Apparatus for manufacturing semiconductor substrates

This apparatus for manufacturing semiconductor substrates has support disks and holding units holding semiconductor substrates on the support disks. The holding unit has a stopper which is formed of a conductive material and holds the brim of the semiconductor substrate, a stopper holder which supports the stopper at the outer circumferential portion thereof, a retaining member which retains the stopper to the support disk, and a heating unit which heats the stopper.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for manufacturing a semiconductor substrate used for manufacturing SIMOX (Separation by Implanted Oxygen) substrate by implanting oxygen ions into a semiconductor substrate of silicon and the like, and then applying a high-temperature treatment.

This application claims priority from Japanese Patent Application No. 2005-244656 filed on Aug. 25, 2005, the content of which is incorporated herein by reference.

2. Background Art

In a common batch-type ion implantation apparatus, for example, as shown in Patent Reference 1, multiple pieces of semiconductor substrate are mounted on multiple support disks equipped on one rotating plat-form and processed in a lump under vacuum.

An ion accelerated by necessary energy is implanted into a semiconductor substrate while being rotated like turning these support disks. As methods for uniformly implanting an ion in a semiconductor substrate, a method of scanning the support disks themselves in conformity to the turning of support disks or a method of scanning an ion beam only by turning support disks are given. In both methods, uniform ion implantation may be performed over the entire surface of all semiconductor substrates on the support disks.

Centrifugal force is utilized for the support of semiconductor substrates. Therefore, a structure of slightly inclining support disks for supporting the semiconductor substrates to the turning surface of the support disks to press the semiconductor substrates against the support disks is adopted.

If turning is inclined at only an angle α to the turning surface of the support disks, the semiconductor substrates are pressed against the support disks by a component of the centrifugal force in proportional to sine α. The inclination α may not be increased too large in restricting the ion implantation.

Therefore, the semiconductor substrates fly off to the outside only by a frictional force at the rear of semiconductor substrates. Accordingly, members called stoppers for suppressing the fly-off of the semiconductor substrates is necessary.

These stoppers have a width, but the support disks are commonly turned at several hundred rpm or so, and the acceleration at this time is also a value of over 150 G (G: gravity acceleration). The semiconductor substrates are 12 in. in diameter and about 150 g, thus the stoppers must support a load (22.5 kg) which is 150 times as much as its own weight.

However, the semiconductor substrates may not be supported on the support disks only at peripheral contact positions by the stoppers. Substrate inner supports must also be provided for the semiconductor substrates at the inner periphery of the support disks.

Moreover, an ion beam current implanted into the semiconductor substrates must flow to the outside of the support disks and the like. Therefore, at least the stoppers or the substrate inner supports must be ensured as a current passage. Stoppers capable of ensuring contact with the semiconductor substrates by the centrifugal force are suitable for the passage of ion beam current.

Furthermore, heat generated in the semiconductor substrates due to ion implantation is put out through the support disks by radiation heat transfer from the entire rear face of the semiconductor substrates, but part of heat is also put out through the stoppers or the substrate inner supports.

In the manufacture of SIMOX substrate, absolute values of the film thickness of the SI (Silicon ON Insulator) layer and BOX (Buried Oxide) layer are decided by the acceleration voltage and the implantation rate during oxygen ion implantation. At this time, the film thickness also depends upon the temperature during implantation.

The ion implantation rate may be made uniform to a level at which the uniformity of the film thickness is not affected by control of above-mentioned scanning conditions. It is also possible to ensure a uniformity level of temperature during implantation by heating the substrates with a radiation heater having an area larger than the semiconductor substrates, for which implantation is performed at the temperature during implantation, and further using material with high adiabaticity or high heat insulativity and no conductivity in the contact part of the substrate inner supports.

In an ion implantation apparatus used for manufacturing the SIMOX substrate, semiconductor substrates must be heated to a desirable temperature. Therefore, a radiation heater, such as halogen lamp and the like is disposed in a vacuum vessel provided with above-mentioned support disks.

When ion implantation is performed, the support disks loaded with the semiconductor substrates are turned and then the semiconductor substrates are heated to a desired temperature by the radiation heater. Subsequently, an ion beam is raised to perform ion implantation while controlling the disks or scanning of the beam.

If the implantation rate reaches a set value for the entire surface of semiconductor substrates, the scan control is stopped at a position where the ion beam does not hit the semiconductor substrates, the radiation heater is cut off and the rotation of the support disks is stopped.

