U.S. patent application number 15/926499 was filed with the patent office on 2018-09-27 for laser diode module.
The applicant listed for this patent is Infineon Technologies AG. Invention is credited to Gianmaria Furlan, Maurizio Galvano, Andrea Logiudice, Franco Mignoli.
Application Number | 20180278011 15/926499 |
Document ID | / |
Family ID | 63450370 |
Filed Date | 2018-09-27 |
United States Patent
Application |
20180278011 |
Kind Code |
A1 |
Galvano; Maurizio ; et
al. |
September 27, 2018 |
LASER DIODE MODULE
Abstract
A laser diode module is described herein. In accordance with a
first exemplary embodiment, the laser diode module includes a first
semiconductor die including at least one electronic switch, and a
second semiconductor die including at least one laser diode. The
second semiconductor die is bonded on the first semiconductor die
using a chip-on-chip connecting technology to provide electrical
connection between the electronic switch and the laser diode.
Inventors: |
Galvano; Maurizio; (Padova,
IT) ; Furlan; Gianmaria; (Padova, IT) ;
Logiudice; Andrea; (Montegrotto Terme (PD), IT) ;
Mignoli; Franco; (Verona, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineon Technologies AG |
Neubiberg |
|
DE |
|
|
Family ID: |
63450370 |
Appl. No.: |
15/926499 |
Filed: |
March 20, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62475633 |
Mar 23, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 7/4814 20130101;
H01S 5/02244 20130101; H01S 5/32341 20130101; G01S 7/4813 20130101;
H01S 5/0215 20130101; H01S 5/0428 20130101; H01S 5/0261 20130101;
H01S 5/02276 20130101; G01S 7/484 20130101; H01S 5/0224 20130101;
H01S 5/04257 20190801 |
International
Class: |
H01S 5/02 20060101
H01S005/02; H01S 5/022 20060101 H01S005/022; G01S 7/484 20060101
G01S007/484 |
Claims
1. A laser diode module comprising: a first semiconductor die
including at least one electronic switch; and a second
semiconductor die including at least one laser diode, wherein the
second semiconductor die is bonded on the first semiconductor die
using a chip-on-chip connecting technology to provide electrical
connection between the electronic switch, the laser diode.
2. The laser diode module of claim 1, further comprising: a third
semiconductor die including at least one buffer capacitor; the
third semiconductor die being bonded on the first semiconductor die
using a chip-on-chip connecting technology.
3. The laser diode module of claim 1, wherein the first
semiconductor die further includes at least one driver circuit
coupled to the electronic switch and configured to drive the
electronic switch on and off.
4. The laser diode module of claim 1, wherein the second
semiconductor die has two electrodes on the same side and is
flip-chip mounted on the first semiconductor die.
5. The laser diode module of claim 2, wherein the third
semiconductor die has two electrodes on the same side and is
flip-chip mounted on the first semiconductor die.
6. The laser diode module of claim 1, wherein the second
semiconductor die has a first electrode on a top side and a second
electrode on a bottom side of the second semiconductor die, the
second electrode being bonded to the first semiconductor die using
chip-on-chip connecting technology and the first electrode being
connected to the first semiconductor die using a clip or a bond
wire.
7. The laser diode module of claim 1, wherein the electronic switch
and the laser diode are connected in series between a supply
terminal and a ground terminal.
8. The laser diode module of claim 2, wherein the electronic switch
and the laser diode are connected in series between a supply
terminal and a ground terminal, and wherein the buffer capacitor is
connected between a supply terminal and a ground terminal.
9. The laser diode module of claim 1, further comprising: wherein
the first semiconductor die includes at least one buffer
capacitor.
10. The laser diode module of claim 1, further comprising: a lead
frame, on which the first semiconductor die is attached.
11. The laser diode module of claim 10, wherein the first
semiconductor die is flip-chip mounted on the lead frame without
using bond wires.
12. The laser diode module of claim 10, further comprising: at
least one capacitor attached on the lead-frame.
13. A laser diode module comprising: a lead frame; a first
semiconductor die including at least one electronic switch and
attached to the lead-frame; at least one capacitor attached to the
lead frame; and a second semiconductor die including at least one
laser diode, the second semiconductor die being arranged between
the lead frame and a metal cap or a metal clip, so that a bottom
side of the second semiconductor die contacts the lead frame and a
top side of the second semiconductor die contacts the clip or the
metal cap.
14. The laser diode module of claim 13, wherein the first
semiconductor die is flip-chip mounted on the lead frame without
using bond wires.
15. The laser diode module of claim 13, wherein the at least one
capacitor is surface mounted on the lead frame without using bond
wires.
16. A laser diode module comprising: a first semiconductor die
including at least one electronic switch; a second semiconductor
die including at least one laser diode; and a third semiconductor
die including at least one buffer capacitor, wherein the first and
the third semiconductor die are embedded in one chip package and
the second semiconductor die is a bare die bonded to a surface of
the chip package.
17. The laser diode module of claim 16, wherein the chip package is
an enhanced wafer level ball grid array (eWLB) package.
