JPH01186734A - Target of infrared vidicon and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve residual image characteristics by laminating a good landing layer on a target. CONSTITUTION:A PbO layer 103 with the surface side thereof covered by a PbS crystal layer substituted and reacted with sulphur is laminated on the transparent conductive film 102 of a face plate 101. Furthermore, an overcoat layer 100 composed of As2S3 and the like as a good landing material ensuring good scanning electron compared with the complex film 103 is laminated thereupon. According to the aforesaid construction, a landing is generated on the overcoat layer 109 and residual image characteristics can be improved depending upon the characteristics of the overcoat layer 109.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an infrared vidicon target and a method for manufacturing the same, such as cameras for dark surveillance, internal observation of semiconductors, confirmation of the beam position and shape of laser light, IC
and LSI silicon (SI) chip inspection and quality control,
Furthermore, it is used in fields such as process control such as temperature monitoring of electric furnaces and melting furnaces, monitoring of heat generating parts of engines and boilers, and detection of moisture adhesion and water absorption/desorption conditions using water adsorption that occurs in the 1.4 μm wavelength band. It will be done.

[Conventional technology]

FIG. 12 shows the structure of a conventional infrared vidicon near the target. The target is a S n O film called a Nesa film on a face plate 101 made of borosilicate glass.
A transparent conductive film 102 consisting of two layers is laminated to a thickness of about 1000 Å, and a pbo-PbS composite film 103 made of a high-resistance photoconductor is laminated on this transparent conductive film 102.

This target is connected to the cylindrical glass (borosilicate glass) that constitutes the tube of the infrared vidicon through the target ring 104 made of Kovar metal used for the signal electrode.
105 by glass fusion. In addition, 1 in the figure
Reference numerals 06 and 107 indicate a third grid and a mesh electrode constituting the electron gun.

The production of such an infrared vidicon target was carried out using the following procedure. First, the face plate 101 on which the transparent conductive film 102 is laminated is placed on the cylindrical glass 105.
Join by glass fusion. Next, a pbo-pbs composite film 103 is laminated using, for example, a vacuum evaporation method. Such a process produces CO when PbO is exposed to the atmosphere.
In order to prevent PbO from reacting with 2 or H2O and chemically changing into carbonate or hydroxide, the steps from the deposition of PbO to the lamination of the composite film 103 are performed in a glass cylinder 105 in a vacuum. It is characterized by the fact that it is made as follows.

[Problem to be solved by the invention]

However, the conventional infrared vidicon targets as described above have the following problems. first,
Regarding the afterimage characteristics, a 1-inch diameter visible image pickup tube is Sb2S.
30% for 3 targets, 20% for Cd Se target
, 20% for S1 target, 5% for PbO target,
While it is 2% for the Se-As-Te target (in both cases, the amount of residual signal charge after 50 m see after cutting off the incident light), the infrared vidicon has a significantly poor afterimage property of about 60%. The images obtained with infrared vidicon were originally considered satisfactory as long as they could be visualized because the infrared range was invisible to the naked eye, but with the development of image processing technology, the resolution and spectral sensitivity have become even higher. Clear image quality is now required in everything. However, the conventional infrared vidicon target described above has a problem in that it cannot meet this requirement.

In addition, in the conventional infrared vidicon target manufacturing method described above, since the photoconductor is laminated by vacuum deposition inside the cylindrical glass 105, it is difficult to control the uniformity of the film thickness. There were problems in that the sensitivity was uneven and the shading was large, reaching about 40%.

In addition to this, during glass fusing or vapor deposition, the transparent conductive film 1
02 and composite film 103 from the target to the cylindrical glass 105
(Fig. 12), the scanning electron (e'') toward the target surface has its trajectory disturbed as shown in the same figure, resulting in inaccurate landing, which is called Binkushion distortion. The problem has been that geometric distortion occurs, leading to a decline in image quality.

In addition, all operations after vapor deposition on the target surface must be performed in a vacuum, resulting in the problem that the apparatus for carrying out this process becomes large in size.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an infrared vidicon target that can improve various characteristics such as afterimage characteristics, resolution, and spectral sensitivity, and can obtain clearer image quality.

