JP4457513B2 - X-ray generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention relates to an X-ray non-destructive inspection, X-ray analysis, an industrial X-ray apparatus for taking an X-ray photograph by enlarging the internal structure of an LSI, and an X-ray photograph of a cell for LSI product inspection, etc. The present invention relates to an X-ray generation device used in such an X-ray device.
[0002]
[Prior art]
Conventionally, X-rays generator, as shown in FIG. 9, the pipe main body 3 in which the internal vacuum, a cathode 4 which is arranged inside of the tube body 3, blanking lock shape formed in a mortar shape The Wehnelt electrode 5, a target T that irradiates an electron beam generated from the cathode 4 when energized to generate X-rays, and a magnetic lens 7 that converges the electron beam toward the target T.
[0003]
Further, the Wehnelt electrode 5 is maintained at a negative potential with respect to the cathode 4, and the electron beam generated from the cathode 4 when energized is output to a certain extent.
[0004]
[Problems to be solved by the invention]
However, the conventional example having such a configuration has the following problems.
That is, the conventional apparatus, as shown in FIG. 9, the Wehnelt electrode 5 is a block-like, compared to the cathode 4, the heat capacity increases. In other words, an extreme temperature difference occurs between the temperature of the cathode 4 when energized and the temperature of the Wehnelt electrode 5 that has risen due to the radiant heat generated from the cathode 4.
[0005]
Further, although the inside of the tube body 3 is in a vacuum state, there is a trace amount of volatile matter such as carbon that is a residue and oxide that is generated when the cathode 4 is worn when electrons are generated. Therefore, it tends to adhere to an object having a lower temperature than the cathode 4 existing near the cathode 4. That is, it adheres to the end portion of the Wehnelt electrode 5 existing in the vicinity of the cathode 4. As a result, the potential difference between the cathode 4 and the Wehnelt electrode 5 is different from the set condition, and the output electron beam cannot be taken out stably. And there is a problem that X-rays cannot be output accurately and stably in the end.
[0006]
The present invention has been made in view of such circumstances, and a main object of the present invention is to provide an X-ray generator that suppresses adhesion of an insulator to a Wehnelt electrode and generates X-rays stably and efficiently. And
[0007]
[Means for Solving the Problems]
In order to achieve such an object, the present invention has the following configuration.
That is, the invention described in claim 1 is a tube main body whose inside is evacuated, an electron source that generates an electron beam in the tube main body, and an electron beam generated from the electron source to irradiate X-rays. In the X-ray generator including the target to be generated, the electron source is (a) a cathode that generates electrons when energized, and (b) a surface of the cylindrical support portion from the target side toward the cathode. And a Wehnelt electrode formed in a mortar shape by a flat plate so that the width of the opening through which the electron beam passes is reduced. It is what has become .
[0009]
According to a second aspect of the present invention, there is provided a tube body whose inside is evacuated, an electron source for generating an electron beam in the tube body, and irradiating the electron beam generated from the electron source to emit X-rays. In the X-ray generator including the target to be generated, the electron source includes: (a) a cathode that generates electrons when energized; and (d) a surface of the cylindrical support portion on the target side toward the cathode tip. A Wehnelt formed in a bowl shape is formed by horizontally extending the flat plate and providing an opening through which the electron beam passes at the cathode, and further refracting the flat plate in a direction in which the opening expands obliquely in the electron beam output direction. (E) The thickness of the mortar-shaped cathode side tip of the Wehnelt electrode is set in the range of 100 to 500 μm.
[0010]
Furthermore, the invention described in claim 3 is the X-ray generator according to claim 1, wherein ( f ) the thickness of the Wehnelt electrode is set in a range of 100 to 500 μm.
[0011]
[Action]
The operation of the first aspect of the invention is as follows.
That is, the invention according to claim 1 is a Wehnelt formed in a mortar shape by a flat plate so that the width of an opening through which an electron beam passes becomes narrower from the surface on the target side of the cylindrical support portion toward the cathode. It has an electrode . That is, the Wehnelt electrode is radiated heat generated from the cathode when energized, and is immediately raised to substantially the same temperature as the cathode. As a result, adhesion of an insulator such as carbon to the Wehnelt electrode is suppressed, and an extreme potential difference between the cathode and the Wehnelt electrode is avoided. Further, since the Wehnelt electrode becomes thinner toward the cathode, it is immediately raised to substantially the same temperature as the cathode by the radiant heat from the cathode. In other words. The potential difference between the cathode and the Wehnelt electrode is suppressed.
