JP6594664B2 - Plasma processing equipment - Google Patents

Description

The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus including an inductively coupled plasma source.

In the field of semiconductor device manufacturing, an inductively coupled plasma (ICP) plasma apparatus is used for sample etching and surface treatment.

  As a conventional inductively coupled plasma processing apparatus, Patent Document 1 discloses a vacuum processing chamber that forms a part of a vacuum processing chamber 2 and includes a processing gas blowout port and an upper portion of the gas ring. Formed on the bell jar 12, antennas 1a and 1b for generating a plasma by supplying a high-frequency electric field to the vacuum processing chamber, and a mounting table 5 for mounting the sample 13 in the vacuum processing chamber. And a Faraday shield 8 disposed between the antennas 1a and 1b and the bell jar 12 and to which a high-frequency bias voltage is applied, and a deposition plate removably attached to the inner surface of the gas ring excluding the processing gas blowing port. The plasma treatment in which the area of the inner surface of the gas ring including the deposition plate that can be seen from the sample surface is set to be approximately ½ or more of the area of the sample Location is disclosed.

In the above plasma processing apparatus, a highly corrosive processing gas such as chlorine or fluorine is often used depending on the film type of the sample to be etched. For this reason, the materials of the vacuum processing chamber 2 and the bell jar 12 are required to have corrosion resistance against corrosive gases, and ceramics such as alumina (Al ₂ O ₃ ) having good dielectric properties are generally used. .

JP 2004-235545 A Japanese Patent Laying-Open No. 2015-022855 JP 2003-282754 A JP 2005-191314 A

In an inductively coupled plasma etching apparatus having a structure in which the outer periphery of a dielectric vacuum window as shown in FIG. 8 is supported by a stainless steel vacuum vessel, when the dielectric vacuum is etched under etching conditions with high plasma heat input. There was a phenomenon that the window was damaged. In order to elucidate this phenomenon, the temperature of the dielectric vacuum window in the presence of plasma heat input was investigated.

  FIG. 8 shows a temperature distribution generated in the plane of the dielectric window 2 when plasma heat input equivalent to 500 W is applied to an alumina vacuum window (hereinafter referred to as a dielectric window). Here, the horizontal axis in the figure indicates the radius of the dielectric window 2, and the vertical axis indicates the temperature of the dielectric window 2. Note that 0 mm on the horizontal axis indicates the center of the dielectric window 2, and 200 mm indicates the outermost periphery of the dielectric window 2.

  When high-power plasma heat input is applied to the dielectric window 2, the temperature at the center of the dielectric window 2 is high as shown in FIG. 8, and the temperature gradually increases toward the outer periphery of the dielectric window 2. A temperature distribution that would be low occurred in the dielectric window 2. The temperature distribution of the dielectric window 2 is due to the fact that the outer periphery of the dielectric window 2 is supported by a stainless steel chamber 1, the chamber 1 has a high thermal conductivity, and the alumina has a low thermal conductivity. it is conceivable that.

  Furthermore, due to the temperature difference in the surface of the dielectric window 2 due to this temperature distribution, the central portion of the dielectric window 2 having a high temperature tends to expand more than the outer peripheral portion having a low temperature. Compressive stress is generated in the circumferential direction, and tensile stress is induced in the circumferential direction of the outer peripheral portion of the dielectric window 2 by the compressive stress in the central portion. This stress distribution is qualitatively shown in FIG. In general, alumina is resistant to compressive stress and weak to tensile stress. For these reasons, the damage to the dielectric window 2 when the plasma heat input is large is caused by excessive tensile stress generated in the circumferential direction of the outer peripheral portion of the dielectric window 2.

