JPS5975656A - Semiconductor integrated circuit structure - Google Patents

Abstract

PURPOSE:To shorten the time required for transmitting an information signal, or to reduce time delay by setting up an optical waveguide as an information signal transmitting path between unit circuits for an integrated circuit. CONSTITUTION:Regarding a transmission section E1, electric light converting light-emitting elements 4, such as a light-emitting diode, a semiconductor laser, etc. are set up on a substrate 1, and the active region or light-emitting section 6 for the elements is arranged so as to emit beams I into the optical waveguide 3. An electrode region 5 for driving the light-emitting elements 4 is formed in the surface of the substrate. On the other hand, light-receiving elements 10 as a reception section D1 are constituted so that a P-N junction is formed between a first region 7 formed to a section such as the surface section of the substrate and a second region 1a as a substrate 1 section around the first region, and a potential change generated in the first region 7 can be detected as an information signal when the first region 7 is connected to the predetermined electric signal input terminal of the unit circuit with the reception section. The optical waveguide 3 is constituted to a shape that it is bent down toward the substrate side in order to introduce beams toward the reception section.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a semiconductor integrated circuit structure having several unit circuits and requiring the transmission and reception of information signals between the unit circuits, and in particular to improvements in the structure of a semiconductor integrated circuit that has several unit circuits and is configured to require the transmission and reception of information signals between the unit circuits. This article relates to a semiconductor integrated circuit structure designed to increase speed.

Bipolar to MO8) Semiconductor integrated circuit in which multiple unit circuits (including cases with a single element) having constituent elements such as transistors are integrated on the same substrate, and information signals are exchanged between the unit circuits. However, in all conventional systems, information signals are transmitted by the flow of carriers or current.

That is, both the transmitting section and the receiving section are composed of transistors and the like as semiconductor electronic devices, and the transmission path between them is, as a matter of course, composed of a conductive material line made of metal or the like.

However, it is clear from past events that the improvement in agglomeration density will continue to progress even further in the future.
Therefore, as the unit circuits themselves and the components of each unit circuit become further miniaturized, the number of unit circuits mounted on a single board is expected to increase significantly and become more complex. Then, conversely, the length of wiring connecting unit circuits is expected to increase.0 Then, due to miniaturization, the time required for the υ unit circuit itself to process electrical signals will decrease. However, there is a good chance that the time delay required for an electrical signal to pass through a signal transmission line with a unit circuit amount will be longer than that, so it is highly likely that the overall performance of integrated circuits will be improved by miniaturizing the dimensions. is also inhibited.

The present invention has been made in consideration of this point, and is capable of reducing the time required for information signal transmission between unit circuits in a semiconductor integrated circuit structure in which a plurality of unit circuits are mounted on the same substrate. To put it simply, the present invention aims to provide a configuration that can minimize delays.Instead of the conventional method of transmitting electrical signals as they are, the present invention aims to first convert them into optical signals and then transmit them. ,In other words,
Although it is a semiconductor integrated circuit as a whole, the information signal transmission path between its unit circuits has an optical waveguide structure. The following findings and principles prove that this achieves the desired goal of increasing the signal transmission speed.

In semiconductor integrated circuits, signals are transmitted and received between unit circuits or unit systems using conventional methods in which electrical signals are used to connect these elements using wiring made of conductive materials such as metals. The delay time 'I'DF can be approximately expressed by the following equation.

TDE = CwL (ΔV)/Io −(
1) Here, Cw is the unit length of the wiring, L is the wiring length, ΔV is the potential change required for signal detection, and IO
is the output current that can be supplied to drive the output element. On the other hand, in the method using optical signals, the time delay in the optical waveguide becomes negligibly small, and the signal transmission delay time TDO is the delay time T++ from when the light emitting element is driven until the light is emitted. It can be expressed as the sum of the delay time Tnnn until outputting a potential change that is not necessary for signal detection. That is, Tno =
TDOE-1-Tnon (2). For comparison, if the light emitting element driven type is used and the current is the same as the output current of the conventional method, In, then Tnorq + TpoI)
can be approximately expressed as follows.

T+]og = C*Vn/Io −(
3) Tnon − (Cn + Ci) (ΔV)/(η
EηnIo) - (4) Here, CE, VD are the terminal capacitance and terminal frost, pressure of the light emitting element, and C10 is the terminal capacitance of the light receiving element M, ', Ci is connected to the terminal of the element. input capacity of the element for air signal detection ~ stiffness, ηE and η
D is the luminous efficiency and the light receiving efficiency, respectively.

Therefore, as is obvious from the two series of equations, the signal transmission time delay due to the conventional electrical signal depends on the length of the wiring,
On the other hand, since the signal converted into an optical signal does not depend on the wiring length, assuming the same manufacturing technology, up to what wiring length the conventional method is faster, or conversely, up to a minimum wiring length of L47tin. It can be compared that the optical conversion method is more advantageous when the wiring length exceeds the above. The answer is that with the current 5-4 μm rule manufacturing technology, the above L
On the other hand, the actual wiring length is longer than this, and Lm will increase as the integration density increases in the future.
Considering the decrease in in and the further increase in wiring length, even if photoelectric conversion time is required, TDo≦T
It becomes DI8. Furthermore, when the line width of an integrated circuit becomes 1 μm or less, the stray capacitance Cw of the wiring cannot be expected to decrease in proportion to the miniaturization of the line width, and the delay of the unit length of the wiring is 1 μm or less.
The degree of improvement is small in miniaturization of 1 tm or less. On the other hand, since the optical conversion transmission method reduces the delay time in proportion to the square of the miniaturization, it can be seen that the power of the optical conversion method is advantageous for most wiring lengths.

