KR100404723B1 - Device for Generating Inductively Coupled Plasma with Lower Aspect Ratio - Google Patents

Abstract

The present invention relates to an ICP-type plasma generator having a low aspect ratio, and has a low electron temperature and a small volume of a chamber so as to be suitable for etching an oxide film of a semiconductor. The outer and central portions of the chamber to achieve a uniform plasma density, in an embodiment of the present invention to maintain the gas inlet 11 and the inside to supply a vacuum to the reaction gas and to discharge the reaction gas when the reaction is complete The chamber 10 is provided with a vacuum pump 12 and a gas discharge port 13 for the purpose, a chuck 20 for placing the workpiece within the chamber 10, and is installed on the upper portion of the chamber 10 In an inductively coupled plasma generator having an antenna 30 to which power is applied, the antenna 30 is capable of high frequency discharge and has a low impedance so as to secure a low electron temperature. Antennas are used, and each antenna 32,34 is connected to the powered end P of each antenna at the center of the virtual circle formed by the antennas 32,34 so that the plasma density distribution can ensure symmetry with respect to the rotational direction. The ground ends G of the other ends are arranged to be in mutually symmetrical positions, and each of the antennas 32 and 34 is formed to be twisted to each other in a spiral shape, and the powered end P of each antenna is located far from the chamber 10. For example, the ground end G may be located near the chamber 10 to compensate for the plasma density drop due to ion loss on the powered end side.

Description

Device for Generating Inductively Coupled Plasma with Lower Aspect Ratio

The present invention relates to an inductively coupled plasma generator having a low aspect ratio. Particularly, a low electron temperature and a small volume of a chamber can be secured to achieve high selectivity, which is necessary for plasma oxide film etching. The density distribution of is designed to precisely process large-diameter semiconductors by rotating symmetry and uniformizing the density distribution at the outside and center of the chamber.

Plasma is generated in the field where fine patterns such as semiconductor wafers and flat panel displays are formed to perform various surface treatment processes such as dry etching, chemical vapor deposition, and sputtering. Recently, in order to achieve cost reduction and throughput improvement, The size of a wafer for a device or a substrate for a flat panel display tends to be larger, for example, 300 mm or more. As a result, the size of a plasma generator for processing a large wafer or a substrate increases. Such plasma generators include inductively coupled plasma generators and capacitively coupled plasma generators. In addition, a method of applying a magnetic field to these basic plasma generators has also been developed.

Inductively coupled plasma generators have a higher density of plasma than capacitively coupled plasmas, but many additional factors are required to improve uniformity. For example, a thicker dielectric is used or a antenna is modified in a dome shape, but this has a limitation in that it is not only complicated in structure but also difficult to apply to processes such as oxide etching. That is, since oxide etching requires high selectivity in the process, the volume of the chamber is relatively large and the uniformity control of the plasma is a diffusion method, so that the residence time of the gas in the chamber is long. In addition, there is a limit to using the conventional inductively coupled plasma generator having a high electron temperature (Te).

The inductively coupled plasma generator described above briefly includes a chamber in which a plasma is generated, which maintains a gas inlet for supplying a reaction gas and the inside of the chamber under vacuum and discharges the reaction gas when the reaction is complete. It is equipped with a vacuum pump and a gas outlet for. In addition, a chuck for placing a sample such as a wafer or a glass substrate is provided inside the chamber, and an antenna to which a high frequency power source (usually 13.56 MHz) is connected is installed at the top of the chamber. An insulating plate is provided between the antenna and the chamber to reduce capacitive coupling between the antenna and the plasma to help transfer energy from the high frequency power supply to the plasma by inductive coupling.

In the inductively coupled plasma generator having such a structure, the inside of the chamber is initially evacuated to be evacuated by a vacuum pump, and then a reaction gas for generating plasma from the gas inlet is introduced and maintained at a required pressure. Subsequently, high frequency power is applied to the antenna from a high frequency power source.

