Classifications

• • 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
  • G03F7/34—Imagewise removal by selective transfer, e.g. peeling away
• • 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
• • 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
  • G03F7/36—Imagewise removal not covered by groups G03F7/30 - G03F7/34, e.g. using gas streams, using plasma
• • 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
• • 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
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70008—Production of exposure light, i.e. light sources
  • G03F7/70033—Production of exposure light, i.e. light sources by plasma extreme ultraviolet [EUV] sources
• • 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
  • H10P50/24—Dry etching; Plasma etching; Reactive-ion etching of semiconductor materials
  • H10P50/242—Dry etching; Plasma etching; Reactive-ion etching of semiconductor materials of Group IV 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
  • H10P50/286—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of organic materials
  • H10P50/287—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of organic 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
  • H10P70/00—Cleaning of wafers, substrates or parts of devices
  • H10P70/10—Cleaning before device manufacture, i.e. Begin-Of-Line process
  • H10P70/15—Cleaning before device manufacture, i.e. Begin-Of-Line process by wet cleaning only

Definitions

• FIG. 1 A first figure.
• the invention relates to the fabrication of integrated circuits and more particularly to removing photoresist from an integrated circuit by using a non-oxygen gas or low oxygen gas plasma process.
• VLSI very large scale integrated
• the interconnection structure consists of thin conductive lines separated by insulation (silicon dioxide) in one layer or level and connected to elements of the semiconductor chip or to a similar layer in another level. Vias or studs extend through the insulation and can be connected to contacts associated with the elements of the semiconductor chip. Connections between levels or layers and between layers and the elements of the semiconductor chip are then made.
• Conventional ultra-large scale integrated (ULSI) circuit devices can include five or more layers.
• the interconnection structure associated with VLSI and ULSI circuits is similar to a transmission line in that there is a propagation delay of the signals being transmitted in these wiring layers.
• the delay is referred to as RC delay because it generally relates to the resistance (R) of the material of the wire and the capacitance (C) between adjacent wires.
• Capacitance (C) is the product of dielectric constant (k) of the insulating material times the area (A) of the opposing faces of the conductive line divided by the distance (D) between the conductive lines ( c _ j ⁇ . With a decrease in distance (D), the capacitance (C) increases. Since
• low-k dielectric materials dielectric materials having low dielectric constants
• a disadvantage to using low-k dielectric materials is that traditional photoresist removal processes (e.g., ashing and solvent cleaning) causes degradation of most low-k dielectric materials.
• photoresist removal on low-k dielectric materials such as, hydrogen silsesquioxanes (HSQ), spin on glass (SOG), benzocyclobutine (BCB), etc., causes the dielectric constant (k) to increase.
• HSQ hydrogen silsesquioxanes
• SOG spin on glass
• BCB benzocyclobutine
• the conventional solvent cleaning of the integrated circuit after the ashing process typically causes further degradation of low-k dielectrics and causes increases in dielectric constant k.
• the present invention relates to a method of photoresist removal from an integrated circuit wafer.
• the method includes exposing the wafer to a plasma.
• the forming gas of the plasma is substantially free of oxygen gas (O 2 ) and removes photoresist from the integrated circuit wafer.
• the method also includes removing the remaining photoresist from the wafer using a solvent and degassing the integrated circuit wafer.
• the present invention also relates to a method of photoresist removal from an integrated circuit wafer.
• the method includes providing an integrated circuit having a layer of photoresist overlying a dielectric stack.
• the method also includes placing the integrated circuit in a substantially pure plasma to remove photoresist from the integrated circuit wafer.
• the present invention still further relates to an integrated circuit.
• the integrated circuit includes a dielectric stack having a first insulative layer, a second insulative layer and a third insulative layer, the second insulative layer being a low-k dielectric layer between the first insulative layer and the third insulative layer.
