JPH10294315A - Formation of metal wiring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for forming the metal wiring, which can perform reflowing and high-pressure embedding of the metal-wiring material such as Al and Cu by the simple process. SOLUTION: After a groove 2 for forming a groove wiring by etching an SiO2 film 3 is formed, a Cu film 4 is formed by a sputtering method. Then, hydrogen is diffused in the Cu film 4 by treated with hydrogen plasma 5. Thereafter, when reflowing is performed in the hydrogen atmosphere for the Cu film 4, the Cu, which is oxidized not only by the hydrogen in gaseous phase but also by the hydrogen, which is desorpted from the Cu film 4, is reduced. Thus, the reflowing of the Cu film 4 at the low temperature can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a metal wiring. More specifically, the present invention relates to a method for forming a metal wiring such as an embedded wiring or a plug used for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In a semiconductor device, a wiring or a plug for electrically connecting an element or an element or an element and an external wiring (in this specification, these are collectively referred to as "metal wiring")
Alternatively, a metal such as aluminum (Al) or copper (Cu) is used. As one method of forming metal wiring, damascene (damas) is used.
The cene) method is known. In the damascene method, a groove corresponding to the shape of a metal wiring is formed in an interlayer insulating film, and then a metal film is formed, and a CMP (Chemical Mechanical) method is performed.
This is a method in which a trench wiring is formed by removing an unnecessary portion on an upper portion by a cal polishing method or the like.
In order to implement the damascene method, it is necessary to sufficiently embed metal wiring material in narrow grooves and small openings in order to improve coverage, and reflow technology and high-pressure embedding technology are used as methods for that purpose. ing.

In the reflow technique, a concave portion such as a groove or a hole serving as a wiring forming region is formed on the surface of an insulating material, a metal film is formed thereon, and then the metal is fluidized and poured into the groove. This is a method of forming a desired wiring. For reflow technology, see Park, C .; S. et al: V-
MIC Conf. , 326 (1991). On the other hand, the high-pressure embedding technique is a method in which a metal is fluidized while maintaining a high temperature after a metal film is formed, and an inert gas such as an argon (Ar) gas is pressed at a high pressure. For the high-pressure embedding technology, reference can be made to Shinya Hosaka et al .: Proceedings of the 50th Annual Conference of the Japan Society of Applied Physics, Second Supplement, 636 (1989).

[0004]

In the case where the wiring material is aluminum (Al), if Al is deposited on a concave portion such as a groove and then exposed to an oxidizing atmosphere such as the atmosphere, reflow at a low temperature or high pressure may occur. There is a problem that embedding is not successful. This is because if an Al film is formed and then exposed to the atmosphere, an oxide film is formed on the surface, which hinders reflow and high-pressure embedding. Regarding this point, “Innovation of Logic LSI Technology” (Science Forum) 211
Pp. 214 pages. A similar problem occurs when the wiring material is copper (Cu).

[0005] However, it is difficult to carry out reflow or vacuum embedding after film formation of Al or Cu while transporting the film to another apparatus while maintaining the same vacuum. For the case of Cu,
A device has been devised to lower the reflow temperature by using a vacuum annealing method, a reduction method, or the like (for this, see "Innovation in Logic LSI Technology" (Science Forum) 215
~ Page 220). However, these methods also have various problems to be implemented in an actual production line.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a method for forming a metal wiring which enables reflow or high-pressure embedding of a metal wiring material such as copper or aluminum in a simple process. I do.

[0007]

According to a first aspect of the present invention, there is provided a method for forming a metal wiring, comprising forming a wiring material on a recessed region for forming a metal wiring. A step of implanting at least one of hydrogen ions and ions containing hydrogen atoms into the formed wiring material, and an embedding step of embedding the ion-implanted wiring material in the recessed region. It is characterized by the following.

[0008] A method for forming a metal wiring according to a second aspect of the present invention includes:
A film forming step of forming a wiring material on the recessed region for forming the metal wiring, and a hydrogen storage metal film forming step of forming a hydrogen storage metal that stores hydrogen on the formed wiring material. Embedding the wiring material in which a hydrogen-absorbing metal which has absorbed hydrogen on the upper portion thereof into a film is embedded in the recessed region.

A third invention, a method for forming a metal wiring, comprises:
A film forming step of forming a wiring material on the concave region for forming the metal wiring, and forming an oxidation-resistant metal film on the wiring material while preventing oxidation of the formed wiring material. An oxidation-resistant metal film forming step and an embedding step of embedding a wiring material after the oxidation-resistant metal film forming step in the recessed region are provided.

