JPH05190542A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve a stress migration resistance and an electro-migration resistance by a method wherein the surface of an insulating film is smoothened and after a highly orientated layer is formed on the insulating film, a metal film is formed on this highly orientated layer or the surface of the highly orientated layer is smoothened and a metal film is formed on the highly orientated layer. CONSTITUTION:A BPSG film is formed on an Si substrate 11 by a CVD method as an insulating film 12 and thereafter, the surface of the film 12 is subjected to smoothing treatment by a chemical polishing method. Then, a Ti film 13 and a TiN film 14, which are a highly orientated layer, are formed in order on the film 12 by sputtering. The surface of the film 14 is smoothened by a chemical polishing method. Moreover, an Al alloy film 15 is formed on the film 14 by sputtering, the films 15, 14 and 13 are etched and a wiring pattern is formed. Thereby, the orientation property of the highly orientated film is improved, the life of a metal wiring formed of this highly orientated film is prolonged and a wiring having a superior reliability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a semiconductor device,
In particular, it relates to a method for forming electrode wiring.

[0002]

2. Description of the Related Art Al has been used as a material for electrode wiring of LSI until now.
Al alloys containing Al as the main component have been widely used.
With the miniaturization of I, the wiring width and wiring film thickness have been reduced,
There is a problem that the reliability of wiring is lowered.

The electromigration phenomenon and the stress migration phenomenon are considered as the causes of the decrease in the reliability of the wiring. Electromigration is a phenomenon in which electrons flowing in a wiring collide with Al atoms and Al atoms move, and stress migration is a phenomenon in which Al atoms are moved by mechanical stress from another material used for LSI. Recent studies have revealed it.

In order to solve the problem of the decrease in the reliability of the wiring, controlling the crystallinity of the Al wiring has been studied. Al has a face-centered cubic structure, and its interface energy is the smallest in the (lll) plane. Therefore, when the Al film is formed by the sputtering method or the like, there is a tendency that the main orientation is (lll) so that the energy at the interface is minimized. When the Al film exhibits the (lll) orientation, the electromigration resistance and the stress migration resistance of the Al wiring are improved, and the reliability of the wiring is improved. A
The reason why l shows the (llll) orientation increases the resistance to each migration is considered as follows. As described above, since the interface energy of the (lll) plane of Al is small, when the Al wiring is broken, the fracture surface is (l).
11) surface. Therefore, when the Al film is (lll) oriented from the underlying substrate, the cross section cut at right angles to the wiring length direction does not become the (lll) plane, and the wiring is hard to break. That is, as the (lll) orientation is stronger, the slit-shaped voids are less likely to occur.

In the current wiring manufacturing process, a barrier metal film is formed on the base insulating film before forming the Al film in order to prevent reaction and diffusion between the Al film and the substrate surface. At this time, by selecting a material for the barrier metal film that prevents reaction and diffusion between the Al film and the underlying substrate, has a close atomic distance to the Al film, and has (lll) orientation on the underlying insulating film, the upper Al film (Lll) Orientation is improved. Hereinafter, such a film is referred to as a highly oriented layer. For example, a metal laminated film such as TiN / Ti can be considered as the highly oriented layer. When Ti is formed on the surface of the substrate, Ti is a material that easily forms the closest packed surface (002) and has a dense hexagonal lattice structure. The upper TiN has a NaCl type crystal structure, and its (ll) plane has a close atomic spacing to the densest plane of Ti, so that the TiN film on Ti is likely to be (lll) oriented. Furthermore, since the atomic spacing between the (ll) plane of Al and the TiN (lll) plane is close, the TiN / Ti laminated film can be used as a highly oriented layer for orienting Al (ll).

Therefore, forming such a metal film having a close atomic distance to the Al film and having a high (111) orientation is effective in improving the Al (111) orientation and the reliability of the electrode wiring. It can be said that it is an effective means to make.

