each layer of the barrier layer is irradiated, each layer can be cut efficiently and reliably, and no cutting failure occurs.

Next, a modification of the fuse cutting device will be described with reference to FIG. FIG. 7 is a conceptual configuration diagram of a modification of the fuse cutting device used in the embodiment of the present invention.
3 through a prism-type reflecting mirror 35 to each laser 3
The fuses 2 are arranged so that the optical axes of 1, 33 coincide with each other.
The lasers 31 and 33 are irradiated by shutters 32 and 34, respectively.

In this case, as the laser 31, a laser having a wavelength having a large absorption rate between the heating layer and the barrier layer may be used. For example, when the heating layer and the barrier layer are made of TiN, the absorption rate for TiN is large. A pulsed YAG laser having a wavelength of 1047 nm may be used. The laser 33 is selected according to the material of the conductive layer. For example, when Al is used as the conductive layer, a pulse having a wavelength of 827 nm is used. Use a laser.

Using this fuse cutting device, fuse 2
0, the TiN heating layer 24 and the Al conductive layer 2
3 and the TiN barrier layer 22
When cutting the Al conductive layer 23, the laser 31 is used.
Is melted and vaporized, the laser 33 is used.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations and conditions described in the embodiments, and various modifications are possible. For example,
In the above embodiment, the heat generation layer and the barrier layer are formed using the same TiN film. However, the heat generation layer and the barrier layer need not be the same, and different films may be used. May be constituted by a Ti layer. In this case, it is sufficient to use a laser having a favorable absorption rate in a barrier layer such as Ti as the laser 15 constituting the fuse cutting device in FIG.

The heat generating layer and the barrier layer are not limited to TiN, but may be nitrides such as TaN or WN, TiC,
A carbide such as TaC or WC or a single metal such as Ti, Ta or W may be used, and the wavelength of the laser beam may be selected according to the material to be used.

In the above embodiment, the conductive layer is made of Al. However, the conductive layer is not limited to Al, and may be made of an alloy containing Al as a main component. May be Cu having a lower specific resistance than Al and having high electromigration resistance, or an alloy containing Cu as a main component. Where Cu,
Alternatively, when an alloy containing Cu as a main component is used, C
In order to prevent the diffusion of u, it is desirable that the side surface of the conductive layer is also covered with the barrier layer.

The fuse to be cut is not limited to a fuse having a three-layer structure, but is also applicable to a fuse having a two-layer structure such as W silicide / polycrystalline silicon. What is necessary is just to select the laser of the wavelength with the favorable absorptivity in silicon, respectively.

Further, in the above embodiment, Ti
The wavelength of the laser used to cut the N film is 1047n.
m and the wavelength of the laser for cutting the Al layer is 827.
Although it is set to nm, it is needless to say that the wavelength is not strictly limited to these wavelengths, and a laser having a wavelength near these wavelengths may be used.

In FIG. 2, three lasers are used so as to correspond to a fuse having a three-layer structure.
As shown in FIG. 5, the laser layer may be composed of only two lasers. Even when the heat generation layer and the barrier layer are formed of different materials, the barrier layer is very thin at about 10 nm, so that a wavelength suitable for the heat generation layer is preferably used. Even if the laser is used, the barrier layer can be cut sufficiently reliably.

In the above embodiment, the laser is switched by using the shutter. However, the shutter is not always essential, and the laser is switched by electrically controlling the laser bias power supply. It is good to go.

The laser to be used is not necessarily a pulse laser, but a laser that oscillates continuously may be used.

The method of cutting a fuse according to the present invention comprises the steps of:
The present invention is not limited to application to connection / disconnection of a redundant circuit of a RAM, but is also applicable to connection / disconnection of a redundant circuit in a memory unit constituting a system LSI.

Further, the fuse cutting method of the present invention is not limited to application to connection / disconnection of a redundant circuit, but is also applicable to a case where a function is switched by a fuse in a general-purpose multifunctional semiconductor integrated circuit device. Things.

