JP2000068226A - Ion implanting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further reduce fluctuations of a load on a swing motor, and to highly precisely operate the mechanical scanning of a holder and a wafer by generating a balancing torque in consideration of the angle from the level line of an arm and the injection angle of ion beams to a wafer from a counter balancer. SOLUTION: An angle from the level line of an arm 22 is α, the implanting angle for ion beams 2 is β, the total weight of the arm 22 and articles (that is, a wafer 6, holder 8, twist motor 24, and vacuum seal part 26) which rotate with this is W, and a distance from a center of gravity G of the total weight to a rotational central axis 22a of the arm 22 is L. Then, a balancing torque F expressed by F=L.Wcosβcosα or a substantially equivalent relation is generated within the angular range of the arm 22 operating ion implantation to at least the wafer 6 from a counter balancer 30a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called hybrid scanning system in which an ion beam is electrically scanned and a holder is mechanically scanned together with a wafer by a swing arm in a direction substantially orthogonal to an ion beam scanning direction. The present invention relates to an ion implantation apparatus having a compressed air type counterbalancer for reducing a load torque applied to a swing motor, and more specifically to a means for more precisely balancing the counterbalancer.

[0002]

2. Description of the Related Art An example of this type of ion implantation apparatus is disclosed in Japanese Patent Publication No. 7-123434. It is summarized and described below.

As shown in FIGS. 2 and 3, this ion implantation apparatus electrically scans an ion beam 2 traveling in a Z direction in a certain direction (X direction in this example) and guides the ion beam 2 into an implantation chamber 4. In addition, the apparatus is configured to mechanically scan the wafer 6 in a Y direction (for example, the Y direction or the Y ′ direction shown in FIG. 6) substantially orthogonal to the ion beam scanning direction in the implantation chamber 4. And a holder driving device 10 for mechanically scanning the holder 8 in the injection chamber 4. The X direction is, for example, a horizontal direction, and the Y direction is, for example, a vertical direction.

[0004] In this example, the holder driving device 10 includes a main shaft 14 penetrating the wall surface of the injection chamber 4 in the X direction, and a main shaft 1
Reversible rotary injection angle motor 1 coupled to the outside of the injection chamber 4
6, a reversible rotation type swing motor 18 mounted substantially orthogonal to the interior of the injection chamber of the main shaft 14, an arm 22 mounted substantially orthogonal to the output shaft of the swing motor 18, and an arm 22 And a reversible rotation type twist motor 24 mounted substantially orthogonally to the motor. The holder 8 is mounted substantially orthogonally to the output shaft of the twist motor 24. 12
Is a vacuum seal bearing, and 20 and 26 are vacuum seal portions.

At the time of ion implantation, as shown in FIG. 3, assuming that the angle of the arm 22 from the horizontal is α, the arm 22 is moved by the swing motor 18 around α = 0 °, for example, α = + 35 ° to α. == − 35 °. Thus, the wafer 6 held by the holder 8 is scanned, for example, in the Y direction so as to draw an arc while facing the ion beam 2.

The twist motor 24 is connected to the arm 22
Is used to keep the attitude of the holder 8 and the wafer 6 constant when the wafer is turned as described above. The implantation angle motor 16 is used for changing the implantation angle β of the ion beam 2 with respect to the wafer 6 (see FIG. 6).

The torque caused by the weight of the arm 22 and the like when the arm 22 is turned as described above is indicated by a curve A in FIG. The torque becomes sin curve, if none measures are taken, this is because it will load torque applied to the swing motor 18, the maximum large load torque of T ₁ in takes the swing motor 18.
In this case, when the arm 22 is turned from the horizontal (α = 0 °) in the downward direction (the direction of −35 °), a negative load is applied to the swing motor 18 and the upward direction (+35)
(In the direction of °), a positive load is applied.

Therefore, in this state, the swing motor 18
Is very large and it is difficult to rotate the arm 22 smoothly. Therefore, it is difficult to perform the mechanical scanning of the holder 8 and the wafer 6 with high accuracy, and the uniformity of ion implantation to the wafer 6 is deteriorated. There is a problem of doing.

To solve this problem, a compressed air type counter balancer 30 is provided. The counter balancer 30 includes an actuator 40 provided on the opposite side of the swing motor 18 and having an output shaft 49 coupled to a turning center shaft 22a of the arm 22, and a compressed air supply unit 50 for supplying compressed air to the actuator 40. Have.

