JP2012099298A - Ion implanter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion implanter by which desired ion implantation can be achieved without any trouble in the motion of a holder driving mechanism even with a wafer cooled at an ultralow temperature.SOLUTION: The ion implanter comprises: a holder 3 for holding a wafer 2; and a holder driving mechanism having at least a twist angle control mechanism and a tilt angle control mechanism. The ion implanter further comprises: a twist motor forming a driving power source of the twist angle control mechanism, and having a rotor attached to the holder; a housing 20 to which a stator of the twist motor is attached; a cooling flange 5 disposed on the housing 20 to be opposed to the holder 3; a refrigerant tank 8 in which a refrigerant is stored; and a refrigerant supply tube 7 having one end connected to the cooling flange 5, and the other end connected to the refrigerant tank 8. In the ion implanter, the tube 7 is disposed in an area outside the holder driving mechanism.

Description

  The present invention relates to an ion implantation apparatus for irradiating a wafer with an ion beam to form a semiconductor element on the wafer. In particular, the present invention relates to an ion implantation apparatus having a mechanism for cooling a wafer irradiated with an ion beam.

  A wafer (for example, a silicon wafer) is provided with a resist film in order to realize ion implantation into a predetermined region. When ion implantation is performed on the wafer, the temperature of the wafer rises. The degree of this temperature rise varies depending on the ion implantation conditions (values of dose, beam current, etc.) and the type of wafer, but it is desirable because the resist film is thermally deformed when the wafer becomes hot. There has been a problem that ion implantation into the region becomes impossible.

  In order to solve this problem, an ion implantation apparatus having a cooling mechanism for suppressing the temperature rise of the wafer has been conventionally employed. Specifically, as disclosed in Patent Document 1, a coolant flow path is provided in each inner region of a holder rotation shaft that drives a holder that holds a wafer, a holder support arm, and a holder main shaft. A cooling mechanism configured to supply a coolant to the holder through the flow path has been used.

  In general, pure water (about 20 ° C.) is used as a refrigerant used in such a cooling mechanism, and the surface temperature of the wafer during ion implantation is such that the resist film is not deformed (about 100 ° C.). If it was good.

JP-A-64-42577 (FIGS. 1 to 4)

  In recent years, miniaturization of semiconductor elements has progressed, and ion implantation into a very shallow region from the wafer surface is required. As a technique for achieving ion implantation into such a region, the temperature of the wafer during ion implantation is set to a lower temperature (0 ° C. or less, for example, about −60 ° C. to −20 ° C. Attention has been paid to a technique for performing ion implantation into a wafer while maintaining the above.

  A holder driving mechanism for driving a holder such as a holder rotating shaft and a holder support arm, a bearing used in the mechanism, and a member such as a vacuum seal when a cryogenic refrigerant flows in the refrigerant flow path disclosed in Patent Document 1. Cause cooling shrinkage. As a result, rattling occurs when the holder is driven, and the relative positional relationship between the ion beam and the wafer deviates from the initial setting, and desired ion implantation cannot be performed.

  Therefore, in order to solve the above problem, it is conceivable that a tube for supplying the refrigerant is provided outside the holder driving mechanism, and this tube is directly assembled to the holder. By adopting such a configuration, the holder driving mechanism is not contracted by cooling.

  However, in order to perform various ion implantation processes, the ion implantation apparatus is provided on the wafer surface with the normal line to the wafer surface at the center position of the wafer as a rotation axis during or before ion implantation into the wafer. The predetermined reference position is set to 0 degree, and it is required to rotate the wafer (holder for holding the wafer) within a range of about 360 degrees from the position.

  Therefore, if the refrigerant supply tube is short, the rotation of the wafer will be hindered. Therefore, it is necessary to make the tube long and bent to an extent that the wafer can be rotated. Even with the configuration, the following problems still remain.

  When the refrigerant supply tube rotates together with the wafer, the tube may block the ion beam applied to the wafer. When the ion beam is interrupted, the desired ion implantation cannot be performed. In addition, the long bent tube is wound around a mechanism for rotating the wafer, which hinders the operation of rotating the wafer.

