Patent ID: 12191124

DETAILED DESCRIPTION

Various exemplary embodiments are described below.

In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus comprises a chamber, a gas supply, an exhaust device, a substrate support, an upper electrode, a high-frequency power supply, an impedance circuit, and a controller. The gas supply is configured to supply a gas into the chamber. The substrate support includes a lower electrode and is provided in the chamber. The upper electrode is provided above the substrate support. The high-frequency power supply is configured to supply high-frequency power to the upper electrode. The impedance circuit is connected between the lower electrode and ground. The controller controls the gas supply and the exhaust device such that a pressure of the gas in the chamber is 26.66 Pa (200 mTorr) or higher. A frequency of the high-frequency power is lower than 13.56 MHz. An impedance of the impedance circuit is set such that an impedance of a first electrical path from the lower electrode through the impedance circuit to the ground is higher than an impedance of a second electrical path from a wall of the chamber to the ground.

Since the plasma processing apparatus of the above embodiment uses the high-frequency power having a frequency lower than 13.56 MHz, it is possible to generate a high-density plasma in a high-pressure chamber of 26.66 Pa (200 mTorr) or higher. Further, electrical coupling between the upper electrode and the lower electrode is weakened by the impedance circuit. Therefore, current flowing through the lower electrode is reduced. Accordingly, energy applied to the substrate on the substrate support is reduced.

In one exemplary embodiment, the plasma processing apparatus may further comprise a ring electrode. The ring electrode has a ring shape and is provided outside a space between the lower electrode and the upper electrode and inside the chamber. The plasma processing apparatus may further comprise a second impedance circuit that is different from a first impedance circuit that is the impedance circuit connected between the lower electrode and the ground. The second impedance circuit is connected between the ring electrode and the ground. An impedance of the second impedance circuit may be set such that an impedance of a third electrical path from the ring electrode through the second impedance circuit to the ground is lower than the impedance of the first electrical path.

In one exemplary embodiment, the plasma processing apparatus may further comprise a current sensor. The current sensor measures a current value in the third electrical path. The controller may set the impedance of the second impedance circuit to maximize the current value measured by the current sensor.

In one exemplary embodiment, the ring electrode may extend along a sidewall of the chamber. In one exemplary embodiment, the ring electrode may extend to surround the upper electrode. In one exemplary embodiment, the ring electrode may extend to surround the substrate support.

In one exemplary embodiment, the frequency of the high-frequency power may be 2 MHz or less.

In one exemplary embodiment, the gas supply may be configured to supply a film forming gas. In other words, the plasma processing apparatus may be a film forming apparatus.

In another exemplary embodiment, a plasma processing method is provided. The plasma processing method comprises (a) preparing a substrate on a substrate support in a chamber of a plasma processing apparatus. The substrate support includes a lower electrode. In the plasma processing apparatus, an impedance circuit is connected between the lower electrode and ground. The plasma processing method further comprise (b) supplying a gas into the chamber. A pressure of the gas in the chamber is set to a pressure of 26.66 Pa (200 mTorr) or higher. The plasma processing method further comprise (c) supplying high-frequency power to an upper electrode. The upper electrode is provided above the substrate support. In a state where the pressure of the gas in the chamber is set to a pressure of 26.66 Pa (200 mTorr) or higher in the (b), the high-frequency power having a frequency lower than 13.56 MHz is supplied to the upper electrode in the (c). During a period in which the (c) is performed, an impedance of the impedance circuit is set such that an impedance of a first electrical path is higher than an impedance of a second electrical path. The first electrical path is an electrical path from the lower electrode through the impedance circuit to the ground. The second electrical path is an electrical path from a wall of the chamber to the ground.

In one exemplary embodiment, during a period in which the (c) is performed, an impedance of a second impedance circuit may be set such that an impedance of a third electrical path is lower than the impedance of the first electrical path. The third electrical path is an electrical path from a ring electrode through the second impedance circuit to the ground.

In one exemplary embodiment, during a period in which the (c) is performed, the impedance of the second impedance circuit may be set to maximize a current value in the third electrical path measured by a current sensor.

In one exemplary embodiment, the gas supplied into the chamber in the (b) may be a film forming gas. In other words, the plasma processing method may be a film forming method.

