The present invention relates to an information processing devices
in which a synapse strength matrix (Tij) representing inter-neuron wiring in neural
information processing can be written by rays of light from light-emitting elements
formed in the device.
Fig. 1 is a diagram showing an integrated circuit in an information
processing device simulating a neural circuit network which is shown, for example,
on page 625 of "Science", 233, by J.J. Hopfield et al (1986). In the drawing,
the reference numeral 1 indicates a unit of neurons each of which includes a resistor
2, a capacitor 3 and an amplifier 4. The reference numeral 5 indicates a Tij indicative
of a level of interaction between neurons. The reference numerals 6 and 7 respectively,
indicate an input line connected to the neuron 1 and an output line extending
The operation of this integrated circuit will now be described. Information
carried by an external signal is supplied, as an input to the processing device,
to the neuron 1 in the form, for example, of electric current, through the input
line 6. The input line 6 crosses the output line 7 of another neuron at the Tij
portions 5 before the input line 6 reaches the neuron 1, the current input to
the neuron 1 is affected by the output line 7. The Tij portions 5 generally consist
of a fixed resistor formed within the information processing device when that device
is manufactured. In the neuron 1, the resistor 2 and the capacitor 3 convert the
input current value to a voltage value, which is amplified by the amplifier 4,
whereby an output of firing (+V) or suppression (-V) is emitted. When the respective
outputs of the neurons of the entire network have attained stability, optimum target
information is obtained among these output values.
A conventional information processing device being constructed such
as described above, neurons, wiring lines and Tij portions have to be previously
formed in the device. As a result, the number of neurons that can be integrated
in the device is limited. In addition, the value of Tij portions cannot be changed.
Document OPTIC LETTERS, vol. 14, no. 16, 15 August 1989, WASHINGTON,
US, pages 844 - 846, OHTA 'GaAs / AlGa As optical synaptic interconnection device
for neural networks' discloses a device for coupling neurons via a light emitting
element and a photo electrical element. In D1 the output signal of one neuron generates
light which in turn is received by the photo electrical element connected to the
input wiring of another neuron, i.e. an opto-opto-coupling device. The coupling
strength is modified by an intermediate layer between the light emitting and the
photoelectric element, e.g. by its thickness, transparency, etc.
The present invention has been made with a view to solving the above
problems. It is accordingly an object of the invention to provide an information
processing device which is capable of enhancing the degree of integration of neurons
and to allow Tij values to be rewritten with ease.
The invention relates to information processing devices as set out
in independent claims 1 and 4.
In accordance with an embodiment of the invention, there is provided
an information processing device comprising a semiconductor integrated circuit
section simulating a neuronic function of a neural network; a photoelectric section
including a heterozygous molecular film having a photoelectric function and placed
between electrodes; and a light emitting section, both photoelectric and light
emitting sections being provided on the integrated curcuit section; wherein Tij
signals from the light emitting section can be written in the photoelectric section.
In accordance with another embodiment of the invention, there is
provided an information processing device in which the photoelectric section and
the light emitting section are formed in a multilayer structure on the semiconductor
integrated circuit section in which neuronic circuit regions are arranged in matrix.
According to the device of the present invention, Tij portions coupling
the neuronic circuit regions to each other comprise a photoelectric heterogeneous
molecular film provided on the semiconductor circuit section in which neural circuit
regions are provided, and electrodes formed on both sides of the molecular film.
Coupling strength between the neurons is input by means of light from a matrix-like
light-emitting device which comprises electrodes and a light-emitting heterozygous
molecular film placed therebetween. This structure allows the coupling between
the neurons to be changed. Further, in accordance with the device of the invention,
the photoelectric section and the light emitting section both comprising electrodes
and a heterogeneous molecular film placed therebetween may be built three-dimensionally
on the semiconductor integrated circuit section, whereby the number of neurons
that can be integrated per unit area can be increased substantially.
Further, in the device of the present invention, the photoelectric
section may be built in a multilayer structure on the semiconductor integrated
circuit in which the neuronic circuit regions are arranged in matrix, whereby the
number of wiring lines for forming the Tij couplings can be reduced, thereby making
it possible to increase the number of neurons that can be integrated.
- Fig. 1 is a circuit diagram showing a conventional information processing device;
- Figs. 2(a) and 2(b) are diagrams showing a plan view of a Tij matrix wiring
pattern in an information processing device in accordance with an embodiment of
the device of the present invention and a partial sectional view of the same;
- Figs. 3(a) to 3(c) are diagrams showing a plan view of a neuron connecting
pattern in an information processing device in accordance with another embodiment
of the device of the present invention and partial sectional views of the same;
- Fig. 4 is a chart showing a voltage-current characteristic of a molecular film
obtained by heterogeneous accumulation.