  Therefore, the present invention is intended to provide an ion implantation apparatus that can achieve a desired ion implantation without hindering the operation of the holder driving mechanism even when the wafer is cooled at an extremely low temperature. As an issue.

  An ion implantation apparatus according to the present invention comprises a holder for holding a wafer and a holder driving mechanism having at least a twist angle adjusting mechanism and a tilt angle adjusting mechanism, and serves as a drive source for the twist angle adjusting mechanism. , A twist motor having a rotor attached to the holder, a housing to which a stator of the twist motor is attached, a cooling flange disposed at a location of the housing facing the holder, and a refrigerant accumulated. And a refrigerant supply tube having one end connected to the cooling flange and the other end connected to the cooling tank, and the tube is disposed in an outer region of the holder driving mechanism. It is characterized by being.

  As described above, since the cooling flange is provided at the position on the stator facing the holder located on the rotor side, the wafer held by the holder without hindering the rotation of the holder by the holder driving mechanism. Can be cooled. Furthermore, since the refrigerant supply tube is arranged in the outer region of the holder driving mechanism, the holder driving mechanism is not cooled and contracted. Therefore, even when the wafer is cooled at an extremely low temperature, desired ion implantation can be achieved without hindering the operation of the holder driving mechanism.

  In order to improve the cooling efficiency of the wafer, in order to supply a gas to the space sealed by the seal member and the seal member that seals the space between the holder and the cooling flange in the radial direction of the wafer It is desirable to have a gas source.

  If such a structure is employ | adopted, the cold air from a cooling flange will become easy to be transmitted to the holder side with the gas supplied between the cooling flange and the holder.

  Further, in order to further improve the cooling efficiency, a plurality of recesses formed to communicate with each other on the surface of the holder facing the wafer, and an inner region of the holder driving mechanism, A gas introduction flow path connected to at least one; a gas introduction tube having one end connected to the gas source and the other end connected to the gas introduction path; It is desirable to employ a configuration in which the plurality of recesses, the space sealed by the seal member, and the gas introduction path communicate with each other.

  On the other hand, a plurality of recesses formed to communicate with each other on the surface of the holder facing the wafer, the twist angle adjusting mechanism, the twist shaft connected to the holder, and a bearing on the twist shaft A gas introduction member that is attached via a seal and into which gas from the gas source is introduced; and a gas introduction path that communicates with the gas introduction member, the bearing seal, and the twist shaft; It is desirable to employ a configuration in which the plurality of recesses, the space sealed by the seal member, and the gas introduction path communicate with each other. By adopting such a configuration, it is possible not only to expect further improvement in cooling efficiency like the previous configuration, but also to simplify the configuration inside the vacuum vessel.

  In addition, it is desirable that a heat insulating material is provided between the cooling flange and the housing. When such a configuration is used, the heat from the housing side is not transmitted to the cooling flange side, so that the temperature of the cooling flange can be kept low.

  Even when the wafer is cooled at an extremely low temperature, desired ion implantation can be achieved without hindering the operation of the holder driving mechanism.

It is a top view showing the mode in the implantation chamber of the ion implantation system concerning a first embodiment. It is a principal part enlarged view which shows the structure of the housing | casing periphery of FIG. An example of the refrigerant | coolant flow path formed in the cooling flange which concerns on this invention is represented. It is a top view showing the mode in the implantation chamber of the ion implantation system concerning a second embodiment. It is a principal part enlarged view which shows the structure of the cooling flange of FIG. It is sectional drawing of the sealing member of FIG. FIG. 6 is a main part enlarged view showing an example in which the configuration of the holder part is improved in the cooling mechanism shown in FIG. 5. The mode when the holder of FIG. 7 is seen from the Y direction reverse side is represented. It is a top view showing the mode in the implantation chamber of the ion implantation system concerning a third embodiment. It is a principal part enlarged view which shows the structure of the gas introduction member periphery of FIG. It is sectional drawing of the twist axis | shaft containing the gas introduction member of FIG. It is a top view showing the mode in the implantation chamber of the ion implantation system concerning a 4th embodiment.

