JP4855455B2 - Copper thin film manufacturing method and sputtering apparatus used in the method - Google Patents

Description

  The present invention relates to the technical field of sputter deposition, and more particularly to the technical field of sputtering a copper or copper-based target to form a copper thin film.

  In recent years, a copper thin film having a small specific resistance has attracted attention as a wiring material for semiconductor devices in place of an aluminum thin film.

  Reference numeral 101 in FIG. 4A denotes a silicon substrate constituting a semiconductor device, and a silicon oxide film 102 is formed on the surface thereof.

  This silicon substrate 101 is carried into a sputtering apparatus, an argon gas plasma is generated, a target made of copper is sputtered, a copper thin film is formed on the silicon oxide film 102, and patterned to form a copper wiring 105 ( FIG. 4 (b)).

  Thus, the specific resistance of the copper wiring 105 formed by the sputtering film forming method is about 2.2 μΩcm, which is larger than the specific resistance of 1.7 μΩcm in the bulk state of copper.

When a copper thin film is formed by a sputtering apparatus, it is known that if the copper thin film is annealed in hydrogen, the specific resistance of the copper thin film immediately after formation can be reduced, but it is only reduced to about 1.9 μΩcm. It is enough.

In addition, in order to perform the annealing process, an apparatus for the annealing process is required in addition to the sputtering apparatus, and there is a problem that the cost is increased.
Japanese Patent Laid-Open No. 50-074534

  The present invention was created in order to solve the above-described disadvantages of the prior art, and an object thereof is to provide a low-resistance copper thin film.

  The inventors of the present invention generate a sputtering gas plasma, sputter a copper or copper-based target, and form a copper thin film on the surface of the film formation object. It has been found that when a small amount is introduced, the specific resistance of the formed copper thin film decreases with the passage of time after film formation.

In particular, in the case of a copper thin film sputtered with an additive gas having a partial pressure of 5 × 10 ⁻⁷ Torr (6.65 × 10 ⁻⁵ Pa), the ratio is almost equal to that of copper in a bulk state after 10 hours after film formation. I found the resistance to drop.

The present invention was created based on the above knowledge, and the invention according to claim 1 introduces a sputtering gas into a vacuum atmosphere, sputters copper or a copper-based target, A copper thin film manufacturing method for forming a copper thin film or a thin film containing copper as a main component on the surface of an object to be deposited placed on the surface of the film, wherein when sputtering the target, a gas having nitrogen atoms in the structure and oxygen An additive gas composed of at least one of a gas having an atom and a gas having a nitrogen atom and an oxygen atom is not less than 2.66 × 10 ⁻⁵ Pa and not more than 6.65 × 10 ⁻⁵ Pa. It introduce | transduces in the said vacuum atmosphere by the partial pressure of.
Invention of Claim 2 is a copper thin-film manufacturing method of Claim 1, Comprising: Said additive gas contains at least any 1 type or more gas among oxygen gas, nitrogen gas, and water. Features.
Invention of Claim 3 is a copper thin-film manufacturing method of any one of Claim 1 or Claim 2, Comprising: The said addition gas is introduce | transduced intermittently, It is characterized by the above-mentioned.
Invention of Claim 4 has a vacuum tank and the target which has copper or copper as a main component arrange | positioned in the said vacuum tank, makes the inside of the said vacuum tank a vacuum atmosphere, introduce | transduces sputtering gas, A sputtering apparatus for sputtering a target and forming a thin film on the surface of a film formation target disposed in the vacuum atmosphere, wherein the vacuum tank is provided with a gas addition pipe, and in the atmosphere of the sputtering gas, An additive gas composed of at least one of a gas having a nitrogen atom in the structure, a gas having an oxygen atom, or a gas having a nitrogen atom and an oxygen atom is 2.66 × 10 ^−5. characterized in that it is configured to allow continuous or pulse introduced at 6.65 × 10 ^-5 Pa or less of the partial pressure than Pa.

  The present invention is configured as described above, and an sputtering gas such as an argon gas contains an additive gas containing nitrogen atoms, oxygen atoms, or both atoms in the chemical structure at a predetermined partial pressure. Plasma of gas and additive gas is generated to sputter a target mainly composed of copper.

The introduction amount of the additive gas as described above is preferably controlled using a flow rate control valve provided in the gas addition pipe, and the partial pressure is preferably 1.33 × 10 ⁻⁴ Pa or less.

  When controlling with a flow control valve, it is difficult to make it smaller than the partial pressure corresponding to the minimum control flow. Therefore, when the additive gas is introduced via the flow control valve, the introduction and the stop thereof are repeated and introduced intermittently, so that the effective partial pressure value (time average value) of the additive gas is calculated as the flow control valve. It can be made smaller than the value that can be controlled by Moreover, the composition of the film interface can be controlled by the timing of intermittent introduction.

Since the specific resistance of the copper thin film can be reduced, it is suitable for LSI wiring.
When the additive gas is introduced intermittently, the partial pressure value can be made smaller than the value controllable by the flow control valve.
After the copper thin film is formed, the specific resistance can be reduced without annealing.

