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
  • H01J37/32431—Constructional details of the reactor
  • H01J37/32458—Vessel
  • H01J37/32477—Vessel characterised by the means for protecting vessels or internal parts, e.g. coatings
• • 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
  • H01J37/321—Radio frequency generated discharge the radio frequency energy being inductively coupled to the plasma

Definitions

• the present invention relates to methods and devices for the etching of substrates, for example in reactors used for the implementation of micromachining or etching processes of a silicon substrate.
• the etching gas or gases are introduced such as a fluorinated gas such as SF 6 at a pre-established flow rate;
• a pumping group and a pressure control system an appropriate pressure is established in the reaction chamber, and this pressure is maintained;
• the gas is excited in the reaction chamber by an electromagnetic excitation wave, to generate a plasma; simultaneously, the substrate is polarized on the sample holder to accelerate the ions which bombard the surface of the substrate during etching.
• the power of the electromagnetic excitation wave allows to ionize and dissociate the molecules of halogen gas such as SF 6 , to generate fluorine atoms. These fluorine atoms arriving on the surface of the silicon substrate will react with it to form a gaseous molecule according to the reaction:
• Si (s) + 4F (g) ⁇ SiF4 (g) Etching thus consists of taking silicon atoms from the substrate, which are transformed by the reaction into a gas SiF 4 which the pumping means eliminate outside the reaction chamber.
• the etching speed of the silicon is directly proportional to the atomic fluorine pressure, therefore to the dissociation rate of the halogen gas molecules such as SF 6 .
• ICP Inductively Coupled Plasma
• ICP-type plasma sources all consist of two main elements:
• An antenna made of an electrically conductive material such as copper, which surrounds or surmounts the sealed wall in dielectric; this antenna is connected at one end to the electrical ground of the equipment and at its other end to a radiofrequency power generator via an automatic impedance adapter.
• the sealed wall of dielectric material is connected to the rest of the wall of the reaction chamber, generally made of metal, by seals generally made of materials of the polymer type. These materials have maximum temperatures of use not exceeding 150 ° C in continuous use. For this, the reaction chamber wall area close to the seals is cooled.
• the quality of the etching depends on the setting to a precise value at all times of all the etching parameters, in particular the pressure of the etching gas, but also of the power of the excitation electromagnetic wave transmitted to the gas to generate the plasma.
• the sequence of the engraving sequences is carried out in a time interval of the order of a few milliseconds. Consequently, at the level of the plasma source, we are in a situation where we must produce an almost instantaneous inductive coupling of the nominal radiofrequency power to the plasma through the sealed wall of dielectric material.
• the object of the present invention is to avoid the drawbacks of known structures and methods for etching a substrate by inductive plasma, by allowing the coupling of radiofrequency powers of up to 5,000 Watts through a dielectric material such as alumina.
• the invention aims to maintain good etching quality, avoiding the use of etching steps in which the parameters are not maintained at their precise nominal values.
• the idea underlying the invention is to reduce the thermal shock of the dielectric material forming the plasma source, by gradually coupling the power of the wave. electromagnetic excitation. We will thus make a ramp up, the slope of this ramp being low enough not to create a destructive thermal shock.
• the only role of neutral gas is to generate a plasma which, under the effect of the progressive increase in power, will gradually heat the dielectric material and thus bring it to its working temperature corresponding to the maximum power used during l reactive gas plasma etching step.
• the invention provides a method of etching a substrate with an inductive plasma, in which the substrate is placed in a reaction chamber, an atmosphere is established in the reaction chamber.
• this method comprises a prior step of progressive establishment of power of the electromagnetic wave of plasma excitation, during which a neutral gas for the substrate is injected into the reaction chamber and the electromagnetic wave power excitation of the plasma until reaching the appropriate nominal power, forming a neutral gas plasma which gradually heats the sealed wall of dielectric material, then the active gas is injected into the reaction chamber to replace the neutral gas and undertake the steps active etching by the active gas plasma.
