JPH0395822A - Semiconductor electron emitting element and its manufacture - Google Patents

Abstract

PURPOSE:To have an extremely thin n-type semiconductor which is uniform, highly concentrated and with low defects by forming a Schottky junction in parallel to the surface of a semiconductor, providing an extracting electrode and using a material stable in the atmosphere with a small work function as a Schottky electrode. CONSTITUTION:An electrically insulating layer provided with at least one opening is provided on a surface of a semiconductor base 1 in parallel to a Schottky junction, and further at least one extracting electrode 7 is provided for decreasing a work function of the Schottky electrode 5 at the edge of the opening on the electrically insulating layer at an edge of the opening. Thus as a result of a strong electric field in the vicinity of the Schottky electrode, apparent reduction in the work function is obtained as well as formation of space charge can be prevented. In addition in the periphery of a part having low breakdown voltage, an n-type region 3 for isolating the part having low breakdown voltage on the surface of the semiconductor base is provided. Thus a leak due to a high electric field at the edge of the Schottky electrode can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electron-emitting device and a method for manufacturing the same, and particularly relates to an electron-emitting device and a method for manufacturing the same. The present invention relates to an electron-emitting device that emits electrons (electrons) to the outside, and a method for manufacturing the same.

[Prior Art] Conventionally, among electron-emitting devices, those using avalanche amplification are disclosed in U.S. Pat. No. 4,259,678 to U.S. Pat.
As described in No. 303930, a p-type semiconductor layer and an n-type semiconductor layer are joined to form a diode structure, and a reverse bias voltage is applied to both ends of this diode to cause avalanche amplification and hot the electrons. A device is known in which electrons are emitted from the surface of an n-type semiconductor layer to which cesium or the like is attached to lower the work function of the surface.

[Problems and effects to be solved by the invention] In the above conventional example, cesium or cesium oxide is formed on the surface of the electron emitting part in order to lower the work function of the electron emitting part. Because it is extremely active in Since there are always challenges such as change,
It has been desired to develop an electron-emitting device having a structure in which materials other than cesium or cesium oxide can be used.

Furthermore, in the conventional example described above, hot electrons generated at the pn interface lose energy due to collapse when passing through the n-type semiconductor layer. In order to avoid this, it is necessary to make the n-type semiconductor layer extremely thin (less than 200 layers). However, it is difficult to make an extremely thin n-type semiconductor layer uniform, highly concentrated,
In addition, since there are many problems in the semiconductor manufacturing process in order to produce such a device with low defects, it has been difficult to stably produce such a device in practice.

[A Thousand Steps to Solve the Problems] A first aspect of the present invention is to provide a semiconductor substrate having a p-type semiconductor layer on at least a portion of its surface, the impurity concentration of which is in a concentration range that causes electron avalanche breakdown; a Schottky electrode joined to a p-type semiconductor layer; means for applying a reverse bias voltage to the Schottky electrode and the p-type semiconductor layer to emit electrons from the Schottky electrode; a Schottky junction between the P-type semiconductor layer and the Schottky electrode is formed parallel to the semiconductor substrate surface, and at least one an electrically insulating layer having two openings on the surface of the semiconductor substrate parallel to the Schottky junction, and an electrically insulating layer provided on the electrically insulating layer at an edge of the opening for reducing the work function of the Schottky electrode. At least one extraction electrode is provided in a part of the Schottky junction, and a part with a concentration range and layer structure such that the breakdown voltage is locally lower than in other parts (hereinafter referred to as a part having a low breakdown voltage). an n-type region for isolating the portion having the low breakdown voltage on the surface of the semiconductor substrate is provided around the portion having the low breakdown voltage, and the Schottky electrode is connected to the Schottky electrode at the time of breakdown. It exists in a semiconductor electron-emitting device characterized by being thin enough to allow electrons generated within the depletion layer of the junction to pass through.

The present invention includes a semiconductor substrate having a p-type semiconductor layer having an impurity concentration in a range that causes electron avalanche breakdown on at least a portion of its surface. ．． As this semiconductor substrate, a silicon substrate, a gallium arsenide substrate, or another substrate may be used.

In the present invention, a Schottky junction between a p-type semiconductor layer and a Schottky electrode is formed parallel to the surface of a semiconductor substrate.

By forming a Schottky junction parallel to the surface of the semiconductor substrate, the depletion layer and electric field are formed parallel to the semiconductor surface, so the electrons are aligned in a direction perpendicular to the electric field, that is, in a vector that goes from inside the semiconductor to the outside. It will be done. For this reason, the spread of the energy distribution of electrons becomes smaller, so the spread of the energy distribution of emitted electrons also becomes smaller.
An electron beam that is advantageous for convergence etc. can be obtained.