In the conventional inductively coupled plasma generator, a single spiral antenna or a plurality of split-electrode antennas are used. As RF power is applied, a magnetic field that changes in time perpendicular to the plane of the antenna is formed. The changing magnetic field forms an induction electric field inside the chamber, and the induction electric field heats electrons to generate a plasma inductively coupled with the antenna. The electrons collide with the surrounding neutral gas particles to generate ions and radicals, which are used for plasma etching and deposition. In addition, when electric power is applied to the chuck from a separate high frequency power source, it is also possible to control the energy of ions incident on the sample.

However, in the antenna of the spiral structure, each induction coil constituting the antenna is connected in series, so the amount of current flowing in each induction coil becomes constant. In this case, it is difficult to control the distribution of the induction field. It is difficult to prevent the density of the plasma from being lowered at the center of the center and having a high density near the inner wall of the chamber. Therefore, it is extremely difficult to keep the density of the plasma uniform.

In addition, since each induction coil of the antenna is connected in series, the voltage drop caused by the antenna is increased, so the influence of capacitive coupling with the plasma is increased. Therefore, the power efficiency is lowered and it is also difficult to maintain the uniformity of the plasma.

Next, in the antenna of the three split electrode structure connected to three high frequency power sources having different phases from each other, the plasma density is high at the position close to each split electrode, and the plasma density is lower at the center of the chamber, thereby ensuring uniformity of the plasma. This is difficult, and it is particularly difficult to process a large area of the sample. In addition, since power must be used independently of each other, the cost increases, and there is a problem in that an independent impedance matching circuit must be used for each split electrode for impedance matching for efficient use of the power source.

On the other hand, in a parallel antenna structure in which a plurality of circular antennas are concentrically coupled in parallel, the uniformity of plasma in the rotational direction is inferior, that is, the middle portion of the antenna is relatively high, and the powered end and the ground of the antenna are relatively high. Plasma density at the ground end is relatively low. The cause of this plasma density distribution is asymmetrical with respect to the rotational direction because the high voltage is applied to the powered end of the antenna. This is because the plasma density drops, and the induced electric field does not occur because the current flow is zero between the looped antenna, that is, the powered end and the ground end. Plasma generation is weak and plasma density drop is generated. It was because, there is a problem in that a uniform machining of the work difficult by this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an inductively coupled plasma generator having a high plasma density so that an electron temperature is low and suitable for use in etching an oxide film of a semiconductor. The present invention provides an inductively coupled plasma generator having a low aspect ratio suitable for use in etching semiconductor oxide films by reducing the volume so that a high selectivity ratio can be ensured and the plasma density distribution in the rotational direction is symmetrical.

In order to achieve the above object, the present invention provides a chamber including a vacuum pump and a gas outlet for maintaining the gas inlet and the inside of the vacuum for supplying the reaction gas and discharging the reaction gas after the reaction, and the inside of the chamber An inductively coupled plasma generator having a chuck for placing a work piece and an antenna to which a high frequency power is applied to the upper side or the side of the chamber, wherein the antenna has a high frequency discharge in a range of 50 MHz to 100 MHz to ensure a low electron temperature. Parallel antennas with low impedance are possible, and each antenna is connected to the power end of each antenna and the ground end of the other end at the center of the virtual circle formed by the antenna so that the plasma density distribution can ensure symmetry with respect to the rotation direction. In a symmetrical position, and each antenna is spirally twisted together. In addition, the powered end of each antenna is located far from the chamber, and the ground end of each antenna is located close to the chamber to provide a plasma generator that can compensate for the plasma density decrease caused by ion loss on the powered end. do.

In the present invention, each antenna constituting the parallel antenna is formed in the form of a spiral twisted mutually in the same radius, the powered end of each antenna is located far from the chamber, that is, relative to the top or outside and the ground end is close to the chamber, It is located at the lower or inner side relative to the powered end, so that high voltage is applied to the powered end to minimize the drop in plasma density due to ion loss. The plasma density drop of one antenna due to the induction-free electric field at the disconnection between the ends is the same in the middle part of another antenna with the same radius and twisted in a double helix, where the plasma density is relatively higher than the power end side. Nested in In other words, by complementing the plasma density, it is possible to secure the symmetry of the plasma density distribution with respect to the rotation direction.