An embodiment of the present invention will now be described with
reference to the accompanying drawings.
Fig. 2(a) is a wiring diagram showing the construction of an information
processing device in accordance with an embodiment of this invention and Fig. 2(b)
is a sectional view taken along the line A-A' of Fig. 2(a). The device shown includes
neurons 11, a molecular film 12 having a photoelectric function, input wiring lines
13, output wiring lines 14, synaptic junction sections 16, a silicon substrate
17, an insulating film 18, electrodes 31 for light-emitting elements, a molecular
film 32 having a light emitting function, a transparent electrode 33 for the light-emitting
elements, a transparent insulating layer 34, and lead wires 35 for the electrodes
A method of producing the device of this embodiment will be described
The neurons 11 which are formed as analog or digital circuits so
as to simulate a neuronic operation of a living body are arranged in columns in
the silicon substrate 17 using integrated circuit technologies. Then, the input
wiring lines 13 are formed on one surface of the integrated circuit by vacuum
evaporation of aluminum. The other surface of the integrated circuit (where no
input wiring lines 13 are formed) are covered by an insulating film, such as an
SiO2 film 18, thus leveling the surface of the integrated circuit.
On this wafer on which the integrated circuit and the wiring lines have been formed,
several layers of porphyrin derivative are deposited by the Langmuir-Blodgett
method and, then, several layers of flavin derivative are deposited thereon, thereby
forming the heterogeneous molecular film 12.
This molecular film 12 has a property of changing a current flowing
between the electrodes in accordance with the intensity of light impinging thereto.
Then, the output wiring lines 14 are formed on the molecular film
12 by vacuum evaporation of aluminum, ITO, SnO2, etc. such that they
overlap the Tij portions 16. In this process, the Tij portions 16 should be transparent
so as to allow light to be transmitted to the molecular films.
Subsequently, the transparent insulating layer 34 is formed on the
molecular film 12 and the output wiring lines 14 by using SiO2, a high
molecular substance, etc., and, on this layer 34, the transparent electrode 33
is formed of such material as ITO, SnO2 and aluminum.
Then, an amine-type material, such as TPD [N, N'-diphenyl-N, N'-(3-methyl
phenyl)-1, 1'-byphenyl-4, 4'-diamine], is deposited as a hole transporting film
on the transparent electrode 33 by the cluster ion beam (ICB) method and, then,
an emitter material such as anthracene is deposited on this hole transporting film
by the ICB method, and, on this emitter material layer, a perylene tetracarboxylic
acid derivative is deposited as an electron transporting film by the ICB method,
thus forming the molecular film 32 having a light emitting function.
Finally, formed on the electron transporting film are Mg electrodes
which serve as the electrodes 31. The wiring leads 35 are formed by vacuum evaporation
of a metal such as aluminum and are connected to the Mg electrodes.
Next, the operation of the above device will be described. In a neural
network, a signal input to a neuron is coupled to a signal output from another
neuron before the input signal is supplied to that neuron. Such a coupling affects
an input condition for the neuron to which the input signal is supplied. However,
it does not follow that the outputs of all the neurons affect one neuron. By determining
the manner in which the output of a neuron affects an input to another neuron in
accordance with the information to be processed, the input information can be
processed at high speed and with high efficiency. This embodiment utilizes the
photoconductivity of the molecular film 12 and the light emitting function of the
molecular film 32. That is, light signals from the molecular film 32 are received
by the molecular film 12, and the Tij portions 16 transmit signal output from the
neurons 11 based on a change in conductivity of the molecular film 12. In other
words, since the output wiring lines 14 on the molecular film 12 and the input
wiring lines 13 therebelow are inter-connected, by applying a light pattern on
the molecular film 32 to the Tij portions 16 as a matrix signal, a high efficiency
information processing as mentioned above can be realized. Further, in the Tij
portions 16, currents flowing between the input wiring lines 13 and the output
wiring lines 14 can be controlled in accordance with the intensity of light. That
is, the resistance in the Tij portions 16 can be changed according to the intensity
of light, so that, in addition to an ON/OFF digital pattern formed by the matrix
section 32, changes in voltage applied between the electrodes 31 and 33 can be
utilized as optical signals to be supplied to the Tij portions 16, thereby making
it possible to realize an information processing which is still more efficient
than in the case where binary Tij values are used. Further, since a Tij pattern
is prepared by optical writing as described above, the rewriting of Tij pattern
can be achieved, thus making it possible to realize an information processing
of a higher level than in the case where a Tij pattern is fixed.
By changing a Tij pattern and Tij resistance in accordance with output
signals, it is also possible to impart a learning function to information processing.