[0013]
According to the second aspect of the present invention , the flat plate extends horizontally from the target-side surface of the cylindrical support portion toward the cathode tip, and an opening through which the electron beam passes is provided at the cathode portion. The plate is refracted in the direction in which the opening expands obliquely in the beam output direction. It has a Wehnelt electrode formed in a mortar shape, and the thickness of the mortar-shaped cathode side tip of the Wehnelt electrode is set in the range of 100 to 500 μm. Yes. That is, the Wehnelt electrode is radiated heat generated from the cathode when energized, and is immediately raised to substantially the same temperature as the cathode. As a result, adhesion of an insulator such as carbon to the Wehnelt electrode is suppressed, and an extreme potential difference between the cathode and the Wehnelt electrode is avoided.
[0014]
According to the invention described in claim 3 , by using the Wehnelt electrode whose thickness is set in the range of 100 to 500 μm, an extreme potential difference caused by the difference in heat capacity between the cathode and the Wehnelt electrode is avoided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
<First embodiment>
Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the overall configuration of the X-ray generator of the present invention, FIG. 2 is a longitudinal sectional view showing an electron source that is the main configuration of the X-ray generator of this embodiment, and FIG. 3 is a plan view of the electron source. FIG. 4 and FIG. 4 are schematic views showing the positional relationship between the cathode and the Wehnelt electrode.
[0016]
As shown in FIG. 1, the X-ray generator of this embodiment includes an X-ray generator 1 that generates X-rays in order from the X-ray output side, and a vacuum exhaust unit that places the inside of the X-ray generator 1 in a vacuum state. 8, a high-voltage power supply unit 9 that supplies a tube voltage / tube current to the X-ray generation unit 1, a control unit 10 that controls each unit, and information such as setting conditions for causing the control unit 10 to generate X-rays A computer 11 that is connected to the computer 11 and includes a keyboard 12 that is used for inputting X-ray output condition settings, etc., and a monitor 13 that displays the input setting conditions and the status of the entire apparatus. It has. Hereinafter, the configuration and function of each unit will be specifically described.
[0017]
First, an X-ray generator 1 having an electron source 2 having a characteristic configuration of the apparatus of this embodiment will be described.
As shown in FIG. 2, the X-ray generator 1 includes an electron source including a tube body 3 whose inside can be evacuated, a cathode 4, and a Wehnelt electrode 5 that narrows electrons generated from the cathode 4 into a beam shape. 2 and a magnetic field lens unit 7 for further converging the electron beam so as to irradiate an electron beam output from the electron source 2 to a target in the subsequent stage.
[0018]
The tube body 3 has a cylindrical shape made of stainless steel or the like, and is provided with an X-ray output window at an end portion in the longitudinal direction, although not shown. In addition, an opening / closing part is provided on the side thereof, and maintenance such as replacement of the cathode 4 can be performed.
[0019]
The cathode 4 is detachably attached to the high voltage connector insulator 6. As a material of the cathode 4, LaB ₆ (lanthanum hexaboride) is used. The material of the cathode 4 is not limited to LaB ₆ and may be tungsten, for example.
[0020]
The Wehnelt electrode 5 is made of stainless steel. Further, as shown in FIGS. 2 and 3, it is formed in a mortar shape (hereinafter referred to as “taper shape” as appropriate) that becomes tapered from the periphery of the support portion of the Wehnelt electrode 5 toward the cathode. In addition, an opening d is provided on the leading end side of the tapered portion so that electrons generated from the cathode 4 pass in a beam shape. Further, the inclination angle θ of the tapered Wehnelt electrode 5 forms an opening of 60 ° on the left and right with respect to the vertical central axis Y shown in the drawing, that is, 120 ° in the electron beam output direction. .
[0021]
That is, the Wehnelt electrode 5 is maintained at a negative potential of about several kV with respect to the cathode 4, and controls the beam current and narrows down the diameter of the electron beam passing through the opening d. .
[0022]
The material of the Wehnelt electrode 5 is not limited to stainless steel, and examples thereof include tungsten, tantalum, and molybdenum. In this embodiment, the inclination angle θ of the Wehnelt electrode is 120 °, but it is not limited to 120 °.
