JP2013048143A - Plasma processing apparatus and plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus equipped with means for adjusting uniformity in sputter etching, with no complex configuration required.SOLUTION: Permanent magnets 8a and 8b are installed such that different poles face each other at an outer peripheral part of a pair of electrodes 5a and 5b facing each other. A magnetron magnetic field (semi-cylindrical magnetic field) is formed at a portion extending from around the front area of the outer periphery of each electrode to an electrode surface being close to the center, in such a manner that a counter magnetic field is formed in the direction vertical to an electrode surface between outer peripheral parts of the pair of electrodes. Each electrode is supplied with plasma power, and argon or the like is supplied through a guiding inlet 2, and then plasma etching is performed on a substrate to be processed 13 placed on one electrode 5b. Magnetic field adjusting means 12a and 12b are provided to the rear surface of each electrode, to adjust magnetic field of plasma space, for adjusting uniformity of etching.

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method. More specifically, the present invention relates to a processing target in which a pair of electrodes are disposed opposite to each other with a predetermined space therebetween, plasma is generated in the counter electrode space, and the processing target is disposed on at least one electrode. The present invention relates to a plasma processing apparatus and a plasma processing method in which a substrate surface is processed with plasma.

  In semiconductor processes, excellent anisotropic etching characteristics can be obtained by generating plasma in a vacuum chamber and processing the substrate surface instead of isotropic wet etching using an etchant as processing becomes finer. Dry etching techniques such as reactive ion etching are widely used. Parallel plate type, ECR (electron cyclotron resonance) type, helicon wave type, etc. have been developed as dry etching equipment, but a magnetron type etching equipment is known as being able to achieve high plasma density with a relatively simple equipment. (For example, see Patent Documents 1 and 2).

  In Patent Document 1, plasma processing is performed in which a permanent magnet installed on a chamber is rotated, a conductive ring is disposed so as to surround an outer periphery of a wafer (substrate to be processed), and a susceptor (wafer mounting table) is used as an anode. An apparatus is disclosed. Patent Document 2 discloses a plasma in which a circumferential groove is provided in the outer periphery of a reaction chamber, a permanent magnet is disposed in the circumferential groove, and this is circulated to supply RF power to a substrate mounting electrode serving as an anode. A processing device is disclosed.

JP 05-029269 A JP 05-047715 A

In the conventional plasma processing apparatus described above, since the permanent magnet has to be rotated, the apparatus may be complicated. Also, in the method of rotating the permanent magnet, the operating speed of the permanent magnet that forms the magnetic field is orders of magnitude slower than the frequency of the power source supplied to the electrodes, resulting in non-uniform plasma density on the substrate surface. There is a concern that micro arcs may be generated due to the charge-up of the insulating resist applied to the substrate, and the processing shape may be poor during etching.
An object of the present invention is to solve the above-mentioned problems of the prior art, and it is possible to realize high-density and highly uniform plasma in a static magnetic field structure without rotating a permanent magnet with respect to a substrate to be processed. Is to do so.

In order to achieve the above object, according to the present invention, a pair of electrodes are arranged to face each other at a predetermined interval, and an electrode surface closer to the center from the front vicinity of the outer periphery of each electrode along the outer periphery of each electrode. Magnetron magnetic field (semi-cylindrical magnetic field) is installed opposite to each other so that different poles face each other so that a vertical opposing magnetic field can be formed on the electrode surface between the outer peripheries of the pair of electrodes. There is provided a plasma processing apparatus characterized in that power is supplied to the pair of electrodes to generate plasma in a counter electrode space, and processing is performed on the surface of a substrate to be processed placed on at least one of the electrodes. .
Preferably, a magnetic field adjusting means is provided inside the permanent magnet on the back surface of each electrode. More preferably, the magnetic field adjusting means is a permanent magnet, a magnetic material, or a combination thereof. Preferably, a substrate height adjusting means for adjusting the surface height of the substrate to be processed is installed between the substrate to be processed and the electrode holding the substrate.

