JP3392490B2 - Sputtering method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering method and apparatus for forming a thin film.

[0002]

2. Description of the Related Art In a sputtering method, it is usually necessary to apply a voltage and a current to a target in Ar gas to form a thin film, and to cause plasma discharge. If the film forming rate is slow, the substrate temperature rises, and it becomes difficult to obtain a constant film quality.

In order to solve such a problem, a magnetic field is formed in the vicinity of the target to confine plasma excited by a voltage and a current applied to the target in the vicinity of the target, whereby Ar ions excited by electrons in the plasma, etc. There is a magnetron sputtering method as a method of suppressing the inflow of oxygen to the substrate surface together with plasma. When this method is used, the film can be formed at a high speed, so that the temperature change of the substrate can be suppressed relatively. Therefore, it is widely used for forming a compound thin film such as an oxide.

However, even in such a magnetron sputtering method, when a thin film is continuously formed for a long time, the target is eroded, and the erosion causes a change in the magnetron discharge state to which the substrate is exposed during film formation.
The problem that the temperature of the substrate changes accordingly has not been solved yet. Therefore, in the conventional magnetron sputtering method, there is a problem that the quality of a film such as an oxide, which is easily affected by the magnetron discharge state, changes with time.

As a method for suppressing the change in film quality over time,
A method has been proposed in which the parallel magnetic field strength on the target surface is adjusted to keep the discharge voltage constant (Japanese Patent Laid-Open No. 2-232).
358). In this method, when an ITO film is formed by magnetron sputtering, an insulating oxide is formed on the target surface, and the voltage applied to the target is increased accordingly. Is intended to be uniform. However, even in this method, since the magnetron discharge state to which the substrate is exposed during film formation is not kept constant, the rise in substrate temperature cannot be suppressed.
For this reason, when forming a compound thin film such as an oxide, which is particularly susceptible to the magnetron discharge state, a change with time still occurs, and it was not possible to form a compound thin film having a constant film quality.

[0006]

As described above, when a continuous thin film is formed by the conventional technique, there is a problem that the quality of the obtained film changes with time. The present invention has been made in view of such a problem, and an object thereof is to provide a sputtering method and an apparatus therefor capable of forming a compound thin film having a constant film quality for a long time.

[0007]

According to the first invention of the present application, a target is placed in a film forming container and plasma discharge is generated in the film forming container to form a thin film on a substrate. In the sputtering method, a step of supplying an inert gas into the film forming container, a step of supplying a voltage and current to an electrode arranged in the film forming container to plasma discharge the inert gas, Measuring an ion current density and a floating potential detected from a probe arranged in the plasma discharge region, and controlling a product of the ion current density and the floating potential detected from the probe to a substantially constant value. And a sputtering method.

A second invention of the present application is a sputtering apparatus for forming a thin film on a substrate by arranging a target in a film forming container to generate plasma discharge in the film forming container. A film forming container having a supply means, a discharge power supply electrically connected to an electrode arranged in the film forming container, and a plasma of the inert gas generated in the film forming container by the discharge power supply. A probe disposed in the discharge region; means for measuring the ion current density and floating potential detected by the probe; and means for controlling the product of the ion current density and floating potential to a substantially constant value. This is a sputtering apparatus characterized by the above.

That is, according to the present invention, a desired sputtering film is obtained by disposing a probe in a film forming container and making the product of the ion current density and the floating potential detected by this probe a constant value.

Hereinafter, the present invention will be described in detail with reference to the drawings. 1 and 2 are schematic configuration diagrams showing an example of the sputtering apparatus of the present invention. The means for supplying the inert gas according to the present invention is not particularly limited, and any commonly used means can be used. For example, as shown in the drawing, the inert gas supply system 2 is connected to the film forming container 1 via the conductance valve 4 or the like, whereby the inert gas is supplied into the film forming container 1. Ar gas is usually used as the inert gas used at this time.

