WO2019101577A1 - Near-infrared photodetector semiconductor device - Google Patents

Near-infrared photodetector semiconductor device Download PDF

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Publication number
WO2019101577A1
WO2019101577A1 PCT/EP2018/081086 EP2018081086W WO2019101577A1 WO 2019101577 A1 WO2019101577 A1 WO 2019101577A1 EP 2018081086 W EP2018081086 W EP 2018081086W WO 2019101577 A1 WO2019101577 A1 WO 2019101577A1
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WIPO (PCT)
Prior art keywords
trenches
conductivity
semiconductor device
type
sige alloy
Prior art date
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Ceased
Application number
PCT/EP2018/081086
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French (fr)
Inventor
Ingrid Jonak-Auer
Gerald Meinhardt
Bernhard LÖFFLER
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Ams Osram AG
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Ams AG
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Publication date
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Priority to US16/763,894 priority Critical patent/US11335824B2/en
Priority to CN201880072965.8A priority patent/CN111684597B/en
Publication of WO2019101577A1 publication Critical patent/WO2019101577A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/14—Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies
    • H10F77/147—Shapes of bodies
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/21—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation
    • H10F30/22—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes
    • H10F30/223—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes the potential barrier being a PIN barrier
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F39/00—Integrated devices, or assemblies of multiple devices, comprising at least one element covered by group H10F30/00, e.g. radiation detectors comprising photodiode arrays
    • H10F39/10—Integrated devices
    • H10F39/12—Image sensors
    • H10F39/18—Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
    • H10F39/184—Infrared image sensors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F39/00—Integrated devices, or assemblies of multiple devices, comprising at least one element covered by group H10F30/00, e.g. radiation detectors comprising photodiode arrays
    • H10F39/80—Constructional details of image sensors
    • H10F39/806—Optical elements or arrangements associated with the image sensors
    • H10F39/8067—Reflectors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/12—Active materials
    • H10F77/122—Active materials comprising only Group IV materials

Definitions

  • the present disclosure applies to the field of integrated near-infrared photodetector semiconductor devices.
  • Semiconductor photodetector devices for wavelengths in the near infrared (NIR) are applied in optical communication, metrology, imaging and spectroscopy, for instance, and may comprise silicon (Si), germanium (Ge) and SiGe alloys.
  • Si silicon
  • Ge germanium
  • SiGe alloys silicon
  • a monolithic integration of optics and electronics parts is desired in view of system performance and small size.
  • trench will be used to denote any suitable opening or recess of arbitrary shape, which can be etched into a semiconductor layer.
  • the near-infrared photodetector semiconductor device The near-infrared photodetector semiconductor device
  • conductivity may be n-type conductivity and the second type of conductivity p-type conductivity, for instance, or vice versa .
  • the SiGe alloy layer is doped for the second type of conductivity, and the filling material comprises a portion of the SiGe alloy layer.
  • the SiGe alloy layer may fill the trench or the plurality of trenches.
  • a further embodiment comprises a silicon layer in the trench or the plurality of trenches.
  • the silicon layer may
  • the SiGe alloy layer and the silicon layer may fill the trench or the plurality of trenches .
  • the silicon layer is doped for the second type of conductivity, and the filling material comprises a portion of the silicon layer.
  • the SiGe alloy layer may be undoped or intrinsically doped.
  • the SiGe alloy layer is doped for the second type of conductivity, the silicon layer is undoped or intrinsically doped, and the filling material comprises a portion of the SiGe alloy layer.
  • a further embodiment comprises a contact region of the first type of conductivity in the semiconductor layer at the main surface, the contact region being at a distance from the trench or the plurality of trenches.
  • conductive contact connection is electrically conductively connected with the filling material, and a further
  • electrically conductive contact connection is electrically conductively connected with the contact region.
  • the trench or at least one of the trenches of the plurality of trenches has a smooth or a grooved sidewall.