Various exemplary embodiments are described in detail below with reference to the accompanying drawings. The same reference numeral is attached to a part which is the same or equivalent in each drawing.

FIG.1is a diagram schematically showing a plasma processing apparatus according to one exemplary embodiment. The plasma processing apparatus shown inFIG.1includes a chamber10. The chamber10provides an inner space therein. The chamber10may include a chamber body12. The chamber body12has a substantially cylindrical shape. Walls, including sidewalls, of the chamber10are provided by the chamber body12. The inner space of the chamber10is provided within the chamber body12. The chamber body12is formed from metals such as aluminum. The chamber body12may be electrically grounded.

The chamber10provides a passage10pin its sidewall. A substrate W processed in the plasma processing apparatus1passes through the passage10pwhen transferred between the inside and outside of the chamber10. A gate valve10gis provided along the sidewall of the chamber10for opening and closing the passage10p.

The plasma processing apparatus1further includes a substrate support14. The substrate support14is provided within the chamber10. The substrate support14is configured to support the substrate W placed thereon. The substrate support14has a main body. The main body of the substrate support14is made of, for example, aluminum nitride, and may have a disc shape. A guide ring15may be provided on an outer edge of the main body of the substrate support14. The substrate support14may be supported by a support member16. The support member16extends upwardly from a bottom of the chamber10. The support member16may have a cylindrical shape.

The substrate support14includes a lower electrode18. The lower electrode18is embedded in the main body of the substrate support14. The substrate support14may have a heater20. The heater20is embedded in the main body of the substrate support14. The heater20is a resistive heating element, and is made of, for example, a refractory metal such as molybdenum. The heater20is connected to a heater power supply22. The heater power supply22is provided outside the chamber10. The heater20heats the substrate W by receiving power from the heater power supply22and generating heat.

The plasma processing apparatus1further includes an upper electrode30. The upper electrode30is provided above the substrate support14. The upper electrode30constitutes a ceiling of the chamber10. The upper electrode30is electrically separated from the chamber body12. In one embodiment, the upper electrode30is fixed to an upper portion of the chamber body12via an insulating member32.

In one embodiment, the upper electrode30is configured as a showerhead. The upper electrode30may include a base member33and a ceiling plate34. The upper electrode30may further include an intermediate member35. The base member33, the ceiling plate34, and the intermediate member35are conductive and made of, for example, aluminum. The base member33is provided above the ceiling plate34. A heat insulating member37may be provided on the base member33. The intermediate member35has a substantially ring shape, and is interposed between the base member33and the ceiling plate34. The base member33and the ceiling plate34provide a gas diffusion space30dtherebetween. The base member33provides a gas introduction port33athat connects to the gas diffusion space30d. The ceiling plate34provides a plurality of gas holes34a. The plurality of gas holes34aextend downward from the gas diffusion space30dand penetrate the ceiling plate34along its thickness direction.

The plasma processing apparatus1further includes a gas supply36. The gas supply36is configured to supply a gas into the chamber10. In one embodiment, the gas supply36is connected to the gas introduction port33avia a pipe38. The gas supply36may have one or more gas sources, one or more flow controllers, and one or more on-off valves. Each of the one or more gas sources is connected to the gas introduction port33avia a corresponding flow controller and a corresponding on-off valve.

In one embodiment, the gas supply36may supply a film forming gas. In other words, the plasma processing apparatus1may be a film forming apparatus. The film formed on the substrate W using the film forming gas may be an insulating film or a dielectric film. In another embodiment, the gas supply36may supply an etching gas. In other words, the plasma processing apparatus1may be a plasma etching apparatus.

The plasma processing apparatus1further includes an exhaust device40. The exhaust device40includes a pressure controller, such as an automatic pressure control valve, and a vacuum pump, such as a turbomolecular pump or a dry pump. The exhaust device40is connected to an exhaust pipe42. The exhaust pipe42is connected to the bottom of the chamber10and communicates with the inner space of the chamber10. The exhaust pipe42may be connected to the sidewall of the chamber10.

The plasma processing apparatus1further includes a high-frequency power supply44. The high-frequency power supply44generates high-frequency power. The frequency of the high-frequency power is less than 13.56 MHz. The frequency of the high-frequency power may be 2 MHz or less. The frequency of the high-frequency power may be 200 kHz or higher.