According to the first invention, as described above, hydrogen in a wiring material is desorbed from the wiring material by implanting hydrogen ions or ions containing hydrogen atoms into the formed wiring material. Since the oxidized wiring material is effectively reduced, the reflow of the wiring material and the application of the high-pressure embedding technique can be performed, and the wiring material can be reliably embedded in the recessed region serving as the wiring formation region.

According to a second aspect of the present invention, as described above, by forming a hydrogen storage metal film storing hydrogen on a wiring material, a wiring oxidized when hydrogen in the hydrogen storage metal is desorbed is formed. Since the material is effectively reduced, the reflow of the wiring material and the application of the high-pressure embedding technology can be performed, and the wiring material can be reliably embedded in the recessed region serving as the wiring formation region.

According to the third aspect of the present invention, the oxidation of the wiring material is prevented by forming an oxidation-resistant metal film on the wiring material while preventing the formed wiring material from being oxidized. Therefore, the reflow of the wiring material and the application of the high-voltage embedding technique can be performed, and the wiring material can be reliably embedded in the recessed region serving as the wiring formation region.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 shows a copper (C) according to a first embodiment of the present invention.
FIG. 9 is a cross-sectional view for describing a method of forming the groove wiring of u) in the order of steps. First, plasma silane (SiH ₄ ) and N ₂ O are applied to the silicon substrate 1 shown in FIG.
VD (Chemical Vapor Deposit)
An SiO ₂ film 3 having a thickness of 0.5 μm is formed by the (ion) method, and a groove 2 having a width of 0.5 μm is formed by the dry etching method. FIG.
(B) shows this state. Although a metal via plug and the like are actually provided below the SiO ₂ film 3, they are not shown in the drawing because they are not directly related to the present invention. 2 and 3 to be described later.
The same applies to.

Next, on the top of FIG.
An m-th Cu film 4 is formed by a sputtering method. However, FIG.
As shown in (c), the Cu film 4 at this stage is not flat, but has a semicylindrical shape on the SiO ₂ film 3 and a triangular cross section at the bottom of the groove 2. Next, the silicon substrate 1 on which the Cu film 4 has been formed is heated to 300 ° C., and in an atmosphere of 1 SLM of H ₂ gas and a pressure of 500 mTorr, a negative bias of 800 V is applied to the substrate side to 1500 ° C.
An RF power of W is applied to generate a hydrogen plasma 5. FIG. 1D shows the state at this time. This hydrogen plasma contains hydrogen ions and hydrogen radicals, which react with the Cu film 4. As a result, hydrogen is diffused and remains in the surface layer portion (to a depth of about several hundred angstroms from the surface) of the Cu film 4. Processing time is about 10 minutes.

Subsequently, the silicon substrate 1 is set at 1 SLM,
Heat to about 400 ° C. in a 1 Torr hydrogen atmosphere and hold for 5 minutes. At this time, hydrogen in the gas phase atmosphere is
In addition to the reduction of the oxide, the oxide of the Cu film 4 is effectively reduced when the hydrogen introduced into the Cu film 4 by the hydrogen plasma desorbs from the surface. This makes it possible to reduce the Cu film 4 more effectively as compared with the case where the treatment is simply performed in a hydrogen atmosphere.
Even if the u film is exposed to the atmosphere, the desorbed hydrogen reduces the Cu oxide, so that the Cu film 4 can be reliably reflowed. Therefore, the Cu film 4 is made of Cu
Is reflowed at about 400 ° C., which is significantly lower than the melting point of 1080 ° C. Cu is reliably buried inside the groove 2 by reflow.

When the Cu film 4 is reflowed, the Cu film 6 becomes almost flat as shown in FIG. Then, CMP
By grinding the surface of the Cu film 6 by the method shown in FIG.
A flat buried trench wiring 7 as shown in FIG.
By the way, in the above, as shown in FIG.
Hydrogen plasma is generated as a method of diffusing hydrogen in the film 4. However, as another method, for example, an ion cluster beam is used, and hydrogen ions or ions containing hydrogen atoms (ions containing hydrogen atoms as constituent elements, for example, SiH
₄ or PH ₃ ). For this ion cluster beam, for example, reference can be made to “Ion Beam Applied Technology” (CMC), etc.

The types of the films and the specific values of the film thickness used in the first embodiment are merely examples, and these can be changed without departing from the gist of the invention. For example,
In the above, Cu was used as the wiring material, but Al can be used instead of Cu. Further, although a method of reflowing Cu is used as a method of embedding Cu in the groove, a high-pressure embedding method may be applied. In this method, for example, after forming an Al film, an Al bridge is formed on the upper portion of the groove 2 and a high-pressure chamber (60M) of an inert gas such as argon is formed.
(Pa, 400 ° C.) by pressing Al into the groove 2. This high-pressure embedding method can also be applied to Cu.