  In order to achieve the above object, according to the present invention, a pair of electrodes are arranged opposite to each other at a predetermined interval, and along the outer periphery of each of the electrodes, the vicinity of the center from the front vicinity of the outer periphery of each electrode. A magnetron magnetic field is formed on a portion reaching the electrode surface, and a counter magnetic field perpendicular to the electrode surface can be formed between the outer peripheral portions of the pair of electrodes, and power is supplied to the pair of electrodes to be disposed on at least one of the electrodes. A plasma processing method for processing a surface of a substrate to be processed, wherein either one or both of an inert gas and a reactive gas is supplied between the pair of electrodes for processing. A processing method is provided.

[Action]
According to the present invention, a pair of electrodes are arranged opposite to each other in a vacuum processing chamber with a predetermined space therebetween, and permanent magnets are arranged along the outer periphery of each of the electrodes so that different polarities face each other. As a result, a semi-cylindrical magnetron magnetic field is formed in a portion from the front vicinity of the electrode outer peripheral portion to the electrode surface closer to the center. Here, when a sputtering gas such as argon gas is supplied to the vacuum processing chamber and DC, pulse, or high frequency power is supplied from the power source to each of the opposed electrodes, the vicinity of the front surface of the outer periphery of each electrode reaches the electrode surface closer to the center. A plasma (hereinafter referred to as magnetron plasma) is formed in the portion.

  In addition, a magnetic field perpendicular to the electrode surface (opposing magnetic field) is formed between the permanent magnets facing different polarities. Therefore, electrons between the counter electrodes travel toward one electrode while being entangled in the magnetic flux. And when it reaches the vicinity of the electrode, it is reflected by the cathode sheath on the electrode surface and heads toward the other electrode while being entangled with the magnetic flux between the opposing electrodes again. When reaching the vicinity of the electrode, it is reflected again by the cathode sheath on the electrode surface, and by repeating this, electrons reciprocate between the electrodes.

Electrons reciprocating between the counter electrodes generate plasma between the counter electrodes by colliding with argon gas or etching gas introduced into the vacuum chamber, and this plasma is counter electrode by a permanent magnet installed on the outer periphery of the counter electrode. A high density plasma (hereinafter referred to as counter plasma) is formed in a portion constrained by the space and extending from the center between the counter electrodes to the outer periphery.
This counter plasma and the previous magnetron plasma are combined to obtain a high-density plasma in the counter electrode space. Then, by appropriately setting the balance between the opposed plasma and the magnetron plasma, the plasma density distribution can be made uniform, and the plasma treatment can be made uniform.

  However, a desired plasma density distribution may not be obtained with only the permanent magnets arranged opposite to the outer periphery of the electrode. In addition, the plasma processing apparatus according to the present invention performs surface treatment of not only a silicon substrate generally used in the semiconductor field but also a metal material including an alloy, an oxide material such as glass, and an organic material such as plastic. There is also. In this case, since the magnetic properties of the base material and the material coated on the base material affect the magnetic field structure formed between the opposing electrodes and on each electrode surface, the balance between the plasma density of the magnetron plasma and the counter plasma is balanced. May collapse. For these reasons, the uniformity of the plasma surface treatment on the entire surface of the substrate may change.

In order to cope with this, according to the present invention, magnetic field adjusting means made of, for example, a permanent magnet is provided on the back surface of the electrode inside the opposed permanent magnet. By providing a magnetic field adjustment means made of a permanent magnet, a counter magnetic field is formed between the magnetic field adjustment means and a plasma magnetic field is formed around the magnetic field adjustment means, thereby making it possible to change the original magnetic field distribution, The distribution of plasma density can be adjusted.
Further, when the surface height of the substrate to be processed is changed, the magnetic field state on the surface of the substrate to be processed can be changed. By this means, it is possible to adjust the uniformity of plasma processing.
In addition, transition metals may be used for materials such as MEMS (Micro Electro Mechanical Systems), and etching may be difficult with conventional plasma processing apparatuses that perform etching based on chemical reactions. According to the possible device of the present invention, a transition metal material or the like generally called a difficult-to-etch material can be easily etched.

  According to the present invention, high-density plasma can be realized in a stationary magnetic field structure without moving a permanent magnet that forms a magnetic field with respect to a substrate. Further, uniform plasma is formed on the entire surface of the substrate to be processed by adjusting the thickness of the height adjusting plate inserted between the substrate to be processed and the lower electrode or by adjusting the magnetic field intensity by the magnetic field adjusting means installed on the back surface of the electrode. be able to.

