KR20000060791A - Inductively coupled plasma apparatus - Google Patents

Abstract

PURPOSE: An inductively-coupled plasma apparatus having an intensified magnetic field is to provide a high plasma uniformity, a density and an etching speed. CONSTITUTION: An inductively-coupled plasma apparatus having an intensified magnetic field comprises a reaction chamber(1), an inducting element(2) and a magnetic field generating element(3). The reaction chamber has a rectangular section and receives at least one test piece for a predetermined process by plasma. The inducting element supplies a radio frequency source power into the reaction chamber to generate plasma in the reaction chamber. The magnetic field generating element is established inside the reaction chamber to supply a magnetic field for putting the plasma into the reaction chamber.

Description

Magnetically enhanced inductively coupled plasma device {INDUCTIVELY COUPLED PLASMA APPARATUS}

The present invention relates to a plasma apparatus, and more particularly to a magnetic field-enhanced inductively coupled plasma apparatus.

The etching process of the semiconductor manufacturing process is to selectively remove the thin film directly under the opening of the photoresist layer, which is a photosensitive resin, and can be roughly divided into wet etching and dry etching. Wet etching is economical because the wafer is immersed in an acid in a boat and etched through an acid or chemical reaction with an acid mixture. However, wet etching has a disadvantage in that the precision of etching is poor. Dry etching is developed for the formation of fine patterns and uses etching gas instead of etching liquid in wet etching. One of the most commonly used dry etching in the semiconductor process is plasma etching using plasma.

Plasma is an ionized gas composed of cations, anions, electrons, excited atoms, molecules, and radicals that are very chemically very active, and because they have very different properties from ordinary gases, electrically and thermally, It may also be called the fourth state of. Plasma can be roughly classified into a low temperature glow discharge plasma having a temperature of tens of thousands of degrees and a density of 10 ^{9-10 10} cm ^-3 and an ultra-high temperature fusion plasma having a temperature of tens of thousands of degrees and a density of 10 ^{13 -10 14} cm ^-3 . In the semiconductor etching process, low-temperature glow discharge plasma having a low degree of ionization containing approximately 90% of neutral gas may be used. However, the plasma having low ionization degree exhibits a completely different behavior from the gas in the molecular state which is not ionized. That is, since the plasma contains ionized gas, it may be accelerated or chemically reacted in the plasma or on the solid surface in contact with the plasma by applying an electric or magnetic field.

In recent years, in the semiconductor process, dry etching has been gradually increasing using plasma equipment using high density plasma. This is because as the degree of integration of semiconductor devices increases, the demand for micromachining increases, while the use of large diameter wafers having a diameter larger than 8 inches is increasing. Therefore, the necessity of etching at a high etching rate at low process pressure is increasing. In particular, in the manufacturing process of flat panel displays having various forms such as thin-film-transistor (TFT) -Plasma Display Panels (PDPs) and field emission displays (FEDs), a larger-area substrate is used than silicon wafers. In addition, there is a need for a square specimen process rather than a circular substrate such as a silicon wafer. Therefore, in the development of dry etching equipment for flat panel displays, it is very important to maintain a high density and uniform plasma at the corners as well as the center region in the rectangular reaction chamber.

In the high-density plasma, according to Lorentz's law, when an electron incident into a magnetic field undergoes a circular orbital rotation, an ECR (eletron cyclotron resonance) plasma, a helicon or a Whistler wave (resonance phenomenon) is applied to the microwave by applying a microwave of resonance frequency thereto. There are helicon plasmas using whistler waves, helical resonators to excite slow waves, and inductively coupled plasmas using plasma of high temperature and low pressure.

High-density plasma can control the energy of ions incident on the substrate by transferring power independently to the substrate, have a high decomposition rate of the reaction gas at a low process pressure and can obtain a high ion density. Particularly, inductively coupled plasma has a low plasma loss since the plasma is generated from a place where the wafer is outside the influence of the electromagnetic field generated from the helical coil above the reaction chamber and is not several times the average free path from the wafer surface. I belong to the side.

