JPH09205124A - Control electrode and charging apparatus for mobile ion isolating device using the electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain charging in a partial region of a wafer and measurement of mobile ions at a plurality of positions. SOLUTION: In charging treatment of BT processing, a charged wire 37 located to face a silicon wafer 7 is horizontally tensioned on an aperture surface (the surface exposed to the wafer) of a shield electrode 32 having a U-shaped cross section. A controlled electrode 33 having a transmitting region 37 formed in a substantially center portion is provided on the forward side of the charged wire 37 on the aperture surface of the shield electrode 32. Ionized molecules by corona discharge are supplied to the surface of the silicon wafer 7 only within the transmitting region 37 of the controlled electrode 33. The controlled electrode 33 attains charging only in a partial region AR of the silicon wafer 7 facing the transmitting region 37, add measurement of mobile ions in the partial region AR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a control electrode interposed between a charging electrode and an object to be charged which is charged by corona discharge generated in the charging electrode, and a control electrode for a wafer. The present invention relates to a charging device of a mobile ion separation device that applies electric charges to the wafer surface in order to move mobile ions contained in an oxide film to the film surface or the interface between the film and the wafer.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, transistor characteristics are greatly affected by mobile ions (mainly mobile Na ions) penetrating into a SiO ₂ film which is an oxide film of a silicon wafer.
Oxide film evaluation that estimates the number of mobile ions in the SiO ₂ film using the −V characteristic has been performed.

Conventionally, a corona charging method has been proposed as a method for evaluating the oxide film. In this corona charging method, a direct current high voltage is applied between a silicon wafer and a charging electrode facing the surface of the silicon wafer, and the ions generated by the corona discharge are applied to the surface of the silicon wafer to be charged. after, and heated to a predetermined high temperature by moving the movable ions in the SiO ₂ film at the interface surface or SiO ₂ film and the silicon wafer of SiO ₂ film, then removed the excess unwanted charge on the surface, the surface or interface This is a method of electrically neutralizing (cancelling) the mobile ions that have moved to. This is generally called BT (Bias-Temperature) processing.

When the mobile ions are electrically neutralized as described above, the mobile ions are apparently absent,
Since the CV characteristics change as compared with those before the BT treatment, the oxide film is evaluated by estimating the number of mobile ions from the change amount of the CV characteristics.

In the field of electrostatic electrophotography, a charging device such as a corotron or a scorotron, which charges a surface of a photosensitive material by corona discharge to sensitize it, is known.

[0006]

A conventional charging device for a movable ion separator using a corona charging method is an application of the above-mentioned corotron or scorotron, and is adapted to charge the entire surface of a silicon wafer by corona discharge. Therefore, the movable ion amount can be measured only for each wafer, and it is difficult to measure the movable ion amount for a partial region on the silicon wafer.

Although it is possible to locally charge the wafer by making the size of the charging electrode relatively small with respect to the wafer, this method requires controlling the applied voltage according to the type of the charging electrode. In addition, when changing the charged area of the wafer, it is necessary to control the movement of the charging electrode, which complicates the drive system and the control system.

Further, the scorotron is provided with a control electrode between a charging electrode and an object to be charged, and the control electrode controls the charging. However, the control electrode in the scorotron is uniform over the entire surface of the photosensitive material. Since it controls the charging and does not limit the charging area of the object to be charged, this control electrode cannot completely control the charging of a partial area of the wafer.

The present invention has been made in view of the above problems, and efficiently utilizes a control electrode and a measurement sample capable of charging only a partial region of an object to be charged to efficiently evaluate an oxide film on a wafer. It is an object of the present invention to provide a charging device for a movable ion separation device that can be well performed.

[0010]

The present invention relates to a control electrode provided between a charging electrode and an object to be charged which is charged by a corona discharge generated in the charging electrode, the control electrode being generated by the corona discharge. The present invention further comprises a conductive member having a transmissive region for transmitting the generated ions to the charged object side and a restriction region for restricting the charged region of the charged object (Claim 1).

According to the above construction, when a high DC voltage is applied to the charging electrode to cause corona discharge, the molecules in the gas are ionized, and the ions of the same polarity as the charging electrode adhere to the side of the object to be charged. . Most of the ions are trapped in the restricted region, which is a non-transmissive region of the conductive member, and a part of the ions permeate from the transmissive region to the charged object side, and are charged in a partial region of the charged object.

The present invention also provides the above control electrode,
The transmission region is formed by forming a plurality of micropores in a matrix (claim 2). According to the above configuration, it is possible to change the charge amount and the charge range by adjusting the size and the number of the micropores.

Further, according to the present invention, in the above control electrode,
The transmissive region is formed by forming a plurality of elongated holes having a minute width in parallel in a direction along the charging electrode (claim 3). According to the above configuration, the distribution of the charging potential is flattened at least in the direction along the charging electrode on the object to be charged, as compared with the case where the minute holes are formed in a matrix.

The present invention also provides the above control electrode,
The plurality of elongated holes are formed at equal intervals in two facing areas, and the width of the holes becomes wider as the distance from the boundary between the two areas increases ( Claim 4). According to the above configuration, the distribution of the charging potential on the object to be charged is flattened not only in the direction along the charging electrode but also in the direction orthogonal to the charging electrode.

