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
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
  • H01L21/3105—After-treatment
  • H01L21/311—Etching the insulating layers by chemical or physical means
  • H01L21/31127—Etching organic layers
  • H01L21/31133—Etching organic layers by chemical means
  • H01L21/31138—Etching organic layers by chemical means by dry-etching
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/42—Stripping or agents therefor
  • G03F7/427—Stripping or agents therefor using plasma means only

Definitions

• This invention relates to the cleaning and stripping of photoresist from surfaces of semiconductor wafers during manufacturing. _.
• photolithography steps and etching, thin film deposition, and/ox ion implantation steps are alternately performed to build up the of the devices.
• the photolithography steps typically include steps of coating a wafer with a photoresist, typically an ultraviolet ⁇ Wt$ photosensitive organic material; exposing the photoresist through a mask; developing the resist; and etching the exposed resist to leave certain exposed areas on the wafer surface. Further processing steps, such as deposition, implantation, or etching can then be employed on the exposed areas.
• Etching is typically performed with either a wet etching process in which the wafers are immersed in a chemical etchant; or a dry etching process, such as downstream microwave plasma etching or reactive ion etching (RIE) . After photoresist is patterned on a surface and after further processing steps are performed in exposed areas, the photoresist is stripped. , hinge;
• Microwave downstream processing can be performed with 0 atomic oxygen to strip resist when wafers cannot tolerate electrical damage. Because atomic oxygen is very chemically reactive, however, it can recombine very rapidly on the surface of a metal, such as aluminum that may be used in chambers for cleaning and stripping. The nature of these ⁇ reactions, and the factors that influence the effects, are not well understood, so manufacturers have been discouraged
• a trace amount means less than about 0.5%, and preferably about 0.1% to 0.2%.
• This process can be combined with additional microwave downstream processes or RIE processes. This process can be used to achieve high ashing rates in an aluminum chamber with reliable performance, independent of variations in the aluminum surface.
• FIG. 1 is a partial pictorial, partial block diagram of an apparatus for etching and stripping.
• Fig. 2 is a graph comparing ashing rates and oxide loss for different processes.
• a semiconductor wafer 10 to be processed is positioned over a horizontally disposed hotplate 12 in an enclosed treatment chamber 16 for etching and/or cleaning.
• Wafer 10 which is typically flat and circular with a diameter of four to eight inches, rests horizontally on support pins 18 that extend through openings in hotplate 12 along its thickness direction.
• WaferJLO and hotplate 12 thus lie in parallel horizontal planes, *
• a process gas is introduced into chamber 16 from a gas source 20 through an inlet pipe 21.
• a microwave source 22 at inlet pipe 21 causes a microwave plasma 24 to be fotmed at the inlet pipe, thus discharging a reactive gas 2f*with a high concentration of active free radicals.
• Gas 26 passes through openings (not shown) in a top electrode 28 that is mounted above the wafer and is configured as in the incorporated patent. Under appropriate conditions, these active free radicals can thus decompose and evaporate?A resist film on wafer 10 by converting the resist to g&t ⁇ es .
• a vacuum 32 draws away these gases through an exhaust ⁇ tube 34, and also maintains pressure on the order of 50-2000 mTorr in the chamber.
• An RF source 30 is electrically coupled to top electrode 28 and to hotplate 12, which serves as a bottom electrode. Electrodes 28 and 12 thus form a double cathode. Source 30 provides an RF voltage that causes an RF plasma 32 to form over wafer 10. RF plasma 32 creates reactive ions that ash the resist from wafer 10.
• a transparent cover 48 and an end point detector 50 are used to detect when ashing caused by the RF plasma begins and ends.
• End point detector 50 has a filter and an optical detector for detecting photons that are released in the RF plasma when OH radicals are formed during ashing.
• a gas can be introduced from gas source 20 while f microwave source 22 is activated to produce reactive gas 26 having a high concentration of free radicals discharged from the microwave plasma.
• An RF plasma can then be generated in the microwave-generated reactive gas 26 to ionize its free radicals.
• a process gas from gas sowce 20 includes CF 4 and oxygen
• the discharged gas from the microwave plasma has a high concentration of fluorine and oxygen radicals, respectively, in the gas over the wafer.
• an RF plasma is then initiated in this discharge gas, the resulting ions that are produced are different from those in either the microwave discharge gas itself or from an RF plasma of CF and oxygen gas without the microwave discharge. This different plasma has been found to s substantially increase ashing during either etching or stripping.
• Chamber 16 thus can be used to perform dry ashing with a downstream microwave process, an RIE process, both of these processes simultaneously, or both of these processes o sequentially and/or alternatively.
• This process can be performed “cold, " meaning at about 100'C or less; or “hot”, meaning at least at about 150'C.
• the fluorine about 1%-10%, reacts with hydrogen in the 25 resist to form HF that can be exhausted from the chamber; however, the reaction of fluorine and hydrogen also creates reactive sites on the resist surface where atomic oxygen can then react and ash at low temperature .
• An embodiment of the NoHal process has the following 30 process variables:
• LoHal a process that has process variables similar to NoHal, except that LoHal uses a small amount of a fluorine containing gas, such as CF , NF , or SF , preferably less than about 0.5%, and more preferably about 0.1% to 0.2%.
• a fluorine containing gas such as CF , NF , or SF
• Preferred process conditions are as follows:
• LoHal has an ashing rate of about 2.5 to about 3 microns per minute, and up to almost 3.5 microns per minute when redone. This rate is about 2-3 times higher than the rate under a similar NoHal process. Because the quantity of fluorine is so small, no substantial etching of sensitive films, such as SiO and Si N , has been observed. In these tests, the oxide loss was less than 3 angstroms per minute, even after a repeat test.
• the fluorine By monitoring optical emissions to measure oxygen radicals, the amount of oxygen radicals increased with a small amount of fluorine, suggesting that the fluorine prevents oxygen from attaching to the surface of the chamber and other components in the chamber. Thus it is believed that the fluorine passivates the surfaces in the chamber.
• the LoHal process can be combined with other dry processes before or after the LoHal process.
• a LoHal process can be followed by a Hal process, a reactive ion etching (RIE) process, or by a Hal process followed thereafter by an RIE process.
• RIE reactive ion etching
• etching following a damascene process channels are etched in a silicon oxide prior to the deposition of metal to achieve fine-line metal definition and to eliminate the subtractive process of conventional etching of aluminum metal. It has been found, however, that etching in the oxide channel results in contamination of a resist mask with the formation of polymers that are difficult to remove, even with the aid of solvents. According to a process for removing such resist, and RIE plasma with oxygen is first utilized in order to break up and ash away a highly fluorinated skin that can form on the resist surface during the etching process. When this skin has been removed, a LoHal process is employed to ash away remaining organic materials. The remaining residues can then be rinsed away with deionized (DI) water to leave a clean surface.
• DI deionized

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Plasma & Fusion (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Drying Of Semiconductors (AREA)

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Publications (2)

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• 1996
  • 1996-04-24 US US08/637,137 patent/US5908319A/en not_active Expired - Lifetime
• 1997
  • 1997-04-23 JP JP53827097A patent/JP4562813B2/ja not_active Expired - Lifetime
  • 1997-04-23 WO PCT/US1997/006691 patent/WO1997040423A2/en not_active Ceased

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