However, in the conventional inductively coupled plasma apparatus, plasma uniformity, density, and etching rate are not sufficient to perform a large-area substrate and rectangular specimen process required for the manufacturing of flat panel displays such as PDP and FED including TFT-LCD. There is a problem that can not perform a high quality process, such as low.

Accordingly, it is an object of the present invention to provide an inductively coupled plasma apparatus and an etching method thereof capable of obtaining high plasma uniformity, density and etching rate.

1 is a schematic diagram of an inductively coupled plasma apparatus according to the present invention;

2 is a schematic view of a permanent magnet disposed in various forms in the reaction chamber in the inductively coupled plasma apparatus of FIG.

Figure 3 (a) is the intensity and distribution of the magnetic field by the permanent magnet inside the reaction chamber,

3 (b) is the intensity and distribution of the magnetic field by the electromagnet provided outside the reaction chamber,

4 is a graph of ion saturation current measured when the permanent magnet is installed in the reaction chamber and when it is not;

5 (a) is a graph of ion density of Ar plasma measured when the permanent magnet type 2 or 4 is provided in the reaction chamber and when it is not;

5 (b) is an ion density graph of Ar plasma measured when a permanent magnet is not provided inside the reaction chamber;

5 (c) is a graph of ion density of Ar plasma measured when the permanent magnet type 4 is installed inside the reaction chamber;

6 (a) and 6 (b) are graphs of ion densities of Ar plasmas measured at the center and the periphery of the reaction chamber when the permanent magnet type 4 is provided inside the reaction chamber;

7 is an ion density graph of Ar plasma according to a magnetic field change caused by an electromagnet disposed outside the reaction chamber as to whether or not permanent magnet type 4 is installed in the reaction chamber;

8 (a), (b) and (c) are graphs showing changes in ion plasma density, plasma potential, and electron temperature of an Ar plasma with or without an electromagnet outside the reaction chamber in the permanent magnet type 4;

9 is an etching rate graph of polysilicon measured according to whether a permanent magnet type 4 or an electromagnet is installed inside or outside the reaction chamber,

10 is a graph showing the concentration of Cl radicals measured according to whether a permanent magnet type 4 or an electromagnet is installed inside or outside the reaction chamber, respectively.

* Explanation of symbols for the main parts of the drawings

1: reaction chamber 2: induction coil

3: electromagnet 4: electrostatic probe

6: permanent magnet 7: crystal window

9: susceptor

According to the present invention, there is provided an inductively coupled plasma apparatus comprising: a reaction chamber having a rectangular cross section for receiving at least one specimen for a predetermined treatment by plasma; Inducing means for providing RF source power in the reaction chamber to generate a plasma in the reaction chamber; It is achieved by an inductively coupled plasma apparatus comprising a magnetic field generating means provided inside the reaction chamber for providing a magnetic field for confining the plasma in the reaction chamber.

Here, the magnetic field generating means provided inside the reaction chamber is preferably at least one pair of permanent magnets in which the N pole and the S pole are arranged at equal intervals.

On the other hand, the inductively coupled plasma apparatus preferably further includes an electromagnet provided outside the reaction chamber.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of an inductively coupled plasma apparatus according to the present invention. As shown, the inductively coupled plasma apparatus according to the present invention includes a reaction chamber 1 having a square cross section whose surface is made of anodized aluminum, and a height control for supporting a wafer in the reaction chamber 1. A susceptor (9), an induction coil (2) wound in a flat spiral shape four times with a copper-coated copper wire which is located above the reaction chamber (1), and coated with gold, and an induction coil (2) and a reaction chamber. Interposed between (1) and a 24 mm quartz window (7), an RF window for separating the reaction chamber (1) and the induction coil (2) spatially, and the like on the inner wall of the reaction chamber (1). The squares are formed on the outer side of the upper and lower edges of the 6 mm x 8 mm x 14 mm small permanent magnet 6 and the reaction chamber 1 each having a plurality of pairs of 3000 gauss surface magnetic fields arranged alternately at intervals. Electromagnets (3) installed in the form of Helmholtz coils of 40 times wound 50 cm x 50 cm It is.

