JP3182615B2 - Plasma processing 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 plasma processing method and apparatus for performing plasma processing such as etching, CVD, and sputtering on a substrate such as a semiconductor integrated circuit substrate using gas plasma generated by high-frequency glow discharge. .

[0002]

2. Description of the Related Art Conventionally, a plasma processing apparatus for plasma processing a substrate (substrate to be processed) using high-frequency glow discharge has been actively used in the manufacture of semiconductor integrated circuits. Above all, a reactive ion etching (RIE) apparatus for etching by placing a substrate on a high-frequency application electrode is capable of performing anisotropic etching and excellent in mass productivity, and is therefore frequently used in each process of semiconductor device manufacturing. It has become.

[0003] However, at first, this type of apparatus had a configuration in which a substrate was simply placed on a high-frequency application electrode (including a substrate mounting table to which a high-frequency voltage was applied). It is easily heated, the substrate temperature rises, the photoresist of the etching mask is thermally damaged, the etching shape deteriorates, and it is difficult to improve the etching rate and control the etching shape as desired. There were drawbacks.

[0004] Therefore, in order to cool the substrate to a temperature at which the substrate is not thermally damaged during the etching, the substrate is mechanically clamped to an electrode (or a substrate mounting table placed thereon), and thermal contact between the two is performed. Or by flowing a gas such as He on the back surface of the substrate to increase the heat transfer effect between the substrate and the substrate mounting surface, thereby cooling the substrate, or through a dielectric below the substrate mounting portion. For example, a method has been devised in which a DC electrode is embedded and the substrate is brought into close contact with the substrate mounting surface by electrostatic force (electrostatic chuck) to improve heat transfer. In particular, various methods have been devised for the electrostatic chuck method because the structure is relatively simple and the cooling effect is large.

[0005] For example, an electrostatic chucking method utilizing the electrical conductivity of gas plasma, which is disclosed in Japanese Patent Publication No. 55-53853 (Japanese Patent Application Laid-Open No. 55-9228) "Dry Etching Apparatus", employs a high frequency applying electrode. The gas plasma works as an electrode sandwiching the dielectric film, so it is simple and has little damage to the substrate. The electrostatic chucking force works only while the gas plasma exists. Met.

Further, as disclosed in Japanese Patent Application Laid-Open No. 1-312087, "Dry Etching Apparatus", a DC voltage for an electrostatic chuck superimposed on a high-frequency application electrode is set to an absolute value smaller than a self-bias voltage induced on a substrate. By setting a large negative voltage, a large electron current did not flow through the high-frequency application electrode, so that dielectric breakdown of the dielectric film was almost eliminated, and the electrostatic chuck became mechanically highly reliable.

[0007]

However, in order to increase the chucking reliability of the electrostatic chuck and increase the chucking efficiency, the dielectric constant of the dielectric film must be increased or the alumina film used as the dielectric film must be oxidized. It has been necessary to accumulate charges near the surface of the dielectric film by mixing titanium. By using these dielectric films, a strong adsorption force was obtained and the substrate could be efficiently cooled.However, after the etching was completed, if the substrate was detached from the substrate mounting surface and transported, the charge remaining on the dielectric film was lost. As a result, a residual suction force acts on the substrate, and the substrate cannot be transported, and in severe cases, the substrate is often damaged. In order to reduce the residual attraction force, for example, a method of applying a reverse voltage at the time of desorption is employed.
However, in this method, a power supply for the electrostatic chuck needs to be a circuit capable of switching the output between positive and negative, which increases the cost of the power supply. Power ON / OF at the time of desorption
The sequence of F had to be complicated. If the value of the reverse voltage and the application time are not set to appropriate values, the substrate may be attracted to the sample stage again due to the residual attracting force due to the reverse voltage.

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving the above problems, and is an electrostatic chuck having a very strong attraction force.
It is an object of the present invention to provide a plasma processing method and apparatus capable of easily and easily detaching a substrate from a substrate mounting table even when residual charges remain on a dielectric film during FF.