Furthermore, the present invention makes it possible to easily control the film thickness on the target surface, suppress shading, and more accurately land scanning electrons on the target surface, thereby reducing geometric distortions such as binkushion distortion. A second object of the present invention is to provide a method for manufacturing an infrared vidicon target, which allows for the miniaturization of an apparatus for carrying out the process.

[Means to solve the problem]

In the infrared vidicon target according to the present invention, a PbO layer whose surface side is covered with a PbS crystal layer subjected to a substitution reaction with sulfur (S) is laminated on a transparent conductive film of a face plate, and further on this PbS crystal layer. Additionally, an overcoat layer made of a material with good landing properties for scanning electrons is laminated thereon.

Furthermore, the method for manufacturing an infrared vidicon target according to the present invention includes forming a PbO layer on the transparent conductive film of the face plate on which the transparent conductive film is laminated, prior to bonding with the glass cylinder constituting the tube of the infrared vidicon. The first step of laminating and the substitution reaction with sulfur (S)
A second step of forming a PbS crystal layer on the surface of the O layer, and a third step of laminating an overcoat layer made of a good landing material for scanning electrons on the PbS crystal layer, and the first to third steps are performed. is characterized in that the PbO layer, the PbS layer, and the overcoat layer are laminated so that their respective peripheral edges recede from the peripheral edge of the transparent conductive film toward their respective centers.

[Effect]

Since the infrared vidicon target according to the present invention is configured as described above, scanning electrons land on the overcoat layer made of a good landing material, and are characterized by image retention characteristics depending on the characteristics of this overcoat layer. Characteristics can be improved.

Furthermore, since the method for manufacturing an infrared vidicon target according to the present invention is configured as described above, the surface of PbO is
In the process after laminating the photoconductor made of bS, PbO
Chemical changes in the film are prevented, and all processes can be performed without being in a vacuum, making it possible to easily perform preparations and inspections for controlling film thickness, deposition position, etc. in the atmosphere.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an infrared vidicon target and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS. 1 to 9 of the accompanying drawings.

FIG. 1 shows the configuration of an infrared vidicon near a target according to an embodiment of the present invention. In this figure, the same components as in FIG. 12 are given the same reference numerals, and their explanations will be omitted. Since the target of this example is obtained by the manufacturing method described later, although the peripheral edge of the transparent conductive film 102 is bonded to the indium (In) 108 used for the signal electrode, it does not adhere to the inner wall of the cylindrical glass 105. Not yet. Then, a good landing material that enables better landing of scanning electrons than this composite film 103 is placed on the pbo-pb s composite film 103 obtained by a substitution reaction of the surface side of PbO with sulfur (S). As, A S 2 S
An overcoat layer 109 of a is laminated.

Here, a good landing material is a material that acts as a transport layer and an accumulation layer for holes and electrons generated by light incident on the target, and that allows the scanning electrons from the electron gun to The material has a resistance value that facilitates better landing on the overcoat layer made of the material than the composite film. The peripheral edge of the overcoat layer 109 and the composite film 103 is formed by the transparent conductive film 10.
It is formed so that it may retreat from the peripheral edge of 2 toward the center of each. That is, the peripheral edges of the overcoat layer 109 and the composite film 103 are formed apart from the inner wall of the cylindrical glass 105. Moreover, the film thickness of the composite film 103 is 3μ
m, and the thickness of the overcoat layer 109 is 150 nm. Furthermore, the diameter of the target is 273 inches.

Other configurations are the same as before.

A typical example of the X-ray diffraction pattern of the above composite film 103 is shown in FIG. According to the figure, the pbo-PbS film is mostly composed of tetragonal PbO, with a trace amount of cubic PbO.
It was found that it contained bS. And tetragonal Pb
O has a large orientation toward the (110) plane, and pbs has a (110) orientation.
), those oriented toward the (200) plane were detected.

Next, a method for manufacturing the target of the above-mentioned infrared vidicon will be explained.

