JPH0653332A - Forming method for metallic plug - Google Patents

Abstract

PURPOSE:To provide a barrier metal in a good embedded state even at a contact hole having a high aspect ratio along with good barrier characteristics between a wiring layer and a lower semiconductor. CONSTITUTION:A contact hole 3 is opened in an insulating layer 2 on a semiconductor substrate 1, and a wiring layer is embedded after a barrier metal made up of a refractory metallic layer 4 and/or a refractory metallic alloy compound layer 5a is formed at a contact hole 3. An impurity plasma beam with a directional characteristic is cast, as indicated by an arrow (p), on the refractory metallic layer 4 and/or the refractory metallic alloy compound layer 5a. Then, an impurity is implanted at least into an intergranular part of the refractory metallic layer 4 and/or the refractory metallic alloy compound layer 5a at a bottom part of the contact hole 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal plug in a connecting portion between a semiconductor layer and a wiring layer of various semiconductor devices.

[0002]

2. Description of the Related Art At present, as a method of burying a micro contact hole of a VLSI, a so-called high temperature Al sputtering method utilizing surface fluidity of Al at high temperature, and a step coverage superior to this sputtering method and superior to Al are used. A method of depositing W having high temperature heat resistance by a CVD (chemical vapor deposition) method is typically adopted.

In the high temperature Al sputtering method, it is necessary to previously form a barrier metal such as TiN in order to prevent the reaction between Al and the Si substrate. As this barrier metal, T
TiON, which prevents Al from diffusing in the grain boundary of TiN, is excellent in a state where oxygen is clogged in the grain boundary of iN and is stuffed.

On the other hand, in the high temperature Al sputtering method, since the surface fluidity of Al is utilized as described above, the wettability between Al and the underlying barrier metal is improved so that a large amount of Al flows into the contact hole. It is important to. Ti and TiN easily react with Al and have a poor barrier property, but have excellent wettability with Al and have good embedding characteristics. On the other hand, TiON has an excellent barrier property against Al, but has poor wettability with Al and has a problem that Al is difficult to be embedded in a contact hole having a high aspect ratio.

Therefore, when embedding the Al wiring layer,
In order to secure wettability and barrier properties, it is desirable to have a Ti / TiON / Ti barrier structure in which Ti layers are provided above and below via TiON. Since TiON and Ti are currently deposited by the sputtering method, the upper layer side has a smaller film thickness than the lower layer side in the side wall portion of the contact hole 3, and the upper Ti layer has oxygen from the intermediate TiON layer. Oxidation may deteriorate the wettability with Al and deteriorate the embedding characteristics.

In order to prevent this, if the thickness of the upper Ti layer is made large, in the case of a sub-half micron fine contact hole, for example, as shown in FIG. As a result, the embedding property of Al becomes disadvantageous. In FIG. 6, 1 is a semiconductor substrate such as Si, and 2 is SiO formed by a CVD method or the like.
Insulating layers such as ₂ and 3 are contact holes formed by photolithography or the like, 21 to 23 are Ti layers,
A TiON layer and a Ti layer are shown.

Therefore, it is strongly desired to form Ti and TiON by a CVD method with excellent coverage.
Ti is produced by various CVD methods by various equipment manufacturers.
Attempts have been made to deposit N and Ti, but at present, TiN,
Only ECR (electron cyclotron resonance) plasma CVD method can form a film together with Ti.

However, in the ECR plasma CVD method, the plasma contributing to the reaction is extracted in the vertical direction by the divergent magnetic field, so that the amount of the vertical component deposited increases and the film on the bottom of the contact hole becomes thicker, but the film on the side wall does not. It becomes thin. Therefore, as in the sputtering method, T
When the i / TiON / Ti structure is formed, the upper Ti layer 23 of the side wall becomes thin, and as shown by hatching in FIG.
The iON layer 22 may be oxidized by oxygen and low contact resistance may not be obtained.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a barrier metal which has a good embedding property of a wiring layer even in a contact hole having a high aspect ratio and which has an excellent barrier property between the wiring layer and the semiconductor below. Provided is a method for forming a metal plug capable of forming a metal plug.