In the present invention, a parallel antenna on the outside of the upper chamber and a parallel antenna on the inside of the chamber may be further provided to generate a uniform plasma density over the entire area of the chamber.

In the present invention, the parallel antenna has two antennas symmetrically crossed at 180 ° and twisted in a double spiral shape, three antennas symmetrically crossed at 120 ° and triple spiral twisted shape, and four antennas crossed at 90 °. It can be twisted in a middle spiral shape, and in order to realize a lower aspect ratio, a larger number of antennas can be combined in parallel and crossed to a center to form a twisted multiple with each other.

In the present invention, in order to evenly distribute the plasma density at the outside and the center of the chamber may be provided with a parallel antenna on the outside of the chamber and a parallel antenna on the inside, the current applied to the parallel antenna on the outside and the current applied to the parallel antenna inside. It may be further provided with a means for matching similarly, and the number of crossings of the inner parallel antenna and the number of crossings of the outer parallel antenna can be different from each other to adjust the impedance of the antenna.

1 is a cross-sectional view of a plasma generating apparatus according to an embodiment of the present invention,

2 is an equivalent circuit diagram of a plasma generating apparatus according to an embodiment of the present invention;

3 is an antenna structure diagram of a plasma generator according to an embodiment of the present invention;

4 is a plan view of the antenna of the plasma generating apparatus according to an embodiment of the present invention;

FIG. 5 is a graph of density distribution in cross sections A-A and B-B of plasma generated by the antenna of the plasma generator shown in FIG. 4;

6 is an antenna structure diagram of a plasma generating apparatus according to another embodiment of the present invention;

7 is a plan view of the antenna shown in FIG. 6;

8 is a graph of the plasma density distribution on the cross section taken along the line C-C when the antenna of FIG. 7 is used;

FIG. 9 is an equivalent circuit diagram of a plasma generating apparatus according to still another embodiment of the present invention, illustrating a case where parallel antennas are respectively installed on an outer side and an inner side thereof,

10 is a structural diagram of an antenna according to another embodiment of the present invention,

11 is a cross-sectional view of the installation state of the antenna shown in FIG.

12 is a structural diagram of an antenna according to another embodiment of the present invention,

13 is a cross-sectional view of the installation state of the antenna shown in FIG.

14 is a cross-sectional view of a plasma generating apparatus according to another embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10 chamber 11: gas inlet

12 vacuum pump 13 gas outlet

14: impedance matching box 20: chuck

30: parallel antenna 31: bobbin

32, 34, 36: antenna 32a, 34a: middle part

40: outer antenna

Hereinafter, with reference to the accompanying drawings, embodiments that do not limit the present invention will be described in detail.

1 is a cross-sectional view of a plasma generating apparatus according to an embodiment of the present invention, Figure 2 is an equivalent circuit diagram of a plasma generating apparatus according to an embodiment of the present invention, Figure 3 is a plasma generation according to an embodiment of the present invention 4 is an antenna plan view of the apparatus, and FIG. 4 is a plan view of the antenna of the plasma generating apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the plasma generating apparatus of the present invention maintains the basic form of the inductively coupled plasma generating apparatus, that is, the gas inlet 11 and the inside of the vacuum for supplying the reaction gas, and the reaction gas when the reaction is complete. A chamber 10 having a vacuum pump 12 and a gas outlet 13 for discharging the gas, a chuck 20 for placing a work in the chamber 10, and an upper portion of the chamber 10. An antenna 30 to which high frequency power is applied is provided.

The antenna 30 is wound on a flat donut-shaped bobbin 31 having a constant thickness so that the two antennas 32 and 34 can be twisted.

In the figure, reference numeral 14 denotes an impedance matching box.

In the present invention, the antenna 30 installed on the chamber 10 is formed in the form of a parallel antenna, which is shown in FIGS. 3 and 4, wherein two antennas 32 and 34 are formed at the center of the virtual circle. In C), the power end P of each antenna 32 and 34 and the ground end G of the other end are placed in a symmetrical position, and each antenna 32 and 34 is formed in a twisted state in a double spiral form. The powered end P of each antenna 32, 34 is at a vertical position far from the chamber 10 and the ground end G of each antenna 32, 34 is at a vertical position close to the chamber 10 (see FIG. 1). I was in position.

