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
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/76—Making of isolation regions between components
  • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
• • 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
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/76—Making of isolation regions between components
  • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
  • H01L21/76202—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO
  • H01L21/76221—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO with a plurality of successive local oxidation steps
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10B—ELECTRONIC MEMORY DEVICES
  • H10B69/00—Erasable-and-programmable ROM [EPROM] devices not provided for in groups H10B41/00 - H10B63/00, e.g. ultraviolet erasable-and-programmable ROM [UVEPROM] devices

Definitions

• the present invention relates to an integrated circuit or semiconductor device. More particularly, the present invention relates to a fabrication method for creating thin and thick isolation structures on a semiconductor substrate.
• LOCOS local oxidation of silicon
• LOCOS typically involves growing a pad oxide or liner oxide, depositing a hard mask layer over the liner oxide, etching the hard mask layer, and growing an oxide isolation structure.
• the hard mask layer can be a nitride film.
• the oxide structure can be grown by heating the substrate.
• Isolation regions or structures for semiconductor devices can vary in size depending on parameters or requirements necessary for proper electric isolation and charge carrier isolation.
• memory devices such as, flash electrical erasable programmable read only memories (flash EEPROMS)
• flash EEPROMS flash electrical erasable programmable read only memories
• core areas e.g. , the memory cell array
• certain areas of the semiconductor device can require large isolation structures while other areas can require small isolation structures due to different voltage requirements, dopant types, increased circuit packing density, dopant concentrations, or other criteria associated with IC design.
• semiconductor devices such as, flash memories generally have utilized thick LOCOS structures in peripheral regions and thin LOCOS structures require two separate critical masks to define the oxide structures which are grown in two separate selective oxidation processes.
• a conventional process for forming thin and thick oxide structures is described as follows.
• a semiconductor structure device 12 includes a core region 8 and a peripheral region 9 separated by an interface 10.
• Structure 12 includes a substrate or base 14, a pad oxide layer 16, and a nitride layer 18.
• Structure 12 is first etched in accordance with a preliminary mask or zero layer mask (not shown) for defining alignment marks.
• a source drain mask layer 20 is provided over layer 18 to define source and drain regions in peripheral region 9.
• Layer 20 completely covers core region 8.
• structure 12 is etched to remove layer 18 from portions of region 9 in accordance with layer 20.
• layer 20 is stripped from structure 12, and structure 12 is oxidized to form LOCOS isolation structure 24 in accordance with a conventional LOCOS technique. During this step, layer 18 in core region 8 is also oxidized. Additionally, LOCOS structure 24 is relatively thin at boundary or interface 10 with respect to the remaining portion of peripheral region 9.
• a source drain mask layer 26 is applied to define source and drain regions in core region 8 as well as isolation structures for core region 8.
• structure 12 is etched in accordance with layer 26 to remove portions of layer 18 in core region 8.
• portions of structure 24 close to interface 10 can be etched because layer 26 does not reach interface 10 ( Figure 4).
• the etching of structure 12 can thin the thickness of structure 24 in peripheral region 9. This thinning can cause a step 28 and a groove 30.
• the thickness of structure 24 can be less than 1300 A at step 28.
• isolation structures 40 and 42 are grown in a thermal process in accordance with a conventional LOCOS technique. Step 28 and groove 30 remain on structure 10.
• the thickness of structure 28 can be less than 1000 A at groove 28.
• Step 28 and groove 30 can cause residue or "stringer” problems during subsequent first polysihcon, oxygen-nitride-oxygen (ONO), second polysihcon and self-aligned etched (SAE) processes.
• Conductive material trapped in step 28, groove 30 can create unintentional gate structures due to the thinness of structure 24 or can electrically short adjacent structures.
• layer 18 is subjected to two oxidation steps which can create "oxide bumps" on top of "bird beaks" associated with structures 40 and 42.
• the oxide bumps can be due to material surface stress of layer 18 which is caused by the dual oxidation process associated with the formation of structures 24, 40 and 42.
