Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D10/00—Bipolar junction transistors [BJT]
  • H10D10/01—Manufacture or treatment
  • H10D10/051—Manufacture or treatment of vertical BJTs
  • H10D10/054—Forming extrinsic base regions on silicon substrate after insulating device isolation in vertical BJTs having single crystalline emitter, collector or base regions
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
  • H10D10/00—Bipolar junction transistors [BJT]
  • H10D10/01—Manufacture or treatment
  • H10D10/021—Manufacture or treatment of heterojunction BJTs [HBT]

Definitions

• the invention relates to a method of manufacturing a semiconductor device comprising a semiconductor body with a bipolar transistor including a base, an emitter and a collector, said base being formed by providing the semiconductor body with a doped semiconducting layer which locally borders on a monocrystalline part of the semiconductor body where it forms a first semiconductor region which is monocrystalline and constitutes the base of the transistor, and which semiconductive layer borders, outside said base, on a non- monocrystalline part of the semiconductor body where it forms a second semiconductor region which is not monocrystalline and which constitutes a connection region of the base, the non- monocrystalline part of the semiconductor body being obtained by covering the semiconductor body with a mask and replacing, on either side thereof, a part of the semiconductor body by an electrically insulating region, and by providing the electrically insulating region with a polycrystalline semiconducting layer before the provision of the semiconducting layer.
• Such a method is known from European patent application, filed by the current applicant (PHN 17.066) under application no. 98202894.6 on 31-08-1998.
• a description is given of a method for the manufacture of a so-called differential bipolar transistor.
• Such a transistor is obtained by providing a semiconducting layer on a crystalline and a non-crystalline part of the semiconductor body, which forms at said locations, respectively, a crystalline semiconductor region, the base of the transistor, and a non- crystalline semiconductor region, a connecting region of the base.
• the crystalline part of the semiconductor body forms the collector, and in the semiconducting layer the emitter is formed at the location of the base.
• the non-monocrystalline part of the semiconductor body is formed by an electrically insulating region which surrounds the collector and on which a polycrystalline semiconducting layer is situated which serves as the host layer during the provision of the semiconducting layer.
• LOCOS Local Oxidation Of Silicon
• a method in accordance with the invention is characte ⁇ zedin that the polycrystalline layer is selectively provided on the elect ⁇ cally insulating region, use being made of the mask to form the elect ⁇ cally insulating region
• the method in accordance with the invention is much simpler than the known method. Additional photolithographic and etch steps are not necessary to (re-)expose the collector.
• the use of the mask employed for forming the elect ⁇ cally insulating region has an important additional advantage which is connected with the following surp ⁇ sing realization: by applying chemico-mechanical polishing du ⁇ ng the selective application of the polycrystalline layer, said polycrystalline layer can be provided in the same manner as the elect ⁇ cally insulating region, thereby making its manufacture easy.
• a method in accordance with the invention has the important advantage that the aperture which the polycrystalline semiconducting layer should have above the collector is formed in a self- recording manner relative to said collector. As a result, the dimensions of the transistor to be formed can be much better controlled, thus enabling, in particular, said dimensions to be very small and hence the transistor very fast.
• the polycrystalline semiconducting layer is provided onto the mask and the elect ⁇ cally insulating region, and the resulting structure is leveled off by means of chemico-mechanical polishing, the mask remaining bu ⁇ ed in the polycrystalline semiconducting layer, and subsequently the polycrystalline semiconducting layer is removed to such an extent that the mask is re-exposed.
• a method in accordance with the invention is made simple by applying this technique.
• the mask is, for example, a nit ⁇ de mask which, as m the known method, can be used to form so-called LOCOS oxide which forms the elect ⁇ cally insulating region on either side of the collector. Re-exposing the mask can take place simultaneously with leveling off the structure by means of CMP.