On the other hand, in order to analyze the effect according to the arrangement state of the permanent magnet in the reaction chamber (1), as shown in FIG. Types 1, 2 and 3 are eight pairs of permanent magnets arranged in pairs of N and S poles with alternating magnetic poles. The distance between the center and the center is 14 pairs in total 2.8cm apart.

As described above, the inductively coupled plasma apparatus according to the present invention has at least one pair of permanent magnets 6 inside the reaction chamber 1 or at least one pair of electromagnets 3 outside the reaction chamber 1. As a result, the strength of the magnetic field in the reaction chamber 1 was enhanced.

FIG. 3 (a) shows the intensity and distribution of the magnetic field from the permanent magnet measured along the radial direction of the reaction chamber 1 at a position 1.5 cm above the center of the substrate in the reaction chamber using a Gaussian. For permanent magnets used, we chose Type 5 with the highest plasma uniformity as a result of the experiment.

The strength of the surface magnetic field of the permanent magnet is 3000 gauss. The strength of the magnetic field decreases toward the center of the reaction chamber 1 and toward the center between the magnets. In general, a strong magnetic field on the substrate has been reported to have a difficulty in obtaining the process uniformity, in the case of the present invention it can be seen that the strength of the magnetic field on the substrate is weak.

FIG. 3 (b) is a graph showing the change and distribution of the strength of the magnetic field caused by the electromagnet provided outside the reaction chamber 1.

As shown, the strength of the magnetic field represents a vertical magnetic field that increases linearly from about 15 gauss to 77 gauss when the current value is applied from 10A to 50A to the coil of each electromagnet. It can be seen that [{(B _max -B _min ) / (2 × average)} × 100] is maintained at less than 2% in the entire range of the 200 mm × 200 mm reaction chamber 1.

First, in the inductively coupled plasma apparatus according to the present invention, the electromagnet 3 installed outside the reaction chamber 1 is not applied to exclude the electromagnet 3 and is permanently installed on the inner wall of the reaction chamber 1. The influence on the plasma uniformity by the magnet 6 will be described. For this purpose, the ion saturation current of the plasma was measured using an electrostatic probe ESP (electrostatic probe) 4.

4 (a) shows the radius of the reaction chamber 1 at 1.5 cm above the center of the substrate when the permanent magnet 6 is installed inside the reaction chamber 1 using the electrostatic probe 4 and when not. It is a graph measuring ion saturation current along the direction. However, at this time, the DC voltage applied to the electrostatic probe 4 was -60V, the plasma pressure was Ar 5 mTorr, and the RF source power applied to the plasma was 600W.

As shown, it can be seen that the ion saturation current is higher when the permanent magnet 6 is installed inside the reaction chamber 1 to apply the magnetic field than when the magnetic field is not applied. In the plasma uniformity measured from the center of the reaction chamber 1 in the radial direction, the uniformity of the type 1, 3, 4 was shown to be worse than that of the non-magnetic field, but the other type did not. It can be seen that the improvement compared to the case. In particular, Type 4 showed the best uniformity among these various types of permanent magnets. For type 1 (distance between magnet center and center: 5.6 cm), the type 4 (distance between magnet center and center: 2.8 cm) and magnetic field are the same, but in the arrangement, rather than the effect of trapping free electrons in the plasma, Due to a decrease in plasma uniformity due to an increase in the loss point toward the reaction chamber 1, the type 3 (intensity of the magnetic surface magnetic field: about 4300 gauss) in the type 1 (intensity of the magnetic surface magnetic field: about 3000 gauss) It is estimated that the plasma uniformity decreases due to the penetration of a strong magnetic field into the reaction chamber 1 due to the intensity of the surface magnetic field about 1.5 times as strong as the

Therefore, it can be seen that by applying an appropriate magnetic field in consideration of the strength and arrangement of the magnetic field to the inside of the reaction chamber 1, it is possible to reduce the electron loss to the inner wall of the reaction chamber 1 and generate a more uniform plasma.

