JP7488127B2 - METHOD FOR FORMING METAL WIRING AND FILM DEPOSITION APPARATUS - Google Patents

Description

The present invention relates to a method for forming metal wiring and a film forming apparatus.

As semiconductor devices become finer, metal wiring patterns are becoming finer and finer. It is becoming more difficult to obtain good coverage characteristics for fine wiring patterns using manufacturing processes such as barrier film formation, seed layer formation, and Cu plating using conventional dual damascene methods. In addition, the finer the wiring pattern, the greater the volume ratio of the barrier film in the metal wiring, which can increase the resistance of the metal wiring.

In this situation, a technology that uses an alloy containing Cu and Al, which does not require a barrier layer or seed layer and has excellent embedding properties for fine metal wiring patterns, is attracting attention (see, for example, non-patent literature).

"CuAl2 thin films as a low-resistivity interconnect material for advanced semiconductors", Journal of Vacuum Science & Technology B 37, 031215 (2019)

However, alloys containing Cu and Al may form, for example, the α phase or the η phase depending on the ratio of Cu to Al. If the α phase is mixed into the metal wiring, it may cause wiring breaks due to its low electromigration resistance. On the other hand, if the η phase is mixed into the metal wiring, it may cause an increase in the resistance of the metal wiring. Therefore, it is necessary to suppress the formation of these phases as much as possible.

In view of the above circumstances, the object of the present invention is to provide a method for forming highly reliable metal wiring that suppresses the formation of the above-mentioned phases, and a film formation apparatus for forming the metal wiring.

In order to achieve the above object, in a method for forming a metal wiring according to one embodiment of the present invention, a first metal material, which is a CuAl alloy and has an Al content greater than the Al content of stoichiometric composition _CuAl2 , and a second metal material, which is a CuAl alloy and has a Cu content greater than the Cu content of stoichiometric composition _CuAl2 , are each incident on a substrate at least once under a reduced pressure atmosphere, thereby forming a metal wiring containing a _CuAl2 alloy on the substrate.

According to this method for forming metal wiring, the first metal material containing aluminum and the second metal material containing copper are each incident on the substrate at least once, so that a highly reliable metal wiring containing a _CuAl2 alloy is formed on the substrate.

In the method for forming the metal wiring, the first metal material and the second metal material may be alternately incident on the substrate to form the metal wiring.

According to this method for forming metal wiring, the first metal material and the second metal material are alternately incident on the substrate, so that metal wiring containing a highly reliable _CuAl2 alloy is formed.

In the method for forming the metal wiring, the metal wiring may be formed by a sputtering method while heating the substrate.

According to this method for forming metal wiring, the metal wiring is formed by sputtering while heating the substrate, so that metal wiring containing a highly reliable _CuAl2 alloy is formed.

In the above method for forming metal wiring, the first metal material may be injected into the substrate under a reduced pressure atmosphere at a first pressure, and the second metal material may be injected into the substrate under a reduced pressure atmosphere at a second pressure different from the first pressure.

According to this method for forming metal wiring, a first metal material is injected into a substrate under a reduced pressure atmosphere of a first pressure, and a second metal material is injected into the substrate under a reduced pressure atmosphere of a second pressure different from the first pressure, so that a metal wiring containing a highly reliable _CuAl2 alloy is formed.

In the above method for forming metal wiring, the second pressure may be set higher than the first pressure.

According to this method for forming a metal wiring, the second pressure is set higher than the first pressure, so that a metal wiring containing a highly reliable _CuAl2 alloy is formed.

In the above method for forming metal wiring, the first metal material may be deposited by applying a first bias power to the substrate, and the second metal material may be deposited by applying a second bias power different from the first bias power to the substrate.

According to this method for forming metal wiring, the first metal material is deposited by applying a first bias power to the substrate, and the second metal material is deposited by applying a second bias power different from the first bias power to the substrate, so that a highly reliable metal wiring containing a _CuAl2 alloy is formed.

In the above method for forming metal wiring, the first bias power may be set higher than the second bias power.

According to this method for forming a metal wiring, the first bias power is set higher than the second bias power, so that a highly reliable metal wiring containing a _CuAl2 alloy is formed.

In the method for forming the metal wiring, a _CuAl2 alloy target may be used as a film-forming source for the metal wiring formed on the substrate.

According to this method for forming metal wiring, a CuAl ₂ alloy target is used as a film formation source, so that metal wiring containing a highly reliable CuAl ₂ alloy is formed.