Second Embodiment FIG. 2 is a cross-sectional view for explaining a method of forming a grooved wiring of Cu according to a second embodiment of the present invention in the order of steps. First, the silicon substrate 11 shown in FIG.
0.5 μm by plasma CVD using H ₄ and N ₂ O
Forming a SiO ₂ film 13 to form a groove 12 of width 0.5μm by dry etching. FIG. 2B shows this state.

Next, a Cu film 14 having a thickness of about 1.5 μm is formed on the groove 12 shown in FIG.
However, as shown in FIG. 2C, the Cu film 14 at this stage is not flat, but has a semicylindrical shape on the SiO ₂ film 13 and a triangular cross section at the bottom of the groove 12. Thereafter, the silicon substrate 11 is maintained at a temperature of 100 ° C., and a mixed gas of Ar gas and H ₂ gas for plasma generation (Ar /
In a H ₂ gas), a 0.1 μm-thick palladium (Pd) film 15 is formed on the Cu film 14 by a sputtering method. Since Pd is a hydrogen storage metal, hydrogen is taken in the Pd film 15 formed by such a process.

Subsequently, this silicon substrate 11 is
Heated to 400 ° C. in a hydrogen atmosphere of M, 1 Torr,
Hold for a minute. At this time, in addition to the hydrogen in the gaseous phase atmosphere reducing the oxide of the Cu film 14, the oxide of the Cu film 14 is effectively reduced when the hydrogen in the Pd film 15 is further desorbed. This makes it possible to reduce the Cu film 14 more effectively as compared to a case where the Cu film 14 is simply treated in a hydrogen atmosphere. Even if the Cu film 14 is exposed to the atmosphere before the reflow, the Cu film 14 is surely reflowed. Can be done.
At this time, the Cu film 14 reflows at about 400 ° C., which is much lower than 1080 ° C., which is the melting point of Cu. This ensures that Cu is buried inside the groove 12.

When reflowing Cu, the Pd film 1
5 is mostly concentrated on the upper layer of the flat Cu film 16. Therefore, by the CMP method, C
When the surface of the u film 16 is ground, Pd is almost completely removed, and as a result, as shown in FIG. By the way, in the above, Cu
The Pd film 15 was used as a film formed on the film 15. This focuses on the fact that when Pd is formed in a mixed gas (Ar / H ₂ gas), it has a property of absorbing hydrogen. Metals, alloys, and other substances that occlude hydrogen (these are collectively referred to as “hydrogen occlusion metals” in this specification) include, for example, ZrMn ₂ , LaCo ₅ ,
Mg ₂ Cu, LaNi and the like are known. Therefore, even if these are formed on the Cu film 14 instead of Pd, the same effect as in the case of Pd can be expected.

The types of the films and the specific values of the film thickness used in the second embodiment are merely examples, and these can be changed without departing from the gist of the invention. For example, as a method of storing hydrogen in the hydrogen storage metal, in addition to the method of storing hydrogen at the same time as the film formation by the sputtering method as described above, for example, a method of heating in a hydrogen atmosphere after the film formation can also be used. . In the second embodiment, Cu is used as the wiring material.
1 can also be used. Further, as a method of embedding Cu into the groove, a method of reflowing Cu was used.
As in the case of the embodiment, a high-pressure embedding method using an inert gas can be applied.

Third Embodiment FIG. 3 is a cross-sectional view for explaining a method of forming a Cu trench wiring according to a third embodiment of the present invention in the order of steps. First, by using SiH ₄ and N ₂ O in the silicon substrate 21 shown in FIG. 3 (a), 0.5 by a plasma CVD method
A SiO ₂ film 23 having a thickness of μm is formed, and a groove 22 having a width of 0.5 μm is formed by a dry etching method. FIG. 3B shows this state.

Next, as shown in FIG.
An m-th Cu film 24 is formed by a sputtering method. However, as shown in FIG. 3C, the Cu film 24 at this stage is not flat, but has a semicylindrical shape on the SiO ₂ film 23 and a triangular cross section at the bottom of the groove 22. Subsequently, the Cu film 24
The silver (Ag) film 25 is formed to a thickness of 0.2 μm while the silicon substrate 21 after the film formation is held in a vacuum.
The state after this film formation is shown in FIG. Since Ag is an oxidation-resistant metal that is less susceptible to oxidation than Cu, the Ag film 2
Even when the silicon substrate 21 on which the film 5 is formed is exposed to the air,
The oxide layer formed on the surface of the g film 25 is extremely thin, and the Cu film 24 is hardly oxidized because it is covered with the Ag film 25.