18. The laser diode module of claim 16, wherein the second
semiconductor is soldered solder pads arranged either on the top
side or the bottom side of the chip package.
19. The laser diode module of any of claim 16, wherein the
electronic switch and the laser diode are connected in series
between a supply terminal and a ground terminal, and wherein the
buffer capacitor is connected between a supply terminal and a
ground terminal.
20. A laser diode module comprising: a first semiconductor die
including at least one electronic switch; and a second
semiconductor die including at least one laser diode, wherein the
first semiconductor die and the second semiconductor die are bare
dies embedded in a circuit board.
21. The laser diode module of claim 20 further comprising: a third
semiconductor die including at least one buffer capacitor, the
third semiconductor die being embedded in the circuit board.
22. The laser diode module of claim 20, wherein a buffer capacitor
is included in the first semiconductor die.
23. The laser diode module of claim 22, wherein the buffer
capacitor is configured to buffer a supply voltage.
24. The laser diode module of any of claim 20, further comprising:
a fourth semiconductor chip including a micro-scanning mirror.
25. The laser diode module of any of claim 20, wherein the
electronic switch and the laser diode are connected in series
between a supply terminal and a ground terminal.
26. The laser diode module of claim 21, wherein the electronic
switch and the laser diode are connected in series between a supply
terminal and a ground terminal, and wherein the buffer capacitor is
connected between a supply terminal and a ground terminal.
27. The laser diode module of claim 21, wherein the third
semiconductor die is arranged on a first metallization layer of the
circuit board.
28. The laser diode module of any of claim 20, wherein the second
semiconductor die is arranged between a first metallization layer
and a second metallization layer of the circuit board.
29. The laser diode module of claim 28, wherein the first
semiconductor die is arranged between the second metallization
layer and a third metallization layer of the circuit board.
30. A laser diode module comprising: a first semiconductor die
including at least one electronic switch; and a second
semiconductor die including at least one laser diode, wherein the
first semiconductor die is a bare die embedded in an intermediate
level of a circuit board, and wherein the second semiconductor die
is arranged in a top or a bottom level of the circuit board.
31. The laser diode module of claim 30, further comprising: at
least one buffer capacitor embedded in an intermediate level of a
circuit board.
Description
[0001] This Application claims the benefit of U.S. Provisional
Application 62/475,633, filed Mar. 23, 2017, the entire content of
which is incorporated herein by reference.
TECHNICAL FIELD
[0002] This disclosure in general relates to aspects Laser diode
packaging, in particular for system-in-a-chip (SoC) or
system-in-a-package (SiP) LIDAR solutions.
BACKGROUND
[0003] Light Detection and Ranging (LIDAR) relates to a surveying
method for measuring distance to an object (referred to as target)
by illuminating the target with pulsed laser light, wherein the
distance information may be obtained from the time-of-flight (TOF)
of the light pulse travelling from the light source to the target
and back to the detector. This time-of-flight is sometimes also
referred to as round trip delay time (RTDT); the measured distance
is basically the product between the RTDT and the speed of light.
LIDAR is used, for example, in so-called time-of-flight cameras
(TOF cameras), which allows mapping depth information to individual
pixels and capturing the entire scene within the field of view of
the TOF camera simultaneously. In contrast thereto, a scanning
LIDAR scans the scene pointwise by deflecting the laser with, e.g.,
a mirror such as a microscanner (also referred to as micro-scanning
mirror).
[0004] The irradiance (power per unit area) of the reflected light
pulse arriving at the detector decreases with increasing distance
of the target. To achieve a measurement range of up to several 10
or 100 meters, the radiant power of the emitted laser light (and
thus the electrical power of the laser diode) is comparably high.
However, to ensure that the laser pulses are harmless for the eyes
of persons standing nearby, the laser pulses have to be comparably
short to limit the radiant energy of a laser pulse. For a
rectangular shaped pulse (power over time), the pulse energy would
be proportional to the product of pulse width and power. In a
realistic example, the peak power of a laser pulse may be up to 80
W or more with a pulse width in the range of 1 ns to 100 ns. To
generate such short pulses the driver electronics used to drive the
laser diode should be capable of switching the load current of the
laser diode with extremely short rise and fall times.
SUMMARY
[0005] A laser diode module is described herein. In accordance with
a first exemplary embodiment, the laser diode module includes a
first semiconductor die including at least one electronic switch,
and a second semiconductor die including at least one laser diode.
The second semiconductor die is bonded on the first semiconductor
die using a chip-on-chip connecting technology to provide
electrical connection between the electronic switch and the laser
diode.
[0006] In accordance with a second exemplary embodiment, the laser
diode module includes a lead frame, a first semiconductor die
including at least one electronic switch and attached to the
lead-frame, at least one capacitor attached to the lead frame; and
a second semiconductor die including at least one laser diode. The
second semiconductor die is arranged between the lead frame and a
metal cap or a metal clip, so that a bottom side of the second
semiconductor die contacts the lead frame and a top side of the
second semiconductor die contacts the clip or the metal cap.
