JPH0945770A - Semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the titanium nitride buried in a minute through hole from being etched when etching an upper-layer wiring with chloric gas. SOLUTION: Titanium 3 and titanium nitride 4 are left only in a through hole 2a opened in a silicon oxide film 2, being etched back after being grown all over into the through hole 2a. Next, a titanium tungsten film 5 is made thinly on a titanium nitride film 4 and the titanium film selectively by a CVD method, and thereon titanium 5 and Al alloy 7 are made, and then using the resist film 8 as a mask, they are etched by chloric gas to form Al wiring. Even if the margin of alignment is small, and the through hole 2a is exposed from the At wiring, the titanium nitride film 4 and the titanium film 3 are never etched, being protected with the tungsten film 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device in which a connection opening provided in an interlayer insulating film is filled with a refractory metal or a refractory metal compound and a manufacturing method thereof.

[0002]

2. Description of the Related Art High integration of semiconductor devices has been promoted by miniaturization of design rules and multilayer wiring. With the miniaturization of design rules, the diameter of the opening for connecting elements or wirings also becomes smaller.However, since the thickness of the interlayer insulating film hardly changes, the diameter of the opening can be reduced. The aspect ratio divided by is increasing, and the aspect ratio is about to exceed 5.

It is difficult to form titanium nitride having a required film thickness in such an opening having a high aspect ratio by a sputtering method which has been widely used conventionally. Titanium nitride prevents a reaction between an Al alloy, which is a wiring material, and a Si substrate, and a reaction between tungsten hexafluoride (WF ₆ ) which is a raw material gas and a silicon substrate when W is grown by a chemical vapor deposition method. There is a role as a barrier metal for preventing the above, and in order to fulfill these roles, it is necessary to form titanium nitride having a thickness of 10 nm or more at the bottom of the opening.

Since it is difficult to form titanium nitride having a thickness of 10 nm or more in an opening having an aspect ratio of more than 5 by a sputtering method, a chemical vapor deposition method (CV) having an excellent covering property is used.
Method D) is being used. When the diameter of the opening is as small as 0.3 μm or less, the conventional method of growing tungsten on titanium nitride to fill the opening requires a large number of steps, resulting in high cost. A method for reducing costs has been proposed (for example, Autumn 1993 54th Annual Meeting of the Society of Applied Physics, Proceedings, p-707, 28p-ZE-2). In the method of filling the opening with titanium nitride described above, since the stress of titanium nitride is generally large and the growth rate is small,
It is difficult to grow thick and it has not been practically used so far. However, when the diameter of the opening becomes as small as 0.3 μm or less, it becomes possible to embed even a thin film thickness of about 0.15 μm, and it becomes possible to put it into practical use.

As a conventional method of filling the opening with W after forming titanium nitride, titanium nitride is grown on the entire surface, W is grown on the entire surface, and W is etched back on the entire surface to open the opening. A method of leaving W only in the inside is general, but this method involves a large number of steps and is costly, and the covering property of titanium nitride is poor.
Since the barrier property during growth may be insufficient and a junction leak may occur, the following method has been proposed. The method will be described with reference to the drawings.

As shown in FIG. 4A, an interlayer insulating film made of a silicon oxide film 22 is first formed on a silicon substrate 21, an opening reaching the silicon substrate 21 is formed, and then a shoulder of the opening is formed. Then, the titanium nitride 23 is formed by the chemical vapor deposition method under the condition that the growth rate and the etching rate are the same.

After that, as shown in FIG. 4 (b), the titanium nitride 23 is entirely etched back, and then a photoresist film 24 is formed only around the opening as shown in FIG. 4 (c). As shown in d), the titanium nitride 23 on the interlayer insulating film is removed by etching to leave the titanium nitride 23 only in the opening.

After that, as shown in FIG. 4 (e), WF ₆ was reduced on the titanium nitride by silane (SiH ₄ ),
W25 is selectively grown to fill the opening with W25, and as shown in FIG.
Wiring is formed (see, for example, JP-A-4-7825).