  • the semiconductor layer of the first type of conductivity is silicon, and the SiGe alloy layer is epitaxially grown on the silicon.
  • a differential or selective epitaxy of the SiGe alloy layer enables to vary and adapt the germanium content during the deposition of the SiGe alloy layer .
  • the arrangement of the SiGe alloy layer in the trench or the plurality of trenches increases the absorption length and thus improves the light sensitivity of the photodetector semiconductor device in the spectral range of red and near- infrared light.
  • Figure 1 is a cross section of a photodetector semiconductor device comprising trenches with smooth sidewalls.
  • Figure 2 is a cross section of a further photodetector
  • Figure 3 is a top view of an arrangement of the trenches.
  • Figure 4 is a top view of a further arrangement of the
  • Figure 5 is a cross section of a photodetector semiconductor device comprising trenches with grooved sidewalls.
  • Figure 6 is a cross section of a further photodetector
  • semiconductor device comprising trenches with grooved sidewalls.
  • Figure 7 is a diagram showing examples of the relative
  • germanium content x as a function of the level h above a silicon surface.
  • Figure 1 is a cross section of a photodetector semiconductor device. At least one trench 2 is formed at a main surface 10 of a semiconductor layer 1, which may especially be silicon.
  • the semiconductor layer 1 has a first type of conductivity. The number of trenches is arbitrary; Figure 1 shows a plurality of three trenches 2, by way of example.
  • a SiGe alloy layer 3 is arranged in each trench 2 and on the main surface 10. If the semiconductor layer 1 is silicon, the SiGe alloy layer 3 can be epitaxially grown on the silicon.
  • the SiGe alloy layer 3 comprises silicon and germanium, and it may also comprise an optional additive like carbon, for instance.
  • the shape of the trenches 2 can be adapted to the epitaxial growth.
  • the sidewalls of the trenches 2 can be perpendicular or inclined with respect to the main surface 10.
  • the sidewalls can be smooth, as shown in Figure 1, or rough.
  • Bottom areas of the trenches 2 can be flat or curved.
  • the SiGe alloy layer 3 has a second type of conductivity opposite to the first type of conductivity.
  • the first type of conductivity may be n-type conductivity and the second type of conductivity p-type conductivity, or vice versa.
  • the SiGe alloy layer 3 may completely fill the trenches 2, as shown in Figure 1. In this case the large volume of the SiGe alloy layer 3 enhances the absorption of near-infrared light.
  • a contact region 4 of the first type of conductivity may be arranged in the semiconductor layer 1 at the main surface 10 and at a distance from the trenches 2.
  • the contact region 4 comprises a doping concentration that is higher than the doping concentration of the semiconductor layer 1 in order to allow the formation of an ohmic contact.
  • a contact connection 6 comprising an electrically conductive material is arranged contacting the SiGe alloy layer 3, and a further contact connection 8 comprising an electrically conductive material is arranged contacting the contact region 4.
  • the contact connections 6, 8 may be formed by plugs in an intermetal dielectric and may connect the SiGe alloy layer 3 and the contact region 4 with conductor tracks 7, 9 in a metal layer of a wiring, for example. Details of the wiring, which are arbitrary, are not shown in Figure 1.
  • Figure 2 is a cross section of a further photodetector semiconductor device. Elements of the photodetector
  • the photodetector semiconductor device according to Figure 2 that correspond to elements of the photodetector semiconductor device according to Figure 1 are designated with the same reference numerals.
  • the photodetector semiconductor device according to Figure 2 comprises a silicon layer 5 in the trenches 2.
  • the silicon layer 5 may especially comprise polysilicon.
  • the SiGe alloy layer 3 and the silicon layer 5 may completely fill the trenches 2.
  • the silicon layer 5 may also be applied on the SiGe alloy layer 3 above the main surface 10, as shown in Figure 2.
  • the silicon layer 5 may be undoped or
  • the contact connection 6 is arranged in such a manner that it contacts the SiGe alloy layer 3.