Further, according to the present invention, in the above control electrode,
The plurality of elongated holes are formed with the same hole width in each of the two facing regions, and the hole spacing becomes narrower as the distance from the boundary between the two regions increases ( Claim 5). According to the above configuration, the distribution of the charging potential on the object to be charged is flattened not only in the direction along the charging electrode but also in the direction orthogonal to the charging electrode.

Further, according to the present invention, in the above control electrode,
The plurality of elongated holes are formed so that the hole width is wider than the hole interval (claim 6). According to the above configuration, the distribution of the charging potential on the object to be charged in the direction along the charging electrode and the direction orthogonal to the charging electrode is flattened.

Further, according to the present invention, in order to move the mobile ions in the oxide film of the wafer to the surface of the film or the interface between the film and the wafer, a high voltage is applied to the charging electrode opposed to the wafer, and corona discharge is performed. A charging device of a movable ion separation device for applying the ions to the wafer surface is provided with the control electrode (claim 7).

According to the above structure, when a high DC voltage is applied to the charging electrode, the molecules in the air are ionized by the corona discharge generated around the charging electrode, and the ions of the same polarity as the charging electrode are on the wafer side. However, most of the ions are trapped in the restricted region, which is a non-transmissive region of the conductive member, and some of the ions are transmitted from the transmissive region to the wafer side. As a result, ions are imparted to the region of the wafer surface facing the transmission region, and the mobile ions in the oxide film in this region are moved to the surface of the oxide film or the interface with the wafer by the imparted ions.

Further, according to the present invention, in the charging device of the movable ion separator, a shield case for shielding a half space of the charging electrode opposite to the wafer is provided, and the control electrode is provided on an opening surface of the shield case. It is detachably attached (Claim 8). According to the above configuration, the charging electrode is surrounded by the shield case and the control electrode, and is protected from electrical and mechanical damage such as short circuit and disconnection.

[0020]

1 is a front view of an external unit for a CV measuring system equipped with a charging device for a movable ion separator according to the present invention, and FIG. 2 is an external unit for the CV measuring system. FIG.

The CV measuring system is composed of Si semiconductor and S
C-V characteristics of a silicon wafer with an iO ₂ film formed (M
A system for measuring (correlation characteristics between the DC voltage applied to the OS diode and the electric capacity), a process for separating mobile ions, which is a part of the BT process, on the main body 2 of the external unit 1 for the CV measurement system. The movable ion separation unit 3 for performing

The C-V measuring system has an oxide film evaluation, a bare wafer evaluation (evaluation of carrier concentration in a bare state), a crystallinity evaluation (C-t characteristic (electric capacitance against applied pulse voltage) in relation to C-V characteristics. Various evaluations such as time-varying characteristics)) are possible, and the evaluation can be performed by operating the keyboard 4 in accordance with the display contents displayed on a CRT (Cathode Ray Tube) display device (not shown).

The oxide film evaluation evaluates the amount of movable ions contained in the SiO ₂ film from the deviation amount of the CV characteristic of the silicon wafer from the ideal characteristic. The deviation amount of the CV characteristic is
C measured with mobile ions mixed in the SiO ₂ film
CV measured while separating -V characteristics and mobile ions
It is calculated from the characteristics.

The movable ion separation unit 3 imparts electric charges to the surface of the silicon wafer by corona discharge, and then restrains the movable ions (mainly Na ions) contained in the SiO ₂ film by the imparted electric charges. Mobile ions as Si
It separates the surface of the O ₂ film and the interface between the SiO ₂ film and the silicon wafer.

The movable ion separation unit 3 has a BT processing chamber for carrying out processing such as charging and heating inside the unit main body.
Opening window 5 formed in the center of the step on the front of the unit
The silicon wafer is transferred to the processing chamber by a transfer tray that is vertically movable.

FIG. 3 is a schematic side view showing the internal structure of the movable ion separation unit. In the figure, the right end is the front side of the movable ion separation unit 3 and the left end is the rear side of the movable ion separation unit 3. The movable ion separation unit 3 includes a transfer tray 6 for transferring the silicon wafer 7 on the front side of the upper surface of the unit main body 301.

The carrying tray 6 has a holding portion 61 having an opening 61A, and the silicon wafer 7 is mounted on the holding portion 61. The transfer tray 6
Is a position on the upper surface of the unit body 301 where the silicon wafer 7 is attached / detached (hereinafter referred to as an attachment / detachment position) and a position below the opening window 5 for charging, heating, etc. It is provided so as to be able to move up and down between a predetermined position where processing is performed (hereinafter referred to as a processing position).

The transport tray 6 is driven up and down by a transport tray drive unit 8 provided on the left side (front side in the figure) of the unit main body 301 when viewed from the front side. The transport tray driving unit 8 includes pulleys 10 and 11 rotatably attached to upper and lower ends of a support plate 9 that has been erected, a wire rope 12 wound between the pulleys 10 and 11, and a pulley 11 at a lower end. And a drive motor (not shown) fixed to the drive motor.

The carrying tray 6 has a supporting portion 62 provided at a proper place on the lower surface thereof fixed to the wire rope 12, and the wire rope 1 is passed through the pulley 11 by the rotational force of the drive motor.
It is lifted and lowered by rotating 2 clockwise or counterclockwise.

Further, on the upper surface of the unit main body 301, a shutter 13 for blocking the opening window 5 is provided slidably from the rear surface side to the front surface side when the transport tray 6 is lowered to the processing position.

