Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
  • H01L27/04—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body
  • H01L27/08—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including only semiconductor components of a single kind
  • H01L27/085—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including only semiconductor components of a single kind including field-effect components only
  • H01L27/088—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including only semiconductor components of a single kind including field-effect components only the components being field-effect transistors with insulated gate
  • H01L27/092—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including only semiconductor components of a single kind including field-effect components only the components being field-effect transistors with insulated gate complementary MIS field-effect transistors
  • H01L27/0921—Means for preventing a bipolar, e.g. thyristor, action between the different transistor regions, e.g. Latchup prevention
• • 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
  • H01L21/763—Polycrystalline semiconductor regions

Definitions

• the invention pertains generally to semiconductor devices and, particularly, to integrated circuits containing complementary metal oxide semiconductor devices.
• CMOS 10 integrated circuit devices include both n- and p-channel field effect transistors (FETs) on the same substrate. While, as known, it is generally desirable to space the different transistors as closely together as possible on the substrate, a limitation in the past is that if adjacent
• FIG. 1 is a cross-sectional view of a first embodiment of the inventive CMOS device.
• FIGS. 2-3 are cross-sectional views of second and third embodiments of the inventive CMOS device.
• the invention is described in connection with an integrated circuit comprising a plurality of field-effect transistors disposed within a substrate of silicon.
• the trench filler material perferably comprises polycrystalline or amorphous silicon ("polysilicon” hereinafter) because such material can be readily deposited to completely fill a trench of proper design and because its coefficient of thermal expansion is the same as that of the silicon substrate. Both these conditions—complete, void-free filling and matching coefficient of expansion—are essential to avoid the prior art problem of excessive cracking of the trench-containing substrates.
• silicon dioxide While it is known in the past to fill trenches with polysilicon, silicon dioxide is also used, and no distinction has been made, as far as we know, between the two materials with respect to the cracking problem. Silicon dioxide, we have discovered, however, is not a suitable filler material with silicon substrates owing to the great disparity in the coefficients of thermal expansion of these materials.
• substrate-filler material combinations can be used. For example, it is possible to fill trenches in
• MPI substrates of gallium arsenide with poly/crystalline gallium arsenide deposited in known manner MPI substrates of gallium arsenide with poly/crystalline gallium arsenide deposited in known manner.
• filler materials can be used with non-identical substrate materials provided the coefficients of thermal expansion of the materials match within a factor of about 3.
• polysilicon is a good candidate for use as a filler material in substrates of gallium arsenide and similar III-IV compounds.
• a first embodiment of the inventive device depicted in FIG. 1, includes a substrate 20, of silicon, having a bulk region 30 of, for example, p-type conductivity (n-type conductivity is also useful) provided by a doping level ranging from about 10 15cm-3 to about 10 17cm-3. Doping levels less than about 10 15cm-3 are undesirable because they require undesirably deep trenches to significantly reduce the possibility of latchup.
• the substrate 20 also includes a tub 40 of / conductivity type opposite to that of the bulk region 30, e.g., n-type conductivity, extending from the surface 50.
• the depth of the tub 40 is preferably greater than about 1/2 m, while the vertical integrated doping level of the tub 40, i.e., the integral of the doping level of the tub 40 over the depth of the tub 40, ranges from about
• the device includes a trench 140 which prevents, or substantially reduces the possibility of, latchup.
• the trench is formed in the silicon substrate 20, and separates
• the one or more p-channel FETs formed in the tub 40 from the one or more n-channel FETs fabricated in the bulk region 30, i.e., the trench encircles the FETs in the tub 40.
• the trench 140 is formed after the fabrication of the tub 40 but before the fabrication of the FETs, and is preferably positioned at the juncture of the tub 40 and bulk region 30.
• a preferred filler material 160 is polysilicon which is readily deposited into the trench 140 using, for example, known conventional chemical vapor deposition (CVD) techniques.
• CVD chemical vapor deposition
• two conditions are preferably met. The first is that the angle (denoted ⁇ in FIG. 1) between the trench sidewall 150 and a perpendicular to the substrate surface 50 is between about 5 to 10 degrees. It is found that trenches having steeper (e.g., vertical) walls or, worse, negative angle walls (e.g., trenches which widen towards the bottom) are quite difficult to completely fill.
