JP7449790B2 - Metal wiring formation method and metal wiring structure - Google Patents

Description

The present invention relates to a method of forming metal wiring and a structure of metal wiring.

With the miniaturization of semiconductor devices, metal wiring patterns are becoming increasingly miniaturized. In manufacturing processes such as barrier film formation, seed layer formation, and Cu plating using the conventional dual damascene method, it is difficult to obtain good coverage characteristics for fine wiring patterns. Furthermore, as the wiring pattern becomes finer, the volume ratio of the barrier film in the metal wiring increases, which may increase the resistance of the metal wiring.

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

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

In the above-mentioned technology, it is desired to be able to form highly reliable wiring with good embedding characteristics each time even if the wiring pattern is becoming finer.

In view of the above circumstances, an object of the present invention is to provide a metal wiring forming method and a metal wiring structure that have good embedding characteristics and can form highly reliable 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 metal wiring containing copper and aluminum is placed inside the opening of an insulating layer in which an opening consisting of a groove or a hole is formed on the surface. Wiring is formed.
A metal layer having lower wettability for the metal wiring than for the metal wiring with respect to the insulating layer is formed at least at an opening end of the opening.
The metal wiring is formed inside the opening by forming the metal wiring on the surface of the insulating layer.

According to such a method of forming a metal wiring, it is possible to form a wiring with good embedding characteristics and high reliability.

In the method for forming the metal wiring, the insulating layer may be heated when forming the metal wiring.

According to such a method of forming a metal wiring, since the insulating layer and the metal layer are heated when forming the metal wiring, a wiring with good embedding characteristics and high reliability can be formed.

In the method for forming metal wiring, the metal layer is formed from a part of the inner wall of the opening that is connected to the opening end, and along the opening end and the surface of the insulating layer that is connected to the opening end. Good too.

According to such a method of forming a metal wiring, since the metal layer is formed in the above-mentioned portion, a wiring with good embedding characteristics and high reliability can be formed.

In the method for forming the metal wiring described above, a CuAl ₂ alloy may be used as the metal wiring.

According to such a method of forming a metal wiring, since a CuAl ₂ alloy is used as the metal wiring, a wiring with good embedding characteristics and high reliability can be formed.

In the above method for forming metal wiring, a layer containing at least one of W, WN, Ta, TaN, TiN, and Si may be used as the metal layer.

According to this method of forming metal wiring, since a layer containing at least one of W, WN, Ta, TaN, TiN, and Si is used as the metal layer, the embedding characteristics are good and the reliability is high. Wiring can be formed.

In the above method for forming metal wiring, an insulating layer containing silicon oxide may be used as the insulating layer.

According to such a method of forming a metal wiring, since an insulating layer containing silicon oxide is used as the insulating layer, a highly reliable wiring can be formed.

In the above method for forming metal wiring, after forming the metal wiring inside the opening, the insulating layer above a part of the inner wall, the metal layer formed above a part of the inner wall, and the metal The wiring may be removed.

According to such a method of forming a metal wiring, the metal layer is removed from a part of the insulating layer and a part of the metal wiring, so that a highly reliable wiring can be formed.

In order to achieve the above object, a metal wiring structure according to one embodiment of the present invention includes an insulating layer, a metal wiring, and a metal layer.
The insulating layer has openings formed in the form of grooves or holes formed on the surface thereof.
The metal wiring is provided inside the opening.
The metal layer is provided between the insulating layer and the metal wiring at least at an open end of the opening, and the metal wiring has a wettability with respect to the metal layer that is higher than a wettability with respect to the insulating layer of the metal wiring. low.

According to such a metal wiring structure, since the metal layer can be removed from part of the insulating layer and part of the metal wiring, a structure having highly reliable wiring can be formed. .

As described above, according to the present invention, there are provided a metal wiring forming method and a metal wiring structure that have good embedding characteristics and can form highly reliable wiring.

FIG. 2 is a schematic cross-sectional view illustrating a method for forming metal wiring according to the present embodiment. FIG. 2 is a schematic cross-sectional view illustrating a method for forming metal wiring according to the present embodiment. FIG. 3 is a schematic cross-sectional view showing a manufacturing process of a metal wiring according to a comparative example.