In this way, it can be concluded that the optical conversion method considered here by the present inventor is superior to the conventional wiring method.

One embodiment of the present invention based on these findings and principles is shown in FIG.

As in the conventional semiconductor integrated circuit structure, the substrate/
The substrate may be formed by laminating a semiconductor layer on a semiconductor crystal or insulator substrate layer, and a plurality of unit semiconductor integrated circuits may be formed on this as in the conventional case. However, since the present invention does not directly define each unit circuit itself, illustration and description thereof will be omitted.

Generally, an insulating film a is provided on the surface of the substrate for electrical wiring of an integrated circuit, isolation between elements, etc., but in this first embodiment, this insulating film a is provided on the surface of the substrate. It is used as a kind of cladding layer of the optical waveguide 3 formed in the. Therefore, if the insulating film is not formed in the area where the optical waveguide 3 is provided, the insulating film, cladding film, or reflective film may be formed separately for the purpose of the present invention. Of course, if the refractive index of the substrate 1 is smaller than that of the optical waveguide 3 to be formed, the optical waveguide 3 can also be formed directly on the substrate l.

At one end of the optical waveguide 3, there is a transmitting section Ej,j of a unit circuit consisting of
=1+2+5. . . ., but at the other end is a receiving section Di of another circuit that receives the signal from this unit circuit.

i=1.2,5. ... will be established. Each unit circuit is
A plurality of transmitters and receivers may be provided as necessary.

Specific configuration examples of each transmitter and receiver are shown in the figure. For the transmitting section EjK, an electro-optic conversion light emitting element 4/ such as a light emitting diode or a semiconductor laser may be provided on the substrate, and its active region or light emitting section 6 transmits light I- into the optical waveguide. Place it so that it can be fired once. The electrode region j for driving this light emitting element≠ can be formed in the substrate surface as shown in the figure.

On the other hand, the light-receiving element 10 as the receiving part Di is configured to form a pn junction between, for example, a first region 7 provided on the surface of the substrate and a second region /σ as a portion of the substrate around the first region 7. If the first region 7 is connected to a predetermined electric signal input terminal of a signal positioning circuit having this receiving section, the region 7 can be configured as follows.
The potential change that occurs can be detected as an information signal. The optical waveguide 3 is bent toward the substrate in order to guide light to the receiving section. In order to especially prevent light leakage at this bent end and the end on the transmitter side, a reflective film is provided around the end. When is greater than or equal to the critical angle, total internal reflection occurs, so a reflective film r may not be particularly required. This also applies to the case where a grating with a spacing matching the wavelength of the light used is provided at the end of the optical waveguide.

If the cross-sectional dimension of the twisted optical waveguide 3 is sufficiently large compared to the wavelength of the light used, the propagation state of the light wave within the optical waveguide is represented by geometrical optics, and therefore the optical waveguide connecting the light emitting part and the light receiving part is does not necessarily have to be linear. For example, an optical waveguide can be provided in a state in which several bent lines are connected. However, in this case, efficient transmission can be achieved by providing a light reflecting film or the like on the outside of the optical waveguide as necessary to prevent light from leaking from the waveguide.

The above is the first example, but as the cross-sectional dimension of the optical waveguide becomes finer to the same extent as the wavelength of the light inside the optical waveguide,
It is conceivable that the propagation state of light within the optical waveguide cannot be represented by geometrical optics, and that the optical waveguide cannot be easily bent. To deal with this, more precise processing techniques and higher quality optical waveguide materials are required, which may reduce the yield of the entire system and therefore make it difficult to reduce costs.

FIG. 2 shows an embodiment that can overcome this problem. The reference numerals in the corresponding figures indicate components corresponding to the components in the first embodiment, but as shown in a plan view with the optical waveguide 3 taken out in FIG. In this example, a planar optical waveguide 3 as a common optical waveguide structure is used instead of the striped optical waveguide dedicated to each of the transmitter and receiver pairs in the first embodiment. The transmitting section Ei and the receiving section Di of each unit circuit, which are to communicate with each other via optical waveguides, are exposed at a plurality of locations on the circumferential side wall of 3.

In the case shown, there are three transmitters E, ~E8 and a receiver 1)+
=Ds is shown for the sake of simplicity, and each pair forms a pair, and each pair is arranged at each vertex of the approximately triangular planar optical waveguide 3. Each vertex is rounded so that the pair of transmitting and receiving sections can be easily viewed, so depending on how you look at it, the planar waveguide 3 can be easily viewed as one short side and one long side nested.
It looks like a hexagonal shape, and it can be said that each pair of transmitting and receiving sections face each short side.