It is sectional drawing which shows one embodiment of this invention. It is sectional drawing of the AA line of FIG. It is sectional drawing of the BB line of FIG. It is a graph for demonstrating the effect | action of this invention. It is sectional drawing which shows the magnetic field adjustment means used for the Example. It is a graph for demonstrating the effect | action of this invention.

Next, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a longitudinal sectional view of a plasma processing apparatus according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view taken along line AA in FIG. 1, and FIG. 3 is a sectional view taken along line BB in FIG. FIG. In these drawings, the same parts are denoted by the same reference numerals.
As shown in FIGS. 1 and 2, the vacuum chamber 1 is constituted by a metal tank wall 4 made of aluminum or the like, a pair of electrodes, an upper electrode 5 a and a lower electrode 5 b. The upper electrode 5a and the lower electrode 5b have a quadrangular planar shape, and both form a parallel plate type electrode. That is, the counter electrode space is formed in the vacuum chamber 1 by the electrode pair. The upper electrode 5a and the lower electrode 5b are connected to a power source and supplied with power such as DC, pulse, high frequency (RF), DC + RF, and the like. The tank wall 4 is grounded. The tank wall 4 is provided with an introduction port 2 and an exhaust port 3. An inert gas such as argon gas, a reactive gas such as oxygen, nitrogen or carbon fluoride, or a mixed gas of an inert gas and a reactive gas is supplied from the introduction port 2. The exhaust port is connected to a turbo molecular pump and evacuated.

  The upper electrode 5a and the lower electrode 5b are constituted by flat plate electrode plates 6a and 6b made of, for example, copper, and electrode plate supports 7a and 7b made of, for example, aluminum for supporting the electrode plates 6a and 6b at the peripheral portions thereof. Composed. The electrode plate supports 7a and 7b have a frame shape, in which grooves for accommodating permanent magnets are formed along the outer periphery of each side so that the opposite poles face each other. Permanent magnets 8a and 8b are accommodated. A part of the lines of magnetic force emitted from the permanent magnets 8a and 8b extend in the vertical direction of FIGS. 1 and 2 and enter the opposing permanent magnet, and the other part of the magnetic lines return to the other magnetic pole side. A magnetic field that restrains the magnetron plasma is formed by the magnetic field lines formed between the magnetic poles. Yoke plates 10a and 10b are installed on the back surfaces of the permanent magnets 8a and 8b, respectively, whereby the permanent magnets installed along each side are magnetically coupled to each other.

  The electrode plates 6a and 6b are provided with cooling water passages having a zigzag structure inside in order to efficiently discharge the heat applied to the electrodes during plasma processing to the outside, and this includes a cooling water tube 9a made of synthetic resin. , 9b are connected and cooling water is allowed to flow. Also, L-shaped insulating frames 11a and 11b made of heat-resistant resin are inserted between the electrodes 5a and 5b and the tank wall 4, and the electrodes and the tank wall 4 are insulated and separated.

A substrate 13 to be processed is placed on the electrode plate 6b of the lower electrode 5b, and is fixed by a substrate fixing jig 15 made of a conductive material having a low sputtering rate such as a titanium alloy material. A height adjusting plate 14 for adjusting the surface height of the substrate to be processed 13 is inserted between the substrate to be processed 13 and the electrode plate 6b as necessary. The height adjusting plate 14 is formed of a material having high thermal conductivity such as aluminum or titanium. The substrate to be processed 13, or the substrate to be processed 13 and the height adjustment plate 14 are fixed in close contact with the electrode plate 6 b by the substrate fixing jig 15, and are effectively cooled. In addition, the electrode plate support 7b of the lower electrode 5b has a bolt attached to the electrode plate 6b in order to prevent the surface from being sputtered during plasma processing and the permanent magnet 8b installed therein due to temperature rise from being deteriorated by heat. An electrode surface member 17b made of a conductive material (for example, titanium) having a low sputtering rate is installed on the L-shaped fitting 16 and covered with a fixed L-shaped fitting 16 made of a thermally conductive material such as a copper plate. .
Here, the surface height of the electrode plate 6b of the lower electrode 5b is preferably lower than the surface height of the front surface side of the permanent magnet 8b. By doing so, the strength of the magnetron magnetic field formed on the substrate to be processed 13 can be effectively adjusted by the thickness of the height adjusting plate 14.