[0010]

According to the present invention, a wiring layer is buried after a barrier metal composed of a refractory metal layer and / or a refractory metal compound layer is formed in a contact hole opened in an insulating layer on a semiconductor substrate. In the method for forming a metal plug to be embedded, as shown in a process chart of an example thereof, a high-melting-point metal layer 4 and / or a high-melting-point metal compound layer 5a is directed to an impurity plasma as indicated by an arrow p. To irradiate the grain boundaries of the refractory metal layer 4 and / or the refractory metal compound layer 5a at the bottom of the contact hole 3 with impurities.

Further, according to the present invention, oxygen, nitrogen or boron is used as an impurity in the above-mentioned method for forming a metal plug.

[0012]

As described above, according to the present invention, the refractory metal layer 4 and the refractory metal compound layer 5a deposited in the contact hole 3 by ECR plasma CVD or the like, for example, the refractory metal compound layer 5a such as TiN, By irradiating the impurity plasma with an increased vertical component, the contact hole 3
The refractory metal compound layer 5a at the bottom of the layer can be irradiated with more impurities to fill the grain boundaries and so-called stuffing. That is, it is possible to form the barrier metal having different impurity concentrations in the side wall portion and the bottom portion, excellent in wettability with the wiring layer such as Al in the side wall portion, and excellent in barrier property in the bottom portion.

Further, in the present invention, by using oxygen, nitrogen or boron as an impurity, the side wall of the contact hole is surely excellent in wettability with the Al wiring layer, and the bottom has a barrier property which does not react with the wiring layer. An excellent barrier metal can be formed.

Therefore, according to the present invention, it is possible to form a metal plug having a good embedding property and an excellent barrier property even in a fine contact hole having a high aspect ratio.

[0015]

EXAMPLE In this example, a case where a barrier metal having a Ti / TiON / Ti structure is formed to form a metal plug when an Al wiring layer is embedded in a contact hole having a high aspect ratio by a high temperature Al sputtering method is described. Show.

Example 1 First, as shown in FIG. 1A, a thick insulating layer 2 having a thickness of, for example, 800 nm is formed on a semiconductor substrate 1 made of silicon or the like by a CVD method or the like, and is diffused at a predetermined position of the semiconductor substrate 1. A contact hole 3 having a diameter of 0.4 μm, that is, an aspect ratio of 2 is opened on the layer (not shown) by applying photolithography or the like. Then, for example, the ECR plasma CV is entirely included including the inside of the contact hole 3.
By the D method, a refractory metal layer 4 of Ti or the like having a thickness of 30 nm and a refractory metal compound layer 5a of TiN or the like having a thickness of, for example, 100 nm are sequentially formed.

In this case, the conditions for depositing Ti are as follows: the temperature is 540 ° C., the flow rate of TiCl ₄ is 10 to 15 sccm, and H is
Flow rate of ₂ is 50 sccm, microwave power is 2.8 k
W. In addition, the TiN deposition conditions include a temperature of 54
At 0 ° C., the TiCl ₄ flow rate was 10 to 15 sccm, the N ₂ flow rate was 15 sccm, the H ₂ flow rate was 50 sccm, and the microwave power was 2.8 kW.

Next, a plasma CV which is the same as or different from the deposition apparatus for the refractory metal 4 and the refractory metal compound layer 5a described above.
In device D, oxygen gas was injected into the plasma chamber to perform EC
Oxygen plasma is generated by the R discharge, and as shown by an arrow p in FIG. 1B, the oxygen plasma is irradiated with directivity, that is, in a direction perpendicular to the surface of the semiconductor substrate 1 in this case, and the bottom portion of the contact hole 3 and Oxygen or a compound of oxygen and titanium TiO _x , TiO
Staff _X N _y . Since TiN has a columnar crystal structure, by stuffing impurities such as oxygen and boron in the grain boundaries, it is possible to suppress the diffusion of the wiring layer material such as Al into the grain boundaries of TiN. The barrier property can be improved.

In this case, since the oxygen plasma is irradiated with directivity as described above, the oxidation of the TiN refractory metal compound layer 5a on the side surface of the contact hole 3 is suppressed. Therefore, as shown by hatching in FIG. 1C, oxygen is stuffed at a high concentration at the bottom of the contact hole 3 to have a high barrier property, and oxidation is suppressed at the side wall part, resulting in good wettability with Al. It is possible to form the TiON refractory metal compound layer 5 formed as follows.

