JP2010090439A - Vacuum treatment method for substrate made from piezoelectric material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum treatment method for a substrate made from a piezoelectric material. <P>SOLUTION: This vacuum treatment method includes measuring the polarity and magnitude of electrostatic voltage of the surface of a treatment substrate 15 made from the piezoelectric material under plasma for treatment as a prior process, before an adsorption device 30 adsorbs the treatment substrate 15 in a vacuum treatment device 1 in plasma treatment which is a main process. In the main process, when the voltage of the surface of the treatment substrate 15 measured in the prior process is 1 kV or more, zero V is applied to electrodes 111 and 112, and when the voltage is less than 1 kV, a voltage having a reverse polarity to the polarity of the electrostatic voltage of the surface of the treatment substrate 15 measured in the prior process is applied to the electrodes 111 and 112. Thereby, the treatment substrate 15 is adsorbed. When the treatment substrate 15 is larger than the surface of the adsorption device 30, a metallic thin film is formed on the whole back surface to lower the temperature of the substrate by thermal conduction. The vacuum treatment method also includes arranging a guard ring 18 in the upper part of the outside of the treatment substrate 15 to prevent heat from flowing to the treatment substrate 15 from plasma and prevent a crack of the treatment substrate 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for vacuum processing while adsorbing a substrate, and more particularly to a technique for vacuum processing a substrate made of a piezoelectric body under plasma.

  Reference numeral 100 in FIG. 2 denotes a vacuum apparatus that performs film formation processing on the substrate by sputtering, and includes a vacuum chamber 110.

  An adsorption device 130 is disposed inside the vacuum chamber 110. The adsorption device 130 is a bipolar adsorption device, and includes a positive electrode 111 and a negative electrode 112, and an insulating portion 113 is disposed on the positive electrode 111 and the negative electrode 112. Here, positive and negative electrodes 111 and 112 are disposed inside the insulating portion 113.

  A positive voltage power supply 121 and a negative voltage power supply 122 are disposed outside the vacuum chamber 110, and the positive electrode 111 and the negative electrode 112 are connected to the positive voltage power supply 121 and the negative voltage power supply 122, respectively. Is configured to be able to apply a positive voltage and a negative voltage to the negative electrode 112.

  An evacuation system 123 and a gas introduction system 125 are connected to the vacuum chamber 110. The inside of the vacuum chamber 110 is evacuated by the evacuation system 123, and the substrate 114 is loaded and placed on the insulating portion 113. When positive and negative voltages are applied to the electrodes 111 and 112, when the substrate 114 is a conductive material such as a metal or a semiconductor, a capacitor is formed between the positive electrode 111 and the negative electrode 112 and the substrate 114. It is attracted to the electrode 111 and the negative electrode 112.

  When the substrate 114 is a dielectric such as a glass substrate and no capacitor is formed between the positive and negative electrodes 111 and 112 and the substrate 114, the substrate 114 is placed in a non-uniform electric field E, assuming that the polarizability of the substrate 114 is α. When placed, the adsorption force of the gradient force F is applied to the substrate 114 according to the following equation (1).

F = 1/2 ・ α ・ grad (E ² ) (1)
A target 126 is disposed on the ceiling side of the vacuum chamber 110, and a sputtering power source 127 is disposed outside the vacuum chamber 110. The substrate 114 is adsorbed to the positive and negative electrodes 111 and 112, and then sputtered from the gas introduction system 125. When a gas is introduced and a voltage is applied to the target 126 by the sputtering power source 127 to generate plasma near the surface of the target 126 and the target 126 is sputtered, a thin film is formed on the surface of the substrate 114.

  As described above, when the substrate 114 is a conductor or dielectric, the substrate 114 is in close contact with the insulating portion 113, and heat flowing from the plasma flows out to the adsorption device 130 side, or the substrate 114 is moved by the heater disposed in the insulating portion 113. Can be heated.

  However, when the substrate 114 is a piezoelectric body, the spontaneous polarization due to the adsorption force applied to the substrate 114 or the spontaneous polarization due to the charge-up from the plasma disturbs the electric field formed by the positive and negative electrodes 111 and 112, and the substrate 114 is adsorbed. However, there is a problem that the temperature rises without being performed, or the adsorption force applied to the substrate 114 becomes non-uniform, causing the substrate to crack.

The following is a document describing a technique for adsorbing a dielectric.
JP 2001-035907 A JP 2001-042662 A JP 2003-133400 A

  During the vacuum processing step, the substrate 114 is charged with a negative polarity due to charge-up from the processing plasma, and the adsorption force of the portion located on the negative electrode 112 on the surface of the insulating portion 113 is weakened.