The high-frequency power supply44is connected to the upper electrode30via a matching device46. The matching device46has a matching circuit that matches an impedance of a load of the high-frequency power supply44with an output impedance of the high-frequency power supply44.

The plasma processing apparatus1further includes an impedance circuit50. The impedance circuit50is connected between the lower electrode18and the ground. The impedance circuit50may provide a variable impedance between the lower electrode18and the ground. The impedance circuit50may include a series circuit of an inductor and a capacitor. The inductor may be a variable inductor and the capacitor may be a variable capacitor.

The impedance of the impedance circuit50is set such that an impedance of an electrical path51from the lower electrode18to the ground through the impedance circuit50is higher than an impedance of an electrical path52from the wall of the chamber10to the ground. The impedance of the impedance circuit50can be set by a controller80, which will be described later.

In one embodiment, the plasma processing apparatus1may further include an impedance circuit54. The impedance circuit54is connected between the wall of the chamber10and the ground. In other words, in one embodiment, the electrical path52includes the impedance circuit54. The impedance circuit54may provide a variable impedance between the wall of the chamber10and the ground. The impedance circuit54may include a series circuit of an inductor and a capacitor. The inductor may be a variable inductor and the capacitor may be a variable capacitor.

An impedance of the impedance circuit54is set such that the impedance of the electrical path52is lower than the impedance of the electrical path51. The impedance of the impedance circuit54may be set by the controller80.

In one embodiment, the plasma processing apparatus1may further include a current sensor56. The current sensor56is configured to measure a current value in the electrical path52. If the wall of the chamber10is directly grounded, the plasma processing apparatus1may not include the impedance circuit54and the current sensor56.

The plasma processing apparatus1further includes the controller80. The controller80is configured to control each component of the plasma processing apparatus1. The controller80may be a computer including a processor, a storage such as a memory, an input device, a display device, a signal input/output interface, or the like. The storage of the controller80stores a control program and recipe data. The processor of the controller80executes the control program and controls each component of the plasma processing apparatus1according to the recipe data. By controlling each component of the plasma processing apparatus1by the controller80, plasma processing methods according to various exemplary embodiments are executed in the plasma processing apparatus1.

The controller80controls the gas supply36and the exhaust device40so that gas pressure in the chamber10is 26.66 Pa (200 mTorr) or higher. The controller80controls the high-frequency power supply44to supply high-frequency power to the upper electrode30. Since the plasma processing apparatus1uses high-frequency power having a frequency lower than 13.56 MHz, it is possible to generate a high-density plasma in the high-pressure chamber10of 26.66 Pa (200 mTorr) or higher.

Further, the impedance of the impedance circuit50is set such that the impedance of the electrical path51is higher than the impedance of the electrical path52. Therefore, in the plasma processing apparatus1, electrical coupling between the upper electrode30and the lower electrode18is weakened by the impedance circuit50. Accordingly, the current flowing through the lower electrode18is reduced, and the energy applied to the substrate W on the substrate support14is reduced.

In one embodiment, the controller80can control the impedance of the impedance circuit54to maximize the current value of the current sensor56. In accordance with this embodiment, even if a film such as an insulating film or a dielectric film is formed on a wall surface of the chamber10, the current flowing through the lower electrode18is suppressed. Therefore, the energy applied to the substrate W on the substrate support14is reduced.

A plasma processing apparatus according to another exemplary embodiment will be described below with reference toFIG.2.FIG.2is a diagram schematically showing a plasma processing apparatus according to another exemplary embodiment. Differences between a plasma processing apparatus1B shown inFIG.2and the plasma processing apparatus1will be described below.

The plasma processing apparatus1B further includes a ring electrode70. The ring electrode70has a ring shape. The ring electrode70is provided outside the space between the lower electrode18and the upper electrode30and in the chamber10. In the plasma processing apparatus1B, the ring electrode70extends along the sidewall of the chamber10(or the chamber body12). When the exhaust pipe42is connected to the sidewall of the chamber10, the ring electrode70may be a mesh electrode providing a plurality of holes.