Embodiments of the present invention will be described below with reference to the drawings. In each drawing, XYZ axis coordinates may be introduced. In addition, the same members or members having the same function may be given the same reference numerals, and the description may be omitted as appropriate after the member has been described. Further, the numerical values shown below are just examples, and are not limited to these examples.

A method for forming metal wiring according to this embodiment will be described below. In this embodiment, a metal wiring containing copper and aluminum is formed inside an opening in an insulating layer having an opening formed in the surface thereof, which is a trench or a hole. As a component of the metal wiring, CuAl ₂ alloy is exemplified.

FIGS. 1(a) to 2(c) are schematic cross-sectional views illustrating the method for forming metal wiring according to this embodiment. 1(a) to 2(c) show electronic components (e.g., semiconductor elements) including transistors, resistors, capacitors, memories, etc. formed in an interlayer insulating layer when formed by a so-called wafer process. An example of a metal wiring manufacturing process is shown.

In FIG. 1A, an interlayer insulating layer 10 is illustrated as an insulating layer on which metal wiring is formed. An opening 102 consisting of a groove or a hole is formed in the 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 in FIG. 1(a). Further, when the opening 102 is a hole, the outer shape of the hole when viewed from the Z-axis direction is circular or rectangular. The hole may be a via hole or the like. The opening 102 in the interlayer insulating layer 10 may have a bottom or may be bottomless. In FIG. 1(a), a bottomless opening 102 is illustrated. That is, the opening 102 penetrates the interlayer insulating layer 10 in the Z-axis direction.

In the opening 102, the width w1 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 of a straight type, or may be of a tapered type in which the width becomes wider toward the bottom or conversely becomes narrower.

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 portion 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, a transistor, a resistor, a capacitor, a memory, or the like (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 the metal wiring layer 12 is replaced with an interlayer insulating layer 11. In this case, the interlayer insulating layer 11 will be 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 of 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). 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 with a dielectric constant of 3 or less (CVD-SiOC, CVD-SiO _{2 ,} etc.).

Next, as shown in FIG. 1B, a metal layer 20 is formed on the surface 101 at least at the opening end 103 of the opening 102. As shown in FIG. As the metal layer 20, a layer containing at least one of W, WN, Ta, TaN, TiN, and Si is used. The metal layer 20 is formed by, for example, a sputtering method under a reduced pressure atmosphere.

In forming the metal layer 20, the film forming conditions are set so that the step coverage of the metal layer 20 near the opening end 103 of the opening 102 is good. For example, the deposition conditions are set so that the upper part of the opening 102 is not closed by the metal layer 20 and the thickness of the metal layer 20 becomes more uniform.

Furthermore, during the formation of the metal layer 20, it is preferable to set conditions such that the surface 101 of the interlayer insulating layer 10 is less likely to be damaged by the sputtered particles of the metal layer 20. In view of these matters, the sputtering conditions for the metal layer 20 are set as follows. Note that the stage is a support stand of a film forming apparatus that supports the structure 1 shown in FIG. 1(b).

Discharge method: High frequency discharge (VHF band to RF band) or DC discharge Target input power: 0.2 W/cm ² or more and 4.0 W/cm ² or less Pressure in vacuum chamber: 0.01 Pa or more and 0.5 Pa or less Discharge gas: Ar
Stage temperature: Room temperature Stage bias: 0 W/cm ² or more and 0.7 W/cm ² or less Film thickness: 0.5 nm or more and 5 nm or less

The metal layer 20 is formed from a part of the inner wall 104 of the opening 102 that is connected to the opening end 103 and along the opening end 103 and the surface 101 of the interlayer insulating layer 10 that is connected to the opening end 103 . For example, the metal layer 20 is formed along the inner wall 104, the open end 103, and the front surface 101 from any position from the half of the depth t1 to the surface 101.

In FIG. 1B, as an example, the metal layer 20 is formed from a position approximately half the depth t1 from the surface 101 along the inner wall 104, the open end 103, and the surface 101. The metal layer 20 may be formed along the inner wall 104, the open end 103, and the surface 101 from a position 1/3 of the depth t1 from the surface 101, and from a position 1/4 of the depth t1 from the surface 101, Alternatively, it may be formed along the inner wall 104, the open end 103, and the surface 101 from the 1/5 position.

