JP2012164766A - Etching apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacity coupling type etching apparatus capable of improving in-plane uniformity.SOLUTION: An etching apparatus 1 includes: a vacuum tank 10; a gas supply part 10e which supplies etching gas into the vacuum tank; a flat plate-shaped stage electrode 13 which is disposed in the vacuum tank and has a substrate Sb placed on the upper surface thereof; a flat plate-shaped upper electrode plate 17 which is opposite to the stage electrode 13 via a plasma generation space S; a high frequency power source 20 which supplies high-frequency power to the stage electrode 13; and a magnetic coil group 30 which is constituted of three annular magnetic coils 31 to 33 having diameters different from each other and provided on the upper side of the vacuum tank 10 so that centers of their magnetic coils 31 to 33 become coaxial, and in which the diameter of the outermost magnetic coil 31 is larger than that of the substrate Sb, the diameter of the central magnetic coil 32 is equal to or less than that of the substrate Sb and a magnetic neutral line NL is generated in the plasma generation space S.

Description

  The present invention relates to an etching apparatus.

Conventionally, dry etching has been mainly used for deep processing of a silicon substrate. Since the reaction between silicon and fluorine is spontaneous, fluorine-based gases such as SF ₆ , NF ₃ , COF ₂ , and XeF ₂ are widely used as etching gases.

  Examples of the dry etching apparatus include an apparatus having a capacitively coupled plasma source and an apparatus having an inductively coupled plasma source (see Patent Document 1). This etching apparatus is frequently used because it has the advantages that the discharge pressure is higher than other apparatuses and fluorine radicals that contribute to the improvement of the etching rate can be generated at a high density.

JP 2009-141116 A

  However, in a capacitively coupled etching apparatus, it is difficult to control the position and shape of plasma, and the plasma distribution is dense at the center of the substrate and sparse at the substrate edge except for the center of the substrate. As a result, there is a problem that the uniformity of the etching rate in the radial direction of the substrate is lowered.

  The present invention has been made in view of the above problems, and an object thereof is to provide a capacitively coupled etching apparatus capable of improving in-plane uniformity.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-mentioned problems, the invention described in claim 1 includes a vacuum chamber, a gas supply unit for supplying an etching gas into the vacuum chamber, and a substrate disposed on the upper surface of the vacuum chamber. High-frequency power is supplied to the first electrode on which is mounted, the second electrode facing the first electrode through the plasma generation space, and the first electrode or the second electrode A high-frequency power source and three annular magnetic coils having different diameters are provided above the vacuum chamber so that the centers of the magnetic coils are coaxial, and the diameter of the outermost magnetic coil is The gist of the present invention is that the apparatus further comprises a magnetic field generating means for generating a magnetic neutral line in the plasma generation space, the diameter of the magnetic coil being larger than the diameter of the substrate and being equal to or less than the diameter of the substrate.

  According to the first aspect of the present invention, in the magnetic field generating means for generating the magnetic neutral line, the outermost magnetic coil has a diameter larger than the diameter of the substrate, and the central magnetic coil is equal to or smaller than the diameter of the substrate. Has a diameter. With this configuration, the magnetic neutral line generated in the plasma generation space has a diameter that is approximately the same as or slightly smaller than the diameter of the substrate, so the magnetic neutral line is positioned above the substrate edge except for the central part of the substrate. Will be. For this reason, even in an etching apparatus having a plate-like electrode, the plasma density at the substrate edge can be increased.

The gist of the invention described in claim 2 is that each of the magnetic coils is disposed in contact with the upper wall portion of the vacuum chamber.
According to invention of Claim 2, each magnetic coil is arrange | positioned in contact with the upper wall part of a vacuum chamber. For this reason, since the relative distance between the magnetic coil and the substrate is shortened, the position of the magnetic neutral line can be brought close to the substrate surface and the plasma density near the substrate surface can be increased.

The gist of the invention described in claim 3 is that each of the magnetic coils is arranged so that a central axis thereof is coaxial with a central axis of the substrate.
According to the third aspect of the present invention, the magnetic coil is arranged so that its central axis is coaxial with the central axis of the substrate. For this reason, the bias of the plasma distribution on a board | substrate can be suppressed and the in-plane uniformity of a board | substrate can be improved more.

