Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/20—Dry etching; Plasma etching; Reactive-ion etching
  • H10P50/28—Dry etching; Plasma etching; Reactive-ion etching of insulating materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/20—Dry etching; Plasma etching; Reactive-ion etching
  • H10P50/28—Dry etching; Plasma etching; Reactive-ion etching of insulating materials
  • H10P50/282—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of inorganic materials
  • H10P50/283—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of inorganic materials by chemical means
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/73—Etching of wafers, substrates or parts of devices using masks for insulating materials

Definitions

• the present invention relates to an improved method for plasma etching
• dielectric materials such as silicon oxide in the fabrication of integrated circuits.
• the dielectric materials include doped silicon oxide such as fluorinated silicon oxide (FSG), undoped silicon oxide such as silicon dioxide, silicate glasses such as boron phosphate
• the dielectric dopants include boron, phosphorus and/or arsenic.
• the dielectric can overlie a conductive or semiconductive layer such as polycrystalline silicon, metals such as aluminum, copper, titanium, tungsten, molybdenum or
• nitrides such as titanium nitride
• metal suicides such as titanium suicide, cobalt suicide, tungsten suicide, molydenum suicide, etc.
• Etching gas chemistries include the oxygen-free, Ar,
• a metallization pattern for either conductors or vias is etched into a dielectric layer, a metal layer is filled into the etched
• CMP chemical mechanical planarization
• the metallization patterns for the vias and conductors are etched in a dielectric layer and the etched grooves and via openings are filled with metal in a single metal filling and excess metal removal process.
• Medium density plasma reactors operate at higher chamber pressures and dissociate etching gas chemistries to a lesser extent than high density plasma
• etching gases such as C 4 F 8 dissociate in stages as follows: C 4 F 8 -> C 2 F 8 - CF 2 ⁇ CF+F. Due to such gradual dissociation, it is possible to achieve a high etch rate of a dielectric layer
• an overlying layer such as a photoresist or underlayer
• etch stop layer As an etch stop layer.
• the ratio of such etch rates is referred to as the "etch stop layer
• selectivity ratio and the high selectivity ratios obtainable in medium density plasma reactors promote complete etching of contacts, vias and conductor patterns.
• instantaneous dissociation of etching gases in high density reactors, the instantaneous dissociation of etching gases
• selectivity ratios is even greater in order to achieve plasma etching of deep and
• the invention provides a process for plasma etching a dielectric layer
• the dielectric layer can be etched in a single step to expose the electrically
• the etching is performed by exposing the dielectric layer to an etching gas in an ionized state
• the etching gas including fluorocarbon reactant and carbon monoxide and an optional inert carrier gas.
• the dielectric layer comprises
• silicon oxide such as doped or undoped silicon dioxide, BPSG, PSG, TEOS, or
• thermal silicon oxide and the openings comprise grooves corresponding to a conductor pattern, via openings or contact openings. According to another aspect
• the openings can be etched so as to have an aspect ratio of at least 3:1.
• the etching gas can include a hydrogen-containing and/or a hydrogen-free fluorocarbon reactant represented by C x F y H z wherein x is at least 1, y is at least
• the fluorocarbon reactant can be any fluorocarbon reactant.
• the fluorocarbon reactant can be any fluorocarbon reactant.
• the electrically conductive or semiconductive layer can comprise a metal-containing layer selected from the group consisting of Al, Al alloys, Cu, Cu
• the process of the invention can etch openings which are 0.30 ⁇ m,
• a fluorocarbon reactant which comprises C x F y H z wherein x is 1 to 5, y is 1 to 8 and
• the fluorocarbon reactant can comprise one or more
• optional carrier gas can be selected from the group consisting of Ar, He, Ne, Kr,
• the CO can be supplied to the plasma reactor at a flow rate of 25 to 250 seem, the fluorocarbon can be supplied to the plasma reactor at a
• fluorocarbon, and Ar can be supplied to the plasma reactor at flow rates of 50 to
• the high density plasma reactor is preferably maintained at a vacuum pressure
• the etching step can be followed by filling the openings with metal.
• the method of the invention can also include steps of forming a
• openings and the etching step forms a metallization pattern of conductor lines, via or contact openings in the dielectric layer.
• openings can be formed with an aspect ratio of at least 5:1.