This silicon substrate 21 is 1 SLM, 1 To
Heat to 400 ° C. in a hydrogen atmosphere of rr and hold for 5 minutes. At this time, the Cu film which is hardly oxidized because the Ag film 25 is present thereon can be easily reflowed at such a relatively low temperature. As a result of the reflow, FIG.
As shown in FIG.
u is uniformly embedded in the groove 22. Ag may be partially mixed into Cu during the reflow, but since the conductivity of Ag is high, no particular inconvenience occurs when Cu is used for the wiring. Finally, by grinding the surface of the Cu film 26 by the CMP method,
A flat buried trench wiring 27 as shown in FIG.

As described above, according to the present embodiment, after the Cu film 24 is formed, the Ag film 25, which is an oxidation-resistant metal, is formed while being kept in a vacuum. The Cu film 24 serving as a wiring layer is not
Reflow can be performed at a low temperature of ℃, and fine metal wiring can be achieved while maintaining high coverage. The types of the films and the specific values of the film thickness used in the third embodiment are merely examples, and these can be changed without departing from the gist of the invention. For example, in the above description, the Ag film 25 was formed on the silicon substrate 21 after the Cu film 24 was formed. However, the same effect can be obtained by forming another oxidation-resistant metal such as gold (Au). can get. In the above description, Cu is used as the wiring material, but Al may be used instead of Cu. Further, as a method of embedding Cu in the groove, a method of reflowing Cu was used.
As in the case of the embodiment, a high-pressure embedding method using an inert gas can be applied.

[0027]

As described above, according to the first aspect of the present invention, for example, by implanting hydrogen ions or ions containing hydrogen atoms into the formed wiring material, Cu, Al It is possible to effectively prevent and reduce the oxidation of metal wiring materials at a relatively low temperature and more effectively than when simply reducing in a hydrogen atmosphere. Becomes possible,
For this reason, metal wiring with a fine pitch can be achieved while maintaining high coverage.

According to the second aspect of the present invention, by forming a hydrogen-absorbing metal film having absorbed hydrogen on a wiring material,
Since the oxidized wiring material is effectively reduced when hydrogen in the hydrogen storage metal is desorbed, Cu,
Since it is possible to more effectively prevent and reduce the oxidation of metal wiring materials such as Al at a relatively low temperature and more simply than in the case of reduction in a hydrogen atmosphere, reflow and high-pressure embedding techniques for metal wiring materials can be used. Application becomes possible, so that fine pitch metal wiring can be achieved while maintaining high coverage.

Further, according to the third aspect, the oxidation of the wiring material is prevented by forming the oxidation-resistant metal film on the wiring material, and therefore, the reflow of the wiring material and the application of the high-pressure embedding technology can be applied. As a result, the wiring material can be reliably embedded in the recessed region serving as the wiring forming region, and therefore, a metal wiring with a fine pitch can be formed while maintaining high coverage.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views for explaining a method of forming a Cu trench wiring according to a first embodiment of the present invention in the order of steps, wherein FIG. 1A shows a silicon substrate 1, and FIG. (C) shows a state in which the groove 2 is formed in the formed SiO ₂ film 3.
Shows a state in which a Cu film 4 is formed, (d) shows a state in which hydrogen plasma is irradiated, (e) shows a state in which Cu is reflowed and flattened, and (f) shows a state in which the Cu film is formed by a CMP method. This shows a state where the surface of the Cu film is ground to form a flat buried trench wiring 7.

FIGS. 2A and 2B are cross-sectional views for explaining a method of forming a trench groove of Cu according to a second embodiment of the present invention in the order of steps, wherein FIG. 2A shows a silicon substrate 11, and FIG. This shows a state in which the grooves 12 are formed in the formed SiO ₂ film 13,
(C) shows a state where the Cu film 14 is formed, and (d) shows a state where the Cu film 14 is formed.
(e) shows a state in which Cu is reflowed and flattened, and (f) shows a state in which a Pd film 15 is formed on the u film.
A state in which the surface of the Cu film is ground by the MP method to form a flat buried trench wiring 17 is shown.