[0009]

In the conventional method for manufacturing a semiconductor device shown in FIG. 4, there is a problem that the step of leaving titanium nitride only at the bottom of the opening is complicated and the cost becomes high. . Furthermore, the opening is mainly filled with W
Since it is very difficult to form W thickly only on titanium nitride without growing W on the interlayer insulating film at all, it is very difficult to grow W on the interlayer insulating film. Also, W grows granularly. For example 1.0μ
When forming W with a thickness of m, W with a diameter of about 0.5 μm
Grains are formed on the interlayer insulating film. When an Al alloy film is formed thereon to form a wiring, W is not etched and remains by etching the Al alloy.
There is also a problem that the wirings are short-circuited as shown in (f).

When a fine opening having a diameter of 0.3 μm or less is filled with titanium nitride, there is almost no margin for alignment between the opening and the wiring when the wiring is formed thereon with an Al alloy or the like. In the case where the opening protrudes from the wiring, if the wiring is made of Al, Al alloy, Cr, or Cu alloy, titanium nitride is etched because the etching is performed with a chlorine-based gas, and the opening that protrudes from the wiring is formed. Part of the titanium nitride is etched to form a depression (FIG. 5A).

When the depression is formed, the coverage of the interlayer insulating film such as the silicon oxide film 32 formed on the depression is deteriorated, the reliability of the wiring is lowered, and it is difficult to flatten the interlayer insulating film. There is a problem that it comes (Fig. 5
(B)).

An object of the present invention is to provide a semiconductor device having a structure for preventing titanium nitride from being etched when the upper wiring is etched with chlorine gas and a method for manufacturing the same.

[0013]

In order to achieve the above object, a semiconductor device according to the present invention has a through-hole provided in an interlayer insulating film for connecting elements or wirings with a refractory metal or refractory metal compound. It is a semiconductor device embedded with
Most of the through holes are filled with a titanium nitride film, and the titanium nitride film is covered with a thin tungsten film or a tungsten compound film.

The wiring on the through hole filled with the refractory metal or the refractory metal compound is mainly selected from aluminum, aluminum alloy, copper and copper alloy.

The thickness of the tungsten film or the tungsten compound film is 20 to 200 nm.

The method of manufacturing a semiconductor device according to the present invention includes an embedding step, an etching step, and a film forming step, and a through hole provided in an interlayer insulating film for connecting elements or wirings is formed. A method of manufacturing a semiconductor device to be embedded with a refractory metal or a refractory metal compound, wherein the embedding step is a step of filling the through-holes by overall growth of a titanium nitride film, and the etching step is a step of forming an etching on the interlayer insulating film. Is a process of removing the titanium nitride film to leave the titanium nitride film only in the through hole, and the film forming process is a process of forming a thin tungsten film or a tungsten compound film only on the titanium nitride film.

The method of removing the titanium nitride film is as follows:
It is a full-etch back method.

The method of removing the titanium nitride film is as follows.
It is a polishing method.

The method of growing the titanium nitride film is as follows.
It is a chemical vapor deposition method.

The diameter of the through hole is 300 nm or less, and the grown film thickness of the titanium nitride film is 300 nm or more.

Further, the tungsten film is selectively formed only on the titanium nitride film by a chemical vapor deposition method.

The specific resistance of the titanium nitride film is 30.
It is μΩcm or less.

After the step of forming the tungsten film or the tungsten compound film, a step of forming a metal layer mainly containing aluminum, an aluminum alloy, copper, or a copper alloy on the entire surface, and the step of forming the metal layer with chlorine. It includes a step of patterning by etching with a gas containing the same.

The film thickness of the tungsten film or the tungsten compound is 20 to 200 nm.

As described above, according to the present invention, titanium nitride is buried in the through hole provided in the interlayer insulating film, and the surface layer of the titanium nitride is made of thin tungsten or a tungsten compound, so that the upper layer wiring is changed to chlorine gas. The titanium nitride in the through hole is prevented from being etched during the etching.

[0026]

Next, the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 6 is a cross-sectional view showing the step of manufacturing. As shown in FIG. 1A, first, a silicon oxide film 2 having a thickness of 1.5 μm is formed on a silicon substrate 1 on which elements are formed. Boron or phosphorus may be added to the silicon oxide film 2. A through hole 2a having a diameter of 0.3 μm is formed at a desired position of the silicon oxide film 2 by a usual lithography technique and a dry etching technique to a depth reaching the silicon substrate 1. Since the diameter of the through hole 2a is 0.3 μm for a depth of 1.5 μm,
Its aspect ratio is 5.