In order to achieve the above object, a film formation apparatus according to one aspect of the present invention includes a vacuum vessel, a film formation source, and a control device.
The vacuum vessel can maintain a reduced pressure atmosphere.
The deposition source is capable of directing aluminum and copper toward a substrate.
The control device controls the incidence of a first metal material containing aluminum and copper, and a second metal material containing aluminum and copper but having a lower aluminum ratio and a higher copper ratio than the first metal material, onto the substrate at least once each by changing the film formation conditions.

According to such a film forming apparatus, the first metal material containing aluminum and the second metal material containing copper are each incident on the substrate at least once, so that a highly reliable metal wiring containing a _CuAl2 alloy is formed on the substrate.

In the above-mentioned film forming apparatus, the control device may perform control to alternately inject the first metal material and the second metal material onto the substrate.

According to such a film forming apparatus, the first metal material and the second metal material are alternately incident on the substrate, so that a highly reliable metal wiring containing a _CuAl2 alloy is formed on the substrate.

As described above, the present invention provides a method for forming highly reliable metal wiring and a deposition apparatus for forming the metal wiring.

FIG. 2 is a schematic diagram showing an example of a film forming apparatus for forming metal wiring according to the present embodiment. 5A to 5C are schematic cross-sectional views showing a method for forming metal wiring by a first forming method. 5A to 5C are schematic cross-sectional views showing a method for forming metal wiring by a first forming method. 5A to 5C are schematic cross-sectional views showing a method for forming metal wiring according to a comparative example. FIG. 4 is a schematic diagram showing another example of a film forming apparatus for forming metal wiring according to the present embodiment. 5A to 5C are schematic cross-sectional views showing a method for forming metal wiring by a second forming method. Figure (a) is a SEM image of the surface of film A after film A was heat-treated at 300°C for 30 minutes, figure (b) is a SEM image of the surface of film B after film B was heat-treated at 300°C for 30 minutes, and figure (c) is a SEM image of the surface of film C.

Below, an embodiment of the present invention will be described with reference to the drawings. XYZ axis coordinates may be introduced in each drawing. In addition, the same reference numerals may be used for identical components or components having the same functions, and after the components have been described, the description may be omitted as appropriate. In addition, the numerical values shown below are examples and are not limited to these examples.

In the formation of the metal wiring in this embodiment, a first metal material containing aluminum and a second metal material containing copper are each incident on a substrate at least once under a reduced pressure atmosphere lower than atmospheric pressure, thereby forming a metal wiring containing a _CuAl2 alloy on the substrate.

In addition, the _CuAl2 alloy according to this embodiment means an alloy having a θ-phase _CuAl2 alloy as a main component. For example, when the _CuAl2 alloy layer formed in this embodiment is subjected to elemental analysis, it means a copper-aluminum alloy layer of _CuAlz (1.7≦Z≦2.3).

(First embodiment)

Figure 1 is a schematic diagram showing an example of a film forming apparatus for forming metal wiring according to this embodiment.

The film forming apparatus 200A used in this embodiment is exemplified by a sputtering film forming apparatus. The film forming apparatus 200A includes a vacuum vessel 201, a target (sputtering target) 202, a power supply 203, a stage 204, a pressure gauge 205, a gas supply system 206, a gas flow meter 207, an exhaust system 208, and a control device 210. A wafer-shaped substrate 220 is placed on the stage 204. The substrate 220 includes a semiconductor material such as silicon.

The vacuum vessel 201 maintains a reduced pressure atmosphere by an exhaust system 208. The vacuum vessel 201 contains a target 202, a stage 204, a substrate 220, and the like. A pressure gauge 205 that measures the pressure inside the vacuum vessel 201 is attached to the vacuum vessel 201. A gas supply system 206 that supplies a discharge gas (e.g., Ar) is also attached to the vacuum vessel 201. The flow rate of the gas supplied into the vacuum vessel 201 is adjusted by a gas flow meter 207.

The target 202 is a film formation source for the film formation apparatus 200A. The target 202 is made of an aluminum-copper alloy. For example, when the target 202 is sputtered by the plasma formed in the vacuum vessel 201, aluminum and copper are emitted from the target 202 toward the substrate 220.

The power supply 203 supplies discharge power to the target 202. The power supply 203 may be a DC power supply or a high-frequency power supply such as RF or VHF. When the discharge power is supplied from the power supply 203 to the target 202, a plasma is formed near the sputtering surface of the target 202.

The stage 204 faces the target 202. The stage 204 supports the substrate 220. The stage 204 is provided with a temperature control mechanism. A bias potential can be applied to the stage 204.