• the gradual increase in plasma excitation power is programmed so as to limit the thermal shock applied to the sealed wall of dielectric material by the neutral gas plasma below a destructive threshold.
• the preliminary step of progressive establishment of plasma excitation power is undertaken only at the start of operation of the reaction chamber after a period of inactivity, and is followed by an alternation of steps active etching during which the temperature of the sealed wall of dielectric material remains within a sufficiently narrow range of values to avoid any destructive thermal shock of the sealed wall of dielectric material.
• the active etching steps can comprise a succession of etching steps with a fluorinated gas such as SF 6 and passivation steps with a passivation gas such as CxFy.
• the invention also provides a device for etching substrates by inductive plasma implementing a method as defined above, comprising a reaction chamber surrounded by a sealed wall, the reaction chamber containing substrate support means and being in communication with an inductively coupled plasma source with a sealed wall of dielectric material and with an inductive coupling antenna supplied by a radiofrequency generator, the reaction chamber being connected by a vacuum line to pumping means for establishing and maintaining a suitable vacuum in the reaction chamber, the reaction chamber being connected by an inlet line to a source of process gas;
• the source of process gas comprises a source of neutral gas, at least one source of active gas, and distribution means controlled by control means for introducing the appropriate gas into the reaction chamber
• the radiofrequency generator comprises means for adjusting the radiofrequency power controlled by the control means
• control means comprise a control program with a prior sequence of power establishment, in which: a) the control means control the distribution means for introducing a neutral gas into the reaction chamber, b) the means for control control the radiofrequency power adjustment means of the radiofrequency generator so as to produce radiofrequency energy which increases progressively until reaching the nominal power, c) then the control means control the distribution means to replace in the reaction chamber the neutral gas by an active gas.
• FIG. 1 is a schematic view illustrating the general structure of an etching device according to an embodiment of the present invention.
• FIG. 2 schematically illustrates the time diagrams of operation of the main organs of the device of Figure 1, diagram a) illustrating the variation of plasma excitation power, diagram b) illustrating the supply of the reaction chamber in neutral gas, diagram c) illustrating the supply of etching gas to the plasma chamber, diagram d) illustrating the supply of passivation gas to the plasma chamber, and diagram e) illustrating the polarization curve of the substrate to be etched.
• the reaction chamber 1 contains substrate support means 3, suitable to receive and maintain a substrate 16 to be etched.
• the reaction chamber 1 is in communication with a plasma source 4 with inductive coupling, consisting of a sealed wall 5 made of a dielectric material associated with an inductive coupling antenna 6 supplied by a radiofrequency generator 7 via a impedance adapter 7a.
• the reaction chamber 1 is connected by a vacuum line 8 to pumping means 9 to establish and maintain an appropriate vacuum in the reaction chamber 1.
• the reaction chamber 1 is connected by an input line 10 to a source process gas 11.
• the sealed wall 2 of the reaction chamber comprises a peripheral portion 2a which is connected to a front inlet portion 2b which is itself open to communicate with an inlet tube constituting the plasma source 4.
• This plasma source 4 in the illustrated embodiment, consists of a sealed wall 5 of dielectric material, of tubular shape, and the inductive coupling antenna 6 is a coaxial turn of electrically conductive material arranged around the wall. tubular, and connected on the one hand to earth 6a of the device and on the other hand to the output of the impedance adapter 7a.
• the inductive coupling antenna 6 is arranged around the central part of the sealed tubular wall 5 made of dielectric material, itself made of alumina Al 2 0 3 .
• a seal 2c is provided for the connection between the tubular sealed wall 5 of dielectric material and the front inlet portion 2b of the reaction chamber 1, which portion 2b is generally made of metal. Furthermore, cooling means 2d are provided making it possible to cool the front inlet portion 2b and the seal 2c.
• the substrate 16, held on the substrate support means 3, is polarized by a polarization generator 15, in a known manner.
• the source of process gas 11 comprises a source of neutral gas 11a, and at least one source of active gas.
• a first source of active gas 11b containing a gas is provided.
• fluorinated such as SF 6