• the electrically insulating region is formed by making grooves in the semiconductor body on either side of the mask, providing an electrically insulating layer in the grooves and on the mask, whereafter an electrically insulating layer is provided in the grooves and on the mask, and the resultant structure is leveled off by means of chemico-mechanical polishing, the mask remaining buried in the electrically insulating layer, whereafter the electrically insulating layer is removed to such an extent that the mask is re-exposed, whereafter a part of the resultant electrically insulating region is removed, the mask remaining intact.
• an amsotropic etching technique such as plasma etching
• Such a method, in which chemico-mechanical polishing can also be used to form the electrically insulating region, keeps the method simple because both the electrically insulating region and the polycrystalline layer are formed in the same manner.
• the formation of the electrically insulating region in this manner results in a very flat structure, thereby substantially simplifying the subsequent selective provision in a similar manner of the polycrystalline semiconducting layer, since an electrically insulating region formed by so-called LOCOS oxide, results in a structure which is not very flat, thereby hampering the chemico-mechanical process to be carried out after the provision of the polycrystalline layer.
• This profile can be obtained by forming a recess in the structure using a wet-chemical etchant which is selective with respect to electrically insulating material.
• the mask can be exposed by means of the CMP step, but also by a separate (anisotropic) etch step after the structure has been leveled off by means of CMP, the mask still being buried in the insulating layer. If the anisotropic etch step is carried out using an etchant which etches the electrically insulating material in a selective manner with respect to the mask, then the additional advantage is obtained that no separate etch step is necessary to provide the structure, after exposure of the mask, with the profile necessary to apply the polycrystalline layer.
• the method of this variant can very suitably be used to manufacture transistors having very small dimensions.
• the mask used in this operation is preferably removed. This can be achieved in a simple manner by immersing the mask in an etchant which is selective with respect to the mask. As a result, the collector is re-exposed, and the semiconducting layer can be provided. Subsequently, the emitter can be formed so as to border on the base.
• silicon dioxide is used as the material for the electrically insulating region
• silicon nitride is used as the material for the mask.
• These materials can be readily selectively removed relative to each other and relative to silicon. These materials can also very suitably be used in combination with the chemico-mechanical polishing technique.
• Figs. 1 through 10 are diagrammatic, cross-sectional views, at right angles to the thickness direction, of a semiconductor device with a bipolar transistor, at successive stages in the manufacture using a method in accordance with the invention.
• the Figures are diagrammatic and not drawn to scale, in particular the dimensions in the thickness direction being exaggerated for clarity. Semiconductor regions of the same conductivity type are generally hatched in the same direction. Like reference numerals refer to like regions whenever possible.
• Figs. 1 through 10 are diagrammatic, cross-sectional views, at right angles to the thickness direction, of a semiconductor device with a bipolar transistor, at successive stages in the manufacture using a method in accordance with the invention. Fig.
• the semiconductor body 10 is a diagrammatic, cross-sectional view, at right angles to the thickness direction, of the finished device comprising a bipolar transistor.
• the semiconductor body 10 comprises (not shown in the drawing) a monocrystalline substrate of p + -type silicon covered with a 1 ⁇ m thick monocrystalline epitaxial layer 3 of n-type silicon with a doping concentration of 1 x 10 16 at/cm 3 which forms a collector 3 of the transistor.
• the epitaxial layer 3 accommodates a 0.3 ⁇ m recessed insulation region 8 which, in this case, includes silicon dioxide and surrounds the collector 3.
• a polycrystalline, p-type silicon layer 4 having a thickness of 50 nm and a doping concentration of, in this example, 1 x 10 20 at/cm 3 .
• an, in this case 150 nm thick, p- type semiconducting layer 1 which, in this case contains SiGe with 20 at.% germanium.
• the part 1A of the semiconducting layer 1 bordering on the collector 3 is monocrystalline and forms a base 1A of the transistor.
• the remaining part IB of the semiconducting layer 1 is polycrystalline, borders on the polycrystalline layer 4 and forms a connecting region IB of the base 1A of the transistor At the location of the base 1A, the doping concentration is 1 x 10 19 at/cm , at the location of the connecting region IB, the doping concentration is higher and amounts to 1 x 10 20 at/cm 3 .
