JPH11307039A - Device and method for introducing impurity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the ratio of breaking of a gate insulation film from increasing even if the gate insulation film gets thinner. SOLUTION: An ion beam 119 introduces charged impurities into a material to be processed composed of a wafer 100 or a film formed on the wafer 100. An electron supply system 117 supplies the material to be processed with electrons for offsetting the charge of the impurities. When energy of electrons supplied from the electron supply system 117 is higher than the energy of electrons at which a gate oxide film formed on the wafer 100 is broken, a wafer voltage controller 114 outputs control signals to a tube bias controller 104 and an arc current controller 110, to lower the value of a tube bias voltage supplied from a first voltage supply source 103 and the value of an arc current supplied from a current supply source 109.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impurity introducing apparatus and an impurity introducing method.

[0002]

2. Description of the Related Art As VLSI devices become more highly integrated and miniaturized, the thickness of gate insulating films of MOS transistors is steadily reduced. The thickness of the gate insulating film is 0.5
Although it was about 10 nm in the μm device, it was 0.25 μm.
It is about 5 nm for m devices. The gate insulating film thinned in this way is becoming extremely sensitive to charge-up damage caused by ion implantation into the gate electrode.

Further, in order to cope with an increase in the diameter of a wafer and to improve the throughput, the maximum beam current in an ion implantation apparatus has been increased. For this reason, in order to suppress the positive charge-up caused by the ion beam, which is caused by the increase in the beam current density at the time of ion implantation, an improvement in the electron supply capacity of the electron supply system has been required. Was.

FIG. 10 shows a cross-sectional structure of a conventional impurity introducing apparatus, in which a guide tube 12 is provided so as to face a wafer 11 held on a substrate holder 10. A tube bias is applied from one voltage supply source 13. Ion beam 14 generated by ion beam generating means (not shown)
Is irradiated from the right side to the left side inside the guide tube 12 and then irradiated onto the surface of the wafer 11.

[0005] An arc chamber 16 is provided beside the guide tube 12, and a filament 17 is provided inside the access chamber 16. Filament 1
7 is applied with a filament voltage from a second voltage supply source 18 between one end of the filament 17 and an arc voltage from a third voltage supply source 19 between the one end of the filament 17 and the arc chamber 16. 16 is supplied with an arc current from a current supply source 20.

[0006] For example, Ar gas is introduced into the arc chamber 16 from the gas introduction unit 21. For example, while introducing Ar gas into the arc chamber 16,
When a predetermined voltage is applied to the arc chamber 16 and the filament 17, plasma is generated inside the arc chamber 16, and electrons contained in the generated plasma are supplied into the guide tube 12 with a certain energy distribution. You.

The above-described guide tube 12, the first
Voltage supply 13, arc chamber 16, filament 17, second voltage supply 18, third voltage supply 1
9. An electron supply system 2 for supplying electrons to the wafer 11 by the current supply source 20 and the gas introduction unit 21
The electron 23 supplied to the inside of the guide tube 12 from the arc chamber 16 is attracted to the ion beam 14 of positive polarity and distributed around the ion beam 14, and together with the ion beam 14. Irradiation is performed on the wafer 11. Electrons that have not been captured around the ion beam 14 are also attracted to the wafer 11 by the electric field generated between the guide tube 12 and the wafer 11 and are irradiated on the wafer 11.

[0008]

SUMMARY OF THE INVENTION However, the present inventors have proposed that the wafer 1
When ion implantation was performed on the gate electrode formed in No. 1, there was a problem that as the thickness of the gate oxide film became smaller, the breakdown rate of the gate oxide film became higher.

FIGS. 11 (a) and 11 (b) show the above-mentioned conventional wireless communication system.
MOS with antenna effect by using pure substance introduction device
When ion implantation is performed on the gate electrode of a transistor
3 shows the relationship between the thickness of the gate oxide film and the breakdown rate.
Here, the antenna effect refers to the actual area of the gate electrode.
Larger than the area of the gate electrode formed on the transistor
In this case, the charge and electrons of the ions are given to the gate oxide film.
Means that the electrical effect becomes larger than it actually is.
FIG. 11A shows an ion implantation into a p-type semiconductor substrate.
FIG. 11B shows an n-type semiconductor substrate.
This shows a case where ions are implanted into the plate. This place
In this case, the conditions for ion implantation are as follows: ion species: As ⁺, Ionic
Acceleration energy: 20 keV, ion implantation amount: 5 × 1
0^Fifteen/ Cm ^Two, Beam current amount: 10 mA. Also,
The structure of the MOS transistor is based on the surface of the gate insulating film.
The product is 1 × 10^-6mm^TwoAnd the area of the gate electrode is 1 ×
10 ^-1mm^TwoAnd the antenna ratio is 1 × 10^FiveIt is.