The control device 210 controls the film forming apparatus 200A. For example, the control device 210 controls the power of the power source 203, the aperture of the gas flow meter 207, the bias power applied to the stage 204, the temperature of the stage 204, etc. The pressure measured by the pressure gauge 205 is sent to the control device 210.

By changing the film formation conditions by the control device 210, a first metal material containing aluminum and copper and another second metal material containing aluminum and copper can be incident on the substrate 220. For example, even if one CuAl ₂ alloy target is installed in the film formation device 200A as the target 202, by changing the film formation conditions, a film of the first metal material and a second metal material having a different composition ratio from the first metal material can be formed on the substrate 220.

Here, the first metal material and the second metal material are metals with different composition ratios in the layers deposited on the substrate 220. For example, the second metal material has a lower ratio of aluminum and a higher ratio of copper than the first metal material. The control device 210 controls the first metal material and the second metal material to be incident on the substrate 220 at least once each.

The pressure inside the vacuum vessel 201 during film formation is maintained at a predetermined value, for example, by the control device 210 adjusting the aperture of the gas flow meter 207 or the aperture of a valve provided in the exhaust system 208.

Hereinafter, a method for forming metal wiring formed by the film forming apparatus 200A will be described. The substrate 220 is subjected to a film forming process at room temperature, and then a heat treatment is performed, or the substrate 220 is heated during the film forming process and is subjected to the film forming process. The forming conditions of the metal wiring are automatically controlled by the control device 210. In addition, in the first embodiment, one copper aluminum alloy target is used as a film forming source. Hereinafter, the copper aluminum alloy is referred to as a CuAl alloy. The CuAl alloy target may be made of a CuAl ₂ alloy, or may be made of an alloy having a composition different from CuAl _2. For example, the composition of Cu may be in the range of 30 at% to 40 at% or in the range of 33.3 at% to 38 at%.

(First formation method)

In the first formation method, a sputtering film formation process is performed while the substrate 220 is heated to 200 to 400°C.

Figures 2(a) to 3(c) are schematic cross-sectional views showing a method for forming metal wiring using the first formation method. Figures 2(a) to 3(c) show how metal wiring is formed in an opening 102 provided in the upper layer of a substrate 220.

2(a) illustrates an interlayer insulating layer 10 as an insulating layer in which metal wiring is embedded. An opening 102 consisting of a groove or a hole is formed on a surface 101 of the interlayer insulating layer 10. When the opening 102 is a groove, the groove extends, for example, in the X-axis direction. When the opening 102 is a hole, the outer shape of the hole when viewed from the Z-axis direction is circular or rectangular. An example of the hole is a via hole. The opening 102 may be bottomed or bottomless in the interlayer insulating layer 10. In FIG. 2(a), a bottomless opening 102 is illustrated. That is, the opening 102 penetrates the interlayer insulating layer 10 in the Z-axis direction.

The width w1 of the opening 102 at the bottom is, for example, 3 nm or more and 30 nm or less. The width w2 at the opening end is, for example, 5 nm or more and 50 nm or less. The depth of the opening 102 is, for example, 10 nm or more and 140 nm or less. The opening 102 may be a straight type, or a tapered type in which the width becomes wider or narrower toward the bottom.

An interlayer insulating layer 11 is provided below the interlayer insulating layer 10. For example, a metal wiring layer 12 is provided inside the interlayer insulating layer 11. A part of the metal wiring layer 12 is exposed at the bottom of the opening 102. The metal wiring layer 12 is electrically connected to, for example, any of a transistor, a resistor, a capacitor, a memory, etc. (not shown) provided below the interlayer insulating layer 11. Alternatively, the potential of the metal wiring layer 12 may be floating. Note that this embodiment also includes a structure in which the metal wiring layer 12 is removed and replaced with the interlayer insulating layer 11. In this case, the interlayer insulating layer 11 is exposed at the bottom of the opening 102.

The material of the metal wiring layer 12 is an intermetallic compound containing Cu and Al. For example, the material of the metal wiring layer 12 is a CuAl ₂ alloy. Here, the CuAl ₂ alloy means an alloy having a θ-layer CuAl ₂ alloy as a main component. For example, when the CuAl ₂ alloy layer formed in this embodiment is subjected to elemental analysis, it means a copper-aluminum alloy layer of CuAl _z (1.7≦Z≦2.3). The material of the metal wiring layer 12 may also be W and Co, which are contact materials. The interlayer insulating layers 10 and 11 contain silicon oxide. The material of the interlayer insulating layers 10 and 11 is, for example, silicon oxide or a low-k material (CVD-SiOC, CVD-SiO ₂ , etc.) with a relative dielectric constant of 3 or less.

