JPS6237554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a matrix-type light emitting diode display device that can be manufactured at low cost with a simplified manufacturing process.

Conventionally, display devices using semiconductor light-emitting diodes include a hybrid display device in which multiple light-emitting diode chips of a predetermined shape are arranged on a single substrate, and a hybrid display device in which a plurality of light-emitting diode chips in a predetermined shape are arranged on a single substrate. A monolithic display device having a structure incorporating a light emitting diode element is known.

Among these, monolithic display devices are suitable for mass production because they allow precise display patterns to be easily formed using photoetching technology, and many light emitting regions can be formed at the same time. Furthermore, since it is possible to almost eliminate variations in brightness among each light emitting region, it is often used in digital display sections of handheld calculators and wristwatches, and display sections of various measuring instruments.

By the way, in this monolithic display device, it is necessary to electrically and optically separate each light emitting diode element formed in a single semiconductor substrate, and it is also necessary to provide a driving force for each separated light emitting diode element. A process for forming electrodes and lead wires for supplying voltage is required.

Conventionally, light emitting diode elements have been separated by separation methods such as etching or dicing, or by selectively diffusing impurities that form regions of the opposite conductivity type into predetermined regions of a semiconductor substrate of one conductivity type. Selective diffusion methods are often used to create light-emitting diode devices.

In addition, electrodes are formed on each light emitting diode element,
Furthermore, vapor deposition methods, wire bonding methods, etc. are used to connect lead wires, and in many display devices currently in use, one electrode is generally used as a common electrode and the other electrode is made independent. A structure is taken.

On the other hand, display devices have diversified in recent years, and even for display devices using light-emitting diodes, there is now a demand for display devices that can display complex patterns such as various characters and figures in addition to the conventional numeric display. It's here.

Further, display devices using light emitting diodes are being considered in some areas as small flat display devices to replace conventional cathode ray tubes.

However, with the structure in which the lead wires are drawn out independently from the electrodes formed on each of the light emitting diode elements as described above, the wiring structure becomes extremely complicated and it is difficult to obtain a display device that displays a precise pattern. In this type of display device,
A structure in which electrodes and lead wires are formed in a matrix and light emitting diode elements are located at the intersections of this matrix is suitable. Various matrix-shaped display devices have been proposed in the past, but the conventional The separated structure of the light emitting diode elements in a monolithic display device is not suitable for forming electrodes and lead wires in a matrix, and the formation process becomes complicated, making the display device itself extremely expensive. There was a problem with this.

The present invention has been made in view of the above-mentioned circumstances, and it is a group semiconductor material such as Si or Ge that can be obtained at low cost in a prescribed shape that is high quality and easy to handle in each manufacturing process. A new method is to use a compound semiconductor material such as or GaAs as a substrate, and to provide a diffusion layer that penetrates the front and back of the substrate to serve as a part of the electrode or an electrical separation zone for supplying drive current to the light emitting diode. It is an object of the present invention to provide a light emitting diode display device which has a structure that simplifies the manufacturing process and enables precise display.

Hereinafter, one embodiment of a light emitting diode display device according to the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway perspective view showing an embodiment of a light emitting diode display device according to the present invention, and FIG.
FIG. 3 is a sectional view of a main part of the same embodiment.

Here, 1 is a substrate made of, for example, p-type Si, and diffusion masks 2 and 3 made of an insulating material are adhered to the front and back surfaces of this substrate 1 in a predetermined shape. These diffusion masks 2 and 3 are made by, for example, exposing the front and back surfaces of the substrate 1 to a high-temperature oxidizing atmosphere to form a SiO ₂ film.
This is done using well-known photo-etching technology to remove unnecessary parts.
Diffusion masks 2 and 3 can be obtained by removing the SiO ₂ film.

Further, 4 is a method for removing impurities that become donors in Si, such as elements such as P, Sb, and Bi, from the striped opening portions partitioned by the diffusion masks 2 and 3 using a well-known thermal diffusion method or ion implantation method. This is a layer with a high impurity concentration obtained by diffusion (hereinafter referred to as a diffusion layer), and is provided to penetrate the front and back surfaces of the substrate 1. The lower surface of this diffusion layer 4 is in contact with an electrode on the back surface side, which will be described later, and a semiconductor layer that will become a part of the light emitting diode element is epitaxially grown on the surface, and a driving potential is applied to this semiconductor layer. A low-resistance layer is formed by diffusing donor impurities at a high concentration so that it becomes a part of the electrode for the electrode.

