JP2004325238A - Charge quantity measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charge quantity measuring device which measures the charge quantity appearing by being induced by an electric field without preparing a sample. <P>SOLUTION: A metal plate 70 having a prescribed capacity is mounted through an insulator 60 on a casing 10 composing a device body. A surface electrometer 20, an operation part 30 or the like are stored in the casing 10, and the surface electrometer 20 is arranged so as to face to the metal plate 70. When the metal plate 70 is exposed to an external electric field, the charge is induced on the metal plate 70 by the electric field, and the electric potential of the metal plate 70 is stabilized at the electric potential corresponding to the charge quantity. The electric potential is measured by the surface electrometer 20, and the charge quantity is operated from the measured value by the operation part 30. A shielding part 80 is mounted slidably on the casing 10, and the external electric field exerting an influence on the electric potential of the metal plate 70 is shielded when initializing the electric potential of the metal plate 70. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a charge measuring apparatus for measuring a charge of a sample such as a semiconductor device, and more particularly to a technique for measuring a charge induced in a sample placed in an electric field.
[0002]
[Prior art]
With the miniaturization of the device structure, the resistance of semiconductor devices to static electricity has been reduced, and measures against static electricity have become even more important. Conventionally, as a destruction mode due to static electricity, a mode in which electric charges charged on a human body or the like are directly discharged to a lead electrode of a device, and a mode in which electric charges induced in a lead terminal are discharged by charging a semiconductor device package. Are known. The static electricity that causes these breakdown modes is directly charged on the semiconductor device. On the other hand, in recent years, various types of electronic devices have been arranged at semiconductor device manufacturing sites, and electric charges induced in the semiconductor devices by electric fields generated by these electronic devices cause damage to the semiconductor devices. It has been attracting attention as one.
[0003]
Here, a supplementary explanation of the generation mechanism of the charges induced in the semiconductor device described above will be given. When a semiconductor device that is in an electrically neutral state in an initial state is brought close to a charged object (for example, a CRT), charges are induced in the semiconductor device by the action of an electric field formed by the charged charges on the object. A potential is generated in the device. When the lead terminal of the semiconductor device is short-circuited to the ground in this state, the charge induced in the semiconductor device is discharged, and a current corresponding to the amount of the charge flows between the semiconductor device and the ground, thereby damaging the semiconductor device.
As a technique for measuring this kind of charge amount, a technique disclosed in Japanese Patent Application Laid-Open No. 7-325119 is known. In this conventional technique, one electrode of a capacitor having a known capacitance value is grounded, and the other electrode is brought into contact with an object to be measured. Then, the charge amount (Q = CV) is calculated from the voltage value (V) between the terminals of the capacitor and the capacitance value (C) at that time (see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-7-325119 (paragraph number 0030, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, according to the above-mentioned prior art for measuring the amount of electric charge induced in a semiconductor device, a sample of the semiconductor device from which electric charge is induced must be prepared. Therefore, there is a problem that the charge amount cannot be measured unless a sample of the semiconductor device is prepared, and the influence of the electric field in which the semiconductor device is placed cannot be evaluated.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a charge amount measuring device capable of measuring a charge amount induced by an electric field without preparing a sample.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configurations.
That is, the charge amount measuring device according to the present invention is a charge amount measuring device for measuring a charge amount induced by an electric field, and is attached to the device main body via an insulator, and has a metal member having a predetermined capacity. A surface voltmeter provided on the apparatus main body so as to face the metal member, and measuring a surface potential of the metal member.
[0008]
In the above-mentioned charge amount measuring device, a switch for initializing the metal member to a predetermined potential is further provided.
The above-mentioned charge amount measuring apparatus is characterized in that it further comprises a shielding member for shielding an electric field which affects the potential of the metal member when the metal member is initialized to a predetermined potential.
The charge amount measurement device further includes a calculation unit that calculates a charge amount from a predetermined capacity of the metal member and a potential measured by the surface voltmeter, and a display unit that displays a calculation result of the calculation unit. It is characterized by having.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The charge amount measuring apparatus according to this embodiment measures the amount of charge induced by an electric field existing in an environment where a semiconductor device is placed, and is guided to the semiconductor device by the action of the electric field. This is for evaluating the amount of brazing charge. Therefore, this charge amount measuring apparatus does not directly measure the amount of charge on the semiconductor device, but observes the electric field itself in the environment where the semiconductor device is placed, thereby receiving the effect of the electric field. Thus, it can be said that the amount of charge that would be induced in the semiconductor device is indirectly measured.