Of course, the shape of the planar optical waveguide is not limited to this and is arbitrary, and the number of single circuits and the number of transmitting and receiving sections are also arbitrary depending on the need.

Light-emitting element ≠, light-receiving element IO that constitutes each transmitter and receiver
As shown in the cross-sectional end view of FIG. 2(b), the structure may be the same as that shown in FIG. 1.

For example, in such an optical waveguide configuration, the light emitting part may be given directivity to send light only to a specific light receiving element, or it may be possible to send light only to a specific light receiving element, as shown by the arrow ■ in Figure 2 (α). In addition, by using non-directional light emitting diodes, all light receiving elements /θ
It is also possible to send the information to... Whether or not to receive the optical signal and use it as information can be left to the selection of each unit circuit.

If the optical waveguide is planar as in this embodiment, its cross-sectional dimension can be made sufficiently larger than the wavelength of the light wave therein, and the above restriction can be avoided.

Incidentally, FIG. 2(b) also schematically shows a semiconductor integrated circuit (c) which is formed using existing technology and which performs a predetermined function by handling electrical signals.

Regardless of the first or second embodiment, the material for the optical waveguide is as follows:
It is desirable that there is no absorption of light waves, or even if there is, there is very little absorption of light waves. For example, a material with a bandgap sufficiently larger than the energy of the light wave in it is preferable.

Next, we will discuss specific examples that are desirable from the viewpoints of materials and manufacturing methods.

When the substrate l is silicon, the light emitting element g is as follows:
On this silicon substrate, liquid phase or vapor phase epitaxial method,
A green light-emitting diode in which NU molecules are introduced as a luminescent center into TiJ-capable GrzP epitaxially grown by MBE or the like, or a red light-emitting diode in which ZsN atoms and O atoms are introduced are used, and as an optical waveguide 3 suitable for this, an impurity-doped one is used. It is better to use GaP 'it that is not available. Since the energy of light passing through the G and P optical waveguides is smaller than the band gap of the G and P, undesirable light absorption can be avoided.

Furthermore, if an opening is made in the insulating film λ on the substrate and GaP is epitaxially grown, a single crystal of GaP can be grown on the opening, and polycrystalline or amorphous Ga,
P grows. If the aforementioned N atoms, Zy* atoms, and O atoms are selectively introduced into the Gσ, P single crystal formed above the aperture, the light emitting element, the light receiving element, and the optical waveguide can be formed integrally, and they can be formed separately. When formed, the step of aligning each of the light emitting and light receiving elements and the optical waveguide can be omitted. The light emission mechanism may be due to the formation of a pn junction in GaP or a heterostructure in which carriers are injected from the junction surface between region j and GaP.

If G~tt 1-P is grown on the GaP in the light emitting element portion, the emission wavelength is smaller than the bandgap energy of GaP used for the waveguide, and no light absorption occurs. If the amount of In is further increased, a laser diode can be formed. Laser emission is p-type GaP/p or n-type Gaz
This is possible with a heterostructure of In 1-, Pz4 type GaP.

As described in detail above, according to the present invention, it is possible to reduce the signal transmission delay due to the wiring of semiconductor integrated circuits configured on the same substrate or chip, to fully demonstrate the performance improvement due to miniaturization, and to improve the performance between unit circuits. It is possible to increase the speed of signal transmission and improve the functionality of the entire system.

Further, in the case of a waveguide having a planar structure as shown in the second figure, an integrated optical bus function can be realized by configuring the light emitting elements with LEDs having little directivity. In other words, by connecting the required number of light emitting elements as signal sending ends and light receiving elements as signal receiving ends to the ends of this planar waveguide, a conventional electrical signal path can be established from any sending end to any receiving end. Signals can be transmitted with much smaller delays than when using lines.

[Brief explanation of drawings]

FIG. 1(cL) is a plan view schematic diagram of the first embodiment of the present invention, FIG. 1(b) is a cross-sectional end view taken along line X-X in FIG. 1(α), and FIG. Figure (0,) is a plan view schematic diagram of the main parts of the second embodiment, and Figure 2 (b) is the X in Figure 2 (a).
- a cross-sectional end view taken along the X-ray; In the figure, l is the substrate, 3 is the optical waveguide, ≠ is the light emitting element, IO
is a light receiving element, Ei is a transmitter, and Pi is a receiver.

Claims (4)

[Claims] (1) A plurality of coronation circuits, each including a semiconductor electronic element, are formed on the same substrate, and have a transmission path for transmitting signal information from a transmitter in one unit circuit to a receiver in another unit circuit. A semiconductor integrated circuit having a semiconductor integrated circuit structure, characterized in that the transmitting section is composed of an electro-optical conversion light emitting element, the receiving section is composed of a photoelectric conversion light-receiving element, and the transmission path is composed of an optical waveguide. structure. (2) The structure according to claim (1), wherein the optical waveguide is dedicated to a pair of transmitter and receiver. (3) The structure according to claim 1, wherein the optical waveguide is common to a plurality of pairs of transmitting sections and receiving sections. (4) The structure according to claim (3), wherein the light emitting element of the transmitter is non-directional.