Recently, however, the SOI layer has tended to be extremely thinned in the SOI substrates including SIMOX and only slight non-uniformity of film thickness has not been allowed. As a result, the problem that prescribed film thickness uniformity could not be realized was known to arise in the prior art.

In view of the above problem, an object of the present invention is to provide an apparatus for manufacturing semiconductor substrates capable of forming a SOI layer and BOX layer in a uniform thickness as a whole.

SUMMARY OF THE INVENTION

If SIMOX semiconductor substrates are prepared by the ion implantation apparatus of the prior art, a region with uneven film thickness occurs in a substrate holding part and a contact part with semiconductor substrates of the support disks, particularly in the vicinity of stoppers for ensuring conductivity.

It is known that this is a reason the semiconductor substrates are heated by a large-area radiation heater, but the temperature of semiconductor substrates becomes lower than that of other regions due to heat extraction caused by heat conduction from the semiconductor substrates to the contact part of stoppers and heat extraction caused by radiation heat transfer from the semi-conductor substrates to the stoppers.

Based of the above research results, the present invention realizes an apparatus for manufacturing semiconductor substrates which may form a SOI layer and BOX layer of uniform thickness as a whole by adopting a constitution for suppressing a temperature drop of a part in contact with stoppers where an ion current outflows.

A first aspect of the apparatus for manufacturing semiconductor substrates of the present invention includes support disks; and holding units for holding semiconductor substrates on the support disks, wherein the semiconductor substrates held by the support disks are subjected to an ion implantation while the semiconductor substrates are revolved like orbital motion. The holding unit has a stopper which holds the brim of the semiconductor substrate and which joins with the support disk, a stopper holder which supports the stopper at the outer circumferential portion thereof and which is fixed to the support disk as being able to attached and removed, and a retaining member which retains the stopper to the support disk and which is fixed to the support disk as being able to attached and removed. The stopper is formed of a conductive material and has a heating unit which heats the stopper.

In the first aspect of the apparatus for manufacturing semiconductor substrates of the present invention, the heating unit may be provided at the back surface of the stopper which is on the opposite side from the side facing the brim of the semiconductor substrate.

The holding unit may be provided on the outer side of the revolving orbit of the revolving support disk.

The stopper holder is formed of a strong metallic material that sustains a centrifugal force acting on the holding unit.

A second aspect of the apparatus for manufacturing semiconductor substrates of the present invention includes support disks; and holding units for holding semiconductor substrates on the support disks, wherein the semiconductor substrates held by the support disks are subjected to an ion implantation while the semiconductor substrates are revolved like orbital motion. The holding unit has a stopper piece which holds the brim of the semiconductor substrate and which is formed of a conductive material, a stopper-piece holding member which holds the stopper piece, a stopper holder which supports the stopper-piece holding member at the outer circumferential portion thereof and which is fixed to the support disk as being able to attached and removed, and a retaining member which retains the stopper-piece holding member to the support disk and which is fixed to the support disk as being able to attached and removed. The stopper piece is connected to the support disk via a conducting member, and has a heating unit which heats the stopper-piece holding member.

In the second aspect of the apparatus for manufacturing the semiconductor substrates of the present invention, the heating unit may be provided at the back surface of the stopper-piece holding member which is on the opposite side from the side facing the stopper piece.

The holding unit may be provided on the outer side of the revolving orbit of the revolving support disk.

The stopper holder may be formed of a strong metallic material that sustains a centrifugal force acting on the holding unit.

A third aspect of the apparatus for manufacturing semiconductor substrates of the present invention includes support disks; and holding units for holding semiconductor substrates on the support disks, wherein the semiconductor substrates held by the support disks are subjected to an ion implantation while the semiconductor substrates are revolved like orbital motion. The holding unit has a stopper piece which holds the brim of the semiconductor substrate and which is formed of a conductive material, a stopper-piece supporting platform which supports the stopper piece, a stopper-piece holding member which holds the stopper piece and the stopper-piece supporting platform, a stopper holder which supports the stopper-piece holding member at the outer circumferential portion thereof and which is fixed to the support disk as being able to attached and removed, and a retaining member which retains the stopper-piece holding member to the support disk and which is fixed to the support disk as being able to attached and removed. The stopper-piece supporting platform and the stopper-piece holding member are formed of a material having a heat insulating property. The stopper piece is connected to the support disk via a conducting member, and has a heating unit which heats the stopper-piece holding member.

In the third aspect of the apparatus for manufacturing semiconductor substrates of the present invention, the stopper-piece holding member may contain a ceramic material or a quartz material which has a heat insulating property.