Furthermore, in this embodiment, a metal layer is formed as the metal layer 20, which has lower wettability for the metal wiring 30 than the interlayer insulating layer 10 for the metal wiring 30, which will be described later. The effect when such a metal layer 20 is used will be described later.

Next, as shown in FIG. 1C, a metal wiring 30 is formed on the surface 101 of the interlayer insulating layer 10. The metal wiring 30 is formed by, for example, a sputtering method under a reduced pressure atmosphere. Furthermore, in this embodiment, the stage is heated when forming the metal wiring 30, thereby forming the metal wiring 30 while heating the interlayer insulating layer 10 and the metal layer 20 using a heating sputtering method (dynamic reflow method). ) applies. The sputtering conditions are as follows.

Discharge method: DC discharge Target input power: 0.3 W/cm ² or more and 1.6 W/cm ² or less Pressure in vacuum chamber: 0.01 Pa or more and 0.5 Pa or less Discharge gas: Ar
Stage temperature: 200°C or more and 350°C or less Stage bias: 0 W/cm ² or more and 0.3 W/cm ² or less Film deposition rate: 0.1 nm/sec or more and 0.7 nm/sec or less Film thickness: 15 nm or more and 350 nm or less

The material of the metal wiring 30 is an intermetallic compound containing Cu and Al. For example, the material of the metal wiring 30 is CuAl ₂ alloy. CuAl ₂ alloy means an alloy having a θ layer of 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). Here, the wettability of the metal wiring 30 to the metal layer 20 is lower than the wettability of the metal wiring 30 to the interlayer insulating layer 10 . For example, the contact angle of the metal wiring 30 on the interlayer insulating layer 10 is smaller than the contact angle of the metal wiring 30 on the metal layer 20. As a result, during sputtering film formation, the metal wiring 30 is less likely to wet the metal layer 20 and is more likely to be repelled by the metal layer 20.

Furthermore, since the stage is heated within the above temperature range, the interlayer insulating layer 10 and the metal layer 20 are heated to a predetermined temperature. For example, the stage temperature corresponds to the temperature of the interlayer insulating layer 10 and the metal layer 20. Further, the metal wiring 30 is deposited on the surface 101 and the metal layer 20 while obtaining kinetic energy from sputtered particles during sputtering film formation. As a result, migration of the metal wiring 30 on the metal layer 20 is promoted during sputtering film formation.

As a result, the metal wiring 30 deposited on the surface of the interlayer insulating layer 10 does not remain on the metal layer 20 but easily flows down into the opening 102 (FIG. 2(a)), and the metal wiring 30 is deposited on the surface of the interlayer insulating layer 10. It is easily embedded not only on the surface 101 but also inside the opening 102. This state is shown in FIG. 2(b). As shown in FIG. 2(b), no gap is formed between the metal wiring 30 and the metal wiring layer 12, and the metal wiring 30 is electrically connected to the metal wiring layer 12 below. Ru.

Note that if the thickness of the metal layer 20 becomes thinner than 0.5 nm, the water-repellent effect of the metal wiring 30 on the metal layer 20 becomes weaker, which is not preferable. Furthermore, if the thickness of the metal layer 20 becomes thicker than 5 nm, there is a possibility that the metal layer 20 will block the upper part of the opening 102, which is not preferable.

Further, if the stage temperature is lower than 200° C., migration of the metal wiring 30 on the metal layer 20 during sputtering film formation becomes difficult to be promoted, which is not preferable. Further, if the stage temperature is higher than 350° C., crystallization of the metal wiring 30 is promoted and the surface roughness (for example, Ra) of the metal wiring 30 increases, which is not preferable. Alternatively, if the stage temperature is higher than 350° C., if the interlayer insulating layer 10 is made of a low-k material, the low-k material will be susceptible to thermal damage, which is not preferable.

Furthermore, if the pressure in the vacuum chamber during sputtering film formation is lower than 0.01 Pa, it is not preferable because the number of sputtered particles will be small and the total amount of kinetic energy received from the sputtered particles will be small. Moreover, if the pressure in the vacuum chamber during sputtering film formation becomes greater than 0.5 Pa, the number of collisions between sputtered particles increases and the kinetic energy of the sputtered particles themselves decreases, which is not preferable.