[0007] In accordance with a third exemplary embodiment, the laser
diode module includes a first semiconductor die with at least one
electronic switch, a second semiconductor die including at least
one laser diode, and a third semiconductor die including at least
one buffer capacitor. The first and the third semiconductor die are
embedded in one chip package and the second semiconductor die is a
bare die bonded to a surface of the chip package.
[0008] In accordance with a third exemplary embodiment the laser
diode module includes a first semiconductor die including at least
one electronic switch, and a second semiconductor die including at
least one laser diode. The first semiconductor die and the second
semiconductor die are bare dies embedded in a circuit board.
[0009] In accordance with a third exemplary embodiment the laser
diode module includes a first semiconductor die including at least
one electronic switch and a second semiconductor die including at
least one laser diode. The first semiconductor die is a bare die
embedded in an intermediate level of a circuit board, whereas the
second semiconductor die is arranged in a top or a bottom level of
the circuit board.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention can be better understood with reference to the
following description and drawings. The components in the figures
are not necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. Moreover, in the
figures, like reference numerals designate corresponding parts. In
the drawings:
[0011] FIGS. 1A and 1B illustrate a circuit diagram (FIG. 1A) of a
laser diode and an electronic switch for switching the laser diode
and a schematic drawing (FIG. 1B) of a corresponding chip
package.
[0012] FIG. 2 illustrates an electric equivalent circuit of the
laser diode package including parasitic inductances.
[0013] FIG. 3 illustrates a cross sectional view of one exemplary
implementation of a laser diode.
[0014] FIG. 4 illustrates a cross sectional view of an integrated
silicon capacitor.
[0015] FIG. 5 illustrates one example of a system-on-chip (SoC)
including laser diode, electronic switch, capacitances and driver
circuit.
[0016] FIG. 6 illustrates an isometric view of another example of a
system-on-chip (SoC) similar to FIG. 5.
[0017] FIGS. 7A and 7B illustrates top view (FIG. 7A) and side view
(FIG. 7B) of an exemplary system-in-package, in which a laser diode
is chip-on-chip mounted on a driver IC arranged on a lead-frame
together with silicon capacitors.
[0018] FIG. 8 illustrates an alternative example similar to FIGS.
7A and 7B.
[0019] FIGS. 9A, 9B and 9C illustrate an alternative example
similar to FIGS. 7A and 7B, in which the laser diode is arranged in
a separate housing and soldered onto the lead frame and/or covered
with a transparent mold compound.
[0020] FIG. 10 illustrates a cross sectional view of one example of
a system-in-package (SiP), in which laser diode, capacitors,
electronic switch and driver circuit are embedded in a multilayer
circuit board.
[0021] FIG. 11 illustrates a cross sectional view of another
example of a system-in-package (SiP) similar to FIG. 10
additionally including a micro-scanning mirror and the respective
micro-mirror driver IC.
[0022] FIG. 12 illustrates a cross sectional view of another
example of a system-in-package (SiP) similar to FIG. 10.
[0023] FIGS. 13A and 13B illustrate another example of a
system-in-package (SiP), in which driver IC and capacitors are
arranged in an eWLB package with the laser diode(s) directly
soldered onto the eWLB package.
DETAILED DESCRIPTION
[0024] FIGS. 1A and 1B illustrate a laser diode and a portion of a
driver circuit used to drive the laser diode. FIG. 1A is a circuit
diagram of a laser diode D.sub.L and an electronic switch T.sub.L
for switching the laser diode D.sub.L on and off. Accordingly, a
series circuit of laser diode D.sub.L and electronic switch T.sub.L
is coupled between ground terminal GND and supply terminal, at
which a supply voltage V.sub.S is applied. At least one capacitor
(in the present example a parallel circuit of capacitors C.sub.1
and C.sub.2) is connected in parallel to the series circuit of
laser diode D.sub.L and electronic switch T.sub.L in order to
buffer the supply voltage V.sub.S and provide load current to the
laser diode D.sub.L. The electronic switch T.sub.L may be a MOSFET
or any other suitable transistor type (e.g. BJT). The control (gate
or base) terminal of the electronic switch T.sub.L is labelled ON
in the present example. Generally the buffer capacitance provided
by capacitors C.sub.1 and C.sub.2 is needed to allow fast
transients of the load current.
[0025] FIG. 1B is a schematic drawing of a laser diode module 1
with a chip package including the circuit of FIG. 1A. Accordingly,
the chip package includes a first semiconductor die including the
electronic switch T.sub.L, a second semiconductor die including the
laser diode D.sub.L, and at least a third semiconductor die
providing the buffer capacitance. Corresponding to FIG. 1A, two
separate capacitors are used in the present example. A lead frame
11 provides three pins corresponding to the supply terminal
(voltage V.sub.S), the ground terminal GND and the control terminal
ON, wherein the middle terminal is the supply terminal. The
semiconductor dies including the buffer capacitors C.sub.1 and
C.sub.2 are directly (i.e. without using bond wires) bonded (e.g.
soldered) to the lead frame 11 and provide a buffer capacitance
between the pins representing ground and supply terminal. The
bottom metallization of the semiconductor die including the MOSFET
T.sub.L represents the drain electrode of the MOSFET and is
directly bonded (e.g. soldered) to the pin representing the supply
terminal. The gate electrode in the top metallization layer of
MOSFET T.sub.L is connected to the pin representing the control
terminal ON via a bond wire 12'. Similarly, the source electrode in
the top metallization layer of MOSFET T.sub.L is connected to the
anode electrode on the top surface of laser diode D.sub.L via bond
wires 12. The cathode electrode at the bottom surface of the laser
diode D.sub.L is directly bonded (e.g. soldered) to the lead frame
11.