• a via extends through the dielectric stack and the lateral sides of the second layer of the dielectric stack includes a protective layer.
• FIG. 1 is a cross sectional view of a portion of an integrated circuit having a top layer of photoresist
• FIG. 2 is a cross sectional view of the integrated circuit of FIG. 1 having some of the photoresist of FIG. 1 selectively removed;
• FIG. 3 is a cross sectional view of the dielectric stack illustrated in FIG. 2 having a via etched through the dielectric layers;
• FIG. 4 is a cross sectional view of the integrated circuit of FIG. 3 depicting the integrated circuit with the photoresist removed.
• Integrated circuit wafer 10 includes a silicon substrate 14, a low-k dielectric layer 16, a conductive metal layer 18, an oxide layer 20, a low-k dielectric layer 22, an oxide layer 24, and a photoresist layer 26.
• Silicon substrate 14 is typically a single crystal silicon wafer having a thin layer of silicon dioxide on its outermost surface 15.
• substrate 14 may be a silicon dioxide (Si0 2 ) substrate, a gallium arsenide (GaAs) substrate, or other insulating materials.
• Low-k dielectric layer 16 is deposited over silicon substrate 14.
• Low-k dielectric layer 16 is a thin layer of low-k material, having a thickness of approximately 200 Angstroms, or alternatively any suitable thickness.
• Low-k dielectric layer 16 may be a spin on deposit of materials such as HSQ, SOG, BCB or other suitable materials. The low-k dielectric materials are deposited using spin on deposit techniques in which the materials are dissolved in a solvent and spun on to integrated circuit wafer 10. Alternatively, chemical vapor deposition (CVD) techniques can be used or any other deposition techniques that are known to those of ordinary skill in the art of semiconductor fabrication.
• CVD chemical vapor deposition
• Conductive metal layer 18 is deposited over low-k dielectric layer 16.
• Conductive layer 18 may be deposits of aluminum (Al), copper (Cu), gold (Au), tungsten (W), or alloys including these metals or polysilicon.
• Conductive metal layer 18 may be deposited by evaporation methods, such as physical vapor deposition (PVD), sputtering or plating. Evaporation methods use heat and high- vacuums to cause vaporization of a metal source. The vaporized metal material condenses on the cooler wafer surface. Sputtering techniques are well known in the art and use a plasma to bombard a metal source. The dislodged metal molecules are then deposited onto the wafer.
• oxide layer 20 is deposited utilizing for example a tetraethylorthosilane (TEOS) process or other suitable processes known to those of ordinary skill in the art.
• TEOS tetraethylorthosilane
• silicon dioxide or other suitable materials can be deposited as oxide layer 20.
• Low-k dielectric layer 22 is then deposited over oxide layer 20, similar to low-k dielectric layer 16.
• a cap layer 24 (usually an oxide layer) is then deposited over low-k layer 22, similar to oxide layer 20.
• Layers 24, 22, and 20 form a dielectric stack.
• the dielectric stack may be a single insulating layer of low-k dielectric 22 or any suitable combination of dielectric layers.
• Photoresist layer 26 is a layer of photoresist or mask material, which is a photosensitive material, that is applied over oxide layer 24 in a liquid state in relatively small quantities. The wafer is spun at approximately 3,000 RPMs spreading the photoresist material into a uniform layer, typically between 0.15 and 200 micrometers ( ⁇ m) thick. Two types of photoresist may be used, the two types being negative photoresist and positive photoresist.
• a negative photoresist causes unexposed portions of the photoresist to be removed leaving a "negative image".
• Negative photoresist is typically only capable of producing features down to about 2 ⁇ m.
• Most conventional semiconductor processes today use a positive resist where exposed portions are removed leaving a "positive image" of the masked pattern on the surface of the wafer.
• Positive resists are more capable of producing the small size of modern device features which are typically below 1 ⁇ m but may be as small as 0.15 ⁇ m.
• photoresist layer 26 is deposited on oxide layer 24, photoresist layer 26 is masked. If a positive resist is used, the portions which are not to be removed are masked. The masked wafer is then exposed to high intensity ultra-violet light. The ultra-violet light causes the exposed photoresist to undergo a chemical change, becoming more acidic. Once the wafers have been developed by exposure, the wafers are etched either in an acid or base solution to remove (or strip) the exposed areas of the photoresist. The wafer is then heated at a low temperature which hardens the remaining photoresist 26. With reference to FIG. 2, this developing and stripping procedure leaves a pattern of channels 30 in the photoresist 26.
