JPH0191478A - Optical connection circuit - Google Patents

Abstract

PURPOSE:To reduce skew of clock signal, and realize small size and low cost, by providing a semiconductor photoelectronic integrated circuit with a light emitting device generating light clock, and a photo detector receiving the light clock signal, and forming a light scattering body on the rear of a package. CONSTITUTION:On a photoelectronic integrated circuit, the follow are integrated; a light emitting device 12 generating light clock signal, a plurality of photo detectors 13 receiving the light clock signal, and a light scattering body 16 which is formed on the surface facing a semiconductor substrate 11 inside a package 15 of the photoelectronic integrated circuit, and scatters the clock signal generated from the light emitting device 12 to make the photo detector 13 detect the scattered light. The clock signal is radiated from the light emitting device 12 formed on the semiconductor substrate 11, and scattered by the light scattering body 16 formed inside the package 15. The clock signal of the scattered light is detected by the plurality of photo detectors 13 formed on the semiconductor substrate 11, and the detected clock signal is delivered to electronic circuits on the semiconductor substrate 11. Thereby reducing the skew of clock signal, and obtaining a small-sized package of low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical connection circuit for clock signals in an optoelectronic integrated circuit in which a function of transmitting signals by light is added to a semiconductor substrate on which electronic circuits are integrated. It is.

[Conventional technology]

As the density of silicon integrated circuits continues to increase, large-scale semiconductor memories such as 1 mega DRAMs and large-scale semiconductor logics such as 32-bit processors are now commercially available. In order to move these elements at higher speeds, each element must be driven by a synchronized, faster clock signal.

If there is a skew (time difference) in the clock signals of each element, the operations of each element will not be synchronized and high-speed operation will not be possible.

[Problem that the invention seeks to solve]

Normally, in order to prevent this problem, each element is laid out so that the line lengths of the clock signal 6 are as equal as possible. For this reason, there are restrictions on the layout of the element,
This made the design difficult.

Even with this layout, clock skew cannot be completely resolved. In such a case, synchronization was achieved by latching the clock signal and delaying it by one time loft. Therefore, there was a problem that the processing speed was reduced.

As a way to solve this problem, B.D.Climber and J.W.
mer and J.W. Goodman) in the publication ``Optical Engineering, vol. 25, 1986.
, 25+ 1986) J, p. 1103, proposed the concept of an optical connection circuit shown in FIG.

This proposal is not an actual prototype, but merely a proposed concept. This concept will be explained below. A semiconductor laser 22 is provided outside the VLSI, and a clock signal generated by light emitted by the semiconductor laser 22 is branched and irradiated onto a photodetector 23 formed on a silicon semiconductor substrate 21 using a hologram 26 .

Position information of the photodetector 23 on the silicon semiconductor substrate is written on the hologram in advance so that the photodetector 23 is efficiently irradiated with an optical clock signal.

However, in this optical connection circuit, it is necessary to maintain a distance of 1 cm or more between the hologram 26 and the semiconductor substrate 21, which poses a major constraint on miniaturization of the element package. Also,
The shape of the hologram is different for each type of VLSI.
It had to be rebuilt, which was an obstacle to making VLSI at a low price.

As mentioned above, when connecting VLSI clock signals using electricity, which has traditionally been done, the problem of skew occurs, and when using optical connections using light, the miniaturization and cost reduction of devices are obstacles. Ta.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical connection circuit that can reduce the skew of a VLSI clock signal, reduce the size of a VLSI package, and form a low-cost VLSI package.

[Means for solving problems]

The present invention provides an optical connection circuit for a clock signal of an optoelectronic integrated circuit in which a function of transmitting a signal by light is added to a semiconductor substrate on which an electronic circuit is integrated. a light-emitting element for detecting an optical clock signal and a plurality of light-receiving elements for detecting an optical clock signal; It is characterized by having a light scattering body that is detected by the element.

[Effect]

In the present invention, a clock signal is emitted from a light emitting element formed on a semiconductor substrate, and is scattered by a light scattering body formed inside a package. The clock signal of this scattered light is detected by a plurality of light receiving elements formed on the semiconductor substrate. The sensed clock signal is distributed to electronic circuitry on the semiconductor substrate.