[0026] FIG. 2 illustrates a simplified electrical equivalent
circuit of the laser diode module 1 of FIG. 1. Additionally, the
circuit of FIG. 2 includes a gate driver circuit 41 coupled to the
control electrode of the MOSFET T.sub.L and configured to generate
drive signals suitable to switch the MOSFET T.sub.L on and off in
accordance with a logic signal SON. Apart from the gate driver 41,
the circuit of FIG. 2 is substantially the same as in FIG. 1A
except the inductors L.sub.D, L.sub.C and L.sub.G that represent
parasitic inductances of the bond wires 12 (corresponds to
inductance L.sub.D), the electric connections between the
capacitors C.sub.1 and C.sub.2 and the laser diode D.sub.L
(corresponds to inductance L.sub.C), and the electric connection
(bond wire 12') between the control terminal ON and the actual
control electrode of the MOSFET T.sub.L (corresponds to inductance
L.sub.G).
[0027] In LIDAR systems the measurement range depends on the
radiant power of the laser pulse. However, to limit the pulse
energy (to protect the eyes of persons in the environment of the
LIDAR system) the laser pulses need to be rather short. The voltage
drop V.sub.LEFF across the effective parasitic inductance L.sub.EFF
(L.sub.EFF=L.sub.C+L.sub.D) is given by
V.sub.LEFF=L.sub.EFF.DELTA.i.sub.L/t.sub.rise and
V.sub.LEFF=L.sub.EFF.DELTA.i.sub.L/t.sub.fall
wherein .DELTA.i.sub.L is change of the load current (e.g. from 0 A
to 40 A or from 40 A to 0 A), t.sub.rise is the respective rise
time and t.sub.fall respective fall time. Assuming an effective
inductance of 5 nH and a rise time of 2 ns yields a voltage drop of
100V. Accordingly, the system including the capacitors would have
to be designed for a voltage of more than 110V (assuming 10V
voltage drop across the laser diode and the MOSFET) in order to
achieve the desired peak current within the desired rise time. It
is noted, that a rise time of 2 ns may be too long for some
applications. With the integration approach as illustrated in FIG.
1B, the inductance L.sub.EFF may be significantly reduced (probably
below, e.g., 2 nH or even below 1 nH). The remaining inductance is
predominatly caused by the bond wires 12 used to connect the MOSFET
T.sub.L and the laser diode D.sub.L. For example, the voltage drop
V.sub.LEFF is still 80V when reducing the inductance L.sub.EFF to 1
nH when the load current is to be ramped up to 40 A within a rise
time of 0.5 ns.
[0028] Before describing various examples of laser modules using a
system-on-chip (SoC) or a system-in-package (SiP) approach, which
may help to further reduce effective inductance L.sub.EFF, the
structure of a laser diode and an integrated capacitor is described
below with reference to FIGS. 3 and 4. FIG. 3 illustrates one
exemplary implementation of a laser diode. Accordingly, the laser
diode 20 includes a substrate 2, on which a plurality of functional
layers (layers 25, 26 and 27) are formed using epitaxial growth. In
the depicted example, the substrate 2 includes a GaN semiconductor
material, on which a silicon-doped AlGaN cladding layer 28 and a
silicon-doped GAN waveguide layer 27 are arranged. Thereabove, an
active layer 25 having a multiple quantum well structure (MQW
structure) having 1 to 5 GaInN quantum films and GaN barrier layers
is provided. A magnesium-doped GaN waveguide layer 26 and a
magnesium-doped AlGaN cladding layer 22 are applied on the active
layer. Furthermore, one or a plurality of contact layers composed,
for example, of magnesium-doped GaN can additionally be applied on
the cladding layer 22, while one or a plurality of intermediate
layers (not shown) can likewise be arranged between the substrate 2
and the cladding layer. The depicted sequence of layers forming the
laser diode 20 is suitable for generating electromagnetic radiation
in an ultraviolet to green, e.g. in a blue wavelength range.