The heating unit may be provided at the back surface of the stopper-piece holding member which is on the opposite side from the side facing the stopper pieces.

The holding unit may be provided on the outer side of the revolving orbit of the turning support disk.

The stopper holder may be formed of a strong metallic material that sustains a centrifugal force acting on the holding unit.

A fourth aspect of the apparatus for manufacturing semiconductor substrates of the present invention includes support disks; and holding units for holding semiconductor substrates on the support disks, wherein the semiconductor substrates held by the support disks are subjected to an ion implantation while the semiconductor substrates are revolved like orbital motion. The holding unit has a stopper piece which holds the brim of the semiconductor substrate and which is formed of a conductive material, and a stopper holder which supports the stopper piece at the outer circumferential portion thereof and which is fixed to the support disk as being able to attached and removed. A conducting member which electrically connects the support disk and the stopper piece are provided.

The present invention enhances the temperature uniformity in the ion implantation and improves the film thickness uniformity of SOT layer and BOX layer of the SIMOX semiconductor substrates because heat escaping through the stoppers is compensated for by the heating unit.

PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described hereafter with reference to the accompanying drawings. The present invention is not limited to the following embodiments and constituent elements of these embodiments may be appropriately combined.

First, the ion implantation of an apparatus of manufacturing semiconductor substrates are described byFIG. 1toFIG. 7.

As shown inFIG. 1, oxygen ion generated in an ion source1enters a mass separator3accelerated by a lead-out electrode2. Unnecessary ions and impurities are removed and only the necessary ion is withdrawn by applying a magnetic field corresponding to the ion species implanted by the mass separator3.

The oxygen ion in which impurities are removed is implanted into semiconductor substrates10by controlling the path and shape of an ion beam200further accelerated by a post-accelerating electrode4and deflecting it at30oby a deflector6.

A rotary platform30has a rotary box31, a rotary shaft32fitted to the rotary box31, multiple arms33provided and radially arranged in the rotary box31and support disks34. The support disks34are rotated, turning by the rotation of a rotary shaft32. The semiconductor substrates10are held and turned on these turning support disks34.

The support disks34are inclined as shown inFIG. 3. The support disks34with an angle α to the turning surface are so placed that the turning periphery side becomes the upper side and the turning inner side becomes the lower side. That is, the support disks34have such an inclina-tion that the mounting face for mounting the semiconductor substrates10faces to the rotation axis of the rotary box31.

The implantation of ion beam200into the semiconductor substrates10held at the sup-port disks34of the rotary platform30and rotating like turning is performed as shown inFIG. 2,FIG. 3. The implantation of oxygen ion is performed over the entire surface of semiconductor substrates10by scanning the implanting ion beam200in the direction of illustrated arrows.

Moreover, the implantation of oxygen ion may be performed over the entire surface even if the rotary platform30is scanned in the direction of illustrated arrows as shown inFIG. 1.

FIGS. 4A and 4Bshow a holding unit for a semiconductor substrate.

FIG. 4Ais a diagram in which the semiconductor substrate held by the holding unit is viewed from the front, andFIG. 4Bis a diagram showing an A-C cross-section ofFIG. 4A.

A stopper40of the holding unit is provided so as to locate on the turning periphery side of the turning support disk34. A substrate inner supports41are provided near to the turning inner side. The semiconductor substrate10is held by the stopper40and the substrate inner sup-ports41.

A centrifugal force acting on the semiconductor substrate10due to turning is stopped by the stopper40, therefore the semiconductor substrate10is surely held even if it is rotated like turning at a high speed of about several hundred rpm.

As described above, the support disk34supporting the semiconductor substrate has an inclination such that the mounting face for mounting the semiconductor substrate10faces the rotating axis of rotary box31. Therefore, the semiconductor substrate10is surely held by the support disk34because is pressed against the support disk34by the centrifugal force due to high-speed turning.

FIGS. 5A and 5Bshow another embodiment of the holding unit.

FIG. 5Ais a diagram in which the semiconductor substrate held by the holding unit is viewed from the front, andFIG. 5Bis a diagram showing a D-O-C cross-section ofFIG. 5A.

This embodiment is different from the former embodiment in that two adjacent stoppers40are provided and one substrate inner support41is provided and has a common constitution in others.

The holding of the holding unit is further illustrated by citingFIG. 6.

A stopper40is provided on the turning periphery side of the support disk34, and movable chucks42are provided on the turning inner side. A stopper groove43is provided on the inner side of the stopper40.