• the diverging trench walls avoid any masking effects, by the walls, of the filler material during the deposition process. Conversely, trenches having wall angles in excess of 10 degrees become too wide, thus defeating the object of small transitor spacings.
• the second condition is that the thickness of the polysilicon deposited in the trench filling process is adequate to at least completely fill the trench. To ensure this result, a thickness which is slightly excessive is used, and the excessive material overlying the trench is slightly etched back using known processes. To prevent conduction of leakage currents, and diffusion of dopant, from the substrate 20 into the polysilicon 160, the trench 140 preferably includes a
• OMPI relatively thin layer of a dielectric material (material whose bandgap is greater than about 2 eV) 170 covering the interior surfaces of the trench.
• dielectric materials include Si ⁇ 2 and Si 3 N4 deposited in known fashion.
• the thickness of the dielectric layer 170 ranges from about 200 Angstroms (A) to about 5000 A. A thickness less than about 200 A is undesirable as being ineffective to prevent short circuits through the polysilicon. A thickness greater than about 5000 A is undesirable as resulting in the formation of cracks and dislocations at the coating 170-trench wall 150 interface during high temperature processing.
• a second embodiment of the inventive device differs from the first embodiment in that the substrate 20 includes a relatively heavily doped bulk region 32 of, for example, p-type conductivity, supporting a moderately doped, relatively thin (compared to the bulk region 32) layer 34 whose conductivity type is the same as that of the region 32.
• the layer 34 is preferably epitaxially grown on the bulk region 32 using, for example, conventional vapor phase epitaxy.
• a tub 40 of, for example, n-type conductivity, is formed in the moderately doped layer 34 and a trench 140 extends through the thickness of the layer 34 at least to the heavily doped bulk region 32.
• the advantage of this arrangement is that the depth of the trench 140 is reduced (as compared to the trench employed in the first embodiment) because the heavy doping within the bulk region 32 reduces the lifetime of minority charge carriers therethrough which would otherwise cause latchup between the two MOS devices shown.
• the doping level within the bulk region 32 ranges from about 10 17 to about 1021cm-3, and is preferably about 10 20cm-3.
• a doping level less than about 10 17cm—3 is undesirable because so low a doping level does not significantly reduce the possibility of latchup.
• a doping level greater than about 10 21cm—3 is undesirable because so high a doping level results in an undesirably large out-diffusion of dopant from the bulk region 32 into the layer 34.
• the layer 34 has a thickness ranging from about
• the tub 40 has a thickness greater than about
• a third embodiment of the inventive device is generally similar to the second embodiment except that the depth of the trench 140 is reduced by the depth of a relatively heavily doped region 190 within the layer 34, extending from the bottom of " the trench into the bulk region 32.
• the conductivity type and the doping level range for the region 190 is the same as that for the bulk region 32, and thus the region 190 is essentially an extension of the bulk ⁇ region 32 into the layer 34.
• the region 190 serves the same purpose as the bulk region 32, i.e., it reduces the lifetime of minority carriers therethrough (while decreasing trench depth) .
• the region 190 is formed by implanting donor or acceptor ions (depending on whether the region 190 is to be of ni or p + -type conductivity) into the semiconductor material adjacent the bottom of the trench, and then diffusing these ions toward the bulk region 32 with a heat treatment. Because ions diffuse both vertically and laterally, vertical diffusion, and thus the depth of region 190, is preferably less than about 4 ⁇ m to avoid
• Ion implantation preferably occurs after the formation of the dielectric layer 170 on the walls of the trench 140 (and before the deposition of the polysilicon). Because the trench sidewall 150 is inclined to the vertical (as viewed in FIG. 4), and because the ions travel an essentially vertical path, the ions impinging the sidewall of the trench must penetrate a greater thickness of dielectric material than the ions impinging the bottom of the trench to reach the underlying semiconductor material. Thus, relatively few, if any, ions penetrate the sidewall 150 into the tub 40.
• acceptor ions such as boron ions
• useful dopant implantation levels range from

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Metal-Oxide And Bipolar Metal-Oxide Semiconductor Integrated Circuits (AREA)
• Element Separation (AREA)

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• 1984
  • 1984-10-04 DE DE8484306756T patent/DE3472604D1/de not_active Expired
  • 1984-10-04 EP EP84306756A patent/EP0138517B1/de not_active Expired
  • 1984-10-04 WO PCT/US1984/001583 patent/WO1985001836A1/en not_active Application Discontinuation
  • 1984-10-04 KR KR1019850700081A patent/KR850700087A/ko not_active Application Discontinuation
  • 1984-10-04 EP EP84903741A patent/EP0158670A1/de active Pending

Non-Patent Citations (1)

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