JPH0551772A - Ion etching method and device - Google Patents

Abstract

PURPOSE:To allow anisotropic etching of a high speed, high quality, high selection ratio and uniform in a large area with a magnetron type ion etching device by adequately controlling a magnetic field, thereby decreasing a self-bias voltage and rotating the magnetic field. CONSTITUTION:A chamber 1 is internally evacuated to a vacuum and an etching gas is introduced from an introducing port 20 into the chamber to generate a prescribed pressure. An electric discharge is generated between a cathode electrode 4 and an anode electrode 2 by impressing RF electric power to the cathode electrode 4, by this plasma is formed and a substrate 5 is etched. An RF power source 15 and a stepping motor 14 are controlled via an interface 19 by a computer 18 to stepwise drive an insulator gear 13 and to move a post 7 so as to change the distance between a substrate stage 3 and a permanent magnet 6, by this, the specified self-bias voltage is established. Further, the permanent magnet 6 is rotated by the stepping motor 14A to uniformize the etching speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material etching technique, and more particularly to a magnetron type ion etching method and apparatus.

[0002]

2. Description of the Related Art In a magnetron type ion etching apparatus (hereinafter referred to as M-IE apparatus), a magnetic field generator is attached to an ordinary ion etching apparatus (hereinafter referred to as IE apparatus) to use a magnetic field in addition to an electric field. The configuration is An example of such a conventional M-IE device is shown in FIG. In FIG. 1, 1 is a chamber, and in this chamber 1,
The grounded anode electrode 2 and the cathode electrode 4, which is attached to the cathode support, that is, the substrate stage 3 and is arranged to face the anode electrode 2, are arranged in parallel. Below the cathode support base 3, a pillar 7A of a yoke 7, which will be described later, is provided.
A cylindrical portion 3A that penetrates and is fixed is provided. A substrate 5 as a sample is placed on the surface of the cathode electrode 4 facing the anode electrode 2. A permanent magnet 6 is arranged near the lower portion of the cathode electrode 4, that is, on the back surface side of the cathode support 3. Reference numeral 7 is a yoke forming a magnetic path of the magnet 6. Reference numeral 8 represents a magnetic flux passing from the magnet 6 to the sample 5. Reference numeral 9 denotes an insulator which is interposed between the cathode support base 3 and the cathode support base 3 when the cathode support base 3 is mounted in the chamber 1. Reference numeral 10 denotes a cooling water outlet pipe provided on the cathode support base 3. Reference numeral 20 is a gas inlet for introducing gas into the chamber 1, and 21 is a vacuum pump system for evacuating the chamber 1. High frequency power from a high frequency (RF) power source 15 is applied to the cathode electrode 4 by the matching box 16 and the cathode support 3.
Is applied via. A high-frequency voltmeter 17 measures the output voltage of the matching box 16.

In the M-IE device in which the electric field E and the magnetic field B are orthogonal to each other, the electrons in the cathode sheath perform a cyclotron motion. This motion increases the probability of collision of electrons with neutral atoms and molecules, which increases the probability of ionization,
Thus, high density plasma (a large amount of ions and electrons) can be formed between the cathode and the anode.

There are four processing parameters in the IE device and the M-IE device: input power, gas pressure, and self-bias voltage and magnetic field strength (only for the M-IE device) described below.

Normally, when high frequency power is applied to the cathode electrode in a rare gas, plasma is formed by this, and a sheath of positive ions is formed on the surface of the cathode electrode. Due to the self-bias voltage in this sheath region, the ions between the cathode and the anode are accelerated toward the cathode and the material is etched.

Even if good anisotropic etching can be performed with a certain gas voltage, power, and pressure, as the applied power is increased in order to increase the etching rate, the self-bias voltage also increases and the processing is performed. Damage is increased.

Further, in IE, since there is no non-uniform magnetic field, a uniform etching region can be obtained over a wide range, but there is a problem that the etching rate is slow due to the low plasma density.

The ion sheath depends on the density distribution of the plasma. In the M-IE applying a magnetic field, the distribution of the magnetic field strength causes the plasma density and the distribution of ions in the sheath region. Is high and the density is low where the strength is low. Due to the distribution of these plasma densities, the etching region could not be made uniform.