As the material for the Schottky electrode, it is preferable to use a material that is electrically conductive and has a small work function, and for this purpose, it may have a multilayer structure of a conductive material and a material that has a small work function (Claim 9). ).

For example, when composed of only one layer, LaBa, BaB6
, CaBa , SrBa , CeBa . YB6,Y
A boride such as B4 may be used (Claim 10).

The thickness of the Schottky electrode may be thin enough to allow electrons generated within the depletion layer of the Schottky junction to pass through during breakdown. 0.1 μm or less is preferable (
Claim 5).

Note that the portion having a low breakdown voltage may be formed by locally doping the p-type semiconductor layer with a high concentration (claim 2).

By providing a locally heavily doped region in the P-type semiconductor layer, an extremely thin depletion layer is formed in the heavily doped region during operation, locally lowering the breakdown voltage and making electrons hot under a high electric field. It can give you the energy you need to do it.

Further, it is preferable that the width of the heavily doped p-type region is 5 μm or less (claim 4). This can prevent thermal destruction of the element due to current concentration.

In the present invention, an electrically insulating layer having at least one opening is provided on the surface of the semiconductor substrate in parallel with the Schottky junction, and further, an edge of the opening on the electrically insulating layer is provided at an edge of the opening. is provided with at least one extraction electrode for lowering the work function of the Schottky electrode.

Thereby, as a result of the strong electric field near the Schottky electrode surface generated via the extraction electrode, the work function is apparently reduced (Schottky effect) and the formation of space charges can be prevented.

Note that the insulating layer may have a one-layer structure, or may have a two-layer structure. For example, it may be made of two layers of silicon oxide and silicon nitride (claim 12). Note that the shape of the opening may be circular, or, when used for display purposes, it is appropriate to use a square or rectangular opening.

When used in a circular shape, the extraction electrode may be circular.

For example, gold may be used as the material for the extraction electrode (
Claim 11). In addition, drawer N. The pole may have a single layer structure or a multilayer structure (claim 7).

It is also possible to divide the extraction electrode into two or more sub-electrodes to provide a lens function or a deflection function.

Note that the ratio of the diameter of the opening to the thickness of the insulating layer is preferably 2:1 or less (Claim 6).

By doing so, a high electric field is formed in the vicinity of the Schottky electrode, and it is possible to effectively extract electrons and lower the work function due to the Schottky effect.

In the present invention, an n-type region is provided around the portion having a low breakdown voltage to isolate the portion having the low breakdown voltage on the surface of the semiconductor substrate.

rTHE BELL SYSTEM TEC}INIc
AL JOURNAL, February 1968 p195-p
By forming an n-type region around the Schottky electrode as shown in 208, leakage due to the high electric field at the edge of the Schottky electrode can be prevented.

In addition, by using a low work function material that is stable in the atmosphere and conductive for the Schottky electrode, it is possible to form a depletion layer only on the semiconductor side, and the velocity vector of electrons is uniformly aligned perpendicular to the semiconductor surface. This makes it possible to narrow the width of the energy distribution of emitted electrons.

Further, since the Schottky electrode can be formed by electron beam evaporation or the like, by forming it extremely thin, scattering of electrons when passing through the Schottky electrode can be suppressed to a low level, and handling in the atmosphere is extremely easy.

The second gist of the present invention is to cover the surface of a semiconductor substrate in which a low concentration p-type semiconductor layer is grown on a high concentration p-type semiconductor substrate with an insulating layer, and to open a portion that will become an n-type region by etching to provide a donor layer. Ions are implanted, then acceptor ions are implanted through the insulating layer to form a highly concentrated p-type region, and then annealing is performed with the insulating layer left in place to form a contact electrode on this insulating layer, and then an extraction electrode is formed. forming an insulating layer for the purpose, further forming an extraction electrode layer on the insulating layer,
After forming an opening in the extraction electrode, the insulating layer for forming the extraction electrode is patterned by etching to expose the surface of the semiconductor layer, and finally a Schottky electrode is formed using the formed opening as a mask. There exists a method for manufacturing an electron-emitting device characterized by forming the electron-emitting device.