However, a TiN film or the like formed by the sputtering method or the like has minute irregularities due to crystal grains on its surface, and a crystal plane inclined with respect to the substrate surface appears (FIG. 8). It has been found that the Al crystal grains on the highly oriented layer having the inclined surface cannot form the (lll) axis perpendicular to the substrate surface and deteriorate the reliability of the wiring. In addition, minute unevenness of the base insulating film and (ll of the Al film
It was found that there is also a close relationship with l) orientation.

[0008]

As described above, the present inventors have found that the unevenness present on the surface of the highly oriented layer which is the base film of the Al wiring or the surface of the insulating film which is the lower layer of the highly oriented layer has (11
l) A problem has been found that it becomes a factor that deteriorates the orientation, and also causes a disconnection of wiring.

The present invention has been made in consideration of the above circumstances, and an object thereof is to form an electrode wiring having excellent resistance to stress migration and electromigration.

[0010]

In order to solve the above problems, in the present invention, the surface of an insulating film is smoothed, a highly oriented layer is formed thereon, and then a metal film is formed on the highly oriented layer. Or and / or smoothing the surface of the highly oriented layer, and forming a metal film thereon. As a method for smoothing the surface of the insulating film and the surface of the highly oriented layer, a polishing method, an etching method using a halogen radical, or the like can be used.

[0011]

When the surface of the insulating film is smoothed, the (lll) orientation of the highly oriented layer on the insulating film is improved, and as a result, an Al film having a high (lll) orientation is formed, and the reliability of the electrode wiring is improved. To do. Further, if the surface of the highly oriented layer is also smoothed in addition to the smoothing of the insulating film, the (ll) orientation of the upper Al layer is further improved, and a more reliable electrode wiring can be obtained.

First of the insulating film surface and the highly oriented layer surface
The smoothing method is a polishing method, and for example, chemical polishing with a chemical etching action can be used. Chemical polishing is a method for polishing while chemically etching a substrate using an etching solution containing polishing particles. The cut part of the substrate surface mechanically polished has an acute angle, but by chemical etching, the acute-angled cut part is etched in a direction to reduce the surface area, and simultaneous progress of these two etching results in smoothing at the atomic level. Contribute.

The second of the insulating film surface and the highly oriented layer surface
The method of smoothing is to expose the insulating film to halogen radicals such as fluorine, which causes etching and deposition of etching products on the surface of the insulating film. When deposits are deposited on the surface of a substrate having irregularities, they tend to deposit in the recesses in the initial process, and the deposits selectively deposited in the recesses act as a mask for etching and the protrusions selectively etch. This enables smoothing at the atomic level.

[0014]

EXAMPLES The details of the present invention will be described below with reference to examples. FIG. 1 is an explanatory view showing a method for forming electrode wiring including a step of smoothing an insulating film and a highly oriented layer.

First, B as an insulating film 12 is formed on the Si substrate 11.
The PSG film was formed by the CVD method to a thickness of 7,000 Å. This BPSG film formation was performed at a normal pressure of 600 ° C. Next, a smoothing process was performed by the chemical polishing method (FIG. 1A).

FIG. 2 shows a top view of the polishing apparatus.
The wafer moves from the loading unit 21 to the polishing unit 23, where polishing is performed and when the polishing is completed, the wafer is moved to the brush washing unit 22 where the polishing liquid and polishing debris adhering to the wafer are washed, and finally Arrives at the unloading section 24. FIG. 3A shows the structure of the polishing section in the polishing apparatus, and FIG. 3B shows the polishing mechanism. In the polishing part of FIG. 3A, the wafer 33 set on the top ring 32 is rotated on the turntable 35, and the polishing liquid is supplied through the polishing liquid supply pipe 34 during polishing on the turntable. Liquid continues to be supplied. When polishing is completed and the wafer moves to the brush water washing unit 22 of FIG. 2, the polishing unit flushes the old polishing liquid on the turntable, so pure water is supplied from the pure water supply pipe 31.