As shown in FIG. 4, the actuator 40 includes two opposing pneumatic cylinders 42a.
And 42b. Both pneumatic cylinders 42a,
The racks 46 are attached to the pistons 44a and 44b in the rack 42b.
a and 46b are connected to each other, and both racks 4
A common pinion 48 is meshed with 6a and 46b, and the output shaft 49 is connected to this pinion 48.

The compressed air supply section 50 has a compressed air source 52 and a pressure reducing valve 56 in this example. Compressed air from the compressed air supply section 50 is supplied to both pneumatic cylinders 42 a and 42 b of the actuator 40 via a pipe 60. Supplied.

According to the above configuration, when the arm 22 is turned by the swing motor 18 as described with reference to FIG. 3 and the like, the pneumatic cylinders 42a and 42b of the actuator 40 are also linked via the output shaft 49 and the like.

At this time, if compressed air is supplied from the compressed air supply unit 50 to both the pneumatic cylinders 42a and 42b, the movement of the pistons 44a and 44b when the arm 22 (that is, the holder 8) turns downward. Due to this, the volume inside the pneumatic cylinders 42a and 42b decreases and the internal pressure tends to increase, but since the pressure reducing valve 56 operates to keep the pressure on the secondary side constant, the volume compressed by the pistons 44a and 44b Only the compressed air is discharged from the pressure reducing valve 56.

Conversely, when the arm 22 pivots in the ascending direction, the volume in the pneumatic cylinders 42a and 42b increases and the internal pressure tends to decrease. Acts to keep the pressure constant.
The compressed air source 52 via the pressure reducing valve 56 is increased by the increased volume.
Compressed air is supplied into the pneumatic cylinders 42a and 42b.

By such an operation, the balancing torque generated by the counter balancer 30 becomes ideally constant. For example, by appropriately selecting the pressure of the compressed air supplied to both the pneumatic cylinders 42a and 42b, the balancing torque of the counter balancer 30 can be reduced by the straight line B in FIG.
As shown by α, the ion implantation operation range α = + 35 °
The average torque T ₂ of the torque (curve A) by the arm or the like within the range of α = −35 ° can be obtained.

As a result, the load torque applied to the swing motor 18 (ie, the difference between the torque curves A and B) can be reduced, and the capacity and size of the swing motor 18 can be reduced. Further, since the load fluctuation applied to the swing motor 18 becomes small and the movement of the arm 22 becomes smooth,
The mechanical scanning of the holder 8 and the wafer 6 can be performed with high accuracy, and the uniformity of ion implantation on the wafer 6 can be improved.

[0017]

However, the counter balancer 30 still has room for improvement in that the angle α of the arm 22 from the horizontal and the injection angle β with respect to the wafer 6 are not taken into account.

That is, the counter balancer 30 cannot make the balancing torque generated by the counter balancer 30 follow the torque corresponding to the angle α of the arm, as shown in FIG. The torque is fixed to the average torque T ₂ of the torque (curve A) by the arm or the like at α.

Therefore, the load fluctuation on the arm 22 is
Although it is smaller than the case where the counter balancer 30 is not provided, it is still present. Therefore, the holder 8
In addition, there is a limit in performing mechanical scanning of the wafer 6 with high accuracy.

Further, the counter balancer 30 adjusts the implantation angle β of the ion beam 2 with respect to the wafer 6 (see FIG. 6).
Is fixed (usually β = 0 °), and no consideration is given to making the injection angle β variable. However, the implantation angle β is one of the important parameters of ion implantation, and the apparatus shown in FIG.
The injection angle β is made variable by the injection angle motor 16. That is, the injection shaft motor 16 controls
6 by tilting the arm 22 and the like around the center.
As shown in (1), the holder 8 and the wafer 6 are scanned in the Y 'direction inclined at an angle β from the Y direction. In other words, the angle γ between the surface that scans the ion beam 2 (the surface including the X direction in this example) and the surface that scans the holder 8 (the surface including the Y ′ direction) is made variable. , The implantation angle β of the ion beam 2 with respect to the wafer 6 (the normal set on the surface of the wafer 6 and the ion beam 2
The angle formed by the angle is variable. The injection angle β is, for example,
0 degree, 7 degrees, 30 degrees, 45 degrees, 60 degrees and the like are selected.

