Antenna device for generating inductively coupled plasma

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an antenna device used in a plasma generator for generating plasma, and more specifically, an inductively coupled type capable of generating plasma having a high density with a wide effective area capable of processing a large sample. The present invention relates to an antenna device for plasma generation.

【0002】

[Conventional technology]

In technical fields such as semiconductor wafers or flat plate display devices where fine patterns should be formed, plasma is generated to perform various surface treatment processes such as dry etching (etching), chemical vapor deposition, and sputtering. .. Recently, in order to reduce costs and improve the flow, there is a tendency for the size of semiconductor device wafers and flat plate display device substrates to be increased to, for example, 300 mm or more. The scale of plasma generators for processing large-scale wafers and substrates is also increasing.

【0003】

As a conventional plasma generation source, there is one that uses a plasma generation method using high frequency power such as a die method, a microwave method, and a radio wave method. On the contrary, according to the die method, it is difficult to control a high voltage and a high gas pressure is required, so that it is not suitable for processing a fine pattern. Furthermore, according to the Electron Cyclotron Resonance (ECR) method, which is a type of microwave method, there is an advantage that high-density plasma can be generated even under low pressure, but there is a disadvantage that it is difficult to form a uniform distribution of plasma. These disadvantages become even more pronounced as the scale of the plasma grows. As a result, according to the helicon wave method, which is a type of radio wave method also called inductively coupled method, the energy of the electric field and the magnetic field are combined and excited (excite). Therefore, a small-scale plasma can generate a high-density plasma having a uniform distribution, but when the scale of the plasma is still large, it has a disadvantage that the density distribution is not uniform.

【0004】

A normal inductively coupled plasma generator will be briefly described with reference to FIG. The plasma generator (10) includes a chamber (104) in which the plasma (118) is generated, and the chamber (104) is provided with a gas inlet (110) and a chamber for supplying a reaction gas. When the inside is kept in a vacuum and the reaction is completed, a vacuum pump (112) and a gas discharge port (114) for discharging the reaction gas are formed. Further, a chuck (108) for placing a sample (106) such as a chamber or a glass substrate is formed inside the chamber- (104), and a chuck (108) is formed on the upper part of the chamber- (104). An antenna (100) connected to a high frequency power supply (102) is installed. By installing an insulating plate (116) between the antenna (100) and the chamber- (104) to reduce the capacitive coupling between the antenna (100) and the plasma (118). , Energy from the high frequency power supply (102) helps transfer to the plasma (118) by inductive coupling.

【0005】

The plasma generator (10) having the above mechanism generates plasma as follows. That is, after the inside of the chamber- (104) is initially evacuated so as to be evacuated by the vacuum pump (112), a reaction gas for generating plasma is introduced from the gas inlet (110), which is necessary. It is held at a high pressure. Then, RF high frequency power of, for example, 13.56 MHz is applied to the antenna (100) from the high frequency power supply (102).

【0006】

Conventional plasma generators (10) include spiral antennas (200) or multiple (eg, three) split electrode antennas (202a, 202b and 202c), as shown in FIGS. 2 (a) and 2 (b). ) Was used. Therefore, as RF power is applied, a magnetic field that changes with time in the direction perpendicular to the plane formed by the antenna (100) is formed. Such a time-varying magnetic field forms an induced electrical field inside the chamber- (104), which heats the electrons and is inductively coupled to the antenna (100). Will occur. In this way, the electrons collide with the surrounding neutral gas particles to generate ions and radicals, which are used for plasma etching and vapor deposition. Further, by applying electric power to the chuck (108) from a separate high-frequency power source (not shown), it is possible to control the energy of ions incident on the sample (106).

【0007】

[Problems to be Solved by the Invention]

On the contrary, in the antenna (200) having a spiral structure as shown in FIG. 2 (a), since the windings constituting the antenna are connected in series, the current flowing in each winding The amount becomes constant. In such a case, it is difficult to adjust the distribution of the induced electric field, and the loss of ions and electrons in the inner wall of the chamber- (104) causes the central part of the plasma (118) to have a high density, and the chamber- (104) has a high density. It becomes difficult to prevent a decrease in plasma density in the portion near the inner wall. Therefore, it becomes extremely difficult to keep the density of the plasma (118) uniform.

【0008】

Furthermore, since each winding of the antenna (200) is connected in series, the voltage drop due to the antenna (200) increases, and the effect of capacitive coupling with the plasma (118) increases. To do. Therefore, the power efficiency is lowered and it becomes difficult to maintain the uniformity of the plasma.

【0009】

Next, as shown in FIG. 2 (b), in the antenna having three divided electrodes (202a, 202b and 202c) connected to three high-frequency power supplies (204a, 204b and 204c) having different phases, respectively. Since the plasma density is high near each of the split electrodes and the plasma density is low toward the center of the chamber- (104), it is difficult to ensure plasma uniformity, and it is particularly wide. There is significant difficulty in processing area samples. In addition, since each power supply must be operated independently, the cost increases, and in order to perform impedance matching for efficient use of the power supply, each divided electrode is unique. There was a problem that a simple impedance matching circuit should be used.