• Step 28 can also create a "race track” topography problem related to the difference in thickness of structure 24 at interface 10.
• the race track topography problem is manifested when photoresist is provided on structure 12 and includes grooves or lanes in a race track form.
• the present invention relates to a method of fabricating an integrated circuit having a core area, an interface area and a peripheral area.
• the interface area is between the core area and the peripheral area, and the peripheral area has at least one thick LOCOS structure.
• the core area has at least one thin LOCOS structure.
• the thin LOCOS structure and the thick LOCOS structure are formed in a semiconductor substrate.
• the semiconductor substrate includes a first hard mask layer disposed above the substrate.
• the method includes a first etch resist layer over the first hard mask layer, etching the first hard mask layer in accordance with first etch resist layer, growing the thin LOCOS structure, stripping the first hard mask layer, and providing a second hard mask layer over the core region.
• the first etch resist layer defines the thin LOCOS structure.
• the present invention further relates to a method of fabricating at least one first isolation region and at least one second isolation region on a semiconductor substrate.
• the semiconductor substrate includes a pad oxide layer disposed above the substrate and a first hard mask layer disposed above the pad oxide layer.
• the method includes the steps of etching the first hard mask layer, forming the first isolation region by oxidizing the substrate, removing the first hard mask layer, and providing a second hard mask layer.
• the present invention still further relates to a method of fabricating a semiconductor device on a semiconductor, the method includes providing a first nitride layer over a semiconductor substrate, selectively etching the first nitride layer at a plurality of first locations, forming a plurality of first oxide isolation structures at the first locations, providing a second nitride layer over the semiconductor substrate, selectively etching the second nitride layer at a plurality of second locations, and forming a plurality of second oxide isolation structures at the second locations.
• selective oxidation structures are provided in a core region and a peripheral region of an integrated circuit (IC).
• Thick oxidation structures are provided in the peripheral region, and thin oxidation structures are provided in the core region.
• Two separate hard mask layers, such as, nitride layers, are utilized to define the thin and thick oxidation structures.
• the thin oxidation structures in the core region are formed first following by the thick oxidation structures in the peripheral region.
• selective oxidation by LOCOS is utilized for thick and thin LOCOS isolation regions in a peripheral region and core region, respectively, of a semiconductor substrate.
• An interface region between the core region and peripheral region preferably has relatively even isolation (e.g., without significant step downs or grooves) due to the advantageous fabrication technique.
• the advantageous process reduces residue or "stringer” problems.
• the advantageous fabrication process is less susceptible to "oxide bumps" formed on oxidation structures in the core region and reduces the potential for photo resist "race track” problems.
• boron segregation into the field oxide is reduced or eliminated because the integrated circuit is implanted with boron after the formation of the field oxide.
• FIGURE 1 is a cross-sectional view of a semiconductor device illustrating a first step in a conventional LOCOS formation process
• FIGURE 2 is a cross-sectional view of the semiconductor device shown in FIGURE 1 illustrating a second step in the conventional LOCOS formation process;
• FIGURE 3 is a cross-sectional view of the semiconductor device shown in FIGURE 2 illustrating a third step in the conventional LOCOS formation process
• FIGURE 4 is a cross-sectional view of the semiconductor device shown in FIGURE 3 illustrating a fourth step in the conventional LOCOS formation process
• FIGURE 5 is a cross-sectional view of the semiconductor device shown in FIGURE 4 illustrating a fifth step in the conventional LOCOS formation process
• FIGURE 6 is a cross-sectional view of the semiconductor device shown in Figure 5 illustrating a sixth step in the conventional LOCOS formation process
• FIGURE 7 is a cross-sectional view of a semiconductor structure including thin isolation structures in a core region and thick isolation structures in a peripheral region in accordance with an exemplary embodiment of the present invention
• FIGURE 8 is a cross-sectional view of the semiconductor structure shown in Figure 7 illustrating a first step in the method utilized to manufacture the semiconductor structure;
• FIGURE 9 is a cross-sectional view of the semiconductor structure shown in Figure 8 illustrating a second step in the method utilized to manufacture the semiconductor structure
• FIGURE 10 is a cross-sectional view of the semiconductor structure show in in Figure 9 illustrating a third step in the method utilized to manufacture the semiconductor structure
• FIGURE 11 is a cross-sectional view of the semiconductor structure shown in Figure 10 illustrating a fourth step in the method utilized to manufacture the semiconductor structure;
• FIGURE 12 is a cross-sectional view of the semiconductor structure shown in Figure 11 illustrating a fifth step in the method utilized to manufacture the semiconductor structure; and
• FIGURE 13 is a cross-sectional view of the semiconductor structure shown in Figure 12 illustrating a sixth step in the method utilized to manufacture the semiconductor structure.
