Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/46—Generating plasma using applied electromagnetic fields, e.g. high frequency or microwave energy
• • 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
  • H01J37/32137—Radio frequency generated discharge controlling of the discharge by modulation of energy
  • H01J37/32146—Amplitude modulation, includes pulsing
• • 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
  • H01J37/32137—Radio frequency generated discharge controlling of the discharge by modulation of energy
  • H01J37/32155—Frequency modulation
  • H01J37/32165—Plural frequencies
• • 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
  • H01J37/3244—Gas supply means
  • H01J37/32449—Gas control, e.g. control of the gas flow
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2242/00—Auxiliary systems
  • H05H2242/20—Power circuits
  • H05H2242/24—Radiofrequency or microwave generators

Definitions

• Plasma processing systems have long been employed to process substrates (e.g., wafers or fiat panels or LCD panels) to form integrated circuits or other electronic products.
• Popular plasma processing systems may include capacitively coupled plasma processing systems (CCP) or inductively coupled plasma processing systems (iCP), among other's.
• CCP capacitively coupled plasma processing systems
• iCP inductively coupled plasma processing systems
• plasma substrate processing involves a balance of ions and radicals (also referred to as neutrals).
• ions and radicals also referred to as neutrals.
• etching tends to be more chemical and isotropic.
• ions and radicals tends to he more physical and selectivity tends to suffer.
• ions and radicals tend to be closely coupled. Accordingly, the process window (with respect to processing parameters) tends to be fairly narrow due to the fact thai there are limited control knobs to independently achieve an ion-dominant plasma or a radical -dominant plasma.
• the source RF signal may be pulsed (e.g., on and off) in order to obtain a plasma that has the normal ion flux during one phase of the pulse cycle (e.g., the pulse on phase) and a plasma with lower ion flux during another phase of the pulse cycle (e.g., during the pulse off phase), it is known that source RF signal may be pulsed synchronously with bias RF signal.
• Fig. 1 shows, in accordance with one or more embodiments of the invention, an example combination pulsing scheme where the input gas (such as reactant gas and/or inert gas) and the source RF signal are both pulsed, albeit at different pulsing frequencies
• FIG. 2 shows, in accordance with one or more embodiments of the invention, another example combination pulsing scheme.
• Fig, 3 shows, in accordance with one or more embodiments of the invention, yet another example combination pulsing scheme.
• Fig. 4 shows, in accordaiice with one or more embodiments of the invention, other possible combinations for the combination pulsing scheme.
• FIG. 5 shows, in accordance with one or snore embodiments of the invention, the steps for performing combination pulsing.
• the invention might also cover articles of manufacture that includes a computer readable medium on which computer-readable instructions for carrying out embodiments of the inventive technique are stored.
• the computer readable medium may include, for example, semiconductor, magnetic, opto- magnetic, optical or other forms of computer readable medium for storing computer readable code.
• the invention may also cover apparatuses for practicing embodiments of the invention. Such apparatus may include circui ts, dedicated and/or programmable, to carry out tasks pertaining to embodiments of the invention. Examples of such apparatus include a general-purpose computer and/or a dedicated computing device when appropriately programmed and may include a combination of a
• Embodiments of the invention related to a combination pulsing scheme that pulses the input gas (e.g., reaciant gases and/or inert gases) using a first pulsing
• the input gas e.g., reaciant gases and/or inert gases
• the input gas isinstalled at a slower poising frequency, and the inductive source RF signal is poised at a different, faster pulsing frequency in an inductively coupled plasma processing system.
• the inductive source RF signal may be pulsed at, for example, 100 Hz while the gas isinstalled at a different pulsing rate, such as 1 Hz.
• a complete gas pulse cycle is 1 second in this example.
• the gas pulsing duty cycle is 70%, the gas may be on for 70% of the 1 -second gas pulsing period and off for 30% of the 1 -second gas pulsing period. Since the source RF signal pulsing rate is 100 Hz, a complete RF signal pulsing period is .10 ms. If the RF pulsing duty cycle is 40%, the RF on-phase (when the 13.56 MHz signal is on) is 40% of the 10 ms RF pulsing period and the RF off phase (when the 13.56 MHz signal is off) is 60% of the 10 ms RF pulsing period.
• the inductive source RF signal may be pulsed with two different frequencies while the gas is pulsed at its own gas pulsing frequency.
• the aforementioned 13.56 MHz RF signal may be pulsed not only at frequency f 1 of 100 Hz but may also be pulsed with a different, higher frequency during the on-phase of frequency f 1.
• the RF pulsing duty cycle is 40% of the fl pulse
• the on-phase of f! is 40% of ⁇ 0ms or 4ms.
• the RF signal may also be pulsed at a different, higher frequency of 12 (such as at 400 Hz).
• Embodiments of the invention contemplate that the gas pulses and RF pulses may be synchronous (i.e., with matching leading edge and/or lowering edge of the pulse signals) or may be asynchronous.
• the duty cycle may be constant or may vary in a manner that is independent of the other pulsing frequency or in a manner that is
• frequency chirping may be employed.