[0029] As an alternative to the nitride-based semiconductor
materials described herein, the laser diode may, for example, also
comprise phosphide- and arsenide-based semiconductor materials such
as a GaAs substrate 2 and thereabove a 100 nm thick intermediate
layer 28 composed of AlGaAs having an Al proportion of
approximately 40% of the group III materials and/or composed of
InGaP having an In proportion of approximately 50% of the group III
materials, thereabove a 2 .mu.m thick InAlP wavelength layer 27,
thereabove a 100 nm thick InGaAlP/InGaP quantum film/barrier layer
MQW structure 25 having an In proportion of approximately 50% and
an Al proportion of approximately 25%, thereabove a 2 .mu.m thick
InAlP waveguide layer 26, and, thereabove, a 100 nm thick InGaP
intermediate layer 22 and furthermore a 300 nm thick GaAs contact
layer (not shown). A sequence of semiconductor layers of this type
may be suitable for generating green to infrared electromagnetic
radiation, and particularly electromagnetic radiation in a red
wavelength range. The functional layers may be formed on the
substrate 2 using epitaxial growth. As an alternative thereto, the
semiconductor layer sequence may be formed using thin-film
technology. That means that the functional layers are grown on a
substrate and subsequently transferred to a carrier substrate,
which then forms the substrate 2 of the depicted sequence of
semiconductor layers. Depending on the growth technique the
n-conducting layers (or the p-conducting layers) may face the
substrate 2.
[0030] The laser diode is effected may be electrically contacted
via electrode 21 arranged on the surface of the substrate 1 spaced
apart from the functional layers 25, 26, and 27 and via electrode
23 arranged on the stack of functional layers 25, 26, and 27 as
shown in FIG. 3. Thereby, the electrodes 21 and 23 may each have
one or more layers comprising Ag, Au, Sn, Ti, Pt, Pd, Cr, Ni and/or
Ge. Although a specific example of a laser diode has been described
above, it is understood that various types of laser diodes are as
such known and the exemplary embodiments described herein are not
limited to any specific type of laser diode. It is noted that, in
the example of FIG. 3 anode and cathode (electrodes 21 and 23) of
the laser diode are at the same side of the semiconductor substrate
2. However, a very similar structure may be formed that has its
electrodes on opposing sides of the semiconductor substrate. Both
types of laser diodes may be used in accordance with various
exemplary embodiments described herein. One example of a laser
diode is described, e.g., in the publication US 2011/0188530
A1.
[0031] FIG. 4 illustrates a cross-sectional view of one example of
a capacitor 30 integrated in a semiconductor body 31. A plurality
of trenches 37, 38 are formed in the semiconductor body 31. A first
electrode 34 extends on the surface of the silicon body throughout
the trenches 37, 38. The purpose of the trenches is basically to
increase the area of the electrodes and thus the achievable
capacitance. The first electrode 34 is covered by an insulating
dielectric layer 35, and a second electrode 36 is arranged on the
dielectric 35 and extends throughout the trenches 37, whereas
trench 38 is filled with electrode material and is electrically
connected with the first electrode 34. In the present example
polycrystalline silicon is used as electrode material. It is
understood, however, that other materials may be used instead. On
the top surface of the semiconductor body, the electrodes 34 and 36
may be contacted by metal electrodes/terminals 32 and 33,
respectively. It is noted that, in the example of FIG. 4 both
electrodes/terminals of the capacitor 30 are at the same side of
the semiconductor body 31. However, a very similar structure may be
formed that has its electrodes on opposing sides of the
semiconductor body 31. Both types of capacitors may be used in
accordance with various exemplary embodiments described herein. It
is noted that trench capacitors as illustrated in FIG. 4 are as
such know and commercially available and are thus not further
discussed herein.
[0032] FIG. 5 illustrates one example of a system-on-chip (SoC)
approach to form a laser diode module 1 including laser diode (cf.
FIG. 2, laser diode D.sub.L), an electronic switch 40 with (gate)
driver circuit 41 (cf. FIG. 2, driver circuit 41) and capacitances
30 (cf. FIG. 2, buffer capacitors C.sub.1, C.sub.2). In the present
example, four electronic switches 40a, 40b, 40c, and 40d
(collectively 40) and respective driver circuits 41 are integrated
in one semiconductor die referred to as driver IC 4 in FIG. 5 (cf.
FIG. 2). The driver IC 4 includes a semiconductor substrate 4'
(e.g. a silicon substrate) and chip interconnections 42 in the
metallization layer arranged on the top surface of the
semiconductor substrate 4'. The chip interconnections 42 allow for
directly bonding (i.e. without using bond wires) the laser diodes
20 and capacitors 30 onto the driver IC 4 using a chip-on-chip
bonding technique. As can be seen in FIG. 5, four laser diodes 20a,
20b, 20c, 20d (collectively 20) are flip-chip mounted on the driver
IC 4. Similarly, the capacitors 30a, 30b, 30c, and 30d
(collectively 30) are also flip-chip mounted on the driver IC
4.
[0033] In the present example, the laser diodes 20 have both
electrodes (anodes and cathodes) on the same side of the
semiconductor die (cf. FIG. 3, substrate 2), in which the diodes
are integrated. Similarly, the capacitors 30 have their electrodes
on the same side of the semiconductor die(s), in which the
capacitors are integrated (cf. FIG. 4, silicon body 31). Having
both electrodes on the same side allows a flip chip mounting of the
capacitors 30 and the laser diodes 20 on the driver IC 4, which
entails very short electrical lines between the laser diode, the
electronic switches and the capacitors. Short electrical lines
result in correspondingly low inductances (e.g. an effective
inductance L.sub.EFF below 0.5 nH or even below 0.3 nH). In the
present example, the laser diodes 20 are arranged vertically above
that portion of the driver IC 4, in which the electronic switches
40 are located that switch the load currents of the laser diodes
20. In the present example, four laser diodes are included in the
laser diode module 1. It is understood that, in other examples,
more or less laser diodes (even a single laser diode) may be
included in one laser diode module. Although the capacitors 30 are
chip-on-chip mounted onto the driver IC 4 in the present example,
trench capacitors may be also integrated together with the
electronic switches 40 and the (gate) driver circuits 41 in one
semiconductor die.