• the process of the invention thus provides a semiconductor manufacturing process wherein deep and narrow quarter micron and smaller openings can be
• the plasma gas chemistry includes fluorocarbon and CO which cooperate to etch the dielectric material while providing a desired selectivity wit respect to the
• Figures la-d show schematic representations of a via-first dual-damascene structure which can be etched according to the process of the invention
• Figures 2a-d show schematic representations of a trench-first dual- damascene structure which can be etched according to the process of the invention, Figure 2a showing a pre-etch condition, Figure 2b showing a post-etch condition
• Figures 3a-b show schematic representations of a self-aligned dual-
• damascene structure which can be etched according to the process of the invention
• Figure 3a showing a pre-etch condition
• Figure 3b showing a post-etch
• Figure 4 shows a schematic representation of an inductively coupled high
• Figure 5 is a SEM micrograph of a dual-damascene structure etched in accordance with the invention.
• Figure 6 is a SEM micrograph of a TEOS over Si structure at the center of
• Figure 7 is a SEM micrograph of a TEOS over Si structure at the edge of a
• Figure 8 is a SEM micrograph of a PSG over S%N 4 structure at the center
• Figure 9 is a SEM micrograph of a PSG over S%N 4 structure at the edge of
• Figure 10 is a graph showing the effects of CO flow rates on the etch rate of TEOS, the etch rate increasing steadily to 50 seem CO;
• Figure 11 is a graph showing the effects of CO flow rates on the etch depth
• the invention provides a process of high density plasma etching of features such as contacts, vias, conductor lines, etc. in dielectric materials such as oxide
• the invention overcomes a problem with prior etching techniques wherein the selectivity between the
• doped and undoped oxide films BPSG, PSG, TEOS
• BPSG, PSG, TEOS doped and undoped oxide films
• Figures 1 a-d show schematics of how a via-first dual-damascene structure can be etched in accordance with the invention.
• Figure la shows a pre-etch
• a photoresist masking layer 12 which overlies a stack of a first dielectric layer 14 such as silicon oxide, a first stop layer 16 such as silicon nitride, a second dielectric layer 14 such as silicon oxide, a first stop layer 16 such as silicon nitride, a second dielectric layer 14 such as silicon oxide, a first stop layer 16 such as silicon nitride, a second dielectric layer 14 such as silicon oxide, a first stop layer 16 such as silicon nitride, a second
• dielectric layer 18 such as silicon oxide
• second stop layer 20 such as silicon
• Figure lb shows the structure after etching wherein the opening 10 extends through the dielectric layers 14, 18
• Figure lc shows the structure after re-patterning the masking layer for a trench 24.
• Figure Id shows the
• Figures 2 a-d show schematics of how a trench-first dual-damascene
• FIG. 2a shows a pre-
• etch condition wherein an opening 30 corresponding to a trench is provided in a photoresist masking layer 32 which overlies a stack of a first dielectric layer 34 such as silicon oxide, a first stop layer 36 such as silicon nitride, a second dielectric layer 34 such as silicon oxide, a first stop layer 36 such as silicon nitride, a second dielectric layer 34 such as silicon oxide, a first stop layer 36 such as silicon nitride, a second
• Figure 2c shows the structure after re-patterning the masking layer for a via 44.
• Figure 2d shows the structure after etching wherein the second
• dielectric layer 38 is etched down to the second stop layer 40.
• Figures 3 a-b show schematics of how a dual-damascene structure can be
• Figure 3a shows a pre- etch condition wherein an opening 50 corresponding to a trench is provided in a photoresist masking layer 52 which overlies a stack of a first dielectric layer 54 such as silicon oxide, a first stop layer 56 such as silicon nitride, a second dielectric layer 54 such as silicon oxide, a first stop layer 56 such as silicon nitride, a second dielectric layer 54 such as silicon oxide, a first stop layer 56 such as silicon nitride, a second
• dielectric layer 58 such as silicon oxide
• second stop layer 60 such as silicon nitride
• substrate 62 such as a silicon wafer.
• first stop layer 56 includes an opening 64.
• Figure 2b shows the structure after etching wherein the
• opening 50 extends through the dielectric layer 54 to the first stop layer 56 and the
• opening 64 extends through the second dielectric 58 to the second stop layer 60.
• Such an arrangement can be referred to as a "self-aligned dual-damascene"
• the process of the invention is applicable to etching of various dielectric
• doped silicon oxide such as fluorinated silicon oxide (FSG)
• undoped silicon oxide such as silicon dioxide
• silicate glasses such as fluorinated silicon oxide (FSG)