  In the present invention, for convenience, the long side direction of the ribbon-like ion beam 1 is the X direction, the short side direction of the ribbon-like ion beam 1 and the scanning direction of the wafer 2 crossing the ribbon-like ion beam 1 is the Y direction, and the ribbon shape. The traveling direction of the ion beam 1 is assumed to be the Z direction, and the XYZ directions are orthogonal to each other. Embodiments used in the present invention will be described below with reference to the drawings.

<First embodiment>
FIG. 1 illustrates a state in the implantation chamber of the ion implantation apparatus according to the first embodiment. The injection mechanism shown in this embodiment is called a so-called hybrid scan system.

  In order to perform a desired ion implantation to the wafer 2 such as silicon, a holder 3 (for example, an electrostatic chuck) for holding the wafer 2 is rotated around the A axis and the B axis in FIG. These rotational operations are conventionally known as twist angle adjustment and tilt angle adjustment.

  The A axis is a rotation axis provided at a center position of the wafer 2 in a direction perpendicular to the surface of the wafer 2. By rotating the holder 3 around this axis, the twist angle of the wafer 2 (the notch or orientation flat of the wafer is present). The angle is adjusted from the reference position when the center of the wafer is rotated about the rotation axis.

  On the other hand, the B axis is a rotation axis provided in a direction perpendicular to the A axis. By rotating the holder 3 around this axis, the tilt angle of the wafer 2 (normal line standing on the wafer surface and irradiation to the wafer surface are irradiated). The angle formed by the ion beam to be adjusted is adjusted. In the drawings of the embodiment of the present invention, the B axis is set as an axis parallel to the X direction, but is not limited to this direction. The B axis may be set in a direction perpendicular to the A axis.

  After the twist angle and tilt angle are adjusted in this way, the scan shaft 23 is moved in the direction of arrow C in the figure via the bearing seal 27 by the scan motor 24 provided outside the vacuum vessel 25 (atmosphere side). Slide along. The ribbon-shaped ion beam 1 shown in the figure has a dimension in the X direction longer than the diameter of the wafer 2. Therefore, the wafer 2 indirectly supported by the scan shaft 23 is moved across the ribbon-like ion beam 1 from the top to the bottom or from the bottom to the top in the Y direction. Ion implantation is achieved.

  FIG. 2 is an enlarged view of a main part for explaining the configuration around the casing shown in FIG. FIG. 2 shows a state in which the holder 3 shown in FIG. 1 is rotated around the B axis so that the A axis is just parallel to the Y direction. The twist angle adjustment mechanism and the tilt angle adjustment mechanism will be briefly described with reference to this figure.

  A twist shaft 4 is attached to the lower surface of the holder 3 with screws or the like (not shown). The twist shaft 4 includes a twist motor 17 as a drive source, and the stator side of the twist motor 17 is attached to the housing 20. The twist shaft 4 is supported by a housing 20 via a bearing (not shown) so that the rotation is allowed and the drop in the Y direction is prevented.

  A mechanism for adjusting the twist angle of the wafer 2 in this way is called a twist angle adjusting mechanism. However, this configuration is an example, and the present invention is not limited to this. Various modifications can be considered for details of the mechanism. For example, the belt may be hung on the twist shaft, and the twist shaft may be rotated such that the belt is hung on the rotation shaft of a motor provided at a position far from the twist shaft. In the twist angle adjusting mechanism of the present invention, the power source is a motor, the holder 3 for holding the wafer 2 is provided on the rotor side, and the cooling flange described later is provided on the stator side. The details of the configuration may be anything.

  A tilt shaft 19 is connected to a pair of support arms 21 extending from the base 22. The tilt shaft 19 is inserted into the housing 20 along the B axis. A tilt motor 18 is attached to the tilt shaft 19 arranged on the left side in FIG. 2, and the casing 20 is rotated with respect to the tilt shaft 19 by the tilt motor 18. A bearing (not shown) is provided between the tilt shaft 19 and the housing 20 through which the shaft is inserted.

