the invention will be described in greater detail subsequently with the aid of fig4 to 16 . the invention relates to an apparatus for the thermal treatment of substrates , especially semiconductor wafers , in a chamber in which the wafers are placed upon support elements . such an apparatus is known , for example , from de - a - 198 21 007 of the same applicant , and to this extent is made the subject matter of the present invention in order to avoid repetition . the chamber in which the semiconductor wafer is placed upon the support elements is surrounded by a heating device that is comprised of lamps or banks of lamps that are disposed above and below the chamber . pursuant to the present invention , the support elements are movably or displaceably mounted in order to follow a movement of the wafer , especially during an expansion or other distortion resulting from the thermal treatment . fig4 shows a first embodiment of a carrier construction 6 for a support element 8 in the form of a support pin . the support pin 8 has a first end 10 with a support tip 11 for receiving a semiconductor wafer . an opposite end 13 of the support pin 8 is secured in a suitable manner to a flat helical spring 15 . the helical spring 15 is formed by cutting out a portion 16 from a thin plate 17 , for example a thin quartz plate . due to the cutout portion 16 in the quartz plate 17 , the flat helical spring 15 is resilient not only in a horizontal direction but also in a vertical direction . fig5 and 6 show a second embodiment of the present invention for a movable suspension of a support pin 8 . the support pin 8 has a first end 10 on which is formed a support tip 11 . in this connection , the end 10 of the support pin 8 is embodied as a double cone . the support tip 11 is formed by one cone having an opening angle between 50 degrees and 130 degrees , and preferably between 80 degrees and 100 degrees . following this cone is a second cone having an opening or generating angle between 5 and 45 degrees and preferably between 5 and 25 degrees . the thus - formed support tip is sturdy and reduces the danger that the tip will break off . the support pin 8 has a longitudinal axis a . mounted on one side of the support pin 8 is a pivot pin 20 having a longitudinal axis b . the longitudinal axis b of the pivot pin 20 extends perpendicular to the longitudinal axis a of the support pin 8 , and is laterally offset relative thereto . the pivot pin 20 is received in a suitable holding device , such as a u - shaped holding device , so that the support pin 8 is mounted in a swinging manner . due to the fact that the longitudinal axis b of the pivot pin 20 is offset from the central axis a of the support pin 8 , the pivot pin 20 is inclined in a rest position . in this connection , the longitudinal axis b of the pivot pin 20 is disposed in such a way that the support pin 8 is inclined relative to a central axis of the wafer that is to be received . fig3 a and 3 b show defect locations on the back side of a semiconductor wafer that were produced during the thermal treatment by swingingly mounted support pins pursuant to fig5 . as can be clearly recognized in a comparison to the defect locations shown in fig2 a and 2 b , the swingingly mounted support pin produces only a point - type impression rather than an elongated scratch . the damage to the surface of the wafer is thus significantly reduced , which is attributable to the support pin moving along during the thermal expansion of the wafer . fig1 shows a further embodiment for the movable holding of support elements . in this connection , sleeve - like receiving devices are arranged in a tilted manner for receiving support pins . the support pins are seated with great play in the sleeve , while their angle of tilt is in the range of 1 °- 45 °, preferably between 1 °- 10 °. fig7 shows an alternative embodiment for the movable suspension of support pins 8 . with the embodiment of fig7 , the support pins 8 are mounted on a rigid carrier frame 27 via freely swinging or oscillating carrier arms 25 . a total of three support pins 8 are mounted on the carrier frame 7 and form an equilateral triangle upon which a wafer is placed in a centered manner . during a thermal treatment of a wafer placed upon the support pins 8 , the freely oscillating carrier arms 25 follow a thermally - caused movement , especially an expansion movement , of the wafer . in addition to the freely oscillating carrier arms 25 , the support pins 8 could , of course , also be movably mounted upon the carrier arms . a preferred embodiment for a movable mounting of the support pins 8 , for example in combination with the freely oscillating carrier arms , is illustrated in fig8 . in this connection , the end 13 that is remote from the support tip 11 has a conical configuration . the conical end 13 is received in a receiving means 28 , such as a sleeve , and is pivotably held thereby . alternatively , the conical end could also simply be received in a hole of the carrier