Fig. 3(a) is a wiring diagrams showing an information processing
device in accordance with another embodiment of the present invention, and Figs.
3(b) and 3(c) are sectional views taken along the lines A-A' and B-B' of Fig. 3(a).
In the drawings, the components which are identical with or equivalent to those
of Figs. 2(a) and 2(b) are referred to by the same reference numerals and a description
of such components is omitted here. The device shown includes output electrodes
20, input electrodes 21, and wiring lines 22 and 23 on the first layer of molecular
film 12. The wiring lines 22 are positioned above the output electrodes 20, and
the wiring lines 23 are positioned above the input electrodes 21. The reference
numerals 24 and 24' indicate wiring lines on the second layer of molecular film
12'; the reference numerals 25 through 28 indicate positions to be irradiated
with light; and 29 indicates a neuron spaced away from the neuron 11.
Next, a method of producing the device of this embodiment will be
Neurons 11 and 29 which consist of analog or digital circuits formed
so as to simulate a neural operation in a living body, are arranged in matrix form
on one surface of a silicon substrate 17 by the integrated circuit technique.
Then, by vacuum evaporation of a metal such as aluminum, the input and output electrodes
20 and 21 of the neurons are formed on the integrated circuit. The remaining portions
of the surface of the integrated circuit where no electrodes are formed are covered
with an insulating film such as the SiO2 film 18, thereby leveling the
circuit surface. On this wafer thus formed, the first layer of molecular film
12 having heterojunction is formed by the Langmuir-Blodgett method in the same
manner as in the embodiment shown in Figs. 2(a) and 2(b). Semitransparent aluminum
wiring lines 22 and 23 are formed on this first layer of molecular film 12 such
as to respectively extend just above the output electrodes 20 and the input electrodes
21 of the neurons 11 aligned in lateral rows. Afterwards, the second layer of
molecular film 12' is formed in the same manner as the first layer of molecular
film 12. Then, semiconductor aluminum electrodes 24 and 24' are formed, two for
each neuron, on the second layer of molecular film 12' such as to extend above
the neurons 11 aligned in longitudinal rows but not to overlap the output and
input electrodes 20 and 21 of these neurons. The elements of the light-emitting
sections 31 through 35 are formed in the same manner as in the case of the device
shown in Figs. 2(a) and 2(b).
Next, the operation of the above device will be described. For example,
the output of the neuron 11 in the upper left corner and the input of the neuron
29 in the right bottom corner of Fig. 3(a) are interconnected in the following
manner. A plurality of rays of light irradiate those sections of the device shown
in Fig. 3(a) where neuron electrodes and wiring lines cross each other. When, for
example, an intersection point 25 of the output electrode 20 of the upper left
neuron 11 and one of the wiring lines 22 formed on the first layer of molecular
film 12, this output electrode 20 and this wiring line 22 are electrically interconnected,
thus transferring an electrical signal on the output electrode 20 to the wiring
line 22. Then, when an intersection point 26 of the wiring line 22 and one of the
wiring lines 24 formed on the second layer of molecular film 12' is irradiated
with light, the above wiring line 22 and this wiring line 24 are electrically interconnected,
thus transferring the electrical signal on the output electrode 20 of the neuron
11 to the wiring line 24. When an intersection point 27 of the wiring line 24 and
the wiring line 23 which is on the first film layer of molecular 12 and extends
above the input electrode 21 of the neuron 29 is irradiated with light, the wiring
line 24 and this wiring line 23 are electrically interconnected, thereby transferring
the electrical signal from the output electrode 20 of the neuron 11 to this wiring
line 23. Finally, when an intersection point 28 of the wiring line 23 and the input
electrode 21 of the neuron 29 is irradiated with light, the wiring line 23 and
this input electrode 21 are electrically interconnected, thus allowing the electrical
signal from the output electrode 20 of the neuron 11 to be transferred to the
input electrode 21 of the neuron 29.
Thus, by simultaneously irradiating the four points of intersection
25, 26, 27 and 28 with light, the output of the neuron 11 can be coupled to the
input of the neuron 29. Such a coupling relationship can be applied to other neurons,
thus making it possible to express all the input/output couplings between the neurons.
Fig. 4 is a characteristic chart showing an example of the photoconductivity
of the molecular film 12 and 12'.
Thus, an information processing device of this invention comprises
a semiconductor integrated circuit section simulating a neural function of a neural
network, and a molecular film device provided on the integrated circuit section
and having a photoelectric function, Tij portions of a plurality of neural circuit
regions provided on the integrated circuit section being written by light. Due
to this construction, the writing of the Tij matrix can be performed arbitrarily,
and the number of wiring lines can be reduced. Accordingly, an information processing
device can be obtained which performs information processing with high efficiency
and provides a high level of integration of neurons.