Here, the feature of the detailed configuration of the present invention will be described with reference to FIG. 1 again. FIG. 1 (Supplementary Note 1) A method of cutting a fuse, wherein the fuse 1 having a multilayer structure is cut by irradiating a plurality of laser beams having at least one wavelength different from others. (Supplementary Note 2) When the fuse 1 is moved from the laser irradiation surface side,
2. The method for cutting a fuse according to claim 1, wherein the heating layer 2, the conductive layer 3, and the barrier layer 4 have a multilayer structure in which they are sequentially stacked. (Supplementary Note 3) When irradiating the plurality of laser beams, first, a laser beam having a wavelength at which the absorptance in the heating layer 2 after passing through the cover film 5 covering the heating layer 2 is 60% or more is applied. 2. The method for cutting a fuse according to claim 2, wherein: (Supplementary Note 4) The method for cutting a fuse according to Supplementary Note 3, wherein the cover film 5 is made of at least one of an interlayer insulating film mainly composed of SiN and an interlayer insulating film mainly composed of SiO ₂ . (Supplementary Note 5) When irradiating the conductive layer 3 with a laser beam,
The conductive layer 3 is made of Al, an alloy mainly containing Al, Cu,
Alternatively, it is made of any of alloys containing Cu as a main component,
In the case of Al or an alloy containing Al as a main component, the absorptivity in the conductive layer 3 is set to be 4.6% or more. 5. The method for cutting a fuse according to claim 3 or 4, wherein the wavelength of the laser beam is selected so that the absorptance in the layer 3 is 2.7% or more. (Supplementary Note 6) The heating layer 2 and the barrier layer 4 are made of Ti, T
a, W, or Ti, Ta, W nitride or carbide, and the conductive layer 3
Are Al, an alloy containing Al as a main component, Cu, or C
The method for cutting a fuse according to any one of claims 2 to 5, wherein the fuse is made of any one of alloys mainly containing u. (Supplementary Note 7) In a fuse cutting device that cuts a fuse 1 having a multilayer structure, a plurality of lasers 6, 7, and 8 having a number corresponding to a material constituting each layer of the fuse 1 at most are provided by laser light from each of the lasers. Are arranged so as to be aligned on the same optical axis via the optical elements 9 and 10, and the wavelength of each of the lasers 6, 7 and 8 is set to a wavelength corresponding to the absorptance of the material constituting each layer of the fuse 1. A fuse cutting device, characterized in that: (Supplementary note 8) The supplementary note 7, wherein each of the laser lights is a pulsed laser light that is intermittently irradiated via a shutter, and the optical elements 9 and 10 are prism-type reflection mirrors. Fuse cutting device.

[0044]

According to the present invention, when a fuse having a multilayer structure is cut, a laser beam having a wavelength having a good absorptance is applied to each layer constituting the fuse. In addition, disconnection of redundant circuits and function switching can be reliably performed, which greatly contributes to improvement in the manufacturing yield of semiconductor integrated circuit devices.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is a conceptual configuration diagram of a fuse cutting device used in the embodiment of the present invention.

FIG. 3 is a conceptual configuration diagram of a fuse according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a fuse cutting step according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of irradiation energy dependence of a melting amount of an Al conductive layer in the embodiment of the present invention.

FIG. 6 is an explanatory diagram of a pressure change due to melting of an Al conductive layer in the embodiment of the present invention.

FIG. 7 is a conceptual configuration diagram of a modification of the fuse cutting device used in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuse 2 Heat generation layer 3 Conductive layer 4 Barrier layer 5 Cover film 6 Laser 7 Laser 8 Laser 9 Optical element 10 Optical element 11 Laser 12 Shutter 13 Laser 14 Shutter 15 Laser 16 Shutter 17 Prism type reflection mirror 18 Prism type reflection mirror 20 Fuse Reference Signs List 21 interlayer insulating film 22 TiN barrier layer 23 Al conductive layer 24 TiN heating layer 25 cover film 31 laser 32 shutter 33 laser 34 shutter 35 prism-type reflection mirror

Claims (5)

[Claims] 1. A method for cutting a fuse, comprising: irradiating a fuse having a multilayer structure with a plurality of laser beams having at least one wavelength different from the others to cut the fuse. 2. The method according to claim 1, wherein the fuse is provided from a laser irradiation surface side.
2. The method for cutting a fuse according to claim 1, wherein the fuse has a multilayer structure in which a heat generating layer, a conductive layer, and a barrier layer are sequentially stacked. 3. When irradiating the plurality of laser beams, first, irradiating the laser beam having a wavelength at which the absorptance in the heating layer after passing through the cover film covering the heating layer is 60% or more is performed. 3. The method of cutting a fuse according to claim 2, wherein: 4. When irradiating the conductive layer with a laser beam,
The conductive layer is Al, an alloy containing Al as a main component, Cu,
Alternatively, it is made of any of alloys containing Cu as a main component,
In the case of Al or an alloy containing Al as a main component, the absorptivity in the conductive layer is set to be 4.6% or more. 4. The method for cutting a fuse according to claim 3, wherein the wavelength of the laser beam is selected so that the absorptance of the laser beam becomes 2.7% or more. 5. A fuse cutting device for cutting a fuse having a multi-layer structure, wherein a maximum number of lasers corresponding to a material constituting each layer of the fuse are supplied by a laser beam from each laser via an optical element. A fuse cutting device which is arranged so as to be aligned on the same optical axis, and wherein the wavelength of each laser is a wavelength corresponding to the absorptivity of a material constituting each layer of the fuse.