In FIGS. 11A and 11B, the horizontal axis represents the gate oxide film thickness (Gate Oxide Thickness).
The vertical axis has an antenna effect and the withstand voltage of the gate oxide film is 8
MOS transistor breakdown rate (Pe
rcentage Of Breakdown). FIG.
(A) and (b) also show the results when the electron supply amount (Electron Flux) by the electron supply system is changed, and the electron supply amounts (0.5, 1.0, 1.5, 2.0) are:
The supply amount of electrons under standard conditions is normalized to 1. From FIGS. 11A and 11B, even if the supply amount of the electrons 23 supplied by the electron supply system 22 is the same,
It can be seen that as the thickness of the gate oxide film decreases, the rate of destruction of the gate oxide film increases.

In view of the above, it is an object of the present invention to prevent the breakdown rate of a gate insulating film from increasing even if the thickness of the gate insulating film is reduced.

[0012]

In order to achieve the above-mentioned object, an impurity introducing apparatus according to the present invention is a method for introducing an impurity having a charge into an object to be processed comprising a semiconductor substrate or a film formed on the semiconductor substrate. Impurity introduction means for introduction, electron supply means for supplying electrons for canceling the charge of impurities in the object to be processed, and control means for controlling the maximum energy of the electrons supplied by the electron supply means to a predetermined value or less. Have.

According to the impurity introducing apparatus of the present invention, since the control means for controlling the maximum energy of the electrons supplied by the electron supply means to a predetermined value or less is provided, the object to be processed or the object to be processed is formed. Negative charge-up in the semiconductor substrate is prevented.

In the impurity introducing apparatus of the present invention, the impurity introducing means is preferably a means for implanting ions as impurities.

In the impurity doping apparatus of the present invention, an insulating film having a thickness of t (nm) is formed on the semiconductor substrate, and the predetermined value is preferably 2 t (eV).

It is preferable that the impurity introducing apparatus of the present invention further includes an energy measuring means for measuring the energy of electrons supplied by the electron supplying means.

In this case, it is preferable that the energy measuring means has means for measuring the maximum energy of the electrons supplied by the electron supplying means.

Preferably, the energy measuring means causes the control means to control the maximum energy of the electrons supplied by the electron supply means to a predetermined value or less based on the measured energy of the electrons.

According to the impurity doping method of the present invention, there is provided an impurity introducing step of introducing an impurity having a charge into a semiconductor substrate or an object formed of a film formed on the semiconductor substrate; An electron supply step of supplying electrons for canceling the electric charges held therein, wherein the electron supply step includes a step of controlling the maximum energy of the supplied electrons to a predetermined value or less.

According to the impurity doping method of the present invention, since the electron supply step includes the step of controlling the maximum energy of the supplied electrons to a predetermined value or less, the object to be processed or the semiconductor on which the object to be processed is formed Negative charge-up on the substrate is prevented.

In the impurity introducing method of the present invention, the impurity introducing step preferably includes a step of implanting ions as impurities.

In the impurity doping method of the present invention, an insulating film having a thickness of t (nm) is formed on the semiconductor substrate, and the predetermined value is preferably 2 t (eV).

It is preferable that the method for introducing impurities according to the present invention further includes an energy measuring step for measuring energy of electrons supplied in the electron supplying step.

In this case, the energy measuring step preferably includes a step of measuring the maximum energy of electrons supplied in the electron supplying step.

The energy measuring step preferably includes a step of controlling the maximum energy of the electrons supplied in the electron supplying step to a predetermined value or less based on the measured energy of the electrons.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus for introducing impurities according to an embodiment of the present invention will be described with reference to FIG. The impurity introduction device according to one embodiment includes a substrate holding table 1
This is an apparatus for introducing impurities into the wafer 101 held at 00. The type of electron supply system provided in the impurity introduction device is not limited, but here, a system that irradiates electrons generated from plasma onto the orbit of the ion beam (Plas
ma Flood System) will be described.

