JPS60246599A - Method and device for generating homogeneous large capacity plasma of high density and low electron temperature - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to the generation of plasma from gaseous media of a nature that is used for a variety of purposes.

Several means are known for generating plasma from gaseous media.

For example, methods using continuous discharge or heat emitting filaments are known. These means cannot obtain a high-density, homogeneous, large-volume plasma. In addition, when heat-emitting filaments are used, such means generally cannot be used in conjunction with such reacting gaseous media.

It is also known that plasma is generated by high-frequency discharge.

The same disadvantages as mentioned above have to be attributed to such technical measures, except for the use of corrosive gaseous media that may be considered in that case. In addition, this method has the disadvantage of generating plasma with high electron temperatures.

Furthermore, this solution does not allow for independent parameters regarding plasma generation and its use.

It is also known to generate plasma using UHF waves. The resulting plasma has an electron temperature lower than that of the plasma obtained by radiofrequency excitation, but is not always homogeneous and bulky. However, this method makes the parameters of plasma generation and its use independent.

The generation of a plasma excited by heat-emitting filaments and spatially maintained by magnetic confinement K is also known. Such a method makes it possible to obtain a homogeneous large volume plasma of high density and low electron temperature by making the parameters of plasma generation independent from the parameters of its use.

However, such methods have considerable drawbacks, especially with regard to the reliability of the emitted filament and the contamination of the surrounding medium that it causes.Moreover, the thermal radiation of the filament does not support the stable development of plasma formation methods. temperature rise time associated with each developmental stage.

In addition, taking into account the presence of heat-releasing filaments, such a method cannot be used in the case of ionization of gaseous media of a reactive nature in conjunction with the substances that constitute the filaments.

It has also been proposed to generate a plasma excited by a heat-emitting filament maintained by electrostatic confinement. In addition to the above drawbacks, it should be noted that such methods cannot obtain a homogeneous large volume of plasma.

Conventionally known means are therefore available for a wide variety of applications of low electron temperature, high density, homogeneous large volume plasmas generated from gaseous media, reactive or otherwise, and whose generation parameters are independent of the parameters of their use. Unsatisfactory when availability is necessary for modern technology.

This is especially the case at relatively low cost or in areas where it is necessary to generate positive or negative ions when engraving, deposition or oxidation is carried out.

and <K, which is the case in the preferred application of the invention, which consists in the surface treatment of various substrates in the microelectronics industry. In such areas, it is necessary to be able to work with real precision, while using the lowest possible energy, for example on layers of small thickness in which anisotropic engravings are carried out with precision.

It is an object of the present invention to outperform the prior art by proposing a new method and a new device for generating a continuous homogeneous large volume plasma of high density and low electron temperature from a gaseous medium, reactive or otherwise. It consists in overcoming shortcomings.

Another object of the invention is to propose a new method and a new device for obtaining a plasma whose parameters governing its origination or generation are completely independent of those regarding the interaction between the plasma and its application. It's about doing.

To achieve the above object, the present invention continues the excitation of the gaseous medium within the enclosure up to UHF waves, maintains the plasma within the enclosure by at least multipole magnetic confinement, and provides 10 and 10 -1
) is characterized in that it uses a device adapted to maintain the absolute pressure between the two channels.

The invention also provides a tight enclosure connected to a pumping circuit and a gaseous medium supply circuit adapted to maintain a determined pressure, and at least a shell for multipole magnetic confinement. and,
The apparatus is characterized in that it comprises a UHF wave generator terminating in a device for excitation of a gaseous medium arranged opposite the window of the shell, and means for analyzing the plasma in the confinement shell.

The present invention will be more easily understood by reading the following description with reference to the accompanying drawings.

According to the method of the invention, generation of a homogeneous large volume plasma of high density and low electron temperature and in which the parameters controlling its generation or generation are independent of the parameters controlling its subsequent use is achieved within a tight enclosure. Introducing a gaseous medium of selected nature as a function of a defined subsequent use. This gaseous medium is, for example, approximately 10
-5 and about 10-1) liters (1 Torr = 133 Pascals).