arm 25 . fig9 shows a further alternative embodiment of a movable support pin 8 pursuant to the present invention . the support pin 8 has a first end 10 , which forms a support tip 11 . the end 10 is again provided with a double cone , whereby the cone that forms the support tip 11 has an opening angle of 90 degrees , and the following cone has an opening angle of 15 degrees . adjoining the second cone is a support flange 30 that provides a considerable widening of the support pin 8 in a middle portion thereof . the support flange 30 forms a support surface 31 , which will be described in greater detail subsequently with reference to fig1 . connected below the support flange 30 is a lower end 13 of the support pin 8 . in this connection , provided in the transition region between support flange 30 and lower end 13 is an undercut or relief groove 33 . furthermore , the end portion 13 has a tapered end 34 . the support pin 8 is produced from a light - permeable material , such as quartz , in order to avoid a shading effect due to the support pin 8 . to achieve a smooth surface and a good transparency of the support pin 8 , it is fire polished . the relief groove 33 , as well as the tapered base 34 , are provided due to possible changes in the dimensions during this process . in the region of the support tip 11 , the support pin 8 is not fire polished , so that this region remains relatively opaque . as a result , the tip does not freely allow the heating radiation through , and is thus itself heated up during a thermal treatment . as a result , the temperature gradient between support tip 11 and wafer is reduced , thereby achieving a greater homogeneity of the wafer temperature . fig1 shows a simplified illustration of an alternative embodiment of a support pin 8 . the support pin 8 essentially corresponds to the support pin illustrated in fig9 . it has an upper end 10 , a support flange 30 , and a lower end 13 . provided on the lower end portion 13 is a widened base 36 , the function of which will be described in greater detail subsequently with reference to fig1 . fig1 shows a receiving plate 40 for receiving support pins 8 pursuant to fig9 or 10 . the receiving plate 40 has three slots 42 that extend radially relative to a central axis c , and that are provided at their radially outer ends with a widened bore 44 . the slots 42 are angularly uniformly spaced from one another . the dimensions of the slots 42 are such that they receive the lower end portion 13 of the support pins 8 of fig9 and 10 and can guide such end portions in a radial direction . the widened bore 44 is dimensioned such that the widened base portion 36 of the support pin of fig1 passes through the bore 44 . however , the bore 44 is not so large that the support flange 30 of the support pin 8 of fig9 and 10 can also pass through . rather , the support surfaces 31 of the support flanges 30 come to rest upon the upper side of the receiving plate 40 , whereby the support pins 8 are slidingly mounted along the slots 42 and upon the receiving plate 40 . the widened base 36 of the support pin 8 of fig1 is dimensioned such that it does not fit through the slots . this prevents the support pin 8 from being moved along with the wafer and coming out of the slot 42 when a wafer is raised . in contrast , the support pin of fig9 has an appropriately lengthened base portion 13 for this purpose . the receiving plate 40 is made of a light permeable material , such as quartz , in order not to adversely affect the thermal treatment of the wafer . although this is not illustrated , the light permeable support flange 30 of the support pin 8 can have a lens - shaped configuration in order to form an optical lens . in this connection , the lens shape is selected such that light radiation of a heating field is focused on the contact location between support tip 11 and wafer . in this way , thermal losses of the wafer at this location are compensated for , and the temperature distribution is homogenized over the surface of the wafer . fig1 and 13 show alternative embodiments of support pins 8 having a support flange 30 , according to which the support flange 30 is respectively provided with a curved support surface 31 . with the embodiment of fig1 , the support flange 30 forms the lowermost portion of the support pin 8 . the support flange 30 , with its curved support surface 31 , is received in a receiving means 50 that is adapted to the curved shape and that is , as is the support pin 8 , made of a transparent material . the support pin 8 is pivotably guided within the receiving means 50 . with the embodiment of fig1 , an end portion 13 is connected below the support flange 30 . the curved or arc - shaped support surface 31 of the support flange 30 rests upon a receiving ring 52 and thus enables a tilting movement of the support pin 8 . the end portion 13 is received with relatively great play in a receiving sleeve 54 in order to limit the tilting movement of the support pin 8 . fig1 and 15 show a