After that, a titanium film 3 having a thickness of 100 nm and a titanium nitride film 4 having a film thickness (here, 1) are formed by collimating sputtering on the entire surface of the silicon oxide film 2.
(Thickness of 50 to 300 nm). The titanium nitride film 4 has a large stress and is peeled off or cracks are formed when it is formed thicker than 300 nm.
It is desirable to apply it to a contact that can be embedded with the above film thickness.

In the collimated sputtering method, a so-called collimated plate in which a large number of holes are provided between a target and a substrate is installed, and only sputtered particles that are incident in a direction almost perpendicular to the substrate are selected and the substrate is selected. Is a sputtering method with improved coverage at the bottom of the opening,
Here, the thickness of the collimator plate: the diameter of the opening of the collimator plate is 2: 1 and the titanium film 3 of about 10 nm is formed on the bottom of the through hole 2a.

The titanium nitride film 4 is formed by thermal decomposition of tetraxidemethylaminotitanium (TDMAT). There is also a method of nitriding by adding ammonia (NH ₃ ), but this is not suitable for filling a fine opening because the step coverage deteriorates. Pressure during growth is 0.3-1.0
The substrate temperature is 350 to 450 ° C. In this temperature range, the growth is performed by the surface rate-determining reaction, so that it is excellent in step coverage and is suitable for embedding in the fine through holes 2a.

Next, as shown in FIG. 1B, the titanium nitride film 4 and the titanium film 3 are entirely etched by a reactive ion etching method using a boron trichloride (BCl ₃ ) gas, and the silicon oxide film 2 is covered. And leave them only in the through hole 2a. At that time, over-etching is performed so that the titanium nitride film 4 and the titanium film 3 are present at positions recessed downward by about 10 to 20 nm from the upper opening edge of the through hole 2a.

Next, as shown in FIG. 1C, a titanium tungsten (TiW) film 5 in which about 10% by weight of titanium is added to tungsten is formed to a thickness of 200 to 500 nm by using a sputtering method. In the sputtering method, the step coverage is not good, but since the depression degree of the titanium nitride film 4 and the titanium film 3 in the through hole 2a is extremely small, the titanium tungsten film 5 is used in the depression portion in the through hole 2a by the sputtering method. It can be completely embedded.

Next, as shown in FIG. 1D, the titanium-tungsten film is entirely etched by reactive ion etching using CF ₄ gas to remove it from the silicon oxide film 2, and this is removed from the inside of the through hole 2a. Leave only in the recessed part,
Make it almost flat.

Here, instead of the method of growing the titanium tungsten film over the entire surface and filling the recessed portion of the through hole 2a by etching back, the tungsten film 9 is replaced with the titanium film 3 by the low pressure chemical vapor deposition method as shown in FIG. You may make it selectively grow 10-20 nm only on the titanium nitride film 4. In this case, the tungsten film 9 is grown by reducing tungsten hexafluoride (WF ₆ ) gas with SiH ₄ . The growth temperature is 200 to 270 ° C., and S
The flow rate of iH ₄ is 50 to 100% of WF ₆ , and the total pressure is 10 to 100 mTorr.

The film thickness of the tungsten film 9 is 10 to 20 nm.
Since it is thin, the tungsten film 9 hardly grows on the silicon oxide film 2. When the tungsten film 9 is selectively grown on the titanium nitride film 4, the time from the gas flow to the start of growth of the tungsten film 9 changes depending on the specific resistance of the titanium nitride film 4. Since the film 9 is difficult to grow and it is difficult to maintain the selectivity with respect to the silicon oxide film 2, it is desirable that the specific resistance of the titanium nitride film 4 be 300 μΩcm or less. If the specific resistance of the titanium nitride film 4 is 300 μΩcm or less,
Even if the tungsten film 9 is grown to a thickness of 10 to 20 nm, the tungsten film 9 does not grow on the silicon oxide film 2 at all.

Next, as shown in FIG. 1 (e), the second titanium nitride film 6 has a thickness of 50 to 100 nm and the Al alloy film 7 has a thickness of 0.
After sequentially forming a film having a thickness of 3 to 1.0 μm by a sputtering method, a photoresist film 8 is applied and a desired pattern to be an Al wiring is formed by exposure and development. At this time, if there is a small margin for the alignment of the through hole 2a and the Al wiring, the through hole 2a will protrude from the photoresist film 8.