  • the refractive index of silicon is lower than the refractive index of SiGe, total reflection of light at the boundary between the silicon layer 5 and the SiGe alloy layer 3 yields a longer optical path and enhanced light absorption.
  • the silicon layer 5 may be doped for the second type of conductivity, especially in situ during its deposition. If the silicon layer 5 is doped for the second type of
  • the SiGe alloy layer 3 may be undoped or intrinsically doped.
  • the contact connection 6 is arranged in such a manner that it contacts the silicon layer 5. If the SiGe alloy layer 3 is undoped, the space charge region extends over the entire portion of the SiGe alloy layer 3 that is arranged within the trenches 2, and this results in a better carrier collection efficiency.
  • Figure 3 is a top view of an arrangement of the trenches 2 for an example in which the trenches 2 are cylindrical.
  • the SiGe alloy layer 3 and the conductor track 7 are indicated in Figure 3 in order to facilitate the comparison with the cross section shown in Figure 1.
  • Figure 4 is a top view of a further arrangement of the trenches 2 for an example in which the trenches 2 have longitudinal extensions and are parallel to each other.
  • the shapes and arrangements of the trenches 2 are not restricted to these examples, but may vary according to individual requirements .
  • the trenches 2 can be etched into the semiconductor layer 1, and the etching process can be performed in such a way that it yields grooved or corrugated surfaces of the sidewalls. Such etching
  • Figure 5 is a cross section of a photodetector semiconductor device comprising trenches 2 with grooved sidewalls. Elements of the photodetector semiconductor device according to Figure 5 that correspond to elements of the photodetector
  • semiconductor device according to Figure 1 are designated with the same reference numerals.
  • the shape of the sidewalls makes the difference between the devices according to Figures 1 and 5.
  • Figure 6 is a cross section of a further photodetector semiconductor device comprising trenches 2 with grooved sidewalls. Elements of the photodetector semiconductor device according to Figure 6 that correspond to elements of the photodetector semiconductor device according to Figure 2 are designated with the same reference numerals. The shape of the sidewalls makes the difference between the devices according to Figures 2 and 6.
  • Figure 7 is a diagram showing some examples of the relative germanium content x of the Sii- x Ge x alloy in the SiGe alloy layer 3 as a function of the level h above the surface on which the SiGe alloy layer 3 is grown.
  • the Sii- x Ge x alloy may especially be epitaxially grown on a silicon surface, as indicated on the right side of the diagram.
  • the relative germanium content x of the alloy Sii_ x Ge x can be varied during the deposition of the SiGe alloy layer 3, so that the
  • SiGe alloy layer 3 properties of the SiGe alloy layer 3 can be adapted to the requirements of individual embodiments.
  • the relative germanium content x may instead be essentially constant, so that the SiGe alloy layer 3 is homogeneous.
  • Such a SiGe alloy layer 3 is represented in Figure 1 by the horizontal line x' ' ' .
  • An integrated circuit of the photodetector semiconductor device can be formed by a conventional CMOS process, for instance, which is known per se and need not be described here.
  • the formation of the trenches 2 and the SiGe alloy layer 3 may take place after the CMOS process. Instead, the trenches 2 can be etched at an earlier stage of the CMOS process. In this case the trenches 2 are subsequently filled with a sacrificial filling, which may be an oxide of the semiconductor material, for instance. After the CMOS process, the sacrificial filling is removed, which may be effected by wet etching, for instance, to open the trenches 2, and the SiGe alloy layer 3 is subsequently deposited.
  • Deep trenches provide long optical paths within the SiGe alloy layer in the vertical direction.
  • a differential or selective epitaxial growth of the SiGe alloy layer guarantees monocrystalline growth with low defect density at the Si/SiGe interface, thus enabling the formation of photodetectors with low dark current.
  • the efficiency in photocarrier collection is enhanced by an increase of the width of the space charge region within the SiGe alloy.