According to the second summary, by using the ion implantation method, the highly concentrated ρ-type region that is the electron emission region can be miniaturized to obtain an ideal point electron source, and that the insulating film formed at the beginning can be left until the end. Contact us! Not only is it possible to position the pole with a self-line, and by forming the Schottky electrode last by using the opening as a mask after forming the opening, it is also possible to form 7 lines of Schottky electrode. , the oxidation that occurs during the Schottky electrode process step,
Physical and chemical changes such as etching can be avoided. In addition, by making the insulating layer and extraction electrodes have a multilayer structure, By fabricating a 3I rough lift-off shape (inverted Taber), it became possible to create a shape that effectively draws out electrons while avoiding charge-up.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

Figure 1 (A). (B) is a schematic diagram of the first embodiment of the semiconductor electron-emitting device of the present invention, FIG. 1(A) is a plan view, and FIG. 1(B) is a cross-sectional view taken along the line A-A. It is. In the case of this example, a p-type gallium arsenide substrate 1 doped with Zn having carriers of 8X10'1'atoms/cm' is doped with Be having carriers of 5X10'' atoms/cm3.
A substrate on which a doped p-type shrimp layer (p-type semiconductor layer) 3 was formed by MBE growth (molecular beam epitaxy) was used as a raw material.

Next, as shown in FIG. 2, 2,000 silicon nitride films 13a are deposited by the CVD method, and then the silicon nitride films 13a are appropriately patterned and removed to form an n-type region and St ions are focused. The SL ion concentration was implanted at two different voltages of 160 keV and 80 keV using a doped ion beam device so that the concentration of SL ions gradually decreased from the surface (to obtain a graded junction), and at the same time, Be ions were implanted at 80 keV for nitriding. It was implanted through the silicon film 13a. By implanting in this way, the n-type region 3
is formed to a depth of 5000, and at the same time a high concentration ρ type region 4 is formed.
Obtained at a depth of 2,000 people and a diameter of 2 μΦ.

As mentioned above, by using this maskless implantation, it is not only possible to perform multi-stage implantation and implantation of different types of ions simultaneously, but also to narrow down the beam to about 0.1 μm, so it is possible to implant only high-concentration p-type regions. Instead, the entire device structure can be fabricated in the submicron region, and a fine spot-shaped electron source can be fabricated.

Next, while leaving the silicon nitride film 13, the ion-implanted portion is appropriately annealed as shown in FIG.
3. According to this method, the n-type region forming portion can be connected to the contact electrode 12 by a self-line.

Furthermore, as shown in FIG. 4, only the Ai near the high concentration p-type region is removed with phosphoric acid using an appropriate mask.
2000 pieces of silicon oxide 13b and 1 μm silicon nitride 11 were deposited, and then 2000 pieces of gold were vapor-deposited by applying an electric current 8i7. Next, an opening is formed in the upper part of the electron source using a resist, and after first dissolving the gold of the contact electrode 7 with a mixed etchant of potassium iodide and iodine, the silicon nitride film 1 is formed using a CF4 busma etchant.
1 was patterned, and then the silicon oxide 13b was removed by wet etching using hydrogen fluoride and ammonium fluoride. At this time, a good taper shape was obtained at the bottom of the extraction electrode by taking advantage of the fact that the etch rates of silicon oxide and silicon oxide are greatly different due to wet etching.

Furthermore, after the silicon nitride film 13a near the high concentration p-type region 4 was removed again by CF4 plasma etching, BaBa was deposited by electron beam evaporation. BaB. was deposited so as to be connected to the contact electrode 12 using the opening formed above as a mask to form a good Schottky junction. Finally, Baa of the unnecessary part along with the resist. A Schottky type electron source shown in FIG. 1(B) was fabricated by removing .

The structure of the electron-emitting device manufactured by the above method is shown in the first example.
This will be explained based on FIGS. (A) and (b).

In the electron-emitting device according to the wood embodiment, a Schottky junction is formed by contacting the highly doped p-type region 4 and the Schottky electrode 5 on the semiconductor substrate surface, and by applying a reverse bias to both ends of the Schottky electrode. Avalanche amplification occurs to generate electron-hole pairs, and the generated electrons are emitted from the semiconductor surface. In this example, silicon nitride 11 was formed on silicon oxide 13, and lead electrode 7 was formed of gold.

Further, in this embodiment, a lower breakdown voltage is generated in the portion of the Schottky junction 14 within the opening than in the remaining portion of the Schottky junction. In this example, Schottky junction 1
The depletion layer 6 of No. 4 is formed thinly at the junction 14, thereby producing a low breakdown voltage. In this embodiment, such a local reduction in breakdown voltage is achieved by providing the heavily doped p-type region 4 in the junction 14. Further, in order to prevent leakage at the edge portion of the Schottky junction, an n-type region 3 is provided around the Schottky electrode to form a guard ring, thereby avoiding unnecessary current leakage.