First, a face plate 10 with a diameter of 2/3 inch and a predetermined thickness is prepared.
1, a transparent conductive film 102 made of S n O2
are laminated using the CVD method to a predetermined thickness (approximately 1000 Å) with a diameter slightly shorter than 273 inches. Next, lead oxide (Pb 2 O) is deposited on this transparent conductive film 102 in a vacuum. In this case, the diameter is slightly smaller than the diameter of the transparent conductive film 102, and the film thickness is 3 μm. Next, PbO
Since PbO itself does not have infrared sensitivity, a very thin PbS crystal layer is formed on the surface of the PbO layer through a substitution reaction with sulfur (S), thereby imparting infrared sensitivity.

This manufacturing method is disclosed in the patent application filed in 1982-14 by the present applicant.
Since it was described in detail in No. 6439, an outline thereof will be explained here.

First, a borosilicate glass plate on which a transparent electrode of tin dioxide (SnO2) was formed was fixed in a vapor deposition chamber with an oxygen atmosphere of about 10 to 10 Torr, and a platinum crucible was placed in front of this transparent electrode. Then, place the lead (pb) in the vapor deposition chamber, and place sulfur (S) in the vapor deposition chamber.Next, when electricity is applied to the platinum crucible to heat the lead, the lead evaporates and PbO is deposited on the surface of the tin dioxide. At this time, when the borosilicate glass is heated to about 80 to 150℃ and the width of the borosilicate glass is g, the distance between the surface of the transparent electrode and the crucible is It should be about 1.5f1 to 3g.

If vapor deposition continues in this state, needle-shaped PbO crystals will grow on the surface of tin dioxide. The growth at this time is <1
10>Grows quickly in the direction of the axis, and since there is a transparent axis in the direction perpendicular to this, plate-shaped growth occurs, and when the root part hits another plate-shaped growth part, they separate from each other toward the tip side. Grows in the form of needles. After growing acicular crystals of lead oxide in this way, sulfur is evaporated and the deposition chamber is filled with the sulfur, and when it is fired at a low temperature for a long time, some of the oxygen in the acicular crystals of lead oxide is replaced with sulfur, and they mutually interact. A sufficient amount of PbS layer is formed on the surface of the needle crystal in the separated state. The photoconductor with the lead oxide-lead sulfide composite target structure formed in this way maintains the high specific resistance of lead oxide and has a sufficient layer of lead sulfide formed on the surface of the acicular crystals, so it can be used in the infrared region. It can be sensitive up to

In this way, a composite film 103 in which the surface of PbO is coated with PbS can be formed, and from this point on, since PbO is coated with PbS, even if the target is exposed to the atmosphere for about an hour, PbS will not oxidize. It never changes. Therefore, after the composite film 103 is laminated, the target is transferred to a vacuum evaporation apparatus, but exposure to the atmosphere at this time is not a problem. Then, the inside of this vacuum evaporation apparatus is kept in a vacuum, or an inert gas containing argon (Ar) is used.
-3 Torr atmosphere and As2S on the composite film 103.
3. Perform vapor deposition. The diameter of As283 is equal to that of the composite film 103, and the film thickness is 3 nm. As a result, the target shown in FIG. 1 is completed.

This target is joined by cold pressure welding to a cylindrical glass (integrated with an electrode sealed in a stem and an electron gun built in) 105 using an indium (In 2 ). At this time,
Since the diameter of the transparent conductive film 102 is slightly larger than the diameter of the composite film 103 and the overcoat layer 109 made of a good landing material, the bonding portion is only the transparent conductive layer 102 and the indium, and therefore the bonding can be easily achieved. become. Since the transparent conductive film 102, the composite film 103, and the overcoat layer 109 do not adhere to the inside of the glass cylinder 105, the electric field between the mesh electrode 107 and the target becomes uniform, and as shown in FIG. The locus of movement of the electron (e'') becomes perpendicular to the target surface, and landing is properly performed. Therefore, it is possible to obtain an image with less geometric distortion such as binkushion or barrel distortion. In addition, since the target can be manufactured separately from the cylindrical glass 105, it is possible to make the film thickness uniform between the center and the ends, and the sensitivity between the center and the ends can be made uniform. 30 shading
It can be suppressed to about %. In this embodiment, once the pbo-PbS composite film 103 is laminated, it is possible to observe the surface condition by microscopic observation in the air, and it is also possible to judge the quality of the product. .