When the gaseous medium is used, the pressure inside the enclosure is continuously introduced to fill the enclosure, from which the gaseous medium can be extracted by suitable pumping means.

Inside the enclosure, the gaseous medium is ionized via UHF waves delivered by a suitable generator trap. The UHF waves used are in the range 1 to 10 GHz and preferably around 25 GHz.

The plasma generated within the enclosure by UHP waves is preferably at least magnetically confined in a passive manner by a multipolar shell formed inside the enclosure and in communication with means for guiding and pumping the gaseous fluid. It will be done.

In this way, large volumes, for example several hundred liters, can be occupied which are completely homogeneous, without internal magnetic fields and defined by a multipolar magnetic confinement shell. It becomes possible to generate with excellent reliability a high-density plasma of about IQ" an-3 with electron temperatures slightly different from electron volts.

Due to the absence of a heat-releasing filament, this method makes it possible to ionize a reactive gaseous medium that is reactive in a more general sense, ie has reactive properties in relation to the substances that are acted upon by this plasma.

It is thus possible to use such a plasma to act on the surfaces of various substrates, which can be exposed over small or large areas within a confinement shell defined inside the enclosure.

This advantage has applications in microelectronics, since it allows deposition, oxidation or engraving to be carried out with precision, such as the high density of the plasma, the volumetric volume, the homogeneity or isotropy and the independence of the plasma generation parameters. It is particularly highly evaluated in the case of While these treatments can be carried out over large areas, they use only low levels of energy and, in the case of engraving, are anisotropic in the direction of the displacement magnetic field imparted by the application of appropriate potentials to the substrate. In other application areas, the confinement shell is closed over at least part of its local area by an extraction grid that allows a large amount of positive or negative ions to be generated from the generated plasma. The target ions may then be condensed and accelerated as a function of the possible application.

According to the method of the invention, it may be provided to divide the confinement shell by a magnetic filter, one for plasma generation and one for use where said plasma has a uniformly low electron temperature.

In some cases, the method may also include placing a multipolar magnetic confinement shell outside the enclosure.

If there is a confinement shell within the enclosure, it may be provided to add electrostatic confinement means which reduce the shim temperature by a factor of approximately 2 or at high pressures by approximately 5. makes it possible to increase the density of the plasma by a factor of .

Referring to the drawings, FIG. 1 schematically shows a facility or apparatus for generating a homogeneous large volume plasma of high density and low electron temperature.

The installation preferably comprises an enclosure 1 made of non-magnetic material, said enclosure 1 comprising a storage tank 5.
is connected by a pipe 2 to means 5 for distributing a suitable gaseous fluid delivered by a valve 4. The enclosure is also connected by a pipe B to pumping means 7 consisting of a pump 8 and a flow regulating valve 9.

In order to create a plasma within the enclosure 1, the gaseous fluid is maintained at an absolute pressure of approximately 10 to 10 -1) -L. For this purpose, for example, pumping means are used to create a relative vacuum, and the means 3 are adjusted so that the desired absolute pressure appears.

Enclosure 1 is connected to earth 10 by suitable means.

The internal volume defined by the enclosure 1 can be accessed, for example, via an opening 12 made in the bottom wall 1a.

The opening 12 is closed in this case by a removable panel 12a which supports by means of insulation 16 a substrate carrier 14 which can be polarized in a DC or AC manner by a voltage source 15 and thermostatically regulated.

The internal volume 11 of the enclosure 1 houses a magnetic confinement shell 16 constituted by a multipolar cage maintained by an insulating support 17. This multipolar cage can be connected to ground or can be polarized via a pressure source 18. The substrate carrier 14 is mounted so as to be located within the internal volume 19 of the magnetic confinement shell.

The enclosure 1 is associated by suitable means 21 with a generator 20 of UHF waves which excites the gaseous medium so as to generate a plasma which diffuses into the shell 16. Means 21
is therefore arranged opposite the window 21a formed in the shell 16. The means 22 for analyzing the generated plasma are adapted to penetrate the enclosure 1 in the same way as the shell 16. These means 22 are constituted by Langmuir probes, for example.

