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
  • H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
• • 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
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02612—Formation types
  • H01L21/02617—Deposition types
  • H01L21/02636—Selective deposition, e.g. simultaneous growth of mono- and non-monocrystalline semiconductor materials
  • H01L21/02647—Lateral overgrowth
• • 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
• • 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
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02367—Substrates
  • H01L21/0237—Materials
  • H01L21/02373—Group 14 semiconducting materials
  • H01L21/02381—Silicon, silicon germanium, germanium
• • 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
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02436—Intermediate layers between substrates and deposited layers
  • H01L21/02439—Materials
  • H01L21/02441—Group 14 semiconducting materials
  • H01L21/0245—Silicon, silicon germanium, germanium
• • 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
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02518—Deposited layers
  • H01L21/02521—Materials
  • H01L21/02524—Group 14 semiconducting materials
  • H01L21/02532—Silicon, silicon germanium, germanium
• • 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
  • H01L21/02104—Forming layers
  • H01L21/02365—Forming inorganic semiconducting materials on a substrate
  • H01L21/02612—Formation types
  • H01L21/02617—Deposition types
  • H01L21/02636—Selective deposition, e.g. simultaneous growth of mono- and non-monocrystalline semiconductor materials
  • H01L21/02639—Preparation of substrate for selective deposition
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S438/00—Semiconductor device manufacturing: process
  • Y10S438/933—Germanium or silicon or Ge-Si on III-V