In this case, if the substrate 1 is thin, the diffusion layer 4 penetrating the front and back of the substrate 1 can be obtained by simply performing diffusion from either the front or back surface, but if a relatively thick substrate 1 is used, As shown in the figure, diffusion is performed from the front and back surfaces of the substrate 1 to form a diffusion layer 4 that penetrates the front and back surfaces.

Furthermore, 5 is an n-type GaP layer 5 epitaxially grown on the surface of the diffusion layer 4. this
Although the GaP layer 5 can be formed by a well-known vapor phase growth method or a liquid phase growth method, the present inventor obtained the GaP layer 5 by a cluster ion beam evaporation method.

In this cluster ion beam evaporation method, component elements of a compound, in this example Ga and P, are placed in a plurality of closed crucibles each having at least one nozzle.
and evaporated by heating and adding a donor, for example, S, in GaP, and controlling the vapor deposition of the component elements to a pressure at least 1/100 lower than the pressure of the vapor in the crucible. By ejecting it into a high vacuum region with a pressure of: A group, a so-called cluster, is generated.

By ionizing at least one atom in the cluster of the deposited material, accelerating it by an electric field, and causing it to impinge on the surface of the substrate 1 which is heated by an appropriate means and which is not covered by the diffusion mask 3, An epitaxial layer of GaP compound semiconductor single crystal is obtained.

In this case, when the cluster ions impinge on the substrate 1, their kinetic energy is converted into sputtering energy, thermal energy, ion implantation energy, etc. on the surface of the substrate 1, and furthermore, the unique surface migration of the cluster ions is With the addition of the Yong effect, etc., a good epitaxial layer can be formed.

Furthermore, a p-type GaP layer 6 is epitaxially grown on the n-type GaP layer 5 to form a pn junction 7. Like the GaP layer 5, this GaP layer 6 can also be formed by cluster ion beam evaporation.

Also, if O is added together with dopants such as S and Zn when growing the GaP layers 5 and 6,
A red light emitting diode is obtained, and by adding N, a green light emitting diode is obtained.

Reference numeral 8 denotes an electrode on the back side of the substrate 1, which is attached in the X direction along the diffusion layer 4 as shown in FIG. 1, using the diffusion mask 2 attached to the back side of the substrate 1 as an electrically insulating layer. , 9 are surface-side electrodes formed on the GaP layer 6 and in ohmic contact with the GaP layer 6.

The electrodes 9 are commonly connected to each column by a lead wire 10 in a direction intersecting with the electrode 8, that is, along the Y direction shown in FIG. Each is connected to an electrode pad 12. In this case as well, the diffusion mask 3 serves as an electrical insulating layer, so the lead wire 1
An advantage arises that 0 can be formed very easily, for example by a vapor deposition method. Also, 13 is
This is an electrode pad of the electrode 8 that is electrically connected to the electrode 8 via the diffusion layer 4.

As shown in FIG. 1, the electrode 8 is formed in the X direction and the lead wire 10 is formed in the Y direction.
A display device in which a light emitting diode element 11 having a pn junction 7 at the intersection of the two is formed can be obtained.

That is, in the above embodiment, Si, which is available at low cost, is used as the substrate 1, and the diffusion layer 4 in which n-type impurities are diffused at a high concentration is provided through the front and back surfaces of the substrate 1, and the diffusion layer 4 is used to emit light. Diode element 1
In addition, the portion of the substrate 1 on which the diffusion layer 4 is not formed is used as a part of an electric path for supplying a driving current to each light emitting diode element 11.
This is an electrical isolation zone in the Y direction.

Furthermore, the diffusion masks 2 and 3 used to form the diffusion layer 4 are used as an electrically insulating layer for the electrode 8 and the lead wire 10 in subsequent steps.

Therefore, the separation structure and electrode arrangement structure of each light emitting diode element 11 are extremely simplified, and a matrix type display device can be easily obtained.