Further, in this embodiment, a contact electrode 12 is provided, and the n-type region 3 and the contact electrode 12 are connected. By forming the contact electrode 12 in advance and finally connecting the Schottky electrode 5 to the contact electrode 12 in this way, a process with Schottky characteristics can be carried out, compared to the case where a Schottky junction is formed in advance. This can prevent chemical changes in the Schottky electrode and chemical changes in the Schottky electrode.

In this embodiment, the Schottky electrode 5 has a work function of 3.4e.
V's BaB. is used. BaB. and p-type GaAs
According to experiments, the Schottky barrier height with φap”
0. 6 6 (V), forming a clear Schottky junction. BaB6 exhibits sufficient electrical properties, and was formed as a film with a thickness of 100 nm by electron beam evaporation while maintaining the stoichiometric composition.

In addition, p-type groups Fj. 1, it is desirable to use a high concentration substrate. Each impurity concentration in the illustrated embodiment in FIGS. 1(A) and (B) is 1×10 18 atoms/cm 3 for the n-type region 33,
The p-type region 4 has a density of 7×10 atoms/cm'. The p-type semiconductor layer 2 has 5×10” atoms/am3, and the p-type substrate 1 has 8×1
By setting the above concentration, the depletion layer of the Schottky junction 14 has 800 atoms at breakdown, and a breakdown voltage of 5V and a maximum electric field of 1xlO'V/cm can be obtained.Generally, electrons are obtained by avalanche breakdown. The higher the electric field, the greater the energy, and the highly doped p-type region can be doped to a concentration that provides the largest electric field, that is, a doping amount that does not allow tunnel breakdown to dominate breakdown, giving large amounts of energy to electrons. I can do it.

In this embodiment, gallium arsenide is used as an example of a semiconductor substrate, but the semiconductor substrate of this device is not limited to gallium arsenide, but may also be a semiconductor such as silicon, silicon carbide, gallium phosphide, etc. Materials that form key junctions, have large Schottky barriers, and have large band gaps are more desirable.

A method for manufacturing the electron-emitting device shown in FIGS. 1A and 1B will be described below with reference to FIGS. 2, 3, and 4.

[Another Embodiment] FIG. 5 shows another embodiment of the present invention, in which a guard ring corresponding to the n-type formation region of the device shown in FIG. 1(B) is first formed, and then Furthermore, a p-type region is formed. By forming this double semiconductor layer, the formation situation of the depletion layer 6 shown in FIG. 1(B) is different,
It was possible to shorten the recovery time during switching due to the so-called charge accumulation effect. The manufacturing method for this device is such that following the formation of the n-type region 3 in the above-described device manufacturing method, p
This can be obtained by implanting Be ions of 40 keV into the mold region with a peak of 4° or more of 1019 atoms/cm'. If maskless ion implantation is used, steps such as mask shaping can be further simplified.

[Effects of the Invention] As explained in detail above, in manufacturing a Schottky electron source according to the present invention, the spread of the energy distribution of emitted electrons is narrowed by forming a Schottky junction parallel to the semiconductor surface. I can do it. Further, by providing an extraction electrode, the work function of the surface is lowered and the space charge is removed, thereby improving the electron emission efficiency. Furthermore, by using a material that has a small work function and is stable in the atmosphere for the Schottky electrode, it is possible to improve efficiency and make it easier to operate in the atmosphere. Next, by providing a guard ring in the n-type region in the Schottky junction, we prevent leakage that occurs around the electrode and improve efficiency, and we also provide a small high-concentration p-region to concentrate the electrons and reduce the This has the effect of preventing element destruction due to heat generation.

In addition, since conventional semiconductor formation technology and thin film formation technology can be used in the production of semiconductor electron-emitting devices, there are advantages such as the ability to fabricate the device of the present invention at low cost and with high precision using established technology. do.

The semiconductor electron-emitting device of the present invention is suitably used in displays, EB drawing devices, vacuum tubes, and can also be applied to electron beam printers, memories, and the like.

[Brief explanation of drawings]

Figure 1 (A). (B) is a schematic diagram of the first embodiment of the present invention. 2 to 4 are cross-sectional views of FIG. 1(B) at each step of the method for manufacturing the device of the present invention. FIG. 5 shows another embodiment of the semiconductor electron-emitting device of the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor base, 2... P-type region, 3... N-type region, 4... High concentration p-type region, 5... Schottky electrode, 6... Depletion layer, 7... ...Extraction electrode, 8...
・Ohmic electrode, 9, 10++ Power supply, 11, 1.3
a, b゛゜゛Insulating film, 12... Contact electrode, 14
...Schottky junction. Figure 1 (A) Figure 1 (B) Figure 2 Figure 4

Claims (17)