The sputtering apparatus of this invention is demonstrated with the copper thin film manufacturing method of this invention.
Referring to FIG. 1, reference numeral 1 is an example of the sputtering apparatus of the present invention, and has a vacuum chamber 10. A cathode device 12 is disposed on the bottom wall side of the vacuum chamber 10, and a substrate holder 13 is disposed on the ceiling side.

  The cathode device 12 has a cathode electrode 22, and a target 21 made of copper is horizontally provided on the surface (inside of the vacuum chamber 10). The target 21 is disposed at a position facing the substrate holder 13.

  A magnetron magnet 23 that forms a magnetic field on the surface of the target 21 is disposed on the back surface of the cathode electrode 22 (outside of the vacuum chamber 10). The distance (T / S) between the target 21 and the substrate 15 is so-called long throw sputtering (LTS) of 275 mm.

A rotating shaft 16 is inserted in the bottom wall of the vacuum chamber 10 in an airtight manner, and a shutter 17 is attached to a tip portion thereof.
A claw 14 is provided on the substrate holder 13, and a silicon substrate 15 is held by the claw 14 on the surface of the substrate holder 13 on the target 21 side.

A vacuum exhaust system 18 is connected to the vacuum chamber 10, and when the copper thin film is formed by the sputtering apparatus 1, the vacuum chamber 10 is evacuated by the vacuum exhaust system 18.
A gas introduction system 3 having a gas addition pipe 31 and a sputter gas introduction pipe 33 is connected to the vacuum chamber 10.

  The gas addition pipe 31 is provided with a flow rate control valve 32, and an end thereof is open to the atmosphere. The sputter gas introduction pipe 33 is connected to the sputter gas cylinder 37 via the mass flow controller 36 so that the sputter gas (in this case, argon gas) filled in the sputter gas cylinder 37 can be introduced into the vacuum chamber 10. It is configured.

After the inside of the vacuum chamber 10 is evacuated to a pressure of 4 × 10 ⁻⁶ Torr to 2 × 10 ⁻⁷ Torr by the vacuum exhaust system 18, the flow rate control valve 32 is operated, and the atmosphere (air) in the vacuum chamber 10 is operated. Is introduced as an additive gas.

At this time, without introducing the sputtering gas, the pressure in the vacuum chamber 10 is increased by the introduced additive gas, and when the sputtering gas is stabilized at a predetermined partial pressure (for example, a partial pressure of 5 × 10 ⁻⁷ Torr), Introduce.

  The sputtering gas is introduced while controlling the flow rate by the mass flow controller 36 (in this case, it is introduced at a flow rate of 20 sccm). At this time, the introduction amount of the additive gas is not changed.

When the sputtering gas is introduced, the pressure in the vacuum chamber 10 rises, and when the pressure is stabilized at a pressure of 5 × 10 ⁻⁴ Torr, a negative voltage is applied to the cathode electrode 22 to generate plasma near the surface of the target 21.

  In this state, the shutter 17 is disposed between the silicon substrate 15 and the target 21 and is discharged for 5 minutes × 2 times (2 minutes of discharge for 2 minutes between 3.7 kW (about 518 V × 7.18 A)). Pre-sputtering (setting a resting state), cleaning the surface of the target 21, and then rotating the rotating shaft 16, withdrawing the shutter 17 from between the silicon substrate 15 and the target 21, and starting sputtering after 2 minutes, A copper thin film begins to be formed on the surface of the silicon substrate 15 (sputtering power is 3.17 kW).

  Sputtering was performed for 80 seconds, and after forming a copper thin film of about 2000 mm on the surface of the silicon substrate 15, the voltage application to the cathode electrode 21 was stopped, the introduction of the additive gas (atmosphere) and the introduction of the sputtering gas were stopped. End. The temperature of the substrate holder 13 was 30 ° C. before the start of pre-sputtering, but was raised to about 50 ° C. at the end of sputtering.

  After the completion of sputtering, the silicon substrate 15 was taken out and the specific resistance of the formed copper thin film was measured. The value of the specific resistance decreased with time.

The graph of FIG. 2 shows the change over time in the partial pressure P in the sputtering gas of the additive gas (in this case, the atmosphere) introduced into the vacuum chamber 10 and the specific resistance of the formed copper thin film. The flow rate of the introduced sputtering gas is 20 sccm, and the pressure in the sputtering atmosphere is 5 × 10 ⁻⁴ Torr. The partial pressure P of the additive gas is represented by the difference (P ₁ −P ₀ ) between the ultimate pressure P ₀ of the vacuum chamber 10 before the additive gas is introduced and the pressure P ₁ after the additive gas is introduced.
The bulk copper in the graph is a specific resistance value in the case of a copper lump.