• FSG fluorinated silicon oxide (FSG)
• undoped silicon oxide such as silicon dioxide
• SOG spin-on-glass
• boron phosphate silicate glass BPSG
• PSG phosphate silicate glass
• doped or undoped thermally grown silicon oxide doped or undoped TEOS deposited silicon oxide, etc.
• the dielectric dopants include boron, phosphorus
• the dielectric can overlie a conductive or semiconductive layer such as polycrystalline silicon, metals such as aluminum, copper, titanium,
• tungsten tungsten, molybdenum or alloys thereof, nitrides such as titanium nitride, metal
• suicides such as titanium silicide, cobalt silicide, tungsten silicide, molydenum
• High density plasma can be produced in various types of plasma reactors.
• Such plasma reactors typically have high energy sources which use RF energy
• the high density plasma could be produced in a transformer coupled
• TCPTM which is also called inductively coupled plasma reactor
• ECR electron-cyclotron resonance
• the reactor 100 includes
• Etching gas can be supplied to a showerhead arrangement be supplying gas from gas supply 106 to a
• density plasma can be generated in the reactor by supplying RF energy from an RF source 112 to an external RF antenna 114 such as a planar spiral coil having one
• the plasma generating source can be part of a modular mounting arrangement removably
• a semiconductor substrate 116 such as a wafer is supported within the
• a substrate support 118 such as a cantilever chuck arrangement removably supported by a modular mounting arrangement from a sidewall of the
• the substrate support 118 is at one end of a support arm mounted in a cantilever fashion such that the entire substrate support/support arm assembly can
• the substrate support 118 can include a chucking
• an electrostatic chuck 120 and the substrate can be surrounded
• the chuck can include an RF biasing electrode for
• gas supply 106 supplied by gas supply 106 can flow through channels between the window 110 and an underlying gas distribution plate 124 and enter the interior 102 through gas
• the reactor can also include a heated liner 126 extending conically from the plate 124 .
• the invention provides a process for plasma etching
• fluorocarbon is instantaneously dissociated into free F and free C.
• the carbon monoxide is instantaneously dissociated into free C and free oxygen by the high density plasma and the free C reacts with some of the free F to thereby reduce the etch rate of the masking and/or stop etch layers.
• the CO is effective in providing a desired level of selectivity between the
• nitride and/or an overlayer such as a photoresist while at the same time balancing polymer build-up sufficiently to protect sidewalls of etched features while avoiding
• Etch stop is
• dielectric materials such as silicon oxide using gas chemistries which form too
• the polymer build-up can be any polymer build-up.
• the polymer build-up can be any polymer build-up.
• carbon monoxide is added in an amount
• the CO when using an etching gas containing CO and one or more fluorocarbon gases, the CO is effective to scavenge free F dissociated from the fluorocarbon in
• the CO is preferably supplied to the plasma etching
• the etching gas mixture may optionally include other gases such as
• Argon is an especially useful inert carrier gas
• inert gases such as He, Ne, Kr and/or Xe can be used as the inert carrier gas.
• the inert carrier gas such as He, Ne, Kr and/or Xe
• amount of carrier gas introduced into the reactor can be at low flow rates.
• argon can be supplied into the reactor in amounts of 25 to 300 seem.
• the carrier gas preferably aids the dielectric etch
• the fluorocarbon preferably comprises C x F y H z wherein x is at least 1, y is
• At least 1 and z is 0 or above, e.g., CF 4 , C 3 F 6 , C 3 F 8 , C 5 F 8 , C 4 F 8 , C 2 F 6 , CH 2 F 5 ,
• the amount of fluorocarbon gas to be supplied to the plasma reactor should be sufficient to achieve the desired degree of
• the CO can be supplied at flow rates
• to 150 seem, preferably 40 to 100 seem, and more preferably 60 to 70 seem.
• the CO flow rate can range
• the process of the invention is useful for obtaining extremely high aspect
• substrate support can be supplied with power on the order of 500 to 3000 Watts to adequately RF bias 6, 8 or even 12 inch wafers.
• the reactor pressure is preferably maintained as low as possible. In general, too low a reactor pressure can lead to plasma extinguishment whereas too high a reactor pressure can lead to the etch stop problem. For high density plasma
• the reactor is preferably at a pressure below 30 mTorr, more preferably
• the vacuum pressure at the substrate surface may be higher
• etching preferably cools the substrate enough to prevent burning of any photoresist