In this case, since the clock signals on the top of the semiconductor substrate are connected by light, the clock skew is small and does not pose a problem.

According to the scattering and reflection described above, it is possible to reduce the distance between the light scattering body and the light emitting element or the light receiving element to several millimeters or less, and the package does not become large. Furthermore, the light scattering body can be easily formed and can be produced at a very low cost since it does not require the use of expensive holograms.

〔Example〕

Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a perspective view for explaining one embodiment of the present invention, in which a ceramic package 15 shaped like a top lid of a VLSI is removed from a substrate 14 and rotated 90 degrees. A silicon semiconductor substrate 11 is formed on a substrate 14 of the package, a plurality of photodetectors 13 are provided on this semiconductor substrate 11, and a GaAs semiconductor laser 12 is provided approximately in the center of the semiconductor substrate 11. The semiconductor laser 12 used was a vertical emission type in which 45-degree reflecting mirrors were integrated so that laser light was emitted in a direction perpendicular to the silicon semiconductor substrate 11.

On the other hand, on the back side of the package 15, a scattering/reflecting surface 16 was formed by vapor-depositing metal on a ceramic having many surface irregularities. At this time, the distance between the scattering/reflecting surface 16 and the GaAs semiconductor laser 12 is not particularly limited, and can be made as close as several millimeters or less.

In the optical connection circuit configured as described above, the electrical signal that drives the laser 12 is the clock signal of this VLSI. An optical clock signal with a wavelength of 0.85 microns emitted from this laser is scattered by a scattering/reflection surface 16 formed on the back side of a ceramic package 15 shaped like an upper lid. The scattered optical clock signal returns onto the silicon semiconductor substrate 11, is detected by the photodetector 13, and is converted back into an electrical clock signal. Since the scattered light propagates approximately the same distance on average and reaches the photodetector, there is almost no skew between the optical clock signals received by each photodetector.

In the above embodiments, a ceramic surface with metal vapor deposited thereon was used as the scattering/reflection surface, but a scattering/reflection surface formed by roughening the surface of a metal plate may also be used. These scattering/reflecting surfaces can be manufactured much more easily and at lower cost than holograms.

In the above embodiment, a vertical emission type semiconductor laser with integrated 45-degree reflecting mirrors was used, but a vertical emission type semiconductor laser using higher-order diffracted light from a grating may also be used, and a solid-state semiconductor laser that oscillates in the stacking direction A laser may also be used.

Further, in the above embodiments, a silicon semiconductor was used as the semiconductor substrate, but similar effects can be obtained with compound halves such as GaAs or ■nP.

Furthermore, although the shapes of each element and package in the above embodiments were selected as described above, it is clear that the present invention is not limited thereto.

〔Effect of the invention〕

As explained above, according to the present invention, a semi-oligoelectronic integrated circuit is provided with a light emitting element that generates an optical clock signal and a light receiving element that receives the optical clock signal, and a light scattering body is formed on the back surface of the puff cage. By doing so, it is possible to obtain an optical connection circuit which has a small skew of a clock signal, which has been a problem in the past, and which enables a small and low-cost VLSI.

[Brief explanation of the drawing]

FIG. 1 is a perspective view illustrating an embodiment of the present invention, and FIG. 2 is a perspective view illustrating a conventional optical connection circuit. 11... Silicon semiconductor substrate 12... GaAs laser 13... Photodetector 14... Package substrate 15... Ceramic package 16... Scattering Reflective surface 21...Silicon half body substrate 22...Semiconductor laser 23...Photodetector 26...Hologram agent Patent attorney Yoshiyuki Iwasa Figure 1

Claims (1)

[Claims] (1) In an optical connection circuit for a clock signal of an optoelectronic integrated circuit in which a function of transmitting a signal by light is added to a semiconductor substrate on which an electronic circuit is integrated, the optical clock signal integrated in the optoelectronic integrated circuit is emitted. a light-emitting element and a plurality of light-receiving elements for detecting optical clock signals; 1. An optical connection circuit comprising: a light scattering body that is detected by a light scatterer;