From this graph, it can be seen that it is effective to set the partial pressure P of the additive gas (atmosphere) contained in the sputtering atmosphere to 6.65 × 10 ⁻⁵ Pa (5 × 10 ⁻⁷ Torr) or less. . In particular, when the microscopic size is 2.66 × 10 ⁻⁵ Pa (2 × 10 ⁻⁷ Torr) or less, the specific resistance of the formed copper thin film is 1.7 to 1.8 μΩcm, which is the value of bulk copper ( It can be seen that it is approximately equal to 1.7 μΩcm). Similar results were obtained even when a substrate having a thermal oxide film formed on the silicon surface was used.

  As described above, the additive gas is continuously introduced into the vacuum chamber 10 by the flow rate control valve 32. However, in order to make the partial pressure P of the additive gas in the vacuum chamber 10 smaller, it is intermittently introduced. can do.

  For example, an additive gas is intermittently added to the vacuum chamber 10 at predetermined time intervals (this additive gas is a gas having an oxygen atom in its chemical structure, a gas having a nitrogen atom, a gas having an oxygen atom and a nitrogen atom, and water). When a very small amount of any one or more gases is introduced, the partial pressure can be further reduced.

The graph of FIG. 3 shows the pressure change in the vacuum chamber 10 when the additive gas introduction for 2.5 seconds is repeated at intervals of 14 seconds. By introducing the additive gas, the pressure in the vacuum chamber 10 is increased by 2.66 × 10 ⁻⁵ Pa (2 × 10 ⁻⁷ Torr) in a pulse manner.

When this graph is averaged, the vacuum chamber 10 contains the additive gas at a partial pressure of about 1 × 10 ⁻⁸ to 1 × 10 ⁻⁹ Torr. Although it is difficult to accurately introduce the additive gas having a minute partial pressure, it can be achieved by intermittently introducing the additive gas as described above.

  In addition, a pipe for continuously introducing the additive gas into the vacuum chamber 10 and a pipe for introducing the additive gas in a pulsed manner are separately provided to continuously introduce the additive gas and superimpose the pulsed introduction. You may let them.

  In the above, the case where the target is sputtered by applying a DC power source has been described. However, the present invention relates to an RF sputtering method in which an AC voltage is applied, a sputtering method in which an AC voltage is superimposed on a DC voltage, and the magnitude of the DC voltage. The present invention can be applied to various sputtering methods such as a sputtering method for changing the thickness. Alternatively, a voltage may be applied to the substrate holder 13 to apply a bias to the silicon substrate 15 or to float.

In addition, air (air) is used as the additive gas, but oxygen gas, nitrogen gas, or argon gas containing moisture may be used. It may be a mixed gas of oxygen gas and nitrogen gas. Further, oxygen gas, nitrogen gas, or a gas containing water in the mixed gas may be used.
In that case, the end of the gas addition pipe may be connected to a gas cylinder filled with the additive gas via a flow rate control valve.

  Moreover, although the above described formed the copper thin film on the silicon substrate 15, the film-forming target object is not limited to a silicon substrate.

  Furthermore, the copper target used in the present invention is a target made of copper or a target mainly composed of copper, and the target mainly composed of copper may contain other metals.

  Further, annealing may be used in combination in order to promote resistance reduction. Although an example in which the distance between the target and the substrate is 275 mm is shown, a shorter-distance sputtering apparatus may be used.

The figure which shows the sputtering device of an example of this invention Graph showing the change over time in the resistivity of copper thin film Graph showing pressure change when additive gas is introduced intermittently (a), (b): The figure for demonstrating the formation method of a copper thin film

Explanation of symbols

1 …… Sputtering equipment 10 …… Vacuum chamber 21 …… Target 31 …… Pipe for gas addition

Claims (4)

A sputtering gas is introduced into a vacuum atmosphere, a copper or copper-based target is sputtered, and a copper thin film or a copper-based thin film is formed on the surface of the film formation target placed in the vacuum atmosphere. A copper thin film manufacturing method,
When the target is sputtered, an additive gas composed of at least one of a gas having a nitrogen atom in the structure, a gas having an oxygen atom, or a gas having a nitrogen atom and an oxygen atom is used. 2. A method for producing a copper thin film, which is introduced into the vacuum atmosphere at a partial pressure of 2.66 × 10 ⁻⁵ Pa to 6.65 × 10 ⁻⁵ Pa.   2. The method for producing a copper thin film according to claim 1, wherein the additive gas contains at least one of oxygen gas, nitrogen gas, and water.   The method for producing a copper thin film according to claim 1, wherein the additive gas is introduced intermittently. A vacuum chamber;
Having copper or a copper-based target disposed in the vacuum chamber;
A sputtering apparatus for forming a thin film on the surface of a film formation target disposed in the vacuum atmosphere by making the inside of the vacuum chamber a vacuum atmosphere, introducing a sputtering gas, sputtering the target,
The vacuum tank is provided with a gas addition pipe, and in the atmosphere of the sputtering gas, a gas having a nitrogen atom, a gas having an oxygen atom, or a gas having a nitrogen atom and an oxygen atom in the structure. among them, that one of the added gas comprising one or more gases, which is configured to introduce continuous or pulsed with the following partial pressures 2.66 × 10 ^-5 Pa or 6.65 × 10 ^-5 Pa A sputtering apparatus characterized by

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