• the substrate support e.g., maintain the substrate below 140° C. In high density plasma reactors, it is sufficient to cool the substrate support to a temperature of -
• the substrate support can comprise a bottom electrode such as an ESC on which a substrate such as a silicon wafer is electrostatically clamped and cooled by supplying helium at a desired pressure between the wafer and top
• the He can be maintained at a pressure of 10 to 30 Torr in
• planar coil antenna can be supplied with RF
• the power should be sufficient to instantaneously dissociate the fluorocarbon to free F and free C. As explained earlier, such intense plasmas
• dielectric materials such as doped or undoped silicon oxide, e.g., undoped silicate glass (USG), boron phosphorus silicate glass (BPSG), phosphorus silicate glass (PSG), spin on glass (SOG), doped
• dielectric materials such as doped or undoped silicon oxide, e.g., undoped silicate glass (USG), boron phosphorus silicate glass (BPSG), phosphorus silicate glass (PSG), spin on glass (SOG), doped
• TEOS undoped TEOS
• SiOF fluorinated silicon oxide
• thermal oxide or other form
• the process of the invention is especially well suited for etching deep and
• This layer can be a metal such as Al, Ti, Cu, Mo or alloys
• a metal nitride such as titanium nitride, doped or undoped poly crystalline
• the underlying conductive material preferably excludes
• vacuum pressure can be set at 5 mTorr
• the power to the planar coil antenna outside the reactor can be set at 1300 Watts
• the in the electrostatic chuck can be set at 1700 Watts, and the helium supplied
• Figure 5 is a SEM micrograph of a structure etched with the following etching gas mixture: 200 seem
• Figures 6-9 are SEM micrographs of etched contacts wherein the photoresist layer has been removed.
• Figures 6 and 7 show center and edge profiles, respectively, of 0.25 ⁇ m diameter and 1.8 ⁇ m deep contact openings
• Table 1 sets forth results of etching dual-damascene structures using various reactor pressures, CH 2 F 2 , C 4 F 8 and CO gas flow rates .
• the optimal CO flow rate appears to be in the range of 50 to
• optimal etching gas mixture is CH 2 F 2 and C 4 F 8 in a ratio of 1 : 1 to 1.5 : 1. Also, reversed RIE lag is more likely to occur at low pressure settings.
• the process according to the invention was developed as a result of the
• Oxide etch rate uniformity measurements were determined from SEMs using the following formula: %
• Uniformity (feature size center - feature size edge)xl00/(feature size center +
• a preferred center point dielectric etching process using the LAM 9100PTXTM reactor is as follows: lOmTorr chamber pressure, 1300 Watts top electrode (TCP coil) power, 1500 Watts bottom electrode (ESC) power, 35 sccm CH 2 F 2 , 25 sccm C 4 F 8 and 200 sccm CO.
• the chamber pressure can range from 5 to 15 mTorr,
• the bottom electrode temperature can be about +20 °C, the helium supplied
• the CII F 2 flow rate can be at about 20 Torr
• the C 4 F 8 flow rate can range from 20 to 30 sccm and
• the CO flow rate can range from 150 to 250 sccm. While the foregoing reactor
• Figure 10 is a graph of TEOS etch rate versus CO flow
• the open area etch rates are at a maximum without CO additions and drops to near 0 as the CO flow rate increases to 200 sccm.
• Figure 11 is a graph of TEOS etch depth versus CO flow rate wherein the ⁇ indicate etch depth for the 0.4 ⁇ m openings. As shown in the graph, the etch depth of the openings increases gradually with CO flow rates up to 200 sccm.
• Figure 12 is a graph of Selectivities versus CO flow rate wherein the ⁇ indicate TEOS:Si 3 N 4 selectivity and the ⁇ indicate TEOS: Photoresist (PR)
• etching gas does not contain CO and the selectivity approaches 5 as the CO flow
• the TEOS:S ⁇ N 4 selectivity is below 10 without CO additions and increases to 15 as the CO flow rate increases
• Figure 13 is a graph of RIE lag versus CO flow rate wherein the ⁇ indicate the ratios of etch rates of 0.4 ⁇ m openings compared to open areas as CO

Landscapes

• Drying Of Semiconductors (AREA)
• Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

Family

ID=22589392

Family Applications (1)

Country Status (7)

Families Citing this family (26)

Citations (6)

Family Cites Families (20)

• 1998
  • 1998-09-30 US US09/163,301 patent/US6297163B1/en not_active Expired - Lifetime
• 1999
  • 1999-09-24 JP JP2000572915A patent/JP4499289B2/ja not_active Expired - Fee Related
  • 1999-09-24 EP EP99949628A patent/EP1121714A1/en not_active Withdrawn
  • 1999-09-24 WO PCT/US1999/020888 patent/WO2000019506A1/en not_active Ceased
  • 1999-09-24 KR KR1020017004035A patent/KR20010082216A/ko not_active Ceased
  • 1999-09-24 AU AU62463/99A patent/AU6246399A/en not_active Abandoned
• 2000
  • 2000-01-13 TW TW088116761A patent/TW584672B/zh not_active IP Right Cessation

Patent Citations (6)

Also Published As

Similar Documents

Legal Events