  Further, the surface of the upper electrode 5a on the surface of the electrode plate 6a is sputtered during plasma processing, and the electrode surface material is prevented from adhering to the surface of the substrate 13 to be processed placed on the lower electrode, so that the sputtering rate is low. The electrode surface member 17a made of a conductive material is installed. The electrode surface member 17a is made of, for example, a carbon plate, and is bonded to the electrode plate 6a with a heat conductive adhesive such as indium. The electrode surface member 17a also suppresses the electrode material on the electrode plate support 7a holding the permanent magnet 8a from being sputtered during the plasma processing so that the permanent magnet 8a is prevented from being deteriorated by heat. It has become.

  Magnetic field adjusting means 12a, 12b for adjusting the plasma processing uniformity is installed between the electrode plates 6a, 6b and the yoke plates 10a, 10b as required. The magnetic field adjusting means 12a, 12b is constituted by a permanent magnet, a magnetic material, or a combination thereof, and when including the permanent magnet, the polarity thereof is arranged to match the polarity of the permanent magnet 8a, 8b in the electrode. The magnetic field adjusting means 12a and 12b are magnetically coupled to the permanent magnets 8a and 8b by being connected to the yoke plates 10a and 10b.

  A power source is connected between the tank wall 4 and the upper electrode 5a and the lower electrode 5b to supply electric power for forming plasma to the plasma processing apparatus. As the power source, a DC power source, a pulse power source, an RF power source, a power source in which RF is superimposed on DC, or the like is used. The upper electrode 5a and the lower electrode 5b may be fed by the same power source, but may be fed by separate power sources.

Although the plasma processing apparatus described in the above embodiment performs sputtering (etching) on a substrate to be processed, it may be formed on a substrate to be processed. When film formation is performed, a target is placed on the electrode on the side opposite to the substrate to be processed. Further, in the above embodiment, the substrate to be processed is placed only on one electrode, but the substrate to be processed is placed on both electrodes, and sputtering (etching) is simultaneously performed on the two substrates. You may make it perform. In addition, the processing apparatus according to the embodiment has a rectangular parallelepiped shape, but may be a cylindrical shape or an elliptical cylindrical shape instead. In the above embodiment, the magnetic field adjustment means is provided on the back side of both electrodes. However, the magnetic field adjustment means may be provided only on the side on which the substrate to be processed is placed. Furthermore, the magnetic field adjusting means only needs to change the magnetic field formed by the permanent magnet, and can be installed outside the permanent magnet or a plurality of them.
Examples of the etching process will be described below.

When the height adjusting plate 14 is not used and when the thickness is 5 mm and 10 mm (each 92 mm square aluminum plate), sputter etching is performed using a silicon substrate as a substrate and argon as a process gas. The action / effect of the thickness adjusting plate 14 was confirmed.
Using silicon cut to 90 mm square as a test substrate, first clean the silicon substrate in the order of acetone, ethanol, and pure water for 5 minutes using an ultrasonic cleaner made by Honda Electronics Co., Ltd. Used to bake to completely remove moisture. Next, using a spin coater manufactured by Mikasa Co., Ltd., a resist (OFPR (trade name) manufactured by Tokyo Ohka Kogyo Co., Ltd.) is coated on the entire surface of the silicon substrate about 2 μm, and the silicon substrate is prebaked at 105 ° C. for 3 minutes with a constant temperature dryer to solidify the resist Subsequently, the silicon substrate was exposed using a mask aligner manufactured by Union Optical Co., Ltd., and a lattice pattern in which 0.1 mm wide lines were arranged at 1.1 mm intervals and the line portions vertically intersected vertically and horizontally was patterned on the entire surface of the silicon substrate.