As shown in FIG. 1, a guide tube 102 is provided so as to face a wafer 101 held on a substrate holding table 100. The guide tube 102 has a variable tube bias voltage applied to the guide tube 102. Is connected to a first voltage supply source 103 for supplying
The magnitude of the tube bias voltage supplied from the first voltage supply source 103 depends on the tube bias controller 1
04.

An arc chamber 105 is provided on the side of the guide tube 102, and a filament 106 is provided inside the access chamber 105. A filament voltage is applied to both ends of the filament 106 from a second voltage supply 107, and an arc voltage is applied between one end of the filament 106 and the arc chamber 105 from a third voltage supply 108.

A current supply source 109 for variably applying an arc current to the arc chamber 105 is connected to the arc chamber 105. The amount of the arc current supplied from the current supply source 109 is the arc current. It is controlled by the controller 110.

The substrate holding table 100 is provided with electronic parameter detecting means 111 for detecting the energy and supply amount of electrons applied to the wafer 101. The electronic parameter detection unit 111 includes a voltage variable power supply 112 that applies a voltage to the substrate holding table 100 and thus the wafer 101 while changing the voltage value, and an ammeter 113 that detects an amount of current flowing through the substrate holding table 100 and thus the wafer 101. , The voltage value supplied from the voltage variable power supply 112 and the ammeter 113
Voltage controller 1 that controls the voltage value supplied from voltage variable power supply 112 based on the amount of current detected by
14

For example, Ar gas is introduced into the arc chamber 105 from the gas introduction unit 116. For example, Ar gas is introduced into the arc chamber 105, and the arc chamber 105 and the filament 106 are introduced.
When a predetermined voltage is applied to each of the electrodes, plasma is generated inside the arc chamber 105, and electrons contained in the generated plasma are supplied into the guide tube 102 with a certain energy distribution.

As described above, the guide tube 102, the first voltage supply source 103, the tube bias controller 104, the arc chamber 105, and the filament 10
6, the second voltage supply 107, the third voltage supply 10
8, current supply source 109, arc current controller 11
0, electronic parameter detection means 111 and gas introduction unit 11
6 constitutes an electron supply system 117.
Supplied to the inside of the guide tube 10 are attracted to the ion beam 119 having a positive polarity and are irradiated on the wafer 101 together with the ion beam 119.
The electric field generated between the wafer 2 and the wafer 101 causes the wafer 10
1 and irradiates the wafer 101.

When the arc current flowing between the arc chamber 105 and the filament 106 increases, the density of the plasma generated inside the arc chamber 105 increases, and the amount of the electrons 118 supplied to the guide tube 102 also decreases. More. In addition, guide tube 1
When the tube bias voltage applied to 02 is increased,
The energy distribution of the electrons 118 supplied to the guide tube 102 shifts to a higher energy side.

FIG. 2 (a) shows the energy distribution of electrons when the arc current is changed. In FIG. 2 (a), the horizontal axis represents the electron energy (Electron Enery), and the vertical axis represents the supply of electrons. It represents the quantity (Electron Flux). Arrow A indicates the maximum value of the electron energy when the arc current is 0.5 A, arrow B indicates the maximum value of the electron energy when the arc current is 1 A, and arrow C indicates the maximum value when the arc current is 2 A. It shows the maximum value of the electron energy. The possible reasons for this are arrows A, B,
This is because the area on the right side of C is considered to be noise.

FIG. 2B shows the energy distribution of electrons when the tube bias voltage is changed. In FIG. 2B, the horizontal axis represents the energy of electrons, and the vertical axis represents the amount of supplied electrons. Is represented. Arrow A indicates the maximum value of the electron energy when the tube bias voltage is 0 V, and arrow B indicates the negative value of the tube bias voltage.
The maximum value of the electron energy at 5 V is shown, and the arrow C indicates the maximum value of the electron energy at a tube bias voltage of -10 V. The reason for such consideration is that the area on the right side of the arrows A, B, and C is considered to be noise.

As can be seen from FIG. 2A, when the arc current increases, the total supply amount of electrons increases and the maximum value of the electron energy shifts to the higher energy side. Also, as can be seen from FIG. 2B, when the tube bias voltage is reduced (-10 V is lower than 0 V), the maximum value of the electron energy shifts to the higher energy side.

Therefore, by changing the arc current amount and the tube bias voltage, it is possible to change the maximum value of the energy of the electrons applied to the wafer and the total supply amount of the electrons.

Here, a method for measuring the energy and supply amount of electrons supplied by the electron supply system 117 will be described with reference to FIG.