Next, sputtering conditions are set by the control device 210, and a metal material 20A (first metal material) is formed on the surface 101 and opening 102 of the interlayer insulating layer 10. This state is shown in Fig. 2(b). As the metal material 20A, a metal material having an aluminum content greater than the aluminum content of the stoichiometric composition _CuAl2 is selected. For example, the stoichiometric composition of the metal material 20A is expressed as _CuAlx (2<x<2.82).

When the metal material 20A is deposited on the substrate 220, it obtains kinetic energy, for example, from sputtering particles. This promotes migration of the metal material 20A on the substrate 220, improving the step coverage of the metal material 20A. For example, the metal material 20A is formed along the surface 101, the inner wall 104 of the opening 102, and the bottom of the opening 102. The thickness of the metal material 20A is set to 5 nm to 50 nm.

Next, the control device 210 sets sputtering conditions different from the deposition conditions of the metal material 20A, and as shown in FIG. 2(c), the metal material 20C (second metal material) is formed on the surface 101 of the interlayer insulating layer 10 and in the opening 102 via the metal material 20A.

For example, when metal material 20A is incident on substrate 220 under a reduced pressure atmosphere of a first pressure, metal material 20C is incident on substrate 220 under a reduced pressure atmosphere of a second pressure different from the first pressure. For example, the second pressure is set higher than the first pressure, and if the first pressure is, for example, 0.05 Pa or more and 0.15 Pa or less, the second pressure is set to 0.25 Pa or more and 0.35 Pa or less.

Here, a metal material having a copper content greater than the copper content of the stoichiometric composition CuAl ₂ is selected as the metal material 20C. For example, the stoichiometric composition of the metal material 20C is expressed as CuAl _y (0.6≦y<2).

When the metal material 20C is formed on the metal material 20A, it obtains kinetic energy, for example, from sputtering particles. This promotes migration of the metal material 20C on the metal material 20A, improving the step coverage of the metal material 20C. For example, the metal material 20C is formed along the surface 101, the inner wall 104 of the opening 102, and the bottom of the opening 102 via the metal material 20A. The thickness of the metal material 20C is set to 5 nm to 50 nm. The thickness of the metal material 20C may be different from the thickness of the metal material 20A.

In this way, the metal material 20A is sputtered at the first pressure, and then the metal material 20C is sputtered at the second pressure. Since thermal sputtering is used in the sputtering, the deposition of the metal material 20A and the reflow process of the metal material 20A proceed simultaneously, and the deposition of the metal material 20C and the reflow process of the metal material 20C proceed simultaneously.

Here, since both the metallic material 20A and the metallic material 20C are heated, when the metallic material 20C is formed on the metallic material 20A, a reaction occurs between the metallic material 20A and the metallic material 20C, and a metal wiring 20 having a stable θ phase and a stoichiometric composition of _CuAl2 is formed. This state is shown in FIG.

Subsequently, the thermal sputtering deposition of the metal material 20A and the thermal sputtering deposition of the metal material 20C are alternately performed, and as shown in Fig. 3(b), the metal wiring 20 made of CuAl ₂ is laminated on the surface 101 and the opening 102. Thereafter, as shown in Fig. 3(c), the excess part of the metal wiring 20 above the surface 101 is removed by chemical mechanical polishing. By such a method, a highly reliable θ-phase CuAl ₂ layer (metal wiring 20) can be stably formed.

In this embodiment, thermal sputtering is used, which further promotes migration of the metal materials 20A and 20C on the substrate 220, thereby improving the step coverage of the metal wiring 20.

After the metal wiring 20 is formed in the opening 102, the substrate 220 is reflow-treated in-situ, for example, at 200°C to 400°C, preferably 250°C to 350°C, for 3 to 60 minutes, preferably 20 to 40 minutes. This heating may be performed inside the vacuum vessel 201, or in an annealing device independent of the vacuum vessel 201. The reflow treatment after the metal wiring 20 is formed in the opening 102 may be omitted as appropriate.

In the above example, metal material 20A and metal material 20C were formed by changing the pressure during film formation, but metal material 20A and metal material 20C may also be formed by changing the bias power applied to stage 204, or metal material 20A and metal material 20C may also be formed by changing the set temperature of stage 204.

For example, when a first bias power is applied to the stage 204 to cause the metal material 20A to be incident on the substrate 220, the metal material 20C may be incident on the substrate 220 with a second bias power different from the first bias power. For example, the first bias power is set to be higher than the second bias power.