The shutter 13 is driven to slide by a shutter drive section 14 provided below the shutter. The shutter drive unit 14 is wound between a pair of pulleys 16 and 17 and both pulleys 16 and 17 provided at both ends of the movement range of the shutter 13 of the support plate 15, and the wire rope 18 to which the shutter 13 is fixed. The rear pulley 16 is composed of a drive motor (not shown) fixed to the drive shaft, and the shutter 13 is slid by being pulled by the wire rope 18 similarly to the transport tray drive unit 8.

A heater unit 20 for heating the silicon wafer 7 carried by the carrying tray 6 on the table 19 is provided at the processing position.
A charging unit 23 for charging the silicon wafer 7 is provided at the rear position of the above so as to be slidable toward the heater unit 20 side.

The heater unit 20 includes a heater stage 21 for vacuum-adsorbing the silicon wafer 7 transferred on the transfer tray 6, a heater (not shown) for heating the heater stage 21, and a heater temperature for controlling the heating temperature of the heater stage 21. The controller 22 and a cooling fan (not shown) for cooling the heated silicon wafer 7 are provided.

The charging unit 23 includes a pair of heads 24 having charge wires and a power supply 25 for supplying a predetermined high DC voltage to the charge wires.
The slide unit is driven by the charging unit drive unit 26 provided in the lower part of 3. The head portion 24 is capable of charging a partial region of the silicon wafer 7 as described later, and in the present embodiment, two regions of the silicon wafer 7 can be charged positively and negatively, respectively. Two are provided side by side. Further, the power supply section 25 is adapted to be able to supply high DC voltages having different polarities to the two head sections 24.

The charging unit drive section 26 includes a pair of pulleys 2 provided at both ends of the moving range of the charging unit 23.
7 and 28, a wire rope 29 wound between both pulleys 27 and 28, to which the charging unit 23 is fixed, and a drive motor (not shown) in which the pulley 27 on the rear surface side is fixed to the drive shaft. 8. The charging unit 23 is slid by being pulled by the wire rope 29 similarly to the shutter drive unit 14.

When the charging unit 23 is slid to the processing position, the charge wire of the head portion 24 is arranged at a height position separated from the surface of the silicon wafer 7 mounted on the transfer tray 6 by a predetermined distance. It is supposed to be done.

A controller 30 for centrally controlling processing such as charging and heating is provided at a position behind the table 19 in the unit body. The controller 30 controls driving of actuators and units of the transport tray 6, the shutter 13, the heater unit 20, and the charging unit 23, and also controls processes such as charging and heating of the silicon wafer 7.

FIG. 4 is a vertical sectional view showing the structure of the head portion, FIG. 5 is a bottom view of the head portion, and FIG. 6 is a right side view of the head portion.

The head portion 24 has a charge wire 31 to which a high voltage is applied, a shield case 32 for shielding a half space of the charge wire 31 on the opposite side to the silicon wafer 7, and an opening surface of the shield case 32 (the silicon wafer 7). Control electrode 33 provided on the surface (opposite to the side) and terminal portion 34 provided on the base end of the shield case 32.
It is composed of

The charge wire 31 is a charging electrode that generates corona discharge between the wire surface and the silicon wafer 7 to ionize molecules in the air, and is made of, for example, a tungsten wire having a wire diameter of several tens of μm.

The shield case 32 is made up of the charge wire 3
1, a stable corona discharge is generated in the longitudinal direction of the wire by causing a discharge current to flow, and molecules charged by the corona discharge (hereinafter referred to as ionized molecules) are prevented from being charged on the surface of the silicon wafer other than the surface. Things. The shield case 32 is an electrode having a U-shaped cross section that shields the surface facing the silicon wafer 7 and the side surface excluding the base end, and is formed by bending a single metal plate of stainless steel, for example. Two U-shaped conductive support plates 35 and 36 are provided at appropriate positions on the inner surface of the shield case 32, and the charge wires 31 are attached to the support plates 35 and 36.

The control electrode 33 is an electrode plate made of a rectangular conductive member that limits the discharge of ionized molecules to the silicon wafer 7 side, and has a size substantially the same as the opening surface of the shield case 32. As shown in FIG. 7, the control electrode 33 has a plurality of angular micro-holes at a position displaced substantially toward the center of the electrode plate so as to limit the charged area of the silicon wafer 7, as shown in FIG. 38 are formed in a matrix shape, and several millimeters or several centimeters in length and width are formed in order to allow ions generated by the corona discharge to pass to the silicon wafer 7 side.
A transmissive region 37 having a size of the order is formed. A region other than the transmission region 37 of the control electrode 33 forms a limiting region that blocks the ion transmission and limits the charged region of the silicon wafer 7.

The limiting electrode 33 is provided with the minute holes 38 at the position where the transmission region 37 of a thin metal plate made of, for example, stainless is formed.
Is formed by laser processing. Further, instead of the micropores 38, a conductive mesh having angular micropores may be attached. It should be noted that the micropores 3 in the transmission region 37
The shape of the holes of 8 and the mesh is not limited to the rectangular shape, and any shape such as a circle, an ellipse, or a triangle can be adopted. In addition, a portion of the transmission region 37 is formed with a plurality of micro holes 38.
One through hole may be used instead of the one made of. Furthermore, in the present embodiment, the transmission region 37 is provided in one region of the control electrode 33, but the transmission region 37 may be provided in two or more regions.

