JP3655966B2 - Plasma generator - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an etching apparatus that uses plasma to etch semiconductors, electronic components, and other substances on a substrate, and a plasma generation apparatus used in a plasma CVD apparatus that deposits a film on the substrate.
[0002]
[Prior art]
Conventionally, for example, in an etching apparatus or a plasma CVD apparatus, a magnetron type using a magnet, an ECR discharge type using an electron cyclotron resonance, and a helicon type plasma generator using a helicon wave have been used.
More recently, a magnetic field generating means by three solenoid coils for forming a magnetic neutral line in the vacuum chamber, and an electric field is formed along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means. A plasma generator comprising an electric field generating means for generating a discharge plasma in the magnetic neutral line has been proposed (see Japanese Laid-Open Patent Publication No. 7-90632) and applied to an etching apparatus (Japanese Laid-open Patent Publication No. 7-263192). See the official gazette).
[0003]
An example in which a permanent magnet is used instead of a coil as a magnetic field generating means for forming a magnetic neutral line has been proposed (see Japanese Patent Application No. 7-217965).
The present invention relates to an improvement in a magnetic neutral discharge plasma apparatus using this permanent magnet.
[0004]
That is, the plasma generator proposed in Japanese Patent Application No. 7-217965 is a discharge plasma apparatus in which the upper surface A1 generates plasma in a dielectric vacuum chamber A as shown in FIG. 4 of the accompanying drawings. In order to form an annular magnetic neutral line that is continuously present in the vacuum chamber A and has a magnetic field of zero, a donut-shaped or disk-shaped permanent magnet B and a larger inner diameter are formed on the dielectric upper surface A1. A doughnut-shaped permanent magnet C is disposed, and an alternating electric field is applied along the magnetic neutral line formed in the vacuum chamber A by the permanent magnets B and C to generate discharge plasma in the magnetic neutral line 1 Multiple high frequency coils D including heavy are arranged between the permanent magnets B and C. The diameter of the magnetic neutral line and the distance from the magnet surface are determined by the magnetic field strength of the two permanent magnets B and C and the length of the gap between them. When the magnetic field strengths of the two permanent magnets B and C are equal, a magnetic neutral line is formed inside the vacuum chamber A at an intermediate position between the two permanent magnets B and C.
FIG. 5 shows an equipotential diagram calculated in the magnet arrangement of FIG. The distance from the magnet surface of the formed magnetic neutral line increases as the distance between the two magnets B and C increases, and does not depend on the magnetic field strength. Then, a plasma is generated in the vicinity of zero magnetic field by applying a high-frequency electric field by a high-frequency coil D for introducing a high-frequency electric field provided on the upper dielectric surface A1 having a diameter where a magnetic neutral line is formed.
[0005]
When an Si substrate with an oxide film is etched using the apparatus shown in FIG. 4, when a 100 kHz high frequency power source is used for RF bias, the pressure of cyclobutane octafluoride gas is 0.67 Pa, and RF bias The etching rate and etching uniformity as high as 600nm / min ± 7% are obtained under the conditions of 500W power and 1500W RF antenna power.
The magnetic neutral discharge plasma apparatus previously proposed is a discharge plasma apparatus in which plasma is generated in a vacuum chamber whose upper surface is a dielectric, and continuously exists in the vacuum chamber. A donut-shaped or disk-shaped permanent magnet disposed on the top surface of the dielectric material to form an annular magnetic neutral line at a position of zero magnetic field, and two donut-shaped permanent magnets having a larger inner diameter, and this magnetic field Multiple high frequency coils including a single coil for generating an electric discharge plasma on the magnetic neutral line by applying an alternating electric field between two permanent magnets along the magnetic neutral line formed in the vacuum chamber by the generating means It was the plasma generator comprised from these. It was also confirmed that such a magnetic neutral line discharge plasma apparatus is superior to inductively coupled plasma as well as obtaining a highly efficient magnetic neutral line discharge plasma.
[0006]
[Problems to be solved by the invention]
However, if the magnetic neutral line is formed by the fixed donut-shaped or disk-shaped permanent magnet and the donut-shaped permanent magnet having a larger inner diameter than that, the position of the magnetic neutral line is the magnet. There is a problem that the magnetic field condition cannot be changed.
