JPH08293836A - Two-dimensional free space bidirectional optical connection device - Google Patents

Abstract

PURPOSE: To avoid electromagnetic dielectric noise owing to electric wiring and heat generation accompanying transmission delay and the increase in power consumption by preventing the installation of fixed electric wiring connecting signal terminal that respective LSIs have one to one in optical interconnection. CONSTITUTION: A polyimide thin film is formed on an Si substrate, and a core thin film becoming the slab-type waveguide of a single mode is set by polyimide varnish. A hologram 7 is formed on the uppermost layer (clad) of the generated slab waveguide by anisotropic dry etching which is mainly composed of photolithography and O2 , and the waveguide is connected to light-emitting/receiving elements. An ITO transparent electrode is formed on the hologram 7. Organic EL is generated on the electrode. An upper electrode consisting of Ca is formed on the electrode, and an electrode 14 and a semiconductor layer 11 are made into a pattern by photolithography and RIE. The element is subjected to bias in a forward direction and it is made into the light-emitting element. Plural LSI chips (a clock control element, a memory, an arithmetic processor or the like) are arranged on the module substrate, and the whole are sealed by resin materials.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to LSI chips, LS
The present invention relates to a two-dimensional free space bidirectional optical connection device for connecting modules mounted with a large number of I or boards.

[0002]

2. Description of the Related Art A large number of highly integrated LSI chips are used in computers that support an advanced information society, and high-speed and high-density signal transmission is required between these chips, boards, or computers. ing. Until now, the leading role has been implemented by mounting technology using electrical wiring. However, mounting technology using electric wiring is approaching its limit because it faces problems such as transmission delay and mutual interference noise due to increase in wiring capacity due to higher speed and higher density, or increase in heat generation of the device. Attempts to solve these problems by optical transmission have already been reported. In other words, some interconnections with a high degree of freedom have been proposed that take advantage of the non-inductive property and multiplicity of light.

In the light emitting / receiving element which plays a central role in this system, a surface type light emitting / receiving device made of an inorganic semiconductor, particularly a compound semiconductor mainly composed of GaAs or the like is widely used. One of the representatives is the literature (IEEE Journal of Quantum Elec
tronics, QE-24, p.1462 (1985) SEED) or NEC Technical Report, Vol. 46, No. 8, p63 (199
There is an optical transmitter / receiver element called VSTEP disclosed in 3). Although these elements realize low power consumption to some extent and small-scale multiplicity, they are essentially LSIs.
It is not suitable for integration with the silicon material that makes up the chip, and has not yet surpassed the high-speed, high-density performance that the current packaging technology has achieved.

On the other hand, the idea of so-called free space interconnection, which uses the free propagation of light while leaving the light source as a point, has been proposed. A typical example of this is the module substrate using the glass waveguide and holography disclosed in the literature (Applied Physics Letters, 64, p.2931 (1994)). I haven't.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide an LS
Suitable for integration with silicon elements that compose I
The purpose is to eliminate the so-called wiring bottleneck by highly flexible coupling utilizing time multiplexing.

[0006]

[Means for Solving the Problems]

(1) A slab waveguide made of an organic polymer formed on a flat substrate is used as a transmission medium.

(2) An optical input / output coupler having a wavelength selection function is arranged on the waveguiding layer, and a control element for controlling the wavelength to be selected is provided, and a control signal is distributed to each element by this mechanism. Thereby, the coupling state between the elements is arbitrarily controlled.

(3) An LED made of an organic semiconductor is arranged on the coupler, and a part of the LED is used as a light emitting element and the other is used as a light receiving element by reversing the applied voltage.

(4) An LSI chip or module is arranged on the above-mentioned waveguide substrate, and the light emitting / receiving element and the signal electrode of each chip (or module or board) are connected. It should be noted that on this substrate, electrical wiring necessary for driving the chip or module is additionally provided.

(5) Chip mounted on the same waveguide layer
(Or, a module or a board) is provided with an element for synchronization control, and a synchronization signal is distributed to each element by the mechanism described above.

(6) The periphery of the waveguide substrate is shielded by a resin material that absorbs signal light from each light emitting element and an optical noise signal from the outside. However, this does not apply to the part that performs input / output with the outside.

[0012]

(1) By using the slab type optical waveguide substrate, the same planar mounting technology as the conventional one can be used.

(2) Since there is no occupied electric wiring connecting terminals of an LSI or the like, the packaging density can be increased without being restricted by the electric wiring space. Further, by applying the function of arbitrarily changing the coupling to the time-multiplexing and wavelength-multiplexing methods, the packaging density can be further improved.

(3) Since optical transmission is performed even when high-density mounting is performed, problems of signal delay, inductive noise, and element heat generation can be avoided.

(4) By eliminating the bottleneck of the bus and transmission system from the above, not only the flexibility of LSI design is greatly expanded and the performance of a single element is improved, but also parallel computation using a more advanced network is performed. Through processing, the processing capacity of the entire system can be dramatically improved.

[0016]

Example A silicon substrate having excellent flatness was used as the substrate. A polyimide varnish was spread on the substrate by spin coating and heated to form a polyimide thin film. For the polyimide varnish, O manufactured by Hitachi Chemical Co., Ltd.
PI-2005 and OPI-1905 were used to form a clad and a core, respectively, and the core film thickness was set so as to form a single mode slab type waveguide.

