Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
  • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
  • H01L21/3065—Plasma etching; Reactive-ion etching
• • 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
  • H01J37/32174—Circuits specially adapted for controlling the RF 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
  • H01J37/32009—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
• • 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
  • H01J37/3266—Magnetic control means

Definitions

• the present invention relates to a method for generating a plasma generated by an induction coil in the vacuum chamber of a vacuum recipient and a device which is suitable for carrying out the method according to the invention.
• the invention further relates to the use of the method according to the invention for optionally reactive coating or for optionally reactive etching of a substrate.
• a plasma which is generated in the vacuum chamber of a vacuum recipient, is involved in a large number of process steps, e.g. common in the case of optionally reactive coating or optionally reactive etching of substrates.
• the plasma can be generated inductively and / or capacitively.
• EP 0,271,341-A1 describes, for example, a device for dry-etching semiconductor wafers, which comprises an induction coil for plasma generation and an electrode device for extracting ionized particles from the plasma onto the substrate.
• the energy for plasma generation is inductively coupled into the vacuum chamber of the vacuum recipient, which serves as a reactor, via a coil-shaped antenna.
• the substrate is located on an electrode which serves as a substrate carrier and which is subjected to a so-called RF (radio frequency) bias or bias in order to regulate the energy of the ions in the plasma.
• No. 5,460,707 describes a device for capacitive plasma generation which can also be used for coating purposes. To control the plasma density distribution or to generate a locally increased plasma density, a magnetic field can be present which is generated by an additional permanent or electromagnet.
• EP 0,413,283 describes that a planar plasma can be obtained by using an electrically conductive planar flat coil, the induction field being generated by connecting a high-frequency voltage source to the flat coil and being coupled in via a dielectric shield.
• US Pat. No. 6,022,460 proposes to allow the plasma, which is inductively generated at least by a flat coil with high-frequency alternating voltage or by a coil in the form of a vacuum bell, to have a further magnetic field generated by a pair of Helmholtz coils.
• the Helmholtz coil pair is acted upon by a combination of direct and alternating current, so that a weak magnetic field, modulated by the alternating voltage component, results, which allows an influencing of the magnetic field referred to as “shaking”.
• a weak magnetic field modulated by the alternating voltage component
• a disadvantage of the device for generating a plasma described in US '460 is that the additional pair of Helmholtz coils makes a compact design of the device difficult and increases the cost of the device. Since the induction coil must be decoupled from the pair of Helmholtz coils for high-frequency reasons, spatial separation of the induction coil and the Helmholtz coil pair is imperative.
• the present invention was therefore based on the object of providing a method and a device for generating a plasma with high homogeneity which does not have the disadvantages described in the prior art or has them to a lesser extent. Further objects of the present invention will become apparent from the detailed description that follows.
• the present invention relates to a method for generating a plasma, which is at least also generated in the vacuum chamber (la) of a vacuum recipient (1) of a device suitable for plasma treatment with at least one induction coil (2) to which alternating current is applied, the gas used to generate the plasma through at least one inlet (3) into the vacuum chamber (la) and the vacuum chamber (la) is pumped through at least one pump arrangement (4), and wherein the induction coil (2) to influence the density of the plasma additionally by an optionally modulated, preferably pulsed direct current is applied.
• the present invention relates to the use of the method according to the invention for optionally reactive coating and / or for optionally reactive etching of substrates (9).
• the present invention further relates to a device suitable for plasma treatment, comprising at least one induction coil (2) at least for the generation of the plasma in the vacuum chamber (la) of a vacuum recipient (1), the vacuum Chamber (la) has at least one inlet (3) for inlet of a gas used for generating the plasma and a pump arrangement (4), and wherein the induction coil (2) is connected to one or more voltage generators, which the induction coil with an alternating current and a if necessary apply unipolar or bipolar pulsed direct current.
• Fig. 1 is a schematic representation of a device according to the invention, which is suitable for plasma treatment.
• the plasma used for the etching being at least also generated by an induction coil 2, which is generated by a direct and an alternating current (curve I) or only by an alternating current (curve II) was applied.