Two U-shaped conductive support pieces 35 and 36 are provided at appropriate positions on the inner surface of the shield case 32, and the control electrode 33 is detachably attached to the support pieces 35 and 36 by screws or the like. ing.

According to such a control electrode 33, by changing the size of the transparent region 37, the silicon wafer 7
Of the micropores 38 (ie,
Since the charge amount of the charging area changes by changing the mesh size of the transparent area 37, a plurality of control electrodes 33 having different positions and sizes of the transparent area 37 and the mesh size are prepared. By replacing the control electrode 33 of 24 with a predetermined one, the charged area and the charged amount of the silicon wafer 7 can be set to desired conditions.

In the terminal portion 34, the power supply line 41 from the power source portion 25 is connected to the base end portion of the charge wire 31 to connect the terminal 39.
It is connected through. The terminal portion 34 is made of an insulating member such as a synthetic resin, and has a cross section L in which an intermediate portion is bent at a right angle.
It is shaped like a letter.

At the tip of the terminal portion 34 from which the charge wire 31 is pulled out, a fitting portion 34 having a U-shaped cross section having an outer diameter dimension substantially the same as the shape dimension of the inner side surface of the shield case 32.
A terminal holding portion 342 for fixing the connection terminal 39 is formed at the base end of the fitting portion 341 by bending at a right angle.

The terminal holding portion 342 has a side wall 343 protruding from the peripheral edge thereof so as to form a terminal accommodating chamber, and the lid 40 is fitted and mounted on the inner side surface of the side wall 343 to connect the connection terminal 3 to each other.
The terminal holding chamber in which 9 is housed is hermetically sealed.

The connection terminal 39 is made of a metal piece and is fixed to the bottom of the terminal storage chamber formed in the terminal holding portion 342. The power supply line 41 is connected to one end of the connection terminal 39, and the base end of the charge wire 31 is connected to the other end. The charge wire 31 is drawn out toward the shield case 32 through the fitting portion 341, and is extended in parallel with the control electrode 33 at an opening surface of the shield case 32 and separated by a predetermined dimension D from the control electrode 33. Have been.

That is, the holding members 42 and 43 made of an insulating member are provided on the inner side surfaces of the portions of the support pieces 35 and 36 facing the opening surfaces.
The charge wire 31 pulled out from the terminal portion 34 while holding the intermediate portion and the distal end of the wire with the holding members 42 and 43, respectively, is stretched in parallel with the control electrode 33 at a predetermined interval D. ing.

With the above configuration, as shown in FIG. 8, when the head portion 24 is arranged facing the silicon wafer 7 and subjected to the charging process, only a partial area AR facing the transmission area 37 of the silicon wafer 7 is corona-discharged. Ionized molecules or electrons are added.

That is, as shown in FIG.
No. 4 charge wire 31 is connected to one electrode (for example, a minus electrode) of the power supply unit 25, and the shield case 32, the control electrode 33, and the silicon wafer 7 are connected to the other electrode (plus electrode) of the power supply unit 25 to connect the charge wire 31. When a high DC voltage is applied to the wire, corona discharge is generated on the surface of the charge wire 31, and molecules in the air around the wire are ionized.

Of the ionized molecules, the charge wire 31
The positive ionized molecules 44 of the opposite polarity are electrostatically attracted to the charge wire 31, and the negative ionized molecules 45 of the same polarity are electrostatically attracted to the shield case 32 and the control electrode 33, and the negative ionized molecules 45 Is a discharge current flowing between the charge wire 31, the shield case 32, and the control electrode 33, and a part thereof is transmitted through the transmission region 37 of the control electrode 33 and is charged on the surface of the silicon wafer 7.

In this case, since the transmissive region 37 is formed in a partial region of the control electrode 33, the silicon wafer 7 is provided with the negative ionized molecules 45 only in the partial region AR facing the transmissive region 37. , The other areas are not charged by the ionized molecules.

In FIG. 9, when the power supply polarity of the power supply unit 25 is reversed, the negative ionized molecule 45 is electrostatically attracted to the charge wire 31, and the positive ionized molecule 44 is electrostatically attracted to the control electrode 33. Are partially attracted to the surface of the silicon wafer 7 through the transparent region 37.

As described above, the transmissive region 3 is formed in a part of the opening surface of the shield case 32 facing the silicon wafer 7.
Since the control electrode 33 having the electrodes 7 formed therein is provided, the area AR facing the transmission area 37 on the surface of the silicon wafer 7 is formed.
Only the charge is possible, and the mobile ion separation process and the oxide film evaluation can be performed on this area AR.

Further, since the charge wire 31 is housed in the cylindrical body composed of the shield case 32 and the control electrode 33, it is possible to prevent electrical and mechanical damage such as short circuit and disconnection of the charge wire 31. It will be possible.

FIG. 10 is a block diagram of the movable ion separation unit. 3, the same members as those shown in FIG. 3 are denoted by the same reference numerals. In addition, vacuum pump 4
6 is a suction source for adsorbing the silicon wafer 7 to the heater stage 21, a display unit 47 is a display device such as a CRT, and an operation unit 48 is a unit including the keyboard 4 for starting processing and setting the silicon wafer 7 at a processing position. / An operation unit for inputting instructions such as resetting and various processing conditions. Also,
The heater 211 is a heat source provided on the heater stage 21,
The heater temperature controller 22 is an energization controller that controls energization of the heater 211.