[0023]
Moreover, although the thickness H of the Wehnelt electrode 5 changes with materials to be used, it is preferable to set to 100-500 micrometers from the support part shown to L of FIG. 2 to the front-end | tip of a cathode direction. More preferably, it is the range of 100-200 micrometers.
[0024]
That is, if the thickness H of the Wehnelt electrode 5 is less than 100 μm, the thickness becomes too thin and a discharge phenomenon occurs between the tip of the Wehnelt electrode 5 and the cathode 4.
[0025]
On the contrary, if the thickness H of the Wehnelt electrode 5 exceeds 500 μm, an extreme temperature difference between the temperature of the Wehnelt cathode 5 rising due to radiant heat when electrons are generated from the cathode 4 and the temperature of the cathode 4. Occurs. Then, a transpiration substance such as carbon existing in a minute amount in the tube body 3 adheres to the tip of the Wehnelt electrode 5 as an insulator. As a result, a potential difference greater than the setting occurs between the cathode 4 and the Wehnelt electrode 5.
[0026]
Further, as shown in FIG. 4, the disposition relationship between the cathode 4 and the Wehnelt electrode 5 is such that a virtual line extending the Wehnelt electrode 5 in the cathode direction intersects the tip of the cathode 4. Such mutual arrangement allows electrons generated from the cathode 4 to efficiently pass through the opening d of the Wehnelt electrode 5. In addition, in the case of this Example apparatus, although the opening part d is set to the range of 0.5-1.0 mm, it is not limited to this range.
[0027]
Next, the magnetic lens unit 7 has the same structure as that shown in FIG. 9, and includes a magnetic lens 7 a and a target T.
In the magnetic lens 7a, a coil C is provided inside a cylindrical side wall made of pure iron, and a gap K is provided on the tip side (electron beam output side) of the central space portion of the cylinder. That is, the magnetic force generated when a current is passed through the coil C is concentrated in the gap K portion of the pure iron, and the magnetic force is changed by adjusting the current level so that the electron beam converges at a predetermined position. Adjusted.
[0028]
A target T is disposed after the magnetic lens 7a, and X-rays are generated by irradiating the target T with an electron beam.
[0029]
The target T may be a flat plate made of tungsten or a column. In particular, the cylindrical shape can be rotated with reference to the central axis in the longitudinal direction, and can be slid to the left and right in the longitudinal direction. That is, when the irradiated portion is worn by the electron beam irradiation, the electron beam irradiation portion can be easily changed.
[0030]
That is, in the case of this embodiment apparatus, the magnetic lens unit 7 may be either a transmission type or a reflection type.
[0031]
The vacuum exhaust part 8 is for making the inside of the pipe body 3 into a vacuum state. That is, when performing maintenance such as replacing the cathode 4 of the X-ray generator 1, the inside of the tube body 3 is temporarily returned to the atmospheric state, and after the cathode 4 is replaced, it is again returned to the vacuum state.
[0032]
The high voltage power supply unit 9 supplies the tube voltage / tube current to the X-ray generation unit 1 in accordance with the pulse signal sent from the control unit 10 based on the tube voltage / tube current information set on the console 13. It is like that. The state of the tube voltage and tube current on the X-ray generation unit 1 side at the time of X-ray generation is fed back to the high-voltage power supply unit 9 and is monitored successively by a transformer (not shown). In other words, the tube voltage and tube current of the set conditions are kept constant.
[0033]
The control unit 10 comprehensively controls each of the X-ray generation unit 1, the vacuum exhaust unit 8, and the high-voltage power supply unit 9 based on information input and set from the console 13.
[0034]
Next, the operation of the X-ray generator having the above configuration will be described.
The operator inputs conditions such as tube voltage and tube current according to the output X-ray level from the console 13. Based on this input information, the control unit 10 sends a pulse signal to the high voltage power supply unit 9, and supplies the tube voltage / tube current from the high voltage power supply unit 9 to the X-ray generation unit 1. At this time, the control unit 10 also comprehensively controls other components.
[0035]
In the X-ray generator 1 to which the tube voltage / tube current is supplied, electrons are generated from the cathode 4. The generated electrons are narrowed down according to the strength of the magnetic field generated by the potential difference between the cathode 4 and the Wehnelt electrode 5 when passing through the opening d of the Wehnelt electrode 5, and become an electron beam toward the magnetic field lens unit 7. Is output.
[0036]
Then, the output electron beam is further converged by the magnetic lens and irradiated onto the target. Then, X-rays are output from the target irradiated with the electron beam.