• the device according to the invention suitable for plasma generation comprises a vacuum recipient 1 with a vacuum chamber 1 a, which can be evacuated by one or more pump arrangements 4.
• the vacuum recipient 1 comprises an outer housing 10 made of, for example, metals such as stainless steel or aluminum, in order to achieve a good seal of the vacuum recipient and a shield, in particular against external electrical stray fields.
• the metal housing 10 of the vacuum recipient 1 can preferably have a dielectric inner housing 7 on the vacuum side, which can, for example, be applied to the outer housing 10 internally or as a coating.
• the dielectric material is preferably selected such that it is on the one hand as inert as possible to the gases used in reactive etching or coating processes, for example chlorine and / or fluorine-containing gases, and on the other hand that it is as permeable as possible for the inductively coupled power.
• Preferred dielectric materials include, for example, polymer materials, ceramic materials, quartz and aluminum oxide and in particular ceramic materials, Quartz and aluminum oxide.
• Preferred dielectric materials include, for example, polymer materials, ceramic materials, quartz and aluminum oxide and in particular ceramic materials, Quartz and aluminum oxide.
• the vacuum recipient 1 described in EP 0,413,283 has a dielectric shield, which can be contained, for example, in the upper top wall of the vacuum recipient 1.
• vacuum recipient 1 is only to be understood as an example and is intended to explain the invention and not to limit it.
• the vacuum chamber la contains one or more gas inlets 3 through which the gas used for generating the plasma is admitted.
• the gas which can consist of a single gas compound or can also be a mixture of several gas compounds, is selected in particular with regard to the chemical composition and physical parameters of the substrate 9 to be treated and the modification of the substrate surface to be achieved. If the surface of the substrate is to be cleaned (sputter etching), the gas can contain, for example, Ar or another noble gas, while gases can be used for reactive etching processes, for example Cl 2 , SiCl 4 , BC1 3 , CF 4 , CHF, SF 6 and / or can contain O 2 .
• organometallic compounds CH 4 , SiH 4 , NH 3 , N 2 and / or H 2 can be used.
• the gas compounds and processes mentioned for the treatment of substrates 9 are to be understood as examples and are only intended to explain and not limit the invention.
• the flow of the gas and the power of the pump arrangement (s) 4 is preferably selected such that the pressure in the vacuum chamber 1 a of the vacuum recipient 1 is in particular between 0.01 and 10 Pa and particularly preferably between 0.05 and 0.2 Pa.
• the device according to the invention contains at least one induction coil 2, through which the plasma generated in the vacuum chamber 1 a of the vacuum recipient 1 at least is also generated.
• the induction coil (s) 2 are preferably arranged in the vacuum recipient 1 or in the vacuum chamber 1 a in such a way that they are not exposed to the plasma, for example in order to deposit electrically conductive interference coatings or other coatings on the induction coil (s) 2 or damage to avoid the induction coil (s) 2 by the plasma.
• the induction coil (s) 2 are preferably separated from at least the part of the vacuum chamber 1 a in which the plasma is generated by a dielectric shield, such as a dielectric inner housing 7.
• the induction coil ⁇ ) 2 can preferably also be arranged outside the vacuum chamber 1 a.
• the device according to the invention contains one or more induction coils 2, preferably one or two induction coils 2 and in particular an induction coil 2.
• the shape of the induction coil (s) 2 can vary and is preferably chosen such that an induction field which is as homogeneous as possible is obtained even without the induction coil (s) 2 being subjected to a direct current.
• an induction coil 2 it comprises windings which are wound directly onto the vacuum chamber 1 a or preferably onto a dielectric inner housing 7 located therein.
• the coil turns are e.g. wound on the side wall of the dielectric inner housing 7.
• the homogeneity of the induction field can e.g. are influenced by the number and arrangement of the turns of the induction coil (s) 2 and the geometrical dimensions of the dielectric inner housing.