The semiconductor substrate10is set on the support disk34and pressed against the stop-per40by rotating the chucks42in arrow directions. The brim of semiconductor substrate10is joined with the stopper groove43of the stopper40, thus the semiconductor substrate10is surely held.

The related structure of stopper being the main part of the present invention is described by citingFIG. 7,FIG. 8next.

The holding unit forming the principal part of the related structure of stopper has a stopper125, a stopper holder126and a retaining member128.

The stopper125of the holding unit is provided on the turning periphery side of the support disk34. This stopper125is made of silicon or carbon so as to keep the conductivity and has the stopper groove43for receiving the brim of semiconductor substrate10.

The stopper125is placed so as to join with the support disk34, and its periphery side is supported by a stopper holder126. The stopper holder126is formed of a metallic material such as an aluminum alloy and the like. for sustaining the load of centrifugal force. The stopper holder126is fastened and fixed to the support disk34with a fastening screw127.

The retaining member128for retaining the stopper125to the support disk34is fastened and fixed to the support disk34with a fastening screw129.

The stopper125is attachably/detachably mounted to the support disk34by the stopper holder126and the retaining member128.

An ion beam current implanted into the semiconductor substrate10flows to the support disk34via the stopper125having conductivity and made of silicon or carbon.

Moreover, the implantation conditions of the ion beam current are as follows.

The heating unit is provided at the back of stopper125opposite of the brim of the semiconductor substrate10. The heating unit has a heater140and a heater supporting adiabatic plate141. Feed lines142,143are fastened and fixed to both terminals of the heater140by stop screws144. In this embodiment, the both terminals are provided to keep grounding potentials of power supply and beam current of the heater140independently. However, it is also possible to connect one terminal to the support disk34.

The heater140is joined so as to closely adhere to the back of stopper125and well per-form heat transfer. The heating unit is housed in a housing space provided between the back of stopper125and the inner side of stopper holder126so that the stopper holder126also serves as a support of the heating unit.

The heater desirably has such a constitution that a foil used for conducting path is pasted to a ceramic insulation substrate resistant to a high temperature of 1,000K or above. Heat may be compensated for by the heater even if the heat transferred from the stopper125escapes due to the related structure of stopper125of this embodiment. Temperature drop on a site in contact with the stopper125in the semiconductor substrate10is measured by ion implantation. It was confirmed that the temperature drop is suppressed by 10% to 5% in comparison with one provided with no heating unit.

This enhances the temperature uniformity of the semiconductor substrate and improves the film thickness uniformity of SOI layer and BOX layer of the SIMOX semiconductor substrate.

Another embodiment of the related structure of stopper is described by citingFIG. 9andFIG. 10.

Here, the features of this embodiment are mainly described, the same symbols are attached to parts common to the former embodiment examples and their description is omitted.

A holding unit forming the principal part of the related structure of stopper has a stopper piece150, a stopper piece holding member151, a stopper holder126, a stopper piece support platform152and a retaining member128.

The stopper piece150of the holding unit is provided on the turning periphery side of support disk34. This stopper piece150is made of a carbon conductive material and has a stopper groove43for receiving the brim of a semiconductor substrate10. The stopper piece150made of carbon also has a high radiance of heat.

The stopper piece holding member151holds the stopper piece150and the stopper piece support platform152.

The stopper piece holding member151and the stopper piece support platform152are formed of quartz or ceramic. The stopper piece holding member151and the stopper piece support platform152made of quartz have insulativity, have adiabaticity by which heat is hard to transfer, and is also excellent in respect of mechanical strength. They may suppress the occurrence of foreign matters during ion implantation.

The stopper piece holding member151and the stopper piece support platform152have tapered surfaces in their facing portion. A conducting member153is interposed between the tapered surfaces so as to sandwich it. The conducting member153extends to be clamped by the stopper piece holding member151and the stopper piece support platform152and further clamped by the retaining member128and the support disk34. An aluminum foil or aluminum thin sheet of about 0.02 to 0.1 mm is used as the conducting member153.

An ion beam current implanted into the semiconductor substrate10flows to the support disk34via the stopper piece150and the conducting member153. Implantation conditions of the ion beam current are same as in the former embodiment.

The conducting member153is strongly and firmly clamped because it is clamped by the tapered surfaces of the stopper piece150and the stopper piece support platform152. The stopper piece150is pressed against the stopper piece holding member151and fixed strongly and firmly by a pressing force caused by joining of the tapered surfaces.

A heating unit is provided at the back of stopper piece holding member151opposite the stopper piece150.