[0010]
FIG. 1A shows a cross-sectional structure of the charge amount measuring device according to this embodiment. As shown in the figure, a casing 10, a surface voltmeter 20, a computing unit 30, a battery 40, a display unit 50, an insulator 60, a metal plate (metal member) 70, a shielding unit, which constitute a substantially cylindrical device main body. 80 and a switch 90. Here, the surface voltmeter 20, the operation unit 30, and the battery 40 are housed in this order along the central axis of the housing 10, and the display unit 50 and the switch 90 are provided. This switch 90 is for initializing the potential of the metal plate 70 to the ground potential (predetermined potential).
[0011]
A metal plate 70 is fixed to one end of the housing 10 via an insulator 60. The metal plate 70 has a predetermined capacity Cp. The metal plate 70 simulates a semiconductor device subjected to the above-described electric field, and has a shape corresponding to the semiconductor device. In this embodiment, the metal plate 70 is fixed to the metal plate 70 via the insulator 60. However, the metal plate 70 may be replaced with an appropriate one according to the shape of the semiconductor device to be subjected to the action of the electric field. The surface voltmeter 20 is provided on the housing 10 which is the apparatus main body so as to face the metal plate 70 described above. As the surface electrometer 20, a known one can be used. The output signal of the surface voltmeter 20 is input to the calculation unit 30, and the output signal of the calculation unit 30 is input to the display unit 50.
[0012]
The housing 10 is slidably mounted with a cylindrical shielding portion 80 for shielding a surrounding electric field that affects the potential of the metal plate 70. As will be described later, the shielding portion 80 is drawn out as shown in FIG. 1B when the potential of the metal plate 70 is initialized, and in the measurement state after the initialization, the shielding portion 80 shown in FIG. As shown in ()), it is in a state of being pushed into the housing 10 constituting the apparatus main body. When the shielding portion 80 is pulled out, as shown in FIG. 1B, the metal plate 70 is located inside the cylinder of the shielding portion 80, and shields the electric field around the metal plate 70. I have. In this embodiment, when the cylindrical shielding portion 80 is pulled out, one end side thereof is left open. However, if the distance from this opening portion to the metal plate 70 is sufficient, the electric field is substantially shielded. State.
[0013]
FIG. 2 shows a block configuration of the charge amount measuring device. As shown in the figure, a capacitor 100 for forming a predetermined capacitance value Cp of the metal plate 70 is connected between the metal plate 70 and the ground, and a normally open switch is connected in parallel with the capacitor 100. 90 are connected. In this embodiment, it is assumed that the housing 10 held by the user forms the ground, and the above-described capacitor 100 is connected between the metal plate 70 and the housing 10. Of course, it is desirable to connect the housing 10 to the original ground (earth). The detection unit of the surface voltmeter 20 is directed toward the surface of the metal plate 70, and the potential signal SV, which is the output signal of the surface voltmeter 20, is input to the calculation unit 30 as described above. , A display signal SH representing the calculation result is output to the display unit 50.
[0014]
Next, the operation of this embodiment will be described.
Here, it is assumed that the amount of electric charge induced in a semiconductor device in a manufacturing process is measured by the action of an electric field generated by peripheral devices at a manufacturing site.
First, an operator initializes the potential (charge amount) of the metal plate 70 in a place (measurement site) where the influence of the electric field on the semiconductor device is concerned. At the time of this initialization, the operator pulls out the shield 80 from the apparatus main body, and shields the electric field affecting the potential of the metal plate 70 by the shield 80. Then, the operator closes the normally open switch 90 in a state where the electric field to the metal plate 70 is shielded. Thus, the capacitor 100 is discharged in a state where an external electric field is shielded from the metal plate 70, and the potential of the metal plate 70 is initialized to the ground potential.
[0015]
The surface voltmeter 20 measures the surface potential of the metal plate 70 initialized to the ground potential (that is, the terminal voltage of the capacitor 100), and outputs a potential signal SV indicating the measured value Vm of the surface potential. In response to the potential signal SV, the calculation unit 30 calculates the amount of charge accumulated in the capacitor 100, that is, the amount of charge Q (= Cp) induced in the metal plate 70, based on the measured value Vm and the known capacitance value Cp of the capacitor 100. × Vm), and outputs a display signal SH indicating the calculation result to the display unit 50. In this case, since the measured value Vm becomes the ground potential (= 0 V), the charge amount Q indicated by the display signal SH becomes zero. That is, the metal plate 70 is neutralized by the above-described operation.
