JPS5832445B2 - Manufacturing method of target electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a target electrode, particularly a target electrode for a two-electron mirror scan converter tube.

Since the two-electron mirror type scan converter tube includes a writing electron gun and a reading electron gun, it has the advantage of being able to perform a reading operation at the same time as a writing operation.

The target electrode of such a scan converter tube is formed using, for example, a silicon single crystal substrate, and a charge image written on the surface of the substrate on the write electron gun side is induced by electron impact to the surface on the read electron gun side. It is percolated and moved by conductivity effects.

However, in order to perform the osmotic movement, approximately 10k
It has the disadvantage that it requires a high voltage of V and has a short charge accumulation time.

In addition, a device having a transmission grid type target electrode with an insulating film attached to one side of a metal mesh plate can operate at a low voltage, but has the disadvantage that the resolution is low and it is difficult to obtain good image quality.

The present invention provides a method for manufacturing a target electrode for a two-electron mirror scan converter tube, which has high resolution, little shading, long continuous readout time, and can operate stably at a relatively low voltage. This will be explained together with the embodiments shown in the drawings.

Referring to FIG. 1, a glass bulb 1 includes a write/erase electron gun 2, a readout electron gun 3, and a target electrode 4.
These form a two-electron mirror type scanning converter tube.

As shown in FIG. 2, the target electrode 4 includes a porous silicon oxide film 5, a thin metal film 6 as a signal electrode deposited on the lower surface of the porous silicon oxide film 5, and a cylindrical silicon film supporting the silicon oxide film 5. The ring-shaped second metal film 8 spans the side wall of the cylindrical part 7 and the periphery of the silicon oxide film 5. It is fixed onto the surface of the metal ring 9 using an annular metal plate 10 as a pressing tool and a pin-shaped elastic conductor 11.

Then, the silicon oxide film 5 is connected to the write/erase electron gun 2.
The metal film 6 faces the readout electron gun 3.

Further, the lower end surface of the silicon cylindrical portion 7 is in contact with the top surface of the metal ring 9 through the extension of the second metal film 8, so that the metal film 6 is connected to the metal ring 9 through the second metal film 8. 9 and the metal ring 9 becomes a target electrode terminal.

The target electrode 4 is manufactured in the following manner.

That is, referring to FIG. 3a = h, the N conductivity type silicon single crystal substrate 14 has a specific resistance of about 10 gcrIL, and is formed into a disk shape with a diameter of about 32 g and a thickness of about 15071 m. (Figure a).

After cleaning the substrate 14, it is heated in an oxygen atmosphere at a temperature of approximately 1,200°C, and at least one surface is thermally oxidized to a thickness of approximately 0.
．． 2 μm to 3 μm silicon oxide (5i02) film 5′
is formed uniformly (see figure b).

After that, a photoresist film is uniformly deposited on the silicon oxide film portion on the one side, and selective exposure and development are performed using a photomask to create a delicate pattern on the silicon oxide film portion. A matrix-like photoresist film 15 is formed (C in the same figure).

Next, the exposed region of the silicon oxide film is dissolved and removed using a mixed solution of hydrofluoric acid and ammonium hydrofluoride or another hydrofluoric acid-based etchant, and then the photoresist film 15 is dissolved and removed.

As a result, a delicate matrix-like silicon oxide film 5 matching the planar shape of the photoresist film 15 is formed on one surface of the silicon single crystal substrate 14 (d in the figure).
.

Next, after covering the other surface (bottom surface) of the substrate 14 other than the central region with a film or cover of a corrosion-resistant material, the substrate 14 is etched with an etchant having a high etching rate such as hydrofluoric nitric acid.
4 from the center area.

Due to this boring, the thickness in the central region of the substrate 14 is gradually reduced, but the residual thickness is approximately 4 μm to 10 μm.
When the etchant reaches m, the etchant is stopped (e in the same figure).

After removing the film or cover of the corrosion-resistant material, the entire surface of the target is etched at a low speed using an aqueous potassium hydroxide solution, an amine-based etchant, or the like.