[0009]

According to the plasma processing method of the present invention for achieving the above object, a high-frequency applying electrode is provided in a vacuum vessel provided with a gas introducing means such as a reactive gas, and the high-frequency applying electrode is provided on the high-frequency applying electrode. Providing a substrate mounting table made of a dielectric in which a metal electrode having the same potential as the high-frequency application electrode is embedded, and superimposing a negative DC voltage having an absolute value larger than a negative self-bias voltage generated by plasma on the high-frequency application electrode. In the method of electrostatically chucking a substrate on the substrate mounting table and performing plasma processing on the substrate with a gas plasma such as the reactive gas, a predetermined time passes after the DC voltage is cut off at the end of the plasma processing. Later, the high frequency voltage is cut off.

It is desirable that the high-frequency voltage be cut off after a lapse of 3 to 15 seconds after the DC voltage is cut off. When the time is less than 3 seconds, the disappearance of the residual attraction force is insufficient. On the other hand, when the time exceeds 15 seconds, inconveniences such as plasma treatment by application of a high-frequency voltage and progress of the substrate temperature are caused.

According to another aspect of the present invention, there is provided a plasma processing apparatus including a high-frequency applying electrode in a vacuum vessel provided with a gas introducing means such as a reactive gas, and a dielectric film formed on the high-frequency applying electrode. And a substrate mounting table in which a metal electrode covered with the dielectric film and having the same potential as that of the high-frequency application electrode is embedded, and during the plasma processing, the high-frequency application electrode has an absolute value higher than a negative self-bias voltage generated by plasma. In a plasma processing apparatus configured to electrostatically chuck a substrate on a substrate mounting table by superimposing and applying a large negative DC voltage to a high frequency, the high-frequency application electrode is provided below the substrate mounting table. A substrate push-up pin having conductivity and electrically insulated from the substrate mounting base is provided so as to be able to protrude and retract through the substrate mounting table, and the substrate push-up pin is retracted by a spring. Along with the substrate push-up pins, a conductive push-up member for projecting the substrate push-up pins is provided opposite to each other via a gap, and the push-up member is It is characterized by being electrically connected to the high frequency applying electrode.

A high-frequency power supply and a DC power supply for superimposing a DC voltage are connected to the high-frequency application electrode, and these power supplies are preferably configured so that the high-frequency power supply is cut off after the DC power supply is cut off. desirable.

[0013]

In the plasma processing method according to the present invention, the DC voltage for the electrostatic chuck is cut off before the high-frequency discharge is cut off, so that the self-bias voltage generated by the plasma is applied to the substrate. The state in which the potential on the high-frequency electrode side changes from a negative potential state compared to the self-bias voltage to a ground potential, that is, a positive potential from the self-bias voltage, and a reverse voltage is applied just between the dielectric films. The value of the reverse voltage is the self-bias voltage, which is close to the voltage required for desorption, and neutralizes the charge remaining on the dielectric film. As a result, the substrate can be easily detached from the substrate mounting table in a short time.

Further, according to the plasma processing apparatus of the present invention, by moving the push-up member to the upper substrate push-up pin side, the substrate push-up pin can be projected from the upper surface of the substrate mounting table against the spring. it can. At this time, the push-up member and the substrate push-up pin change from a state of being electrically insulated through the gap to a state of being electrically conductive, so that the substrate push-up pin, the push-up member, and the high-frequency application electrode are electrically disconnected from the substrate. Thus, it is possible to discharge the adsorbed charges that may be left between the substrate and the substrate mounting table to the ground potential side.

If the DC power supply is cut off among the high-frequency power supply and the DC power supply connected to the high-frequency application electrode, the high-frequency application electrode becomes the ground potential through the resistance of the cooling water,
Since the potential changes to a positive potential with respect to the self-bias voltage of the plasma, the potential can be reversed from the negative potential when the DC power is turned on, as in the above-described plasma processing method, and remains in the dielectric film. The charge can be neutralized.