The resolution of the signal electrode voltage characteristics, γ (gamma) characteristics, spectral sensitivity characteristics, and afterimage characteristics of the infrared vidicon target thus manufactured will be described below.

(1) Signal electrode voltage characteristics Figure 3 shows target voltage versus dark current and signal current characteristics. The solid line is for the conventional type (N1), and the broken line is for the present embodiment (N2). In this signal current measurement, a tungsten lamp was used for 2856, and light was irradiated through an infrared filter so that the illuminance on the vidicon surface was 10 Lx (lux). The values obtained at this time are shown in FIG. 3, where the signal current is obtained by subtracting the dark current. To explain the dark current characteristics in this case, the third
In the region where the target voltage is low in the figure, there is an ohmic region of ■oev with a slope of 45°. From this, the dark current is proportional to the thermally excited electron density, and its amount is P
This is thought to be largely due to the amount of bS. Furthermore, in a region where the target voltage is high, the dark current becomes a space charge limited current. On the other hand, in this high target voltage region, the dark current depends on the shallow amount of electron traps, and this trap amount is considered to be mainly caused by the traps in the PbO layer. As is clear from FIG. 3, the voltage dependence of this embodiment is lower than that of the conventional one.

(2) γ (Gamma) Characteristics FIG. 4 shows a measurement system for the γ characteristics of the infrared vidicon 1. A tungsten lamp 2856 is used as the light source 2, and the irradiated light is reflected by the reflective pattern 3 and guided to the infrared filter 4. Here, the reason why the reflective pattern is used is to prevent the filament of the light source 2 from appearing on the image since the photoconductive film is sensitive to infrared light when a transmissive pattern is used. The γ characteristics actually measured using this measurement system are shown in FIG. In this measurement, the dark current is 1
The target voltage was controlled to be 0 nA. N1 is the characteristic according to the conventional example, and N2 is the characteristic according to this embodiment. Both are straight lines, the slope of which is N1 is 0.5, and N
2 became 0.6, and γ became large. This is presumed to be because the overcoat film was laminated.

(3) Spectral sensitivity characteristics FIG. 6 shows the spectral sensitivity characteristics of the infrared vidicon of this example. In this measurement, a thermopile is used to calibrate each wavelength so that the energy incident on the photocathode is constant.
Furthermore, the measurement was performed when the dark current had stabilized, and the value obtained by subtracting the dark current from the signal current is shown. The incident energy is changed from 1 μW to 110 μW to 150 μW, but for example, at the same wavelength, the incident energy is changed from 1 μW to 1 μW.
The fact that the signal current does not increase 10 times even if the signal current is changed 10 times to 0 μW indicates that γ is not 1. Also, this sixth
From the figure, it can be seen that the target of the infrared vidicon of this example has sensitivity up to a wavelength of about 1.7 μm. Therefore, since the absorption edge of silicon (Sl) is in the wavelength band of 1.1 μm, when observing the inside of a semiconductor using this infrared vidicon having the target according to this example, the Sl substrate can be seen through as if it were transparent glass. This shows that it is possible to see inside and observe the inside. In addition, the absorption of water is at a wavelength of 1.4 μm.
Since this phenomenon occurs in bands, this shows that it can be used to determine where moisture is attached.

By the way, the band gap of PbS at 300@ is 0.37 eV. Theoretically, infrared sensitivity can be obtained up to about 3.3 μm, but PbS has a low resistance as a material that makes up the film of the image pickup tube.
If a large amount of PbS is mixed, the resolution will deteriorate. Therefore, in this example, a small amount of PbS is formed on the surface by the substitution treatment of PbO with sulfur (S), and because the amount of PbS is kept small, the spectral sensitivity is limited to the level shown in Figure 6. be.

(4) Afterimage Figure 7 shows the afterimage measurement system. As an optical system, an infrared filter shown in FIG. 4 with a diffuser plate provided on the light incident side was used. The shutter 12 is closed by the pulse generator 11, the output signal of the infrared vidicon 13 is guided to the tester 14 with a monitor, and the results are stored in the waveform memory 15 every other field.