As a result, the silicon portion in the central region of the substrate 14 is completely removed, and the silicon cylindrical portion 7 in the peripheral region G is removed.
(f) in the same figure.

Note that this two-step etching is performed on the substrate 1 in the process of thinning the film.
Although the mechanical strength of 4 is reduced, the membrane surface can be protected from damage, which is very advantageous in terms of yield.

An example of an amine-based etchant is ethyldiamine 17r.
ttl, pyrocatechol 39 and water 8 ml.

Incidentally, the matrix shapes of the photoresist film 15 and the silicon oxide film 5 are not limited to the lattice shape shown in the drawings, but may be porous with many pores evenly distributed and arranged.

The pitch P of the hole arrangement can be selected from a range of approximately 2 μm to 30 μm, and the width W can be selected to be approximately 0.2 to 0.6 times the pitch P.

Now, after boring, the silicon single crystal substrate 14 has only the cylindrical part 7, and the cylindrical part T has a delicate matrix-like silicon oxide film 5 stretched over one edge thereof.

Next, a metal such as chromium or a gold-chromium alloy is vacuum-deposited on the inner surface of the silicon oxide film 5 to a thickness of about 0.1
A matrix-like metal film 6 of .mu.m to 0.5 .mu.m is formed as a signal electrode (g in the same figure).

Note that if the metal film 60 is made of chromium or a gold-chromium alloy, the adhesion strength to the silicon oxide film 5 will be poor;
Favorable results are obtained.

However, metals other than chromium and its alloys, such as platinum or nickel, may be used as long as they are resistant to oxidation by residual gas in the tube and can be vacuum-deposited.

In addition, after vacuum-depositing the first layer of chromium, gold and
A second layer of chromium alloy etc. is applied to the first layer by vacuum deposition or metal transfer.
It may also be polymerized onto the layer.

Generally speaking, instead of forming a silicon oxide film on a silicon single crystal substrate, silicon nitride (81
3N4) may be formed in advance.

In the present invention, next, an annular second metal film 8 spanning the inner surface of the side wall of the cylindrical portion 7 and the peripheral part of the film surface of the central region is formed to a thickness of 0.05 μm to 1 μm by vacuum deposition.
Figure h).

As for the material of this second metal film 8, like the metal film 6,
Chromium, gold/chromium, platinum, nickel, or the like can be used, and its thickness is selected depending on the thickness of the membrane 5 and the hole pitch, and can be set to about 0.1 μm when the thickness is 0.5 μm and the hole pitch is 1107z.

The second metal film 8 formed by vacuum evaporation shrinks at an acute angle as shown in FIG. 4 as the temperature decreases to room temperature. The membrane 5 is pulled in a radial direction from its center to its periphery, and is tensioned uniformly over the membrane surface.

The second metal film 8 may be provided before the formation of the metal film 6, but
If the degree of tension is too strong, the membrane 5 may be damaged.

Further, the metal film 6 may be provided on the outer surface of the film 5 or the second metal film 8 may be provided on the outer surface side of the film 5. In these cases, the metal film 6 is connected to the metal through the annular metal plate 10 and the elastic conductor 11. Ring 9 is energized.

Furthermore, the second metal film 8 does not have to be completely annular;
It only needs to be substantially annular.

Since such a target electrode has a uniformly tensioned membrane surface, the membrane surface does not move during tube operation and is stable, and also has a good charge storage effect.

Signal writing is achieved by guiding a density-modulated or velocity-modulated electron beam emitted from the electron gun 2 onto the silicon oxide or silicon nitride film 5 and scanning the film surface.

The first crossover voltage in the secondary electron emission curve of the film 5 is about 25V to 30V, so after erasing with a voltage higher than this, the write target voltage (of the write electron gun) lower than the first crossover voltage is applied. When scanning is performed with the write-side mold beam while setting the potential of the signal electrode to the cathode, a charge image is accumulated on the film 5.

Further, when the write operation is set to a target voltage higher than the first crossover voltage, discharge occurs, and if writing is performed during discharging, erasing is performed during charging, and it can be used in either mode.

In addition, a so-called balance writing method in which the target voltage or cathode voltage is modulated according to the input signal can be applied.