Therefore, in order to prevent the dielectric window 2 from being damaged due to the excessive tensile stress, it is necessary to make the temperature distribution generated in the plane of the dielectric window 2 uniform. That is, the in-plane temperature difference of the dielectric window 2 must be reduced. In this method, it is necessary to adjust the temperature of the entire dielectric window 2. For example, as described in Patent Document 2, (1) temperature rise portion of the dielectric window 2 = compressed stress generating portion (dielectric window) 2), cooling air is blown to the center part of the battery 2 to cool it.
(2) The outer peripheral portion of the dielectric window 2 = the tensile stress generating portion is directly or indirectly heated with a heater.
It is possible.

  Both are effective methods for uniforming the temperature distribution. However, regarding the heater heating in (2), if the members constituting the heater are hard (metal, ceramics, etc.), the heater and the dielectric window 2 are heated thermally. There is a problem that the contact is poor and it is difficult to heat efficiently. There are two causes for this. One is that the dielectric window 2 and the members constituting the heater are hard, so that even if they are configured so as to be in contact with the macro, they are only in point contact with the micro. The remaining one is that the linear expansion coefficient when the temperature changes is different, so that it is difficult to make a configuration that always maintains a good contact state in a desired temperature range.

  Therefore, the present invention provides a plasma processing apparatus capable of suppressing the damage of the dielectric window due to plasma heat input that overcomes the above-described problems.

The present invention is arranged above a metal processing chamber in which a sample is subjected to plasma processing, a dielectric window that hermetically seals the upper portion of the processing chamber, and the disk-shaped dielectric window. an induction antenna causing induced magnetic field, the plasma processing apparatus and a high frequency power supply for supplying high frequency power to said inductive antenna, the disposed outside the dielectric window, and a metallic crimp in the dielectric window A ring-shaped member is further provided , and the linear expansion coefficient of the ring-shaped member is larger than the linear expansion coefficient of the dielectric window, and the ring-shaped member has a refrigerant flow path for adjusting the temperature. It is characterized by.

According to the present invention, damage to the dielectric window due to plasma heat input can be suppressed.

It is a figure which shows the outline of the plasma processing apparatus which concerns on this invention. It is a top view of the compression ring 9 of the present invention. It is a side view of the compression ring 9 of the present invention. It is a figure which shows the relationship between the internal diameter of the compression ring 9 of this invention, and the outer diameter of the dielectric material window 2. FIG. It is a figure which shows the internal stress of the compression ring 9 and the dielectric material window 2. FIG. It is a figure which shows the temperature dependence of the internal stress of the compression ring. It is a figure which shows the outline of embodiment which temperature-controls the compression ring 9 with a refrigerant | coolant. It is a figure which shows the temperature distribution and qualitative stress distribution which generate | occur | produce in the surface of a dielectric material window when a plasma heat input is given to a dielectric material window.

FIG. 1 is a longitudinal sectional view of an inductively coupled plasma processing apparatus according to the present invention. A top dielectric window 2 for hermetically sealing the chamber 1 is attached to the upper opening of the cylindrical chamber 1 to constitute a vacuum processing chamber. A sample stage 5 for placing a sample 3 such as a wafer is installed below the vacuum processing chamber. The chamber 1 is made of a metal such as stainless steel or aluminum.

  By applying a high frequency to the sample 3 from the second high frequency power supply 10, the ion energy from the plasma 11 incident on the sample 3 is controlled. In this embodiment, the sample 3 is, for example, a 300 mm diameter wafer for a semiconductor device, and the second high frequency power source 10 uses a frequency 800 KHz power source.

  An exhaust port 12 is provided between the chamber 1 and the chamber 1. The pressure in the vacuum processing chamber can be controlled in the range of 0.1 Pa to several tens of Pa by an exhaust device (not shown) downstream of the exhaust port 12. A gas for generating plasma is introduced from a gas supply device 13 provided in the chamber 1 forming the vacuum processing chamber, and the processing gas is supplied from a circular opening on the side surface of the chamber 1.