[Claims] (1) a semiconductor substrate having a p-type semiconductor layer on at least a portion of its surface having an impurity concentration in a concentration range that causes electron avalanche breakdown; a Schottky electrode bonded to the p-type semiconductor layer; and the Schottky electrode. An electron emission device comprising: means for applying a reverse bias voltage to an electrode and the p-type semiconductor layer to cause electrons to be emitted from the Schottky electrode; and an extraction electrode for extracting the emitted electrons to the outside. In the device, a Schottky junction between the p-type semiconductor layer and a Schottky electrode is formed parallel to the surface of the semiconductor substrate, and an electrically insulating layer having at least one opening is formed parallel to the Schottky junction between the semiconductor substrate and the Schottky electrode. Provided on the surface of the substrate, at least one extraction electrode for lowering the work function of the Schottky electrode is provided on the electrical insulating layer at the edge of the opening, and at least one extraction electrode is provided on the electrically insulating layer at the edge of the opening, and at least one extraction electrode is provided in a portion within the Schottky junction. A region with a concentration range and layer structure such that the breakdown voltage is locally lower than that of the region (hereinafter referred to as a region having a low breakdown voltage) is provided, and the low breakdown voltage is applied around the region having the low breakdown voltage. an n-type region is provided on the surface of the semiconductor substrate, the Schottky electrode being thin enough to allow electrons generated within the depletion layer of the Schottky junction to pass through during breakdown; A semiconductor electron-emitting device characterized by: (2) The semiconductor electron-emitting device according to claim 1, wherein the portion having a low breakdown voltage is a high concentration p region formed by locally doping the p-type semiconductor layer with a high concentration. . (3) The semiconductor electron-emitting device according to claim 2, wherein the heavily doped p region is in contact with the Schottky junction. (4) The semiconductor electron-emitting device according to claim 2 or 3, wherein the width of the heavily doped p region is 5 μm or less. (5) The semiconductor electron-emitting device according to any one of claims 1 to 4, wherein the Schottky electrode has a thickness of 0.1 μm or less. (6) The semiconductor according to any one of claims 1 to 5, wherein the opening is formed of at least one insulating layer, and the ratio of the diameter of the opening to the thickness of the insulating layer is 2:1 or less. Electron-emitting device. (7) The semiconductor electron-emitting device according to any one of claims 1 to 6, wherein the extraction electrode is formed of at least one layer of electrodes. (8) Claims 1 to 7 characterized in that the shape of the opening is circular, and the shape of the extraction electrode is circular.
The semiconductor electron-emitting device described above. (9) The electron-emitting device according to any one of claims 1 to 8, characterized in that the Schottky electrode contains at least one layer of a material having conductivity and a small work function. (10) The materials with small work functions are LaB_6, Ba
B_6, CaB_6, SrB_6, YB_5, CeB_
10. The semiconductor electron-emitting device according to claim 1, wherein the semiconductor electron-emitting device is a boride such as YB_4 or YB_4. (11) The semiconductor electron-emitting device according to any one of claims 1 to 10, wherein the extraction electrode is made of gold. (12) The semiconductor electron-emitting device according to any one of claims 1 to 11, wherein the insulating layer under the extraction electrode is formed of two layers of silicon oxide and silicon nitride. (13) A semiconductor electron-emitting device according to any one of claims 1 to 12, wherein the semiconductor is made of gallium arsenide. (14) A low concentration p-type semiconductor layer is grown on a high concentration p-type semiconductor substrate. The surface of the semiconductor substrate is covered with an insulating layer, the portion that will become the n-type region is opened by etching, donor ions are implanted, and then donor ions are implanted. Acceptor ions are implanted through the insulating layer to form a highly concentrated p-type region, and then annealing is performed with the insulating layer left to form a contact electrode on this insulating layer.
Furthermore, after forming an insulating layer for forming an extraction electrode, further forming an extraction electrode layer on the insulating layer, and providing an opening in the extraction electrode, the insulating layer for forming an extraction electrode is patterned by etching. and, after exposing the surface of the semiconductor layer, a Schottky electrode is finally formed using the formed opening as a mask. (15) The method for manufacturing an electron-emitting device according to claim 14, wherein the donor ions and acceptor ions are implanted by an ion implantation method. (16) The method for manufacturing an electron-emitting device according to claim 15, wherein the ion implantation is performed at least partially using a maskless ion implantation method. (17) A p-type region formed by an n-type region formed during donor ion implantation and a low-concentration p-type region in contact with the n-type region
17. The method of manufacturing an electron-emitting device according to claim 16, wherein the implantation is performed at least once so that the breakdown voltage of the -n junction is maximized.