  • the efficiency in photocarrier collection is also enhanced when the relative germanium content of the SiGe alloy layer continuously increases or decreases with increasing distance from the silicon surface on which the SiGe alloy layer is epitaxially grown.
  • an integrated near-infrared photodetector semiconductor device comprising the described features has many advantages and is favourable for a wide variety of applications.

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Abstract

The near-infrared photodetector semiconductor device comprises a semiconductor layer (1) of a first type of conductivity with a main surface (10), a trench or a plurality of trenches (2) in the semiconductor layer at the main surface, a SiGe alloy layer (3) in the trench or the plurality of trenches, and an electrically conductive filling material of a second type of conductivity in the trench or the plurality of trenches, the second type of conductivity being opposite to the first type of conductivity.

Description

Description
NEAR-INFRARED PHOTODETECTOR SEMICONDUCTOR DEVICE
The present disclosure applies to the field of integrated near-infrared photodetector semiconductor devices.
Semiconductor photodetector devices for wavelengths in the near infrared (NIR) are applied in optical communication, metrology, imaging and spectroscopy, for instance, and may comprise silicon (Si), germanium (Ge) and SiGe alloys. A monolithic integration of optics and electronics parts is desired in view of system performance and small size.
It is an object of the present invention to provide a monolithically integrated photodetector semiconductor device for near-infrared applications.
This object is achieved with the near-infrared photodetector semiconductor device according to claim 1. Embodiments derive from the dependent claims.
The definitions as described above also apply to the
following description unless stated otherwise. The term
"trench" will be used to denote any suitable opening or recess of arbitrary shape, which can be etched into a semiconductor layer.
The near-infrared photodetector semiconductor device
comprises a semiconductor layer of a first type of
conductivity with a main surface, a trench or a plurality of trenches in the semiconductor layer at the main surface, a SiGe alloy layer in the trench or the plurality of trenches, and an electrically conductive filling material of a second type of conductivity in the trench or the plurality of trenches, the second type of conductivity being opposite to the first type of conductivity. The first type of
conductivity may be n-type conductivity and the second type of conductivity p-type conductivity, for instance, or vice versa .
In an embodiment of the near-infrared photodetector
semiconductor device, the SiGe alloy layer is doped for the second type of conductivity, and the filling material comprises a portion of the SiGe alloy layer. The SiGe alloy layer may fill the trench or the plurality of trenches.
A further embodiment comprises a silicon layer in the trench or the plurality of trenches. The silicon layer may
especially comprise polysilicon. The SiGe alloy layer and the silicon layer may fill the trench or the plurality of trenches .
In a further embodiment the silicon layer is doped for the second type of conductivity, and the filling material comprises a portion of the silicon layer. In this case the SiGe alloy layer may be undoped or intrinsically doped.
In a further embodiment the SiGe alloy layer is doped for the second type of conductivity, the silicon layer is undoped or intrinsically doped, and the filling material comprises a portion of the SiGe alloy layer.
A further embodiment comprises a contact region of the first type of conductivity in the semiconductor layer at the main surface, the contact region being at a distance from the trench or the plurality of trenches. An electrically
conductive contact connection is electrically conductively connected with the filling material, and a further
electrically conductive contact connection is electrically conductively connected with the contact region.
In further embodiments the trench or at least one of the trenches of the plurality of trenches has a smooth or a grooved sidewall.
In further embodiments the semiconductor layer of the first type of conductivity is silicon, and the SiGe alloy layer is epitaxially grown on the silicon. A differential or selective epitaxy of the SiGe alloy layer enables to vary and adapt the germanium content during the deposition of the SiGe alloy layer .
The arrangement of the SiGe alloy layer in the trench or the plurality of trenches increases the absorption length and thus improves the light sensitivity of the photodetector semiconductor device in the spectral range of red and near- infrared light.
The following is a more detailed description of examples of the photodetector semiconductor device in conjunction with the appended figures.