[0007]
The present invention solves the problems of these conventional devices, and provides a magnetic neutral discharge plasma apparatus that can change the position where a magnetic neutral line is formed and change the magnetic field conditions. The purpose is that.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a donut-shaped or disk-shaped permanent magnet for forming an annular magnetic neutral line, which is a position of zero magnetic field continuously present in a vacuum chamber, and In a conventional magnetic field generating structure composed of a donut-shaped permanent magnet having a larger inner diameter, the position of the magnetic neutral line formed in the vacuum can be changed by changing the relative height of the two permanent magnets. And configured to be variable in size.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to one embodiment of the present invention, the plasma generator comprises:
On the outer surface of the top wall of the vacuum chamber to form an annular magnetic neutral line that is a position of zero magnetic field that continuously exists on a horizontal plane in the vacuum chamber with a top wall, a bottom wall, and a side wall. Magnetic field generation composed of a doughnut-shaped or disk-shaped first permanent magnet and a doughnut-shaped second permanent magnet arranged concentrically with the first permanent magnet and having a larger inner diameter than the first permanent magnet Means,
On the outer surface of the top wall of the vacuum chamber to form an annular magnetic neutral line that is a position of zero magnetic field that continuously exists on a horizontal plane in the vacuum chamber with a top wall, a bottom wall, and a side wall. Magnetic field generation composed of a doughnut-shaped or disk-shaped first permanent magnet and a doughnut-shaped second permanent magnet arranged concentrically with the first permanent magnet and having a larger inner diameter than the first permanent magnet Means,
An electric field composed of multiple high-frequency coils including a single layer for applying an alternating electric field along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means to generate a discharge plasma on the magnetic neutral line. Generating means,
The upper wall of the vacuum chamber in which the first and second permanent magnets are disposed is made of a dielectric, and the electric field generating means is disposed at a position between the first and second permanent magnets.
The first and second permanent magnets are arranged so as to be adjustable at relatively different height positions so that the position where the magnetic neutral line is formed can be controlled.
[0010]
According to another embodiment of the present invention, the plasma generator comprises:
On the outer surface of the top wall of the vacuum chamber to form an annular magnetic neutral line that is a position of zero magnetic field that continuously exists on a horizontal plane in the vacuum chamber with a top wall, a bottom wall, and a side wall. Magnetic field generation composed of a doughnut-shaped or disk-shaped first permanent magnet and a doughnut-shaped second permanent magnet arranged concentrically with the first permanent magnet and having a larger inner diameter than the first permanent magnet Means,
An electric field composed of multiple high-frequency coils including a single layer for applying an alternating electric field along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means to generate a discharge plasma on the magnetic neutral line. Generating means,
At least a part of the cylindrical side wall of the vacuum chamber is made of a dielectric, and the electric field generating means is arranged outside the dielectric part of the cylindrical side wall of the vacuum chamber, and the first, second These permanent magnets are arranged so as to be adjustable at relatively different height positions so that the height and size of magnetic neutral lines can be controlled.
[0011]
[Action]
In the plasma generating apparatus of the present invention configured as described above, the magnetic neutral line formed by the doughnut-shaped or disk-shaped first permanent magnet and the doughnut-shaped second permanent magnet having a larger inner diameter than that is formed. The position and size can be adjusted, and the conditions of the plasma formed by the superposition of the electric field generating means can be changed.
[0012]
【Example】
Embodiments of the present invention will be described below with reference to FIGS.
[0013]
FIG. 1 shows an embodiment in which a plasma generator according to the present invention is applied to an etching apparatus. In the illustrated apparatus, reference numeral 1 denotes a cylindrical vacuum chamber forming a process chamber, the upper surface of which is covered with a flat dielectric partition wall 2. On the outer surface of the flat-type dielectric partition wall 2, a disc-shaped inner permanent magnet 3 having a polarity as illustrated above and below, an inner diameter larger than the disc-shaped inner permanent magnet 3, and the same polarity as the inner permanent magnet 3. A doughnut-shaped outer permanent magnet 4 is concentrically mounted, and both the permanent magnets 3 and 4 constitute a magnetic field generating means for forming a magnetic neutral line in the vacuum chamber 1. As shown in the drawing, the disk-shaped inner permanent magnet 3 is arranged at a position higher than the donut-shaped outer permanent magnet 4, and actually, both the permanent magnets 3, 4 are positioned so as to be adjustable at relatively different height positions. Is provided.