The electric field caused by the written signal extends to the readout side through the pores of the target electrode and controls the readout beam.

Figures 5 to 9 show the results of computer analysis of this situation.
As shown in the figure.

However, here, the initial velocity variation distribution of the electron beam is ignored, and it is assumed that there is no effect of space charge.

Further, the readout target voltage is set to +7V, the broken line is an equipotential line, the arrow is a readout beam, and 16 indicates a pore.

As can be seen from these drawings, the readout electron beam flowing into the signal electrode 6 becomes a dog in the membrane region where the membrane surface potential is -10■ compared to the membrane region where the membrane surface potential is +2■. .

Then, by calculating the ratio of the number of electron beams flowing into the signal electrode 6 and the number of returning and passing electron beams, the beam transmittance characteristic is derived, as shown in FIG. 10.

The characteristic curve shown in FIG. 10 can be divided into 3° regions i, n, and m.

In region I, the readout electron beam passes through the target I quadrupole and heads toward the field mesh electrode on the write electron gun side, and in region ■, the readout electron beam is focused from the target electrode surface and is directed toward the readout electron gun. Region (3) is a state in which the readout electron beam returns to the readout electron gun side while receiving a diverging effect.

FIG. 11 shows the relationship between +t and output signal current on the read-out field mesh, and as is clear from the figure, a considerable dark current component is extracted from this tube.

However, since this dark current component has no temperature dependence and can be removed in the operating circuit, stable operation can be achieved.

Note that the dark current component changes by changing the area ratio of the pore group occupying the target electrode surface or by changing the magnitude of the beam current during readout.

Furthermore, as the window waveform is accumulated, Vs outside the black area is OV
, Vs of the white part is -13■), and the signal current is 400
FIG. 12 shows continuous readout time characteristics when readout at nA (of which the dark current component is 200 nA).

As can be seen from the figure, the continuous readout time of this tube is very long.

FIG. 13 shows the amplitude modulation characteristics when a sine wave input signal is written and read by parallel scanning with a scanning area of 9.5 mm x 12.7 mm and a writing speed of 0.3 seconds.

From this figure, it can be seen that although it is a small tube, it has high resolution characteristics.

Furthermore, since the signal electrode is formed using a vapor deposition method with good uniformity, and because it is made of a metal that is taut and easy for electron beams to land on, it is possible to obtain excellent sheating characteristics.

[Brief explanation of drawings]

Fig. 1 is a schematic side sectional view of a two-electron gun type scanning converter tube embodying the present invention, Fig. 2 is a side sectional view of a target electrode of the same scanning converter tube, and Figs. A diagram showing the manufacturing process, FIG. 4 is a cross-sectional view of the main part of the target electrode, and FIGS. 5 to 9 are diagrams showing the relationship between the target electrode potential distribution and the readout electron beam during readout of the scan conversion tube. , FIG. 10 is a characteristic diagram showing the relationship between the oxide film surface potential and output signal current of the same scanning conversion tube, FIG. 11 is a characteristic diagram showing the relationship between mesh electrode current and output signal current, and FIG. Similarly, FIG. 13 is a characteristic diagram showing the relationship between continuous readout time and relative output signal, and FIG. 13 is a characteristic diagram showing the relationship between frequency and amplitude modulation degree. 2... Electron gun for erasing written images, 3...
・Readout electron gun, 4...Target electrode,
5...Silicon oxide film, 6...Metal film, 9...Metal ring, 14...Silicon 16...
... Thin 8 ... Second metal film, Con single crystal substrate,

Claims (1)

[Claims] 1. A large number of pores are formed by selective etching in a silicon oxide or silicon nitride film formed on one surface of a silicon single crystal substrate, and then the central region of the silicon single crystal substrate is bored from the other surface. Then, the silicon portion in the central region is removed, and a first metal film as a signal electrode is deposited on one surface of the film stretched over the cylindrical silicon portion left in the peripheral region. In the method for manufacturing a target electrode, a substantially annular second metal film spanning the cylindrical portion and the peripheral portion of the central region is formed by vacuum deposition before or after the formation of the first metal film. and applying tension to the membrane.