The stage temperatures of the deposition apparatus for depositing metal material 20A and the deposition apparatus for depositing metal material 20C may be set to different temperatures. For example, the stage temperature of the deposition apparatus for depositing metal material 20A is set to be higher than the stage temperature of the deposition apparatus for depositing metal material 20C.

Furthermore, a dedicated film forming apparatus for injecting metal material 20A into substrate 220 and a dedicated film forming apparatus for injecting metal material 20C into substrate 220 may be prepared separately. Each film forming apparatus may have the same configuration, or each may have the same configuration as film forming apparatus 200A. The stage temperatures of each of these independent film forming apparatuses may be set to different temperatures.

(Comparative Example)

Here, FIG. 4(a) and FIG. 4(b) are schematic cross-sectional views showing a method for forming metal wiring according to a comparative example.

For example, when a sputtering film is formed using a target with a stoichiometric composition of CuAl ₂ , the stoichiometric composition ratio of the film formed on the substrate is not necessarily the same as the composition ratio of the target, i.e., θ- _{phase CuAl 2. In} other words, in a film formation process in a reduced pressure atmosphere, a deviation may occur between the composition ratio of the target and the composition ratio of the film.

For example, when a film is formed under a predetermined film forming condition using a _CuAl2 target, an alloy layer 300 having an Al content higher than that of the stoichiometric composition _CuAl2 may be formed on the substrate 220. This state is shown in Figure 4(a). The alloy layer 300 is a single layer.

Thereafter, when the alloy layer 300 is subjected to a thermal history as the wafer process progresses, since the alloy layer 300 contains more Al than the CuAl ₂ layer, there is a possibility that an α-phase 301 may precipitate in the alloy layer 300, as shown in Fig. 4(b) for example. If such Al particles 301 precipitate in the metal wiring, there is a possibility that a disconnection due to electromigration may occur.

On the other hand, when an alloy layer having a Cu content higher than that of the stoichiometric composition CuAl ₂ is formed as the alloy layer 300, a CuAl alloy of the η phase precipitates in the metal wiring due to thermal history, resulting in an increase in wiring resistance. Therefore, in the comparative example, there is a possibility that a highly reliable metal wiring cannot be formed.

In this way, it is difficult to find the optimum conditions for forming a θ-phase CuAl ₂ layer on a substrate using a CuAl ₂ target, and the film formation conditions are restricted to the optimum conditions. In other words, if the film formation conditions deviate from the narrow margin conditions, the θ-phase CuAl ₂ layer cannot be obtained.

There is also a method of preparing multiple targets with different target composition ratios for each deposition condition for forming a θ-phase CuAl ₂ layer, but this method requires repeated trial and error to prepare multiple targets, which leads to high target costs.

In contrast, according to the present embodiment, it is not necessary to set the film formation conditions to form a θ-phase CuAl ₂ layer. In addition, it is not necessary to prepare targets with different target composition ratios for each film formation condition. In this embodiment, a metal material 20A having a relatively high Al content compared to CuAl ₂ and a metal material 20C having a relatively high Cu content compared to CuAl ₂ are laminated, and the metal material 20A and the metal material 20C are heated, so that a highly reliable θ-phase CuAl ₂ layer (metal wiring 20) can be stably formed.

In addition, if the reflow temperature during film formation is set lower than 200°C, the reaction between metal material 20A and metal material 20C will not proceed sufficiently, which is not preferable. In addition, if the reflow temperature is set lower than 400°C, the crystallization of metal wiring 20 will be excessively promoted, which is not preferable, as it will increase the surface roughness (e.g., Ra) of metal wiring 20. Alternatively, if interlayer insulating layer 10 is made of a low-k material, this is not preferable, as the low-k material will be susceptible to thermal damage.

In addition, in order to promote the reaction between the metal material 20A and the metal material 20C, it is desirable that the thickness of the metal material 20A and the thickness of the metal material 20C are small. For example, by making the thickness of the metal material 20A and the thickness of the metal material 20C 50 nm or less, the metal wiring 20 containing a larger amount of θ-phase CuAl ₂ is formed.

(Second embodiment)

Figure 5 is a schematic diagram showing another example of a film forming apparatus for forming metal wiring according to this embodiment.

In the film forming apparatus 200B, target 202A and target 202C are provided as sputtering targets. An adhesion prevention plate 211 is provided on the outer periphery of each of targets 202A and 202C. The film forming apparatus 200B is a dual sputtering apparatus (co-sputtering apparatus).

Target 202A is made of aluminum. Target 202C is made of copper. For example, when targets 202A and 202C are sputtered by plasma formed in vacuum vessel 201, aluminum is emitted from target 202A toward substrate 220, and copper is emitted from target 202C toward substrate 220.

