WO1988001435A1 - Ameliorations apportees a un appareil d'attaque a ions reactifs - Google Patents

Ameliorations apportees a un appareil d'attaque a ions reactifs Download PDF

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Publication number
WO1988001435A1
WO1988001435A1 PCT/AU1987/000261 AU8700261W WO8801435A1 WO 1988001435 A1 WO1988001435 A1 WO 1988001435A1 AU 8700261 W AU8700261 W AU 8700261W WO 8801435 A1 WO8801435 A1 WO 8801435A1
Authority
WO
WIPO (PCT)
Prior art keywords
cathode
anode
plasma
chamber
conducting body
Prior art date
Application number
PCT/AU1987/000261
Other languages
English (en)
Inventor
Roderick William Boswell
Original Assignee
The Australian National University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Australian National University filed Critical The Australian National University
Publication of WO1988001435A1 publication Critical patent/WO1988001435A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32082—Radio frequency generated discharge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32431—Constructional details of the reactor
    • H01J37/32623—Mechanical discharge control means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32431—Constructional details of the reactor
    • H01J37/32697—Electrostatic control

Definitions

  • This invention concerns reactive ion etching. More particularly it concerns modified apparatus - -for- plasma etching techniques which substantially improves the efficiency of such techniques.
  • RIE reactive ion etching
  • the wafer is placed on, or mounted in contact with, the cathode of a plasma chamber which is maintained at a pressure in the range from 1 to about 70 Pa by a vacuum pump while the gas which constitutes the plasma is- -admitted- to -the. chamber.
  • An rf voltage is applied to the cathode in the chamber through a capacitor, to establish a plasma in the chamber between the anode (which is usually earthed) and the cathode.
  • the plasma typically comprises approximately equal densities ' of positive ions and electrons (about 10 to 10 per cubic metre) in a matrix of neutral gas molecules (about ' 10 21 per cubic metre) .
  • a plasma is formed. Because the positive ions and the electrons in the plasma have different velocities, the electrons reach the cathode before the positive ions and establish a negative charge on the cathode. This charge gives the cathode a voltage which is generally termed the "self-bias" of the cathode.
  • the capacitor separating the cathode from the rf supply allows this self-bias voltage to be maintained. Positively charged ions are now attracted from the plasma to the negatively charged cathode. The positive ions so attracted acquire a high energy of several hundreds of volts as they move towards the cathode.
  • This objective is achieved by a simple modification of the cathode of the plasma etching system, namely the inclusion of an electrically conducting body in the plasma chamber, connected to the cathode and positioned between the anode and the cathode but not directly obscuring the line of sight from the anode to the wafer or other body that is being etched.
  • the present inventor has discovered that the presence of such a conducting-body> which may be an annular flat ring or one or more plates, reduces the self-bias voltage by an amount which increases as the ratio of the area of the plate (or plates) to the area of the cathode increases.
  • plasma etching equipment comprising:-
  • At least one electrically conducting body is included within the chamber between the anode and the cathode but not directly obscuring the line of sight from the centre of the anode to the centre of the cathode, said or each conducting body being supported in proximity to the cathode and being electrically connected to the cathode.
  • the cathode is circular and the conducting body is a -flat annular plate .mounted so that the entire body is near the periphery of the circular cathode.
  • conducting bodies of other shapes have been used.
  • the conducting body should be positioned as far as possible from the wafer or other material being etched in the plasma chamber. This precaution will minimise the possibility of metallic pollution of the wafer.
  • Figure 1 is a perspective sketch, partly schematic, of a plasma etching chamber which incorporates one embodiment of the present invention.
  • Figure 2 is a graph showing how the self-bias voltage of the cathode varies as the area of a conductive body (in the form of an annular plate) increases relative to the area of the cathode of the plasma chamber.
  • Figure 3 is a graph showing how the peak-to-peak voltage of the rf signal applied to the cathode of the plasma chamber varies as the area of a conductive body (in the form of an annular plate) increases relative to the area of the cathode.
  • Figure 4 is a graph showing the variation of plasma density with the ratio of the area of a conductive body (in the form of an annular plate) to the area of the cathode of the plasma chamber.
  • Figures 5, 6 and 7 are graphs showing how, for a specific embodiment of the present invention, - the separation of the conductive body (in the form of an annular ' plate.) - . from the cathode affects, respectively,' a.)', the self-bias voltage ! on the cathode of .-a' plasma .chamber, (b) the peak-to-peak voltage of the rf ⁇ signal applied to the cathode, and (c) the plasma density..
  • the plasma etching apparatus illustrated in Figure 1 consists of a plasma chamber 10 - typically made from "pyrex" (trade mark) or another suitable material, which may be an electrical conductor or non-conductor - which is evacuated by a vacuum pump 21 connected to an outlet 11.
  • a gas which forms the plasma, is supplied to the chamber 10 from a gas source 22 via a gas inlet 12.
  • a planar anode 13 of substantially circular shape (a circular shape is not essential) is supported a distance d away from a similarly shaped planar cathode 14.
  • the anode 13 is connected to earth by line 19.
  • the cathode 14 is capacitively connected-,—via-a matching network 15, to an rf oscillator 16.
  • An annular, electrically conducting plate 17 is supported by electrically conductive supports 18 a distance h_ above the cathode 14.
  • the annular conducting plate 17 has an outer diameter which is substantially equal to the diameter of the cathode 14 and is mounted coaxially with the anode 13 ,and the lcathode 14, .However, it should be noted that ⁇
  • plate 17 n'eed not be an annular plate. It may be triangular, square or any convenient polygonal shape.
  • it may. consist of a plurality of conducting bodies separately connected to the cathode 14, the individual bodies being formed in any suitable smooth or polygonal shape (for example, a number of arcuate conducting plates, each forming a segment of a circle, or eight rectangular plates arranged symmetrically around the cathode in the form of an octogon).
  • the annular plate 17 may be replaced with a single conducting body which is generally C-shaped or horseshoe shaped, or with a pair of arcuate, almost semi-circular, conductive plates mounted on opposite sides of the line extending between the centres of the anode 13 and the cathode 14.
  • the conducting body may be a solid body or it may be in the form of a mesh.
  • the ⁇ conducting ' body need not extend over substantially the entire periphery of the cathode.
  • a conducting body of small size, mounted above part only of the edge region of the cathode, is also beneficial to the reactive ion etching technique.
  • the conductive body (or bodies) - ⁇ o be planar for, as will be shown below, as the area of the conductive body increases, so does its effectiveness.
  • Figures 5, 6 and 7 show that the closer the conductive body 17 is located to the cathode, the more effective it is at reducing both the self-bias voltage (Figure 5) and the peak-to-peak value of the minimum rf signal applied to the cathode to establish the plasma (Figure 6), while increasing the plasma density ( Figure 7).
  • this limiting value which may be related to the size of the sheath which separates the plasma from the electrodes, was about 0.9 cm. Similar results to those shown in Figures 2 to 7 were obtained when the plasma was generated using (i) oxygen and (ii) carbon tetrafluoride (CF.) instead of sulphur hexafluoride,
  • the , present invention is not limited to any specific shape of conductive body, or to any one type of plasma.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • ing And Chemical Polishing (AREA)
  • Drying Of Semiconductors (AREA)