FIG. 5 shows the ion density of the Ar plasma measured using the electrostatic probe 4 under the same conditions in order to compare the permanent magnet types 2 and 4 with the best plasma uniformity with those without applying a magnetic field inside the reaction chamber 1. to be. At this time, the DC voltage applied to the electrostatic probe 4 was -60V, the pressure as the process variable was Ar 5 mTorr, and the RF source power applied to the plasma was 600W.

As shown, the ion density of the plasma has a higher ion density than in the case where no magnetic field is applied to the case where the permanent magnet 6 is installed inside the reaction chamber 1 and the magnetic field is applied, as in the case of the ion saturation current. appear.

FIG. 6 (a) is a graph showing the ion density according to the radial distance from the center of the substrate, measured using the electrostatic probe 4 according to the Ar pressure for the case where no permanent magnet is attached. b) is a graph showing the ion density measured in the same manner as in FIG. 6 (a) for the permanent magnet type 4 showing the best plasma uniformity in the reaction chamber 1. However, at this time, the voltage applied to the electrostatic probe 4 is -60V to 60V, the RF source power is 600W as the process conditions, the pressure is changed to 2mTorr, 5mTorr, and 10mTorr and the reaction chamber (1) in the radial direction from the center of the substrate Measured at 1 cm intervals to the inner wall.

As shown, both the plasma density and the uniformity increased compared to the case where the permanent magnet was disposed in the reaction chamber 1, and the uniformity of the ion density improved as the pressure was lowered regardless of the presence or absence of the magnet. It can be seen. This is because the mean free path of the ions increases due to the lower pressure, so that the diffusion coefficient in the radial direction from the center of the reaction chamber 1 increases. In the case where a permanent magnet is provided inside the reaction chamber 1, the uniformity of plasma density [{(n _max -n _min ) / (2 x average)} x 100] at 2 mTorr is 200 mm x 200 mm reaction chamber 1 At 5.9%. Therefore, it is assumed that the uniformity is further increased by lowering the process pressure.

7 (a) and 7 (b) show the uniformity of ion density measured at radial intervals of 1 cm at one point around the center of the reaction chamber 1 and 6 cm in the radial direction from the center in the case of the permanent magnet type 4 The graph shown. However, measurements were made at 600W RF source power and 5mTorr and 2mTorr process pressure. The uniformity of the ion density in the case of disposing the magnet in the reaction chamber 1 and in the case of the non-reaction chamber and at all the process pressures was 2.8%, which was slightly better than the center.

Hereinafter, in the inductively coupled plasma apparatus according to the present invention, the effect of the electromagnet 3 disposed outside the reaction chamber 1 on the plasma will be examined.

8 shows the Ar ion density of the plasma according to the change in the magnetic field by the electromagnet 3 disposed outside the reaction chamber 1 as to whether the permanent magnet 6 fitted inside the reaction chamber 1 is disposed. Indicates a change. Here, the RF source power is 600W, the process pressure is 5mTorr and 10mTorr. As shown, as the intensity of the magnetic field by the electromagnet 3 increases, the ion density tends to gradually increase regardless of the presence or absence of the permanent magnet 6 inside the reaction chamber 1. The rapid increase in ion density estimated by helical excitation at magnetic field location was observed.

9 (a), (b) and (c) are graphs showing the uniformity of the plasma density, the electron temperature, and the plasma potential according to the presence or absence of the electromagnet outside the reaction chamber 1 in the permanent magnet type 4. FIG. Each value was measured at 1cm interval from the center of the substrate to the inner wall of the reaction chamber (1). At this time, the voltage applied to the electrostatic probe (4) was -60V to 60V, the RF source power was 600W and the process pressure was 5mTorr. The magnetic field of the applied electromagnet 3 is 15 gauss and 20 gauss.

As shown, the ion density of the combination of the electromagnet 3 and the permanent magnet 6 was 3.12 × 10 ¹¹ cm ^-3 , and the uniformity of the plasma was slightly reduced, but the ion of the permanent magnet 6 alone was used. It was found that the density was increased to 2.42 × 10 ¹¹ cm ⁻³ . The uniformity of the plasma in the 200mm × 200mm reaction chamber 1 was reduced from 6.9% to 9% when the magnetic field was applied by installing the electromagnet 3 outside the reaction chamber 1. In addition, when the electromagnet 3 was installed outside the reaction chamber 1 in the state in which the permanent magnet was not installed inside the reaction chamber 1, the uniformity was reduced from 10% to 12.5%.

