JP3640386B2 - Pyroelectric high-dielectric etching method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an etching method and apparatus for processing a pyroelectric high dielectric constant material such as LiNbO ₃ or PZT that can be used in an optical modulator for an optical waveguide in plasma.
[0002]
[Prior art]
In this type of conventional etching apparatus, the surface of the substrate electrode is coated with an anodized film of 20 to 30 μm in consideration of corrosion resistance, the substrate pressing jig or clamp material is made of alumina, and the substrate pressing jig or clamp The back side remains the alumina substrate.
[0003]
Incidentally, the main purpose of the substrate holding mechanism in the conventional etching apparatus is to improve the thermal conductivity. Therefore, unlike a high dielectric constant material, there is no large gap between the surface potential and the back surface potential due to plasma irradiation, and high voltage (electrostatic) breakdown does not occur. Therefore, a substrate electrode structure capable of shape control and uniform etching is used. I wish I had it. In the prior art, it is found that slight undercut occurs when, for example, SiO ₂ is etched using a metal mask. SiO ₂ does not react with active species in plasma having no charge, and etching proceeds by ion bombardment. The mask metal is charged by a charge generated by a slight difference in the amount of ions and electrons reaching the surface, and a potential different from that inside the dielectric is generated. Therefore, it can be interpreted that the trajectory of incident ions is bent by the action of electric charges charged on the metal mask on the surface, and as a result, undercut occurs.
[0004]
In a dielectric having a low dielectric constant, such a slight undercut is generated and the problem of substrate cracking does not occur. However, it has been confirmed in many experiments that a dielectric material having a high dielectric constant has a large amount of charge and reaches electrostatic breakdown. In the experiment so far, when LiNbO ₃ was etched using Ar + C ₄ F ₈ plasma having a density of 10 ¹¹ cm ⁻³ , the substrate did not crack for 5 minutes, but cracked in 10 minutes. It was found that the cracks in the substrate were mainly caused by temperature unevenness and charge-up.
[0005]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an etching method and apparatus that eliminates temperature unevenness and charge-up, which are problems associated with the above-described conventional apparatus, and prevents the substrate from cracking.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a gas is introduced into a vacuum chamber to form a high-density plasma using microwaves or high-frequency waves, and pyroelectricity is formed on the substrate electrode. In an etching apparatus for processing a substrate by placing a substrate of a high dielectric material, a receiving surface recess for receiving the substrate to be processed is formed on the surface, and a back surface recess is formed on the back surface corresponding to the substrate receiving surface recess. A substrate tray made of aluminum having a peripheral contact surface portion surrounding the back surface recess and contacting the substrate electrode, and a plurality of gas flow passages penetrating from the back surface recess to the substrate receiving surface recess. The substrate is fixed on the substrate tray by a clamp ring when mounted, and the cooling gas can be mainly flowed to the surface side of the substrate tray.
[0007]
The height from the concave portion on the back surface of the substrate tray to the peripheral contact surface portion can be set to 5 to 100 μm, preferably 10 to 50 μm.
[0008]
The etching apparatus according to the present invention configured as described above is configured so that the cooling gas can flow uniformly on the back surface and the front surface of the substrate tray on which the high dielectric substrate is mounted. Unevenness can be prevented, thereby preventing charge-up.
[0009]
Further, according to the second invention of the present invention, a gas is introduced into the vacuum chamber to form a high-density plasma using microwaves or high-frequency waves, and a pyroelectric high dielectric material substrate is formed on the substrate electrode. In the etching method for mounting and processing the substrate, a receiving surface recess for receiving the substrate to be processed is formed on the surface, and a back surface recess and a back surface are formed on the back surface corresponding to the substrate receiving surface recess on the surface of the substrate tray. It should be processed on the substrate electrode using a substrate tray made of aluminum that forms a contact surface portion that surrounds the recess and contacts the substrate electrode, and that has a plurality of gas flow passages that penetrate from the back surface recess to the substrate receiving surface recess. A substrate is mounted, and a cooling gas is mainly flowed to the surface side of the substrate tray.
[0010]
In the etching method according to the present invention configured as described above, since the cooling gas is mainly flowed to the front side of the substrate tray supporting the substrate at the time of etching the high dielectric substrate, a good cooling efficiency can be obtained. It becomes like this.
[0011]
In the method of the present invention, the leakage amount of the cooling gas supplied to the substrate tray can be set to 7 sccm or less, and the substrate temperature during processing can be maintained at 100 ° C. or less.