[0016]

FIG. 1 is a schematic sectional view of an apparatus in which a plasma processing method according to the present invention is implemented by a single-wafer processing type parallel plate reactive ion etching apparatus. The high-frequency application electrode 2 insulated by the insulating material 15 and the grounded counter electrode 3 are installed with their electrode surfaces facing each other in parallel.

A substrate mounting table 4 made of alumina containing titanium oxide is provided above the high frequency application electrode 2. A metal electrode 5 is embedded inside the substrate mounting table 4 so as to be insulated from plasma, and is connected to the high frequency application electrode 2 in a DC manner. Between the metal electrode 5 embedded in the substrate mounting table 4 and the surface of the substrate mounting table 4, the main component is alumina having a thickness of approximately 300 μm and containing titanium oxide which is a part of the substrate mounting table 4. It is composed of a dielectric film. The surface of the substrate mounting table 4 other than the surface on which the substrate 14 is mounted is covered with an electrode cover 6 made of synthetic resin. On the side of the counter electrode 3 facing the substrate 14, a gas blowout plate 7 having small holes for blowing out a reactive gas in a lattice shape is attached.

A high frequency power supply 8 is connected to the high frequency application electrode 2 via a blocking capacitor 9, and a DC power supply 1 for an electrostatic chuck is further provided via a high frequency filter 10.
1 is connected. High frequency application electrode 2 and counter electrode 3
Indicates cooling water whose temperature is controlled independently.
The temperature is maintained at a constant value by flowing as shown in FIGS. When flowing the cooling water used in the examples,
The DC resistance between the high-frequency application electrode 2 and the vacuum vessel 1, which is a ground potential, is approximately 2 MΩ.

A case will be described below in which, for example, a silicon oxide film grown on a silicon substrate is patterned with a photoresist and etched using the apparatus having the above configuration.

The vacuum system 1 is evacuated to a vacuum by an exhaust system (not shown) connected to the exhaust port 12. Next, the substrate 14 is transferred into the vacuum vessel 1 by a robot or the like via a load lock mechanism (not shown), placed on the substrate placing table 4, and CHF ₃ and C ₂ F are supplied from the gas inlet 13. ₆
Is introduced until the pressure becomes 1 Torr.

Next, while cooling the high frequency applying electrode 2 with cooling water, a high frequency power of 13.56 MHz and 600 W is applied to the high frequency applying electrode 2 from the high frequency power supply 8 through the blocking capacitor 9. At the same time, a negative DC voltage of 500 V is superimposed on the high frequency application electrode 2 from the DC power supply for electrostatic chuck 11 via the high frequency filter 10.

When the high-frequency power is applied, plasma is generated in a space formed between the high-frequency application electrode 2 and the gas blowing plate 7, and a negative self-bias voltage (about 10
0V), ions are drawn from the plasma, and the substrate 14 is subjected to so-called reactive ion etching (RIE) by the interaction between the ions and active radicals generated by the plasma.

At this time, the high-frequency application electrode 2 and the metal electrode 5 embedded in the
Is applied by the DC power source 11 for the electrostatic chuck, the substrate 14 and the metal electrode 5 are sandwiched between the dielectric film mainly composed of alumina containing titanium oxide having a thickness of 300 μm. There is a potential difference between them. Therefore, the substrate 14 is electrostatically chucked to the substrate mounting table, and the substrate 1
4 is forcibly cooled by the high frequency application electrode 2 which is in close contact with the substrate mounting table 4 and is cooled by cooling water. Thereby, the temperature rise of the substrate 14 during the etching is suppressed low, and the silicon oxide film can be etched at a high speed while obtaining a high selectivity to silicon. further,
An etching profile having a forward tapered shape from a vertical direction is obtained.