The power supply 203 supplies discharge power to each of the targets 202A and 202B independently. When the discharge power is supplied from the power supply 203 to each of the targets 202A and 202C, plasma is formed near the sputtering surfaces of each of the targets 202A and 202C. The control device 210 controls the power supplied by the power supply 203 to each of the targets 202A and 202BA.

By changing the film formation conditions, the control device 210 can inject a metal material containing aluminum and a metal material containing copper onto the substrate 220. The control device 210 controls the injection of each of the metal material containing aluminum and the metal material containing copper onto the substrate 220 at least once. The method of forming the metal wiring formed by the film formation device 200B is described below.

(Second formation method)

Figures 6(a) to 6(c) are schematic cross-sectional views showing a method for forming metal wiring using the second formation method. In the second formation method, a sputtering film formation process is performed while the substrate 220 is heated to 200 to 400°C.

6A, discharge power is applied to the target 202A by the power source 203 under the control of the control device 210, and a metal material 21A is formed on the surface 101 and the opening 102 of the interlayer insulating layer 10. A metal material containing aluminum is selected as the metal material 21A. For example, the metal material 21A is a metal material whose Al content is higher than the Al content of the stoichiometric composition _CuAl2 . For example, the stoichiometric composition of the metal material 20A is expressed as _CuAlx (2<x<2.82).

The Al content of the metal material 21A is adjusted by controlling the power supplied by the power source 203 to each of the targets 202A and 202C. For example, the thickness of the metal material 21A is set to 5 nm to 50 nm. The pressure during film formation is set to 0.01 Pa to 0.15 Pa.

Next, under the control of the control device 210, the power source 203 applies discharge power to the target 202C, and the metal material 21C is formed on the surface 101 of the interlayer insulating layer 10 and in the opening 102 through the metal material 21A. A metal material containing copper is selected as the metal material 21C. For example, the metal material 21C is a metal material whose Cu content is higher than the Cu content of the stoichiometric composition CuAl _2. For example, the stoichiometric composition of the metal material 20C is expressed as CuAl _y (0.6≦y<2). The Cu content of the metal material 21C is adjusted by controlling the power supplied by the power source 203 to each of the targets 202A and 202C.

For example, if the power input to target 202A when releasing metal material 21A is set to a first power and the power input to target 202C is set to a second power, the power input to target 202A when releasing metal material 21C may be set to be lower than the first power, or the power input to target 202C may be set to be higher than the second power. The thickness of metal material 21C is set to 5 nm to 50 nm. The pressure during film formation is set to 0.01 Pa to 0.15 Pa.

The deposition of metal material 21A and the deposition of metal material 21C are performed alternately in this manner, and metal material 21A and metal material 21C are alternately incident on substrate 220. As a result, laminate 21L in which metal material 21A and metal material 21C are alternately laminated is formed on surface 101 and opening 102. It is noted that either metal material 21A or metal material 21C may be formed first.

Since thermal sputtering is employed, when the metal material 21C is formed on the metal material 21A, a reaction occurs between the metal material 21A and the metal material 21C, forming the metal wiring 20 having the stoichiometric composition CuAl _2. This state is shown in FIG.

Subsequently, the thermal sputtering deposition of the metal material 21A and the thermal sputtering deposition of the metal material 21C are alternately performed, and as shown in Fig. 6C, the metal wiring 20 made of _CuAl2 is laminated on the surface 101 and the opening 102. By such a method, a highly reliable θ-phase _CuAl2 layer (metal wiring 20) can be formed.

According to the second embodiment, the process can be carried out using cheaper Al and Cu targets without using a _CuAl2 target. In addition, the formation of the metal wiring 20 can be controlled by the thickness ratio of the metal materials 21A and 21C, so the process conditions are simplified. Alternatively, CuAl alloy targets with different compositions can be combined.

After the metal wiring 20 is formed in the opening 102, the substrate 220 may be reflowed in-situ, for example, at 200° C. to 400° C., preferably 250° C. to 350° C., for 3 to 60 minutes, preferably 20 to 40 minutes, to form a highly reliable θ-phase CuAl ₂ layer (metal wiring 20).

(Example 1)

It was confirmed that the composition ratio of the CuAl alloy film changes by changing the pressure during sputtering film formation. As samples, sample A with an Al content higher than that of the stoichiometric composition _CuAl2 , sample B with a Cu content close to the stoichiometric composition _CuAl2 , and sample C with a Cu content higher than that of the stoichiometric composition _CuAl2 were prepared. The stoichiometric composition ratio of _CuAl2 was 33.33%:66.66%. The substrate was a Si substrate.