The ammeter 113 measures the total amount of the amount of electrons injected into the wafer 101 from the ion beam 119 and the amount of electrons introduced into the wafer 101 after being supplied from the arc chamber 105 to the guide tube 118. Measure.

From the variable voltage power supply 112 to the substrate holder 100
When the applied voltage applied to the substrate is increased, electrons having energy lower than the applied voltage cannot reach the substrate holding table 100, so that the amount of current measured by the ammeter 113 decreases.

Therefore, the amount of current flowing through the ammeter 113 is measured while increasing the voltage applied to the substrate holder 100 at predetermined intervals. That is, the current amount corresponding to the predetermined applied voltage value is measured. Then, the amount of electrons corresponding to the predetermined energy range can be calculated from the amount of current corresponding to the predetermined applied voltage value.

FIG. 4A shows ion implantation conditions of ion species: As ⁺ and ion acceleration energy: 20 ke.
V, beam current amount: 10 mA, arc current amount: 1 A, and electron energy (Electron Energ) when performing ion implantation while changing the tube bias voltage.
y) and the supply amount of electrons (Electron Flux). FIG. 4B shows the ion implantation conditions.
Ion species: As ⁺ , ion implantation energy: 20 ke
V, the beam current amount: 10 mA, and the tube bias voltage value: 0 V, showing the relationship between the energy of electrons and the supply amount of electrons when performing ion implantation while changing the amount of arc current.

As can be seen from FIG. 4A, as the tube bias voltage becomes lower, the peak energy (the electron energy at which the supply amount of electrons becomes maximum: the energy of the electrons when the value on the vertical axis becomes maximum) ) And the maximum value of the energy of the supplied electrons (the intersection between the energy distribution graph and the horizontal axis) are all shifted to the higher energy side. The supply amount of electrons at the peak energy is highest when the tube bias voltage is −5 V,
The total amount of supplied electrons (integral value of the amount of electrons) is almost constant.

As can be seen from FIG. 4B, as the amount of arc current increases, both the maximum energy and the total supply amount of electrons increase.

Hereinafter, while changing the arc current amount and the tube bias voltage to change the maximum value of the energy of the electrons applied to the wafer and the total supply amount of the electrons, the impurity is added to the gate electrode of the MOS transistor having the antenna effect. The destruction rate of the gate oxide film when ions are implanted will be examined. The conditions for ion implantation are as follows:
As ⁺ , ion acceleration energy: 20 keV, ion implantation amount: 5 × 10 ¹⁵ / cm ² , beam current amount: 10 m
A. The MOS transistor having an antenna effect used for ion implantation has p-type and n-type substrates, an area of a gate insulating film of 1 × 10 ⁻⁶ mm ² , and an area of a gate electrode of 1 × 10 ^{−6. -1} mm ² and the antenna ratio is 1 × 10 ⁵ .

FIG. 5A shows that an arc current is applied to a gate oxide film having a thickness of 5.0 nm formed on a p-type semiconductor substrate under the conditions of a tube bias voltage of 0 V and a beam current of 10 mA. It shows the relationship between the arc current (Arc Current) and the breakdown rate of the gate oxide film (Percentage Of Breakdown) when ion implantation is performed while changing. FIG. 5B shows that the arc current was changed on a 5.0-nm thick gate oxide film formed on an n-type semiconductor substrate under the conditions of a tube bias voltage of 0 V and a beam current of 10 mA. The graph shows the relationship between the arc current and the breakdown rate of the gate oxide film when performing the ion implantation while performing the ion implantation.

As can be seen from FIGS. 5A and 5B,
As the arc current increases, the breakdown rate of the gate oxide film increases. Therefore, considering this characteristic together with the characteristic that when the arc current increases, the total supply amount of electrons increases and the maximum value of the energy of electrons shifts to the high energy side, the total supply amount of electrons is considered. It can be seen that the breakdown rate of the gate oxide film increases as the value increases or the maximum value of the electron energy shifts to the higher energy side.

FIG. 6A shows that a tube bias voltage is applied to a gate oxide film having a thickness of 5.0 nm formed on a p-type semiconductor substrate under the conditions of an arc current of 1 A and a beam current of 10 mA. It shows the relationship between the tube bias (Tube Bias) and the gate oxide film breakdown rate (Percentage Of Breakdown) when ion implantation is performed while changing the ion implantation. FIG. 6B shows that the tube bias voltage was changed under the conditions of an arc current of 1 A and a beam current of 10 mA on a gate oxide film having a thickness of 5.0 nm formed on an n-type semiconductor substrate. The relationship between the tube bias and the destruction rate of the gate oxide film when the ion implantation is performed while performing the ion implantation is shown.