Next, it developed using the developing solution (NMD-3 (brand name) by Tokyo Ohka Kogyo Co., Ltd.), and post-baked at 90 degreeC for 5 minute (s) with the constant temperature dryer. Next, in the new facing target sputtering apparatus manufactured by F. Thi es Corporation on a silicon substrate subjected to patterning, a SiO _x film of about 1μm thick is deposited on the entire substrate surface by reactive sputtering using a silicon target, Thereafter, the resist on the silicon substrate was removed with acetone using an ultrasonic cleaner to prepare a test substrate using the SiO _x film as a mask by lift-off.

This test substrate is placed on the lower electrode of the plasma processing apparatus according to the present invention, and argon gas having a purity of 99.99995% or more is introduced into the vacuum chamber 1 so that the degree of vacuum in the vacuum chamber 1 is 0.3 Pa. The flow rate was adjusted. ENI pulse power supply RPG50 (trade name) is connected to a pair of electrodes facing each other, the frequency is 100 kHz, the pulse width is 1056 ns, 300 W is input in accordance with the upper electrode 5 a and the lower electrode 5 b, and the sputter etching time is on the test substrate. In order not to etch all the 1 μm-thick SiO _x mask formed in the above, it was set for 6 minutes. After etching, the test substrate was immersed in buffered hydrofluoric acid to remove the remaining SiO _x mask, and the test substrate was washed with pure water.
Thereafter, the etching depth was measured using a stylus type step gauge manufactured by AMBIOS. The measurement positions are 9 points in total (9 points on the center line that bisects the top and bottom in FIG. 3) with the center of the substrate as the origin and a width of 40mm to the origin parallel to the cutting surface of the test substrate at 10mm intervals. .

The measurement results are shown in FIG. Here, when the thickness of the height adjustment plate 14 is 5 mm, the surface height of the counter electrode side of the permanent magnet 8b and the height of the substrate surface are approximately the same.
When the thickness of the height adjustment plate is 0mm (when the height adjustment plate is not used), the counter electrode surface side height of the permanent magnet 8b is higher than the test substrate surface height. Since the magnetron plasma to be applied acts relatively stronger than the counter plasma formed in the vicinity of the center of the test substrate, the etching rate around the outer periphery of the test substrate increases. As can be seen from FIG. The etching depth is higher than the central portion. When the distribution characteristic with respect to the etching depth average value at 9 measurement positions is calculated as “(each etching depth−average value at 9 points) / average value at 9 points × 100”, it is −31.7% to 50.8%.

When the thickness of the height adjustment plate is 10 mm, the surface height of the permanent magnet 8b facing the counter electrode surface is about 5 mm higher than the test substrate surface. Becomes stronger. As a result, the etching depth around the outer periphery of the test substrate decreases, and the etching depth increases around ± 20 mm from the center. Further, since the counter plasma is only relatively strong, the etching depth in the vicinity of the center of the test substrate tends to decrease, and the etching distribution characteristic at this time is −47.9% to 30.3%.
When the thickness of the height adjusting plate is 5 mm, the etching distribution is -17.6% to 27.9%, which is the best value among the three conditions of the height adjusting plate due to the intermediate effect of 0 mm and 10 mm. From the above results, it was confirmed that the etching distribution characteristic of the surface of the substrate to be processed placed on the lower electrode can be adjusted by the thickness of the height adjusting plate.

The influence on the etching distribution due to the change in magnetic field strength when the magnetic field adjusting means 12a and 12b are adjusted using the test substrate manufactured in the same manner as in the case of Example 1 using the plasma processing apparatus used in Example 1. confirmed. An aluminum plate having a thickness of 5 mm was inserted under the test substrate as the height adjustment plate 14. FIG. 5 shows the adjustment state of the magnetic field adjusting means 12a and 12b installed at the center of the back surface of the electrode plate, and FIG. 6 shows the etching measurement results in each case.
When the magnetic field structure A does not use magnetic field adjustment means, the magnetic field structure B is a stack of two auxiliary magnets (permanent magnets) 25 mm long × 10 mm wide × 10 mm high, and the magnetic field structure C includes two auxiliary magnets. The magnetic field structure D, which is a stack of one yoke block (iron plate) of the same size, is a stack of three auxiliary magnets. These auxiliary magnets and yoke blocks are fixed to the yoke plates 10a and 10b by magnetic force.