Figure 1 is a cross section of a photodetector semiconductor device comprising trenches with smooth sidewalls.
Figure 2 is a cross section of a further photodetector
semiconductor device comprising trenches with smooth sidewalls . Figure 3 is a top view of an arrangement of the trenches.
Figure 4 is a top view of a further arrangement of the
trenches .
Figure 5 is a cross section of a photodetector semiconductor device comprising trenches with grooved sidewalls.
Figure 6 is a cross section of a further photodetector
semiconductor device comprising trenches with grooved sidewalls.
Figure 7 is a diagram showing examples of the relative
germanium content x as a function of the level h above a silicon surface.
Figure 1 is a cross section of a photodetector semiconductor device. At least one trench 2 is formed at a main surface 10 of a semiconductor layer 1, which may especially be silicon. The semiconductor layer 1 has a first type of conductivity. The number of trenches is arbitrary; Figure 1 shows a plurality of three trenches 2, by way of example. A SiGe alloy layer 3 is arranged in each trench 2 and on the main surface 10. If the semiconductor layer 1 is silicon, the SiGe alloy layer 3 can be epitaxially grown on the silicon. The SiGe alloy layer 3 comprises silicon and germanium, and it may also comprise an optional additive like carbon, for instance. The shape of the trenches 2 can be adapted to the epitaxial growth. The sidewalls of the trenches 2 can be perpendicular or inclined with respect to the main surface 10. The sidewalls can be smooth, as shown in Figure 1, or rough. Bottom areas of the trenches 2 can be flat or curved. The SiGe alloy layer 3 has a second type of conductivity opposite to the first type of conductivity. The first type of conductivity may be n-type conductivity and the second type of conductivity p-type conductivity, or vice versa. The SiGe alloy layer 3 may completely fill the trenches 2, as shown in Figure 1. In this case the large volume of the SiGe alloy layer 3 enhances the absorption of near-infrared light.
A contact region 4 of the first type of conductivity may be arranged in the semiconductor layer 1 at the main surface 10 and at a distance from the trenches 2. The contact region 4 comprises a doping concentration that is higher than the doping concentration of the semiconductor layer 1 in order to allow the formation of an ohmic contact. A contact connection 6 comprising an electrically conductive material is arranged contacting the SiGe alloy layer 3, and a further contact connection 8 comprising an electrically conductive material is arranged contacting the contact region 4. The contact connections 6, 8 may be formed by plugs in an intermetal dielectric and may connect the SiGe alloy layer 3 and the contact region 4 with conductor tracks 7, 9 in a metal layer of a wiring, for example. Details of the wiring, which are arbitrary, are not shown in Figure 1.
Figure 2 is a cross section of a further photodetector semiconductor device. Elements of the photodetector
semiconductor device according to Figure 2 that correspond to elements of the photodetector semiconductor device according to Figure 1 are designated with the same reference numerals. The photodetector semiconductor device according to Figure 2 comprises a silicon layer 5 in the trenches 2. The silicon layer 5 may especially comprise polysilicon. The SiGe alloy layer 3 and the silicon layer 5 may completely fill the trenches 2. The silicon layer 5 may also be applied on the SiGe alloy layer 3 above the main surface 10, as shown in Figure 2.
If the SiGe alloy layer 3 is doped for the second type of conductivity, the silicon layer 5 may be undoped or
intrinsically doped. In this case the contact connection 6 is arranged in such a manner that it contacts the SiGe alloy layer 3. As the refractive index of silicon is lower than the refractive index of SiGe, total reflection of light at the boundary between the silicon layer 5 and the SiGe alloy layer 3 yields a longer optical path and enhanced light absorption.
The silicon layer 5 may be doped for the second type of conductivity, especially in situ during its deposition. If the silicon layer 5 is doped for the second type of
conductivity, the SiGe alloy layer 3 may be undoped or intrinsically doped. In this case the contact connection 6 is arranged in such a manner that it contacts the silicon layer 5. If the SiGe alloy layer 3 is undoped, the space charge region extends over the entire portion of the SiGe alloy layer 3 that is arranged within the trenches 2, and this results in a better carrier collection efficiency.