When the end point of the etching is determined by an end point detector or the like at the end of the etching, first, the DC power supply 11 for the electrostatic chuck is turned off, and the high frequency power supply 8 is turned off after a lapse of 3 seconds or more. DC power supply for electrostatic chuck 1
Immediately after turning OFF 1, the self-bias voltage is induced on the substrate 14 because the plasma continues to be generated for 3 seconds or more, while the potential of the metal electrode 5 is set to the ground potential through the electric resistance of the cooling water. 300 μm thick
The electric charge induced in the vicinity of the substrate mounting surface of the dielectric film containing alumina as a main component containing titanium oxide can be eliminated by the reverse voltage. Therefore, the high frequency power supply 8
After turning OFF, the substrate 14 is very easily detached because the electrostatic attraction force does not work, and the unprocessed substrate to be etched next is transported by a robot or the like, and the processing on the substrate mounting table is completed. When replacing the substrate, a transfer error, breakage of the substrate, and the like can be avoided, and very reliable electrostatic chuck cooling can be realized.

The time from when the DC power supply 11 for the electrostatic chuck is turned off to when the high-frequency power supply 8 is turned off may be 3 seconds or more, but if it is too long, excessive over-etching will occur, resulting in device characteristics. Some unfavorable things also happen. If the time is less than 3 seconds, the charge induced in the dielectric film cannot be sufficiently eliminated, and the effect of the present invention will not be sufficiently exhibited. Therefore, practically, it is desirable to set this time to about 3 to 15 seconds.

In order to prevent excessive over-etching, it is also effective to reduce the power of the high-frequency power source 8 continuously or stepwise during the above time.

In this embodiment, a dielectric film having a thickness of 300 μm and containing titanium oxide as a main component is used as the dielectric film. This material is made of other ceramics such as barium titanate. Or a ferroelectric substance such as lead titanate, or a resin such as polyimide. Further, its thickness is not limited to 300 μm.

The voltage of the electrostatic chuck, the kind of gas, the high frequency power, the etching pressure, and the like used in the embodiment are not particularly limited to these values.

Further, the method of the present invention can be applied to other etching apparatuses, for example, a batch type apparatus, an ECR apparatus, and the like, and can exert its power. Plasma C
The present invention can be sufficiently applied to other plasma processing apparatuses such as a VD apparatus and a sputtering apparatus.

Next, an embodiment of the plasma processing apparatus of the present invention will be described with reference to FIG.

FIG. 2 is an enlarged view of the high-frequency application electrode 2 and the substrate mounting table 4.
A space 18 is formed at the center of the space 18, and the through holes 19, 1, 1 are penetrated through the top wall of the space 18 and the substrate mounting table 4.
9 (for example, six) are formed at regular intervals along the same circumference, and the substrate push-up pins 2 projecting or immersing into the upper surface of the substrate mounting table 4 through these through holes 19, 19.
0 and 20 are accommodated in the space 18. The substrate push-up pins 20, 20 are made of aluminum and have conductivity, and the lower end is made of an aluminum pin holder 2.
1 and supported by a spring 22 installed between the pin holder 21 and the top wall of the space 18.
The tip is always urged in the immersion direction so that the tip does not protrude from the upper surface of the substrate mounting table 4. The spring 22
Insulating materials 23, 23 are interposed between the portions that contact the pin holder 21 and the portions that contact the top wall, and the side surfaces and the lower peripheral edge of the pin holder 21 are covered with the insulating material 23. Pins 20 and 20 are through holes 1
The board push-up pins 20, 20 are in an electrically floating state in combination with the loose fit states of the boards 9, 19.

The portion of the high-frequency application electrode 2 that penetrates the vacuum vessel 1 is a cylindrical portion 2a, which communicates with the space 18. A metal bellows 24 is continuously provided on the outer end side of the cylinder upper portion 2a, and the outer end of the bellows 24 is sealed with a metal sealing plate 25 and the sealing plate 25
A push-up member 26 made of a metal rod is provided upright, and the upper end surface of the push-up member 26 is
Is opposed to the center of the lower surface with a gap 27 therebetween.
In the figure, 28 is a cooling water passage, and 29 is a shield.

The operation of the above embodiment will be described below. For example, a case where a silicon oxide film grown on a silicon substrate is patterned with a photoresist and etched is described below.