Further, since Si used as the substrate 1 is opaque to visible light, there is little blurring of the light emitted from each light emitting diode element 11, and a clear display can be obtained.

Incidentally, in the above embodiment, an example was described in which a p-type Si substrate 1 was used and a light emitting diode element 11 was formed thereon.
It is also possible to use Si in the form of Si.

An example in this case is shown in FIG.

In the embodiment shown in FIG. 3, a diffusion mask 22 is first formed on the back surface of a substrate 21 made of n-type Si, as shown by the two-dot chain line in the figure, and a diffusion mask 22 is formed from the back surface side.
A p-type diffusion layer 24 is formed in which an impurity that becomes p-type, for example, B, is deeply diffused. This diffusion layer 24
is embedded in the n-type substrate 21 and functions as an insulating separation band for electrically insulating each n-type region.

Furthermore, 23 is an insulating mask formed on the surface of the substrate 1 at the same time as the formation of the diffusion mask 22, or in a process before or after the formation of the diffusion mask 22.

First, an n-type GaP layer 25 is selectively epitaxially grown in the opening of the substrate 1 defined by the insulating mask 23, and then a p-type GaP layer 26 is epitaxially grown on the surface thereof. Light emitting diode element 31 having pn junction 27
form.

On the other hand, reference numeral 28 denotes a backside electrode that is attached to the exposed backside of the substrate 1 after the diffusion mask 22 is peeled off in an arbitrary step after the formation of the diffusion layer 24. In this embodiment, the substrate 1 is n Since the electrode is a shaped semiconductor, an electrode made of a material that makes ohmic contact with the substrate 1, for example, an Au-Sb alloy, is used.

Furthermore, 29 is an electrode on the surface side that makes ohmic contact with the GaP layer 26, and 30 is an electrode 29 in each row arranged in a direction intersecting the electrode 28.
This is the lead wire connected to.

That is, in this second embodiment, the n-type substrate 2
The structure is such that a p-type diffusion layer 24 serving as an electrical isolation layer is provided so as to penetrate the front and back surfaces of the substrate 1.The structure shown in FIG. A matrix type display device in which lines can be easily formed can be obtained.

Furthermore, FIG. 4 shows a third embodiment according to the present invention.

The embodiment shown in FIG. 4 has the same basic structure as the embodiment shown in FIG. In order to do this, grooves 1 are formed by etching in the portion of the substrate 1 where the diffusion layer 4 is to be formed.
4 is formed, and an impurity serving as a donor is diffused in Si at a high concentration from the surface side of the substrate 1 to form a diffusion layer 4. Of course, the shape of the grooves 14 can be arbitrarily selected, such as grooves arranged in stripes or holes arranged in a matrix.

Since the other parts are almost the same in structure as shown in FIG. 1, the same reference numerals are given to the parts having the same functions, and the explanation thereof will be omitted.

Furthermore, in each of the embodiments described above, p-type GaP layers 6 and 26 are epitaxially grown on n-type GaP layers 5 and 25 to form p-n junctions 7 and 27. This is achieved by selectively diffusing impurities that act as acceptors in GaP, such as Zn, into the n-type GaP layers 5 and 25 using a well-known method. ni p
A light emitting diode element having a pn junction may be formed by a so-called planar technique in which a shaped GaP layer is formed.

Furthermore, in the embodiment shown in FIG. 1, an n-type GaP layer is epitaxially grown on the entire surface of the diffusion layer 4 formed in stripes along the X direction of the substrate 1. As shown in FIG. 5, an n-type GaP layer 5 is selectively epitaxially grown only in the portion that will become the light emitting diode element 11, and a p-type GaP layer 6 is grown thereon. It is also possible to have a structure in which each light emitting diode element 11 is completely separated.

The structure shown in FIG. 5 eliminates wasted material, and can also prevent light bleeding, which is a problem with GaP light emitting diodes.