Next, the processing operation in the movable ion separation unit will be described with reference to FIG.

First, after the START switch for processing is operated (step S1) and the silicon wafer 7 is mounted on the holding portion 61 of the transfer tray 6 (step S2), the LOA is set.
When the D switch is operated (step S3), the transport tray drive unit 8 is driven, and the transport tray 6 is lowered from the attachment / detachment position to the processing position by the winding operation of the wire rope 12 (step S4). At this time, at the same time, the shutter drive unit 1
4 is driven, the shutter 13 moves from the open position to the closed position, and the opening window 5 is completely closed.

Then, the vacuum pump 46 is driven, and the silicon wafer 7 is adsorbed to the heater stage 21 arranged oppositely through the opening 61A (step S5).
Then, the charging unit driving unit 26 causes the charging unit 2
3 is slid from the standby position to the processing position, and the two head portions 24 and 24 'of the charging unit 23 are arranged facing the upper portion of the silicon wafer 7 as shown in FIG. 12 (step S6). Then, from the power supply unit 25 to the head unit 2
4 is supplied with a positive DC high voltage, and the head portion 24 'is supplied with a negative DC high voltage, so that the silicon wafer 7 is charged (step S7).

As described above, since the control electrodes 33 are provided on the opening surfaces of the shield cases 32 of the head portions 24, 24 ', the silicon wafer 7 has a region AR1 opposed to the transmission region 37 of each control electrode 33. (Hereinafter, the first area AR
One. ), And only AR2 (hereinafter, referred to as a second area AR2) is charged by corona discharge. In this case, since a positive voltage is supplied to the head portion 24, the first area AR1 is positively charged, and the head portion 2
Since a negative voltage is supplied to 4 ', the second area AR2 is negatively charged.

Subsequently, when the charging process is completed, the charging unit 23 is slid from the processing position to the standby position (step S8), and then the heater 211 is energized by the heater temperature adjusting section 22 to heat the silicon wafer 7. Is performed (step S9). In this heat treatment, the silicon wafer 7 is heated at a predetermined high temperature of 100 ° C. or higher for a predetermined time (about 10 minutes or longer).

By this heat treatment, the movable Na ions move in the SiO ₂ film of the silicon wafer 7, and the first region AR1
In the second area AR2, as shown in FIG.
The movable Na ions are electrostatically separated into ionized molecules 44 and 45 provided on the surface of the silicon wafer 7, respectively. Since the positive ionized molecules 44 are provided in the first region AR1, the positively charged movable Na ions 49 are converted into SiO ₂ by the ionized molecules 44.
Electrostatically repelled to the lower surface of the film (boundary with the silicon layer),
In the second region AR2, the negative ionized molecules 4
5, the movable Na ions 49 are electrostatically attracted to the surface of the SiO ₂ film by the ionized molecules 45, and the state of the movable Na ions 49 is maintained by maintaining this electrostatic attraction or repulsion state. Separation takes place.

When the heating process is completed, the driving of the vacuum pump 46 is stopped and the heater stage 21 of the silicon wafer 7 is stopped.
After the adsorption to the is released (step S10), the transport tray 6 is lowered to the cooling position (step S11), and the cooling process is performed for a predetermined time by the air blow by the cooling fan 212 (step S12). When the silicon wafer 7 is cooled by this cooling process, the movable Na ions separated by the electrostatic attraction or repulsion cannot move and remain in that position.

When the cooling process is completed, U is operated from the operation unit 36.
When the NLOAD switch is operated (step S13), the transport tray drive unit 8 is driven, and the transport tray 6 is raised from the processing position to the mounting / dismounting position by the circling operation of the wire rope 12 (step S14).

When the carrying tray 6 is raised to the mounting / removing position, the silicon wafer 6 is carried out (step S15), and the process is completed. After the processing is completed, the silicon wafer 7 is washed with water, alcohol, or the like to remove excess ionized molecules 44 and 45 on the wafer surface.

In the silicon wafer 7 from which the mobile ions have been separated, the number of mobile ions is calculated by measuring the CV characteristics of the first area AR1 and the second area AR2.

That is, FIG. 14 shows C of the silicon wafer 7.
Although an example of the -V characteristic is shown, assuming that the CV characteristic of the silicon wafer 7 before the mobile ion separation processing is taken, the CV after the silicon wafer 7 is negatively charged and the mobile ion separation processing is performed. The characteristics are as follows:
CV characteristic after the silicon wafer 7 is positively charged and the mobile ion separation process is performed,
Shifts to the minus side of the bias voltage V as shown in FIG.
It is known that ΔV2 is proportional to the number of mobile ions.

Therefore, the first area AR1 and the second area AR
2 are measured, and the shift amounts ΔV1 and ΔV2 are calculated for each of the regions, thereby obtaining the first and second regions A
The number of mobile ions contained in R1 and AR2 is calculated. Note that the number of mobile ions can also be calculated from ΔV1 + ΔV2.

As described above, the control electrode 33 having the transmissive region 37 formed in a partial region is provided between the charge wire 31 of the charging unit 23 and the silicon wafer 7, and the control region 33 of the silicon wafer 7 faces the transmissive region 37. Since it is possible to charge only the surface of the silicon wafer 7, the oxide film can be easily evaluated for a partial region of the silicon wafer 7.