First, the inside of the vacuum vessel 1 is evacuated to a vacuum by a vacuum pump (not shown) connected to the exhaust port 12. Next, the substrate 14 is load-locked (not shown).
, And placed on the substrate mounting table 4, and a mixed gas of CHF ₃ and C ₂ F ₆ is introduced from the gas inlet 13 until the pressure becomes 1 Torr.

Then, while cooling the high-frequency applying electrode 2 with cooling water, a blocking capacitor 9 is supplied from the high-frequency power source 8.
The high frequency power of 13.56 MHz and 600 W is applied to the high frequency application electrode 2 via the. At the same time, a negative DC voltage of 500 V is superimposed on the high frequency application electrode 2 from the DC power supply for electrostatic chuck 11 via the high frequency filter 10.

When the high-frequency power is applied, plasma is generated in a space formed between the high-frequency application electrode 2 and the gas blowing plate 7, and a negative self-bias voltage (about 10
0V), ions are attracted from the plasma, and the interaction between the ions and active radicals generated by the plasma causes the substrate 14 to undergo a so-called reactive ion etching (RIE).

At this time, the high frequency application electrode 2 and the metal electrode 5 embedded in the substrate mounting table 4 having the same potential as this
A negative DC voltage of 00 V is applied to the DC power supply 11 for the electrostatic chuck.
, A potential difference is generated between the substrate 14 and the metal electrode 5 via the dielectric film 4a mainly composed of alumina containing titanium oxide having a thickness of 300 μm. For this reason, the substrate 14 is electrostatically chucked to the substrate mounting table 4,
The substrate 14 is forcibly cooled through the substrate mounting table 4 under the high-frequency application electrode 2 cooled by the cooling water. As a result, the temperature rise of the substrate 14 during the etching can be suppressed low, the silicon oxide film can be etched at a high speed while obtaining a high selectivity to silicon, and the etching profile has a vertical to forward tapered shape. Things are obtained.

When the end point of the etching is determined by an end point detector or the like at the end of the etching, first, the DC power supply 11 for the electrostatic chuck is turned off, and after a predetermined time (3 to 15 seconds), the high frequency power supply 8 is turned off. I do. Turn off high frequency discharge
Before turning off the DC voltage superimposed on the high frequency,
With a self-bias voltage applied to the substrate 14,
The potential on the high frequency application electrode 2 side is compared with the self-bias voltage, and the ground potential is changed from the negative potential state through the cooling water resistance.
That is, the potential changes to a positive potential from the self-bias voltage. This is a state in which a reverse voltage has just been applied between the dielectric films 4a, and the value of the reverse voltage is a self-bias voltage, which is close to the voltage required for attaching and detaching the substrate 14, so that the residual voltage remains on the dielectric film. Neutralize the charge. Next, the substrate is detached by using the substrate push-up pins 20. At this time, since the substrate push-up pins 20 come into contact with the push-up member 26 and have the same potential as the high-frequency application electrode 2, the substrate push-up pins 20 Upon contact, the charge remaining on the substrate can be quickly removed. Therefore, the substrate 14 can be easily attached and detached. When an unprocessed substrate to be etched next is transferred by a robot or the like and replaced with the processed substrate 4 on the substrate mounting table 4, a transfer error or a substrate Can be suppressed, and very reliable electrostatic chuck cooling can be realized.

The substrate 14 by the substrate lifting pins 20
The push-up member 26 vacuum-sealed by the metal bellows 24 is driven by a piston or the like from the outside via the sealing plate 25. The pin holder 21 is pushed up by the push-up member 26, whereby the substrate push-up pins 20 are projected above the substrate mounting table 4, whereby the substrate 14 is detached from the substrate mounting table 4. Push-up member 26 and pin holder 2
1 is made of a conductive metal, and when the substrate 14 is pushed up, the electric charge remaining on the substrate 14 is transferred to the substrate pushing up pins 20, the pin holder 21, the pushing up member 26, and the sealing plate 2.
5. Flow through the metal bellows 24 to the high frequency applying electrode 2,
Furthermore, it flows to the ground side through the cooling water. Therefore, the substrate 1
4 can be easily detached from the substrate mounting table 4 without damaging the substrate 14.