A hologram is formed on the uppermost layer (clad) of the slab waveguide thus manufactured by photolithography and anisotropic dry etching (RIE) mainly composed of O ₂ , whereby the waveguide and the light receiving and emitting light are formed. Bonding with the device was performed.

An indium / tin-oxide (ITO) transparent electrode was formed on this hologram by vacuum evaporation. Subsequently, after forming a buffer layer with a polyimide film, the ITO transparent electrode was vacuum-deposited again to form an etalon (bandpass filter) element. The transmission center wavelength of this filter is the ITO of the lower layer due to the thermo-optic effect of the polymer.
It can be controlled by the value of current flowing through the electrodes. The response time of this tunable filter is limited to about 10 msec due to heat conduction, etc., but if a liquid crystal material or an electro-optical material is applied instead of the polymer layer, the response time is improved from 0.1 msec to 100 psec. It is possible.

In addition to this, reference (1994 Internetional Worksh
op on Electroluminescence, Digest of Technical Paper
s, p. 36), an organic electroluminescence device made of an organic semiconductor was prepared by vacuum vapor deposition. That is, poly [2-methoxy-5- (2'-ethylhexyloxy-1,4-phenylene) vinylene] (MEH-PPV) was used as the organic semiconductor material. An upper electrode made of Ca was formed thereon by vacuum vapor deposition, and the electrode and the semiconductor layer were patterned again to an appropriate size by photolithography and RIE. The element thus formed was biased in a pure direction to form a light emitting element, and the light receiving element was applied with a reverse bias to form a light transmitting / receiving element. The characteristics of this optical transmitter / receiver device were that the driving voltage for receiving light was about -10.0 V for receiving light, the quantum efficiency was about 20%, the driving voltage for emitting light was +2.0 V, and the quantum efficiency for emitting light was 1%.

A plurality of LSI chips (clock control element, memory, arithmetic processor, etc.) were arranged on this module substrate, and the whole was sealed with a resin material.

[0021]

The optical interconnection according to the present invention does not have a fixed electrical wiring that connects the signal terminals of each LSI in a one-to-one relationship. Therefore, many problems caused by high-density wiring, that is, electromagnetic induction noise, transmission delay,
It is possible to avoid heat generation and the like due to increased power consumption. In addition, since these connections can be changed arbitrarily, a more advanced network using time-multiplexing or frequency-multiplexing can be constructed, and a significant improvement in processing capacity can be expected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a two-dimensional free space bidirectional optical connection method in which a plurality of LSI chips are arranged.

FIG. 2 is a sectional view taken along the line AA ′ in FIG.

3 is a detailed cross-sectional view of the device in FIG.

[Explanation of symbols]

1 ... Substrate, 2 ... LSI board, 3 ... Signal light, 4 ... Input / output terminal, 5 ... Receiving element, 6 ... Transmitting element, 7 ... Hologram,
8 ... Insulating layer, 9 ... Polymer encapsulant, 10 ... N-type (p-type) organic semiconductor layer, 11 ... P-type (n-type) organic semiconductor layer, 12,
14 ... Electrode, 13 ... Refractive index variable layer.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takahiro Nakayama 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Atsushi Tsunoda 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Ltd. Hitachi Research Laboratory

Claims (6)

[Claims] 1. A method of performing bidirectional optical connection between any one-to-one, one-to-many or many-to-many of a plurality of integrated circuits, a light emitting element for converting an electrical signal into an optical signal, and a specific wavelength of the optical signal. A variable wavelength optical filter that transmits light, an optical coupler that couples an optical signal to a waveguide, a slab-type waveguide that propagates an optical signal, an optical coupler that extracts the propagated optical signal from the waveguide again, and is extracted. The optical filter having a variable wavelength that transmits a specific wavelength of the optical signal and the light receiving element that converts the optical signal into an electrical signal are used, and the synchronizing signal and the input / output signal are exchanged via these. Dimensional free space bidirectional optical connection device. 2. The two-dimensional free space bidirectional optical connection device according to claim 1, wherein the light emitting element for converting an electric signal into an optical signal is made of an organic semiconductor having a resonator structure. 3. The optical filter according to claim 1, wherein the wavelength of the optical filter transmitting a specific wavelength of the optical signal is variable, and the pair of reflecting mirrors and electrodes are provided on both sides of a material whose refractive index is variable by heat, electric field or magnetic field. Two-dimensional free space bidirectional optical connection device with scissors. 4. The optical coupler according to claim 1, wherein the optical coupler that couples an optical signal to a waveguide and the optical coupler that extracts the propagated optical signal to the outside of the waveguide are holograms or minute scatterers. Dimensional free space bidirectional optical connection device. 5. The two-dimensional free space bidirectional optical connection device according to claim 1, wherein the slab type waveguide for propagating an optical signal is composed of a multilayer film made of a polymer material. 6. The two-dimensional structure according to claim 1, wherein the light receiving element for converting an optical signal into an electric signal is also used by operating the light emitting element made of the organic semiconductor according to claim 2 by applying a reverse bias. Free space bidirectional optical connection device.