The polishing mechanism is shown in FIG.
As shown in (b), the unevenness of the wafer surface is mechanically scraped by the fine porous polyurethane cloth 37 and the polishing particles 36, and is chemically etched by the polishing liquid. By the action, smoothing at the atomic level is possible. This time, N as a polishing liquid
An alkaline aqueous solution containing aOH as a main component was used, and colloidal SiO ₂ was used as abrasive particles.

Next, as shown in FIG. 1B, the insulating film 12
A Ti film 13 having a thickness of 200 Å and a TiN film 14 having a thickness of 500 Å were sequentially formed thereon by a sputtering method. The sputtering conditions for forming the Ti film are Ar atmosphere 10 ⁻³ Torr, and the sputtering conditions for forming the TiN film are mixed atmosphere of Ar and N ₂ (1:
1), 10 ⁻³ Torr, and DC sputtering was performed. The Ti film and the TiN film are highly oriented layers.
Then, the surface of the TiN film 14 is smoothed as shown in FIG. The smoothing treatment at this time was performed by the chemical polishing method similarly to the smoothing of the insulating film. Then, as shown in FIG.

On the TiN film 14 by sputtering,
The Al alloy film (Al-Si-Cu) 15 is formed to a thickness of 8000 angstroms, and Al is formed as shown in FIG.
The alloy film 15, the TiN film 14, and the Ti film 13 were etched to form a wiring pattern.

The method described above smoothes the insulating film and the highly oriented layer. However, even when only the insulating film is smoothed, compared with the conventional case where the insulating film is not smoothed. It is known that the reliability of the finished electrode wiring is improved. However, the reliability improving effect of the electrode wiring changes depending on the smoothing method of the insulating film. FIG. 4 is a diagram showing the average surface roughness of the insulating film surface when the insulating film surface is smoothed by various smoothing methods shown on the horizontal axis. The average surface roughness is 10 in the conventional methods such as the reflow method, the reflow CVD (reflow during CVD), the bias sputtering method, the resist etch back method, etc.
It can be seen that the average surface roughness is about 5 Å when the chemical polishing method, which is the method used in the present embodiment, is used, whereas the average surface roughness is about 5 Å or more. In FIG. 5, a TiN / Ti highly oriented layer is provided on a base insulating film under different conditions, and Al-Si-Cu is formed on the layer by 800.
This is the result of evaluating the orientation of the Al film in the sample formed to a thickness of 0 angstrom by the X-ray diffraction method (note that FIG. 5 does not smooth TiN). Here, the rocking curve full width at half maximum and the XRD (θ-2θ) measurement strength, which are criteria for knowing the crystallinity of the sample, were used as evaluation quantities. The rocking curve half-width is small, and XRD (θ
It can be said that the higher the measured intensity is, the stronger the (lll) orientation of the Al film becomes.

As shown in FIG. 5, the underlying insulating film is asdepo-BP.
Compared with the case of SG (no planarization), melT-BPSG (planarization by reflow method), and t-SiO ₂ (Si substrate is oxidized by BOX, that is, combustion oxidation at 950 °), the underlying insulating film is smoothed by polishing. In the case of BPSG, it can be seen that the (lll) orientation of the upper Al layer is significantly improved.

That is, when the average surface roughness of the insulating film surface is reduced to some extent, T formed on the upper layer through the Ti film is increased.
The (lll) orientation of the iN film is improved, and the crystal information of the TiN film is transmitted to the Al film formed on the iN film,
There is an effect that the (lll) orientation of the Al film is improved. As a result of earnest studies, it has been found that the average surface roughness of the insulating film surface is desirably 8 angstroms or less in order to obtain a highly reliable electrode wiring. As a smoothing method for obtaining such a level of average surface roughness,
In addition to the chemical polishing method described above, there is also a smoothing method by etching using radicals of halogen atoms.