Figure 8 shows the measurement results. The characteristics connecting the black circles are the current implementation N (N2), and the characteristics connecting the white circles are the conventional example (N1).
). Then, after 3 fields (about 3.5 seconds)
The value of was 36% in this example and 67% in the conventional example, indicating a significant improvement. It can be seen that in this embodiment, the afterimage decreases greatly where the number of fields is low, and a low afterimage level is reached quickly. This is considered to be because, in this example, the causes of operational changes such as a decrease in the dark current level and an increase in the γ value as described above caused the decrease in afterimages.

(5) Resolution Figure 9 shows the AR curve. In this AR measurement, the lens aperture was set to F8, the signal current was set to 200 nA, and an EIAJ-Bl chart was used. To adjust the light intensity, an ND filter manufactured by Toshiba Glass ■ was used. The AR value for 40 OTV lines was 5% for the conventional example and 14% for this example, which was a significant improvement.

Here, since the same electrode was used for the electron gun and the same camera with a band of 10 MHz was used for measurement, which is a factor that determines the quality of the resolution, the quality of the target film, that is, the presence or absence of the overcoat film 109, determines the quality of the resolution. is considered to be determined.

An application example will be shown in which an infrared vidicon to which the target according to the present embodiment is applied is used to observe the inside of a semiconductor through an infrared microscope.

Figure 10 is a diagram showing the observation method when observing the internal circuit of an IC, and Figure 11 shows the St chip and A chip of the internal circuit of the IC.
, Q is a diagram showing an observation method when observing a bonding layer with Q. In these figures, 21 represents a plastic mold, 22 represents a silicon substrate, and 25 represents an observation surface.

The photographing results by an infrared vidicon using a conventional target are described in "Television Society Technical Report" Vol. 11. published by the present inventor on November 20, 1986. No,
28. pp, 55-59. ED'87-831D'87
-108 (No'v, 1987), as shown in Fig. 12, and the photographing result by an infrared vidicon using the target of this example is as shown in Fig. 13 of the above-mentioned document.

In the conventional example, the state of the Al-81 eutectic alloy layer is unclear. In the case using this example, even the black dots in the alloy layer can be clearly seen. Furthermore, the outline of each pattern is also clear. Although Afi pattern disconnection has occurred in this photographed IC, this defect can be discovered at a glance in the type according to this embodiment, which has improved resolution.

On the other hand, the die bonding portion imaged by the method shown in FIG. 11 is as shown in FIG. 15 of the above-mentioned document. From this figure, you can see the state of the eutectic alloy layer at the interface,
It is believed that this method can be an effective testing method for power devices and the like.

The infrared vidicon target and the manufacturing method thereof according to the present invention are not limited to the above embodiments.

For example, As283 is used as the above-mentioned good landing material.
A resistor was used, which acts as a transport layer and an accumulation layer for holes and electrons generated by light incidence, and also makes it easier for scanning electrons (from an electron gun) to land well than in a composite film. If it has a value, Sb2S
3. It may be a single layer such as A S 2 S e 2, or (
A double layer such as As S e a + As 2 S a ) may also be used. When adopting this double layer structure, a single layer has approximately 1
Vacuum deposited layers of about 0.000A are laminated to form a denser film to prevent chemical changes from entering the PbO polycrystal, and then heated to 10-3T in an inert gas.
It is also possible to form a double layer by laminating porous films of 500 to 800 A by vapor deposition in an atmosphere of about 100 Å or more. In addition, when laminating this double layer, AsSe2 is used for the single layer,
After vacuum deposition, heat treatment is performed at 120°C to 300°C.
Thereafter, it may be transferred to a vacuum evaporation apparatus to evaporate As282. If this is done, some PbS will become Pb5 during heat treatment.
It is thought that a chemical reaction occurs with e, and the spectral sensitivity was improved to 2.7 μm by improving the infrared sensitivity. Further, the film thickness and diameter may be other values.

〔Effect of the invention〕

As explained above in detail, in the present invention, since a good landing layer is laminated on the target, the mobility and accumulation of holes in the holes and electrons generated from the PbS layer, which is an infrared sensitive layer, is improved. , the capacitance of the target and the time constant are reduced, and therefore the afterimage characteristics (at the time of 3 fills and delay) can be significantly improved. Also, for the same reason, there is an effect that the /F resolution is greatly improved.