10 (a) and 10 (b) show the results of measuring the plasma potential and the temperature change of electrons when a magnetic field is applied by installing both the permanent magnet 6 inside the reaction chamber 1 and the electromagnet 3 outside. Is a graph.

Plasma potential was measured in the radial direction from the center of the substrate to the inner wall of the reaction chamber 1, and did not show a large change. As shown, the permanent magnet (6) or the electromagnet 3 only applied the magnetic field to the permanent magnet ( 6) and the electromagnet (3) were installed to show the lowest plasma potential when the magnetic field was applied. The temperature of the electron was also lower than that of the plasma potential when both the permanent magnet 6 and the electromagnet 3 were installed and the magnetic field was applied than when the magnetic field was applied only with the permanent magnet 6 or the electromagnet 3.

Therefore, as can be seen from the above experimental results, the effect of the permanent magnet type 4 on the uniformity and density of the plasma was analyzed while varying the intensity and arrangement of the permanent magnet 6 in the inductively coupled plasma apparatus. Compared to the case where the permanent magnet 6 was not installed and the magnetic field was not applied, the plasma uniformity was excellent in the center and the periphery of the reaction chamber 1. That is, the plasma uniformity from the center of the 210 mm x 210 mm reaction chamber 1 to the point of 1 cm from the inner wall of the reaction chamber 1 was measured. A permanent magnet 6 was installed at Ar source of 2 mTorr and RF source power of 600 W. In 10% of cases, the uniformity was improved to 5.9% when the fitted permanent magnet 6 was installed (permanent magnet type 4).

In addition, when a magnetic field was applied to the reaction chamber 1 by installing the electromagnet 3, the uniformity of the plasma was slightly reduced regardless of the presence or absence of the permanent magnet 6 (about 1.2% at 5 mTorr, 600 W). It can be seen that the density of the plasma is greatly improved by using. In addition, the use of permanent magnets (6) slightly reduced the plasma potential and electron density, and the combination of permanent magnets (6) and electromagnets (3) showed the lowest plasma potential (34V _p ) and electron temperature (3eV). .

Meanwhile, in order to clarify the etching characteristics of the inductively coupled plasma apparatus according to the present invention, etching of polysilicon was performed. Ar gas was used as the plasma gas in the reaction chamber 1, and C ₂ F ₆ , CHF ₃ , C ₄ F ₈ , and H ₂ gas were used as the gas for etching. In order to generate an inductively coupled plasma, an RF source power of 13,56 MHz was applied to the induction coil (2). Meanwhile, in order to generate a bias voltage, a separate 13.56 MHz RF power was applied to the wafer side as shown.

The silicon wafer used for etching was deposited with a silicon oxide film at a thickness of 1000 후 and then polycrystalline silicon was deposited at a thickness of 2 μm, and a photoresist (PR) having a thickness of 2.5 μm was patterned. Here, a photoresist is a photosensitive resin having a characteristic of changing its internal structure when exposed to various forms of energy such as light, radiation, and heat, and is a polymer that plays a role of changing a structure in response to energy, and a transporting role of the polymer. It has a solvent, and a sensitizer, which controls the chemical reaction of the multiplex, as basic constituents. In the semiconductor manufacturing process, the photoresist is used to form a predetermined pattern, thereby facilitating etching to selectively remove a predetermined film (an oxide film in this embodiment).