As can be seen from FIGS. 6A and 6B,
Tube bias voltage becomes lower (-15V than 0V)
Is lower. ), The rate of destruction of the gate oxide film increases. Therefore, considering this characteristic and the characteristic that the maximum value of the electron energy shifts to the high energy side as the tube bias voltage decreases, the maximum value of the electron energy shifts to the high energy side. It can be seen that the shift increases the breakdown rate of the gate oxide film.

Therefore, FIGS. 5A and 5B and FIG.
As described with reference to (a) and (b), when the total supply amount of electrons increases or the maximum value of the energy of electrons shifts to the higher energy side, the breakdown rate of the gate oxide film may increase. I understand.

The relationship between the maximum value of the energy of electrons and the destruction rate of the gate oxide film will be discussed below.

FIG. 7 shows that the thickness of the gate oxide film is 3.5 nm.
And 5.0 nm, the maximum value of the energy of the electrons supplied by the electron supply system (Max El)
ectron Energy) and the gate oxide breakdown rate (Percenta
ge Of Breakdown). As can be seen from FIG. 7, the breakdown rate of the gate oxide film increases as the maximum value of the electron energy increases. Also, from FIG. 7, when the thickness of the gate oxide film is 5.0 nm, 10
Irradiation with electrons having an energy of eV destroys the gate oxide film and reduces the thickness of the gate oxide film to 3.5 nm.
In this case, it can be seen that the gate oxide film is destroyed when irradiated with electrons having an energy of 7 eV.

Next, the substrates are p-type and n-type, the area of the gate insulating film is 1 × 10 ⁻⁶ mm ² , the area of the gate electrode is 1 × 10 ⁻¹ mm ² , and the antenna ratio is 1 × 10
^With respect to the gate oxide film of the MOS transistor having the antenna effect of ⁵ , the ion species: As ⁺ , the ion acceleration energy: 2 while changing the thickness of the gate oxide film.
The ion implantation is performed under the conditions of 0 keV, ion implantation amount: 5 × 10 ¹⁵ / cm ² , and beam current: 10 mA. Investigated the relationship.

FIG. 8 shows the thickness of the gate oxide film (Gate Oxide).
Thickness) and the maximum value of the electron energy (Max Electron Energy) destroyed by the gate oxide film. FIG. 8 shows that the maximum value of the energy is almost 2 (e).
It can be seen that the gate oxide film is destroyed when (V / nm) × t (nm) = 2t (eV), that is, electrons having an energy of 2t (eV) destroy the gate oxide film.

From the above results, it can be seen that the negative charge-up of the gate oxide film due to the irradiation of electrons depends on the maximum energy of the electrons irradiated to the gate oxide film. Therefore, it can be seen that when the maximum energy of the irradiated electrons is controlled to a certain predetermined value or less, the charge-up of the gate oxide film can be suppressed.

The relationship between the supply amount of electrons and the breakdown rate of the gate oxide film will be discussed below. That is, the maximum energy of the electrons supplied by the electron supply system was set to a predetermined value or less, and the supply amount of the electrons was changed to examine the destruction state of the gate oxide film.

The substrates are p-type and n-type, the area of the gate insulating film is 1 × 10 ⁻⁶ mm ² , the area of the gate electrode is 1 × 10 ⁻¹ mm ² , and the antenna ratio is 1 × 10 ^−6. While changing the thickness of the gate oxide film with respect to the gate oxide film of the MOS transistor having the antenna effect of ⁵ ,
Ion species: As ⁺ , ion acceleration energy: 20 ke
V, ions were implanted under the conditions of an ion implantation amount of 5 × 10 ¹⁵ / cm ² and a beam current of 10 mA, and the relationship between the electron supply amount and the gate oxide film breakdown rate was examined.