An example of the sputtering conditions for sample A is shown below.
Target: CuAl ₂ target Film formation pressure: 0.033 Pa
Substrate temperature: room temperature Discharge power: 0.48 W/ ^cm2
Discharge gas: Ar

An example of the sputtering conditions for sample B is shown below.
Target: CuAl ₂ target Film formation pressure: 0.1 Pa
Substrate temperature: room temperature Discharge power: 0.48 W/ ^cm2
Discharge gas: Ar

An example of the sputtering conditions for sample C is shown below.
Target: CuAl ₂ target Film formation pressure: 0.3 Pa
Substrate temperature: room temperature Discharge power: 0.48 W/ ^cm2
Discharge gas: Ar

The composition ratios of each are shown in Table 1. The concentrations were determined using elemental XRF analysis (AZX400, manufactured by Rigaku Corporation).

As shown in Table 1, by changing the pressure during film formation using a _CuAl2 target, it can be seen that in samples A and B at 0.1 Pa or less, a film having an Al content higher than the Al content of the stoichiometric composition _CuAl2 is formed. Also, in sample C (film formation at 0.3 Pa) where the pressure is set higher than that of samples A and B, it can be seen that a film having a Cu content higher than the Cu content of the stoichiometric composition _CuAl2 is formed.

Next, films A and B, which have different composition ratios of CuAl alloys, were alternately stacked, and the changes in the concentrations of Cu and Al after the stack was heat-treated were investigated. The deposition conditions for film A were the same as those for sample B, and the deposition conditions for film B were the same as those for sample C.

A laminated film was formed by alternately stacking film A of about 10 nm and film B of about 10 nm in the same vacuum chamber 201. This laminated film was then heat-treated at 300°C for 30 minutes. The composition ratio of film C after heat treatment is shown in Table 2. During the stacking of films A and B, the pressure when film A was formed was 0.1 Pa, and the pressure when film B was formed was 0.3 Pa.

As shown in Table 2, in the composition ratio of film C after heat treatment, it was confirmed that in all samples, the Al concentration was lower than that of film A, and the Cu concentration was lower than that of film B. This is thought to be because a reaction occurred between films A and B in film C. For example, the composition ratio of Al and Cu is close to the composition ratio of the CuAl alloy θ phase (33.3%:66.6%).

Figure 7(a) is a SEM image of the surface of film A after it was heat-treated at 300°C for 30 minutes, Figure 7(b) is a SEM image of the surface of film B after it was heat-treated at 300°C for 30 minutes, and Figure 7(c) is a SEM image of the surface of film C.

In the SEM image of film A shown in FIG. 7(a), relatively black portions 25 were observed. Elemental analysis of film A revealed that the Al concentration in portions 25 was higher than the Al concentration in other portions.

In the SEM image of film B shown in FIG. 7(b), relatively white portions 26 were observed. Elemental analysis of film B revealed that the Cu concentration in portions 26 was higher than the Cu concentration in other areas.

In contrast, in film C shown in FIG. 7(c), neither the black portion 25 nor the white portion 26 was observed.

(Example 2)

It was confirmed that the composition ratio of the CuAl alloy film changes by changing the bias power applied to the stage 204 during sputtering film formation. As samples, sample D, which has a content rate higher than that of the stoichiometric composition _CuAl2 , and sample E, which has a Cu content rate higher than that of the stoichiometric composition _CuAl2 , were prepared. The stoichiometric composition ratio of _CuAl2 was 33.33%:66.66%. The substrate was a Si substrate.

An example of the sputtering conditions for sample D is shown below.
Target: CuAl ₂ target Film formation pressure: 0.1 Pa
Substrate temperature: room temperature Discharge power: 0.48 W/ ^cm2
Stage bias power: 0 W
Discharge gas: Ar

An example of the sputtering conditions for sample E is shown below.
Target: CuAl ₂ target Film formation pressure: 0.1 Pa
Substrate temperature: room temperature Discharge power: 0.48 W/ ^cm2
Stage bias power: 50W
Discharge gas: Ar

The composition ratios of each are shown in Table 3. The concentrations were determined using elemental XRF analysis (AZX400, manufactured by Rigaku Corporation).

As shown in Table 3, by changing the bias power applied to the stage 204 using a _CuAl2 target, a film having an Al content greater than that of the stoichiometric composition _CuAl2 is formed in low bias deposition (0 W), and a film having a Cu content greater than that of the stoichiometric composition _CuAl2 is formed in high bias deposition (50 W).