Figure 3 is a top view of an arrangement of the trenches 2 for an example in which the trenches 2 are cylindrical. The SiGe alloy layer 3 and the conductor track 7 are indicated in Figure 3 in order to facilitate the comparison with the cross section shown in Figure 1.
Figure 4 is a top view of a further arrangement of the trenches 2 for an example in which the trenches 2 have longitudinal extensions and are parallel to each other. The shapes and arrangements of the trenches 2 are not restricted to these examples, but may vary according to individual requirements .
Longer optical paths can be achieved with trenches 2
comprising grooved or corrugated sidewalls. The trenches 2 can be etched into the semiconductor layer 1, and the etching process can be performed in such a way that it yields grooved or corrugated surfaces of the sidewalls. Such etching
processes are known per se in semiconductor technology and need not be described here.
Figure 5 is a cross section of a photodetector semiconductor device comprising trenches 2 with grooved sidewalls. Elements of the photodetector semiconductor device according to Figure 5 that correspond to elements of the photodetector
semiconductor device according to Figure 1 are designated with the same reference numerals. The shape of the sidewalls makes the difference between the devices according to Figures 1 and 5.
Figure 6 is a cross section of a further photodetector semiconductor device comprising trenches 2 with grooved sidewalls. Elements of the photodetector semiconductor device according to Figure 6 that correspond to elements of the photodetector semiconductor device according to Figure 2 are designated with the same reference numerals. The shape of the sidewalls makes the difference between the devices according to Figures 2 and 6.
Figure 7 is a diagram showing some examples of the relative germanium content x of the Sii-xGex alloy in the SiGe alloy layer 3 as a function of the level h above the surface on which the SiGe alloy layer 3 is grown. The Sii-xGex alloy may especially be epitaxially grown on a silicon surface, as indicated on the right side of the diagram. The relative germanium content x of the alloy Sii_xGex can be varied during the deposition of the SiGe alloy layer 3, so that the
properties of the SiGe alloy layer 3 can be adapted to the requirements of individual embodiments.
The line x' in the diagram of Figure 7 represents an example of a continuous linear decrease of the germanium content x from h = 0 to the maximal level hmax, which corresponds to the total thickness of the SiGe alloy layer 3. The line c' ' represents an example of a continuous linear increase of the germanium content x from h = 0 to the maximal level hmax. The relative germanium content x may instead be essentially constant, so that the SiGe alloy layer 3 is homogeneous. Such a SiGe alloy layer 3 is represented in Figure 1 by the horizontal line x' ' ' .
An integrated circuit of the photodetector semiconductor device can be formed by a conventional CMOS process, for instance, which is known per se and need not be described here. The formation of the trenches 2 and the SiGe alloy layer 3 may take place after the CMOS process. Instead, the trenches 2 can be etched at an earlier stage of the CMOS process. In this case the trenches 2 are subsequently filled with a sacrificial filling, which may be an oxide of the semiconductor material, for instance. After the CMOS process, the sacrificial filling is removed, which may be effected by wet etching, for instance, to open the trenches 2, and the SiGe alloy layer 3 is subsequently deposited. Deep trenches provide long optical paths within the SiGe alloy layer in the vertical direction. A differential or selective epitaxial growth of the SiGe alloy layer guarantees monocrystalline growth with low defect density at the Si/SiGe interface, thus enabling the formation of photodetectors with low dark current. The efficiency in photocarrier collection is enhanced by an increase of the width of the space charge region within the SiGe alloy. The efficiency in photocarrier collection is also enhanced when the relative germanium content of the SiGe alloy layer continuously increases or decreases with increasing distance from the silicon surface on which the SiGe alloy layer is epitaxially grown. Hence an integrated near-infrared photodetector semiconductor device comprising the described features has many advantages and is favourable for a wide variety of applications.