Between the disc-shaped inner permanent magnet 3 and the donut-shaped outer permanent magnet 4, a multiple high-frequency coil 5 including a single layer constituting electric field generating means is disposed. This high-frequency coil 5 is a high-frequency power source having a frequency of 13.56 MHz. 6, an alternating electric field is applied along the magnetic neutral line formed in the vacuum chamber 1 by the permanent magnets 3 and 4 to generate discharge plasma in the magnetic neutral line. A substrate electrode 7 is provided at a position parallel to the surface formed by the magnetic neutral line formed in the vacuum chamber 1, and this substrate electrode 7 applies a RF bias to a high frequency power source 8 having a frequency of 13.56 MHz. It is connected to the.
[0014]
Next, with reference to FIG. 2 and FIG. 3, how much and in what direction the formed magnetic neutral line changes depending on the relative positions of the permanent magnets 3 and 4 will be described.
FIG. 2 and FIG. 3 are isomagnetic potential diagrams obtained by a two-dimensional finite element method of a permanent magnet type magnetic neutral discharge plasma generator with variable relative position according to the present invention.
Depending on the relative height of the two permanent magnets, the changing direction and amount of the magnetic neutral line changes. FIG. 2 is an equipotential diagram calculated by the finite element method when the doughnut-shaped outer permanent magnet 4 is fixed to the top of the dielectric and the inner permanent magnet 3 having a small inner diameter is positioned 40 mm above the dielectric surface. . FIG. 3 is an equipotential diagram calculated by the finite element method when the doughnut-shaped inner permanent magnet 3 is fixed to the upper portion of the dielectric and the outer permanent magnet 4 having a large inner diameter is disposed at a position 40 mm above the dielectric surface. . In the configuration of FIG. 2, the position of the magnetic neutral line is formed 44 mm below the lower surface (upper surface of the dielectric) of the outer permanent magnet 4 placed on the upper surface of the dielectric and 86 mm from the center of the vacuum chamber 1. ing. Similarly, the position of the magnetic neutral line formed in the configuration of FIG. 3 is 26 mm below and 125 mm from the center. As can be seen from FIGS. 2 and 3, the position of the magnetic neutral line moves, and a deep plasma is formed along the magnetic neutral line, so that the plasma can be controlled.
[0015]
The embodiment of FIG. 1 shows an example applied to a “reactive ion etching apparatus” in which a high frequency power of 13.56 MHz is applied to the antenna, that is, the high frequency coil 5 and a high frequency power of 13.56 MHz is also applied to the substrate electrode 7. Has been. Using the etching apparatus having the magnetic field arrangement shown in FIGS. 2 and 3, using the Si substrate with an oxide film, and using a 100 kHz high frequency power source for RF bias, the apparatus shown in FIG. As a result of an experiment under the same conditions as in the above (pressure of cyclobutane octafluoride gas is 0.67 Pa, RF bias power is 500 W, and RF antenna power is 1500 W), the arrangement shown in FIG. The etching rate was as high as 550 to 650 nm / min, as was the case with
[0016]
Further, it was found that the uniformity can be varied depending on the relative positions of the two permanent magnets 3 and 4. From the results so far, in the arrangement of FIG. 2, the etching rate distribution at the center has a large convex etching rate distribution, and in the arrangement of FIG. 3, the etching rate at the center has a low concave etching rate, It was found to vary between ± 5 and ± 15%. When the permanent magnet arrangement shown in FIGS. 2 and 3 was used, the condition with relatively good uniformity was the arrangement side of FIG. it is conceivable that. It is considered that more uniform conditions can be obtained by further optimizing the arrangement of the two magnets.
[0017]
By the way, in the illustrated embodiment, one of the two permanent magnets is fixed to the upper part of the dielectric, and all or part of the cylindrical upper wall of the vacuum chamber 1 is made of a dielectric, and has a large inner diameter outside thereof. Permanent magnets may be arranged. Alternatively, the upper dielectric may be concave, and a permanent magnet having a small inner diameter may be disposed in the recess.