• a second source of bound active gas containing a passivation gas such as CF 8 .
• Distribution means make it possible to control the introduction of a suitable gas into the reaction chamber 1.
• the distribution means comprise solenoid valves 12a, 12b and 12c each connected in series between an outlet of a corresponding gas source 11a, 11b and 11e and an inlet 14 in the plasma source 4.
• the radiofrequency generator 7 comprises means for adjusting the radiofrequency power, which can be controlled by control means 13. Likewise, the distribution means 12a, 12b and 12c can be controlled by control means 13.
• Control means 13 are provided, for example a microcontroller and input / output members, associated with a control program, suitable for controlling the distribution means with solenoid valves 12a-12c and the radiofrequency generator 7.
• the control means 13 comprise a control program 13a with a prior power establishment sequence, in which: a) the control means 13 control the distribution means, by opening the neutral gas solenoid valve 12a, to introduce a neutral gas such as nitrogen N 2 or argon in the reaction chamber 1, b) the control means 13 control the radiofrequency power adjustment means of the radiofrequency generator 7 so as to produce radiofrequency energy which increases progressively until reaching the nominal power PN, so as to produce a plasma 24 in the plasma source 4 for gradually heating the sealed wall 5 made of dielectric material from the plasma source, c) then, after sufficient heating of the sealed wall 5 , the control means 13 control the distribution means to close the neutral gas solenoid valve 12a and open an active gas solenoid valve 12b or 12c.
• a neutral gas such as nitrogen N 2 or argon
• the etching gas solenoid valve 12b or the passivation gas solenoid valve 12c is sequentially opened to introduce the gases. active in the reaction chamber 1, and the control means 13 simultaneously control the radiofrequency power adjustment means of the radiofrequency generator 7 so as to produce the plasma 24 suitable for the etching and passivation steps.
• FIG. 2 illustrates the steps of an etching method according to an embodiment of the invention.
• the diagram b) indicates the presence of nitrogen during a first step up to time B.
• the pumping means 9 establish and maintain an appropriate pressure inside the reaction chamber 1, pressure chosen for the correct establishment of a plasma 24.
• the substrate 16 is prevented from polarizing, as illustrated in diagram e) of FIG. 2: the polarization voltage V is absent during the step between the instants A and B.
• the plasma excitation power is gradually established, as indicated in diagram a) of FIG.
• the introduction of neutral gas such as nitrogen or argon is interrupted, as represented by example diagram b) which shows the end of the presence of nitrogen from instant B.
• a halogenated etching gas such as SFe, and its presence is maintained during a step BC of appropriate duration depending on the desired etching process.
• the substrate is biased by a voltage V as illustrated in diagram e), possibly establishing * the bias voltage with an appropriate delay relative to the establishment of the presence of the etching gas SF 6 .
• the preliminary step of progressive establishment of plasma excitation power is undertaken only at the start of operation of the reaction chamber 1 after a period of inactivity, and it is followed by the active etching steps, for example d '' an alternation of etching steps and passivation steps, during which the temperature of the sealed wall 5 made of dielectric material remains within a sufficiently narrow range of values to avoid any destructive thermal shock of the sealed wall 5 made of dielectric material .
• the slope of the increase in power illustrated in diagram a) is chosen sufficiently low to avoid any risk of destruction. of the sealed wall 5 made of dielectric material by the neutral gas plasma.
• a neutral gas such as nitrogen N 2 or argon
• the plasma 24 of neutral gas acts on the substrate 16 to be etched, so that a good quality of engraving.
• the polarization of the substrate 16 is also avoided, to avoid bombardment of plasma on the substrate 16.

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

Priority Applications (3)

Applications Claiming Priority (2)

Publications (3)

Family

ID=29763739

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (11)

Family Cites Families (14)

• 2002
  • 2002-07-11 FR FR0208729A patent/FR2842388B1/fr not_active Expired - Fee Related
• 2003
  • 2003-07-10 JP JP2004520755A patent/JP2005532694A/ja active Pending
  • 2003-07-10 EP EP03763951A patent/EP1529305A2/fr not_active Withdrawn
  • 2003-07-10 WO PCT/FR2003/002157 patent/WO2004008816A2/fr not_active Ceased
  • 2003-07-10 US US10/516,455 patent/US20060060566A1/en not_active Abandoned

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