  In the case where the substrate 114 is a piezoelectric body, when the temperature of the substrate 114 rises due to heat inflow from plasma, the polarization is spontaneously changed, the degree of polarization changes, and a voltage is generated by the adsorption force to spontaneously polarize. Changes and the adsorption power becomes weaker. It is considered that the adsorption force becomes weak because the electric field change is disturbed in the substrate 114 and the electric field that can be normally adsorbed does not reach the substrate 114.

  Further, when the surface area of the substrate 114 in close contact with the insulating portion 113 is larger than the surface area of the insulating portion 113 in close contact with the substrate 114, if heat from the processing plasma flows into the substrate 114 during vacuum processing by plasma, the central portion of the substrate 114 Decreases to the insulating portion 113 due to heat conduction, but heat is not released from the outer peripheral portion, and a temperature difference occurs between the central portion and the outer peripheral portion. As a result, a difference in thermal stress occurs between the central portion and the outer peripheral portion of the substrate 114, and the substrate 114 is cracked.

Sputtering was performed using the vacuum processing apparatus 100 under the following conditions.
Substrate 114: substrate made of piezoelectric material (LiTaO ₃ ) having a diameter of 4 inches Applied voltage to positive electrode 111: + 2000V
Applied electrode to the negative electrode 112: -2000V
Target 126: Ni
Sputtering power: 1kW
Thin film formed on substrate 114: Ni thin film with a thickness of 1 μm

The vacuum processing apparatus 100 includes a temperature measurement device 119 and a voltage measurement device 128, and is configured to measure the temperature and the polarity and magnitude of the charging voltage at a plurality of locations on the substrate 114.
When the surface temperature of the substrate 114 was measured by the temperature measuring device 119 during the sputtering process of the Ni thin film under the above conditions, the in-plane temperature distribution was 27 ° C. or higher, and the substrate 114 was cooled by the spontaneous polarization effect of the substrate 114. The effect became worse.
Further, the temperature of the portion directly above the positive electrode 111 was 43 ° C. or lower, and the temperature of the portion directly above the negative electrode 112 increased to 87 ° C.

  As described above, the temperature on the positive electrode 111 side is lower than the temperature on the negative electrode 112 side because the adsorption force between the positive electrode 111 and the substrate 114 is greater than the adsorption force between the negative electrode 112 and the substrate 114. It is considered that the amount of heat that flows from the plasma into the substrate 114 flows out to the insulating portion 113 is larger on the positive electrode 111 side than on the negative electrode side.

The reason why the adsorption force on the positive electrode 111 side is strong is considered to be that the substrate 114 is charged to a negative potential due to charge-up from the plasma.
When the charging voltage of the substrate 114 was measured by the voltage measuring device 128 after the film forming process was completed, it was -500 V, and it was charged to a negative potential.

Therefore, the potential difference between the substrate 114 and the positive electrode 111 is 2500 V, and the potential difference between the substrate 114 and the negative electrode 112 is 1500 V. As a result, the potential difference between the positive electrode 111 and the substrate 114 increases, and as a result, the adsorption force increases. .
When there are positive and negative electrodes, the temperature in the surface of the substrate 114 becomes non-uniform.

The present invention is an invention conceived from the experimental results as described above, and has one or more electrodes and an insulating portion disposed on the electrodes, and an adsorption device disposed in a vacuum chamber A processing substrate is disposed on the insulating portion, a voltage is applied between the electrode and the processing substrate, and plasma is generated in the vacuum chamber while adsorbing the processing substrate to the surface of the insulating portion in a vacuum atmosphere. A vacuum processing method for generating and vacuum processing a plurality of processing substrates, wherein when the processing substrate is made of a piezoelectric material, the same material as the processing substrate is formed on the insulating portion before the vacuum processing is performed. The measurement substrate is placed and plasma is generated in a vacuum atmosphere. Then, the polarity and magnitude of the charging voltage of the measurement substrate are measured. If the charging voltage is 1 kV or more, the processing substrate is subjected to the vacuum processing. The electrode is connected to ground potential. Wherein when the charging voltage is less than 1kV is the electrode from said charging voltage a vacuum processing method for applying a reverse polarity voltage.
Further, in the present invention, when the vacuum processing is performed on the processing substrate that is larger than the surface of the insulating portion and whose periphery protrudes from the surface of the insulating portion, before the vacuum processing is performed, This is a vacuum processing method for forming a metal thin film.
Further, in the present invention, when the vacuum processing is performed on the processing substrate that is larger than the surface of the insulating part and whose periphery protrudes from the surface of the insulating part, a protective ring is disposed on the part protruding from the insulating part. And a vacuum processing method in which the protective ring is positioned between the protruding portion and the plasma.