[0012]
Further, the substrate placed on the substrate tray can be preferably held with a clamping force that does not give a substantial mechanical stress to the substrate and can release the stress generated during the processing of the substrate.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a main part of an etching apparatus according to an embodiment of the present invention used for etching a high dielectric substrate. In FIG. 1, reference numeral 1 denotes a substrate electrode, which is made of aluminum and disposed in a vacuum chamber (not shown). A substrate tray 2 is placed on the substrate electrode 1. On the surface of the substrate tray 2, a receiving surface recess 2 a that receives the substrate 3 of a pyroelectric high dielectric constant material such as LiNbO ₃ or PZT is formed. The receiving surface recess 2 a has the shape and outer dimensions of the substrate 3. In addition, the surface of the receiving surface recess 2a is made to have high flatness and high smoothness so as to ensure as wide a contact area as possible with the substrate which is an insulator. A back surface recess 2 b is formed on the back surface of the substrate tray 2 at a portion corresponding to the substrate receiving surface recess 2 a, and the back surface recess 2 b is defined by a peripheral contact surface portion 2 c that contacts the substrate electrode 1. The peripheral contact surface portion 2c is formed with high flatness and high surface accuracy. Further, the substrate tray 2 is formed with a plurality of gas flow paths 2d penetrating from the back surface recess 2b to the substrate receiving surface recess 2a. The level difference between the bottom surface of the back surface recess 2b and the peripheral contact surface portion 2c on the back surface side of the substrate tray 2 can be set to 5 to 100 μm, preferably 10 to 50 μm from the viewpoint of obtaining good cooling efficiency with He gas.
[0014]
As shown in the figure, the substrate electrode 1 is provided with a He gas passage 1a, and an outer end of the passage 1a is connected to a He gas supply source 5 via a mass flow meter 4 for flow rate adjustment provided outside the vacuum chamber. ing. The inner end of the passage 1 a communicates with the back surface recess 2 b of the substrate tray 2, whereby the He gas is supplied from the He gas supply source 5 to the surface of the substrate tray 2 through the mass flow meter 4 and the passage 1 a of the substrate electrode 1. However, He gas can also be supplied to the back side.
[0015]
A guide ring 6 for positioning the substrate tray 2 is disposed on the substrate electrode 1. The substrate 3 placed on the substrate tray 2 positioned by the guide ring 6 is supported by the clamp ring 7 at three points in the present embodiment. In this case, the pressing force on the substrate 3 should be set to such an extent that stress that is generated during the processing of the substrate can be released without applying excessive mechanical stress to the substrate. As a constituent material of the clamp ring 7, alumina is most suitable because a high dielectric material such as alumina is generally a metal oxide and has a low etching rate and high etching resistance.
[0016]
The operation of the illustrated apparatus configured as described above will be described.
A substrate placed on a substrate tray prepared in a loading chamber (not shown) is loaded onto the substrate electrode 1 and positioned by the guide ring 6, and the peripheral contact surface portion 2 c on the back side of the substrate tray 2 is moved to the substrate electrode 1. It is held in intimate contact with the surface. He gas is introduced up to 1730 Pa from the He gas supply source 5 through the mass flow meter 4 and the passage 1a of the substrate electrode 1 to the back and front surfaces of the substrate tray 2 to set the substrate tray 2 to a desired cooling temperature. In this case, preferably, He gas introduced from the He gas supply source 5 through the mass flow meter 4 and the passage 1a of the substrate electrode 1 mainly flows along the front side of the substrate tray 2, that is, between the substrate 3 and the substrate tray 2. (Leaks), and stays between the back side of the substrate tray 2, that is, the back side of the substrate tray 2 and the substrate electrode 1, but does not substantially flow (does not leak).
[0017]
FIG. 3 shows the results of measuring the amount of He gas leakage in the substrate tray 2 under the following conditions.
The pressure of He gas introduced from the He gas supply source 5 to the substrate tray 2 through the mass flow meter 4 and the passage 1a of the substrate electrode 1 is set to 1730 Pa, and a LiNbO ₃ substrate is placed on the substrate tray 2 without plasma discharge. It was measured.
[0018]
Next, a mixed gas of Ar and C ₄ F ₈ is introduced into a vacuum chamber (not shown) at 100 sccm, the pressure in the vacuum chamber is set to 0.33 Pa, and the plasma forming induction coil (not shown) is high. Etching was performed by applying 600 W of frequency power and 350 W of high frequency bias power to the substrate electrode 2. As a result, the leakage amount of He gas in the substrate tray 2 is maintained at 7 sccm or less during the etching time of 30 minutes, whereby the temperature of the substrate 3 is maintained at approximately 100 ° C. or less, and temperature rise due to heat inflow during etching is suppressed. It was possible to suppress the thermal stress caused by this, and it was possible to perform etching for 30 minutes without generating a substrate crack.