[0009]

In either case, the self-bias voltage increases as the power density increases and cannot be controlled independently. In addition, conventional M
-Because the magnetic field is used in the IE device, the self-bias voltage is smaller than that in the IE device.
A value of 100 V or less cannot be obtained because the strength of the applied magnetic field is small.

The magnitude of the self-bailing voltage at the time of etching not only determines the processing speed (sputtering rate) of the material, but also the selection ratio (determination of the quality of the processed surface and the quality of the pattern of the processed material). It is the etching rate ratio of the processing material and the mask, and the larger this value is, the better anisotropic etching can be performed).

The self-bias voltage changes with the magnetic field strength and decreases as the magnetic field strength increases. The magnetic field strength in the conventional M-IE device is about several hundred Gauss, and the magnitude of the self-bias voltage obtained thereby is 100 V or more. Therefore, the surface to be processed is greatly damaged, and reducing this damage is an important issue.

Further, the M-IE apparatus has a large etching rate by using a magnetic field as compared with the IE apparatus, and has excellent characteristics from an industrial viewpoint such as high-speed processing, low damage, and high selection ratio. Since a uniform magnetic field strength has a distribution, it was not possible to obtain a uniform etching region. Therefore, making the etching distribution uniform is also an important issue.

Therefore, an object of the present invention is to appropriately control the magnetic field to reduce the self-bias voltage, and to rotate the magnetic field to eliminate the above-mentioned conventional drawbacks, and to make a large area uniform, high speed and high quality. Another object of the present invention is to provide an ion etching method and apparatus capable of performing anisotropic etching with a high selectivity.

[0014]

In order to achieve such an object, the method of the present invention comprises arranging first and second electrodes in parallel with each other in a vacuum chamber, grounding the first electrode, and High frequency power is supplied to the second electrode, the sample is placed on the main surface of the second electrode opposite to the first electrode, and a magnet is placed below the other main surface of the second electrode. In the ion etching method using the arranged magnetron type ion etching apparatus, the magnet is moved so as to change the distance between the magnet and the second electrode, and self-applied to the second electrode during ion etching. The bias voltage is always set to a desired value and independent of the high frequency voltage and the pressure of the gas introduced into the vacuum chamber, and the magnet under the second electrode is rotated. hand The etching region formed on the second electrode during ion etching is set to be always uniform and independent of the high frequency power and the pressure of the gas introduced into the vacuum chamber. And

In the device of the present invention, the first and second electrodes are arranged in parallel with each other in a vacuum chamber, the first electrode is grounded, high frequency power is supplied to the second electrode, and the second electrode is A magnetron-type ion etching apparatus in which a sample is placed on a main surface opposite to a first electrode and a magnet is arranged below the other main surface of the second electrode, wherein the magnet and the second electrode are provided. The magnet is configured to be movable so as to change the distance between and, and the magnet under the second electrode is rotatable.

[0016]

In the present invention, the permanent magnet arranged on the back surface side of the substrate stage is movable with respect to the substrate stage so that the distance between the permanent magnet and the substrate stage can be changed. Apart from the value of the self-bias voltage induced, the self-bias voltage can be set to any desired value by appropriately setting the distance between the substrate stage and the permanent magnet.

The self-bias voltage decreases as the magnetic field strength on the substrate stage increases, and conversely increases as the magnetic field strength decreases. Therefore, the self-bias voltage can be adjusted to any desired value by changing the distance between the permanent magnet and the substrate stage to change the magnetic flux density on the substrate surface. By controlling the magnetic flux density while constantly monitoring the voltage value using a high-frequency voltmeter,
The self-bias voltage can always be set to any desired constant value.

Further, since the permanent magnet arranged on the back surface side of the substrate stage can be rotated with respect to the substrate stage, by appropriately determining the distribution of the ion sheath and plasma formed on the substrate stage during discharge, The etching depth per unit time, that is, the etching rate can be made uniform. When the self-bias voltage is constant, the etching rate increases when the plasma density on the substrate stage is increased, and conversely decreases when the plasma density is decreased. Therefore, the arrangement of the etching region and the permanent magnet can be set based on the relationship between the plasma density (magnetic flux density) on the surface of the substrate stage and the etching rate.