The dielectric window 2 is made of a dielectric material capable of transmitting electromagnetic waves, for example, ceramic such as alumina (Al ₂ O ₃ ), quartz, and the like. In this embodiment, the dielectric window 2 made of alumina is used. A coiled induction antenna 4 is disposed above the dielectric window 2. In this case, as shown in FIG. 1, the induction antenna 4 has the first induction antenna 4a to the fourth induction antenna 4d of one turn having different inner diameters arranged concentrically. The inner diameters of the first induction antenna 4a to the fourth induction antenna 4d increase in the order of the first induction antenna 4a, the second induction antenna 4b, the third induction antenna 4c, and the fourth induction antenna 4d. Yes.

  The induction antenna 4 is connected to a first high frequency power source 7 via a matching unit 6. The first high frequency power supply 7 supplies high frequency power of 13.56 MHz or 27.12 MHz to the induction antenna 4, for example. A Faraday shield 8 is disposed between the induction antenna 4 and the dielectric window 2. In this case, the Faraday shield 8 is disposed on the upper surface of the dielectric window 2. The Faraday shield 8 is a conductor, and has a circular opening at the center as shown in FIG. 2, and has a plurality of slits radially around the circular opening. The Faraday shield 8 is connected to the first high-frequency power source 7 through the matching unit 6 and becomes a flat antenna that is capacitively coupled to the plasma 11. Furthermore, the dielectric window 2, the Faraday shield 8, and the induction antenna 4 are arranged concentrically and in parallel at a predetermined interval in the vertical direction.

As shown in FIGS. 2 and 3, a ring-shaped compression ring 9 is disposed on the side surface of the outer peripheral portion of the dielectric window 2. The conditions that the compression ring 9 should satisfy for the dielectric window 2 are shown below. First, as shown in FIG. 4 (1), the inner diameter _φr0 and the dielectric window 2 of the compression ring 9 placed in a stress-free state in the operating temperature range T _{L to} T _U of the dielectric window 2 and the compression ring 9. The relationship of the outer diameter _φW0 is _φr0 < _φW0 . Here the T _L the lower limit value of the operating temperature range of the dielectric window 2 and the compression ring 9, the T _U is the upper limit value of the operating temperature range of the dielectric window 2 and compression ring 9.

Next, in T ₁ is a temperature above Tu, as shown in FIG. 4 (2), the relationship between the inner diameter phi _r1 and the outer diameter phi _W1 of the dielectric window 2 compression rings 9 placed in the absence of stress, φ _r1 = φ _W1 . In order to satisfy this condition, the linear expansion coefficient of the material of the compression ring 9 needs to be larger than the linear expansion coefficient of the material of the dielectric window 2. For this reason, a metal material such as stainless steel, particularly high-tensile steel is suitable as the material of the compression ring 9.

When the compression ring 9 and the dielectric window 2 are raised to T ₂ which is a temperature higher than T ₁ , the inner diameter of the compression ring 9 placed in a stress-free state as shown in FIG. relationship of the outer diameter phi _W2 of phi _r2 and the dielectric window 2 becomes φ _r2> φ _W2.

Next, a method for attaching the compression ring 9 to the dielectric window 2 will be described. First, the dielectric window 2 and compression ring 9 is heated to a temperature T _2, after expanding the larger size of the compression ring 9 of the thermal expansion coefficient, encasing an dielectric window 2 to the compression ring 9, gradually cooling the entire . Becomes the temperatures T ₁ or less, the compression ring 9, as shown in FIGS. 2 and 3 are pressed against the outer periphery of the dielectric window 2. As a result, in the operating temperature range T _{L to} T _U , a compressive stress that cancels the tensile stress can be uniformly applied to the inside of the dielectric window 2 in advance.