• a semiconductor device or structure 112 includes a core region 108, an interface region 110, and a peripheral region 109.
• Structure 112 includes a substrate or a base 114, an oxide isolation structure 146, and an oxide isolation structure 148.
• Structure 112 can be any type of semiconductor device or portion thereof made from any of the various semiconductor processes, such as, complimentary metal oxide semiconductor (CMOS) process, bipolar process, or other semiconductor processes. Structure 112 is shown in Figure 7 before other components and structures, such as, polysihcon layers, insulating layers and metal layers are provided.
• CMOS complimentary metal oxide semiconductor
• Semiconductor structure 112 may be an entire or a portion of an integrated circuit (IC) including a multitude of electronic components.
• Base 114 of semiconductor structure 112 is preferably silicon or other semiconductor structure 112 and can be doped with P-type dopants or N-type dopants.
• Structure 112 can include CMOS transistors fabricated in N-type and P-type wells.
• structure 112 is at least a portion of a memory device, such as, a flash EPROM.
• the memory device includes memory cells provided in core region 108 and input/output or drive circuitry in peripheral region 109.
• Core region 108 is a low voltage region (e.g. , 2.7V or less).
• Peripheral region 109 is preferably a higher voltage region (e.g., 3.3V or higher) including drive circuitry.
• Interface region 1 10 is adjacent a border 11 1 between regions 108 and 109.
• Core region 108 includes isolation structures 146 and 148, and peripheral region 109 includes isolation structures 142 and 144.
• Structures 146 and 148 are preferably thin LOCOS structures having a thickness of 2,000 angstroms (A).
• Structures 142 and 144 are preferably thick LOCOS structures having a thickness of 4,000 A.
• Structure 142 extends across interface region 110 and into region 108. Structures 142, 144, 146 and 148 are grown in selective thermal
• System parameters and design requirements can define the various dimensions for structures 142, 144, 146 and 148. For example, as the size and spacing of transistors integrated within and above base 114 decrease, the width and depth of structure 142, 144, 146 and 148 can likewise decrease. Further, as voltage parameters change for the functional units integrated in base 1 14, the dimensional relationships of isolation structures 142, 144, 146 and 148 can also change. Thus, system configurations and fabrication parameters associated with the design of structure 112 can serve to define the dimensions of structures 142, 144, 146 and 148, as well as, regions 108, 109 and 110.
• semiconductor structure 112 includes substrate layer or base 114, an oxide film or pad oxide layer 116, and a nitride layer 118.
• Base 114 is preferably silicon (Si) and can be doped with phosphorous for N-type wells or boron for P-type wells and is significantly thicker than layers 1 16 and 118.
• Pad oxide layer 116 is grown on top of base 1 14 to a thickness of approximately 150-250 A by a thermal process.
• Nitride layer 1 18 is deposited as a 1 ,700 A thick layer by chemical vapor deposition (CVD) on top of pad oxide layer 116.
• CVD chemical vapor deposition
• layers 116 and 118 may be deposited by physical vapor deposition (PVD), sputtering deposition, collimated sputtering deposition, dipping, evaporating, or other application techniques.
• Nitride layer 118 is a hard mask layer.
• Layer 118 is comprised of silicon nitride (Si 3 N 4 ) and serves to prevent oxidation of underlying substrate 114.