(Example 3)

It was confirmed that the composition ratio of the CuAl alloy film changes by changing the power applied to each target in co-sputtering of an Al target and a Cu target. As samples, sample F, in which the Al content is higher than the Al content of the stoichiometric composition _CuAl2 , and sample G, in which the Cu content is higher than the Cu content of the stoichiometric composition _CuAl2 , were prepared. The stoichiometric composition ratio of _CuAl2 was 33.33%:66.66%. The substrate was a Si substrate.

An example of the sputtering conditions for sample F is shown below.
Target size: φ125mm
Gas pressure during film formation: 0.03 Pa
Al target input power: 1000 W
Cu target input power: 130 W

An example of the sputtering conditions for sample G is shown below.
Target size: φ125mm
Gas pressure during film formation: 0.03 Pa
Al target input power: 1000 W
Cu target input power: 140 W

The composition ratios of each are shown in Table 4. The concentrations were determined using elemental XRF analysis (AZX400, manufactured by Rigaku Corporation).

As shown in Table 4, by adjusting the power applied to each target by co-sputtering an Al target and a Cu target, a film having an Al content higher than the Al content of the stoichiometric composition _CuAl2 and a film having a Cu content higher than the Cu content of the stoichiometric composition _CuAl2 can be formed.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made. Each embodiment is not necessarily an independent form, and can be combined as far as technically possible.

In addition, the alloy containing Cu and Al according to this embodiment is not limited to a metal alloy having a stoichiometric ratio represented by the chemical formula CuAl ₂ , but also includes an alloy in which the ratio of the number of Cu and Al atoms is slightly deviated from 1: 2. Even when such an alloy having a slight deviation is used for metal wiring, no localized formation of Al particles is observed in the metal wiring, and there is no increase in the resistance of the metal wiring.

10...Interlayer insulating layer 11...Interlayer insulating layer 12...Metal wiring layer 20...Metal wiring 20A, 21A...Metal material 20C, 21C...Metal material 20L, 21L...Laminate 101...Surface 102...Opening 104...Inner wall 200A, 200B...Film forming apparatus 201...Vacuum vessel 202, 202A, 202C...Target 203...Power supply 204...Stage 205...Pressure gauge 206...Gas supply system 207...Gas flow meter 208...Exhaust system 210...Control device 211...Adhesion prevention plate 220...Substrate 300...Alloy layer 301...α phase

Claims (10)

A method for forming a metal wiring including a CuAl2 alloy on a substrate by irradiating a first metal material, which is a CuAl alloy and has an Al content greater than the Al content of stoichiometric composition _CuAl2 , and a _second metal material, which is a CuAl alloy and has a Cu content greater than the Cu content of stoichiometric composition _CuAl2 , on the substrate at least once under a reduced pressure atmosphere, the method comprising:
The first metal material and the second metal material are subjected to a heat treatment.
A method for forming metal wiring. 2. The method for forming metal wiring according to claim 1,
the first metal material and the second metal material are alternately incident on the substrate to form the metal wiring. 3. The method for forming metal wiring according to claim 1, further comprising the steps of:
forming the metal wiring by a sputtering method while heating the substrate. The method for forming a metal wiring according to any one of claims 1 to 3,
The method for forming metal wiring further comprises: causing the first metal material to be incident on the substrate under a reduced pressure atmosphere at a first pressure; and causing the second metal material to be incident on the substrate under a reduced pressure atmosphere at a second pressure different from the first pressure. The method for forming metal wiring according to claim 4,
The method for forming a metal wiring, further comprising setting the second pressure higher than the first pressure. The method for forming a metal wiring according to any one of claims 1 to 5,
a first metal material is deposited by applying a first bias power to the substrate, and a second metal material is deposited by applying a second bias power different from the first bias power to the substrate. The method for forming metal wiring according to claim 6,
The method for forming a metal wiring, further comprising: setting the first bias power higher than the second bias power. The method for forming a metal wiring according to any one of claims 1 to 7,
A method for forming a metal wiring, comprising the steps of: forming a metal wiring on a substrate by using a _CuAl2 alloy target as a film formation source for the metal wiring formed on the substrate; a vacuum vessel capable of maintaining a reduced pressure atmosphere;
a film formation source capable of emitting aluminum and copper toward a substrate;
a control device that controls a first metal material containing aluminum and copper, and a second metal material containing aluminum and copper and having a lower aluminum ratio and a higher copper ratio than the first metal material, to be incident on the substrate at least once each by changing the power applied to the film formation source. The film forming apparatus according to claim 9 ,
The control device is a film forming device that performs control so that the first metal material and the second metal material are alternately incident on the substrate.

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