• the induction coil 2 is designed as a flat or planar coil, which can consist, for example, of a number of turns arranged in a spiral or in a series of concentric circles, as described in EP 0,413,282.
• the flat coil can, for example, preferably have a circular or ellipsoidal shape.
• the term "flat" or “planar” means that the ratio of the thickness of the coil to the extent in the other two directions perpendicular to the thickness is less than 0.3 and preferably less than 0.2.
• EP 0,413,282 discloses that the flat coils are preferably close to a dielectric shield in the outer housing 10 of the vacuum regulator. are arranged, which acts as a dielectric window and allows coupling of the induction field. It is of course also possible to arrange the flat coil close to the dielectric inner housing 7.
• the induction coil 2 has the shape of a vacuum bell, as is disclosed in US Pat. No. 6,022,460.
• the density of the plasma generated at least by the induction coil (s) 2 and in particular the homogeneity of the plasma can be increased if the induction coil (s) 2 is acted upon by an alternating current and additionally and simultaneously by a direct current.
• the application of alternating current to the induction coil (s) 2 serves to couple high-frequency power into the vacuum recipient 1 for at least co-generation of the plasma.
• the induction coil 2 is preferably connected to a high-frequency voltage generator 6 via a matching network 13.
• the matching network 13 serves to adapt the output resistance of the high-frequency voltage generator 6 and the impedance of the induction coil (s) 2 and the vacuum chamber 1 a or the plasma generated therein, in order to be able to couple in the high-frequency power as effectively as possible.
• the term “high frequency” is used for electromagnetic vibrations or waves with a frequency between 10 kHz and 3 GHz.
• the high-frequency voltage generator 6 can be particularly preferred in a wide high-frequency spectrum of preferably 100 kHz to 100 MHz from 100 kHz to 14 MHz and very particularly preferably from 400 kHz to 2 MHz.
• a preferred frequency also depends on the geometry of the induction coils ⁇ ) 2.
• a frequency between 100 kHz and 2 MHz and chosen in particular between 200 kHz and 1 MHz.
• higher frequencies preferably between 2 MHz and 14 MHz are selected.
• the preferred upper limit of this frequency range therefore results in the standard frequency of the high frequency voltage generators most commonly used in the industry being 13.56 MHz. This frequency is approved for industrial use by international telecommunications agreements.
• the density distribution of the plasma can be influenced and preferably the homogeneity of the plasma e.g. can be increased in the area of the expansion of a substrate 9.
• the induction coil 2 is additionally preferably connected to a DC voltage generator 6 'via a low-pass filter 12.
• the low pass filter 12 which e.g. can comprise a coil and a capacitor connected in parallel with it, is preferably designed such that the direct current can reach the induction coil 2 while the high-frequency current is blocked, so that it cannot reach the direct current source.
• the direct current can be uniform or also modulated, e.g. be unipolar or bipolar pulsed.
• the direct current is preferably set such that the product of the number of turns and the direct current is on average and absolutely between 10 and 1000 and particularly preferably between 100 and 400 A turns.
• the number of turns of the induction coil 2 is preferably at least 7, particularly preferably at least 10 and very particularly preferably at least 12, since as the number of turns decreases, the current required for homogenizing the plasma density distribution increases, as a result of which the requirements for the direct current generator 6 ′ and the low-pass filter 12 increase increase.
• a Langmuir probe for example, can be used to measure the plasma density distribution. Since the homogeneity of the plasma density distribution in the area of the substrate 9 in sputter etching or reactive etching processes and in reactive coating processes, if applicable, depends on the homogeneity of the etching depth distribution or the coating thickness distribution. effect along a cross-section through the substrate, the homogeneity of the plasma density distribution can also be measured by measuring the distribution of the etching depth or the coating thickness.
• the measurement of the etching depth can e.g. for a thermally oxidized silicon wafer, first by etching the thickness of the silicon oxide layer e.g. with an egg lipometer in a grid over the entire surface of the silicon wafer or e.g. is measured along a diameter of the silicon wafer. After the etching process, the thickness of the remaining silicon oxide layer is measured. The etching depth results from the difference in the thicknesses of the silicon oxide layer before and after the etching process.