At the end of the etching, the DC voltage O
After the FF, a case where the high-frequency voltage is turned off after a certain time has elapsed, and then the substrate 14 is detached with the substrate push-up pin 20 has been described.
It is also possible to remove the charge remaining on the substrate 14 by setting the substrate to the FF and then lifting the substrate lifting pin 20.

In this embodiment, a dielectric film mainly composed of alumina containing titanium oxide having a thickness of 300 μm is used as the dielectric film 4a, but this material is made of another ceramic such as titanic acid. It may be a ferroelectric such as barium or lead titanate, a resin such as polyimide, or simply an aluminum oxide film. Further, the thickness is not limited to 300 μm.

The voltage, etching material, gas type, high frequency power, etching pressure and the like of the electrostatic chuck used in the embodiment are not particularly limited to these values.

The substrate push-up pins 2 used in the embodiment
The material of No. 0 and the structure of the push-up mechanism are not limited to this. In particular, the material of the substrate push-up pin 20 is more effective to use, for example, glassy carbon or silicon carbide in order to avoid metal contamination. is there.

Further, the present invention relates to another etching apparatus,
For example, it can be applied to a batch type device, an ECR device, and the like to exert its power, and besides, a plasma CVD device.
The present invention can be applied to other plasma processing apparatuses such as a sputtering apparatus and a sputtering apparatus.

[0045]

According to the method of the present invention, the substrate can be detached with high reliability after the plasma processing is performed while sufficiently cooling the substrate by the electrostatic chuck, so that the substrate is not damaged. Therefore, a plasma processing method which can perform highly reliable plasma processing and is excellent in substrate transfer reliability is provided.

Further, according to the apparatus of the present invention, after the plasma processing of the substrate subjected to the electrostatic chuck is completed, the electric charge remaining on the substrate can be reliably removed, so that the substrate can be detached with high reliability. This has the effect of eliminating the possibility of breakage. Therefore, there is an effect that a good plasma processing can be performed by using the electrostatic chuck, and a plasma processing apparatus excellent in reliability of substrate transfer can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part of a reactive ion etching apparatus used in an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a portion of a high-frequency application electrode according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 High frequency application electrode 3 Counter electrode 4 Substrate mounting table 4a Dielectric film 5 Metal electrode 8 High frequency power supply 11 DC power supply 14 Substrate 19 Through hole 20 Substrate push-up pin 21 Pin holder 22 Spring 23 Insulation material 24 Metal bellows 25 Sealing plate 26 Push-up member 27 Air gap

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-110927 (JP, A) JP-A-63-56920 (JP, A) JP-A-1-189124 (JP, A) JP-A-2-110 69956 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 C23C 16/509 H01L 21/205 H01L 21/68

Claims (2)

(57) [Claims] A high-frequency applying electrode is provided in a vacuum vessel provided with a gas introducing means such as a reactive gas, and a dielectric film is provided on the high-frequency applying electrode, and the high-frequency applying electrode is covered with the dielectric film. A substrate mounting table in which a metal electrode with the same potential as that of the substrate is embedded is provided, and during plasma processing, a negative DC voltage, whose absolute value is larger than the negative self-bias voltage generated by the plasma, is applied to the high-frequency application electrode by superimposing it on the high frequency By doing so, in a plasma processing apparatus configured to electrostatically chuck the substrate on the substrate mounting table, a substrate push-up pin having conductivity and electrically insulated from the high-frequency application electrode below the substrate mounting table, The substrate push-up pin is provided so as to be able to protrude and retract through the substrate mounting table, and the substrate push-up pin is urged in a retracting direction by a spring. A plasma processing apparatus characterized in that a push-up member having conductivity for projecting a substrate push-up pin is provided opposite to the air gap, and the push-up member is electrically connected to the high frequency application electrode. . Wherein the powered electrode DC frequency power source power supply is connected, after the DC power supply is cut off, continued plasma processing apparatus according to claim 1, wherein the RF power is provided a structure for blocking.