In the plasma processing apparatus1B, the impedance circuit54is connected between the ring electrode70and the ground. The impedance circuit54may provide a variable impedance between the ring electrode70and the ground. The impedance of the impedance circuit54is set such that an impedance of an electrical path53from the ring electrode70to the ground through the impedance circuit54is lower than the impedance of the electrical path51. In the plasma processing apparatus1B, the electrical path52directly connects the wall of the chamber10to the ground.

In the plasma processing apparatus1B, the current sensor56is configured to measure a current value in the electrical path53. Also in the plasma processing apparatus1B, the controller80can control the impedance of the impedance circuit54to maximize the current value of the current sensor56. In this embodiment, even if a film such as an insulating film or a dielectric film is formed on a surface of the ring electrode70, the current flowing through the lower electrode18is suppressed. Therefore, the energy applied to the substrate W on the substrate support14is reduced.

A plasma processing apparatus according to another exemplary embodiment will be described below with reference toFIG.3.FIG.3is a diagram schematically showing a plasma processing apparatus according to still another exemplary embodiment. A plasma processing apparatus1C shown inFIG.3differs from the plasma processing apparatus1B in that the ring electrode70extends to surround the upper electrode30. In the plasma processing apparatus1C, the ring electrode70may surround the ceiling plate34. Other configurations of the plasma processing apparatus10may be similar to other configurations of the plasma processing apparatus1B.

A plasma processing apparatus according to another exemplary embodiment will be described below with reference toFIG.4.FIG.4is a diagram schematically showing a plasma processing apparatus according to further still another exemplary embodiment. A plasma processing apparatus1D shown inFIG.4differs from the plasma processing apparatus1B in that the ring electrode70extends to surround the substrate support14. Other configurations of the plasma processing apparatus1D may be similar to other configurations of the plasma processing apparatus1B.

A plasma processing method performed using the plasma processing apparatus of any one of the various exemplary embodiments described above will be described below.

The plasma processing method includes step (a). In step (a), the substrate W is provided on the substrate support14in the chamber10.

In subsequent step (b), the pressure of the gas in the chamber is set to a pressure of 26.66 Pa (200 mTorr) or higher. In step (b), the gas is supplied from the gas supply36into the chamber10. The gas may be a film forming gas, as described above, or an etching gas. The pressure of the gas in the chamber10is regulated by the gas supply36and the exhaust device40.

Step (c) is performed during step (b). In other words, step (c) is performed in a state where the pressure of the gas in the chamber10is set to 26.66 Pa (200 mTorr) or higher. In step (c), the high-frequency power is supplied from the high-frequency power supply44to the upper electrode30. The high-frequency power has a frequency lower than 13.56 MHz. The frequency of the high-frequency power may be 2 MHz or less. Further, the frequency of the high-frequency power may be 200 kHz or higher. A high-density plasma is generated in the high-pressure chamber10by step (c).

The impedance of the electrical path51including the impedance circuit50is higher than the impedance of the electrical path52. Therefore, the current flowing through the lower electrode18is reduced, and the energy applied to the substrate W on the substrate support14is reduced.

In the case of using the plasma processing apparatus1, the impedance of the impedance circuit54may be controlled to maximize the current value of the current sensor56during step (c). In this case, even if a film such as an insulating film or a dielectric film is formed on the wall surface of the chamber10, the current flowing through the lower electrode18is suppressed. Therefore, the energy applied to the substrate W on the substrate support14is reduced.

In the case of using the plasma processing apparatus1B,10, or1D, the impedance of the electrical path51including the impedance circuit50is higher than the impedance of the electrical path53. Therefore, the current flowing through the lower electrode18is reduced, and the energy applied to the substrate W on the substrate support14is reduced.

Also in the case of using the plasma processing apparatus1B,10, or1D, during step (c), the impedance of the impedance circuit54may be controlled to maximize the current value of the current sensor56. In this case, even if a film such as an insulating film or a dielectric film is formed on the surface of the ring electrode70, the current flowing through the lower electrode18is suppressed. Therefore, the energy applied to the substrate W on the substrate support14is reduced.

While various exemplary embodiments have been described above, various additions, omissions, substitutions, and modifications may be made without being limited to the exemplary embodiments described above. Further, elements from different embodiments can be combined to form other embodiments.