FIG. 9 shows the amount of supplied electrons (Electron Flux).
And the gate oxide film breakdown rate (Percentage Of Breakdown)
), And 0, 5, 10, 1 on the horizontal axis.
5, 20, 25, and 30 indicate the amount of supplied electrons, and the value in parentheses is the apparent amount of current on the wafer, that is, the sum of the amount of supplied electrons and the amount of beam current supplied by the electron supply system. A value (a positive value of the current amount, the supply amount of electrons becomes a negative value, and therefore, actually, the amount of beam current-the supply amount of electrons). From FIG. 9, when the supply amount of electrons is small, that is, when the supply amount of electrons is 10 mA or less (when the apparent current amount is 0 mA or more),
Destruction of the gate insulating film occurs, and the amount of supplied electrons is 10
When the current exceeds mA (when the apparent current amount is smaller than 0 mA), the gate oxide film hardly breaks down, and even when the electron supply amount becomes 30 mA, the gate oxide film breaks down. It turns out that it hardly happens.

From this, it is considered that the breakdown of the gate oxide film is caused by the charge-up caused by the positive charge of the ion beam, regardless of the supply amount of electrons.

From the above description, (1) the charge-up of the gate oxide film depends on the maximum energy of the electron irradiated on the gate oxide film, and (2) the maximum energy of the electron is
If it is about 2 t (eV) or less, the charge up of the gate oxide film does not occur. (3) If there is supplied enough electrons to neutralize the beam current, the charge up of the gate oxide film does not occur. And (4) It can be seen that charge-up does not occur in the gate oxide film even if the supply amount of electrons increases, as long as the electrons have a maximum energy that does not cause charge-up in the gate oxide film.

Therefore, by adjusting the arc current of the electron supply system and the bias voltage of the guide tube to set the maximum energy of the supply electrons to a predetermined value or less determined by the thickness of the gate oxide film, the negative charge Destruction of the gate oxide film due to the up can be suppressed.

In the actual device manufacturing process, when the thickness of the gate oxide film is t (nm), the maximum energy of the supplied electrons is 2 (eV / nm) ×
When t (nm) is about 2 t (eV) or less, the gate oxide film can be prevented from being broken due to negative charge-up.

The conventional ion implantation apparatus does not have a function of measuring the energy of electrons and the amount of supplied electrons during ion implantation and before and after ion implantation. For this reason, it was not possible to know the energy of the electrons during the ion implantation. Also, since the energy and supply amount of electrons were not known, it was not possible to cope with a change in the supply amount of electrons caused by a change in the state of the ion implanter, so that breakdown due to charge-up of the gate oxide film could occur. There was sex.

However, according to the impurity introducing device according to the present embodiment, the electronic parameter detecting means 111 including the variable voltage power supply 112, the ammeter 113 and the wafer voltage controller 114, and the tube supplied from the first voltage supply source 103 Since it has the tube bias controller 104 for controlling the magnitude of the bias voltage and the arc current controller 110 for controlling the amount of arc current supplied from the current supply source 109, the electron supply system supplies Since the maximum energy can be controlled to a predetermined value or less, destruction due to charge-up of the gate oxide film can be reliably prevented.

The operation of the electronic parameter detecting means 111, the operation of the tube bias controller 104 and the operation of the arc current controller 110, and the reason why the gate oxide film can be reliably prevented from being damaged by negative charge-up according to the present embodiment will be described below. I do.

First, before performing ion implantation, the substrate holding table 100 is irradiated with an ion beam and electrons under the same conditions as those for performing ion implantation. In this case, if the applied voltage applied from the variable voltage power supply 112 is increased, electrons having energy lower than the applied voltage cannot reach the substrate holding table 100, so that the current value detected by the ammeter 113 decreases. Go. Therefore, the voltage variable power supply 112
The current value corresponding to each applied voltage is calculated by measuring the current value with the ammeter 113 while increasing the applied voltage to be applied at predetermined intervals, and each energy range is calculated based on the current value corresponding to each applied voltage. Is calculated. At this time, the total supply amount of electrons is calculated by calculating the integral value of the amount of electrons in each energy range, and the maximum value of the energy of electrons is calculated.

Next, the maximum energy of the electrons supplied by the electron supply system 117 is higher than a predetermined energy at which the gate oxide film is destroyed, which is determined by the thickness of the gate oxide film of the device to be ion-implanted. In the case, the wafer voltage controller 114 to the tube bias controller 104 and the arc current controller 1
10 to output a control signal to the first voltage supply 1
03, the magnitude of the tube bias voltage supplied from the current supply source 103 and the current value of the arc current supplied from the current supply source 109 are reduced.

By repeating the above operation until the maximum energy of the electrons supplied by the electron supply system 117 becomes equal to or less than a predetermined energy (the maximum energy of the electrons that does not damage the gate oxide film), the operation of the gate oxide film is repeated. Prevent destruction due to charge-up.