In the case of the magnetic field structure A, the measurement data is the same as in the case where the thickness of the adjustment plate of Example 1 is 5 mm. In the magnetic field structure B, the etching depth near the center of the test substrate tends to increase as the counter plasma intensity increases compared to the magnetic field structure A, and the etching distribution at this time ranges from -16.0% to 17.1% And the magnetic field structure A is improved.
In the magnetic field structure C, the addition of the yoke block increases the counter plasma intensity and increases the etching depth near the center of the test substrate. In addition, since the magnetron plasma intensity is relatively lowered, the etching depth in the vicinity of the outer peripheral portion of the test substrate surface tends to be lowered, and the etching distribution in the magnetic field structure C is −9.3% to 8.8%. In the magnetic field structure D, the opposing plasma intensity is further increased and the magnetron plasma intensity is decreased as compared with the magnetic field structure C, and the etching distribution of the magnetic field structure D is −31.1% to 26.5%. From the above results, it was confirmed that the etching distribution characteristics on the surface of the substrate to be processed can be adjusted by adjusting the magnetic field strength by the magnetic field adjusting means installed near the center of the back surface of the electrode plate 6b.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Inlet port 3 Exhaust port 4 Tank wall 5a Upper electrode 5b Lower electrode 6a, 6b Electrode plate 7a, 7b Electrode plate support 8a, 8b Permanent magnet 9a, 9b Cooling water tube 10a, 10b York plate 11a, 11b Insulating frames 12a and 12b Magnetic field adjusting means 13 Substrate to be processed 14 Height adjusting plate 15 Substrate fixture 16 L-shaped bracket 17a and 17b Electrode surface member

Claims (12)

A pair of electrodes are arranged opposite to each other at a predetermined interval, and a magnetron magnetic field (semi-cylindrical magnetic field) is formed along the outer circumference of each electrode from the front vicinity of the outer circumference of each electrode to the electrode surface closer to the center. Permanent magnets are installed facing each other so that different polarities face each other so that a vertical opposing magnetic field can be formed on the electrode surface between the outer peripheral portions of the pair of electrodes, and power is supplied to the pair of electrodes, A plasma processing apparatus, characterized in that plasma is generated in a space and processing is performed on a surface of a substrate to be processed that is placed on at least one electrode. The plasma processing apparatus according to claim 1, further comprising a magnetic field adjusting unit that changes a magnetic field formed by the permanent magnet. The plasma processing apparatus according to claim 2, wherein the magnetic field adjusting unit is a permanent magnet, a magnetic material, or a combination thereof. 4. The plasma processing according to claim 1, wherein a substrate height adjusting means for adjusting a surface height of the substrate to be processed is installed between the substrate to be processed and the electrode. apparatus. 5. The plasma processing apparatus according to claim 1, wherein the back surface of the permanent magnet, or the back surface of the permanent magnet and the back surface of the magnetic field adjusting means are in contact with a yoke plate. 6. The height of the surface on which the substrate to be processed of the electrode on which the substrate to be processed is mounted is lower than the height on the front side of the permanent magnet held by the electrode. The plasma processing apparatus according to any one of the above. A pair of electrodes are arranged opposite to each other at a predetermined interval, and a magnetron magnetic field is applied along the outer periphery of each of the electrodes from the front of the outer periphery of each electrode to the electrode surface closer to the center. A plasma processing method for forming a counter magnetic field perpendicular to the electrode surface between the parts, supplying power to the pair of electrodes, and processing the surface of the substrate to be processed disposed on at least one of the electrodes. A plasma processing method comprising performing processing by supplying either one or both of an inert gas and a reactive gas between the pair of electrodes. The plasma processing method according to claim 7, wherein the processing is performed by adjusting the intensity of a magnetron magnetic field or a counter magnetic field formed on the electrode, or a balance between these two magnetic fields. 9. The plasma processing method according to claim 7, wherein power is supplied to each electrode from a separate power source. The plasma processing method according to claim 7, wherein the power supplied to each electrode is any one of DC, RF, pulse, and DC + RF. The plasma processing method according to claim 7, wherein the surface of the substrate to be processed is processed by sputter etching. The target substrate is placed on one electrode, the target is placed on the other electrode, and the target is sputtered to form a thin film on the surface of the target substrate. Plasma processing method.

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