170
of semiconductor elements are made to run over a previously heated substrate using
an inert gas flow, usually argon. These molecules are formed by organic elements,
like hydrogen and carbon, which are bound to one of the atoms required for doping
(aluminium, gallium, indium, phosphor, and others) (Kitai 2011). This labourintensive process is based on the use of a carrier gas formed by a mixture of inert
molecules. The substrate should be hot enough to break molecules and afford the
deposition of the atoms of the semiconductor elements desired. The remaining
atoms of the mixture flow with the gas (Kitai 2011). The advantages of this technique include the possibility to control composition and to work with ternary and
quaternary semiconductors, which affords to obtain a wide variety of compositions.
Besides, the method allows changing composition during deposition by merely
altering the flow rate of molecules (Kitai 2011).
The LED production process starts with the manufacture of ingots (Fig. 9.8),
which are used to produce the substrate. The composition of the substrate may vary,
since various materials can be used, like silicon (Stasiak 2013). Yet, Stasiak (2013)
claims that most LEDs are built using sapphire (aluminium oxide, Al 2 O 3 ) as substrate. Another material used for this purpose is diamond (Stasiak 2013).
From these ingots, fine blades are cut (wafers), which are then transported to the
hoods where the deposition process is carried out (Fig. 9.9). After that, a metallic
layer is deposited, whose role is to conduct the current outside the semiconductor
using metallic terminals (Stasiak 2013).
Subsequently, the wafers are mechanically cut to small chips to high levels of
accuracy. These chips are then soldered on a metallic terminal. Extremely thin gold
filaments are used to establish the connections. After that, encapsulation is carried
out using optical materials (epoxy resin, silicone, or glass), through which light is
irradiated (Stasiak 2013).
Figure 9.10 shows a simplified flowchart of the LED production process.
According to Osram (2009), the production of LEDs may be divided into two
stages; the first is called frontend when the semiconductor chip is produced; the
second is called backend when contacts are connected and the chip is encapsulated.
In turn, Scholand and Dillon (2012) divided the process into three main steps: production of the substrate, production of the LED chip, and assembly and
encapsulation.
Fig. 9.8 Sapphire ingots.
(Source: Stasiak 2013)
E. C. A. dos Santos et al.
of semiconductor elements are made to run over a previously heated substrate using
an inert gas flow, usually argon. These molecules are formed by organic elements,
like hydrogen and carbon, which are bound to one of the atoms required for doping
(aluminium, gallium, indium, phosphor, and others) (Kitai 2011). This labourintensive process is based on the use of a carrier gas formed by a mixture of inert
molecules. The substrate should be hot enough to break molecules and afford the
deposition of the atoms of the semiconductor elements desired. The remaining
atoms of the mixture flow with the gas (Kitai 2011). The advantages of this technique include the possibility to control composition and to work with ternary and
quaternary semiconductors, which affords to obtain a wide variety of compositions.
Besides, the method allows changing composition during deposition by merely
altering the flow rate of molecules (Kitai 2011).
The LED production process starts with the manufacture of ingots (Fig. 9.8),
which are used to produce the substrate. The composition of the substrate may vary,
since various materials can be used, like silicon (Stasiak 2013). Yet, Stasiak (2013)
claims that most LEDs are built using sapphire (aluminium oxide, Al 2 O 3 ) as substrate. Another material used for this purpose is diamond (Stasiak 2013).
From these ingots, fine blades are cut (wafers), which are then transported to the
hoods where the deposition process is carried out (Fig. 9.9). After that, a metallic
layer is deposited, whose role is to conduct the current outside the semiconductor
using metallic terminals (Stasiak 2013).
Subsequently, the wafers are mechanically cut to small chips to high levels of
accuracy. These chips are then soldered on a metallic terminal. Extremely thin gold
filaments are used to establish the connections. After that, encapsulation is carried
out using optical materials (epoxy resin, silicone, or glass), through which light is
irradiated (Stasiak 2013).
Figure 9.10 shows a simplified flowchart of the LED production process.
According to Osram (2009), the production of LEDs may be divided into two
stages; the first is called frontend when the semiconductor chip is produced; the
second is called backend when contacts are connected and the chip is encapsulated.
In turn, Scholand and Dillon (2012) divided the process into three main steps: production of the substrate, production of the LED chip, and assembly and
encapsulation.
Fig. 9.8 Sapphire ingots.
(Source: Stasiak 2013)
E. C. A. dos Santos et al.