Further, two head portions 24, 24 ′ are arranged on the silicon wafer 7 so as to face each other.
Since 24 'is charged with different polarities, the oxide film can be evaluated simultaneously with positive and negative polar mobile ions.

Further, by changing the area of the transparent area 37 facing the silicon wafer 7, it is possible to evaluate the oxide film in a plurality of areas of the silicon wafer 7, so that the evaluation sample can be effectively used and the evaluation efficiency can be improved. Become.

By the way, in the above embodiment, the control electrode 33 is provided on the head portion 24 of the charging unit 23. However, as shown in FIG.
3'may be interposed between the silicon wafer 7 and the charge wire 31.

In this case, the control electrode 3 of the silicon wafer 7
Since the charging area is limited only to the area AR opposed to the transmissive area 37 formed in 3 ', the size of the control electrode 33' is three-dimensional as seen from the charge wire 31 to the control electrode 33 'as shown in FIG. The angle ω2 is at least set to a size that is substantially the same as the solid angle ω1 when the silicon wafer 7 is viewed from the charge wire 31. By doing so, the portion other than the area AR of the silicon wafer 7 is controlled by the control electrode 33 '.
By this, the charged area can be surely limited to the area AR.

The size of the control electrode 33 'may be smaller than the above size as long as the charging of the peripheral portion of the silicon wafer 7 does not affect the measurement of the movable ions in the area AR.

Further, as apparent from FIG. 16, the size of the control electrode 33 'can be made smaller as the control electrode 33' is closer to the charge wire 31. Therefore, in consideration of the holding of the control electrode 33 'and power feeding, the above-mentioned embodiment is preferable. As shown in, the control electrode 33 'is preferably attached to the opening surface of the shield case 32 of the charge wire 31.

In the above embodiment, the control electrode 33 is used.
The transparent region 37 is formed by forming a plurality of minute holes 38 in a matrix, but as shown in FIG. 17, a plurality of elongated holes 51 having a minute width are formed in a direction along the charge wire 31. You may make it comprised by forming in parallel with a predetermined hole space | interval. That is, FIG.
The transparent regions 37 ′ shown in FIG. 2 are elongated holes 51 a, 51 b, 51 c, 51 d, 5 in two opposing regions on both sides of the boundary B, which are positions facing the charge wire 31, respectively.
1e and 51f are arranged symmetrically with the boundary B as a boundary.

Holes 51 in each region on both sides of the boundary B
The hole spacings of a, 51b, 51c, 51d, 51e, and 51f are the same, but the distance between the holes 51a and 51a in contact with the boundary B of each region is set to be wider than the other hole spacings. Has been done. Further, the hole width dimension of the hole 51a in contact with the boundary portion B of each region (the dimension of the hole in the direction orthogonal to the boundary portion B) is slightly narrower than the hole 51b, and the hole width dimension of the hole 51b is smaller than that of the hole 51c. It is set to be narrower. The hole width dimension of the hole 51c is set slightly narrower than that of the hole 51d, and the holes 51d to 51f are set to have the same hole width dimension.

That is, the hole located near the boundary B has a narrow hole width, and the hole width dimension increases as the distance from the boundary B increases. The hole width dimension does not have to be gradually increased for each hole, but may be increased for every two holes or every three holes.
In addition, the holes 51a, 51b, 51c, 5 in each region
The hole width dimensions of 1d, 51e, and 51f are set to be wider than the hole intervals.

FIG. 18 shows a transparent region 3 having the structure shown in FIG.
In the direction orthogonal to the boundary B when the silicon wafer is charged by using the control electrode 33 ″ forming 7 ′, that is,
FIG. 6 is a diagram showing a distribution of a charging potential on a silicon wafer in a direction orthogonal to a charge wire 31. In this figure, the vertical axis represents the ratio to the highest potential, the horizontal axis represents the facing position of the charge wire 31 as 0, and the position on one side of the charge wire 31 in the direction orthogonal to the charge wire 31 as a boundary is +. , And the position on the other side is represented by-on the silicon wafer.

Further, FIG. 19 shows a direction along the boundary B when the silicon wafer is charged by using the control electrode 33 ″ forming the transmission region 37 ′ having the structure shown in FIG. 17, that is, along the charge wire 31. 3 is a diagram showing the distribution of the charged potential on the silicon wafer in the direction of the arrow, in which the vertical axis represents the ratio to the highest potential, and the horizontal axis represents the central position of the charge wire 31 at the facing position and the facing position is 0. The position on the silicon wafer is indicated by + on the right side and − on the left side along the position.

As is apparent from these figures, a substantially flat region is formed in the distribution of the charging potential within a certain range in both the direction orthogonal to the charge wire 31 and the direction along the charge wire 31. When such a flat region is formed, accurate measurement is possible within the range of the flat region of the distribution even if the measurement position deviates from the center position of the transmission region 37 'when measuring the C-V characteristic. Will be able to do.

20 and 21, the charging of the silicon wafer when the silicon wafer is charged using the control electrode 33 in which the minute holes 38 shown in FIG. FIG. 20 is a diagram showing a potential distribution and corresponds to FIGS. 18 and 19, respectively.
As is clear from these figures, the distribution of the charging potential is larger in the control electrode 33 ″ in which the transmission region 37 ′ is formed by the elongated hole 51 than in the control electrode 33 in which the transmission region 37 is formed by the minute holes 38. Thus, a flat region is formed, which is considered to be due to the following reasons.