Separately from the gas supply system 2, an exhaust system 3 is connected to the film forming container 1 via a conductance valve 4 or the like so that the gas in the film forming container 1 is exhausted and the inside of the film forming container is desired. Can be at atmospheric pressure. For example, while the pressure inside the film forming container 1 is reduced to 10 ⁻⁶ Torr or less by the exhaust system 3, the inside of the film forming container 1 is set to 1 × 10 ^{−3 to} 5 by the inert gas supply system 2.
It may be maintained at about × 10 ^-3 Torr. Further, when a reactive gas is further supplied into the film forming container 1 to obtain an oxide film such as ITO, a reactive gas supply system 13 as shown in FIG. It is also possible to obtain a desired film by supplying oxygen as.

The target 5 in the present invention is not particularly limited as long as it is used for ordinary sputtering, and may be appropriately selected according to the film to be formed. When a conductor is used as the target, the target 5 itself is usually used as an electrode as shown in FIGS. When the target is an insulator, etc., a separate electrode may be provided if necessary, and the target may be placed between the discharge region and the electrode, and sputtering may be performed as usual.

Further, as shown in the figure, by providing a means for generating a magnetic field on the surface of the target 5, it can be used as a magnetron sputtering apparatus. As the means for generating the magnetic field, any means such as the magnet 6 may be used, and normally 400 Gauss or more is used, but 1 kGauss or more is used to reduce the voltage supplied from the discharge power supply 7. It is desirable to use. It is also possible to control the magnetic field by using an electromagnet as the magnet 6 or by using a permanent magnet 6a and an electromagnet 6b together as shown in FIG.

Further, in the present invention, the inert gas concentration and atmospheric pressure in the film forming container 1 by the inert gas supply system 2 and the exhaust system 3, the magnitude of the magnetic field generated from the magnet 6 and the discharge power supply 7 are used. By adjusting the voltage and current supplied to the electrode 5, a desired plasma discharge state can be generated in the film forming container 1.

At this time, if the substrate 11 is arranged in the region in the plasma discharge state in the film forming container 1, a sputtering film is formed on the surface of the substrate 11 facing the target 5.

In the present invention, the probe 8 placed in the film forming container 1 can be used without particular limitation as long as it is a conductive substance. In addition, a wire-like conductive member made of tungsten or gold having a diameter of about 0.2 to 2 mm and covered with glass or the like is usually used in terms of durability.

The location of the probe 8 is not particularly limited as long as it is in a plasma discharge state.
When the target is placed between the target 5 and the substrate 11, the sputtering film may not be formed on the substrate 11 at the position shielded by the probe 8. Therefore, it is desirable that the probe 8 be installed at a position that does not block the inflow path of the sputtered particles to the substrate 11.

The means for measuring the ion current density and floating potential detected by the probe 8 in the present invention (hereinafter referred to as measuring means) is, for example, the probe 8
The circuit 9 for measuring the ion current density and the floating potential electrically connected to the above may be used.

This measuring means is detected by the probe 8 arranged in the film forming container 1 when the inside of the film forming container 1 is plasma-discharged by the voltage and current supplied from the discharge power source 7 to the target 5. The plasma discharge state in the film forming container 1 is observed by measuring the ion current density and the floating potential.

In the present invention, at this time, as shown in FIG. 1, for example, by controlling the voltage or current of the discharging power source 7 by the controller 10 connected to the discharging power source 7, the ions measured by the measuring means are measured. The product of current density and floating potential can be constant. That is, it is possible to suppress a change in the plasma discharge state in the film forming container 1 due to the erosion of the target 5, and it is possible to form a sputtering film having a constant film quality. Therefore, in such a case, it is necessary to use, as the discharging power supply 7, one capable of adjusting the voltage or current supplied to the target 5.

When the permanent magnet 6a and the electromagnet 6b are used together as the magnet 6 as shown in FIG. 2, the magnetic field generated on the surface of the target 5 is controlled by using the electromagnet power source 12 and the controller 10 capable of adjusting the voltage or current. It is also possible to make the product of the ion current density and the floating potential measured by the measuring means constant, for example by controlling.