【0010】

(Purpose of the Invention) Therefore, the present invention has been made to solve the above-mentioned various problems, and the purpose of the present invention is an antenna for generating a large-scale plasma capable of processing a large-area sample. To provide the equipment.

【0011】

Another object of the present invention is to provide an antenna device for making the density distribution of plasma uniform.

【0012】

[Means for solving problems]

The present invention made to achieve the above object is an antenna device for a plasma generator for generating a large-scale plasma, in which a high-frequency power supply and a high-frequency power supply are supplied from the high-frequency power supply. It is characterized by including one antenna and a second antenna that is supplied with high-frequency power from the high-frequency power source and is connected in parallel to the first antenna, but maintains a resonance state with the first antenna. And.

【0013】

Further, in an antenna device for a plasma generator for generating a large-scale plasma, a high-frequency power supply, a first antenna to which high-frequency power is supplied from the high-frequency power supply, and the first antenna are connected in parallel. A first antenna set provided with a second antenna, a third antenna to which high-frequency power is supplied from the high-frequency power source, and a fourth antenna connected in parallel to the third antenna are provided. It includes a second antenna set connected in parallel to the first antenna set, and is characterized in that a resonance state is maintained between the first antenna and the second antenna.

【0014】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the attached drawings.

【0015】

First, referring to FIGS. 3 (a) and 4 (a), FIG. 3 (a) is a conceptual diagram of an antenna device according to an embodiment of the present invention, and FIG. 4 (a) is FIG. 3 (a). It is an equivalent circuit diagram of the antenna device in. As shown in the figure, the antenna device (100) of the present invention includes a plurality of antenna units (400a or 400b) connected in parallel with each other, and each of the antenna units (400a or 400b) has a variable load (400a or 400b). Includes 302a or 302b) and single-winding or double-winding antennas (300a or 300b), respectively. The antenna (300a or 300b) is displayed by the equivalent resistance (R1 or R2) and the equivalent inductance (L1 or L2), and the latency component is absorbed by the resonant variable capacitor (CR) or variable load capacitor (CL) and displayed. did.

【0016】

Further, the antenna device (100) is an impedance matching circuit (Impedance Matching Box) for impedance matching between the plurality of antenna units (400a or 400b) and a high frequency power supply (102). Includes IMB) (304). Here, the plurality of antenna units (400a and 400b) are kept in resonance with each other by a variable load, for example, a variable capacitor (CR, 302a), which is possessed by the antenna device (100) of the present invention. This is the most important feature. The resonance state of the antenna device (100) according to this embodiment will be described in detail below with reference to FIG. 4 (a).

【0017】

FIG. 4 (a) is an equivalent circuit diagram of the antenna device of FIG. 3 (a). That is, power is supplied through the impedance matching circuit (304) connected to the high frequency power supply (102), and the first variable load (302a) and the first antenna (300a) connected in series with the first variable load (302a) are included. The first antenna unit (400a) and the second antenna unit (400b) including the second variable load (302b) and the second antenna (300b) connected in series with it are connected in parallel with each other. ..

【0018】

Here, the magnitude of the first variable load (302a) so that the imaginary part of the equivalent impedance by the first antenna unit (400a) and the second antenna unit (400b) becomes 0 (zero). Can be adjusted. This can be easily achieved by those skilled in the art by, for example, adjusting its cavities using a variable capacitor (CR) as shown in the figure, so a detailed description thereof will be omitted. In such a resonance state, the magnitudes of the currents flowing inside the first antenna unit (400a) and the second antenna unit (400b) become the same as each other, and the first one located outside through the process. It is possible to increase the current of the antenna unit of.

【0019】

Next, in order for the energy from the high frequency power supply (102) to be transmitted to the first and second antenna units (400a and 400b) to the maximum extent, it is preferable to use a normal impedance matching method. That is, once the variable load inside the first and second antenna units (400a and 400b) is determined, the whole can be regarded as a fixed load, so that the impedance can be matched to the equivalent impedance. The dance matching circuit (304) can be determined. The impedance matching circuit (304) can be embodied by a method already known in the art, for example, a variable inductor- (L)._I) And variable capacitors (C_I) Can be used in a simple circuit connected in parallel.

【0020】

That is, the antenna device (100) of this embodiment determines the size of the variable load (302b) for adjusting the transmitted energy of the second antenna (300b) itself, and the first antenna (300a). The high-frequency power supply is obtained by determining the size of the resonant variable load (302a) so as to form a resonance state between the second antennas (300b) and then matching the impedance with the high-frequency power supply (102). Not only can the energy supplied from (102) be efficiently transferred to the plasma (118) in the chamber- (104), but the uniformity of the plasma corresponding to the position can be increased.