1 is an overall schematic view of an etching apparatus. FIG. 3 is a schematic diagram of a recess according to the first embodiment. The schematic diagram of the recessed part by the comparative example 1. FIG.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIG.
FIG. 1 is a schematic view of an etching apparatus 1. The etching apparatus 1 is an etching apparatus having a capacitively coupled plasma source, and has a vacuum chamber 10 formed in a substantially bottomed cylindrical shape. The vacuum chamber 10 is made of metal such as aluminum and is grounded, and its upper opening is sealed by the upper wall portion 10a and the like. In addition, the side walls 10b are respectively formed with through-holes 10c for carrying the silicon substrate Sb from the adjacent chamber into the vacuum chamber and for transferring the substrate Sb from the vacuum chamber 10 to another processing chamber. Further, in the vacuum chamber 10, a discharge port 10d for exhausting a fluid such as an etching gas, the atmosphere, and particles in the vacuum chamber is formed through the bottom wall portion. Further, the upper wall portion 10a is provided with a gas supply portion 10e into which the gas supply pipe 11 is inserted, and an etching gas containing a fluorine-based gas such as SF ₆ , NF ₃ , COF ₂ , XeF ₂ is supplied into the vacuum chamber. Is done.

  A substantially cylindrical stage 12 is provided at the lower part of the vacuum chamber 10. The stage 12 has a flat upper surface, and an electrode accommodating portion 12a capable of accommodating the stage electrode 13 inside is provided at the center. The electrode accommodating portion 12a is provided with a fixing portion 14 for supporting and fixing the stage electrode 13 from below.

  A high frequency power supply 20 is electrically connected to the stage electrode 13 via a matching box 21. The matching box 21 includes a matching circuit and a blocking capacitor for matching impedance between the plasma generation region and the transmission path from the high frequency power supply 20 to the substrate Sb.

  A substantially central portion on the upper surface of the stage electrode 13 is a substrate position on which the substrate Sb to be processed is placed. A focus ring 15 made of an insulating material such as quartz is placed on the outer periphery of the substrate position and the upper surface of the stage 12 in order to increase the incident efficiency of ions or the like to the substrate Sb.

  In addition, an electrode support portion 16 is provided on the upper portion of the vacuum chamber 10. The electrode support portion 16 includes a buffer (not shown) that temporarily stores the gas delivered from the gas supply pipe 11 and supports the upper electrode plate 17 on the lower surface thereof. The upper electrode plate 17 functions as an anode, and also functions as a shower plate that ejects the gas stored in the buffer into the plasma generation space S between the upper electrode plate 17 and the stage electrode 13.

  A magnetic coil group 30 is provided outside the vacuum chamber 10 and on the upper wall portion 10a thereof. The magnetic coil group 30 is composed of three magnetic coils 31 to 33. Each of the magnetic coils 31 to 33 is formed in an annular shape, has a different diameter, and is arranged so that its center is coaxial with the central axis of the substrate Sb. That is, the magnetic coils 31 to 33 are arranged concentrically in a plan view as viewed from the upper wall portion 10a side. The magnetic coil group 30 is placed on the upper wall portion 10a of the vacuum chamber 10 so that the relative distance to the substrate Sb is as short as possible.

  The outermost first magnetic coil 31 has a diameter larger than the diameter of the substrate Sb, and the central second magnetic coil 32 has a diameter equal to or smaller than the diameter of the substrate Sb. The innermost third magnetic coil 33 has a diameter smaller than the diameter of the substrate Sb.

  The first magnetic coil 31 and the third magnetic coil 33 are supplied with current in the same direction, and the central second magnetic coil 32 is supplied with current in the opposite direction to the other magnetic coils 31 and 33. As a result, a so-called magnetic neutral line NL in which the magnetic field is zero is continuously generated in the plasma generation space S in an annular shape. At this time, by setting the first magnetic coil 31 and the second magnetic coil 32 to the above-described diameter, the magnetic neutral line NL is near the lower part of the second magnetic coil 32 and above the edge part of the substrate Sb. It is generated at the position. The edge portion refers to a portion excluding the central portion when a circular region having a diameter that is half the diameter of the substrate Sb is defined as the central portion.

  When high frequency power is applied to the stage electrode 13, plasma is generated in the plasma generation space. Electrons existing in the vicinity of the magnetic neutral line NL are applied with a high-frequency electric field, and repeat acceleration motion in a magnetic field in which the electron cyclone resonance conditions are satisfied to finally obtain energy. That is, since the high frequency power can be efficiently absorbed in the vicinity of the magnetic neutral line NL, the plasma density can be increased. In particular, in the vicinity of the magnetic neutral line NL, the plasma density increases, and a large amount of fluorine radicals that contribute to the etching of the silicon substrate are generated, so that the etching rate at the substrate edge can be improved. Therefore, when plasma is generated only with parallel plate type electrodes, the plasma density at the center of the substrate naturally increases and the plasma density at the substrate edge decreases, but by generating the magnetic neutral line NL, the substrate edge portion is generated. The plasma density can be increased to suppress the bias of the plasma distribution.