Further, when a reactive gas supply system 13 is provided as shown in FIG. 2 and oxygen is supplied as a reactive gas into the film forming container 1, an insulating oxide is formed on the surface of the target 5. As a result, the voltage supplied from the discharge power source 7 becomes high, which may result in failure to obtain uniform film quality. Therefore, while the voltage supplied to the target 5 is kept constant, the controller 10 controls the current supplied from the discharge power supply 7 to the target 5 and the electromagnet 6b.
If the product of the current density and the floating potential is made constant by adjusting the magnitude of the magnetic field generated from, it becomes possible to control the product of the ion current density and the floating potential for a longer period of time. It is possible to obtain a uniform film quality for a long time.

Further, the product of the current density and the floating potential can be made constant by changing the atmospheric pressure in the film forming container 1 by the inert gas supply system 2, the exhaust system 3 or the reactive gas supply system 13. is there. At this time, the atmospheric pressure in the film forming container 1 is preferably controlled within the range of 1 × 10 ^{−3 to} 5 × 10 ⁻³ Torr as described above.

In the present invention, the controller 10 as a means for controlling the product of the ion current density and the floating potential to have a substantially constant value in this way is, as shown in FIG. 1, a discharge power source 7 and a circuit 9. Alternatively, as shown in FIG. 2, the discharge power source 7, the electromagnet power source 12 and the circuit 9 are electrically connected, and the discharge power source 7 corresponds to the change in the product of the measured values of the ion current density and the floating potential. It is desirable that the voltage and the current of the above or the voltage and the current of the power supply 7 for discharge or the power supply 12 for the electromagnet are interlockedly controlled.

Further, in the above-mentioned apparatus, in order to obtain a constant film quality continuously for a long time, the measuring means is interlocked with the control system. The measuring means monitors the inflow of plasma which affects the film quality. When the set value of the plasma inflow amount exceeds a certain range, the continuous film formation is stopped, the target 5 is replaced, the apparatus is repaired, and the film formation is restarted.

Here, the constant value depends on the accuracy of the uniformity of the film quality, but is ± 10% with respect to the product of the ion current density and the measured value of the floating potential required to obtain the desired film quality. It is desirable to be within the range.

In the present invention, in such an apparatus, a shutter 14 is provided between the substrate 11 and the target 5 in order to prevent the film formation from starting while the plasma discharge state in the film formation container 1 is unstable. It can also be installed at. The shutter 14 is initially closed, and is opened after the apparatus is started and the plasma discharge state in the film forming container 1 is stabilized.

In the present invention, since the product of the ion current density and the floating potential detected from the probe is made constant in this way, the plasma discharge state in the film forming container can be made constant. The substrate temperature can be kept constant. Therefore, the quality of the film formed on the substrate surface can be made uniform.

[0029]

【Example】

Example 1 In this example, in the above-described device of FIG.
An ITO film in the range of 10 ^-4 Ω · cm or more and 6 ^{-10 4} Ω · cm or less was formed in the range of less than 80 mmφ centering on the center of the substrate. At this time, the controller was set to increase the current of the DC power source as the discharge power source when the product of the ion current density and the floating potential started to decrease, and the electromagnet and the electromagnet power source were not operated.

As a target, 150 × 280 mm, thickness 6 m
In ₂ O ₃ -10 wt% SnO ₂ of m was used as the substrate.
A glass substrate having a size of 230 × 250 mm and a thickness of 1 mm was used, and they were arranged so as to face each other with a distance of 60 mm. Further, a probe connected to a circuit for measuring the ion current density and the floating potential was arranged at a position of 4 mm on the substrate and 80 mm from the center to the end of the substrate.

Under these conditions, first, the film formation container 1 was evacuated to 1 × 10 ^-6 Torr, and then Ar gas was supplied to 17 times.
2 sccm, oxygen as a reactive gas was introduced into the film forming container at 2 sccm, and the pressure in the film forming container was further adjusted to 5 × 10 ⁻³ T.
After adjusting the conductance valve connected to the exhaust system so as to be orr, when the DC power supply was turned on so that the power density became 0.4 W / cm ² , the initial value of the discharge voltage was 280 V, and the ion current density was And the product of the floating potential was 136 mW / cm ² .