[0037]
According to the X-ray generator of the embodiment described above, the temperature difference between the cathode 4 and the Wehnelt electrode 5 when generating electrons is suppressed by reducing the thickness of the Wehnelt electrode 5 and reducing the heat capacity. Is done. That is, the Wehnelt electrode 5 that has received the radiant heat of the cathode 4 when generating electrons immediately rises to substantially the same temperature as the cathode 4, so that an insulator such as carbon that is present inside the tube body 3 is replaced by the tip of the Wehnelt electrode. Does not adhere to parts. As a result, the electron source 2 can accurately and stably output an electron beam according to the set conditions, and the X-ray generator 1 can accurately and stably output a predetermined X-ray by using this electron beam. Can be output.
[0038]
<Second embodiment>
Next, an X-ray generator according to the second embodiment will be described.
In this embodiment apparatus, since the configuration other than the X-ray generation unit is the same as that of the first embodiment, the same portions are only given the same reference numerals and the description thereof is omitted.
FIG. 5 is a longitudinal sectional view of an electron source which is a main part of the X-ray generator of the second embodiment.
[0039]
The electron source 2 includes a cathode 4 and a flat Wehnelt electrode 5 formed in a taper shape from the periphery of the support portion toward the cathode. The tapered inclination angle θ of the Wehnelt electrode 5 is 120 ° from the cathode 4 side toward the electron beam output side as shown in FIG.
[0040]
The thickness of the Wehnelt electrode 5 is formed such that the thickness gradually decreases from 200 (support side) to 100 (tip side) μm, for example, from the support side toward the tip on the cathode side. In other words, the Wehnelt electrode 5 increases the structural strength by increasing the thickness on the support portion side, and the thickness of the limit at which no discharge is generated between the tip of the Wehnelt electrode 5 and the cathode 4 is maintained. ing.
[0041]
By forming the Wehnelt electrode 5 as described above, adhesion of an insulator to the tip of the Wehnelt electrode 5 is suppressed, and an electron beam corresponding to the set condition can be output from the electron source 2 accurately and stably. As a result, the X-ray generator 1 can output X-rays accurately and stably.
[0042]
<Third embodiment>
Next, an X-ray generator according to the third embodiment will be described.
In the apparatus of this embodiment, the configuration other than the Wehnelt electrode of the X-ray generator is the same as that of the first and second embodiments, so that the same parts are only given the same reference numerals and the description thereof is omitted. To do.
FIG. 6 is a longitudinal sectional view of an electron source which is a main part of the X-ray generator of the third embodiment.
[0043]
The Wehnelt electrode 5 has a mortar shape formed in a flat plate shape, and the inside is hollow. That is, as shown in FIG. 6, the Wehnelt electrode 5 extends in the horizontal direction from the support portion to the tip of the cathode 4 and is provided with an opening d for outputting an electron beam at the cathode 4 portion, so that the electron beam output direction is oblique. Is refracted. And the S part shown in FIG. 6 is hollow.
[0044]
The refraction (inclination angle θ) of the Wehnelt electrode 5 is such that an opening of 60 ° to the left and right, that is, 120 ° in the electron beam output direction, is formed with reference to the cathode central axis Y.
[0045]
In this embodiment, the thickness H of the cathode side tip of the Wehnelt electrode 5 may be set in the range of 100 to 500 μm.
[0046]
The present invention is not limited to the embodiment described above, and can be modified as follows.
(1) In the above embodiment, the plate-shaped Wehnelt electrode 5 is used, but is not limited to a flat plate shape, and no discharge occurs between the cathode 4 and the Wehnelt electrode 5, and the temperature difference between them Therefore, it is sufficient that the insulating material adheres to the Wehnelt electrode and a different potential difference does not occur. For example, as shown in FIG. 7, to the tip of the Wehnelt electrode may be of a ring shape, may be of block-like shape shown in Figure 8. However, in order to satisfy the above-described conditions, it is preferable to set the thickness of the tip portion in FIGS. 7 and 8 within a range of 100 to 500 μm.
[0047]
(2) In the above embodiment, the magnetic lens is provided. However, the present invention is not limited to the magnetic lens, and may be a condenser such as a condenser lens.
[0048]
(3) In the first embodiment, the X-ray generator is described as an open type capable of maintaining the inside of the tube body 3, but is not limited to the open type.