• Layer 118 is also an anti-reflective coating.
• Pad oxide layer 116 provides stress relief between base 114 and layer 118 for structure 112.
• layer 118 can be any hard mask layer.
• an etch resist layer 152 is selectively applied on top of layer 118.
• Etch resist layer 152 is preferably a photoresist layer which defines spacings 154 for structures 142, 146 and 148. Unlike conventional processes, well regions are not yet defined in regions 108 and 109. Structure 112 can be etched by dry etching (e.g. , plasma etching) to form spacings 156 in layer 118
• FIGURE 10 This etching of structure 112 can also serve to define alignment marks for structure 112, thereby eliminating the need for a zero mask layer.
• Layer 152 Figure 9) is removed or stripped from structure 112.
• structure 112 is oxidized to form structures 142, 146, and 148 in accordance with a LOCOS process. Structures 142, 146 and 148 are grown to a 1000 A to 3000 A thickness, preferably 2000 A to 2500 A or less.
• nitride layer 118 is removed or stripped. Layer 118 can be removed by a hot phosphoric acid wet strip process, other etching processes, or other removal processes.
• a hard mask or nitride layer 160 is deposited over structures 142, 146 and 148 and layer 116.
• Layer 160 is preferably similar to layer 118 (in FIGURE 10) and has a thickness of 1700 A.
• Etch resist layer 162 is provided over layer 160.
• Etch resist layer 162 is preferably a photoresist layer which is selectively provided to define structure 142 and structure 144 with spacings 166.
• Layer 162 preferably completely covers region 108.
• layer 160 is etched to define spacings 168.
• structure 1 12 undergoes a thermal process in accordance with a LOCOS technique to form structures 144 and 142 (FIGURE 7).
• structures 144 and 142 are grown to a thickness of 4000 A in peripheral region 109.
• Layer 160 in region 108 prevents further growth of structures 146 and 148 during this second LOCOS process.
• Structure 142 grows to an edge 168 (FIGURE 13) of layer 160.
• layer 160 is stripped by a hot phosphoric acid wet strip process. Alternatively, other etching or removal techniques can be utilized to remove layer 160.
• structures 144 and 142 have a relatively even thickness when compared to structure 24 (FIGURE 6).
• Structure 142 has a relatively even thickness throughout interface region 110.
• the use of two hard mask layers 118 and 160 advantageously eliminates or reduces residue or stringer problems associated with the conventional process discussed with reference to FIGURES 1-6. Accordingly, structure 112 can optimize isolation structure thicknesses associated with structures 142, 144, 146 and 148 because overetching problems are significantly reduced.
• source drain definitions in core region 108 can be used as a target for follow-up deep N-well, P-well and N-well implant masks, thereby eliminating the need for a zero layer mask.
• the process discussed with reference to FIGURES 7-13 reduces the "oxide" bump concern because each nitride layer 118 and 160 is only subjected to a single oxidation process. Therefore, the method advantageously eliminates material surface stress which can cause field edge defects in core region 8 due to oxidized nitride in core region 108. Further, the method reduces non-uniform "race track" problems due to topographic differences in field oxide thickness of structure 142 at interface region 110.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Element Separation (AREA)
• Local Oxidation Of Silicon (AREA)
• Metal-Oxide And Bipolar Metal-Oxide Semiconductor Integrated Circuits (AREA)

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• 1998
  • 1998-03-06 US US09/036,288 patent/US5966618A/en not_active Expired - Lifetime
• 1999
  • 1999-03-05 DE DE69939775T patent/DE69939775D1/de not_active Expired - Lifetime
  • 1999-03-05 JP JP2000535047A patent/JP2002506288A/ja active Pending
  • 1999-03-05 WO PCT/US1999/004905 patent/WO1999045589A1/en not_active Ceased
  • 1999-03-05 KR KR10-2000-7009845A patent/KR100537812B1/ko not_active Expired - Fee Related
  • 1999-03-05 EP EP99911155A patent/EP1060510B1/en not_active Expired - Lifetime

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