Definitions

• This invention relates to the production of lattice-tuning semiconductor substrates, and is more particularly, but not exclusively, concerned wifh the production of relaxed SiGe (silicon/germanium) "virtual substrates" suitable for the growth of strained silicon or SiGe active layers and unstrained III-V semiconductor active layers within which active semiconductor devices, such as MOSFETs, may be fabricated.
• relaxed SiGe silicon/germanium
• the buffer layer is provided in order to increase the lattice spacing relative to the lattice spacing of the underlying Si substrate, and is generally called a virtual substrate.
• the relaxation of the buffer layer inevitably involves the production of dislocations in the buffer layer to relieve the strain. These dislocations generally form a half loop from the underlying surface which expands to form a long dislocation at the strained interface.
• the production of threading dislocations which extend through the depth of the buffer layer is detrimental to the quality of the substrate, in that such dislocations can produce an uneven surface and can cause scattering of electrons within the active semiconductor devices.
• many dislocations are required to relieve the strain in a SiGe layer, such dislocations inevitably interact with one another causing pinning of threading dislocations. Additionally more dislocations are required for further relaxation, and this can result in a higher density of threading dislocations.
• US 2002/0017642 Al describes a technique in which the buffer layer is formed from a plurality of laminated layers comprising alternating layers of a graded SiGe layer having a Ge composition ratio which gradually increases from the Ge composition ratio of the material on which it is formed to an increased level, and a uniform SiGe layer on top of the graded SiGe layer having a Ge composition ratio at the increased level which is substantially constant across the layer.
• the provision of such alternating graded and uniform SiGe layers providing stepped variation in the Ge composition ratio across the buffer layer makes it easier for dislocations to propagate in lateral directions at the interfaces, and consequently makes it less likely that threading dislocations will occur, thus tending to provide less surface roughness.
• this technique requires the provision of relatively thick, carefully graded alternating layers in order to provide satisfactory performance, and even then can still suffer performance degradation due to the build-up of threading dislocations.
• a method of forming a lattice-tuning semiconductor substrate comprising: (a) defining parallel strips of a Si surface by spaced parallel isolating means;
• SiGe layer above the isolating means to relieve the strain in the second SiGe layer in directions transverse to the first dislocations.
• Figure 1 is an explanatory view showing the effect of the transverse dislocations in preventing relaxation of a strained Si substrate in the longitudinal direction;
• Figure 2 shows successive steps in a method of forming a lattice-tuning semiconductor substrate in accordance with the invention.
• Si substrate on an underlying Si substrate with the interposition of a SiGe buffer layer is also applicable to the production of other types of lattice-tuning semiconductor substrates, including substrates terminating at fully relaxed pure Ge allowing III-N incorporation with silicon. It is also possible in accordance with the invention to incorporate one or more surfactants, such as antimony for example, in the epitaxial growth process in order to produce even smoother virtual substrate surfaces and lower density threading dislocations by reducing surface energy.
• surfactants such as antimony for example
• Figure 1 shows a long thin stripe of SiGe material 1 which is grown within a confined area between Si oxide walls 2 which surround the SiGe material on four sides.
• dislocations 3 form preferentially along the shortest dimension of the area, that is from one long oxide wall towards the other opposite, long oxide wall.
• These dislocations 3 are generated at dislocation nucleation sites 4 along one or other of the long oxide walls, as illustrated in each case by a "X" in the figure. This is generally attributed to the ease of dislocation formation at the edge of the growth zone. Where dislocations are formed along the shortest dimension, these dislocations are able to extend to the opposite edge of the zone substantially unhindered.
• dislocations tending to form along the longest dimension of the zone are quickly blocked by the dislocations formed along the shortest dimension, and thus cannot traverse the entire length of the zone.
• Such dislocations 5 are shown in Figure 1 as being generated from one end of the zone but being quickly pinned at pinning locations 6 by the dislocations 3 extending along the shortest dimension.
• the SiGe material in this case can only be relaxed in one direction by the formation of the dislocations extending along the shortest dimension, whilst remaining unrelaxed in the orthogonal direction due to the failure of dislocations to form along the longest dimension (although there may be some elastic relaxation if the shortest dimension is small enough).
• the above described difficulties are discussed above in relation to growth of SiGe within a limited area confined by oxide walls 2, similar problems are found where SiGe is required to be grown within an area limited by the area of the substrate surface, for example on top of an etched mesa pillar.
• a layer of oxide is grown on a Si substrate 10 and is then selectively etched after the area to be etched has been defined, for example by the application of a photoresist layer to the oxide layer and the selective exposure and development of the photoresist layer to form a photoresist mask. After etching elongate walls 11 of oxide extend substantially parallel to one another along the length of the substrate 10 and are separated by long thin strips 12, as shown at a in Figure 2, within which a SiGe layer may subsequently be grown in the manner already described above.
• a SiGe layer 13 is selectively grown on each long thin strip 12 between the oxide walls 11, as shown at b in Figure 2, at a temperature in the range from room temperature to 1200°C, and preferably in the range from 350 to 900°C.
• Such SiGe growth is selective such that there is substantially no growth of SiGe along the top of the oxide walls 11.
• Such selective growth may be effected by chemical vapour deposition (CND).
• CND chemical vapour deposition
• dislocations 14 are caused to be generated at each oxide wall 11 and to extend along the shortest dimension towards the opposite oxide wall 11. In this manner the SiGe material is caused to relax in the direction of the dislocations 14 which extend over the entire width of the area between the walls 11.
• SiGe material is continued at a temperature in the range from room temperature to 1200°C, and preferably in the range from 350 to 900°C, to form a further SiGe layer 13a continuous with the first SiGe layer 13 until lateral overgrowth of the SiGe material onto the top of the oxide walls 11 occurs, as shown at d in Figure 2.
• the grown areas of SiGe seeded in the areas between the oxide walls 11 will coalesce with each other and cover the entire surface of the Si substrate.
• the SiGe material grown in this manner may form a single crystalline layer, or alternatively there may be stacking faults where the different growth zones coalesce. It is in any case likely that the surface will be uneven where the different growth zones meet.
• the strain in the unrelieved longitudinal direction is eventually relaxed by the formation of dislocations extending in the longitudinal direction which are able to be nucleated from anywhere on the wafer. Since such nucleation has a much higher activation energy than nucleation from the oxide walls on the sides of the growth zone, the formation of such longitudinal dislocations 15 occurs at a much later stage than the formation of the dislocations 14 within the windows defined by the oxide walls 11.
• the two sets of dislocations 13, 15 do not interact with one another and the dislocations may extend over the whole surface of the wafer. Furthermore, because there is no strain in the SiGe material in a direction orthogonal to the outside walls 11, there will be no driving force tending to produce dislocations in this direction. Furthermore, since any dislocation interactions are kept to a minimum, there are substantially no threading dislocations produced which would otherwise terminate at the upper surface of the SiGe material resulting in roughness of the surface.
• the height of the oxide walls 11 may vary from 10 nm to 1,000 nm depending on the Ge composition of the SiGe material, although it would normally be expected to be in the range of 400 nm to 700 nm.
• the oxide windows may range in width from 100 nm to 100 ⁇ m in width, and most likely are from 5 ⁇ m to 20 ⁇ m in width.
• the width of the oxide walls 11 is preferably as small as possible to ensure full lateral overgrowth, and currently the width is likely to be in the range from 100 nm to 10 ⁇ m, and preferably about 1 ⁇ m.
• the Ge composition within the SiGe material may be substantially constant through the thickness of the layer, although it would also be possible for the Ge composition to be graded so that it increases from a first composition at a lower level in the layer to a second, higher composition at a higher level in the layer.
• an uneven surface 16 may be obtained, as shown at d in Figure 2, and the effect of this may be overcome by a chemo-mechanical polishing (CMP) step to planarise the surface before a final capping layer is grown to obtain the final arrangement shown at e in Figure 2.
• CMP chemo-mechanical polishing
• an annealing step is applied to ensure full relaxation. Such an annealing step may be effected at any stage in the SiGe growth process, although it is preferably effected after the selective SiGe growth between the oxide walls 11 and before the further growth leading to overgrowth of the oxide walls 11.
• the SiGe growth occurs on top of closely spaced mesa pillars defining the growth zones.
• the isolation between the strips is provided by the trenches between the pillars, rather than by isolating oxide walls, and the epitaxial growth process may be molecular beam epitaxy (MBE) or CVD.
• the SiGe material may be grown between spaced parallel walls of Si nitride or some other isolating material.
• the virtual substrate may be epitaxially grown on a patterned silicon wafer or a wafer having a patterned oxide layer such that growth only occurs in selected areas.
• the fabrication technique may be used to produce a virtual substrate in only one or more selected areas of the chip (as may be required for system-on-a-chip integration) in which enhanced circuit functionality is required, for example.
• the method of the invention is capable of a wide range of applications, including the provision of a virtual substrate for the growth of strained or relaxed Si, Ge or SiGe layers for fabrication of devices such as bipolar junction transistors (B JT), field effect transistors (FET) and resonance tunnelling diodes (RTD), as well as III-V semiconductor layers for high speed digital interface to CMOS technologies and optoelectronic applications including light emitting diodes (LEDs) and semiconductor lasers.
• B JT bipolar junction transistors
• FET field effect transistors
• RTD resonance tunnelling diodes
• III-V semiconductor layers for high speed digital interface to CMOS technologies and optoelectronic applications including light emitting diodes (LEDs) and semiconductor lasers.

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• 2002
  • 2002-09-03 GB GBGB0220438.6A patent/GB0220438D0/en not_active Ceased
• 2003
  • 2003-08-12 AU AU2003251376A patent/AU2003251376A1/en not_active Abandoned
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  • 2003-08-12 JP JP2004533596A patent/JP2005537672A/ja active Pending
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