  Next, the effect of the present invention will be described with reference to FIG. FIG. 5 (1) shows the stress distribution when there is no compression ring 9. When there is no temperature distribution, no stress is generated inside the dielectric window 2. However, when the plasma is ignited and the temperature of the central portion of the dielectric window 2 rises, the central portion tends to thermally expand. However, since the central portion is constrained by the outer peripheral portion of the dielectric window 2 (which does not attempt to thermally expand due to low temperature), it cannot expand sufficiently.

For this reason, compressive stress is generated in the constrained central portion, and tensile stress is generated in the constrained outer peripheral portion. This is the stress distribution σ _w in FIG. However, the total sum (volume integral) of the stress distribution σ _w inside the dielectric window 2 is zero.

FIG. 5 (2) shows the stress distribution when the compression ring 9 is pressure-bonded to the outer periphery of the dielectric window 2 in the operating temperature range T _{L to} T _U. When there is no temperature distribution in the dielectric window 2, a uniform tensile stress σ _t and a uniform compressive stress σ _p are generated in the compression ring 9 and the dielectric window 2, respectively. Here, the temperature distribution is generated in the dielectric window 2, also stress distribution sigma _w is generated. In this case, the relationship between these stress distributions is as follows.

Here, _Vw and _Vr are the volumes of the dielectric window 2 and the compression ring 9, respectively.

This equation means that the stress distribution σ _w is subjected to an offset compressive stress of σ _p . Only the sigma _p min tensile stress of the dielectric window 2 is reduced, thereby preventing damage due to tensile stress of the dielectric window 2.

  Patent Documents 3 and 4 disclose that the glass of the transmission window is shrink-fitted with a metal frame. However, the present invention utilizes the difference in linear expansion coefficient between the dielectric window 2 and the compression ring 9 and also measures the inner diameter of the compression ring 9 based on the tensile stress due to the temperature distribution of the dielectric window in the operating temperature range. It is characterized by prescribing. Next, the relationship between the tensile stress generated in the compression ring 9 and the temperature is shown in FIG.

Tensile stress is not generated in the compression ring 9 at a temperature above T _1. That is, if the temperature rises after the contact, it loosens and does not adhere, and compression stress cannot be applied. This is because if the temperature of the compression ring 9 and the dielectric window 2, as shown in FIG. 4 is above T _1, the inner diameter phi _r1 of the compression ring 9 is to become larger than the outside diameter phi _w1 of the dielectric window 2 . In order to prevent this, it is _advisable to monitor the temperature T _u or the stress σ _tu and give an alarm, or stop the plasma discharge. The monitoring device 14 in FIG. 1 monitors the temperature T _u or the stress σ _tu and turns on the first high-frequency power source 7 that is a discharge power source when the temperature becomes equal to or higher than the set value or the tensile stress becomes equal to or lower than the set value. Control to stop.

  In the present invention, since the compression ring 9 is made of a metal material, it is possible to easily dig a groove in the compression ring 9 and allow the refrigerant to pass through the circulator 15 that is a temperature control device. Therefore, it is more desirable to adjust the temperature of the compression ring 9 with a refrigerant. This is shown in FIG. By adjusting the temperature in this way, it is possible to prevent the compression ring 9 from reaching an undesired temperature range. In this case, it is better to metallize the outer peripheral side surface of the dielectric window 2 (the surface to be crimped to the compression ring 9).

The metallized layer 16 must be made of a metal material that is wetted by the dielectric window, and the metallized layer 16 has good heat transfer characteristics with the dielectric window 2. Furthermore, since the metallized layer 16 is softer than the dielectric window 2, it is in close contact with the metal compression ring 9. As a result, the compression ring 9 has good heat transfer characteristics with the dielectric window 2, and the temperature adjustment by the refrigerant works more effectively. In this case, the monitoring device 14 may monitor the stress σ _tu of the compression ring 9.