When β> 0 °, the arm 22 is turned obliquely and turned. Therefore, the above-described load torque applied to the swing motor 18 due to the eccentric load of the arm 22 or the like is larger than when β = 0 °. And also decreases as the injection angle β increases. Simply put cos
It is proportional to β.

Therefore, if a fixed balancing torque is generated from the counter balancer 30 on the basis of one injection angle β, when the injection angle β is changed, the balancing cannot be performed accurately, and the swing cannot be performed. The load fluctuation on the motor 18 cannot be reduced. Therefore, also for this reason, there is a limit in performing mechanical scanning of the holder 8 and the wafer 6 with high accuracy.

Therefore, the present invention reduces the load fluctuation on the swing motor by generating a balancing torque from the counter balancer in consideration of the angle of the arm from the horizontal and the implantation angle of the ion beam with respect to the wafer. A main object is to enable mechanical scanning of a wafer to be performed with higher accuracy.

[0024]

According to the ion implantation apparatus of the present invention, the angle of the arm from the horizontal is α, the implantation angle of the ion beam is β, and the total weight of the arm and the object to be swiveled therewith is W. When the distance from the center of gravity of the total weight to the center axis of rotation of the arm is L, at least within the angular range of the arm for performing ion implantation on the wafer from the counter balancer, the following formula or substantially equivalent thereto is obtained. The balance torque F expressed by the following relationship is generated.

[0025]

[Formula 1] F = L · Wcosβcosα

Under the conditions such as the angle α and the injection angle β, the torque applied to the swing motor is also represented by the above equation (1). Therefore, by generating the balancing torque F represented by the above equation (1) from the counter balancer, An optimum balancing force according to the arm angle α and the injection angle β can be applied to the swing motor. Therefore, the load fluctuation applied to the swing motor is almost eliminated, and the mechanical scanning of the holder and the wafer can be performed with higher accuracy. As a result, the uniformity of ion implantation on the wafer is further improved.

[0027]

FIG. 1 is a view showing an example of an ion implantation apparatus according to the present invention. The same or corresponding parts as those of the above-described conventional example are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

The ion implanter of this embodiment has a counter balancer 30a in place of the conventional counter balancer 30.
It has. The angle of the arm 22 from the horizontal is α, the injection angle of the ion beam 2 is β, and the arm 22 and an object that can be rotated therewith (in this example, the wafer 6, the holder 8, the twist motor 24, and the vacuum seal portion). If the total weight of 26) is W, and the distance from the center of gravity G of the total weight to the rotation center axis 22a of the arm 22 is L, the angle of the arm 22 for ion-implanting at least the wafer 6 from the counter balancer 30a. Within the range (for example, within the range of α = + 35 ° to α = −35 ° described above), the balancing torque F expressed by the above equation 1 or a relation substantially equivalent thereto is generated.

Under the conditions of the angle α and the injection angle β, the torque applied to the swing motor 18 is also represented by the above equation (1). Therefore, the counterbalancer 30a generates the balancing torque F represented by the above equation (1). Thereby, an optimum balancing force according to the angle α of the arm 22 and the injection angle β can be applied to the swing motor 18.

A more specific example of the counter balancer 30a will be described. In this example, the counter balancer 30a has the same actuator 40 and compressed air source 5 as described above.
2, an electro-pneumatic pressure control valve 66 connected between the compressed air source 52 and the actuator 40, a control device 70 for controlling the electro-pneumatic pressure control valve 66, and the angle α of the arm 22. Arm angle detecting means for detecting.

First, the arm angle detecting means will be described. In this example, the drive circuit 78 for driving the swing motor 18 also serves as the detecting means. That is, the injection angle motor 16 and the swing motor 18 are servo motors in this example, and are respectively driven by driving circuits 76 and 78 for driving the injection controller 8 in this example.
Controlled by 0. The angle α of the arm 22 is fed back to the drive circuit 78 from the swing motor 18, and the angle α is supplied from the drive circuit 78 to the injection controller 80 and the control device 70 in this example. Therefore, in this example, the drive circuit 78 also serves as the arm angle detecting means.