In this case, the wafer voltage controller 114
Has a function of inputting the thickness of the gate oxide film of the device to be ion-implanted, the wafer voltage controller 114
4 and the arc current controller 110, the control signal can be repeatedly output until the maximum energy of the electrons becomes equal to or less than the predetermined energy, so that the breakdown due to the charge-up of the gate oxide film is automatically prevented. be able to.

In the above embodiment, the ion implantation conditions are as follows: ion species: As ⁺ , ion acceleration energy: 20 keV, ion implantation amount: 5 × 10 ¹⁵ / cm
^{2. A} beam current value of 10 mA was adopted, but the ion implantation conditions are not limited to these, and the ion species, ion acceleration energy, ion implantation amount, and beam current value can be changed as appropriate.

In the above embodiment, a MOS transistor having an antenna effect is used as a device for measuring a breakdown rate of a gate oxide film due to charge-up. Is not limited.

Further, in the above embodiment, the parameters of the arc current and the tube bias voltage are
Although the energy and the supply amount of the electrons supplied by the electron supply system can be controlled, the present invention controls the energy and the supply amount of the electrons supplied by the electron supply system by parameters other than the arc current and the tube bias voltage. It can be applied even when it can be controlled.

The electron supply system may be any other than a system that irradiates electrons generated from plasma onto the trajectory of an ion beam, as long as it is an electron supply system that can control parameters for controlling the energy of electrons.

[0074]

According to the impurity introducing apparatus of the present invention, since the control means for controlling the maximum energy of the electrons supplied by the electron supply means to a predetermined value or less is provided,
It is possible to prevent negative charge-up of the object to be processed or the semiconductor substrate on which the object to be processed is formed.

In the impurity introducing apparatus of the present invention, when the impurity introducing means is a means for implanting ions as impurities, negative charge-up during ion implantation can be prevented.

In the impurity introducing apparatus of the present invention, an insulating film having a thickness of t (nm) is formed on the semiconductor substrate, and when the predetermined value is 2 t (eV), the insulating film has a negative charge-up. Can be prevented from being destroyed.

When the impurity introducing device of the present invention includes the energy measuring means, the energy of the electrons supplied by the electron supplying means can be known.

In this case, if the energy measuring means has means for measuring the maximum energy of the electrons supplied by the electron supply means, the maximum energy of the electrons supplied by the electron supply means is controlled to a predetermined value or less. It becomes easier to do.

Further, when the energy measuring means controls the control means to control the maximum energy of the electrons supplied by the electron supply means to a predetermined value or less based on the measured energy of the electrons, the electron supplied by the electron supply means Can be automatically controlled to a predetermined value or less.

According to the method for introducing impurities according to the present invention,
Since the electron supply step includes a step of controlling the maximum energy of electrons to be supplied to a predetermined value or less, a negative charge-up in the object to be processed or the semiconductor substrate on which the object to be processed is formed can be prevented.

In the impurity introducing method of the present invention, when the impurity introducing step includes the step of implanting ions as impurities, negative charge-up in the ion implanting step can be prevented.

In the method of introducing impurities according to the present invention, an insulating film having a thickness of t (nm) is formed on a semiconductor substrate, and when the predetermined value is 2 t (eV), the insulating film has a negative charge-up. Can be prevented from being destroyed.

If the method for introducing impurities according to the present invention includes an energy measuring step, the energy of electrons supplied in the electron supplying step can be known.

In this case, if the energy measuring step includes a step of measuring the maximum energy of electrons supplied in the electron supply step, it is easy to control the maximum energy of electrons supplied in the electron supply step to a predetermined value or less. Become.

Further, if the energy measuring step includes a step of controlling the maximum energy of the electrons supplied in the electron supply means step to a predetermined value or less based on the measured energy of the electrons, the electron supplied in the electron supplying step Can be automatically controlled to a predetermined value or less.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of an impurity introduction device according to an embodiment of the present invention.

2A is a characteristic diagram showing an electron energy distribution when an arc current is changed, and FIG. 2B is a characteristic diagram showing an electron energy distribution when a tube bias voltage is changed. .

FIG. 3 is a diagram illustrating a method for measuring the energy and supply amount of electrons supplied by an electron supply system.