Experiments performed using the plasma processing apparatus1will be described below. The experiments described below do not limit the present disclosure.

First Experiment

In a first experiment, a plasma was generated in the chamber10of the plasma processing apparatus1using different combinations of the frequencies of the high-frequency power and the pressures of the gas in the chamber10. The frequencies of the high-frequency power used in the first experiment were 450 kHz, 2 MHz, 13.56 MHz, and 40.68 MHz. In the first experiment, a plasma absorption probe was used to measure the electron density in the plasma within the chamber10. Other conditions in the first experiment are shown below.

Conditions of the First Experiment

Gas supplied into the chamber10: mixed gas of argon gas and oxygen gas

High-frequency power: 500 W

FIG.5shows the results of the first experiment. In the graph ofFIG.5, the horizontal axis indicates the pressure of the gas in the chamber10in the first experiment, and the vertical axis indicates the electron density. As shown inFIG.5, when the pressure of the gas in the chamber was set to a high pressure of 200 mTorr (26.66 Pa) or higher, high electron density was obtained using high-frequency power having a frequency lower than 13.56 MHz. In other words, it was confirmed that a high-density plasma can be generated by using high-frequency power having a frequency lower than 13.56 MHz when the pressure of the gas in the chamber10is set to a high pressure of 200 mTorr (26.66 Pa) or higher.

Second Experiment

In a second experiment, a plasma was generated in the chamber10of the plasma processing apparatus1under two conditions of high impedance and low impedance of the impedance circuit50. In the second experiment, the ion energy distribution (IED) of the plasma on the substrate was determined. Other conditions in the second experiment are shown below.

Conditions of the Second Experiment

Gas supplied into the chamber10: mixed gas of argon gas and oxygen gas

Pressure of gas in the chamber10: 500 mTorr (66.66 Pa)

High-frequency power: 450 kHz and 800 W

FIG.6shows two ion energy distributions obtained in the second experiment. InFIG.6, the dotted line indicates the ion energy distribution in the case where the impedance of the impedance circuit50is low. InFIG.6, the solid line indicates the ion energy distribution in the case where the impedance of the impedance circuit50is high. It was confirmed that when the impedance of the impedance circuit50is low, the ions supplied to the substrate have high energy, as indicated by the dotted line inFIG.6. On the other hand, it was confirmed that when the impedance of the impedance circuit50is high, the ions supplied to the substrate have low energy, as indicated by the solid line inFIG.6.

Third Experiment

In a third experiment, similarly to the second experiment, a plasma was generated in the chamber10of the plasma processing apparatus1under two conditions, when the impedance of the impedance circuit50was high and when it was low. In the third experiment, the electron density in the plasma was measured using a plasma absorption probe to obtain the electron density distribution in the plasma. Other conditions in the third experiment are shown below.

Conditions of the Third Experiment

Gas supplied into the chamber10: mixed gas of argon gas and oxygen gas

Pressure of gas in the chamber10: 500 mTorr (66.66 Pa)

High-frequency power: 450 kHz and 800 W

FIG.7shows two electron density distributions obtained in the third experiment. InFIG.7, the horizontal axis indicates the position in the radial direction with the position on the center of the substrate W (the position of 0 mm) as a reference. InFIG.7, the dotted line indicates the electron density distribution in the case where the impedance of the impedance circuit50is low. InFIG.7, the solid line indicates the electron density distribution in the case where the impedance of the impedance circuit50is high. As shown inFIG.7, in the case of using high-frequency power having a relatively low frequency such as a frequency lower than 13.56 MHz, the radial distribution of the electron density in the plasma was substantially uniform without depending on the impedance of the impedance circuit50.

From the above description, it will be appreciated that various embodiments of the present disclosure have been described herein for purpose of illustration, and that various changes may be made without departing from the scope and spirit of the present disclosure. Therefore, the various embodiments disclosed herein are not intended to be limiting, with a true scope and spirit being indicated by the following claims.

DESCRIPTION OF REFERENCE NUMERALS

1: plasma processing apparatus,10: chamber,14: substrate support,18: lower electrode,30: upper electrode,36: gas supply,40: exhaust device,44: high-frequency power supply,50: impedance circuit