  When etching is performed, the substrate Sb is transferred from the adjacent chamber into the vacuum chamber through the transfer port 10c and placed on the substrate position of the stage electrode 13. Further, the atmosphere in the vacuum chamber is discharged from the discharge port 10d, and an etching gas having a predetermined flow rate is supplied from the gas supply pipe 11 into the vacuum chamber. At this time, the inside of the vacuum chamber has a relatively high pressure range of 10 to 100 Pa by adjusting the flow rate of the supplied etching gas and the exhaust amount from the discharge port 10d.

  After supplying the etching gas, a current is supplied to the magnetic coil group 30. That is, a current in the same direction (for example, the back side of the drawing) is supplied to the first magnetic coil 31 and the third magnetic coil 33, and a current in the direction opposite to the other magnetic coils 31, 33 is supplied to the second magnetic coil 32 ( For example, the front side of the sheet) is supplied. Thereby, the magnetic neutral line NL is generated at the position described above in the plasma generation space S. Further, a high frequency voltage is applied to the stage electrode 13, and the etching gas is ionized by the discharge between the stage electrode 13 and the upper electrode plate 17, and plasma is generated in the plasma generation space S. Since the electrons in the generated plasma gather at the magnetic neutral line NL along the magnetic field gradient, the plasma is efficiently generated near the magnetic neutral line NL.

At this time, since the magnetic coil group 30 is placed on the upper wall portion 10a so that the relative distance to the substrate Sb is the shortest, the magnetic coil group 30 is disposed at the lowest position where the magnetic neutral line NL can be generated in the vertical direction. Is done. Accordingly, since the magnetic neutral line NL is formed in the vicinity of the substrate surface, the plasma density in the vicinity of the substrate surface is increased. The radical species and positive ions in the plasma are attracted to the substrate Sb by the bias voltage applied to the substrate Sb. Fluorine radicals having no directivity advance highly isotropic etching, react with silicon to become SiFn, and desorb from the substrate surface. The positive ions are etched in the thickness direction of the substrate Sb. As a result, a recess is formed at a predetermined position of the substrate Sb. At this time, since the plasma density in the vicinity of the substrate surface is increased, the etching rate can be increased. Moreover, since the magnetic neutral line NL is formed above the edge portion of the substrate Sb, the plasma density at the substrate edge portion does not become extremely smaller than the plasma density at the center portion of the substrate, and the etching rate is uniform in the plane. Can be improved.

  In the etching apparatus 1, it is known that the position of the magnetic neutral line NL is changed by changing the current magnitude of each of the magnetic coils 31 to 33, but the pressure in the vacuum chamber is 10 as described above. In the case of a relatively high pressure of ˜100 Pa, it is difficult to adjust the plasma distribution. However, in the etching apparatus 1, the plasma density near the substrate edge and near the surface can be increased by adjusting the position of the magnetic coil group 30. Further, by increasing the plasma density, the sheath generated in the vicinity of the substrate surface is thinned, and processing with high anisotropy can be performed by setting the direction of ions and the like incident on the substrate Sb to be nearly perpendicular.

According to the above embodiment, the following effects can be obtained.
(1) The etching apparatus 1 of the above embodiment is a parallel plate type etching apparatus, and includes a flat stage electrode 13 and a flat upper electrode plate 17 that faces the stage electrode 13 through the plasma generation space S. And have. Further, a magnetic coil group 30 for generating a magnetic neutral line NL in the vacuum chamber is provided above the vacuum chamber 10. The three magnetic coils 31 to 33 constituting the magnetic coil group 30 have an annular shape, have different diameters, and are arranged so that their centers are coaxial. The diameter of the outermost first magnetic coil 31 is larger than the diameter of the substrate Sb, and the diameter of the second magnetic coil 32 at the center is equal to or smaller than the diameter of the substrate Sb. With this configuration, the magnetic neutral line NL generated in the plasma generation space has a diameter that is substantially the same as or slightly smaller than the diameter of the substrate, so the magnetic neutral line NL is above the substrate edge except for the central portion of the substrate. Will be located. For this reason, also in the capacitively coupled etching apparatus 1 having a flat electrode, the plasma density at the substrate edge portion can be increased.

  (2) In the embodiment described above, the magnetic coils 31 to 33 are arranged in contact with the upper wall portion 10 a of the vacuum chamber 10. For this reason, since the relative distance between each of the magnetic coils 31 to 33 and the substrate Sb is shortened, the position of the magnetic neutral line NL can be brought close to the substrate surface and the plasma density near the substrate surface can be increased.