11 shows a permanent magnet 6 inside the reaction chamber 1 when a permanent magnet 6 is installed inside the reaction chamber 1 and an electromagnet 3 is installed outside the reaction chamber 1 to simultaneously apply a magnetic field. If the electromagnet 3 is not installed outside the reaction chamber 1, the electromagnet 3 is installed only outside the reaction chamber 1 without installing the permanent magnet 6 inside the reaction chamber 1. In this case, and in the case where the permanent magnet 6 and the electromagnet 3 are not provided inside or outside the reaction chamber 1, it is a graph showing the etching rate of the polycrystalline silicon measured every 2 cm in the radial direction from the center of the silicon wafer. Here, the permanent magnet 6 installed inside the reaction chamber 1 is type 4.

As shown, in the case of installing a permanent magnet (6) or electromagnet (3) inside or outside the reaction chamber (1) to apply a magnetic field to the plasma in the reaction chamber (1) when no magnet is installed at all It is easy to see that the etching rate is high. Moreover, the etching rate was higher when the electromagnet 3 was installed outside the reaction chamber 1 than when the permanent magnet 6 was installed inside the reaction chamber 1. The fastest etching rate was obtained when the permanent magnet 6 and the electromagnet 3 were installed inside and outside the reaction chamber 1, respectively. However, the uniformity of speed in the radial direction at the center of the silicon wafer was best when the permanent magnet 6 was installed inside the reaction chamber 1.

A radical means a molecule such as fluorine or chlorine that is excited by absorbing energy or an atom whose molecular bond is broken, and unlike ions, it does not have electricity, but is highly unstable and highly reactive with other materials. Therefore, the etching rate depends mainly on the concentration of reactive ions and radicals in the plasma.

12 shows a permanent magnet 6 inside the reaction chamber 1 and an electromagnet (20 gauss) 3 installed outside the reaction chamber 1 to simultaneously apply a magnetic field, thereby permanently inside the reaction chamber 1. When the magnet 6 is installed and the electromagnet 3 is not installed outside the reaction chamber 1, the electromagnet 20 may be installed only outside the reaction chamber 1 without installing the permanent magnet 6 inside the reaction chamber 1. When the Gaussian (3) is installed and the permanent magnet (6) and the electromagnet (3) are not provided inside or outside the reaction chamber (1), the concentration of Cl radicals measured with increasing RF source power is shown. It is a graph.

As shown, increasing the RF source power increases the energy in the plasma, thereby activating the collision reaction of electrons and increasing the number of radicals. Therefore, in all cases, increasing the RF source power increases the concentration of radicals. However, in the case where a permanent magnet 6 or an electromagnet 3 is installed inside or outside the reaction chamber 1 to apply a magnetic field to the plasma in the reaction chamber 1, Cl radicals are compared with the case where no magnet is installed. The concentration was higher. Furthermore, the Cl radical concentration was higher when the electromagnet 3 was installed outside the reaction chamber 1 than when the permanent magnet 6 was installed inside the reaction chamber 1. The highest Cl radical concentrations were obtained when permanent magnets 6 and electromagnets 3 were installed inside and outside the reaction chamber 1, respectively.

As described above, the change in the concentration of the Cl radical supports the cause of the increase in the etching rate measured previously.

In the above-described embodiment according to the present invention, 8 pairs or 14 pairs of permanent magnets are disposed inside the reaction chamber 1 and four electromagnets are disposed outside the reaction chamber 1 to strengthen the magnetic field in the reaction chamber 1. However, the number, size, and magnetic force of permanent magnets can be changed in various ways according to the requirements of the process to be performed, and of course, interchangeable permanent magnets and electromagnets can be used.

As described above, according to the present invention, an inductively coupled plasma apparatus capable of obtaining high uniformity, density and etching rate of plasma is provided.

Claims (3)

In an inductively coupled plasma device, A reaction chamber having a rectangular cross section for receiving at least one specimen for a predetermined treatment by plasma; Inducing means for providing RF source power in the reaction chamber to generate a plasma in the reaction chamber; And a magnetic field generating means provided inside said reaction chamber for providing a magnetic field for confining said plasma in said reaction chamber. The method of claim 1, The magnetic field generating means installed inside the reaction chamber is at least one pair of permanent magnets in which the N pole and the S pole are arranged at equal intervals. The method according to claim 1 or 2, Inductively coupled plasma apparatus further comprises an electromagnet provided outside the reaction chamber.