JP3017021U - Inductively coupled plasma generation coil - Google Patents

Abstract

(57) [Abstract] [Purpose] A coil for inductively coupled plasma generation that does not make a plasma generator large and does not make discharge breakdown difficult, and that can easily prevent generation of a quasi-stationary electric field in a processing container. provide. [Structure] A processing container 20 comprising a cylindrical lower portion 20a and a hemispherical upper portion 20b connected to the upper opening end of the lower portion is spirally wound from the upper portion to the lower portion and is parallel to each other. The coil 23 is an inductively coupled plasma generation coil having a plurality of connected coil portions 23a and 23b, and a high frequency current is supplied from a high frequency power source 25 to generate high density plasma in the processing container.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an inductively coupled plasma generating coil used for generating plasma in a plasma generating device used in semiconductor or LCD technology such as etching or film formation.

Generally, the following two excitation methods are known as methods for generating plasma using high frequencies in the short wave band. That is, the first method is a capacitive coupling method in which a high-frequency voltage is applied between a pair of parallel metal plates arranged in the processing container to generate plasma between these metal plates. Is. The second method is a method called an inductive coupling type in which a coil is wound around the processing container and a high frequency current is passed through the coil to generate a spiral electric field in the processing container to generate plasma. Is. In particular, the second method attracts attention because it can generate high-density plasma, and an example of a plasma generator adopting this method has a configuration shown in FIG. In this figure, reference numeral 10 denotes a cylindrical processing container in which a processing gas serving as a plasma source is supplied while the inside is exhausted and a substrate to be processed such as a semiconductor wafer or a glass plate is housed therein. It is made of an electrically insulating material such as quartz or alumina that is heat resistant. A high frequency coil 11 is wound around the outer circumference of the processing container 10, and a high frequency power supply 12 including a matching unit is connected between both ends of the coil 11. Then, the high-frequency current from the high-frequency power source 12 causes the coil 11 to generate a spiral electric field in the processing container 10 to generate plasma of the processing gas supplied to the processing container 10. In the figure, a symbol Eqs showing a dotted line indicates a quasi-stationary electric field generated between the coil wires.

[0003]

[Problems to be solved by the device]

 The quasi-stationary electric field Eqs is useful for starting discharge, but since it has a function of accelerating ions, the probability of accelerating ions during plasma generation and spattering the inner surface of the processing container to generate impurities Becomes higher. As a result, there are disadvantages that impurities in the processing plasma increase and accelerated ions collide with the processing substrate to cause internal damage (damage) to this substrate. For this reason, a technique has been developed in which an electrostatic shield is interposed between the coil and the inside of the processing container to prevent a quasi-stationary electric field from being generated inside the processing container. However, in this conventional technique, it is necessary to electrically insulate the electrostatic shield and the coil, which is troublesome to handle and the size of the entire device becomes large. Furthermore, if this electrostatic shielding is ensured, discharge breakdown becomes difficult and plasma cannot be generated.

Therefore, an object of the present invention is to generate an inductively coupled plasma that does not make the plasma generator large in size, does not make discharge breakdown difficult, and can easily prevent generation of a quasi-stationary electric field in the processing container. Is to provide a coil.

[0005]

[Means for Solving the Problems]

 The coil for inductively coupled plasma generation according to the present invention is used in an inductively coupled plasma generator for generating plasma by high frequency, and is connected in parallel with each other and is supplied with the high frequency current to generate a plurality of coils. Coil for generating inductively coupled plasma with parts.

[0006]

[Action]

 Assuming that the high frequency current supplied to the coil is I, its angular frequency is ω, and the inductance of the coil is L, a voltage V = | ωL · I | (1) is applied between the terminals of the coil. Therefore, assuming that the total length of this coil is Λ, the quasi-stationary electric field Eqs is approximately: Eqs = V / Λ = | ωL · I | / Λ (2) From this equation (2), it can be understood that in order to lower the quasi-stationary electric field Eqs, either ω, L, or I is made smaller or Λ is made longer. Therefore, each parameter is examined as follows.

1) If ω is reduced while keeping other conditions constant, the ions are easily accelerated, which is contrary to the objective. 2) Reducing I lowers the vortex electric field required to generate high-density plasma, which defeats the purpose.

3) Increasing Λ is contrary to the purpose because it increases the inductance L of the coil. Therefore, in the present invention, by reducing the inductance L, the coils are connected in parallel to each other so as to reduce the quasi-stationary electric field Eqs without defeating the purpose, and the coils are formed by a plurality of coil portions for generating the above high frequency. ing.

[0009]

【Example】

 Hereinafter, an inductively coupled plasma generating coil according to an embodiment of the present invention will be described with reference to the accompanying drawings together with a plasma generating apparatus using the same. As shown in FIG. 1, this plasma generator is composed of a cylindrical lower portion 20a and a hemispherical upper portion 20b connected to the upper open end of the lower portion 20a. Processing container 20 formed of the electric insulator of FIG. A susceptor 21 that supports a substrate W to be processed, such as a semiconductor wafer, is fixed to the lower portion of the processing container 20. Although not shown, the susceptor 21 has a heating temperature control unit for maintaining the target substrate W at a desired temperature and a unit for applying a predetermined voltage to the target substrate W, as is known.