  (3) In the above embodiment, the magnetic coils 31 to 33 are arranged so that the central axis thereof is coaxial with the central axis of the substrate Sb. For this reason, the bias of the plasma distribution on the substrate can be suppressed, and the in-plane uniformity of the substrate can be further improved.

[Example 1]
A mask having an opening having a diameter of 5 to 10 μm was applied to an 8-inch silicon substrate having a thickness of 725 μm, and then etching was performed using the etching apparatus 1 under the following conditions.

Etching gas: mixed gas of sulfur hexafluoride gas, oxygen gas, and hydrogen bromide gas Flow rate: 75 sccm, 80 sccm, 15 sccm (SF ₆ , O ₂ , HBr)
Frequency of high frequency power: 60MHz
Output value: 3600 W / cm ²
Etching pressure: 360 mTorr
And the recessed part of Example 1 was obtained by performing etching for 8 minutes on the said etching conditions (refer FIG. 2). In the case where a predetermined etching shape (for example, the recess H) is formed on the substrate Sb by reactive ion etching, a mask M having a predetermined opening is formed on the substrate Sb prior to the reactive etching. Then, the positive ions and radical species enter the substrate Sb from the opening, whereby the substrate Sb is etched.

  As shown in FIG. 2, when the recess H is formed using the etching apparatus 1, the plasma density in the vicinity of the substrate is increased, so that etching easily proceeds along the normal direction of the opening Ma. Therefore, an etching shape with high anisotropy can be obtained with an inner diameter φ2 close to the inner diameter φ1 of the opening Ma. At this time, the depth D1 etching depth along the normal direction of the recess H is 80 μm at the center of the substrate and 82 μm at the edge near the outer edge of the substrate Sb. The etching rate is 10 μm / min at the center of the substrate and 10.25 μm / min at the substrate edge. The uniformity of the etching rate within the substrate surface was ± 1.23%.

[Comparative Example 1]
Etching was performed under the same conditions as in Example 1 using an apparatus in which the magnetic coil group 30 of the etching apparatus 1 of the above embodiment was omitted.

  As shown in FIG. 3, when the concave portion H is formed using the etching apparatus of the comparative example, the etching is less likely to proceed along the normal direction of the opening Ma as compared with the first embodiment, and the inner diameter φ3 is larger than that of the first embodiment. Is large (φ3> φ2), and an etching shape with high isotropy can be obtained. At this time, the depth D2 along the normal direction of the recess H is 70 μm at the center of the substrate and 75 μm at the edge near the outer edge of the substrate Sb. The etching rate is 8.75 μm / min at the center of the substrate and 9.4 μm / min at the substrate edge. The uniformity of the etching rate within the substrate surface was ± 3.44%. That is, compared with Example 1, the difference between the central portion of the substrate and the edge portion was large, and the in-plane uniformity was lower than that of Example 1.

In addition, you may change this embodiment as follows.
In the above embodiment, the magnetic coil group 30 is disposed so as to be in contact with the upper wall portion 10a of the vacuum chamber 10. However, it may be separated and may be disposed at a position close to the substrate Sb.

  In the above embodiment, the substrate to be processed is the silicon substrate Sb, but a substrate made of another material such as a quartz substrate may be the target to be processed.

  DESCRIPTION OF SYMBOLS 1 ... Etching apparatus, 10 ... Vacuum chamber, 10a ... Upper wall part, 10e ... Gas supply part, 13 ... Stage electrode as 1st electrode, 17 ... Upper electrode plate as 2nd electrode, 20 ... High frequency power supply, 30 ... Magnetic coil groups as magnetic field generating means, 31 to 33, magnetic coils, NL, magnetic neutral wire, S, plasma generation space, Sb, substrate.

Claims (3)

A vacuum chamber;
A gas supply unit for supplying an etching gas into the vacuum chamber;
A flat plate-like first electrode which is disposed in the vacuum chamber and on which the substrate is placed;
A flat plate-like second electrode facing the first electrode via a plasma generation space;
A high frequency power source for supplying high frequency power to the first electrode or the second electrode;
It is composed of three annular magnetic coils having different diameters, and is provided above the vacuum chamber so that the centers of the magnetic coils are coaxial, and the diameter of the outermost magnetic coil is larger than the diameter of the substrate. An etching apparatus comprising: a magnetic field generating means for generating a magnetic neutral line in the plasma generation space, wherein the diameter of the magnetic coil at the center is equal to or smaller than the diameter of the substrate.   The etching apparatus according to claim 1, wherein each of the magnetic coils is disposed in contact with an upper wall portion of the vacuum chamber.   3. The etching apparatus according to claim 1, wherein each of the magnetic coils is arranged so that a central axis thereof is coaxial with a central axis of the substrate.

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