  A mechanism for adjusting the tilt angle of the wafer 2 in this way is called a tilt angle adjusting mechanism. However, like the twist angle adjusting mechanism, the configuration shown here is an example, and the present invention is not limited to this. The tilt angle adjusting mechanism according to the present invention may have any configuration as long as the power source is a motor and the entire twist angle adjusting mechanism can be rotated.

  Since the ion implantation apparatus described as an embodiment of the present invention is a hybrid scan system, it has a scan shaft 23 and a scan motor 24. However, the dimensions of the ribbon-like ion beam 1 are those of the wafer 2. These members are not necessary if they have dimensions that cover the entire surface. In addition, a member such as a scan axis is not required even in a raster scan type ion implantation apparatus in which ion implantation to the entire surface of the wafer 2 is achieved by scanning a spot-like ion beam by electrostatic or magnetic fields. The present invention can be applied to these types of ion implantation apparatuses.

  Therefore, the holder driving mechanism for driving the holder 3 in the present invention means a mechanism having at least a twist angle adjusting mechanism and a tilt angle adjusting mechanism, and the holder driving mechanism includes the scan shaft 23 and the shaft. Whether or not a scanning mechanism (such as a scan motor 24) that slides is included depends on the size of the ion beam 1 irradiated on the wafer 2 and the scanning method of the ion beam.

  The ion implantation apparatus of the present invention has a cooling flange 5. The cooling flange 5 is attached to the casing 20 described above via a heat insulating material 6 (for example, made of a fluorine-based material). By using such a heat insulating material 6, heat transfer from the housing 20 to which the motors 17 and 18 are attached can be suppressed. However, this heat insulating material is not essential. For example, the heat transfer to the cooling flange 5 may be suppressed using vacuum insulation by reducing the contact area between the cooling flange 5 and the housing 20 or by separating both members.

  As shown in FIG. 2, the cooling flange 5 is attached to the housing 20 at a position facing the holder 3. Since such a configuration is adopted, the holder 3 and the wafer 2 held by the holder 3 can be rotated without any trouble.

  As shown in FIG. 1, a refrigerant supply tube 7 is connected to a refrigerant tank 8 arranged on the atmosphere side, and this tube is provided with a cooling flange provided inside the vacuum vessel 25 via a feedthrough 26. 5 is connected. Thereby, the refrigerant is supplied from the refrigerant tank 8 to the cooling flange 5.

  In the present invention, in order to circulate the refrigerant, an example is shown in which two refrigerant supply tubes 7 are used as the refrigerant forward path and the backward path, but the present invention is not limited thereto. For example, the number of the refrigerant supply tubes 7 may be one, and this may be used as a reciprocating path. Further, the refrigerant may be supplied between the refrigerant tank 8 and the cooling flange 5 by using three or more tubes 7. Furthermore, it is desirable to provide a heat insulating material such as Aeroflex (registered trademark) on the outer periphery of the tube 7. If it does in this way, even if the conveyance route of a refrigerant | coolant becomes a little long, it will be possible to make it convey with the temperature of a refrigerant | coolant kept at low temperature enough.

  In the prior art, the refrigerant is configured to pass through the inner region of the holder driving mechanism, but in the present invention, as described above, the refrigerant supply tube 7 is disposed in the outer region of the holder driving mechanism. Cooling shrinkage does not occur in each member constituting the holder driving mechanism.

  Inside the cooling flange 5, there is provided a refrigerant flow path 9 for flowing the refrigerant, and a specific configuration is shown in FIG. As shown in FIG. 3, the cooling flange 5 is formed with a refrigerant flow path 9 drawn in a single stroke over the entire surface thereof. With this configuration, the entire surface of the cooling flange 5 can be efficiently cooled.

<Second Embodiment>
4 to 8 illustrate a configuration according to the second embodiment of the present invention. The difference from the first embodiment is that a heat transfer gas (for example, hydrogen or helium) is used to improve the cooling efficiency. Since the other points are the same as those in the first embodiment, description of overlapping parts is omitted.

  In the first embodiment described above, there is a gap between the cooling flange 5 and the holder 3. Since the inside of the vacuum vessel 25 is in a vacuum state, it is difficult for the cool air from the cooling flange 5 to be transmitted to the holder 3 side by the heat insulating action of the vacuum. Such a configuration is not preferable from the viewpoint of cooling efficiency. Below, 2nd embodiment aiming at the improvement of the cooling efficiency in 1st embodiment is described.