FIG. 2 shows a schematic view of an example of such a plasma CVD apparatus. Reference numeral 11 is a CVD reaction chamber, and a plasma chamber 12 is provided above the reaction chamber through an opening of a predetermined size. An oxygen gas introduction space 13 and a microwave introduction space 14 are provided above the plasma chamber 12,
Oxygen gas and microwave are introduced respectively as indicated by arrows o and m. In addition, the wafer 1 is placed under the reaction chamber 11.
A mounting table 16 of No. 5 is provided, and a high frequency power source 17 for applying a high frequency bias magnetic field is provided below the mounting table 16. 18 is an exhaust port.

In such an apparatus, the oxygen plasma generated by the ECR discharge is drawn from the plasma chamber 12 to the lower reaction chamber 11 by the divergent magnetic field, and the oxygen plasma is deposited on the wafer 15, that is, on the wafer 15. It is vertically incident on the TiN refractory metal compound layer 5a. Therefore, much oxygen is stuffed at the bottom of the contact hole, and oxidation can be suppressed at the side wall. In this example, plasma irradiation was performed under the conditions of oxygen plasma irradiation of oxygen of 50 sccm, microwave power of 1.5 kW and pressure of 0.01 Pa.

Since the incorporation of oxygen into the TiN refractory metal compound layer can occur even by exposure in the atmosphere, the incorporation of oxygen into the TiN film, that is, the grain size, can be achieved even during the oxygen plasma irradiation of this method. Can be fully staffed to the world.

Further, in this example, the active oxygen plasma was directionally irradiated only by the divergent magnetic field without applying the bias to the semiconductor substrate 1, but in order to further enhance this effect, the bias magnetic field is applied to the substrate 1. You can also In addition, various means such as a collimator that can be used under reduced pressure or vacuum can be used.

Then, as shown in FIG. 3A, a refractory metal layer 6 of Ti or the like is formed on the refractory metal compound layer 5 by EC.
The R plasma CVD method or the like is applied to have a thickness of about 50 nm. As the deposition conditions, the temperature was 540 ° C., TiCl
₄ flow rate of 10 to 15 sccm, H ₂ flow rate of 50 sccc
m, and the microwave power was 2.8 kW. Further, at this time, in order to prevent the oxidation of Ti, the deposition of Ti is performed by a device different from the device irradiated with oxygen plasma, or when the same device is used, Ti is deposited after sufficient exhaustion.

Then, as shown in FIG. 3B, an Al wiring layer 7 is buried and formed on the entire surface by a high temperature Al sputtering method or the like. DC sputtering power source 10.5
kW, temperature 480 ° C. to 500 ° C., pressure 0.4 Pa, Al
The gas flow rate was 100 sccm. At this time, since the amount of oxygen stuffing in the refractory metal compound layer 5 on the side wall is small, the oxidation of the Ti refractory metal layer 6 in the upper layer is suppressed, good wettability of Al can be secured, and the Al burying property is improved. A metal plug having low contact resistance and low leakage current can be formed.

Embodiment 2 Next, another embodiment according to the present invention will be described in detail with reference to FIGS. 4A to 4C and FIGS. 5A and 5B. First, as shown in FIG. 4A, a thick insulating layer 2 having a thickness of, for example, 800 nm is formed on a semiconductor substrate 1 made of silicon or the like by a CVD method or the like, and is formed on a diffusion layer (not shown) at a predetermined position of the semiconductor substrate 1. Similarly to the first embodiment, a contact hole 3 having a diameter of 0.4 μm and an aspect ratio of 2 is formed by applying photolithography or the like. Then, for example, the ECR plasma CV is entirely included including the inside of the contact hole 3.
By the D method, a refractory metal layer 4 of Ti or the like having a thickness of 30 nm and a refractory metal compound layer 5a of TiN or the like having a thickness of, for example, 100 nm are sequentially formed. The deposition conditions were the same as in Example 1 above, that is, the Ti deposition conditions were:
Temperature 540 ° C., TiCl ₄ flow rate 10-15 scc
The flow rate of m and H ₂ was 50 sccm, and the microwave power was 2.8 kW. Further, as the TiN deposition conditions,
Temperature 540 ° C., TiCl ₄ flow rate 10-15 scc
m, flow rate of N ₂ is 15 sccm, flow rate of H ₂ is 50 sccm
cm and the microwave power was 2.8 kW.