  A substrate made of a piezoelectric material can be uniformly adsorbed. Further, the temperature of the substrate can be controlled, and vacuum processing can be performed without breaking the substrate.

  Reference numeral 1 in FIG. 1 is an example of a vacuum processing apparatus capable of performing the vacuum processing method of the present invention. The vacuum processing apparatus 1 has a vacuum chamber 10. An adsorption device 30 is disposed on the bottom surface inside the vacuum chamber 10.

A target 26 is disposed inside the vacuum chamber 10 on the ceiling side. A sputtering power source 27 is disposed outside the vacuum chamber 10, and the target 26 is connected to the sputtering power source 27.
A vacuum exhaust system 23 and a gas introduction system 25 are connected to the vacuum chamber 10.

  After the inside of the vacuum chamber 10 is evacuated by the evacuation system 23, the processing substrate 15 is carried into the vacuum chamber 10, the processing substrate 15 made of a piezoelectric material is disposed on the adsorption device 30, and sputtering is performed by the gas introduction system 25. When gas is introduced into the vacuum chamber 10, the sputtering power supply 27 is activated to apply a voltage to the target, and plasma is formed near the surface of the target 26, the target 26 is sputtered and a thin film is formed on the surface of the processing substrate 15. A vacuum treatment for forming can be performed.

The adsorption device 30 includes one or more (two in this case) first and second electrodes 11 ₁ and 11 _2, and an insulation disposed above the first and second electrodes 11 ₁ and 11 _2. Part 13 is provided. Here, the insulating part 13 is plate-shaped, and when the first and second electrodes 11 ₁ and 11 ₂ are arranged inside the insulating part 13 and the processing substrate 15 is arranged on the suction device 30, the processing substrate 15 is insulated. It is comprised so that the part 13 may be contacted.

An adsorption power source 21 is disposed outside the vacuum chamber 10, and the first and second electrodes 11 ₁ and 11 ₂ are connected to the adsorption power source 21, and the first and second electrodes 11 ₁ and 11 ₂ include , The same potential voltage or different voltages can be applied.

<Previous process>
When the vacuum processing is performed, if the processing substrate 15 is adsorbed to the adsorption device 30, the processing substrate 15 can be precisely heat-treated.

When the processing substrate 15 is a piezoelectric body, the polarity and magnitude of the charging voltage change due to the material of the processing substrate 15, charge-up from plasma, or spontaneous polarization of the processing substrate 15, and the adsorption state changes. If the same voltage is applied to the second electrodes 11 ₁ and 11 ₂ as the case where a dielectric is adsorbed, temperature control becomes difficult.

Therefore, when vacuum processing a plurality of processing substrates 15, first, the same material as the processing substrate 15 is used to determine the polarity and magnitude of the voltage applied to the first and second electrodes 11 ₁ , 11 _2. The measurement substrate 14 is placed on the insulating portion 13 of the adsorption device 30, plasma is formed in the vacuum chamber 10 under the same conditions as the vacuum processing for the processing substrate 15, and the same vacuum processing as that used for the processing substrate 15 is performed. Perform vacuum processing under conditions.

  After vacuum processing is performed on the measurement substrate 14 under the same conditions as the processing substrate 15, the plasma is extinguished, and the polarity and magnitude of the charging voltage of the measurement substrate 14 are measured by the voltage measurement device 28.

The treatment substrate 15 is composed of lithium tantalate (LiTaO ₃ ), lithium niobate (LiNbO ₃ ), lithium tetraborate (LBO), crystal (SiO ₂ ), zinc oxide (ZnO), lead zirconate titanate (PZT: Pb). (Zr, Ti) O ₃ ), lithium tetraborate (Li ₂ B ₄ O ₇ ), langasite (La ₃ Ga ₅ SiO ₁₄ ), aluminum nitride (AlN), tourmaline (tourmaline), polyvinylidene fluoride (PVDF) The measurement substrate 14 is made of the same material as the processing substrate 15.

When the measured charging voltage is 1 kV or more, the processing substrate 15 can be adsorbed to the adsorption device 30 even if the potential difference between the first and second electrodes 11 ₁ , 11 ₂ and the processing substrate 15 is the charging voltage. When the substrate 15 is vacuum processed, the connection of the first and second electrodes 11 ₁ and 11 ₂ is connected to the ground potential, and is set so that a voltage of zero V is applied.

When the magnitude of the charging voltage of the measurement substrate 14 is less than 1 kV, it is provided in the adsorption device 30 in order to increase the potential difference between the processing substrate 15 and the first and second electrodes 11 ₁ and 11 ₂ . A voltage having a polarity opposite to the charging voltage is applied to the plurality of electrodes (first and second electrodes 11 ₁ and 11 _{2 in} this example).