• the RF signal may change its fundamental frequency in a periodic or non- periodic manner so that during a phase or a portion of a phase of any of the pulsi ng periods (e.g.. any of the RF signal or gas pulsing periods), a different frequency (e.g., 60 MHz versus 13.56 MHz) may be employed.
• the gas pulsing frequency may be changed with time in a periodic or non-periodic manner if desired.
• the aforementioned gas and source RF pulsing may be combined with one or more pulsing or variation of another parameter (suc as pulsing of the bias RF signal, pulsing of the DC bias to the electrode, pulsing of the multiple RF frequencies at different pulsing frequencies, changing the phase of any of the parameters, etc.)
• Fig. I shows, in accordance with an embodiment of the invention, an example combination pulsing scheme where the input gas (such as reactant gas and/or inert gas) and the source RF signal are both pulsed, albeit at different pulsing frequencies.
• the input gas 102 is pulsed at a gas pulsing rate (defined as 1/T 3 ⁇ 45 , where T gP is the period of the gas pulse) of about 2 seconds/pulse or 2 MHz.
• the TCP source RF signal ! 04 of 13.56 MHz is pulsed at a RF pulsing rate (defined as ⁇ ⁇ , where 3 ⁇ 4 is the period of the RF pulsing).
• a RF pulsing rate defined as ⁇ ⁇ , where 3 ⁇ 4 is the period of the RF pulsing.
• the RF signal is on (such as the 13,56 MHz RF signal) during the time period 120 and the RF signal is off during the time period 122.
• Each of the gas pulsing rate and the RF pulsing rate may have its own duty cycle (defined as the pulse on-time divided by the total pulsing period). There are no requirements that the duty cycle has to be 50% for any of the pulse signals, and the duty cycle may vary as needed for a particular process.
• the gas pulsing and the RF signal pulsing are at the same duty cycle. In another embodiment, the gas pulsing and the RF signal pulsing are at independently controllable (and may be different) duty cycles to maximize granular control. In one or more embodiments, the leading and/or trailmg edges of the gas pulsing signal aud the RF pulsing signal may be synchronous, in one or more embodiments, the lead ing and ' or trai ling edges of the gas pulsing signal and the RF pulsing signal may be asynchronous. [00026] In Fig, 2, the gas input 202 is pulsed at its own gas poising frequency.
• the source .RF signal 204 may be pulsed with two different frequencies while the gas is pulsed at its own gas pulsing frequency (defined as 1 T W> where T g? is the period of the gas pulse).
• the RF signal may be pulsed not only at frequency fi (defined as l 'Tn from the figure) but may also he pulsed with a different, higher frequency during the on-phase of f! pulsing.
• the RF signal may be pulsed at a different pulsing frequency 12 (defined as 1 ⁇ ⁇ from the figure).
• the gas input 302 is pulsed at its own gas pulsing frequency.
• the source R.F signal 304 may be pulsed with three different frequencies while the gas is pulsed at its own gas pulsing frequency.
• the RF signal may be pulsed not only at frequency f l (defined as 1/Tn from the figure) but may also be pulsed with a different, higher frequency during the on-phase o f! pulsing.
• the RF signal may he pulsed at a differen pulsing frequency f2 (defined as !/3 ⁇ 4 from the figure.
• the RF signal may ⁇ be pulsed at a different pulsing frequency f3 (defined as l/T ⁇ from the figure).
• the duty cycle may also vary, in a periodic or non-periodic manner and independently or dependency on the phases of one of the pulsing: signals (whether gas pulsing signal, RF pulsing signal, or othenvise).
• the change in the duty cycle may be synchronous or asynchronous with respect to phase of any one of the pulsing signals (whether gas pulsing signal, RF pulsing signal, or otherwise).
• the duty cycle of the RF pulsing is advantageously set to be one value during the on-phase of the gas pulse (e.g., 154 in Fig. 1), and the duty cycle of the RF pulsing is set to he another different value during the off-phase of the gas pulse (e.g., 156 of Fig. 1 ).
• the duty cycle of the RF pulsing is advantageously set to be one value during the on-phase of the gas pulse (e.g., 154 in Fig. 1 ) and the duty cycle of the RF pulsing is set to be a lower value doting the off-phase of the gas pulse (e.g., 156 of Fig. I ).
• this RF pulsing duty cycle embodiment wherein the dirty-' cycle is higher during the on phase of the gas pul sing and lower during the off phase of the gas pulsing is advantageous for some etches. It is contemplated that this RF pulsing duty cycle variance wherein the duty cycle is lower during the on phase of the gas pulsing and higher during the off phase of the gas pulsing is advantageous for some etches. As the terra is employed herein, when a signal is poised, the duty cycle is other than 100% during the time when the signal is pulsed (i.e., pulsing and "always on" are two different concepts).
• frequency chirping may be employed with any of the pulsing signals (whether gas pulsing signal, RF pulsing signal, or otherwise).
• Frequenc chirping is described in greater detail in connection wit the RF pulsing signal in Fig. 4 below.