Heat transfer from the heater140to the stopper piece150is performed via the stopper piece holding member151having adiabaticity, therefore it is expected to need more heating value of the heater140than the former embodiment described byFIG. 7andFIG. 8. However, surfacing is needed to increase the contact heat resistance between the stopper piece holding member151and the stopper piece support platform152. Consequently, the heating value of the heater may be reduced by making the heating volume smaller than the stopper125of former embodiment only by the size of stopper piece support platform152.

Carbon having high heat radiance is used for the stopper piece150, and the stopper piece holding member151and the stopper piece support platform152are formed of quartz which is hard to transfer heat. The radiation heat transfer effect on the stopper piece150are utilizable because the surface temperature of the heater140becomes 1,000K or above. The heat radiation effect may be increased by facing the heater140and the stopper piece150so that their lengths in the width direction are 20 to 25 mm, respectively and suppressing the width of conducting member153shielding the radiation to 3 to 4 mm. The necessary heating value of the heater140is decreased by the radiation heat transfer effect.

The stopper piece150of this embodiment is much smaller than the stopper125of the former embodiment, therefore the radiation heat withdrawn from the semiconductor substrate10by the stopper piece150is reduced. This enables lowly suppressing the heat generation of the heater140.

As described above, the stopper of this embodiment enables to suppress the partial temperature drop of the semiconductor substrate10at a smaller heating value of the heater140than that of the former embodiment described byFIG. 7andFIG. 8.

FIG. 11shows a cross-section of SIMOX semiconductor substrate. The surface side is SOI layer and the inner side is BOX layer.

FIGS. 12A and 12Bshow a surface temperature distribution of the semiconductor substrate during ion implantation.

FIG. 12Ashows measured values measured during ion beam implantation at various heating values of the heater.FIG. 12Bshows measured values measured during ion beam implantation by manufacturing apparatus provided with no heater. T is the measured value, and Tc is the reference value. The reference value is made to 1.0.

The horizontal axis represents a range of going apart from a part in contact with the stopper. The vertical axis represents the measured temperature.

As shown inFIG. 12B, it is known that the temperature is lower than the reference value Tc and approaches to the reference value with going apart from the stopper when in contact with the stopper.

As shown inFIG. 12A, it is known that the temperature drop when in contact with the stopper is slowly corrected by increasing the heating value of the heater. For the heating value, the temperature is the best at 25 W, conversely, it is more than the reference value at 30 W.

The temperature of semiconductor substrate during ion implantation changes with implantation energy, beam current value and temperature of radiation heater. In order to uniform the temperature distribution on the semiconductor substrate during ion implantation, it is necessary to adjust the exothermic input power of the heater suited to the implantation conditions.

FIGS. 13A and 13Bshow measured values of film thickness distribution of SOI layer.

The measuring SIMOX semiconductor substrate is prepared by setting the input of heater to 25 W. The implantation conditions of ion beam are same as those of the formerly described embodiment.

FIG. 13Ais a SIMOX semiconductor substrate manufactured while heating with the heater, andFIG. 13Bis a SIMOX semiconductor substrate manufactured while not heating with the heater. InFIGS. 13A to 13B, t is the measured value, and tc is the reference value. The reference value is made to 1.0. As shown inFIG. 13A,13B, it is known that the film thickness distribution of SOI layer is made uniform over the entire layer by heating with the heater.

FIGS. 14A and 14Bshow measured values of the film thickness distribution of BOX layer.

The measuring SIMOX semiconductor substrate is prepared by setting the input of heater to 25 W. The implantation conditions of ion beam are same as those of the formerly described embodiment.

FIG. 14Ais a SIMOX semiconductor substrate manufactured while heating with the heater, andFIG. 14Bis a SIMOX semiconductor substrate manufactured while not heating with the heater. InFIGS. 14A to 14B, t is the measured value, and tc is the reference value. The reference value is made to 1.0. As shown inFIG. 14A,14B, the film thickness distribution of BOX layer is made uniform over the entire layer by heating with the heater.

As shown inFIG. 13andFIG. 14, a thick film of SIO layer, BOX layer when in contact with the stopper is not found and a good SIMOX semiconductor substrate made uniform over the whole is provided by beating with the heater.

Some preferred embodiments of the invention have been described above, although these embodiments are considered in all respects as being illustrative and not limiting. Those skilled in the art will appreciate that various additions, omissions, substitutions and other modifications are possible without departing from the scope of the invention as disclosed in the accompanying claims.