In order to solve the above-mentioned problems, the present inventors use a permanent magnet having a large magnetic field strength and increase the applied magnetic field strength by about one digit as compared with the conventional one, thereby decreasing the self-bias voltage value, and The desired value could be obtained. Furthermore, by arranging the magnet appropriately,
Give a desired etching area distribution on the substrate stage,
By combining this etching area distribution control and the magnetic field rotation mechanism, it was possible to obtain an etching area with a uniform depth over a wide range on the substrate stage.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIG. 2 shows the construction of an embodiment of the ion etching apparatus of the present invention. In this device,
The same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

A cylindrical portion 3A provided on the cathode support base 3 slidably supports the yoke support 7A, and an O-ring 11 for hermetically sealing the inside of the chamber 1 is provided inside the cylindrical portion 3A. Arrange. A gear knob 12 is formed on the lower side of the column 7A. A gear 13 made of an insulator is meshed with the gear knob 12. This gear 13 is stepwise driven by a stepping motor 14 to move the support 7 in the direction of the arrow,
That is, the direction in which the distance between the substrate stage 3 and the magnet 6 is changed (in the illustrated example, the direction perpendicular to the substrate stage 3).
It is possible to move to a magnetic field strength control mechanism.

Further, the column 7A is the stepping motor 1
The rotation of the permanent magnet can be controlled from 0 to 2000 rpm by 4A. In this case, the stepping motor 14A is the gear knob 1
Although it is a mechanism that moves up and down with the vertical movement of 2, the gear knob 12 may have a double shaft structure and the stepping motor 14A may be fixed. Also, the stepping motors 14 and 14A
Both may be ordinary motors. According to the above configuration, the magnet 6 is capable of both rotation and vertical movement.

Reference numeral 18 is a computer, which takes in the self-bias voltage measured by the high-frequency voltmeter 17 through the interface 19 and stores it. In this state, the computer 18 controls the RF power supply 15 and the stepping motor 14 via the interface 19 in order to adjust the applied power and the self-bias voltage, respectively. That is, the computer 18 variably operates the magnetic field strength so that the self-bias voltage becomes constant. Further, the permanent magnet is rotated by the stepping motor 14A to make the etching rate uniform.

In this embodiment, it is needless to say that an electromagnet may be used instead of the permanent magnet 6, but a permanent magnet is suitable as a magnet that can move and rotate and has a strong magnetic field, and the material is samarium cobalt. Rare earth magnets such as are suitable.

This device operates as follows. First, the chamber 1 is moved to about 1 × 1 by the vacuum pump system 21.
After evacuating to about 0 ^-7 Torr, gas inlet 2
Etching gas, for example, O ₂ gas at 1 × 10 ⁻³
Introduce until Torr. Next, when RF power is applied to the cathode electrode 4 by the RF power source 15, a discharge is generated between the cathode electrode 4 and the anode electrode 2, and plasma is formed. At this time, the substrate 5 is placed on the cathode electrode 4 placed on the cathode support 3 and cooled by the cooling water flowing from the cooling water outlet pipe 10. In the high frequency power meter 17, a certain self-bias voltage is induced by the above discharge. Here, the permanent magnet moving gear knob 12, the insulator gear 13, and the stepping motor 14
By using, the permanent magnet 6 can be moved in the direction of the arrow in the drawing, that is, in the direction perpendicular to the substrate 5. As a result, the value of the self-bias voltage displayed on the high frequency power meter 17 can be controlled within the range of -30V to -1kV.

FIG. 3 is a characteristic diagram showing the relationship between the self-bias voltage and the magnetic field strength in the present invention. From FIG.
It can be seen that the larger the magnetic field strength, the smaller the self-bias voltage. In this case, in order to realize an ultra-high selection ratio and ultra-high quality processing, a magnetic field strength that provides a self-bias voltage of several + eV is ideal.