【0021】

Next, other examples of the present invention will be described with reference to FIGS. 3 (b) and 4 (b). As shown in the figure, the antenna device (100') of the present invention may include an arbitrary number of antenna units (410a, 410b or 410c) provided that the condition for maintaining the resonance state is maintained. it can. In the embodiment shown in the figure, a case where there are three antenna units is shown. Referring to the equivalent circuit diagram of FIG. 4 (b), each antenna unit (410a, 410b or 410c) contains a variable load (312a, 312b or 312c) within two of the antenna units (410b and 410c). By adjusting the size of the mounted variable load (312b or 312c), the current ratio flowing through the two antenna units (310b and 310c) can be adjusted, and the remaining one antenna unit (310a) is a circuit. It can be used to induce a resonance state within. In such an embodiment, the antenna unit (310a) in the resonant state forms the outer winding, and the remaining antenna units (310b and 310c) form the inner winding, thereby energizing the antenna device as a whole. The uniformity of the above can be easily improved. It should also be noted here that the variable load (312b or 312c) of the inner antenna units (410b and 410c) can be omitted in certain embodiments.

【0022】

Also, as mentioned above, impedance matching with the high frequency power supply (102') should be achieved in order to maximize the energy supplied to the entire antenna unit (410a, 410b and 410c). Because of the inductor-(L_I') And capacitors (C_IUse an impedance matching circuit (304') containing').

【0023】

The antenna device (100') according to this embodiment can efficiently form a larger-scale plasma in a uniform manner than in the case of the embodiment shown in FIG. 3 (a).

【0024】

Next, other examples of the present invention will be described with reference to FIGS. 5 and 6. In the embodiment shown in FIG. 5, one set of antenna units having the same configuration as the antenna units (400a and 400b) included in the antenna device (100) of FIG. 3A is further included. That is, referring to FIG. 6, which shows an equivalent circuit diagram of the antenna device (500) of FIG. 5, the antenna device (500) includes a first antenna unit (510a) and a second antenna unit (510b). Includes one antenna set (520a) and a second antenna set (520b) that includes a third antenna unit (510c) and a fourth antenna unit (510d). Each of the antenna units (510a, 510b, 510c or 510d) may include a variable load similar to that used in the other embodiments described above. In particular, a resonant state is maintained between the antenna units (510a and 510b or 510c and 510d) of each antenna set (520a or 520b), which is done by adjusting the magnitude of the resonant variable load (CR1 or CR2). Can be achieved. Also, energy transfer is maximized by the impedance matching circuit (504) connected between the entire antenna set (520a and 520b) and the high frequency power supply (102 ).

【0025】

In this embodiment, the case where the number of the antenna sets is two is illustrated, but in order to increase the scale of the plasma or control the uniformity more precisely, it is possible to install more antenna sets. As described in the above, the number of antenna units included in each antenna set is not limited to two. In particular, it should be noted that in the case of the antenna set located inside, it is possible to artificially prevent the resonance state from being maintained. This can be done in the case of achieving the goal of improving the uniformity of the plasma by providing less power to the plasma than the antenna set located on the outside, and on the antenna set on the outside. By maintaining the resonance state, it is possible to supply a larger amount of electric power.

【0026】

That is, with reference to FIG. 7, FIG. 7 shows an antenna device (600) containing two or more antenna sets containing the three antenna units used in the antenna device (100') of FIG. 3 (b). Has been done. Also in this embodiment, the resonance state of the antenna units, the energy strength of each antenna unit, the matching of the impedance with the high frequency power supply, and the like are the same as or similar to those described above.

【0027】

[Effect of the invention]

As described above, according to the present invention, the problem of impedance matching that occurs as the scale of the antenna device for generating plasma increases can be solved, and further, a resonance state is induced and specified in the antenna. Since the energy transmitted by the antenna can be selectively increased or decreased, the uniformity of the plasma can be significantly increased.

【0028】

Although the technical idea of the present invention has been specifically described with reference to the above embodiment, it should be noted that the above embodiment is for explaining it and not for limiting it. ..

[Simple explanation of drawings]

[Figure 1]

Schematic diagram of a conventional inductively coupled plasma generator [Figure 2]

Schematic diagram of a conventional inductively coupled plasma generating antenna device [Fig. 3]

Schematic of an inductively coupled plasma generating antenna device according to an embodiment of the present invention. [Fig. 4]

Equivalent circuit diagrams of the antenna devices shown in FIGS. 3 (a) and 3 (b), respectively. [Fig. 5]

Schematic diagram of an inductively coupled plasma generating antenna device according to another embodiment of the present invention. [Fig. 6]

It is an equivalent circuit diagram of the antenna device for inductively coupled plasma generation according to another Example of this invention.

[Fig. 7]

It is an equivalent circuit diagram of the antenna device for inductively coupled plasma generation according to another Example of this invention.

[Explanation of symbols]

100 ... antenna 102 ... High frequency power supply 104 ... Chamber- 106 ... sample 108 ... Chuck 110 ... gas inlet 112 ... Vacuum pump 114 ... Gas outlet 116 ... Insulation plate 118 ... Plasma