Moreover, it is preferable that the film formation rate of the metal wiring 30 is 0.1 nm/sec or more and 0.25 nm/sec or less. If the deposition rate of the metal wiring 30 is lower than 0.1 nm/sec, productivity tends to be poor, or if it is higher than 0.25 nm/sec, the characteristics of embedding the metal wiring 30 into the opening 102 tend to be poor.

Through such a manufacturing process, the metal wiring structure 1 shown in FIG. 2(b) is formed. The structure 1 shown in FIG. 2(b) includes an interlayer insulating layer 10, a metal wiring 30 provided inside the opening 102, and a connection between the interlayer insulating layer 10 and the metal wiring 30 at least at the opening end 103 of the opening 102. and a metal layer 20 provided therebetween. Note that after the structure 1 is formed, an after-reflow treatment (at 200° C. or higher and 350° C. or lower) may be performed as necessary.

After the metal wiring 30 is formed inside the opening 102, a CMP (Chemical Mechanical Polishing) process is performed as required, as shown in FIG. 2(c). For example, the interlayer insulating layer 10 above a portion of the inner wall 104 and the metal layer 20 and metal wiring 30 formed above the portion of the inner wall 104 are removed. For example, the interlayer insulating layer 10, the metal layer 20, and the metal wiring 30 above the half depth t1 from the surface 101 of the opening 102 are removed by CMP.

As a result, the metal layer 20 is removed from the structure 1 shown in FIG. 2(b) along with a portion of the interlayer insulating layer 10 and a portion of the metal wiring 30. After this, another metal wiring may be connected to the metal wiring 30, and an electrode pad or the like may be formed on the metal wiring 30.

FIG. 3 is a schematic cross-sectional view showing a manufacturing process of a metal wiring according to a comparative example.

In the comparative example, the metal layer 20 is not formed from the inner wall of the opening 102 to the opening end 103 and the surface 101, and the process is proceeding. Therefore, during sputtering film formation, the metal wiring 30 is difficult to flow toward the bottom of the opening 102, and a void 110 is formed under the metal wiring 30.

As another comparative example, during sputtering film formation of the metal wiring 30, the stage temperature was set to room temperature, the metal wiring 30 was formed on the surface 101 of the interlayer insulating layer 10, and then post-annealing (350°C, 30 min) was performed. There are examples of attempts. In this case, after the thick metal wiring 30 is once formed on the surface 101 of the interlayer insulating layer 10, an annealing treatment is performed thereafter. In such a case, since CuAl ₂ is an intermetallic compound, the fluidity of the metal wiring 30 was not good even if annealing treatment was performed after film formation, and voids were observed under the metal wiring 30.

An example of the effects of this embodiment will be described below.

When _CuAl2 material is used as the metal wiring 30, aluminum oxide is spontaneously formed at the interface between the metal wiring 30 and the interlayer insulating layer 10, and the aluminum oxide layer functions as a barrier layer for the metal wiring 30. do. As a result, it is not necessary to form a barrier layer between the metal wiring 30 and the interlayer insulating layer 10, and the bulk of the metal wiring 30 increases accordingly, realizing lower resistance of the metal wiring.

Furthermore, even if there is no barrier layer, the presence of the aluminum oxide layer between the metal wiring 30 and the interlayer insulation layer 10 provides excellent adhesion between the metal wiring 30 and the interlayer insulation layer 10. is obtained.

Further, since CuAl ₂ is an intermetallic compound, the bond between Cu and Al is relatively strong, and the diffusion coefficient with respect to the interlayer insulating layer 10 is small. Therefore, the metal wiring 30 is difficult to diffuse into the interlayer insulating layer 10 even without a barrier layer.

However, since CuAl ₂ is an intermetallic compound, the bond between Cu and Al is relatively strong. Therefore, CuAl ₂ has lower fluidity into the opening 102 during the film formation process than pure Cu. As a result, the narrower the width w2 of the opening 102 (for example, 20 nm or less), the worse the filling characteristics of CuAl ₂ tend to be.