  Further, as described above, since the heat transfer characteristic of the dielectric window 2 is improved by metallizing the outer peripheral side surface of the dielectric window 2, the temperature distribution of the dielectric window 2 is improved. Due to this effect, the compression ring 9 can be made thinner than the compression ring 9 when the metallization process is not performed. In general, the roundness of the dielectric window of alumina is not always good. For this reason, the roundness of the dielectric window 2 is improved by metallizing the outer peripheral side surface of the dielectric window 2, and the stress of the dielectric window 2 is relieved. For this reason, the present invention in which the compression ring 9 is pressure-bonded to the outer periphery of the dielectric window 2 after metallizing the outer peripheral side surface of the dielectric window 2 without passing the refrigerant through the compression ring 9 is based on plasma heat input. This is a very practical and effective solution to dielectric window breakage.

DESCRIPTION OF SYMBOLS 1 Chamber 2 Dielectric window 3 Sample 4 Induction antenna 5 Sample stand 6 Matching device 7 First high frequency power supply 8 Faraday shield 9 Compression ring 10 Second high frequency power supply 11 Plasma 12 Exhaust port 13 Gas supply device 14 Monitoring device 15 Circulator 16 Metallized layer

Claims (6)

A metal processing chamber in which a sample is subjected to plasma processing, a dielectric window made of a dielectric material that hermetically seals the upper portion of the processing chamber, and a disk-shaped dielectric window are disposed above the dielectric window, and an induction magnetic field is generated. In a plasma processing apparatus comprising an induction antenna to be generated and a high-frequency power source that supplies high-frequency power to the induction antenna,
Wherein disposed outside the dielectric window further comprises a metal ring-shaped member which is crimped to the dielectric window,
The linear expansion coefficient of the ring-shaped member is larger than the linear expansion coefficient of the dielectric window,
The plasma processing apparatus, wherein the ring-shaped member is formed with a refrigerant flow path for adjusting temperature. A metal processing chamber in which a sample is subjected to plasma processing, a dielectric window made of a dielectric material that hermetically seals the upper portion of the processing chamber, and a disk-shaped dielectric window are disposed above the dielectric window, and an induction magnetic field is generated. In a plasma processing apparatus comprising an induction antenna to be generated and a high frequency power source for supplying high frequency power to the induction antenna,
Wherein disposed outside the dielectric window further comprises a metal ring-shaped member which is crimped to the dielectric window,
The linear expansion coefficient of the ring-shaped member is larger than the linear expansion coefficient of the dielectric window,
A plasma processing apparatus, wherein the outer periphery of the dielectric window is metallized. A metal processing chamber in which a sample is subjected to plasma processing, a dielectric window made of a dielectric material that hermetically seals the upper portion of the processing chamber, and a disk-shaped dielectric window are disposed above the dielectric window, and an induction magnetic field is generated. In a plasma processing apparatus comprising an induction antenna to be generated and a high frequency power source for supplying high frequency power to the induction antenna,
Wherein disposed outside the dielectric window, wherein the dielectric and the metal ring-shaped member which is crimped to the window, on the basis of the stress of temperature or monitored the ring-shaped member of the monitored the ring-shaped member RF A monitoring device for stopping the power supply ,
The plasma processing apparatus , wherein a linear expansion coefficient of the ring-shaped member is larger than a linear expansion coefficient of the dielectric window . In the plasma processing apparatus according to any one of claims 1 to 3,
When the temperature of the dielectric window is within a predetermined temperature range, the inner diameter of the ring-shaped member is smaller than the diameter of the dielectric window and based on tensile stress due to the temperature distribution of the dielectric window during the plasma processing. A plasma processing apparatus characterized by being defined. The plasma processing apparatus according to claim 4, wherein
When the temperature of the dielectric window is higher than the upper limit value of the predetermined temperature range, the inner diameter of the ring-shaped member is a value equal to or larger than the diameter of the dielectric window. In the plasma processing apparatus according to claim 1 or 2,
A plasma processing apparatus, further comprising a monitoring device that stops the high-frequency power source based on the monitored stress of the ring-shaped member.

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