• the semiconducting layer 1 there is a 0.3 ⁇ m thick insulating layer of silicon dioxide having a recessed portion above the base 1A, which is filled with an emitter connection 7 of n-type polycrystalline silicon whose doping concentration is approximately 10 21 at/cm 3
• an emitter 2 of the transistor which is recessed m the base 1 A which is of the n-conductivity type, has a thickness of 40 nm and a doping concentration of approximately 10 20 at/cm 3
• the device further includes (not shown in the Figure) elect ⁇ cal connections of the connecting region 11 of the emitter 2, of the connecting region IB of the base 1 A and of a connecting region (not shown either in the drawing) of the collector 3.
• the width of the part of the semiconductor body shown in the drawing is several micrometers, the collector 3 and the base 1A have a width of approximately 1 ⁇ m, and the width of the emitter 2 and the emitter connection 7 is approximately 0 5 ⁇ m.
• a p-type silicon substrate (not shown m the drawing) is first provided with an epitaxial n-type silicon layer 3 (see Fig. 1).
• This n-type silicon layer is provided with a mask 20, which in this case is formed from a 200 nm thick silicon nit ⁇ de layer 20 by means of photolithography and etching.
• plasma etching see Fig. 2
• 0.3 ⁇ m deep grooves 21 are formed in the semiconductor body 10 on either side of the mask 20.
• LPCVD Low Pressure Chemical Vapor Deposition
• the oxide layer 8 is subjected to a chemico-mechanical polishing so as to ensure that the resultant structure is flat and the surface of the (remaining part) of the mask 20 is re-exposed.
• a slurry of silicon dioxide particles and potassium hydroxide.
• a suitable slurry is, for example, ssl2 by Cabbot.
• the elect ⁇ cally insulating region 8 is subsequently selectively provided with a polycrystalline semiconducting layer 4, in which process use is made of the mask 20 which was used to form the elect ⁇ cally insulating region 8.
• the method in accordance with the invention is much simpler than the known method. First of all, additional photolithography and etching, as m the known method, are not necessary to remove (again) the polycrystalline layer 1 above the collector 3.
• a chemico-mechanical polishing technique becomes very suitable to obtain the desired result.
• Another important advantage of a method in accordance with the invention is that the aperture in the polycrystalline semiconducting layer 4 above the collector 3 is formed in a self- recording manner relative to said collector 3. As a result, the dimensions of the transistor to be formed can be controlled much better, thus enabling very small and very fast transistors to be achieved.
• the surface of the semiconductor body 10 is first provided with a several tens of micrometers thick polycrystalline semiconducting layer 4, in this case by means of LPCVD from a gas mixture containing silane and hydrogen.
• the polycrystalline layer 4 is removed by means of chemico- mechanical polishing to such an extent the resultant structure is flat.
• the mask 20 is still buried in the polycrystalline layer 4.
• use is made of the same slurry as in the above-described chemico-mechanical polishing step. It is alternatively possible, however, to use a different slurry which is more specially developed for etching polycrystalline silicon.
• an anisotropic etch technique such as plasma etching, is used to etch back the polycrystalline layer 4 until the mask 20 is exposed.
• the insulating region 8 is provided, in a selective and self-recording manner, with the polycrystalline semiconducting layer 4.
• the mask 20 is removed by means of etching, in this case by means of warm phosphoric acid, without the polycrystalline layer 4 and the collector 5 being attacked.
• the resultant structure is used to continue the manufacture of the transistor.
• the geometry and dimensions of the various regions of the transistor may be chosen so as to be different.
• a device in accordance with the invention can also be a more complex device than a single bipolar transistor.
• the device may comprise a number of different active or passive components.

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• Bipolar Transistors (AREA)

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• 1999
  • 1999-08-31 DE DE69935967T patent/DE69935967T2/de not_active Expired - Lifetime
  • 1999-08-31 WO PCT/EP1999/006416 patent/WO2000016392A1/en not_active Ceased
  • 1999-08-31 JP JP2000570829A patent/JP2002525851A/ja active Pending
  • 1999-08-31 EP EP99969180A patent/EP1048066B1/en not_active Expired - Lifetime
  • 1999-09-10 US US09/393,944 patent/US6150224A/en not_active Expired - Lifetime

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