[0019]
FIG. 2 shows a main part of an etching apparatus according to another embodiment of the present invention. Portions corresponding to those in FIG. 1 are denoted by the same reference numerals.
In the structure shown in FIG. 2, an annular cushioning material 8 having a thickness of 40 μm is pasted instead of providing a stepped portion in the peripheral portion on the back side of the substrate tray 2. Other structures are substantially the same as those of the embodiment shown in FIG.
[0020]
【The invention's effect】
As described above, in the etching apparatus according to the present invention, the receiving surface recess for receiving the substrate to be processed is formed on the surface, and the back surface recess and the back surface recess are surrounded by the back surface corresponding to the substrate receiving surface recess. And a substrate tray made of aluminum and having a plurality of gas flow passages penetrating from the recesses on the back surface to the recesses on the substrate receiving surface. The substrate tray is mounted when mounted on the substrate electrode. The substrate is fixed on the substrate tray by a clamp ring, and the cooling gas is made to flow mainly on the surface side of the substrate tray, so that the substrate is maintained at a substantially uniform temperature during processing, and the temperature unevenness and the charge caused thereby. It is possible to suppress the increase, and it is possible to perform high dielectric processing without causing substrate cracking.
[0021]
Further, in the etching method according to the present invention, a receiving surface recess for receiving a substrate to be processed is formed on the surface, and the back surface recess and the back surface recess are surrounded by a back surface portion corresponding to the substrate receiving surface recess on the surface of the substrate tray. The substrate to be processed is mounted on the substrate electrode using a substrate tray made of aluminum that forms a contact surface portion that contacts the substrate electrode and forms a plurality of gas flow passages that penetrate from the back surface recess to the substrate receiving surface recess. In addition, by flowing the cooling gas mainly along the surface side of the substrate tray, good cooling efficiency for the substrate can be obtained, and as a result, the substrate can be maintained at a substantially uniform temperature during processing, and temperature unevenness and As a result, it is possible to suppress the charge-up, and it is possible to perform high dielectric processing without causing substrate cracking.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a main part of an etching apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing a main part of an etching apparatus according to another embodiment of the present invention.
FIG. 3 is a graph showing a measurement result of a leak amount of He gas in a substrate tray.
[Explanation of symbols]
1: substrate electrode 1a: gas passage 2: substrate tray 2a: receiving surface recess 2b: back surface recess 2c: peripheral contact surface 2d: gas flow path 3: substrate of pyroelectric high dielectric constant material 4: mass flow meter 5: He Gas supply source 6: Guide ring 7: Clamp ring

Claims (5)

Processed on the surface of an etching apparatus that processes a substrate by forming a high-density plasma using a microwave or high frequency by introducing a gas, placing a substrate of a pyroelectric high-dielectric material on the substrate electrode A receiving surface recess for receiving the substrate to be formed is formed, a back surface recess corresponding to the substrate receiving surface recess is formed, and a peripheral contact surface portion that surrounds the back surface recess and contacts the substrate electrode is formed. It has a substrate tray made of aluminum with a plurality of gas flow passages penetrating the surface recess, and when mounted on the substrate electrode, the substrate is fixed on the substrate tray by a clamp ring and cooled mainly to the surface side of the substrate tray An apparatus for etching a pyroelectric high-dielectric, characterized in that a gas is allowed to flow. The pyroelectric high-dielectric etching apparatus according to claim 1, wherein a height from a back surface concave portion to a peripheral contact surface portion of the substrate tray is 5 to 100 μm. In an etching method in which a gas is introduced into a vacuum chamber to form high-density plasma using microwaves or high-frequency waves, a substrate of a pyroelectric high-dielectric material is placed on a substrate electrode, and the substrate is processed. A receiving surface recess for receiving a substrate to be processed is formed on the front surface, a back surface recess corresponding to the substrate receiving surface recess on the surface of the substrate tray, and a contact surface portion surrounding the back surface recess and contacting the substrate electrode. A substrate tray made of aluminum is formed and formed with a plurality of gas flow passages penetrating from the back surface recess to the substrate receiving surface recess, and a substrate to be processed is mounted on the substrate electrode, and cooling gas is mainly used on the surface of the substrate tray. A method of etching a pyroelectric high-dielectric, characterized by flowing along a side. 4. The pyroelectric high-dielectric etching method according to claim 3, wherein the leakage temperature of the cooling gas supplied to the substrate tray is set to 7 sccm or less to maintain the substrate temperature during processing at 100 ° C. or less. . 4. The substrate placed on the substrate tray is held with a clamping force that does not give a substantial mechanical stress to the substrate and can release the stress generated during the processing of the substrate. A method for etching a pyroelectric high-dielectric material described in 1.

Images