further alternative embodiment for a movable mounting of support pins 8 . with this embodiment , a holder 60 is provided that has three carrier arms 62 that on their free ends are respectively provided with an opening 64 for receiving a support pin 8 . the carrier arms 62 extend from a central , roof - shaped central portion 66 in which is formed a downwardly directed blind hole 68 . the blind hole 68 serves for receiving a stud 70 having a rounded support end 71 . the other end portion 72 of the stud 70 is received in a closely fitting manner in a receiving means 74 of a rigid carrier arm 75 . the blind hole 68 and the stud 70 , especially the rounded support end 71 , are dimensioned such that the holder 60 is tiltably disposed upon the stud 70 . as a result , when a wafer is placed upon the support pins , a self or automatic correction of the support pins 8 is achieved for small deviations in height . a total of three of these holders 60 are provided , so that a wafer is placed on a total of nine support pins 8 , in contrast to the previous three support pins 8 . as a result , slight pressure forces occur at the respective contact points , thereby reducing damage of the wafer . in addition , a minimal shading of the wafer relative to the heat radiation is achieved , whereby preferably all elements are made of a material , such as quartz , that is transparent for the heat radiation . although this is not illustrated , the individual support pins 8 can be respectively movably mounted on the free ends of the carrier arms 62 in order to again be able to follow a movement of the wafer during the thermal treatment . in so doing , a tiltable mounting of the support pins 8 , as illustrated by way of example in fig1 or 13 , is particularly suitable . pursuant to a further , non - illustrated embodiment of the invention , instead of support pins , spheres or balls can be utilized as support elements . such balls preferably have a diameter between 0 . 5 mm and 5 mm . during a thermal expansion of the wafer , the balls roll on a base support in conformity with the magnitude of the expansion , and thus always contact only one point of the wafer surface . in this connection , the movement of the balls can be prescribed by support surfaces , such as grooves . these grooves are preferably inclined relative to a central axis of the substrate in order to ensure that after a wafer has been removed , the balls always roll back into a certain starting position . in this connection , the grooves are preferably disposed relative to one another in the same way as are the slots of fig1 . pursuant to one preferred embodiment of the invention , in order to receive a wafer three support elements are respectively provided that are disposed at the ends of an equilateral triangle , and hence form a good three - point support . in this connection , the center of the triangle coincides with the central axis of a wafer placed thereupon . each support element is , in this connection , spaced from the central axis of the wafer by a distance of 0 . 5 to 0 . 8 times the wafer radius ( r ). the spacing is preferably ⅔ of the wafer radius . if the elements are spaced greater than 0 . 8 r from the central axis , larger wafers , for example having a diameter of 300 mm , sag in the middle during the thermal treatment . if they are disposed too close to the axis , the rim of the wafer sags downwardly during the thermal treatment . if the support elements are disposed in the above mentioned range , and in particular at ⅔ of the wafer radius , the sagging of the wafer is at a minimum , as a result of which the formation of dislocation errors or slip lines is minimized . instead of individual support elements , it is also possible to respectively provide a holder 60 having respectively three support elements at the corner points of the triangle . although the invention was described with the aid of preferred embodiments , the present invention is not limited to the specifically illustrated embodiments . in particular , the various ways for mounting or supporting the support elements can be combined with one another . preferably , all of the described support elements , as well as the support or mounting elements that are correlated therewith , are produced from materials that are transparent for the heat radiation . such materials are , for example , aluminum nitride , aluminum oxide , zirconium oxide , silicon carbide , boron nitride , sapphire , saphal ( trademark of the company toshiba ) or ceramic . particularly advantageous are quartz , magnesium oxide , silicon and primarily silicon nitride . the specification incorporates by reference the disclosure of german priority document 100 03 639 . 2 filed 28 jan . 2000 and international priority document pct / ep01 / 00607 filed 19 jan . 2001 . the present invention is , of course , in no way restricted to the specific disclosure of the specification and drawings , but also encompasses any modifications within the scope of the appended claims .