On the other hand, in this embodiment, the CuAl ₂ material, which is the metal wiring 30, is reliably embedded in the opening 102 of the interlayer insulating layer 10 by using the heating sputtering method and the metal layer 20 and the action explained using the figures. I'm here.

Here, if the metal layer 20 is a material that easily diffuses into the interlayer insulating layer 10 than the metal wiring 30, in a structure in which the metal layer 20 is formed between the metal wiring 30 and the interlayer insulating layer 10, the metal Layer 20 may diffuse into interlayer dielectric layer 10 . Further, since the metal wiring 30 has weak wettability with respect to the metal layer 20, the adhesion between the metal wiring 30 and the metal layer 20 is weaker than the adhesion between the metal layer 20 and the interlayer insulating layer 10. Therefore, there is a concern that the metal wiring 30 and the metal layer 20 may peel off.

In this embodiment, the metal layer 20 is used when the metal wiring 30 is embedded in the opening 102, and after the metal wiring 30 is embedded in the opening 102, the metal layer 20 is used as a part of the interlayer insulating layer 10 and the metal layer 20. It is possible to remove it from the structure 1 together with a part of the wiring 30. This is because the metal layer 20 is formed from a portion of the inner wall 104 of the opening 102 to the opening end 103 and along the surface 101 of the interlayer insulating layer 10 .

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways. Each embodiment is not necessarily an independent form, and can be combined to the extent technically possible.

DESCRIPTION OF SYMBOLS 1... Structure 10... Interlayer insulation layer 11... Interlayer insulation layer 12... Metal wiring layer 20... Metal layer 30... Metal wiring 101... Surface 102... Opening 103... Opening end 104... Inner wall

Claims (8)

A method of forming a metal wiring containing copper and aluminum inside an opening of an insulating layer having an opening constituted by a groove or a hole formed on the surface thereof, the method comprising:
From a part of the inner wall of the opening that is connected to the opening end of the opening, along the opening end and the surface of the insulating layer that is connected to the opening end, the metal wiring is lower than the wettability of the metal wiring with respect to the insulating layer. forming a metal layer with low wettability,
A method for forming a metal wiring, comprising forming the metal wiring inside the opening by depositing the metal wiring on the metal layer while heating the metal wiring. A method for forming a metal wiring according to claim 1, comprising:
The metal layer is not formed at the bottom of the opening.
How to form metal wiring. A method of forming a metal wiring containing copper and aluminum inside an opening of an insulating layer having an opening constituted by a groove or a hole formed on the surface thereof, the method comprising:
The metal wiring is not formed at the bottom of the opening, but is formed from a part of the inner wall of the opening that is connected to the opening end of the opening to the opening end, and along the surface of the insulating layer that is connected to the opening end. forming a metal layer whose wettability for the metal wiring is lower than wettability for the insulating layer ;
forming the metal wiring inside the opening by forming the metal wiring on the metal layer;
How to form metal wiring. A method for forming a metal wiring according to any one of claims 1 to 3, comprising:
A method for forming a metal wiring, in which a CuAl ₂ alloy is used as the metal wiring. A method for forming a metal wiring according to any one of claims 1 to 4, comprising:
A method for forming a metal wiring, in which a layer containing at least one of W, WN, Ta, TaN, TiN, and Si is used as the metal layer. A method for forming a metal wiring according to any one of claims 1 to 5, comprising:
A method for forming a metal wiring, using an insulating layer containing silicon oxide as the insulating layer. A method for forming a metal wiring according to any one of claims 1 to 6, comprising:
After the metal wiring is formed inside the opening, the insulating layer above a part of the inner wall and the metal layer and the metal wiring formed above from a part of the inner wall are removed. an insulating layer with an opening formed on its surface consisting of a groove or a hole;
a metal wiring provided inside the opening;
The insulating layer and the metal are not formed at the bottom of the opening, but extend from a part of the inner wall of the opening that is connected to the opening end of the opening to the opening end and the surface of the insulating layer that is connected to the opening end. and a metal layer provided between the metal wiring and the metal wiring, the metal layer having a lower wettability for the metal wiring than the wettability of the metal wiring for the insulating layer.

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