[0016]
Subsequently, the operator opens the normally open switch 90, and then stores the shielding unit 80 in the apparatus body. As a result, the metal plate 70 is set to the electric field generated by the surrounding devices. As a result, a surrounding electric field acts on the metal plate 70 to induce electric charges, and the potential of the metal plate 70 is stabilized at a potential corresponding to the electric field formed by the electric field. At this time, since the shape of the metal plate 70 is in accordance with the shape of the semiconductor device to be placed in this environment, the influence of the electric field acting on the metal plate 70 is affected by the effect acting on the actual semiconductor device. Is equal to Therefore, the amount of charge induced in the metal plate 70 becomes equal to the amount of charge induced in the actual semiconductor device. From the potential of the metal plate 70, the amount of charge likely to be induced in the actual semiconductor device is determined. It becomes possible to do.
[0017]
In this case, the surface voltmeter 20 measures the surface potential of the metal plate 70 in the state where the electric charge is induced, and outputs a potential signal SV indicating the measured value Vm of the surface potential of the metal plate 70. This measured value Vm depends on the amount of charge induced on the metal plate 70. In response to the potential signal SV, the calculation unit 30 calculates the charge amount Q (= Cp × Vm) induced on the metal plate 70 from the measured value Vm and the known capacitance value Cp of the capacitor 100, and calculates the calculation result. The display signal SH shown is output to the display unit 50. As a result, the amount of charge induced on the metal plate 70 is displayed on the display unit 50 as a calculation result of the calculation unit 30.
[0018]
As described above, according to this embodiment, at the time of measurement, the potential of the metal plate 70 is initialized in a state where an external electric field affecting the potential of the metal plate 70 is cut off. The potential of the plate 70 can be properly initialized. If the initialization is performed without providing the shielding unit 80, the initialization is performed in a state where the potential of the metal plate 70 is affected by the surrounding electric field, and the amount of charge induced in the metal plate 70 is accurately evaluated. Can not be done. However, in this case, if initialization is performed in a place not affected by the electric field, there is no inconvenience in the subsequent measurement.
[0019]
As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and includes any design change or the like without departing from the gist of the present invention. For example, in the above-described embodiment, the shielding portion 80 is formed in a cylindrical shape, but may be formed in a cap shape and fixed to the housing 10 so as to cover the metal plate 70 at the time of initialization. In any case, as long as the surrounding electric field that affects the potential of the metal plate 70 can be shielded, any shape or material may be used as the shield 80.
[0020]
【The invention's effect】
As described above, according to the present invention, since the metal member having the predetermined capacity and the surface voltmeter for measuring the surface potential of the metal member are provided, the metal member is induced by the electric field without preparing the sample. The amount of charge that appears can be measured.
Further, a switch for initializing the metal member to a predetermined potential is further provided, so that the potential of the metal member can be initialized at the time of measurement.
Further, since a shielding member for shielding an electric field affecting the potential of the metal member is further provided, it is possible to appropriately initialize the potential of the metal member at the measurement site.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a schematic structure of a charge amount measuring device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a block configuration of a charge amount measuring device according to an embodiment of the present invention.
[Explanation of symbols]
10; housing; 20; surface voltmeter; 30; computing section; 40; battery; 50; display section, 60; insulator, 70; metal plate, 80; shielding section, 90; normally open switch, 100;

Claims (4)

A charge measuring device for measuring a charge induced by an electric field,
A metal member attached to the device body via an insulator and having a predetermined capacity;
A surface potentiometer is provided on the apparatus main body so as to face the metal member, and measures a surface potential of the metal member,
Charge measuring device provided with. The charge amount measuring device according to claim 1, further comprising a switch for initializing the metal member to a predetermined potential. The charge amount measuring device according to claim 2, further comprising a shielding member for shielding an electric field that affects a potential of the metal member when the metal member is initialized to a predetermined potential. A calculation unit that calculates a charge amount from a predetermined capacity of the metal member and a potential measured by the surface electrometer,
A display unit that displays a calculation result of the calculation unit;
The charge amount measuring device according to claim 1, further comprising:

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