Next, as shown in FIG. 1F, an Al alloy film 7 and a titanium nitride film are formed by a reactive ion etching method using a gas containing chlorine, for example, a gas such as Cl ₂ , BCl ₃ , CCl ₄ , or SiCl _4. After etching the film 6, the photoresist film 8 is removed. At that time, the surface of the through hole 2a is exposed, but since the titanium tungsten film 9 is present on the surface, it is hardly etched by a chlorine-based gas, and a recess is not formed in the through hole 2a.
Al wiring can be formed.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
FIG. 6 is a cross-sectional view showing the step of manufacturing. As shown in FIG. 3A, first, a first wiring is formed of polycrystalline silicon 13 on a silicon substrate 11 whose surface is covered with a silicon oxide film 12. Next, after forming the second silicon oxide film 14, the through holes 14a and 14b reaching the silicon substrate 11 and the polycrystalline silicon 13 are formed by using the ordinary lithography technique and dry etching technique, and then the titanium film 15 and the titanium film 15 are formed. The titanium nitride film 16 is sequentially formed by the chemical vapor deposition method.

The titanium film 15 is formed by plasma CVD by adding hydrogen to titanium tetrachloride (TiCl ₄ ). The titanium nitride film 16 is formed by nitriding TiCl ₄ with ammonia (NH ₃ ) and using a normal low pressure CVD method without using plasma.

Since the titanium film 15 has good step coverage, it may have a thickness of 5 to 20 nm. Further, the titanium nitride film 16 has a thickness larger than that in which the through holes 14a and 14b can be embedded as in the first embodiment. However, if it is too thick, film peeling or cracks occur, so it is preferable to set the thickness to 300 nm or less. Further, in this method, since the film does not contain carbon,
Compared with the first embodiment, the specific resistance of the titanium nitride film 16 is 1
It is possible to make it as small as 00 to 150 μΩcm,
It is advantageous to selectively grow a tungsten film on it.

Next, as shown in FIG. 3B, the titanium nitride film 16 and the titanium film 15 are polished by the chemical mechanical polishing method and removed from the silicon oxide film 14. This makes the surface almost flat.

Next, as shown in FIG. 3C, a tungsten film 17 having a thickness of 20 to 200 nm is selectively formed on the surfaces of the titanium film 15 and the titanium nitride film 16 by a low pressure CVD method. The tungsten film 17 may be formed by reducing WF ₆ with SiH ₄ as in the first embodiment.
It may be formed by reducing F ₆ with hydrogen. The method of reducing with hydrogen has a smaller growth rate than the method of reducing with SiH ₄ , but there is no problem because the grown film thickness is small.

Since the surface of the tungsten film 17 is flat,
Since the film grows laterally as much as the grown film thickness, if it is made thick, it may short-circuit with an adjacent wiring or the like, and it cannot be formed too thick.
It is desirable that the thickness is 00 nm or less. Further, if the tungsten film 17 is thinner than 20 nm, it may be etched when the Al alloy is etched thereafter, and the titanium film 15 and the titanium nitride film 16 under the tungsten film 17 may also be etched. The film 17 has a thickness of 20 nm or more.

Next, as shown in FIG. 3D, after growing a tungsten film 17, an Al alloy film 18 is formed by a sputtering method, and a photoresist film 19 is applied thereon.
A desired pattern to be an Al wiring is formed by exposure and development. At this time, if the margin for alignment between the through holes 14a and 14b and the Al wiring is small, the through holes 14a and 14b will protrude from the photoresist film 19.

Next, as shown in FIG. 3E, an Al alloy film 18 is formed by a reactive ion etching method using a gas containing chlorine.
After etching, the photoresist film 19 is removed to complete the Al wiring. At this time, even if the surfaces of the through holes 14a and 14b are exposed, the tungsten film 17 is hardly etched by the chlorine-based gas, so that the titanium nitride film 16 and the titanium film 15 below are not etched.

Through holes 14 having different depths as in this embodiment
It is possible to form a and 14b at the same time.

In the embodiment described above, the through-hole connecting to the silicon substrate or the polycrystalline silicon is provided, but the present invention is not limited to this, and the present invention is also applied to the through-hole connecting to the underlying Al wiring or the like. It goes without saying that you can do it. The lower wiring is a refractory metal or its silicide,
Or when the Al alloy film is covered with a refractory metal,
Since the titanium film is not particularly required as the lower layer of the titanium nitride film, the titanium nitride film may be directly grown after the formation of the through hole to fill the through hole.