When the insulating film and the highly oriented layer were smoothed by this method, the same smoothness of the film as that obtained by the chemical polishing method was obtained. The smoothing treatment of the insulating film using halogen radicals was performed under the following conditions. As a device, a chemical dry etching device (CDE) is used, and a mixed gas of CF ₄ gas and O ₂ gas is 100 S each.
It was introduced into the chamber in which the wafer was set at a flow rate of CCM and 250 SCCM through the microwave discharge part. The internal pressure in the chamber was set to 0.9 Torr, and the gas was exhausted to 0.01 Torr or less before introducing the gas. CF ₄ and O ₂ introduced into the microwave discharge part away from the chamber
Long-lived radicals of fluorine atoms are generated from the gas.
The input power of microwave discharge was 600W.

The surface of the highly oriented layer (TiN film) was smoothed under the following conditions. That is, similarly, a CDE device is used to supply CF ₄ gas and O ₂ gas at 150 SCCM and 3 respectively.
It was introduced at a flow rate of 00 SCCM. Chamber pressure is 1T
The pressure was set to orr, and the gas was evacuated to 0.01 Torr or less before gas introduction. The microwave input power was 600W.

The above-described smoothing method and the chemical polishing method have the same smoothing effect. One of the insulating film and the highly oriented layer may be smoothed by the above etching, and the other may be chemically polished. ..

Next, FIG. 6 shows the results of evaluating the orientation of the Al film by the X-ray diffraction method with and without the smoothing treatment of the insulating film surface and the TiN film surface. FIG. 6 shows the result of performing smoothing by chemical polishing. Compared to the conventional example in which the surface of the insulating film and the surface of the TiN film are not smoothed, the one having the smoothed insulating film surface has improved (ll) orientation of Al. In addition to smoothing the surface of the insulating film, the TiN film surface is also smoothed. It can be seen that the (lll) orientation of Al is further improved in the case of smoothing.

Further, FIG. 7 shows the evaluation results of the reliability characteristics of the wiring with and without the smoothing treatment of the insulating film surface and the TiN film surface. Similar to FIG. 6, FIG. 7 also shows smoothing by the chemical polishing method. In FIG. 7, the vertical axis represents the cumulative defective rate and the horizontal axis represents the disconnection time. Sample A is a conventional one in which the insulating film and TiN film are not smoothed, Sample B is one in which only the insulating film is smoothed, Sample C is one in which the insulating film and TiN film are smoothed, The wiring of a plurality of chips in each sample was evaluated, and the relationship between the cumulative defective rate and the disconnection time was plotted on a log-normal probability paper. The closer the curve is to the vertical, the smaller the variation in the wiring performance of each chip, and the closer the curve is to the right, the longer the disconnection time. In other words, there are few curve tails, the closer to the vertical and to the right,
It can be said that the reliability of the electrode wiring is high.

From FIG. 7, sample C, sample B and sample A satisfy the above conditions in this order, and the insulating film and Ti
As compared with the conventional method in which the N film surface is not smoothed, the one having the smoothed insulating film surface has higher wiring reliability, and the one having the smoothed insulating film surface and the TiN film surface has higher reliability. Recognize.

It has been described above that the smoothing of the insulating film or the smoothing of the insulating film and the highly oriented layer improves the (ll) orientation of the upper Al, but only the highly oriented layer is smoothed. It has been found that the (lll) orientation of Al is improved as compared with the conventional method even if the conversion is performed. As a smoothing method for the highly oriented layer, there are the chemical polishing method and the etching method using halogen radicals as described above. The highly oriented layer may be made of a material other than TiN / Ti, and the metal wiring material is not limited to Al.

Further, in the above embodiments, an experiment was described in which an insulating film was formed on a Si substrate, the insulating film was smoothed by a chemical polishing method or etching, and a highly oriented layer and a metal wiring layer were sequentially formed. In the actual manufacturing, the insulating film may be temporarily flattened and then the smoothing process described above may be performed. For example, on a Si substrate on which elements such as MOS transistors are formed, a BPSG film is deposited by CVD on these substrates having irregularities due to element formation, and then heated and reflowed to be substantially flat. The surface of the BPSG film may be further smoothed by the above chemical polishing or etching. This heat treatment for reflow causes the water content in the BPSG film to be discharged. The BPSG film may be formed by a reflow CVD method instead of the reflow after the formation of the BPSG film.