In the present embodiment, the antennas 32 and 34 constituting the antenna 30 are twisted in a double spiral form and are positioned at the same radius, and the powered end P of each antenna 32 and 34 is a chamber 10. ) And the ground end (G) is located near the chamber (10), that is, relatively lower than the powered end (P), so that a high voltage is applied to the powered end (P). The loss of plasma density due to the loss is minimized, and the density drop due to the ion loss from the one end antenna (one of 32 and 34) to the powered end P and between the powered end P and the ground end G The plasma density drop of one antenna (one of 32,34) due to an induction-free electric field at the broken portion of the middle portion 34a, 32a of another antenna (one of 34,32) having the same radius and twisted in a double helix. plasma Is one to be superposed on the same position to secure the symmetry of the plasma density distribution with respect to the rotational direction by a complementary plasma density - relatively higher than the side part caused degrees powered end (P).

FIG. 5 graphically shows the density distribution of plasma generated by the antenna of the plasma generator shown in FIG. 4, with a solid line A-A across the powered end P of both antennas 32, 34. The plasma density distribution in the line cross section, and the dotted line shows the plasma density distribution in the cross section B-B perpendicular to the excitation. As shown in the graph of FIG. It can be seen that the distribution of the plasma density is symmetrical in the rotational direction with respect to the center of the chamber 10. The two antennas 32 and 34 cross each other symmetrically so that the plasma density in the rotational direction of one antenna is changed. The asymmetry of the distribution is complemented by the asymmetry of the plasma density distribution with respect to the rotation direction of the other antenna, so that the plasma density distribution is symmetrical. In addition, the plasma density distribution at the position traversing the powered ends of both antennas 32 and 34 and the plasma density distribution at the position perpendicular to the antenna are similar to each other and are symmetrical with respect to the rotation direction in the chamber 10. Able to know.

As can be seen in the plasma density distribution graph of FIG. 5, in the plasma generating apparatus of the present invention, in the conventional inductively coupled plasma generating apparatus, a plasma is disposed in a chamber in which a chuck for placing a workpiece such as a semiconductor is placed inside the chamber. In the present invention, the chamber height is increased by increasing the height of the chamber, and the volume of the chamber is increased and the plasma residence time is increased. Since the density of plasma is uniformly distributed even at relatively high position of the chamber, the height of the chamber can be reduced. Therefore, the volume of the chamber can be minimized and the plasma residence time is shortened. Conditions to secure selection costs In the inductively coupled plasma generator, a high frequency discharge of 50 MHz to 100 MHz is performed, which is relatively higher than that of a 13.56 MHz high frequency power supply, so that the electronic temperature can be lowered. Another condition is to be created.

FIG. 6 is an antenna structure diagram of a plasma generating apparatus according to another embodiment of the present invention, and FIG. 7 is a plan view of the antenna shown in FIG.

6 and 7, the three antennas 32, 34, and 36 have a power end P of each antenna 32, 34, and 36 at the center C of the virtual circle. The ground ends (G) of the other ends are symmetrically positioned at an angle of 120 ° to each other, and the antennas 32, 34, and 36 are twisted with each other in the form of a triple spiral, and each antenna (32, 34, 36). The powered end P of is located at the top, and the ground end G of each antenna 32, 34, 36 is located at the bottom.

In this embodiment, each of the antennas 32, 34, and 36 constituting the antenna 30 are twisted in a triple spiral shape and positioned at the same radius, and the powered end P of each of the antennas 32, 34, and 36 is in the same radius. Is located far away from the chamber 10, i.e., relatively high, and the ground end G is located near the chamber 10, i.e., relatively lower than the powered end P. Is applied to minimize the drop in plasma density due to ion loss, and the density drop due to ion loss on the powered end (P) side and no disconnection between the powered end (P) and the ground end (G). The plasma density drop of the antenna 32 on one side due to the induced electric field has the same radius and the middle portion 34a, 36a-plasma density of the other antennas 34, 36 twisted in a double helix is relatively higher than that of the powered end P.To part generated - it is superimposed on the same position to one so as to ensure the symmetry of the plasma density distribution with respect to the rotational direction by a complementary plasma density.