• This method can be applied analogously to the measurement of coating thicknesses.
• the homogeneity or uniformity of the distribution of e.g. the etching depth or also the plasma density or the coating thickness e.g. along a cross section through a substrate 9 can be characterized by the so-called uniformity index, which is defined as
• Uniformity index (maximum value - minimum value) / (maximum value + minimum value)
• the maximum value or the minimum values are the largest or the smallest values of the distribution to be characterized, for example on the entire surface of the substrate 9 or along a cross section through the substrate.
• the uniformity index is usually given in%.
• the direct current acting on the induction coil 2 is preferably selected such that the uniformity index of the distribution of plasma density, etching depth and / or coating thickness, for example along an arbitrarily selected cross section through the substrate 9 or, for example, over a certain part or the entire surface of the substrate 9, is not greater than 10%, preferably not larger than 7.5% and very particularly preferably not larger than 5%.
• it contains at least one pair of spaced electrodes 5a, 5b.
• the electrodes 5a, 5b can be formed by the metallic connections in the upper and lower ceiling wall of the vacuum recipient 1, which are galvanically separated from one another by the side wall made of dielectric material.
• No. 6,068,784 describes a three-electrode arrangement in which the substrate table 8 serves as a cathode and the side wall of the vacuum recipient serves as an anode and the top wall of the upper dome-like protuberance of the vacuum recipient forms a third electrode.
• an electrode 5a of the pair of electrodes 5a, 5b is formed by the substrate table 8 on which the substrate 9 rests or on which it is held with a usually electrostatic or mechanical holding and / or centering device (in the case of a wafer Substrate also referred to as wafer chuck) is attached.
• the substrate table itself is usually electrically insulated from the housing 10 of the vacuum chamber.
• an electrical connection in the upper ceiling wall or end face of the vacuum recipient can serve as the counter electrode 5b.
• Particularly preferred is e.g. circular substrate table 8 surrounded by a ring serving as a counter electrode, which is usually referred to as dark room shielding.
• the vacuum in the vacuum chamber 1 a serves for insulation between the substrate table 8 and the dark room shield in the upper region of the dark room shield.
• the dark room shield is attached to the substrate table 8 in a centered manner via an annular ceramic insulator and is galvanically separated from it.
• the pair of electrodes 5a, 5b can e.g. be connected to a possibly unipolar or bipolar pulsed DC voltage source, to an AC voltage source or simultaneously to a DC and AC voltage source.
• the plasma is capacitively excited by the voltage applied to the pair of electrodes 5a, 5b, which is also referred to as bias.
• the pair of electrodes 5a, 5b is preferably supplied with a direct voltage or an alternating voltage, in particular with a high-frequency alternating voltage with a frequency between 100 kHz and 100 MHz.
• a suitable frequency of the alternating voltage the effects on the substrate 9 or on the vacuum chamber 1a shown in US Pat. No. 6,068,784, column 4, lines 23-52 can preferably be taken into account; this discussion is referred to here.
• the substrate table 8 is used as the electrode 5 a and a dark room shield as the counter electrode 5b
• the substrate table 8 is provided with a high-frequency voltage generator 11 with a frequency of preferably more than 3 MHz and particularly preferably of more than 10 MHz connected while the dark room shield is grounded.
• the vacuum recipient 1 comprises an evacuable boiler 10 from e.g. stainless steel, which encloses the vacuum chamber la and a dielectric inner housing 7 made of e.g. Contains quartz or aluminum oxide.
• the induction coil 2 is wound around the dielectric inner housing and is connected to the AC voltage generator 6 via the matching network 13 and additionally to the DC voltage generator 6 'via the low-pass filter 12; the return is via earth.
• the substrate table 8, on which the substrate 9 rests, serves as an electrode 5a and is surrounded by a circular, centered dark room shield, which acts as a counter electrode 5b.
• the vacuum chamber la is pumped with a pump arrangement 4.