Furthermore, in the target manufacturing method of the present invention, a PbS layer and an overcoat layer that protects PbO from air are laminated before bonding with the cylindrical glass that becomes the tube of the infrared vidicon, so that PbO does not undergo chemical changes. Therefore, the process can be performed in the atmosphere. In other words, the target only needs to be in vacuum while the PbO is exposed, and since it is separated from the cylindrical glass, it is easier to stack the transparent conductive film, and the composite film and overcoat layer can be inspected with a microscope. This makes it possible to accurately judge whether a product is good or bad. Also, for the same reason, the film thickness, evaporation distance, degree of vacuum, 0
゜Vapor deposition conditions such as flow rate can be controlled easily and accurately, and targets of the same quality can be obtained. In addition, the overcoat layer of the transparent conductive film, composite film, or good landing material is not attached to the inner wall of the cylindrical glass, and the scanning electrons are prevented from landing in a disordered manner. The electric field becomes uniform, and images with less geometric distortion such as binkushion distortion can be obtained.

Furthermore, since the film thickness can be made uniform between the center and the edges, the sensitivity can be made uniform, which also has the effect of reducing shading.

Furthermore, the peripheral edges of the overcoat layers of the pbo layer and the PbS layer are laminated so that they recede from the peripheral edge of the transparent conductive film toward the center of each layer, and the PbO layer is covered with a PbS layer or the like. Cold pressure welding using indium (In 2 ) can be used to bond the cylindrical glass and the target, which is simple yet effective in forming electrodes accurately.

Further, it is not necessary to perform the process continuously in a vacuum, and the effect is that it becomes possible to downsize the apparatus for performing the process.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of an infrared vidicon target according to an embodiment of the present invention, FIG. 2 is a diagram showing an X-ray diffraction pattern of a composite film used in an embodiment of the present invention, and FIG. ,
Figures 5, 6, 8, and 9 are diagrams showing the signal electrode V-1 characteristics, γ characteristics, spectral sensitivity characteristics, afterimage characteristics, and resolution, respectively, of an infrared vidicon using the target of this example. , Figure 4 is a block diagram of the gamma characteristic measurement system, Figure 7 is a block diagram of the afterimage characteristic, Figures 10 and 11 are diagrams for explaining the IC observation method using an infrared vidicon,
FIG. 12 is a sectional view showing the structure of a conventional infrared vidicon target. 101... Face plate, 102... Transparent conductive film, 103... Composite film, 105... Cylindrical glass, 1
06...Third grid, 107...Mesh electrode, 108
... Indium, 109... Overcoat layer. Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent Attorney
Yoshiki Hase Figure 1 Figure 2 Vi (V) V-I characteristics Figure 3 r Measurement system Figure 1 (LUMINOUS INTENSITY) No fill "Characteristics 8001αχ), 1200 140016001800
2000 wavelength (nm) Spectral sensitivity characteristics Figure 6 TV book AR curve Figure 9 LAG (@/・) Six observation directions Figure 10 Figure 11 Conventional example Figure 12

Claims (1)

[Claims] 1. A PbO layer whose surface side is covered with a PbS crystal layer subjected to a substitution reaction with sulfur (S) is laminated on the transparent conductive film of the face plate on which the transparent conductive film is laminated, Further, on this PbS crystal layer, an overcoat layer made of a good landing material for scanning electrons is laminated to form an infrared vidicon target. 2. A first step of laminating a PbO layer on the transparent conductive film of the face plate on which the transparent conductive film is laminated, and
PbS is formed on the surface of the PbO layer by a substitution reaction with S).
After the second step of forming a crystal layer and the third step of laminating an overcoat layer made of a good landing material for scanning electrons on this PbS crystal layer, the infrared vidicon is bonded to the glass cylinder constituting the tube. , and in the first to third steps, the PbO layer, the PbS layer, and the overcoat layer are laminated so that their peripheral edges recede from the peripheral edge of the transparent conductive film toward their respective central portions. Features: Target manufacturing method for infrared vidicon.