METHOD AND DEVICE FOR TREATING A SUBSTRATE WITH A PLASMA

Abstract: Device for treating a substrate, comprising: means for generating a magnetic field whereof the lines of flux extend substantially parallel to the substrate; means for generating an electrical field whereof the lines of flux extend substantially perpendicular to the substrate and the magnetic lines of flux, wherein these generating means for the electrical field are equipped for generating a field with a frequency of less than 50 kHz.

Description: METHOD AND DEVICE FOR TREATING A SUBSTRATE WITH A PLASMA The present invention relates to a method and device for treating a substrate, for instance for plasma etching of a substrate or other plasma treatments thereof. Of importance here is that the electrons which provide the formation of ions are confined close to the substrate on which the treatment has to be performed, in order to obtain a high etching speed. A device for this purpose is described in the American patent 4.422.896. The device described therein requires cooling and an alternating voltage of high frequency to perform the treatment. These factors makes this device complicated. A first aspect of the present invention provides a device for treating a substrate as according to claim 1, wherein the operation is carried out at a low frequency so that adapter networks and the like can be dispensed with. In addition the present invention provides a device according to claim 3, wherein the magnetic field strength can be precisely controlled, whereby treatments can be carried out more accurately. The present invention also provides a method for treating a substrate. The present invention will be elucidated on the basis of a description of a preferred embodiment thereof with reference to a drawing, wherein: fig. 1 shows a schematic side view of a first embodiment according to the present invention; fig. 2 shows a schematic side view of a second preferred embodiment according to the present invention; fig. 3 shows a schematic side view of a third preferred embodiment according to the present invention; fig. 4 shows a schematic side view of a fourth embodiment according to the present invention; and fig. 5 shows a schematic side view of a fifth embodiment according to the present invention. Placed above a cathode 1 (fig. 1) is a substrate 2 , while a permanent magnet 3 closes as a yoke around a confining space 4 above the substrate or otherwise provides the required field strength close to the substrate. Using the cathode 1 and an anode connection (not shown) a substantially uniform electrical field E with a frequency of less than 50 kHz is generated, while a magnetic field B assumed to be also substantially uniform is generated using the permanent magnet 3. Through the co-action of the E- field and the B-field, electrons which provide for the ionization of molecules such as 0 2 and the like that are required for the treatment have a comparatively long resident time in the vicinity of the substrate, which improves and accelerates the reactive effect. Disposed above the substrate or wafer 5 in fig. 2, which is again arranged on cathode 6, is an electromagnet 7 which makes use of a DC or AC source 8 and a solenoid 9 wound round a core. With this arrangement it becomes possible to control the strength of the magnetic field B whereby the treatment can be controlled more precisely. A still better containment of the electrons is obtained in the embodiment of fig. 3, wherein a substrate 11 is enclosed by a cathode 12 which is insulated from a solenoid 14 by means of an insulating wall 13. The E-field now extends perpendicularly of the walls while the B-field extends perpendicularly of the plane of the drawing. In the embodiment of fig. 4 a substrate 15 is placed on a cathode 16 in which is placed a core 18 provided with a solenoid 17. Particularly in the case of the embodiments of fig. 3. and 4 an electric field with high frequency, for instance the much used frequency of 13.56 MHz, can also be applied. For a more detailed description of the operating principles of the above mentioned embodiments there is referred to reference books in the field of plasmas in addition to the previously mentioned American patent 4.422.896, the content of which should be deemed as interpolated herein. The magnetic field strength and the electrical field strength can vary in both space and time; the above described situation of mutually perpendicular field strengths is a possibility for containing the electrons in the desired manner. The embodiment shown in fig. 5 provides an even greater flexibility since an electrical voltage can be applied to an anode 17 as well as to cathode 18, while the magnetic field strength B can be applied or not and to a greater or lesser degree. The rights are determined by the annexed claims. *****

Claims: CLAIMS 1. Device for treating a substrate, comprising: - means for generating a magnetic field whereof the lines of flux extend substantially parallel to the substrate; - means for generating an electrical field whereof the lines of flux extend substantially perpendicular to the substrate and the magnetic lines of flux, wherein these generating means for the electrical field are equipped for generating a field with a frequency of less than 50 kHz. 2. Device as claimed in claim 1, wherein the generating means for the magnetic field comprise a permanent magnet which defines a containing space above the substrate. 3. Device for treating a substrate, comprising: - means for generating a magnetic field whereof the lines of flux extend substantially parallel to the substrate; - means for generating an electrical field whereof the lines of flux extend substantially perpendicular to the substrate and the magnetic lines of flux, wherein the generating means for the magnetic field are formed by one or more electromagnets. 4. Device as claimed in claim 3, wherein the electromagnet is arranged around a core which defines a containing space above the substrate. 5. Device as claimed in claim 3, wherein the electromagnet is arranged in a substrate holder. 6. Device for treating a substrate comprising means for generating a magnetic field whereof the lines of flux extend substantially parallel to the substrate; and - means for generating an electrical field whereof the lines of flux extend substantially perpendicular to the substrate and the magnetic lines of flux, wherein a substrate is received in a containing space around which one or more solenoid windings are arranged for generating the magnetic field. 7. Method for treating a substrate, wherein use is made of a device as claimed in any of the claims 1-6. 8. Method for treating a substrate wherein: - a magnetic field is generated; - an electrical field is generated; wherein the magnetic field and the electrical field co-act for holding a plasma in position close to the substrate. 9. Method as claimed in claim 6, wherein the electrical field has an alternating frequency of less than 50 kHz. 10. Method, as claimed in claim 8 or 9, wherein the magnetic field is generated using a solenoid. 11. Method for treating a substrate with a plasma, wherein: - an electrical* field is generated between a cathode and an anode; and - a voltage is applied to both the cathode and the anode by a voltage source. ****

Inventors: BRASSEUR GUY JEAN JACQUES, BRASSEUR, GUY, JEAN, JACQUES
Applicants: COBRAIN NV, COBRAIN N.V.
Application year: 1991
Main classification: H01L21
IPC codes: C23C14, C23F4, H01J37, H01L21, H05H1