Abstract

Les appareils traditionnels d'attaque au plasma, comprennent une anode (13) et une cathode (14) montées de façon espacée dans une chambre de plasma (10). L'anode est généralement mise à la terre et la cathode est connectée de façon capacitive à une source de signaux HF (16). L'application d'une tension HF permet d'établir un plasma du gaz à basse pression dans la chambre. L'amélioration apportée par la présente invention consiste à inclure entre l'anode et la cathode un corps électroconducteur (17) qui est relié à la cathode mais qui n'obstrue par la ligne de collimation entre le centre de l'anode et le centre de la cathode. La présence de ce corps conducteur - qui peut être une plaque annulaire - réduit la tension de polarisation automatique de la cathode et permet en même temps une réduction de l'amplitude minimale du signal HF et une augmentation de la densité du plasma.
PCT/AU1987/000261 1986-08-13 1987-08-12 Ameliorations apportees a un appareil d'attaque a ions reactifs WO1988001435A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPH7420 1986-08-13
AU742086 1986-08-13

Publications (1)

Publication Number Publication Date
WO1988001435A1 true WO1988001435A1 (fr) 1988-02-25

Family

ID=3698100

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1987/000261 WO1988001435A1 (fr) 1986-08-13 1987-08-12 Ameliorations apportees a un appareil d'attaque a ions reactifs

Country Status (1)

Country Link
WO (1) WO1988001435A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2244721A (en) * 1990-05-03 1991-12-11 Northern Telecom Ltd Plasma processing apparatus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1342513A (en) * 1970-03-18 1974-01-03 Philips Electronic Associated Ion engraving apparatus
US4349409A (en) * 1980-05-12 1982-09-14 Fujitsu Limited Method and apparatus for plasma etching
US4585516A (en) * 1985-03-04 1986-04-29 Tegal Corporation Variable duty cycle, multiple frequency, plasma reactor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1342513A (en) * 1970-03-18 1974-01-03 Philips Electronic Associated Ion engraving apparatus
US4349409A (en) * 1980-05-12 1982-09-14 Fujitsu Limited Method and apparatus for plasma etching
US4585516A (en) * 1985-03-04 1986-04-29 Tegal Corporation Variable duty cycle, multiple frequency, plasma reactor

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2244721A (en) * 1990-05-03 1991-12-11 Northern Telecom Ltd Plasma processing apparatus
GB2244721B (en) * 1990-05-03 1993-05-19 Northern Telecom Ltd Plasma processing apparatus

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