• the gas is pulsed such that during the gas pulsing on phase, reactant gas(es) and inert gas(es) (such as Argon, Helium, Xenon, Krypton, Neon, etc.) are as specified by the recipe.
• reactant gas(es) and inert gas(es) such as Argon, Helium, Xenon, Krypton, Neon, etc.
• inert gas(es) such as Argon, Helium, Xenon, Krypton, Neon, etc.
• the reactant gas(es) and inert gas(es) may be removed.
• at least some of the reactant gas(es) is removed and replaced by inert. gas(es) during the gas pulsing off phase.
• at least some of the reactant gasies) is removed and replaced by inert gas(es) during the gas pulsing off phase to keep the chamber pressure substantially the same.
• the percentage of inert gas(es) to total gasies) flowed into the chamber may vary .from about X% to about 100%, wherein X is the percentage of inert gas(es) to total gas flow that is employed during the gas pulsing on phase, hi a more preferred embodiment, the percemage of i nert gas(es) to total gas(es) flowed into the chamber may vary from about 1.1 X to about 100%, wherein X is the percentage of inert gas(es) to total gas flow that is employed during the gas pulsing on phase.
• the percentage of inert gas(es) to total gas(es) flowed into the chamber may vary from about 1.5 X to about 100%, wherein X is the percentage of inert gasies) to total gas flow that is employed during the gas pulsing on phase,
• the gas pulsing rate is limited at the high end (upper frequency limit) by the residence time of the gas in the chamber.
• This residence time concept is one that is known to one skilled in the art and varies from chamber design to chamber design. For example, residence time typically ranges in the tens of milliseconds for a capaciiively coupled chamber, hi another example, residence time typically ranges in the tens of milliseconds to hundreds of milliseconds for an inductively coupled chamber.
• the gas pulsing period may range from 1.0 milliseconds to 50 seconds, more preferably from 50 milliseconds to about 10 seconds and preferably from about 500 milliseconds to about 5 seconds.
• the source RF pulsing period is lower than the gas pulsing period in accordance with embodiments of the invention.
• the RF pulsing frequency is limited at the upper end by the frequency of the RF signal (e.g., 13.56 MHz would establish the upper limit for the RF pulsing frequency if the RF frequency is 33.56 MHz).
• Fig. 4 shows, in accordance with one or more embodiments of the invention, other possible combinations.
• another signal 406 (such as bias RF or any other periodic parameter) may be pulsed along with gas pulsing signal 402 and source RF poising signal 404 (pulsed as shown with 430 and 432).
• the pulsing of signal 406 may be made synchronous or asynchronous with any other signals in the system.
• another signal 408 (such as DC bias or temperature or pressure or any other non-periodic parameter) may be pulsed along with gas pulsing signal 402 and source RF pulsing signal 404, The pulsing of signal 408 may be made synchronous or asynchronous with any other signals in the system.
• another signal 4.10 (such as RF source or RF bias or any other non -periodic parameter) may be chirped and pulsed along with gas pulsing signal 402.
• the frequency of signal 410 may vary depending on the phase of signal 410 or another signal (such as the gas pulsing signal) or in response to a control signal from the tool control computer.
• reference 422 points to a region of higher frequency than the frequency associated with reference number 420.
• An example of a lower frequency 422 may be 27 MHz and a higher frequency 420 may be 60 FIz. The pulsing and.
• FIG. 5 shows, in accordance with an embodiment of the invention, the steps for per forming combi n at ion pulsing.
• the steps of Fig. 5 may be ex ecut ed via software under control of one or more computers, for example.
• the software may be stored in a computer readable medium, including a non-transitory computet readable medium io one or more embodiments.
• step 502 a substrate is provided in a plasma processing chamber.
• the substrate is processed while pulsing both the RF source and the input gas.
• step 506 Optional pulsing of one or more other signals (such as RF bias or another signal) is shown i step 506.
• the frequency, duty cycle, gas percentages, etc. may optionally be varied while poising the RF source and the input gas.
• Embodiments of the invention may also employ one or more of the gas pulsing techniques as disclosed in a commonly owned co-pending patent applicatio entitled “Inert-Dominant Pulsing In Plasma Processing System," Attorney Docket No. P2337P/LMRX-P226P1 , filed on even date and incorporated by reference herein
• embodiments of the invention pro vide another control knob that can widen the process window for etch processes. Since many current plasma chambers are already provided with pulsing valves or pulsing mass flow controllers, as well as pulse-capable RF power supplies, the ach ievement of a wider process window may be obtained without requiring expensive hardware retrofitting. Current tool owners may leverage on existing etch processing systems to achieve improved etches with minor software upgrade and/or minor hardware changes. Further, by having improved and/or more granular control of the ion-to-radical flux ratios, selectivity and uniformity and reverse RLE lag effects may be improved.
• ALE atomic layer etch
• inert gas substitution may be practiced with techniques discussed with any one or pari of any one or a combination of multiple ones) of the figures and/or with duty cycle variance and/or with frequency chirping.
• techniques axe discussed individually and/or in connection with a specific figure, the various techniques can be combined in any combination in order to perform a particular process.

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• 2012
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