[0049]
【The invention's effect】
As is apparent from the above description, according to the first aspect of the invention, the width of the opening through which the electron beam passes becomes narrower from the surface on the target side of the cylindrical support portion toward the cathode. A Wehnelt electrode formed in a mortar shape by a flat plate is provided , and the thickness decreases toward the cathode. For this reason, the heat capacities of the cathode and the Wehnelt electrode are made substantially the same. That is, the temperature difference between the cathode and the Wehnelt electrode is suppressed, and adhesion of an insulator to the Wehnelt electrode can be avoided. As a result, the electron source does not generate a different potential difference between the cathode and the Wehnelt electrode, so that the output of the electron beam can be stably and efficiently performed, and the X-ray generator can accurately generate X-rays according to the set conditions. In addition, stable output can be achieved.
[0050]
According to the invention described in claim 2, the flat plate extends horizontally in the cathode tip direction from the target-side surface of the cylindrical support portion, and an opening through which the electron beam passes at the cathode portion is provided, In addition, a flat plate is refracted in the direction in which the opening expands obliquely in the electron beam output direction. Is set. For this reason, the heat capacities of the cathode and the Wehnelt electrode are made substantially the same. That is, the temperature difference between the cathode and the Wehnelt electrode is suppressed, and adhesion of an insulator to the Wehnelt electrode can be avoided. As a result, the electron source does not generate a different potential difference between the cathode and the Wehnelt electrode, so that the output of the electron beam can be stably and efficiently performed, and the X-ray generator can accurately generate X-rays according to the set conditions. In addition, stable output can be achieved. The thickness according to the invention described in claim 3 with the use of the c Eneruto electrode which is set in a range of 100 to 500 [mu] m, the heat capacity of the cathode and Wehnelt electrode are substantially the same. That is, the potential difference due to the influence of the temperature difference between the cathode and the Wehnelt electrode is suppressed, and adhesion of an insulator to the Wehnelt electrode is avoided. As a result, the X-ray generator can output X-rays according to the set conditions accurately and stably.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the overall configuration of a first embodiment according to the X-ray generator of the present invention.
FIG. 2 is a longitudinal sectional view showing the main configuration of the first embodiment.
FIG. 3 is a front view of the electron source of the first embodiment.
FIG. 4 is a schematic diagram showing the positional relationship between the cathode and the Wehnelt electrode in the first embodiment.
FIG. 5 is a longitudinal sectional view of an essential part of the X-ray generator of the second embodiment apparatus.
FIG. 6 is a longitudinal sectional view of an essential part of the X-ray generator of the third embodiment apparatus.
FIG. 7 is a longitudinal sectional view showing an essential part of a modification according to the X-ray generator of the present invention.
FIG. 8 is a longitudinal sectional view showing an essential part of a modification according to the X-ray generator of the present invention.
FIG. 9 is a diagram showing a configuration of a main part of a conventional X-ray generator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... X-ray generation part 2 ... Electron source 3 ... Tube main body 4 ... Cathode 5 ... Wehnelt electrode 7 ... Electric field lens part 8 ... Vacuum exhaust part 9 ... High voltage power supply part 10 ... Control part 11 ... Computer

Claims (3)

An X-ray generator comprising: a tube body whose inside is evacuated; an electron source that generates an electron beam in the tube body; and a target that irradiates an electron beam generated from the electron source to generate X-rays The electron source includes: (a) a cathode that generates electrons when energized; and (b) a width of an opening through which an electron beam passes from the surface on the target side of the cylindrical support portion toward the cathode. A Wehnelt electrode formed in a mortar shape by a flat plate so as to be narrow, and (c) the Wehnelt electrode has a thickness that decreases from the support part toward the cathode. apparatus. An X-ray generator comprising: a tube body whose inside is evacuated; an electron source that generates an electron beam in the tube body; and a target that irradiates an electron beam generated from the electron source to generate X-rays The electron source includes: (a) a cathode that generates electrons when energized; (d) a flat plate extending horizontally from the surface on the target side of the cylindrical support portion toward the cathode tip; and the cathode And (e) the Wehnelt electrode provided with a Wehnelt electrode formed in a mortar shape in which an opening through which the electron beam passes is provided and a flat plate is refracted in a direction in which the opening is expanded obliquely in the electron beam output direction. The mortar-shaped cathode side tip has a thickness in the range of 100 to 500 μm . 2. The X-ray generator according to claim 1, wherein ( f ) the Wehnelt electrode has a thickness in a range of 100 to 500 μm.

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