• Via 32 can be created by dry etching. Via 32 will be used to create a post contact to interconnect conductive metal layer 18 with another layer of device 10, such as a layer (not shown) above layer 24.
• photoresist 26 may be removed.
• ashing or photoresist removal
• Wafer 10 is exposed to a high temperature plasma that selectively removes photoresist 26 without damaging conductive lines 18, oxide layer 20, low-k dielectric layer 22, or oxide layer 24.
• the plasma used is non-oxygen forming gas plasma.
• a non-oxygen forming gas plasma may be used that contains up to 20% of combined hydrogen gas (H 2 ) and nitrogen gas (N 2 ).
• photoresist layer 26 has a thickness on the order of 1 ⁇ m
• wafer 10 should be exposed to the plasma for approximately 4-10 minutes at a temperature of 250-270°C to complete the photoresist removal.
• other plasma forming gasses may be used having either no O? or a trace amount of 0 2 (less than 5%) and the exposure times and temperatures should be varied accordingly.
• plasmas that are suitable for use are plasmas that do not degrade the low-k properties in the dielectric layer.
• other plasma forming gasses that may be suitable are H 2 + N 2 + trace
• Plasmas from forming gasses in this class may be characterized as substantially pure plasmas, i.e., plasmas having an 0 2 content less than about 5% so that the oxygen does not cause reaction with the low-k dielectric which would substantially raise the k value thereof.
• the plasma it is also desirable for the plasma to create a protective layer on surface 23 of low-k dielectric material 22.
• the protective layer is created during exposure of layer 22 to the plasma. Exposure of low-k dielectric layer 22 to the conditions present during plasma ashing causes a physical or chemical change to surface 23 of low-k dielectric 22.
• This protective layer provides a protective block such that 0 2 plasma photoresist ashing solvent and photoresist removal solvent does not easily penetrate the protective layer and further degrade the low-k dielectric layer.
• a thicker protective layer provides better protection from solvent attack of low-k dielectric layer 22. Therefore, low dielectric constants of layer 22 are maintained. If a pure 0 plasma is used to remove photoresist layer 22, the low-k dielectric layer is degraded or removed.
• wafer 10 is deposited in a solvent that removes any remaining photoresist from wafer 10.
• a solvent that removes any remaining photoresist from wafer 10.
• exposing low-k dielectric layer 22 to many solvents will cause degradation of low-k dielectric layer 22 and will cause a significant rise in the dielectric constant (k) (as the dielectric constant of water is 85). Therefore, it is desirable to use a photoresist ashing process, as described above, that provides a protective layer over low-k dielectric layer 22 in advance of the solvent cleaning process.
• a degassing process is used to remove any trace photoresist and eliminate any moisture.
• the degassing process includes placing integrated circuit wafer 10 in a vacuum, such that the solvent and any trace photoresist is evaporated.
• the degassing process may be accomplished by exposing integrated circuit wafer 10 to high temperature (i.e., heating integrated circuit wafer 10) alone or in combination with exposing integrated circuit wafer 10 to a vacuum.
• the resulting device 10 is depicted in FIG. 4 having a via 32 extending through insulative layers 24, 22, and 20 and being terminated at conductive metal layer 18, where a post contact may be deposited in a next processing step.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Drying Of Semiconductors (AREA)
• Internal Circuitry In Semiconductor Integrated Circuit Devices (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (13)

Families Citing this family (34)

Citations (4)

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• 1999
  • 1999-07-07 US US09/349,055 patent/US6235453B1/en not_active Expired - Lifetime
• 2000
  • 2000-03-13 WO PCT/US2000/006603 patent/WO2001004707A1/en not_active Ceased
  • 2000-03-13 KR KR1020027000179A patent/KR100682639B1/ko not_active Expired - Lifetime
  • 2000-03-13 EP EP00914955A patent/EP1192506B1/en not_active Expired - Lifetime
  • 2000-03-13 JP JP2001510054A patent/JP4557479B2/ja not_active Expired - Lifetime

Patent Citations (4)

Non-Patent Citations (2)

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