In other words, GaP has a large energy gap of approximately 2.26 eV at room temperature, and as light is rarely absorbed within the crystal, light propagates to light-emitting diode elements to which no driving signal is applied, causing smearing. However, as shown in FIG. 5, by eliminating unnecessary portions of the GaP layer, there is an advantage that bleeding is eliminated and a high-quality display can be obtained.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings. For example, the substrate 1 may be made of a unitary semiconductor material such as Ge in addition to Si.
Semiconductor materials that are opaque to visible light, such as compound semiconductors such as GaAs, can also be used, and compound semiconductors such as GaAs, GaAsP, GaAlAs, and ZnSe can be used as light-emitting diode elements grown on the substrate. By using a semiconductor with a smaller bandgap as a substrate than the semiconductor layer of the light emitting diode element to be formed,
It can be implemented with various modifications without changing the gist thereof.

As described above, the light emitting diode display device according to the present invention has a substrate 1 made of a semiconductor of one conductivity type.
A diffusion layer 4 is formed in a stripe shape by penetrating the front and back surfaces of the substrate 1, and on the surface of the substrate 1 on which the diffusion layer 4 is formed, a light emitting diode element 11 section consisting of a p layer and an n layer, which are separate members from the substrate 1, is formed. The surface side electrode part 9 is formed to connect the surface side electrode part 9, and the underlying surface of the substrate 1 and the semiconductor layer of the light emitting diode element 11 formed directly on the underlying surface are of the same conductivity type. The back side electrode portion 8 is directly fixed and supported on the substrate side on the back side, and the diffusion layer 4 of the substrate 1 is
Alternatively, since the other striped portion of the substrate is used as a part of one matrix electrode, the material of the substrate 1 can be a group semiconductor material such as Si or Ge, or a compound semiconductor material such as GaAs. This has the effect of expanding the range of materials. Further, the electrodes for driving the light emitting diode element portions are also supported and formed directly on both the front and back sides of the substrate 1, which will become part of the matrix electrode, and the thickness of the substrate 1 can be made sufficiently thick.
Since it does not require any effort such as drilling holes, it has the effect of being easy to handle and manufacture.

Further, in the present invention, since the substrate 1 is made of a semiconductor having a smaller bandgap than the semiconductor layer of the light emitting diode element 11 formed thereon, the light from the light emitting diode element 11 that is lit is transmitted to the adjacent unlit light emitting diode element 11. There is no phenomenon of so-called light leakage from the light emitting diode elements, and the optical separation between the light emitting diode elements can be effectively and reliably achieved.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of essential parts showing an embodiment of a light emitting diode display device according to the present invention;
FIG. 2 is an enlarged cross-sectional view of a main part of the same embodiment, and FIGS. 3 and 4 are cross-sectional views of main parts showing different embodiments of the light emitting diode display device according to the present invention. FIG. 5 is a perspective view of main parts showing still another embodiment of the light emitting diode display device of the present invention. 1...Substrate, 4...Diffusion layer, 5, 6...GaP
Layer, 7... P-n junction, 8, 9... Electrode, 10...
... Lead wire, 11 ... Light emitting diode element, 14
……groove.

Claims (1)

[Claims] 1. A diffusion layer of the opposite conductivity type formed in a stripe shape through the front and back surfaces of a substrate made of a semiconductor of one conductivity type with a smaller bandgap than that of the semiconductor layer of the light emitting diode element portion 11 to be formed. The surface of either this diffusion layer or the substrate partitioned by this diffusion layer is used as a base, and on this base, a member separate from the substrate and having the same conductivity as the base is placed at a predetermined distance. a plurality of light emitting diode element parts having p-n junctions formed by forming a semiconductor layer of a shape and a semiconductor layer of an opposite conductivity type thereon, and the diffusion layer in which the light emitting diode element parts are formed. an electrode portion on the back surface side formed by being directly fixedly supported on the substrate side on the back surface or the back surface of the substrate partitioned by a diffusion layer; and an electrode portion on the front side formed on the light emitting diode element portion; A light emitting diode display device comprising a lead wire section connected to each of the electrode sections. 2. The light emitting diode display device according to claim 1, wherein the substrate has a groove portion provided in a portion where the diffusion layer is formed. 3. The lead wire portion connected to the electrode portion on the front side is configured to commonly connect the electrode portions on the front side arranged in a direction crossing the electrode portion on the back side. 2. The light emitting diode display device according to item 2.