At this time, the resistivity of the ITO film formed first on the glass substrate was 5 × 10 ⁻⁴ Ω · cm. Furthermore, this sputtering device was operated continuously. When the product of ion current density and floating potential started to decrease with time, the controller actuated to increase the current of the DC power supply, and the product of ion current density and floating potential could be kept constant.

As a result, the resistivity of the formed ITO film gradually increases with the passage of time, and the resistivity is 5 × 10 ⁻⁴ Ω.
・ IT in the range of cm to 6 × 10 ^-4 Ω · cm
An O film could be formed for 60 hours.

Example 2 In this example, the apparatus shown in FIG. 2 including an electromagnet and an electromagnet power supply was used, and a controller was used to change the currents of the DC power supply and the electromagnet power supply as the product of ion current density and floating potential changed. When a DC power source was turned on in exactly the same manner as in Example 1 except that the setting was made to increase, the initial value of the discharge voltage of the DC power source was 280 V, and the product of the ion current density and the floating potential was 136 mW / cm ^2. Was displayed.

At this time, the resistivity of the ITO film formed first on the glass substrate was 5 × 10 ⁻⁴ Ω · cm. Furthermore, this sputtering device was operated continuously. When the product of the ion current density and the floating potential starts to decrease with the passage of time, the controller operates to increase the currents of the DC power supply 14 and the power supply for the electromagnet, and keeps the product of the ion current density and the floating potential constant. I was able to.

As a result, the resistivity of the formed ITO film gradually increases with the passage of time, and the resistivity is 5 × 10 ⁻⁴ Ω.
・ IT in the range of cm to 6 × 10 ^-4 Ω · cm
An O film could be formed for 80 hours.

On the other hand, for comparison, an ITO film was formed in exactly the same manner as in Example 1 except that the controller was not operated using the same device, and the resistivity of the ITO film first formed on the glass substrate was measured. Is 5 × as in the embodiment
Although it was 10 ⁻⁴ Ω · cm, when this device was continuously operated, the resistivity increased sharply as compared with the example, and the resistivity was 5
It was only 30 hours that an ITO film having a thickness in the range of ^10-4 Ω · cm or more and 6 × 10 ⁻⁴ Ω · cm or less was obtained. From the above results, it is found that it is effective to keep the product of the ion current density and the floating potential constant in order to continuously obtain a uniform film quality for a long time.

[0038]

As described above in detail, according to the present invention, it becomes possible to continuously form a thin film having a uniform film quality for a long time.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a sputtering apparatus of the present invention.

FIG. 2 is a schematic configuration diagram showing an example of another sputtering apparatus of the present invention.

[Explanation of symbols]

1 Film Forming Container 2 Inert Gas Supply System 3 Exhaust System 4 Conductance Valve 5 Target (Electrode) 6 Magnet 6a Permanent Magnet 6b Electromagnet 7 Discharge Power Supply 8 Probe 9 Circuit 10 Controller 11 Board 12 Power Supply for Electromagnet

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuro Yasuda 1 Komukai Toshiba Town, Komukai-shi, Kawasaki City, Kanagawa Prefecture Toshiba Research & Development Center (56) Reference JP 4-72064 (JP, A) JP-A-5-266990 (JP, A) JP-A-54-139892 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 14/00-14/58

Claims (2)

(57) [Claims] 1. A sputtering method in which a target is placed in a film forming container, plasma discharge is generated in the film forming container to form a thin film on a substrate, and an inert gas is contained in the film forming container. And a step of causing a plasma discharge of the inert gas by supplying a voltage and a current to the electrodes arranged in the film forming container, and a probe arranged in the plasma discharge region. A sputtering method comprising: a step of measuring an ion current density and a floating potential; and a step of controlling a product of the ion current density and the floating potential detected from the probe to a substantially constant value. 2. A sputtering apparatus for placing a target in a film forming container to generate plasma discharge in the film forming container to form a thin film on a substrate, having a means for supplying an inert gas. A film forming container, and a discharge power source electrically connected to electrodes arranged in the film forming container,
A probe arranged in a plasma discharge region of the inert gas generated in the film forming container by the discharge power source, means for measuring an ion current density and a floating potential detected by the probe, and the ion current density. And a means for controlling the product of floating potentials to a substantially constant value.