Here, the ultrahigh selectivity etching will be described. Etching proceeds by the synergistic effect of ions (physical effect) and radicals (chemical effect) in plasma. Among them, the ions collide with the substrate in a directional manner, so that the anisotropy at the time of etching is determined, and the radicals are adsorbed on the substrate surface and react with the atoms constituting the substrate to have high volatility. The etch rate of the material is primarily determined as it forms and leaves the compound. In this way, the material is processed by the ions and radicals. on the other hand,
The mask formed on the substrate material also undergoes ion collision and radical reaction as in the substrate material. Since the mask material hardly reacts with radicals, it is only scraped by ion bombardment. Since it is ideal that the mask will not be scraped or deformed (retracted), the energy of ions is desired to be as small as possible. Specifically, if the kinetic energy of the ions can be lowered to about the displacement threshold energy of the material constituent atoms (the minimum energy required for the material to be sputtered, about 20 eV), the mask material is It is hardly shaved, and only the material to be processed is etched by ion bombardment and radical reaction. Therefore, if such an ideal state is formed, the amount of mask processing becomes zero, and anisotropic etching with an infinite etching rate ratio between the mask and the material to be processed, that is, the selection ratio can be realized. ..

Next, ultra-high quality processing will be described. As described in the description of the ultra-high selectivity etching, if the ion energy during processing can be reduced to about 20 to 30 eV, the etching proceeds in an ideal state. That is, the surface of the substrate is subjected to ion bombardment, but since the energy is the minimum required to remove the substrate atoms, the surface damage after processing is also in the minimum state. From this, the processed surface is close to the most ideal processed surface. Therefore, the self-bias voltage mentioned above must be
It may be about V. In the present invention, by applying a large magnetic flux of 1000 gauss or more, it can be seen that a low energy self-bias voltage of −100 V or less, which was not obtained in the past, can be obtained. When the magnetic field of 2000 gauss was applied, the self-bias voltage of about -30V was obtained.

The self-bias voltage and RF power density
Fig. 4 plots the relationship with. Where
O as a ching gas₂ Gas pressure 5 × 10^-3At Torr
Introduced. Power density refers to the value of power as the electrode area (100
cm² ) Shows the value divided by. With this device,
Range of 50-300W (power density 0.5-3W / cm
² ), The self-bias voltage can be controlled to be constant
I understand. In this case, as the power density increases
Processing speed increases, but power density is 2 to 3 W / c
m² 1W / cm even when processed by² Obtained at
It can be seen that the processed shape pattern can be maintained as it is.
It was

Further, FIG. 5 shows the relationship between the value of the self-bias voltage and the etching rate ratio between the mask and the material to be processed when processing the material, that is, the selection ratio. here,
Ti was used as the mask material, and polyimide was used as the material to be processed. Therefore, the selection ratio is (polyimide etching rate)
/ (Ti etching rate). Here, the selection ratio increased as the self-bias voltage decreased, and at the self-bias voltage of −40 V, the selection ratio of 1000 times was obtained.

FIG. 6 shows the relationship between the etching depth of the material (polyimide) and the time in such a state. Here, the rotation speed of the magnet was 1500 rpm, the self-bias voltage was −45 V, and O ₂ gas as an etching gas was introduced at a pressure of 5 × 10 ⁻³ Torr. High frequency power 20
The characteristics in two cases of 0,600 W are shown. From this characteristic diagram, it is understood that the etching depth can be accurately controlled with time. The etching rate in the case of 600 W is about 5 μm / min, which is about 5 times as large as that of the conventional apparatus. This is because a high-density plasma is formed between the electrodes due to a magnetic field of about 2000 Gauss, which is larger than the conventional one by about one digit, and the material is etched by a large amount of generated ions.

Further, it has been found that if the self-bias voltage can be reduced in this way, the quality of the machined surface can be improved as described below. That is, in the energy range shown in FIG. 5, only the energy was changed, the etching gas was set to CF ₄ , and the other processing parameters were kept constant to perform Si etching. afterwards,
When the defects were evaluated by wet etching, it was found that the processing damage at a self-bias voltage of 40 V or less was comparable to chemical etching, and there was no processing damage. This suggests that etching is performed while maintaining an ideal processed surface.