A gas supply port 22 for introducing a processing gas into the processing container 20 is provided on the outer peripheral wall of the processing container 20, and the inside of the processing container 20 is evacuated, though not shown, on the bottom wall. In addition, an exhaust port for exhausting the processing gas is provided. On the outer peripheral surface of the processing container 20, a spiral coil 23 is wound from a hemispherical upper portion 20a to a cylindrical lower portion 21b as shown in the drawing. The coil 23 has one end located substantially at the center of the hemispherical upper part 20a and the other end located in the middle of the cylindrical lower part 20b. The coil 23 is composed of a first coil portion 23a whose cross section is indicated by a black circle in FIG. 1 and a second coil portion 23b whose cross section is indicated by a white circle. The first coil portion 23a and the second coil portion 23b are wound around the processing container 20 with a certain distance from each other. Both ends of the coil portions 23a and 23b are connected by a common connection terminal 24a, and thus the coil portions 23a and 23b are connected in parallel to the connection terminal 24a. A high frequency power supply 25 including a matching unit is connected between the connection terminals 24a by a connection line 24. Thus, the high-frequency current from the high-frequency power source 25 causes the coil 23 to generate a spiral electric field in the processing container 20 and generate plasma of the processing gas supplied to the processing container 20. At this time, as described above, since both coil portions 23a and 23b are connected in parallel to the power supply 25, the inductance of this coil 23 can be lowered, and the quasi-stationary electric field can be compensated for discharge breakdown. It is possible to generate a high-density plasma by reducing the parameters of each material to the minimum value.

Next, the result of an ashing test for etching the photoresist applied to the semiconductor wafer by generating oxygen plasma using the inductively coupled plasma generator having the above-described configuration will be described below.

The processing container 20 has an inner diameter of about 300 mm, and the inductance of the coil 23 is about 1/100 of that of the closely wound coil. Oxygen gas was supplied as the processing gas so that the pressure inside the processing container 20 was 8 Pa, and a high-frequency current of 1 kw at 13.56 MHz was passed through the coil 23. As a result, plasma having an electron temperature of 5 eV and a density of 2 × 10 ¹¹ cm ⁻³ could be generated, and an etching rate of the photoresist on the semiconductor wafer W was 6 μm · min ⁻¹ . The uniformity of the charged particle density on the surface of the semiconductor wafer was + 2%. It should be understood that such good uniformity of the charged particle density means that damage to the semiconductor wafer is extremely small.

In the above embodiment, the case where the coil is composed of two coil parts connected in parallel with each other has been described, but the number of coil parts is not limited to two and may be any number. Any number is acceptable. For example, as shown in FIG. 3, the coil may be composed of four coil portions 23a, 23b, 23c and 23d connected in parallel with each other. Even in this case, the coil portions 23a, 23b, 23c and 23d are connected to the connection terminals 24a at both ends, and the high frequency power supply 25 including the matching unit connected between the connection terminals 24a by the connection line 24 supplies a high frequency current. Can be supplied to generate high density plasma.

In the above-mentioned embodiment, the case where the coil of the present invention is applied to the processing container having an upper portion having a hemispherical shape has been described, but the shape of the processing container is not limited to this, and for example, the upper wall is flat. Anything is fine. Further, in this case, the coil is not limited to the spiral coil wound around the outer circumference of the processing container, and may be, for example, a flat spiral coil disposed on the upper wall, or both of them. The combination of

[0015]

[Effect of device]

 According to the above inductively coupled plasma generating coil of the present application, the plasma generator does not become large in size, the discharge breakdown is not made difficult, and the quasi-stationary electric field can be easily prevented from being generated in the processing container. Can generate plasma.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a plasma generator using an inductively coupled plasma generating coil according to an embodiment of the present invention.

FIG. 2 is a side view schematically showing a modified example of the inductively coupled plasma generation coil shown in FIG.

FIG. 3 is a schematic cross-sectional view of a conventional plasma generator for explaining the device.

[Explanation of symbols]

20 ... Processing container, 21 ... Susceptor, 23 ... Coil, 23
a, 23b ... Coil portion, 24a ... Connection terminal, 25 ... High frequency power source, W ... Substrate to be processed (semiconductor wafer).

Claims (2)

[Scope of utility model registration request] 1. An inductively coupled plasma generator for use in an inductively coupled plasma generator for generating plasma by high frequency, comprising: a plurality of coil units connected in parallel with each other to generate plasma by being supplied with the high frequency current. Coil. 2. A spiral coil wound from an upper portion to a lower portion on an outer peripheral surface of a processing container having a cylindrical lower portion and a hemispherical upper portion connected to an upper opening end of the lower portion. A coil for inductively coupled plasma generation according to item 1.