FIGS. 3A and 3B are cross-sectional views for explaining a method of forming a trench wiring of Cu according to a third embodiment of the present invention in the order of steps, wherein FIG. 3A shows a silicon substrate 21 and FIG. This shows a state in which the groove 22 is formed in the formed SiO ₂ film 23,
(C) shows a state where the Cu film 24 is formed, and (d) shows a state where the Cu film 24 is formed.
(e) shows a state in which Cu is reflowed and flattened, and (f) shows a state in which the Ag film 25 is formed on the u film.
A state in which the surface of the Cu film is ground by the MP method to form a flat buried trench wiring 27 is shown.

[Explanation of symbols]

1,11,21 silicon substrate 2,12,22 groove 3,13,23 SiO ₂ film 4,14,24 Cu film 5 hydrogen plasma 6,16,26 flat Cu film 7,17,27 buried groove wiring 15 Pd Film 25 Ag film

Claims (25)

[Claims] 1. A film forming step of forming a wiring material on a concave region for forming a metal wiring, and implanting at least one of hydrogen ions and ions containing hydrogen atoms into the formed wiring material. And a burying step of burying the wiring material after the ion implantation in the recessed region. 2. The method according to claim 1, wherein the implanting step implants at least one of hydrogen ions and ions containing hydrogen atoms by an ion cluster beam method. 3. The method according to claim 1, wherein the implanting step includes irradiating the film-formed wiring material with a plasma generated by a gas containing hydrogen. 4. The method for forming a metal wiring according to claim 1, wherein said embedding step includes flowing said wiring material into said recessed region by keeping said wiring material at a high temperature. 5. The metal wiring according to claim 1, wherein the embedding step is performed by applying a high pressure to the wiring material with an inert gas at a predetermined temperature and forcing the wiring material into the recessed region. Forming method. 6. The method according to claim 1, further comprising a step of removing an unnecessary portion of the wiring material after the embedding step. 7. The method according to claim 1, wherein the wiring material is copper or aluminum. 8. The method according to claim 1, wherein the concave region is a groove for a metal wiring or a hole for a metal plug. 9. The method according to claim 1, wherein the film forming step is performed by a sputtering method. 10. A film forming step of forming a wiring material on a recessed region for forming a metal wiring, and a hydrogen absorbing metal film forming a hydrogen storage metal containing hydrogen on the formed wiring material. A method of forming a metal wiring, comprising: a metal film forming step; and an embedding step of embedding the wiring material, on which a hydrogen storage metal having hydrogen stored therein has been formed, into the concave region. 11. The method for forming a metal wiring according to claim 10, wherein said burying step is to keep said wiring material at a high temperature to flow said wiring material into said recessed region. 12. The metal wiring according to claim 10, wherein the embedding step is performed by applying a high pressure to the wiring material with an inert gas at a predetermined temperature and forcing the wiring material into the recessed region. Forming method. 13. The metal according to claim 10, wherein the hydrogen-occluding metal film forming step forms the hydrogen-occluding metal film by a sputtering method in a gas obtained by adding a gas containing hydrogen to an argon gas for plasma generation. Method of forming wiring. 14. The metal wiring according to claim 10, wherein in the hydrogen storage metal film forming step, the hydrogen storage metal is formed and then heated in a hydrogen atmosphere to store hydrogen in the hydrogen storage metal. Forming method. 15. The method according to claim 10, further comprising a step of removing an unnecessary portion of the wiring material after the embedding step. 16. The method according to claim 10, wherein the wiring material is copper or aluminum. 17. The method according to claim 10, wherein the concave region is a groove for a metal wiring or a hole for a metal plug. 18. The method according to claim 10, wherein the film forming step is performed by a sputtering method. 19. A film forming step of forming a wiring material on a concave region for forming a metal wiring, and an oxidation-resistant metal is formed on the wiring material while preventing oxidation of the formed wiring material. An oxidation-resistant metal film forming step of forming a film; and an embedding step of embedding a wiring material after the oxidation-resistant metal film forming step in the recessed region. Forming method. 20. The method according to claim 19, wherein the embedding step includes flowing the wiring material into the concave region by keeping the wiring material at a high temperature. 21. The metal wiring according to claim 19, wherein the embedding step is performed by applying a high pressure to the wiring material with an inert gas at a predetermined temperature and forcing the wiring material into the recessed region. Forming method. 22. The method according to claim 19, further comprising a step of removing an unnecessary portion of the wiring material after the embedding step. 23. The method according to claim 19, wherein the wiring material is copper or aluminum. 24. The method according to claim 19, wherein the concave region is a groove for a metal wiring or a hole for a metal plug. 25. The method according to claim 19, wherein the film forming step is performed by a sputtering method.