  As described in FIG. 4, in the second embodiment, the gas source 16 is provided on the atmosphere side. A gas supply tube 10 is connected to the gas source 16, and gas is supplied to the cooling flange 5 provided inside the vacuum vessel 25 through a feedthrough 26 provided on the wall of the vacuum vessel 25. Done.

  In this embodiment, the cooling flange 5 is provided with a gas flow path 28 for enabling introduction and extraction of gas. This is illustrated in FIG. Further, a seal member 11 that seals a space between the cooling flange 5 and the holder 3 is provided in the radial direction of the wafer 2 (X direction in the drawing). The seal member 11 is in contact with the lower surface of the holder 3 to such an extent that the rotation of the holder 3 can be allowed when adjusting the twist angle. In order to prevent the sealing function from being impaired by the friction generated when the holder 3 rotates, for example, a highly wear-resistant seal member such as Variseal (registered trademark) or Varilip (registered trademark) is used. In FIG. 5, illustration of the cooling flange 5 and the like located on the right side (X direction side) with the twist shaft 4 interposed therebetween is omitted. This is because the configuration is the same as that depicted on the left side of the twist shaft 4.

  Thus, the gas is filled in the space 12 (the hatched portion in the figure) sealed by the sealing member 11 between the holder 3 and the cooling flange 5, so that the holder is cooled from the cooling flange 5. The heat transfer rate to 3 is improved, and the cool air of the cooling flange 5 is easily transmitted to the holder 3. By adopting such a configuration, the cooling efficiency of the wafer 2 can be improved. The gas may be configured to be able to flow in and out through the flow path 28, or may be configured to be capable of only flowing in.

  6 is a cross-sectional view of the seal member 11 shown in FIG. As can be understood from FIG. 6, in this example, the space 12 is roughly divided into a donut shape by the seal member 11. Further, there may be one gas flow path 28 communicating with the space 12 as shown in the figure, or a plurality of gas flow paths 28 may be provided.

  FIG. 7 discloses a configuration that can be expected to further improve the cooling efficiency. In this example, a plurality of concave portions 13 (portions hatched by a two-dot chain line in the figure) are formed on the surface of the holder facing the wafer. The recess 13 communicates with the space 12 sealed by the seal member 11 by a through hole 14. By using such a configuration, the gas supplied to the cooling flange 5 is filled up to the lower surface of the wafer 2, so that the cool air from the cooling flange 5 can be more efficiently transmitted to the wafer 2. It becomes possible.

  FIG. 8 illustrates a state when the holder 3 illustrated in FIG. 7 is viewed from the opposite side in the Y direction. 7 corresponds to a cross section when the holder 3 is cut along the Y direction along a line segment DD along the X direction shown in FIG. In FIG. 8, a hatched portion with a two-dot chain line corresponds to the concave portion 13. The other parts excluding the through holes 14 are in contact with the lower surface of the wafer 2 and serve as parts for holding the wafer 2. Further, if a large number of through holes 14 are provided or the size of the through holes 14 is increased, the gas introduction time to the lower surface of the wafer 2 can be shortened.

<Third embodiment>
In the second embodiment, the configuration in which the gas is supplied through the cooling flange 5 has been described. However, the gas introduction member 15 may be attached to the twist shaft 4 and the gas may be supplied through the member. When such a configuration is used, it is not necessary to provide the gas flow path 28 in the cooling flange 5, and accordingly, the configuration of the cooling flange 5 can be simplified.

  Specific configurations of the third embodiment are shown in FIGS. As an example, the gas introduction member 15 is a concentric columnar member, and is attached to the twist shaft 4 via a bearing seal 29 so as to surround the outer periphery of the twist shaft 4. In this embodiment, the gas flow path 28 is formed so as to communicate with the gas introduction member 15, the bearing seal 29, the twist shaft 4, and the recess 13 formed in the holder 3.