[0031]

As described above, according to the present invention,
Since the underlying insulating film is smoothed before forming the wiring metal film, the orientation of the highly oriented film is improved, and crystal information is also transmitted to the metal film formed on this film so that the highly oriented film is formed. Is obtained. Also, by smoothing the surface of the highly oriented film, a highly oriented metal film can be obtained. Therefore, the metal wiring formed in this way has a longer wiring life than the conventional one, and a highly reliable wiring can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of an electrode wiring according to an embodiment of the present invention.

FIG. 2 is a top view of a polishing device.

FIG. 3 is a diagram showing a polishing section (a) and a polishing mechanism (b) in the polishing apparatus.

FIG. 4 is a diagram comparing average surface roughness of insulating films smoothed by various smoothing methods.

FIG. 5 is a diagram showing evaluation results of Al films formed on various insulating films by an X-ray diffraction method.

FIG. 6 Al formed by the method of the present invention and a conventional method
The figure which shows the evaluation result of the film | membrane by the X-ray diffraction method.

FIG. 7 is a diagram showing reliability characteristics of wiring formed by the method of the present invention and the conventional method.

FIG. 8 is a schematic diagram showing the crystal grain structure of TiN immediately after sputtering.

[Explanation of symbols]

 11 Si substrate 12 Insulating film 13 Ti 14 TiN 15 Al 21 Loading part 22 Brush water washing part 23 Polishing part 24 Unloading part 31 Pure water supply pipe 32 Top ring 33 Wafer 34 Polishing liquid supply pipe 35 Turntable 36 Polishing particles 37 Cross 81 Insulating film 82 TiN crystal grains

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuo Hayasaka No. 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside the Toshiba Research Institute, Inc. (72) Inventor Kyoichi Sukuro Komukai-cho, Kozaki-ku, Kawasaki-shi, Kanagawa No. 1 Incorporated company Toshiba Research Institute

Claims (10)

[Claims] 1. A step of forming an insulating film on a semiconductor substrate, a step of smoothing the insulating film, a step of forming a highly oriented layer on the insulating film, and a step of smoothing the highly oriented layer. And a step of forming a metal film on the highly oriented layer, the method of manufacturing a semiconductor device. 2. A step of forming an insulating film on a semiconductor substrate, a step of smoothing the insulating film so that the average surface roughness is 8 angstroms or less, and a highly oriented layer formed on the insulating film. And a step of forming a metal film on the highly oriented layer, the method of manufacturing a semiconductor device. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the insulating film is smoothed by polishing. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the insulating film is smoothed by exposing the insulating film to radicals of halogen atoms. 5. A step of forming an insulating film on a semiconductor substrate, a step of forming a highly oriented layer on the insulating film, a step of smoothing the highly oriented layer, and a step of forming a highly oriented layer on the highly oriented layer. And a step of forming a metal film thereon. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the highly oriented layer is smoothed by polishing. 7. The high orientation layer is smoothed by exposing it to radicals of halogen atoms.
Or the method of manufacturing a semiconductor device according to item 5. 8. A step of forming an insulating film on a semiconductor substrate, a step of smoothing the insulating film by polishing, a step of forming a highly oriented layer on the insulating film, and a step of forming the highly oriented layer on the highly oriented layer. And a step of forming a metal film thereon. 9. A step of forming an insulating film on a semiconductor substrate, a step of smoothing the insulating film by exposing it to radicals of halogen atoms, and a step of forming a highly oriented layer on the insulating film. And a step of forming a metal film on the highly oriented layer. 10. A step of forming a substantially flat insulating film on a substrate having irregularities, a step of further smoothing the surface of the insulating film, a step of forming a highly oriented layer on the insulating film, And a step of forming a metal film on the highly oriented layer.