[0034] In the example of FIG. 5 the radiation emitted by the laser
diodes propagates along an axis parallel to the top surface of the
driver IC 4. FIG. 6 illustrates an SoC laser diode module including
one or more laser diodes which emit radiation along an axis
perpendicular to the top surface of the driver IC 4. Apart from
this, the example of FIG. 6 is substantially the same as the
previous example of FIG. 5. However, due to the different direction
of the radiation in the examples of FIGS. 5 and 6, different
methods of covering the laser diodes 20 with a transparent mold
compound (e.g. resin) may be applicable.
[0035] In the example of FIGS. 5 and 6, the laser diodes 20 have
anode and cathode on the same side of the semiconductor die. The
examples of FIGS. 7 and 8 illustrate exemplary systems-in-package
(SiP) approaches for forming a laser diode module, in which the
driver IC 4 is mounted on a lead frame 11 and one or more laser
diodes 20 are attached (e.g. soldered) on the driver IC 4 using a
chip-on-chip mounting technique, whereas the capacitors 30a, 30b
are mounted (e.g. soldered) on the lead frame 11 adjacent to driver
IC 4 without the need for bond wires.
[0036] FIG. 7A is a top view of a first example, in which the laser
diode 20 has anode and cathode on opposing sides of the
semiconductor die. One side of the laser diode die (anode or
cathode) is attached (e.g. soldered) to the corresponding chip
interconnection pad of the driver IC 4 (similar to chip
interconnections 42 in the previous examples) using a chip-on-chip
mounting technique, whereas the other side of the laser diode die
is connected via a bond wire 12''. Bond wires 12 are used as
electrical connections between supply terminal and driver IC 4 as
well as control terminal and driver IC 4. FIG. 7B illustrates a
side view corresponding to the top view of FIG. 7A. FIG. 8
illustrates an exemplary alternative to the example of FIGS. 7A and
7B. Accordingly, the bond wire 12'' is replaced by a clip 12''',
which may result in a lower effective inductance L.sub.EFF. Apart
from the clip 12'' the example of FIG. 8 is the same as the
previous example of FIGS. 7A and 7B. The semiconductor dies
including the driver IC 4, the laser diode(s) 20 and the
capacitor(s) 30 may be encapsulated with a (at least partly)
transparent resin (mold compound), which allows emission of the
laser light while protecting the laser diode.
[0037] The example of FIGS. 9A, 9B and 9C illustrate another SiP
laser diode module similar to the previous example of FIGS. 7A and
7B. FIG. 9A is a top view and FIG. 9B a corresponding side view.
Accordingly, the capacitors 30a, 30b are mounted (e.g. soldered) on
lead frame 11 without the need for any bond wires. Similarly, the
driver IC 4 is also mounted to the lead frame 11, wherein also no
bond wires are needed in the present example; flip-chip mounting
technique or ball-grid-array (BGA) technique may be used. Driver IC
and capacitors 30 are encapsulated using a resin or any suitable
mold compound material, which does not need to be transparent.
Outside this encapsulation 15 the packaged laser diode is mounted
on the lead frame 11. To provide a low-inductance connection
between the driver IC 4 and the laser diode package 20', the laser
diode die 20 is attached in a metal cap 201 with its top side and
to the lead frame 11 with its bottom side. FIG. 9C illustrates the
laser diode package 20' in more detail. The package used for the
laser diode 20 is substantially the same as the so-called
DirectFET.RTM. package known for MOSFET devices. A small opening
has to be provided in the package to allow emission of laser light.
As an alternative to the DirectFET package, a simple clip
connecting the top electrode of the laser diode 20 to the lead
frame 11 may be used (similar to clip 12''' shown in FIG. 8).
Finally, the laser diode may be covered with transparent material
(e.g. resin, mold compound).
[0038] The examples of FIGS. 10, 11, and 12 illustrate further
examples of SiP laser diode modules, in which the semiconductor
dies including driver IC 4, the laser diode(s) 20, the capacitor(s)
30 and (optionally) further devices are embedded in a (e.g.
multilayer) circuit board 5. According to the depicted example, the
module includes at least three semiconductor dies, wherein a first
semiconductor die includes at least one electronic switch 40 and
respective driver circuitry (driver IC 4), a second semiconductor
die includes at least one laser diode 20, and a third semiconductor
die includes at least one buffer capacitor 30. It is understood
that the capacitor is not necessarily a silicon capacitor (trench
capacitor, see FIG. 4); in the present examples other types of
capacitors such as ceramic capacitors may be used instead. In the
example of FIG. 10, the semiconductor die forming the driver IC 4
has all contact pads (particularly the pads forming drain and
source electrodes) on the same side so that the driver IC 4 may be
attached to corresponding metal pads in the metallization layer 52
of the circuit board 5. The drain potential is guided through the
circuit board 5 down to the layer 51 using via 54 as shown in FIG.