In the illustrated example, the multipole cage is configured as shown in FIG. The cage consists of an armature 26 supporting a bar 24 of permanent magnetic properties.

The armature 23 is formed to maintain the bars 24 parallel to each other with a small relative spacing, so that
In addition, the bars each have faces of different polarity sequentially in the direction of the internal volume defined by the multipolar cage. The magnetic field thus created between the bars 24 and indicated schematically by the arrows and the symbols N and 8 in FIG. 2 has a reflective effect for the electrons of the plasma thus confined within the volume 19. Armature 23 can be made from a magnetic material, for example stainless steel.

Cross pressure of magnetic field lines perpendicular to each bar 24 is advantageously provided to achieve a magnetic confinement shell by passive electrostatic confinement means in order to limit the loss of electrons in a portion of the corresponding loss cone. .

This means may include, for example, the cage 16 as shown in FIG.
It consists of a layer 25 of insulating material covering the face of each bar that is directed into the internal volume defined by the bar. The layer 25 can be constituted by a sheet or plate of an insulating material such as mica, Kapton etc. or Al2
It can be formed by vapor deposition of a layer of insulating material made from O3, TiO2, etc.

To this end, the armature 23 defines a segmented support 26 with an open cross section consisting of a step edge 27 for maintaining the insulating sheet or layer 25 in the plane of the support.

In the case of using reactive gaseous fluids, the armature 23 defines, in place of the support 26, a tight housing 28 in which the bar 24 is maintained and insulated, as shown in FIG. Can be configured to contain code. This means may be a trap, a layer of insulating material or a plate, sheet or film of insulating material as described above.

The combination of multipolar magnetic confinement and passive electrostatic confinement, all equal, allows the density of the plasma to increase significantly, especially towards high pressures. Such an increase can be approximately by a factor of 2 to 10.

This coupling also allows the electron temperature of the plasma to be reduced by a factor of approximately two.

This binding also increases the generation rate of negative ions with a suitable gaseous medium.

For example, with respect to engraving, oxidizing or depositing on a substrate 30, such as 30, within the scope of application in the field of microelectronics, the substrate 30 is mounted, fixed and fixed in any suitable manner on the substrate carrier 14. 2, so that the surface to be treated is exposed to the plasma generated in volume 19.

In case of application for generation of positive or negative ions, opening 1
2 is equipped with a grid which is suitably polarized by a power source 15 to produce extraction and then possible acceleration of the generated ions.

FIG. 1 shows the volume 19 as a plasma generation portion 19
a and a portion 19b used, for example, for exposing the substrate 30.
A magnetic filter 3 that cooperates with the shell 16 so as to be divided into
1 shows that by lowering its temperature it is possible to improve the properties of the generated plasma. The magnetic filter 31 is made in the same manner as described above for the magnetic confinement shell to increase plasma transmission, except that the spacing between the pars 24 is larger. The magnetic filter may also consist of electrostatic confinement means of the type shown in FIGS. 3 or 4. In each case, the magnetic filter has a structure such that the polarized faces of the bars 24 are parallel to the plane containing the filter and oriented in two parts of the volume.

The invention is not limited to the examples shown, since various modifications can be made without departing from its scope.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an apparatus according to the invention for generating a homogeneous large volume plasma; FIG. 2 is a partial perspective view showing the structure of one of the components constituting the apparatus; FIG. 3 constitutes the object of the invention. FIG. 4 is a perspective view similar to FIG. 3, but showing a modified example. In the figure, 1 is an enclosure, 2 is a pipe, 6 is a gaseous medium supply means, 12 is an opening, 16 is a magnetic confinement shell (multipolar cage), 19 is an internal volume, 19a, 19b
20 is a UHF wave generator, 21a is a window, 23 is a magnetic armature, 25 is an insulating layer, 27 is a step edge, 28 is a tight housing, 30 is a substrate, 61 is a magnetic filter.・ ・− (3 other people)

Claims (1)