Although the upper layer wiring is made of Al alloy, it is not limited to this, and copper or copper alloy can be etched by plasma etching while irradiating ultraviolet rays using chlorine gas.

[0049]

As described above, according to the present invention, most of the through holes provided in the interlayer insulating film are filled with a titanium nitride film, and the titanium nitride film is covered with a thin tungsten film or a tungsten compound film. When forming an Al alloy or copper as a wiring metal on it and etching with a gas containing chlorine, the titanium nitride film in the through hole is completely etched even if the through hole protrudes from the wiring because there is no alignment margin. It is possible to form the interlayer insulating film on the insulating film with good coverage, and it is possible to easily form the fine multilayer wiring having the fine through holes without deteriorating the reliability.

Even when the tungsten film on the titanium nitride film is selectively formed by the CVD method, the film thickness may be thin, so that the selectivity is deteriorated and there is no short circuit between wirings due to the tungsten film. Wiring can be formed with good yield.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a diagram showing another example of a process on the way in the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a second embodiment of the present invention in the order of manufacturing steps.

FIG. 4 is a cross-sectional view showing a conventional example in the order of manufacturing steps.

FIG. 5 is a cross-sectional view showing a problem of the conventional technique.

[Explanation of symbols]

 1,11,21 Silicon substrate 2,12,14,22,32 Silicon oxide film 3,15 Titanium film 4,6,16,23 Titanium nitride 5 Titanium tungsten (TiW) film 9,17,25 Tungsten (W) film 7, 18, 26, 31 Al alloy 8, 19, 24 Photoresist film 13 Polycrystalline silicon

Claims (12)

[Claims] 1. A semiconductor device in which a through hole provided in an interlayer insulating film for connecting elements or wirings is filled with a high melting point metal or a high melting point metal compound, and most of the through hole is a titanium nitride film. A semiconductor device in which the titanium nitride film is buried and covered with a thin tungsten film or a tungsten compound film. 2. The wiring on the through hole filled with the refractory metal or the refractory metal compound is mainly selected from aluminum, aluminum alloy, copper and copper alloy. Item 2. The semiconductor device according to item 1. 3. The semiconductor device according to claim 2, wherein the film thickness of the tungsten film or the tungsten compound film is 20 to 200 nm. 4. An embedding step, an etching step, and a film forming step, wherein a through hole provided in an interlayer insulating film for connecting elements or wirings is filled with a refractory metal or a refractory metal compound. A method of manufacturing a semiconductor device, wherein the burying step is a step of burying the through hole by overall growth of a titanium nitride film, and the etching step removes the titanium nitride film on the interlayer insulating film to remove the titanium nitride film. A method of manufacturing a semiconductor device, which is a process of leaving the titanium nitride film only in the through-hole, and the film forming process is a process of forming a thin tungsten film or a tungsten compound film only on the titanium nitride film. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the method of removing the titanium nitride film is a full surface etchback method. 6. The method of manufacturing a semiconductor device according to claim 4, wherein the method of removing the titanium nitride film is a polishing method. 7. The method for manufacturing a semiconductor device according to claim 4, wherein the growth method of the titanium nitride film is a chemical vapor deposition method. 8. The method of manufacturing a semiconductor device according to claim 7, wherein the diameter of the through hole is 300 nm or less, and the grown film thickness of the titanium nitride film is 300 nm or more. 9. The manufacturing of a semiconductor device according to claim 4, wherein the tungsten film is selectively formed only on the titanium nitride film by a chemical vapor deposition method. Method. 10. The specific resistance of the titanium nitride film is 30.
The method for manufacturing a semiconductor device according to claim 9, wherein the value is μΩcm or less. 11. A step of forming a metal layer mainly containing aluminum, an aluminum alloy, copper, or a copper alloy on the entire surface after the step of forming the tungsten film or the tungsten compound film; 11. The method of manufacturing a semiconductor device according to claim 4, 5, 6, 7, 8, 9, or 10, including a step of patterning by etching with a gas containing 12. The method of manufacturing a semiconductor device according to claim 11, wherein a film thickness of the tungsten film or the tungsten compound is 20 to 200 nm.