List of reference numerals
1 semiconductor layer
2 trench
3 SiGe alloy layer
4 contact region
5 silicon layer
6 contact connection
7 conductor track
8 further contact connection
9 further conductor track
10 main surface

Claims

Claims
1. A near-infrared photodetector semiconductor device, comprising :
a semiconductor layer (1) of a first type of conductivity with a main surface (10),
a trench or a plurality of trenches (2) in the semiconductor layer (1) at the main surface (10),
a SiGe alloy layer (3) in the trench or the plurality of trenches (2), and
an electrically conductive filling material (3, 5) of a second type of conductivity in the trench or the plurality of trenches (2), the second type of conductivity being opposite to the first type of conductivity.
2. The near-infrared photodetector semiconductor device according to claim 1, further comprising:
a silicon layer (5) in the trench or the plurality of
trenches (2 ) .
3. The near-infrared photodetector semiconductor device according to claim 2, wherein the silicon layer (5) is doped for the second type of conductivity, and the filling material comprises a portion of the silicon layer (5) .
4. The near-infrared photodetector semiconductor device according to claim 3, wherein the SiGe alloy layer (3) is undoped or intrinsically doped.
5. The near-infrared photodetector semiconductor device according to claim 2, wherein the SiGe alloy layer (3) is doped for the second type of conductivity, the silicon layer (5) is undoped or intrinsically doped, and the filling material comprises a portion of the SiGe alloy layer (3) .
6. The near-infrared photodetector semiconductor device according to one of claims 2 to 5, wherein the silicon layer (5) comprises polysilicon.
7. The near-infrared photodetector semiconductor device according to one of claims 2 to 6, wherein the SiGe alloy layer (3) and the silicon layer (5) fill the trench or the plurality of trenches (2) .
8. The near-infrared photodetector semiconductor device according to one of claims 1 to 3, wherein the SiGe alloy layer (3) is doped for the second type of conductivity, and the filling material comprises a portion of the SiGe alloy layer (3) .
9. The near-infrared photodetector semiconductor device according to one of claims 1 to 8, wherein the first type of conductivity is n-type conductivity, and the second type of conductivity is p-type conductivity.
10. The near-infrared photodetector semiconductor device according to one of claims 1 to 8, wherein the first type of conductivity is p-type conductivity, and the second type of conductivity is n-type conductivity.
11. The near-infrared photodetector semiconductor device according to one of claims 1 to 10, further comprising:
a contact region (4) of the first type of conductivity in the semiconductor layer (1) at the main surface (10), the contact region (4) being at a distance from the trench or the
plurality of trenches (2),
an electrically conductive contact connection (6)
electrically conductively connected with the filling
material, and
a further electrically conductive contact connection (8) electrically conductively connected with the contact region (4) .
12. The near-infrared photodetector semiconductor device according to one of claims 1 to 11, wherein the trench or at least one of the trenches of the plurality of trenches (2) has a smooth sidewall .
13. The near-infrared photodetector semiconductor device according to one of claims 1 to 11, wherein the trench or at least one of the trenches of the plurality of trenches (2) has a grooved sidewall.
14. The near-infrared photodetector semiconductor device according to one of claims 1 to 13, wherein the semiconductor layer (1) comprises silicon and the SiGe alloy layer (3) is epitaxially grown on the silicon.
15. The near-infrared photodetector semiconductor device according to claim 5, wherein
the semiconductor layer (1) is silicon,
the SiGe alloy layer (3) is epitaxially grown on the silicon in the trench or the plurality of trenches (2) and on the main surface (10),
the silicon layer (5) is applied on the SiGe alloy layer (3) in the trench or plurality of trenches (2) and above the main surface (10), the SiGe alloy layer (3) and the silicon layer (5) completely fill the trench or the plurality of trenches (2), and
a contact connection (6) contacts the SiGe alloy layer (3) .
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