Incidentally, in this example, a signal for setting the injection angle β according to the injection recipe (injection condition) is supplied from the injection controller 80 to the drive circuit 76 and the control device 70.
Given to. Further, the injection controller 80 controls the swing motor 18 to control the angular velocity ω of the reciprocating swing of the arm 22 to satisfy the following expression, as disclosed in Japanese Patent Publication No. 7-87083. As a result, the mechanical scanning speed of the wafer 6 becomes proportional to the beam current I of the ion beam 2, so that the ion implantation can be performed uniformly over the entire surface of the wafer without being affected by the fluctuation of the beam current I. Can be. Here, K ₀ is a proportionality constant,
M is the distance between the rotation center axis 22a of the arm 22 and the center 6a of the wafer 6, α is the angle of the arm, and I is the beam current of the ion beam 2.

[0033]

Ω = {K ₀ / (M · cosα)} I

The electropneumatic pressure control valve 66 is of an electropneumatic type, is connected between the compressed air source 52 and the actuator 40, and controls the air pressure P on the actuator 40 side in this example to a control device. It is adjusted to a value proportional to the control voltage V given from 70.

The control device 70 is, for example, a computer. In this example, the injection angle β is set from the storage means 72 and the injection controller 80, and the drive circuit 78
And an arithmetic control means 74 to which the angle α of the arm is given.

Then, when the angle α of the arm 22 is 0 degree, the balancing torque F shown in Expression 1 is applied to the actuator 40.
The control voltage V corresponding to the air pressure P on the actuator 40 side of the electropneumatic pressure regulating valve 66 necessary to generate
(This is referred to as V ₀ in particular) is obtained in advance by experiment or the like for each injection angle β, and is stored in the storage means 72 in a form as shown in Table 1, for example. This control voltage V ₀
Reflects the part other than cos α in Equation 1, that is, L · W cos β.

[0037]

[Table 1]

The operation control means 74 includes the injection controller 8
Injection angle β set from 0 (this is 0 in this case
Degrees, 7 degrees, 30 degrees, 45 degrees, the control voltage V ₀ corresponding to the a) any of the 60-degree removed from the storage means 72, and using the angle α of the arm given from driving circuit 78 The angle α of the arm 22 is calculated by the following equation.
And a control voltage V corresponding to the injection angle β is obtained, and the control voltage V is given to the electropneumatic pressure regulating valve 66.

[0039]

V = V ₀ cosα

As described above, the electropneumatic pressure regulating valve 66 regulates the air pressure P on the actuator 40 side to a value proportional to the control voltage V given from the arithmetic control means 74.

As a result, the air pressure P applied to the actuator 40 from the compressed air source 52 through the electropneumatic pressure control valve 66 can be controlled to the relationship represented by the following equation.

[0042]

## EQU4 ## P∝V = V ₀ cosα = L · Wcosβcosα

The equation (4) is substantially equivalent to the equation (1). As a result, the counterbalancer 30a (specifically, from the actuator 40) generates the balancing torque F represented by the equation (1). Therefore, an optimum balancing force according to the angle α of the arm 22 and the injection angle β can be applied to the swing motor 18. Therefore, the load applied to the swing motor 18 can be greatly reduced, and the load fluctuation is almost eliminated, so that the mechanical scanning of the holder 8 and the wafer 6 can be performed with higher accuracy. Specifically, the control shown in Expression 2 can be performed with higher accuracy. As a result, the uniformity of ion implantation for the wafer 6 is further improved.

In place of the above-described example, an electropneumatic pressure regulating valve necessary for the actuator 40 to generate the balancing torque F shown in Equation 1 when the angle α of the arm 22 is 0 degree. 66, the air pressure P on the actuator 40 side
(This is referred to as P ₀ in particular) may be obtained in advance by experiment or the like for each injection angle β, and may be stored in the storage means 72 in a form as shown in Table 2, for example. As in the case of the control voltage V ₀ , the air pressure P ₀ has
The portion other than sα, that is, L · Wcosβ is reflected.

[0045]

[Table 2]

The injection angle β set by the injection controller 80 by the arithmetic control means 74 (this is also any one of 0 degree, 7 degrees, 30 degrees, 45 degrees, and 60 degrees). the storage means 7 the air pressure P ₀ corresponding to)
2 and using the arm angle α given from the drive circuit 78, the following equation is calculated to obtain the arm 22
The air pressure P corresponding to the angle α and the injection angle β may be obtained, and the air pressure on the actuator 40 side may be controlled to the air pressure P by controlling the electropneumatic pressure control valve 66.

[0047]

## EQU5 ## P = P ₀ cosα

Also by such means, as in the above example, the counterbalancer 30a (specifically, from the actuator 40) generates an optimum balancing force corresponding to the angle α and the injection angle β of the arm 22. It can be added to the swing motor 18.