  FIG. 11 is a sectional view of the twist shaft 4 including the gas introduction member 15 shown in FIG. At the position in the Y direction of the twist shaft 4 to which the gas introduction member 15 is attached, an annular groove 30 (hatched portion in the figure) is formed on the outer peripheral surface of the twist shaft 4. Even when the twist shaft 4 is rotated by the groove 30, the gas flow path 28 formed in the gas introduction member 15 and the bearing seal 29 and the radial direction and the length direction of the twist shaft 4 are extended. Connection with the gas flow path 28 is possible.

<Fourth embodiment>
In the second and third embodiments, the gas supply tube 10 is introduced into the vacuum vessel 5 through the feedthrough 26. However, the gas supply tube 10 is used for transporting the wafer 2 in the inner region of the vacuum vessel 5. In order to avoid interference with such a transfer arm, it is desirable that the inner region of the vacuum vessel 5 be configured simply.

  Therefore, in this embodiment, the gas introduction tube 10 is disposed in the inner region of the holder conveyance mechanism such as the scan shaft 23. This is illustrated in FIG.

  A gas having a relatively high temperature can be used as compared with the cryogenic refrigerant used in the present invention. This is because the gas is not used to cool the wafer 2 but is used only to improve heat transfer. For this reason, even if such a gas flow path is provided in the inner region of the holder driving mechanism, the holder driving mechanism does not undergo cooling shrinkage.

<Other variations>
The refrigerant tank 8 may be provided in the inner region of the vacuum vessel 5. By doing so, the path for supplying the refrigerant to the cooling flange 5 can be shortened, so that an increase in the temperature of the refrigerant during the conveyance can be avoided.

  In addition to the above, it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

2. Wafer 3. Holder 4. Twist shaft5. 5. Cooling flange Insulation material7. 7. Tube for supplying refrigerant Refrigerant tank 9. Refrigerant flow path 10. 10. Gas supply tube Seal member 17. Twist motor 20. Enclosure

Claims (7)

In an ion implantation apparatus comprising a holder for holding a wafer and a holder driving mechanism having at least a twist angle adjusting mechanism and a tilt angle adjusting mechanism,
A twist motor that constitutes a drive source of the twist angle adjusting mechanism and a rotor is attached to the holder;
A housing to which the stator of the twist motor is attached;
A cooling flange disposed at a location of the housing opposite the holder;
A refrigerant tank in which refrigerant is accumulated;
A refrigerant supply tube having one end connected to the cooling flange and the other end connected to the cooling tank; and the tube is disposed in an outer region of the holder driving mechanism. Ion implantation device. A seal member that seals a space between the holder and the cooling flange in the radial direction of the wafer;
The ion implantation apparatus according to claim 1, further comprising a gas source for supplying a gas to the space sealed by the seal member. A plurality of recesses formed to communicate with each other on a surface of the holder facing the wafer;
A gas introduction flow path provided in an inner region of the holder driving mechanism and connected to at least one of the recesses;
A gas introduction tube having one end connected to the gas source and the other end connected to the gas introduction path;
The ion implantation apparatus according to claim 2, wherein the plurality of recesses, the space sealed by the seal member, and the gas introduction path communicate with each other.   3. The ion implantation apparatus according to claim 2, wherein a flow path for introducing gas into the space sealed by the seal member is formed in the cooling flange.   A plurality of recesses formed to communicate with each other are formed on the surface of the holder facing the wafer, and the plurality of recesses communicate with the space sealed by the seal member. The ion beam irradiation apparatus according to claim 4. A plurality of recesses formed to communicate with each other on a surface of the holder facing the wafer;
Constituting the twist angle adjusting mechanism, and a twist shaft coupled to the holder;
A gas introduction member that is attached to the twist shaft via a bearing seal and into which gas from the gas source is introduced;
The gas introduction member, the bearing seal, and a gas introduction path communicated with the twist shaft are further included, and the plurality of recesses, the space sealed by the seal member, and the gas introduction path communicate with each other. The ion implantation apparatus according to claim 2, wherein: 7. The ion implantation apparatus according to claim 1, wherein a heat insulating material is provided between the cooling flange and the housing.