Further, each electrode in the adsorption device 30 (first and second electrodes 11 ₁ and 11 _{2 in} this example) is set to be applied with the same voltage so that the processing substrate 15 is uniform in the surface. It is made to adsorb | suck on the insulation part 13 with an attractive force.

<This process>
As described above, the voltage applied from the suction power source 21 is set to each electrode (first and second electrodes 11 ₁ and 11 _{2 in} this example) in the suction device 30, and the plurality of processing substrates 15 are vacuum processed. In order to adsorb the processing substrate 15 carried into the vacuum chamber 10, a voltage set to the first and second electrodes 11 ₁ and 11 ₂ is applied to adsorb the processing substrate 15 uniformly, When the vacuum processing is performed, the processing substrate 15 is not easily broken because it is uniformly strongly adsorbed.

A processing substrate 15 made of LiTaO _{3 having a} diameter of 4 inches is placed on the adsorption device 30, and a voltage of 2000 V is applied to both the first and second electrodes 11 ₁ and 11 ₂ for adsorption. When the surface temperature of 15 was measured, the in-plane temperature distribution was 5 ° C. or less. Moreover, the crack of the processing board | substrate 15 did not generate | occur | produce.

  If the surface area of the processing substrate 15 is larger than the surface area of the insulating portion 13 and the processing substrate 15 is arranged on the insulating portion 13, the peripheral portion of the processing substrate 15 protrudes outside the insulating portion 13. As a result, the temperature of the protruding portion is higher than the temperature of the portion on the insulating portion 13, so that the adsorption force becomes non-uniform due to the spontaneous polarization generated inside the processing substrate 15, and cracking may occur.

  In this case, a thermal conductive thin film made of metal or the like is formed in advance on the back surface of the processing substrate 15 and then the above vacuum processing is performed, whereby the in-plane heat distribution of the processing substrate 15 becomes uniform and cracks do not occur.

  Further, in order to prevent heat from flowing in from the plasma, a protective ring 18 is provided so as to cover the surface of the portion of the processing substrate 15 that protrudes from the insulating portion 13, so that the peripheral portion of the processing substrate 15 does not come into contact with the plasma. The inflow of heat in the surface of the processing substrate 15 may be made uniform.

  In the above embodiment, the vacuum treatment of the present invention is a film formation process by sputtering. However, the vacuum treatment of the present invention is not limited thereto, and a vacuum for forming plasma such as etching, annealing, and surface treatment. Includes processing.

Sectional drawing explaining an example of the vacuum processing apparatus using the adsorption | suction apparatus of this invention Sectional drawing explaining an example of the vacuum processing apparatus using the conventional adsorption | suction apparatus

Explanation of symbols

1 ...... vacuum processing apparatus 10 ...... vacuum chamber 11 _1, 11 ₂ ...... electrodes 13 ...... insulating portion 15 ...... substrate 18 ...... protective ring 28 ...... voltage measuring device 30 ...... adsorber

Claims (3)

Having one or more electrodes and an insulating portion disposed on the electrode, and disposing a processing substrate on the insulating portion of the adsorption device disposed in the vacuum chamber;
A voltage is applied between the electrode and the processing substrate, and plasma is generated in the vacuum chamber while the processing substrate is adsorbed on the surface of the insulating portion in a vacuum atmosphere to vacuum-process the plurality of processing substrates. A vacuum processing method comprising:
When the processing substrate is made of a piezoelectric material,
Before performing the vacuum processing, a measurement substrate made of the same material as the processing substrate is placed on the insulating portion, and after generating plasma in a vacuum atmosphere, the polarity and magnitude of the charging voltage of the measurement substrate are measured. ,
When the charging voltage is 1 kV or more, the electrode is connected to a ground potential when the processing substrate is vacuum processed,
A vacuum processing method in which, when the charging voltage is less than 1 kV, a voltage having a polarity opposite to the charging voltage is applied to the electrode.   When performing the vacuum processing on the processing substrate that is larger than the surface of the insulating portion and whose periphery protrudes from the surface of the insulating portion, a metal thin film is formed on the back surface of the processing substrate before performing the vacuum processing. The vacuum processing method according to claim 1.   When the vacuum processing is performed on the processing substrate that is larger than the surface of the insulating portion and whose periphery protrudes from the surface of the insulating portion, a protective ring is disposed on the portion protruding from the insulating portion, and the protruding portion and the The vacuum processing method according to claim 1, wherein the protective ring is positioned between plasmas.

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