Next, the TiN refractory metal compound layer 5A is formed on the TiN refractory metal compound layer 5A by using the apparatus described in FIG.
As indicated by an arrow p in B, oxygen plasma is irradiated with directivity, that is, in a direction perpendicular to the surface of the semiconductor substrate 1, and oxygen or a compound of oxygen and titanium is introduced into the TiN grain boundary at the bottom of the contact hole 3. TiO _x , Ti
O _X N _y is stuffed and the wiring layer material such as Al is TiN
It is possible to improve the barrier property of TiN by suppressing the diffusion of the grain boundaries of TiN.

Also in this case, since the oxygen plasma is irradiated with directivity as described above, the TiN refractory metal compound layer 5 on the side wall of the contact hole 3 is formed.
Oxidation of a is suppressed, and Ti that has good wettability with Al
The ON refractory metal compound layer 5 can be formed.

Then, as shown in FIG. 5A, a refractory metal layer 16 such as W is deposited on the refractory metal compound layer 5 by LP.
A film is formed to a thickness of about 50 nm by (low pressure) CVD method or the like to form a barrier metal having a W / TiON / Ti laminated structure. As film forming conditions, the temperature is 450 ° C., the flow rate of WF ₆ is 95 sccm, the flow rate of H ₂ is 550 sccm, and the pressure is 1.
It was set to × 10 ⁴ Pa.

Then, as shown in FIG. 5B, an Al wiring layer 7 is buried over the entire surface by a high temperature Al sputtering method or the like. DC sputtering power source 10.5
kW, temperature 480 ° C. to 500 ° C., pressure 0.4 Pa, Al
The gas flow rate was 100 sccm. In this case, since the oxide of W has a higher free energy of formation than the oxide of Ti,
The W refractory metal layer 16 is superior in oxidation resistance to Ti, and in combination with the fact that oxygen is less taken in from the refractory metal compound layer 5 on the side wall, better wettability of Al is secured. Therefore, it is possible to form a metal plug having a low contact resistance and a low leak current while improving the Al burying property.

Also in this case, the directivity can be further improved by applying a bias to the substrate as in the first embodiment, and the impurities can be effectively implanted. Alternatively, various means such as a collimator can be used.

Although oxygen O was stuffed into the TiN refractory metal compound in each of the above-mentioned embodiments, the TiN contains N.
The same effect can be obtained by stuffing and B with directivity. Further, for example, the present invention can be applied to the case of stuffing Ti with N or B.

Further, in each of the above-mentioned examples, the case where the present invention is applied to the example in which the contact hole is provided on the diffusion layer of the Si semiconductor substrate has been described. It goes without saying that the method of the present invention can be applied to the formation of metal plugs in various semiconductor devices.

Further, it is needless to say that the present invention is not limited to the above-mentioned embodiment, and various modifications and changes can be made in the material constitution, apparatus constitution, film forming conditions and the like.

[0035]

As described above, according to the method of forming a metal plug of the present invention, the barrier property between the wiring layer material and the semiconductor substrate material is excellent at the bottom of the contact hole and the wettability of the wiring layer material at the side wall portion. In addition, a metal plug can be formed with a good filling property even in a contact hole having a high aspect ratio, and a low contact resistance and a reduction in leak current can be achieved.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of an example of a method for forming a metal plug of the present invention.

FIG. 2 is a schematic diagram of an example of a plasma CVD apparatus.

FIG. 3 is a manufacturing process diagram of an example of a method for forming a metal plug of the present invention.

FIG. 4 is a manufacturing process diagram of another example of the method for forming the metal plug of the present invention.

FIG. 5 is a manufacturing process diagram of another example of the method for forming a metal plug of the present invention.

FIG. 6 is a manufacturing process diagram of an example of a conventional metal plug forming method.

FIG. 7 is a manufacturing process diagram of another example of the conventional method for forming a metal plug.

[Explanation of symbols] 1 semiconductor substrate 2 insulating layer 3 contact hole 4 refractory metal layer 5 refractory metal compound layer 6 refractory metal layer 7 wiring layer

Claims (2)

[Claims] 1. A method for forming a metal plug in which a wiring layer is embedded after a barrier metal composed of at least a refractory metal layer and / or a refractory metal compound layer is formed in a contact hole opened in an insulating layer on a semiconductor substrate. Irradiating the refractory metal layer and / or the refractory metal compound layer with impurity plasma in a directed manner, and at least the grain boundaries of the refractory metal layer and / or the refractory metal compound layer at the bottom of the contact hole. A method for forming a metal plug, characterized in that the metal plug is filled with impurities. 2. The method for forming a metal plug according to claim 1, wherein oxygen, nitrogen or boron is used as the impurity.