10.
[0039] In the example of FIG. 11, the semiconductor die forming the
driver IC 4 has the drain contact of the MOSFET included in the
semiconductor die on its top side and the other contacts
(particularly the source contact) on its bottom side. Thus, drain
and source of the MOSFET are connected to metal pads in the
metallization layer 52 and the further metallization layer 53. The
drain potential is guided through the circuit board 5 down to the
layer 51 using via 54' as shown in FIG. 11. In both, the examples
of FIGS. 10 and 11, the semiconductor die including capacitor(s) 30
(or, alternatively, e.g. a ceramic capacitor) is attached to metal
pads in the metallization layer 51 subjacent to the layer 52. The
laser diode is connected between a metal pad (attached to cathode
of the laser diode 20) in layer 51 and another metal pad (attached
to anode of the laser diode 20) in layer 52. A via 55 may bridge
the vertical distance between the surface of the laser diode die 20
and layer 52. Via 56 guides the control terminal of the driver IC
down to layer 51.
[0040] In the example of FIG. 11 a fourth semiconductor chip 6
including a micro-scanning mirror 6 (microscanner) is embedded in
the circuit board 5 as well as a respective scanner driver IC 61.
The micro-scanning mirror 6 is aligned with the laser diode to
receive and redirect the laser light emitted from the laser diode
20. Generally, the material used for embedding the bare
semiconductor dies may be any known material used to manufacture
circuit boards. The process of embedding bare dies in a circuit
board is as such known and thus not further discussed here. The
embedding of the base dies in the circuit board also allows for a
reduction of the effective inductance in the load current path
carrying the load current of the laser diode 20.
[0041] FIG. 12 illustrates a further example of a SiP laser diode
module, wherein the driver IC 4 and the capacitor(s) 30 are
embedded in a circuit board and the laser diode 20 is flip-chip
mounded on the surface of the circuit board. Both, the driver IC 4
and the capacitor are embedded between two metallization layers of
the circuit board 5. Solder balls 51 may be attached to the bottom
surface of the circuit board 5 to allow soldering the circuit board
onto another circuit board or a similar carrier board. Thus, the
circuit board 5 of FIG. 12 may also be referred to as package-like
PCB. One difference between the previous examples of FIGS. 10 and
11 and the present example of FIG. 14 is the different arrangement
order of the three circuit elements driver IC 4, capacitor 30 and
laser diode 20. As shown in FIG. 13, the laser diode is arranged in
another level of the Circuit board 5 as the capacitor 30, whereas
these elements are arranged in the same level in the previous
examples.
[0042] FIGS. 13A and 13B illustrate another example of a SiP laser
diode module. In this example, the driver IC 4 and the capacitor(s)
30 are included in an enhanced wafer level ball-grid array (eWLB)
package. The laser diode (bare die) may be either soldered onto
solder balls 54 at the bottom side of the eWLB package or to
dedicated solder pads 55 on the top side of the eWLB package.
[0043] Although the invention has been illustrated and described
with respect to one or more implementations, alterations and/or
modifications may be made to the illustrated examples without
departing from the spirit and scope of the appended claims. In
particular regard to the various functions performed by the above
described components or structures (units, assemblies, devices,
circuits, systems, etc.), the terms (including a reference to a
"means") used to describe such components are intended to
correspond--unless otherwise indicated--to any component or
structure, which performs the specified function of the described
component (e.g., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure, which performs
the function in the herein illustrated exemplary implementations of
the invention. For example, in any embodiment the capacitor may be
integrated in the same semiconductor die as the laser diode driver
IC 4 instead of attaching the capacitor onto the driver IC 4.
[0044] In addition, while a particular feature of the invention may
have been disclosed with respect to only one of several
implementations, such feature may be combined with one or more
other features of the other implementations as may be desired and
advantageous for any given or particular application. Furthermore,
to the extent that the terms "including", "includes", "having",
"has", "with", or variants thereof are used in either the detailed
description and the claims, such terms are intended to be inclusive
in a manner similar to the term "comprising".
EXAMPLES
Example 1
[0045] A laser diode module comprising: a first semiconductor die
including at least one electronic switch; and a second
semiconductor die including at least one laser diode, wherein the
second semiconductor die is bonded on the first semiconductor die
using a chip-on-chip connecting technology to provide electrical
connection between the electronic switch, the laser diode.
Example 2
[0046] The laser diode module of example 1, further comprising: a
third semiconductor die including at least one buffer capacitor;
the third semiconductor die being bonded on the first semiconductor
die using a chip-on-chip connecting technology.
Example 3
[0047] The laser diode module of examples 1 or 2, wherein the first
semiconductor die further includes at least one driver circuit
coupled to the electronic switch and configured to drive the
electronic switch on and off.
Example 4
[0048] The laser diode module of any of examples 1 to 3, wherein
the second semiconductor die has two electrodes on the same side
and is flip-chip mounted on the first semiconductor die.