[0018]
The position of the antenna or high-frequency coil 5 that introduces an alternating electric field along the magnetic neutral line does not need to be in the middle of the permanent magnets 3 and 4 because the position of the antenna or the high-frequency coil 5 is stainless steel. The upper part may be made of a material, the cylindrical side wall may be made of a dielectric, and the antenna may be arranged outside the dielectric cylindrical side wall.
[0019]
Further, although a high frequency of 13.56 MHz is used for the high frequency coil 5 for introducing a high frequency electric field, it is not limited to this frequency. Similarly, the high frequency applied to the substrate electrode 7 is not limited to 13.56 MHz. When power supplies having the same frequency are used for the antenna and the substrate electrode, a phase control circuit for adjusting the phase between the two power supplies is generally required.
In the illustrated embodiment, the case where the plasma generating apparatus of the present invention is applied to an etching apparatus has been described, but the same effect can be obtained in a CVD apparatus.
[0020]
【The invention's effect】
As described above, according to the present invention, in a magnetic field structure composed of a donut-shaped or disk-shaped permanent magnet that forms a magnetic neutral line and two donut-shaped permanent magnets having a larger inner diameter than that, Since the structure is such that the relative height of the two permanent magnets can be changed and the position and size of the magnetic neutral line can be made variable, the position of the magnetic neutral line can be selected arbitrarily. In addition, it is possible to provide a discharge plasma apparatus in which the position of the magnetic neutral line, which cannot be achieved with the conventional configuration in which the permanent magnet is fixed, can be made variable.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment in which a plasma generating apparatus according to the present invention is applied to a magnetic neutral line discharge etching apparatus.
FIG. 2 is a graph showing a calculation result by a finite element method of isomagnetic lines obtained by the magnetic field generation structure of the plasma generator of the present invention.
FIG. 3 is a graph showing a calculation result by a finite element method of isomagnetic lines obtained by another magnetic field generation structure of the plasma generator of the present invention.
FIG. 4 is a schematic view showing an example of a conventional magnetic neutral wire discharge etching apparatus using permanent magnets.
5 is a graph showing a calculation result by a finite element method of isomagnetic lines obtained by the magnetic field generation structure shown in FIG. 4;
[Explanation of symbols]
1: Vacuum chamber 2: Flat plate type dielectric partition 3: Inner permanent magnet 4: Outer permanent magnet 5: High frequency coil 6: High frequency power source

Claims (2)

On the outer surface of the top wall of the vacuum chamber to form an annular magnetic neutral line that is a position of zero magnetic field that continuously exists on a horizontal plane in the vacuum chamber with a top wall, a bottom wall, and a side wall. Magnetic field generation composed of a doughnut-shaped or disk-shaped first permanent magnet and a doughnut-shaped second permanent magnet arranged concentrically with the first permanent magnet and having a larger inner diameter than the first permanent magnet and means,
An electric field composed of multiple high-frequency coils including a single layer for applying an alternating electric field along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means to generate a discharge plasma on the magnetic neutral line. includes a generating means <br/>,
First, the top wall of the vacuum chamber in which the second permanent magnets are arranged with a dielectric, disposed above electric field generating means to a first position between the second permanent magnets,
A plasma generator characterized in that the first and second permanent magnets are arranged so as to be adjustable at relatively different height positions so that the position where the magnetic neutral line is formed can be controlled. On the outer surface of the top wall of the vacuum chamber to form an annular magnetic neutral line that is a position of zero magnetic field that continuously exists on a horizontal plane in the vacuum chamber with a top wall, a bottom wall, and a side wall. Magnetic field generation composed of a doughnut-shaped or disk-shaped first permanent magnet and a doughnut-shaped second permanent magnet arranged concentrically with the first permanent magnet and having a larger inner diameter than the first permanent magnet and means,
An electric field composed of multiple high-frequency coils including a single layer for applying an alternating electric field along the magnetic neutral line formed in the vacuum chamber by the magnetic field generating means to generate a discharge plasma on the magnetic neutral line. includes a generating means <br/>,
Form part of a dielectric even without less of the cylindrical side wall of the vacuum chamber, said electric field generating means, arranged outside the dielectric portion of the cylindrical side wall of the vacuum chamber, the first, second 2. A plasma generator characterized in that the two permanent magnets are arranged so as to be adjustable at relatively different height positions so that the height and size of magnetic neutral lines can be controlled.

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