[Claims] (1) UHF excitation of the gaseous medium within the enclosure
an apparatus adapted to maintain the plasma within said enclosure in at least a multipolar magnetic confinement, and to maintain an absolute pressure between 10-5 and 1o-1 torr within said enclosure; A method for generating homogeneous large-volume plasma with high density and low electron temperature, characterized by using (2) A homogeneous large volume with high density and low electron temperature according to claim 1, characterized in that the plasma Fi is maintained in multipolar confinement K and passive electrostatic confinement within the enclosure. Plasma generation method. (8) A magnetic filter is used which separates the volume occupied by the plasma from the part that causes the plasma and the partial pressure for use of the plasma. A method for generating homogeneous large-volume plasma with high density and low electron temperature. (4) A method for generating homogeneous large-volume plasma with high density and low electron temperature according to claim 1, 2, or 3, wherein the substrate is subjected to the action of plasma within the enclosure. . (5) A homogeneous large volume with high density and low electron temperature according to claim 1, 2 or 3, wherein ions are extracted from the plasma generated within the enclosure. Plasma generation method. (6) A method for generating a high-density, low-electron-temperature, homogeneous, large-volume plasma according to any one of claims 1 to 5, characterized in that a reactive gaseous medium is excited. The method for generating a homogeneous large-volume plasma with high density and low electron temperature according to claim 1, characterized in that (γ) the gaseous medium is excited by UHF waves in the range of 1 to 10 gigahertz. (8) the gaseous medium is UHF at approximately 245 GHz;
8. The method for generating homogeneous large-volume plasma with high density and low electron temperature according to claim 7, characterized in that the plasma is excited by waves. (9) A device for generating a homogeneous large volume plasma of high density and low electron temperature, including a tight enclosure connected to a pumping circuit and a gaseous medium supply circuit designed to maintain a determined pressure. at least a multipolar magnetic confinement shell, a UHF wave generator terminating in a device for excitation of a gaseous medium disposed opposite a window of said shell, and means for analyzing plasma gold in said confinement shell. A high-density, low-electron-temperature, homogeneous, large-volume plasma generator characterized by: 9. A high-density, low-density battery as claimed in claim 9, characterized in that said enclosure comprises an opening closed by a removable panel supporting a substrate carrier rolling within said shell and connected to a polarization source. Homogeneous large volume plasma generator with electron temperature. 01) The high-density-low-electron-temperature homogeneous large-volume plasma generation device according to claim 9, characterized in that the enclosure consists of an opening occupied by an ion extraction grid connected to a polar source. . 9. A homogeneous large volume plasma of high density and low electron temperature, characterized in that within said enclosure said multipolar magnetic confinement shell is associated with electrostatic confinement means. Generator. Oa) A high-density, low-electron-temperature generator according to claim 9 or claim 12, characterized in that the confinement shell is associated with a magnetic filter that divides the shell into two parts. Homogeneous large volume plasma generator. (4) said confinement shell is constituted by a multipolar cage formed by bars of permanent magnetic nature, said bars extending parallel to each other and extending successively in the direction of the volume defined by said shell; 10. A high-density, low-electron-temperature, homogeneous, large-volume plasma generation device according to claim 9, characterized in that it is supported by a magnetic armature exhibiting polar planes. (1) The confinement shell comprises electrostatic confinement means comprising a layer of insulating material extending in front of the face of the bar directed towards the interior of the shell.
15. The high-density, low-electron-temperature, homogeneous, large-volume plasma generator according to item 1, 12, or 14. (I6) A high-density, low-electron temperature, homogeneous large-volume plasma generation device according to claim 13, characterized in that the magnetic barrier cooperates with electrostatic confinement means on two surfaces thereof. α7) The electrostatic confinement means are made of sheets or plates of insulating material formed by an open part forming part of said cage and maintained in front of each bar by the outermost edge adapted to maintain the bars. A homogeneous large-volume plasma generating device with high density φ and low electron temperature according to claim 15 or 16, characterized in that: Said electrostatic confinement means consist of a sheet or plate of insulating material held together by the two extreme edges of the portion defining a tight housing adapted to accommodate a bar for each par. Features a homogeneous large volume plasma generation cap with high density and low electron temperature.