The antenna structure according to the present invention is not limited to the double spiral triple helical described above, and the four antennas are twisted into a quadratic spiral crossed at 90 ° to achieve a lower aspect ratio and more. A large number of antennas may be combined in parallel and crossed about the center to form multiple twists.

FIG. 8 is a graph illustrating a plasma distribution on a cross section taken along the line C-C when the triple spiral antenna of FIG. 7 is used. As can be seen in the graph of FIG. 8, the plasma density distribution at the position across the middle of the antenna at the powered end P and the ground end G of one antenna 32, 34, 36 is symmetrical. The symmetry of the plasma density distribution can be seen that the three antennas cross each other at an angle of 120 ° and appear almost the same in all rotation directions of the antenna.

In the plasma generator of the embodiment described with reference to FIGS. 1 to 8, one parallel antenna 30 is installed outside the upper portion of the chamber 10, and the center portion of the chamber 10 is closer to the outer portion of the chamber 10. In consideration of the low plasma density distribution of the parallel antenna 30 in the same structure as the outer parallel antenna 30, the parallel antenna 40 can be installed on the inner side concentrically with the outer parallel antenna 30. 9 is shown.

In the above-described embodiment of FIG. 9, the outer parallel antenna 30 and the inner parallel antenna 40 are provided so that the rotational symmetry of the plasma density distribution is achieved throughout the entire region of the chamber, and at the same time, the plasma at the outer and center of the chamber is The density distribution can be formed uniformly, and in the plasma generating apparatus of this embodiment, a means for matching the current applied to the parallel antenna 30 on the outside with the current applied to the parallel antenna 40 on the inside is further provided. In order to adjust the impedance of the antenna, the number of crossings of the inner parallel antennas and the number of crossings of the outer parallel antennas are different from each other. For example, in the outer parallel antennas, three antennas cross each other in a triple form. The parallel antenna may be of a form in which two antennas are crossed in two.

The plasma generating apparatus of the present invention described above has a high selectivity ratio to solve the problem that the high volume ratio of the chamber is large and the electron temperature is high in the inductively coupled plasma generating apparatus capable of relatively high density plasma generation. In order to ensure low electron temperature and chamber volume, high frequency discharge is possible and low impedance parallel antenna is used, but the plasma generation is twisted symmetrically so that the plasma density distribution is rotationally symmetric in the chamber. By manufacturing in the form, it is possible to secure a high selection ratio.

In the plasma generating apparatus of the present invention, the chamber volume should be minimized in order to shorten the time that the plasma remains in the chamber. In the conventional inductively coupled plasma generating apparatus, the volume depends on the uniformity control of the plasma by the diffusion method. Although the present invention had to be large, the present invention achieves a low aspect ratio even if the diffusion method is not symmetrical by the symmetrical parallel antenna structure in which the density distribution of the plasma is twisted. Since the outer periphery of the chamber and the center of the chamber form a uniform plasma distribution at the position where the workpiece is placed, even if the position of the workpiece is placed high, that is, the upper and lower distances of the chamber can be shortened, thereby minimizing the volume of the chamber. And antenna It is connected in parallel, so it is low-impedance high-frequency discharge it possible to lower the electron temperature will be obtained in a high selectivity to a request from the oxide etch of a semiconductor.

10 is a structural diagram of an antenna according to another embodiment of the present invention, Figure 11 is a cross-sectional view of the installation state of the antenna shown in FIG.