That is, in the direction orthogonal to the charge wire 31, the amount of ionized molecules applied to the silicon wafer decreases as the distance from the charge wire 31 increases, but in the configuration of the transmission region 37 'of the configuration shown in FIG. Since the hole 51 at the near position has a narrow width and the hole 51 at a position away from the charge wire 31 has a wide width, the transparent region 3 having the configuration shown in FIG.
This is because the amount of ionized molecules applied to the silicon wafer can be made uniform more easily than in No. 7. Further, in the direction along the charge wire 31, the transparent region 37 having the configuration shown in FIG.
This is because the holes 51 are continuous along the charge wire 31 in ′, so that the application of ionized molecules is less likely to be discontinuous than in the permeation region 37 having the configuration shown in FIG. 7.

It should be noted that the holes 51a, 51b, 51c, 51d in the two regions facing each other on both sides of the boundary B shown in FIG.
The hole width dimensions of 51e and 51f may be the same, and the hole interval in each region may be widened at a position close to the boundary B and narrowed as the distance from the boundary B increases. Even in this case, each hole 51a, 51b, 51c, 5
It is desirable that the hole width dimension of 1d, 51e, and 51f be wider than the dimension of each hole interval. Even in this case, the same effect as that shown in FIG. 17 can be obtained. However, including the case of FIG. 17, the holes 51a, 51
The hole width dimension of b, 51c, 51d, 51e, 51f does not necessarily have to be larger than the dimension of each hole interval, and may be equal to the hole interval or narrower than the hole interval. .

If a plurality of elongated holes 51 are formed in parallel in the direction along the charge wire 31, the hole width and the hole interval of each elongated hole 51 do not necessarily satisfy the above conditions. You don't have to. Even in this case, it is possible to form a flat region in the distribution of the charging potential at least in the direction along the charge wire 31, and when measuring the CV characteristic, the measurement position is from the center position of the transmission region 37 'to the charge wire. Even if it is deviated in the direction along the line 31, accurate measurement can be performed within the range of the flat distribution region.

Further, in the plurality of elongated holes 51 forming the transmission area 37 'shown in FIG. 17, it is sufficient that at least the central portion of the transmission area 37' satisfies the above condition, The peripheral portion of the transmissive region 37 'may have a slightly irregular shape.

Further, regarding the plurality of minute holes 38 forming the transparent region 37 shown in FIG.
By increasing the hole width or narrowing the hole interval in the direction orthogonal to the charge wire 31, it is possible to further flatten the distribution of the charging potential of the silicon wafer.

Furthermore, in the present embodiment, the charging device of the movable ion separation device has been described as an example, but the control electrode according to the present invention does not uniformly charge the entire charged object, but only a partial region thereof. It is widely applicable as a control electrode that limits the charging area when the above-mentioned charging is required.

[0091]

As described above, according to the present invention,
A control electrode provided between the charging electrode and the object to be charged is formed with a transmission area for transmitting ions generated by corona discharge to the object to be charged and a restriction area for limiting the charging area of the object to be charged. Since it is composed of the conductive member, it is possible to reliably charge only the area facing the transparent area of the object to be charged.

Further, since the transmission area of the control electrode is formed by forming a plurality of micropores in a matrix, it is possible to easily control electrodes having different charge amounts and charge ranges by adjusting the size and number of the micropores. Can be created.

Further, since the transmission area of the control electrode is constituted by arranging a plurality of elongated holes having a minute width in parallel with the direction along the charging electrode, charging on the object to be charged at least in the direction along the charging electrode. The potential distribution can be flattened within a certain range, and accurate measurement can be performed even if the measurement position of the characteristic of the charged object is slightly shifted.

Further, a plurality of elongated holes of the control electrode are formed in two facing regions at equal hole intervals, and the hole width becomes wider as the distance from the boundary between the two regions increases. Since it is formed, the distribution of the charging potential on the charged object in the direction along the charging electrode and the direction orthogonal to the charging electrode can be flattened within a certain range, and the measurement position of the characteristic of the charged object is slightly displaced. Even then, it becomes possible to make accurate measurements.

Further, the plurality of elongated holes of the control electrode are formed in the two areas facing each other with the same hole width, and the hole spacing becomes narrower as the distance from the boundary between the two areas increases. Since it is formed, the distribution of the charging potential on the charged object in the direction along the charging electrode and the direction orthogonal to the charging electrode can be flattened within a certain range, and the measurement position of the characteristic of the charged object is slightly displaced. Even then, it becomes possible to make accurate measurements.

Further, since the plurality of elongated holes of the control electrode are formed so that the hole width is wider than the hole interval, the object to be charged in the direction along the charging electrode and the direction orthogonal to the charging electrode. The above distribution of the charging potential can be flattened more reliably within a certain range, and accurate measurement can be performed even if the measurement position of the characteristic of the charged object is slightly shifted.

Further, in a charging device of a movable ion separation device in which a high voltage is applied to a charging electrode arranged to face a wafer and ions are applied to the wafer surface by corona discharge, a control electrode is provided between the charging electrode and the wafer. Since it is interposed, a partial region of the wafer can be limitedly charged, and mobile ions can be measured at a plurality of points on the wafer.