• In the upper ceiling wall of the vacuum recipient 1 there is e.g. Centrally arranged gas inlet 3.
• the diameter of the dielectric inner housing was 275 mm.
• the distance between the substrate table 8 and the upper ceiling wall of the vacuum recipient 1 was 180 mm.
• the induction coil 2 wound around the dielectric inner housing 7 had a diameter of 304 mm and consisted of 15 turns.
• Ar was fed in for sputter etching via the gas inlet 3, so that an operating pressure of 10 "3 mbar was reached.
• the substrate table 8 serving as the electrode 5a was subjected to a high-frequency bias of 13.56 MHz, and the dark room shield serving as the counter electrode was grounded.
• the induction coil 2 was connected via a matching network 13 consisting of two capacitors to an AC voltage generator 6 operated at 400 kHz.
• the magnetic field thereby induced in the interior of the induction coil 2 was approximately 5 Gauss.
• the induction coil 2 was simultaneously connected to a DC voltage source via a low-pass filter 12, which consisted of a capacitor and a coil connected in parallel therewith.
• the direct current which was chosen such that the sputter etching depth distribution along a diameter of the wafer serving as substrate 9 had a uniformity index ⁇ 3%, was approximately 10 A and caused a magnetic field of approximately 12 Gauss.
• FIG. 2 shows the normalized sputter etching depth distribution for a previously thermally oxidized, circular silicon wafer with a diameter of 300 mm along a diameter of the wafer.
• the measurements were carried out under the operating conditions described in FIG. 1 in a corresponding arrangement which had the geometric dimensions required to accommodate a 300 mm wafer.
• the curve I shown in FIG. 2 was obtained for a method according to the invention, in which the induction coil 2 with an alternating current and additionally with a direct current of approximately
• curve II shows the sputter etching depth distribution which is obtained when the induction coil is only supplied with an alternating current. It can be seen from curve II that the sputter etching depth only drops to the edge of the wafer substrate 9 when the induction coil is acted on by an alternating current; in addition, the sputter etching depth distribution is tilted asymmetrically. Curve I shows that the additional application of a direct current to the induction coil 2 significantly improves the homogeneity of the sputter etching depth distribution. An asymmetrical tilting of the sputter etching depth distribution is practically no longer observed.
• the device according to the invention can be part of a so-called cluster as a processing station.
• a cluster is understood to be the compilation of several, often different processing stations, which have a common transport device such as have a handling robot.
• another processing station e.g. a PVD (physical vapor deposition) system.
• the various processing stations are preferably separated from the transport space via corresponding locks.
• the device according to the invention is loaded with the substrate 9 via the transport device through the lock (not shown in FIG. 1).
• the transport device deposits the substrate 9 on the substrate table 8, where it may be centered and held.
• the vacuum chamber 1 a is evacuated via the pump device 4; parallel to this or subsequently, the substrate 9 is optionally set to the desired process temperature by means of temperature control devices contained in the substrate table 8.
• the gas required to generate the plasma is fed in via the gas inlet 3.
• the plasma is then ignited by applying the high-frequency voltage to the induction coil 2 and the high-frequency bias to the substrate table 8.
• the direct current is applied to the induction coil 2.
• the substrate 9 is removed from the vacuum recipient 1 again.

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• Engineering & Computer Science (AREA)
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• 2001
  • 2001-09-28 DE DE10147998A patent/DE10147998A1/de not_active Withdrawn
• 2002
  • 2002-09-24 TW TW091121849A patent/TWI290809B/zh not_active IP Right Cessation
  • 2002-09-26 EP EP02777222A patent/EP1433192A1/de not_active Ceased
  • 2002-09-26 KR KR1020047004415A patent/KR100960978B1/ko active IP Right Grant
  • 2002-09-26 CN CNB028189183A patent/CN100364035C/zh not_active Expired - Lifetime
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  • 2002-09-26 WO PCT/EP2002/010811 patent/WO2003030207A1/de active Application Filing
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• 2008
  • 2008-12-04 US US12/315,608 patent/US8613828B2/en active Active

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