Example 5
[0049] The laser diode module of example 2, wherein the third
semiconductor die has two electrodes on the same side and is
flip-chip mounted on the first semiconductor die.
Example 6
[0050] The laser diode module of any of examples 1 to 5, wherein
the second semiconductor die has a first electrode on a top side
and a second electrode on a bottom side of the second semiconductor
die, the second electrode being bonded to the first semiconductor
die using chip-on-chip connecting technology and the first
electrode being connected to the first semiconductor die using a
clip or a bond wire.
Example 7
[0051] The laser diode module of any of examples 1 to 6, wherein
the electronic switch and the laser diode are connected in series
between a supply terminal and a ground terminal.
Example 8
[0052] The laser diode module of example 2, wherein the electronic
switch and the laser diode are connected in series between a supply
terminal and a ground terminal, and wherein the buffer capacitor is
connected between a supply terminal and a ground terminal.
Example 9
[0053] The laser diode module of any of examples 1 to 8, wherein
the first semiconductor die includes at least one buffer
capacitor.
Example 10
[0054] The laser diode module of any of examples 1 to 9, further
comprising a lead frame, on which the first semiconductor die is
attached.
Example 11
[0055] The laser diode module of example 10, wherein the first
semiconductor die is flip-chip mounted on the lead frame without
using bond wires.
Example 12
[0056] The laser diode module of example 10 or 11, further
comprising at least one capacitor attached on the lead-frame.
Example 13
[0057] A laser diode module comprising a lead frame; a first
semiconductor die including at least one electronic switch and
attached to the lead-frame; at least one capacitor attached to the
lead frame; and a second semiconductor die including at least one
laser diode; the second semiconductor die being arranged between
the lead frame and a metal cap or a metal clip, so that a bottom
side of the second semiconductor die contacts the lead frame and a
top side of the second semiconductor die contacts the clip or the
metal cap.
Example 14
[0058] The laser diode module of example 13, wherein the first
semiconductor die is flip-chip mounted on the lead frame without
using bond wires.
Example 15
[0059] The laser diode module of examples 13 or 14, wherein the at
least one capacitor is surface mounted on the lead frame without
using bond wires.
Example 16
[0060] A laser diode module comprising a first semiconductor die
including at least one electronic switch; a second semiconductor
die including at least one laser diode; and a third semiconductor
die including at least one buffer capacitor, wherein the first and
the third semiconductor die are embedded in one chip package and
the second semiconductor die is a bare die bonded to a surface of
the chip package.
Example 17
[0061] The laser diode module of example 16, wherein the chip
package is an enhanced wafer level ball grid array (eWLB)
package.
Example 18
[0062] The laser diode module of example 16 or 17, wherein the
second semiconductor is soldered solder pads arranged either on the
top side or the bottom side of the chip package.
Example 19
[0063] The laser diode module of any of examples 16 to 18, wherein
the electronic switch and the laser diode are connected in series
between a supply terminal and a ground terminal, and wherein the
buffer capacitor is connected between a supply terminal and a
ground terminal.
Example 20
[0064] A laser diode module comprising: a first semiconductor die
including at least one electronic switch; and a second
semiconductor die including at least one laser diode, wherein the
first semiconductor die and the second semiconductor die are bare
dies embedded in a circuit board.
Example 21
[0065] The laser diode module of example 20 further comprising a
third semiconductor die including at least one buffer capacitor,
the third semiconductor die being embedded in the circuit
board.
Example 22
[0066] The laser diode module of example 20 or 21, wherein a buffer
capacitor is included in the first semiconductor die.
Example 23
[0067] The laser diode module of example 22, wherein the buffer
capacitor is configured to buffer a supply voltage.
Example 24
[0068] The laser diode module of any of examples 20 to 23, further
comprising a fourth semiconductor chip including a micro-scanning
mirror.
Example 25
[0069] The laser diode module of any of examples 20 to 24, wherein
the electronic switch and the laser diode are connected in series
between a supply terminal and a ground terminal.
Example 26
[0070] The laser diode module of example 21 or 22, wherein the
electronic switch and the laser diode are connected in series
between a supply terminal and a ground terminal, and wherein the
buffer capacitor is connected between a supply terminal and a
ground terminal.
Example 27
[0071] The laser diode module of example 21, wherein the third
semiconductor die is arranged on a first metallization layer of the
circuit board.
Example 28
[0072] The laser diode module of any of examples 20 to 27, wherein
the second semiconductor die is arranged between a first
metallization layer and a second metallization layer of the circuit
board.
Example 29
[0073] The laser diode module of example 28, wherein the first
semiconductor die is arranged between the second metallization
layer and a third metallization layer of the circuit board.
Example 30
[0074] A laser diode module comprising a first semiconductor die
including at least one electronic switch; and a second
semiconductor die including at least one laser diode, wherein the
first semiconductor die is a bare die embedded in an intermediate
level of a circuit board, and wherein the second semiconductor die
is arranged in a top or a bottom level of the circuit board.
Example 31
[0075] The laser diode module of example 30, further comprising at
least one buffer capacitor embedded in an intermediate level of a
circuit board.
* * * * *