Further, in the above charging device, a shield case for shielding the half space of the charging electrode on the side opposite to the wafer is provided, and the control electrode is detachably attached to the opening surface of the shield case, so that the entire charging electrode is shielded. Since it is shielded by the case and the control electrode, it is possible to reliably prevent mechanical or electrical damage such as disconnection or short circuit of the charging electrode.
Further, the charged area of the wafer can be easily changed by exchanging the control electrodes having different transmissive areas.

[Brief description of drawings]

FIG. 1 is a front view of an external unit for a CV measuring system equipped with a charging device for a movable ion separator according to the present invention.

FIG. 2 is a left side view of an external unit for a CV measuring system equipped with a charging device for a movable ion separator according to the present invention.

FIG. 3 is a schematic side view showing an internal structure of a movable ion separation device according to the present invention.

FIG. 4 is a vertical cross-sectional view showing the structure of the head portion of the charging device according to the present invention.

FIG. 5 is a bottom view of the head portion of the charging device according to the present invention.

FIG. 6 is a right side view of the head portion of the charging device according to the present invention.

FIG. 7 is a diagram showing a configuration of a transmission region of a control electrode.

FIG. 8 is a cross-sectional view showing a state in which the head portion of the charging unit is arranged facing the upper portion of the silicon wafer.

FIG. 9 is a diagram for explaining charging of a partial region of a silicon wafer by a charging unit.

FIG. 10 is a block configuration diagram of a movable ion separation unit.

FIG. 11 is a flowchart showing a sequence of processing operations of the movable ion separation unit.

FIG. 12 is a perspective view showing a charged region on the surface of a silicon wafer.

FIG. 13 is a diagram showing a state where mobile ions in an oxide film of a silicon wafer are separated.

FIG. 14 is a diagram showing changes in CV characteristics due to separation processing of mobile ions.

FIG. 15 is a perspective view showing a state in which a single control electrode is interposed between a charge wire and a silicon wafer.

FIG. 16 is a diagram for explaining the size of the control electrode when the control electrode alone is interposed between the charge wire and the silicon wafer.

FIG. 17 is a diagram showing another configuration example of a transmission region of a control electrode.

18 is a diagram showing a potential distribution on a silicon wafer charged by using the control electrode having the configuration shown in FIG.

19 is a diagram showing a potential distribution on a silicon wafer charged by using the control electrode having the configuration shown in FIG.

20 is a diagram showing a potential distribution on a silicon wafer charged using the control electrode having the configuration shown in FIG. 7.

21 is a diagram showing a potential distribution on a silicon wafer charged by using the control electrode having the configuration shown in FIG.

[Explanation of symbols]

 1 External Unit for C-V Measurement System 2 Unit Body 3 Movable Ion Separation Unit (Movable Ion Separation Device) 301 Unit Body 4 Keyboard 5 Opening Window 6 Transport Tray 61 Holding Part 61A Opening 62 Supporting Part 7 Silicon Wafer (Charged Object) ) 8 transport tray drive unit 9 support plate 10, 11 pulley 12 wire rope 13 shutter 14 shutter drive unit 15 support plate 16, 17 pulley 18 wire rope 19 table 20 heater unit 21 heater stage 22 heater temperature control unit 23 charging unit (charging unit) Device 24 Head part 25 Power supply part 26 Charging unit drive part 27, 28 Pulley 29 Wire rope 30 Controller 31 Charge wire (charging electrode) 32 Shield case 33, 33 ', 33 "Control electrode 34 Terminal part 341 Fitting 342 Terminal holding part 343 Side wall 35,36 Support piece 37,37 'Transmission area 38 Micropore 39 Connection terminal 40 Lid 41 Power supply line 42,43 Holding member 44,45 Ionized molecule 46 Vacuum pump 47 Display part 48 Operation part 49 Movable Na ion 51 Long hole

Claims (8)

[Claims] 1. A control electrode interposed between a charging electrode and an object to be charged which is charged by corona discharge generated in the charging electrode, wherein ions generated by the corona discharge are introduced into the object to be charged. A control electrode comprising: a conductive member having a transmissive region for transmitting light to a substrate and a restricted region for restricting a charged region of the charged object. 2. The control electrode according to claim 1, wherein the transmissive region is formed by forming a plurality of micropores in a matrix. 3. The control electrode according to claim 1, wherein the transmission region is formed by arranging a plurality of elongated holes having a minute width in parallel in a direction along the charging electrode. . 4. The plurality of elongated holes are formed at equal intervals in two facing regions, and the width of the holes becomes wider as the distance from the boundary between the two regions increases. The control electrode according to claim 3, wherein: 5. The plurality of elongate holes are formed with equal hole widths in two opposing regions, and the hole intervals are narrowed as the distance from the boundary between the two regions increases. The control electrode according to claim 3, wherein: 6. The control electrode according to claim 4, wherein the plurality of elongated holes are formed so that the hole width is wider than the hole interval. 7. A high voltage is applied to a charging electrode facing the wafer to move mobile ions in the oxide film of the wafer to the surface of the film or the interface between the film and the wafer, and the ions are transferred to the wafer by corona discharge. A charging device for a movable ion separation device, which is provided on a surface, comprising the control electrode according to any one of claims 1 to 6, wherein the charging device for a movable ion separation device uses a control electrode. 8. The charging device for a movable ion separator using the control electrode according to claim 7, further comprising a shield case for shielding a half space of the charging electrode opposite to the wafer, wherein the control electrode is the shield. A charging device for a movable ion separation device using a control electrode, which is detachably attached to an opening surface of a case.