(Embodiment 2) An application embodiment of the above apparatus for the purpose of making the etching rate uniform in the etching region will be described in detail below.

First, FIG. 7 shows the magnetic field dependence of the etching rate for designing the magnetic field. The etching conditions are
Power density 2 W / cm ² , etching gas; argon, sample; tungsten, gas pressure 1 × 10 ^-2 Torr, substrate temperature 20 ° C. The etching rate monotonically increases with an increase in the magnetic field and reaches its maximum at 500 gauss. The rate decreases monotonically with further increase.

Next, a magnetic field is designed based on this figure. A design example will be described below. First, FIG. 8 shows a schematic view of the arrangement of the cathode permanent magnets.

The magnet design of this cathode is a magnet arrangement such that the average magnetic field strength per unit time per unit area during rotation is constant, that is, the magnetic field strength is proportional to the radial distance when stopped. Is an example of the arrangement. The magnets are made of the same material, and the magnetizing moment is constant in all parts of the magnet. Here, the shape of the magnet will be described.
Consider the case where the center of the circle is the origin 0, the x-axis and the y-axis are set as shown in the figure, the magnet is composed of four parts, and the S poles and the N poles are alternately arranged.

[0038]

[Outer 1]

[0039]

[Outside 2]

[0040]

[Outside 3]

[0041]

[Outside 4]

In the cathode designed by the above method,
The leakage magnetic field on the cathode surface was measured in the radial direction. In this case, 1 was 15 cm, and the S-N pole gap in the outer peripheral portion was 2 cm. The results are shown in Fig. 9. As designed, the leakage magnetic field is approximately proportional to 5 from the center to the radial direction.
Increasing to 00 Gauss, the desired magnetic field distribution was obtained.

As the backing plate on the cathode surface, a composite plate with a magnetic shielding material such as permalloy is used, and the average leakage magnetic field strength on the entire target surface is optimized by changing the thickness of the plate (from the central magnetic field strength). The average magnetic field strength is preset so that the etching rate is proportional to the magnetic field strength at the outer circumference.

In the above description, the number of magnets in which the S pole and the N pole are paired is four, but it may be two or eight. If the number of sheets is 8 or more, leakage of magnetic field lines to the outside is reduced, which is not suitable. Of the two, four, and eight configurations,
From the viewpoint of the distribution of magnetic force lines and leakage of magnetic force lines, the four-sheet structure is most suitable.

Further, as a specific dimension of the above l, for example, as described above, 15 cm is suitable, and the gap between the S pole and the N pole in the outer peripheral portion is about 2 cm.

Further, in order to actually machine the outer peripheral shape of the magnet represented by y = f (x), a method of repeating linear machining in multiple stages is adopted, and the machining linear width is set within a range in which it is cost effective. It can be handled by making it smaller (more stages).

Further, in the above-mentioned magnet arrangement, the central ends of the respective magnet pieces are made to coincide with each other, but in practice, there is no problem even if the respective ends are made coincident with each other, separated from each other, or further overlapped.
Therefore, it may be appropriately selected in actual processing.

Next, the uniformity of the etching depth when the magnet was rotated to etch the cathode for 1 hour was examined. The results are shown in Fig. 10. As is clear from the figure,
It is uniformly etched except for the center and outer periphery.

Similarly, other materials (dielectrics such as SiO ₂ ,
In the case of etching a magnetic material such as CoCr), the etching was performed at a uniform depth by using the same method as described above.

[0050]

As described above, according to the present invention, the permanent magnet arranged on the back surface side of the substrate stage can be moved with respect to the substrate stage so that the distance between the permanent magnet and the substrate stage can be changed. Since this is done, the self-bias voltage induced in the substrate stage during discharge can be reset to any desired value. Moreover, since the self-bias voltage can be lowered by using a permanent magnet having a large magnetic field strength, high-speed and high-quality anisotropic etching can be performed with a high selection ratio.
Also, by rotating the permanent magnet arranged on the back surface side of the substrate stage with respect to the substrate stage, the etching region formed on the substrate stage during discharge can be made uniform over a wide area, and a uniform depth can be achieved over a large area. Etching is possible. Therefore, the present invention provides a material such as a dielectric having a small sputtering rate and being hard to be scraped, an etching mirror of an LD (laser diode), a part requiring smoothness and verticality of an end surface, and a large size. It is suitable for processing such as pattern formation of parts and the like in an industrial process in which a uniform etching area is required.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a conventional example.