The antenna shown in FIG. 10 has a structure in which two antennas 32 and 34 are wound around a short tubular bobbin 31, and two antennas 32 and 34 coupled in parallel are formed of the bobbin 31. At the center C, the powered end P of each antenna 32 and 34 and the ground end G of the other end are in a symmetrical position, and each antenna 32 and 34 is wound in a twisted state in a double spiral form. The powered end P of each of the antennas 32 and 34 is located outside the bobbin 31, and the ground end G of each of the antennas 32 and 34 is located inside the bobbin 31. The high voltage is applied to the (P) side to minimize the drop of the plasma density due to the ion loss, and the density drop caused by the ion loss on the powered end (P) side and between the powered end (P) and the ground end (G). The plasma density drop of one antenna 32 due to the induction-free electric field at the broken portion is the same radius. The intermediate portions 34a and 36a of the other antennas 34 and 36 twisted in a high double-helical shape-the portions where the plasma density is generated relatively higher than the powered end P side-overlap in the same position to complement each other. It is to ensure the symmetry of the plasma density distribution with respect to the rotation direction.

The antenna 30 shown in FIG. 10 is simply changed in shape so as to exhibit the same function as the antenna shown in FIGS. 2 and 3 of the present specification. It is to be used in the generator, its operation is specifically mentioned in the first embodiment of the present invention, so repeated description is omitted.

12 is a structural diagram of an antenna according to another embodiment of the present invention, Figure 13 is a cross-sectional view of the installation state of the antenna shown in Figure 12, in this embodiment to install on the dome in the dome-shaped inductively coupled plasma generator The antennas 32 and 34 are wound around the conical bobbin 31 formed to be suitable, and its operation and effect are the same as in the first embodiment of the present invention.

FIG. 14 is a cross-sectional view of a plasma generating apparatus according to another embodiment of the present invention. In this embodiment, the antenna 30 of the present invention is shown in FIG. An example of installing the illustrated antenna is shown, and its operation is the same as in the description of FIGS. 10 and 11, and thus, a detailed description thereof will be omitted.

In addition, in the present invention, the antenna shown in FIGS. 10 to 14 shows a form in which two antennas are coupled in parallel, but the present invention is not limited thereto, and by using three or more antennas arranged in a symmetrical form. The density distribution of the induced plasma may have high symmetry with respect to the rotation direction.

As described above, the present invention improves the antenna structure of the inductively coupled plasma generator so that the electron temperature is low and the volume of the chamber is reduced so as to be suitable for etching the semiconductor oxide film, thereby ensuring high selectivity. By having the density distribution achieve rotational symmetry, it has a useful effect of precisely processing a large diameter semiconductor.

Claims (4)

A chamber having a gas inlet for supplying a reaction gas and a vacuum inside the chamber and having a vacuum pump and a gas outlet for discharging the reaction gas when the reaction is completed; a chuck for placing a work in the chamber; In the inductively coupled plasma generator having an antenna to which a high frequency power is applied to the upper part or the side part, The antenna 30 is capable of high frequency discharge to ensure a low electron temperature, and uses a low impedance parallel antenna, each antenna 32, 34 so that the plasma density distribution can ensure the symmetry of the rotation direction At the center of the virtual circle formed by the antennas 32 and 34, the power end P of each antenna and the ground end G of the other end are placed in symmetrical positions, and the antennas 32 and 34 are spirally aligned with each other. It is formed in a twisted state, and the power end P of each antenna is located far from the chamber 10, and the ground end G of each antenna is located close to the chamber 10, so as to prevent ion loss on the power end side. Inductively coupled plasma generator having a low aspect ratio, characterized in that to compensate for the decrease in plasma density. The method according to claim 1, The parallel antenna (30) is an inductively coupled plasma generator having a low aspect ratio, characterized in that three or more antennas are symmetrically crossed with respect to the center thereof and are twisted mutually. The method according to claim 1, Induction with a low aspect ratio, characterized in that the parallel antenna 30 is coupled in parallel with the parallel antenna 30 and the symmetrical twisted structure is installed in the upper portion of the chamber 10 is installed inside the chamber 10 is further provided. Combined plasma generator. The method according to claim 1, The antenna (32, 34) is inductively coupled plasma generator having a low aspect ratio, characterized in that the bobbin (31) is wound around the installation to maintain the twisted form.