[0049]

As described above, according to the present invention, the counterbalancer can generate the optimum balancing torque for the angle of the arm from the horizontal and the implantation angle of the ion beam with respect to the wafer, and apply it to the swing motor. Therefore, the load applied to the swing motor can be significantly reduced, and the load fluctuation is almost eliminated. As a result, the mechanical scanning of the holder and the wafer can be performed with higher accuracy, and the uniformity of ion implantation on the wafer can be further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an ion implantation apparatus according to the present invention.

FIG. 2 is a diagram illustrating an example of a conventional ion implantation apparatus.

FIG. 3 is a view of the device of FIGS. 1 and 2 as viewed from the rear side of the arm.

FIG. 4 is a diagram showing a detailed example of a counter balancer in FIGS. 1 and 2;

FIG. 5 is a diagram showing examples of various torques.

FIG. 6 is a diagram illustrating a state of scanning of a holder when an implantation angle is set to be larger than 0 degree, as viewed parallel to an ion beam scanning direction.

[Explanation of symbols]

 2 Ion beam 6 Wafer 8 Holder 10 Holder driving device 16 Injection angle motor 18 Swing motor 22 Arm 30a Counter balancer 40 Actuator 52 Compressed air source 66 Electropneumatic pressure control valve 70 Control device 72 Storage means 74 Operation control means 78 Drive circuit

Claims (3)

[Claims] 1. An ion beam is electrically scanned in a fixed direction, and an arm is reciprocated by a reversible swing motor so that a holder for holding a wafer attached to the arm is moved together with the wafer in the ion beam scanning direction. An ion implantation apparatus configured to mechanically scan in a direction substantially orthogonal to the ion implantation apparatus, comprising an actuator of a compressed air type connected to a pivot axis of the arm and a compressed air source for supplying compressed air to the actuator. A counter balancer of a compressed air type for reducing the load torque applied to the swing motor by generating a balancing force, and the angle between the surface for scanning the ion beam and the surface for scanning the holder is variable. In the ion implantation apparatus, in which the implantation angle of the ion beam with respect to the wafer is variable, Α, the implantation angle of the ion beam is β, the total weight of the arm and the object to be rotated therewith is W, and the distance from the center of gravity of the total weight to the rotation center axis of the arm is L. Wherein the counter balancer generates a balancing torque F represented by F = L · Wcosβcosα or a substantially equivalent relation at least within an angle range of an arm for implanting ions into a wafer. Ion implanter. 2. An arm angle detecting means for detecting an angle α of the arm, an electro-pneumatic pressure control valve connected between the compressed air source and an actuator for adjusting air pressure on an actuator side, and the arm A control device for controlling the electropneumatic pressure regulating valve in accordance with the arm angle α given from the angle detecting means and an injection angle β set from the outside, and the control device further comprises an arm angle storage means for storing the actuator-side air pressure P ₀ required for generating the balancing torque F when α is 0 degrees, obtained for each of a plurality of injection angles β; The air pressure P ₀ corresponding to β is taken out from the storage means, and the arm angle α given from the arm angle detection means
Using, P = P ₀ cos [alpha] comprising calculating a go seek air pressure P corresponding to the angle α and angle of implantation β of the arm, the electro-pneumatic control pressure regulating valve the air pressure P of the air pressure of the actuator side 2. The ion implantation apparatus according to claim 1, further comprising arithmetic control means for fading. 3. An electro-pneumatic type which is connected between the compressed air source and the actuator and adjusts the air pressure on the actuator side to a value proportional to a control voltage, wherein the arm angle detecting means detects the angle α of the arm. A pressure control valve, and a control device for controlling the electro-pneumatic pressure control valve in accordance with an arm angle α given from the arm angle detection means and an injection angle β set from the outside. The control device obtains the control voltage V ₀ corresponding to the air pressure on the actuator side necessary to generate the balancing torque F when the angle α of the arm is 0 degree, for each of a plurality of injection angles β. a storage means for storing, the control voltage V ₀ corresponding to the injection angle β which is set is taken out from the storage unit, and the α angle of the arm given from the arm angle detecting means used Obtains the control voltage V corresponding to the angle α and angle of implantation β of the arm performs V = V ₀ cos [alpha] becomes operational, and a calculation control means for providing the control voltage V to the electro-pneumatic pressure regulating valve The ion implantation apparatus according to claim 1.