FIG. 2 is a configuration diagram showing an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between the self-bias voltage and the magnetic flux density in the present invention.

FIG. 4 is a characteristic diagram showing a relationship between self-bias voltage and power density in the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a selection ratio and a self-bias voltage according to the present invention.

FIG. 6 is a characteristic diagram showing a relationship between etching depth and time in the present invention.

FIG. 7 is a diagram showing magnetic field strength dependence of an etching rate for designing a magnetic field.

FIG. 8 is a plan view schematically showing a cathode permanent magnet.

FIG. 9 is a characteristic diagram showing the relationship between the magnetic field strength and the distance from the center of the cathode.

FIG. 10 is a characteristic diagram showing the relationship between the etching depth and the distance from the center of the cathode.

[Explanation of symbols]

 1 Chamber 2 Anode Electrode 3 Cathode Support Base (Substrate Stage) 3A Cylindrical Part 4 Cathode Electrode 5 Substrate 6 Permanent Magnet 7 Yoke 7A Strut 8 Magnetic Flux 9 Insulator 10 Cooling Water Outlet Pipe 11 O-Ring 12 Gear Knob 13 Insulator Gear 14 Stepping Motor 14A Stepping motor 15 RF power supply 16 Matching box 17 High-frequency voltmeter 18 Computer 19 Interface 20 Gas inlet 21 Vacuum pump

Claims (8)

[Claims] 1. A first and a second electrode are arranged in parallel with each other in a vacuum chamber, the first electrode is grounded, and the second electrode is grounded.
High frequency power is supplied to the electrode, the sample is placed on the main surface of the second electrode opposite to the first electrode, and the magnet is arranged below the other main surface of the second electrode. In an ion etching method using a magnetron type ion etching apparatus, the magnet is moved so as to change a distance between the magnet and the second electrode, and a self-bias voltage applied to the second electrode during ion etching. Is always set to a desired value, and independently of the high frequency voltage and the pressure of the gas introduced into the vacuum chamber, and while rotating the magnet below the second electrode, The etching area formed on the second electrode during the ion etching is set to be always uniform and independent of the high frequency power and the pressure of the gas introduced into the vacuum chamber. Ion etching method which is characterized in that to be. 2. The magnet comprises a plurality of magnets having a pair of south and north poles, and these magnets are evenly arranged along the outer circumference of rotation.
The ion etching method described in. 3. The ion etching according to claim 1, wherein the magnet is a magnet that generates a magnetic flux that gives a self-bias voltage corresponding to the sputtering threshold energy of the sample. Method. 4. A first and a second electrode are arranged in parallel with each other in a vacuum chamber, the first electrode is grounded, and the second electrode is grounded.
High frequency power is supplied to the electrode, the sample is placed on the main surface of the second electrode opposite to the first electrode, and the magnet is arranged below the other main surface of the second electrode. In the magnetron ion etching apparatus, the magnet is configured to be movable so as to change the distance between the magnet and the second electrode, and the magnet under the second electrode is rotatable. Ion etching equipment. 5. The ion etching apparatus according to claim 4, wherein the magnetic field applied to the second electrode has a distribution, and a uniform etching region is formed by controlling the rotation of the magnet. 6. The ion etching apparatus according to claim 4, wherein the high frequency voltage applied to the second electrode is measured, and the movement of the magnet is controlled according to the measured voltage. 7. The high frequency voltage applied to the second electrode is measured, and the value of the high frequency voltage applied to the second electrode is controlled according to the measured voltage. 7. The ion etching apparatus according to any one of 1 to 6. 8. The magnet according to claim 4, wherein the magnet generates a magnetic flux that provides a self-bias voltage corresponding to the sputtering threshold energy of the sample. Ion etching equipment.