4A is a characteristic diagram showing the relationship between the energy of electrons and the supply amount of electrons when ion implantation is performed while changing the tube bias voltage, and FIG. FIG. 4 is a characteristic diagram showing a relationship between electron energy and electron supply amount when performing ion implantation while performing ion implantation.

5A is a characteristic diagram showing a relationship between an arc current amount and a breakdown rate of a gate oxide film when ion implantation is performed while changing an arc current, and FIG. FIG. 4 is a characteristic diagram showing a relationship between an arc current amount and a gate oxide film breakdown rate when ion implantation is performed while performing ion implantation.

FIG. 6A is a characteristic diagram showing a relationship between a tube bias voltage and a gate oxide film destruction rate when ions are implanted into a p-type semiconductor substrate while changing a tube bias voltage, and FIG. () Is a characteristic diagram showing the relationship between the tube bias voltage and the breakdown rate of the gate oxide film when ions are implanted into an n-type semiconductor substrate while changing the tube bias voltage.

FIG. 7 is a characteristic diagram showing a relationship between a maximum value of energy of electrons supplied by an electron supply system and a breakdown rate of a gate oxide film.

FIG. 8 is a characteristic diagram showing the relationship between the thickness of a gate oxide film and the maximum value of the energy of electrons that are destroyed by the gate oxide film.

FIG. 9 is a characteristic diagram showing a relationship between an electron supply amount and a breakdown rate of a gate oxide film.

FIG. 10 is a diagram showing an overall configuration of a conventional impurity introduction device.

11A is a characteristic diagram showing a relationship between the thickness of a gate insulating film and a destruction rate when ion implantation is performed on a p-type semiconductor substrate, and FIG. FIG. 4 is a characteristic diagram illustrating a relationship between a thickness of a gate insulating film and a destruction rate when ion implantation is performed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 substrate holder 101 wafer 102 guide tube 103 first voltage supply source 104 tube bias controller 105 arc chamber 106 filament 107 second voltage supply source 108 third voltage supply source 109 current supply source 110 arc current controller 111 electronic parameter Detecting means 112 Variable voltage power supply 113 Ammeter 114 Wafer voltage controller 116 Gas introduction unit 117 Electron supply system 118 Electron 119 Ion beam

Claims (12)

[Claims] An impurity introducing means for introducing an impurity having a charge into a semiconductor substrate or a workpiece formed of a film formed on the semiconductor substrate, and an impurity introducing means for canceling the charge of the impurity on the workpiece. An impurity introduction device, comprising: an electron supply unit that supplies electrons; and a control unit that controls a maximum energy of electrons supplied by the electron supply unit to a predetermined value or less. 2. The impurity introducing apparatus according to claim 1, wherein said impurity introducing means is means for implanting ions as said impurities. 3. The impurity according to claim 1, wherein an insulating film having a thickness of t (nm) is formed on the semiconductor substrate, and the predetermined value is 2 t (eV). Introducing device. 4. The apparatus according to claim 1, further comprising energy measuring means for measuring energy of electrons supplied by said electron supplying means. 5. The impurity introducing apparatus according to claim 4, wherein said energy measuring means has means for measuring a maximum energy of electrons supplied by said electron supplying means. 6. The energy measuring device according to claim 1, wherein the control device controls the maximum energy of the electrons supplied by the electron supply device to a predetermined value or less based on the measured energy of the electrons. 5. The apparatus for introducing impurities according to item 4. 7. An impurity introducing step of introducing an impurity having a charge into a semiconductor substrate or a workpiece formed of a film formed on the semiconductor substrate, and a step of canceling the charge of the impurity on the workpiece. An electron supply step of supplying electrons, wherein the electron supply step includes a step of controlling the maximum energy of the supplied electrons to a predetermined value or less. 8. The method according to claim 7, wherein said impurity introducing step includes a step of implanting ions as said impurities. 9. The impurity according to claim 7, wherein an insulating film having a thickness of t (nm) is formed on the semiconductor substrate, and the predetermined value is 2 t (eV). How to introduce. 10. The method according to claim 7, further comprising an energy measuring step of measuring energy of electrons supplied in the electron supplying step. 11. The method according to claim 10, wherein the energy measuring step includes a step of measuring a maximum energy of electrons supplied in the electron supplying step. 12. The method according to claim 10, wherein the energy measuring step includes a step of controlling the maximum energy of the electrons supplied in the electron supplying step to a predetermined value or less based on the measured energy of the electrons. An apparatus for introducing impurities as described above.