Abstract:
The invention relates to an apparatus for devices for determining properties of thin layers applied on a substrate. This apparatus comprises two changing magazines wherein one magazine is provided for crystal resonators and the other magazine for test glasses. The changing magazine for crystal resonators has the form of a disk and is encompassed by the annular magazine for test glasses. Both can be rotated independently of one another. Each position of the magazines can be reproduced with the aid of sensors and evaluation devices. Consequently, it is possible to carry out multiple coatings.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to an apparatus for devices for determining properties of applied layers. 
     When coating substrates, for example optical lenses and glasses, it is important to acquire the properties of the applied layers, for example in order to be able to determine the time at which the coating is to be terminated. In particular multiple coatings, which are employed in the production of high-quality optical objects such as beam splitters, color conversion filters, cold light mirrors and laser mirrors, require highly precise measuring devices to ensure the quality and the reproducibility of the coatings. The physical properties which define the quality of thin layers are essentially the transmission, reflection, absorption, scattering, thermal stability and moisture resistance as well as the abrasion resistance and adhesiveness. 
     For determining the thickness and measuring the coating rate, i.e. of the mass applied per unit time, crystal oscillators are already known, whose crystal is coated in a manner similar to the substrate (DE 31 20 443 C2). Its mass is changed through the coating of the crystal, which, in turn, has an effect on the frequency of the crystal oscillator. The frequency change of the crystal oscillator is consequently a measure of the thickness of the deposited layer, while the frequency change per unit time can serve as a measure of the coating rate. 
     While the coating rate can be determined relatively precisely by means of a crystal oscillator, the measurement of the absolute layer thickness entails imprecisions such that for this purpose other measuring methods, for example optical ones, are preferred. In the case of optical measuring methods the applied thin layer is irradiated with a light beam and the reflected beam is compared with the irradiating beam. Based on the ratio of irradiating to emitted light beam it is possible inter alia to determine the thickness of the layer. 
     Thus, for measuring the transmission of an [epitaxially] grown layer on a test glass a spectral photometer is utilized (DE 43 14 251 A1) during the coating. The white light of a halogen lamp is conducted with a light waveguide to a vacuum lead-through with imaging optics and through the imaging optics imaged onto the test glass. A second vacuum lead-through with imaging optics images the transmitted light on a monochrometer or a line filter with succeeding detector. 
     It is also known to determine the growth of layers optically with the aid of a light source with detector and a test glass as well as also with the aid of crystal resonators (DE 37 42 204 A1). 
     It is further known that a light source emits a light beam with specific wavelength onto a film thickness control substrate, which is reflected onto a detector (DE 693 09 505 T2, corresponding to EP 0 552 648 B1). The quantity of light reflected from a film thickness control substrate varies as a function of the index of refraction and thickness of the thin film which has formed on the film thickness control substrate. 
     The invention addresses the problem of providing an apparatus with which the determination of the properties of a layer by means of a crystal oscillator and an additional optical method is carried out. 
     This problem is solved according to the present invention. 
     The invention consequently relates to an apparatus for devices for determining properties of thin layers, which are applied onto substrates. This apparatus comprises two changing magazines with one magazine being provided for crystal resonators and the other for test glasses. The changing magazine for crystal resonators has the form of a disk and is encompassed by the annular magazine for test glasses. Both can be rotated independently of one another. With the aid of sensors and evaluation devices each position of the magazines can be reproduced. Therewith it is possible to carry out multiple coatings. 
     One advantage attained with the invention comprises that it can be applied with an online process regulation or with the precise determination of switch-off conditions during the epitaxial growth of thin layers in order to measure the reflection or transmission on test glasses or on the substrate itself. 
     A further advantage of the invention comprises that several test glasses and several crystal resonators can be provided and be brought into specific positions. Furthermore is of advantage that the test glasses and the crystal resonators can readily be exchanged. If a test glass ring is utilized instead of several individual test glasses, the different positions of this test glass ring can be encountered reproducibly and repeatedly. 
     An embodiment example of the invention is shown in the drawing and will be described in further detail. 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         FIG. 1  a coating installation with the apparatus according to the invention, 
         FIG. 2  a side view of the apparatus, 
         FIG. 3  a view onto the underside of the apparatus, 
         FIG. 4  the apparatus in a perspective representation, 
         FIG. 5  a view onto the underside of the apparatus with the diaphragm removed, 
         FIG. 6  an enlarged representation of a light emitter and a light receiver, 
         FIG. 7  a section through the lower region of the apparatus according to  FIG. 4 , 
         FIG. 8  an enlarged representation of a portion of the apparatus according to  FIG. 7 , 
         FIG. 9  an exploded view of an apparatus according to  FIG. 4  to explain the changing of test glasses, 
         FIG. 10  an exploded view of a portion of the apparatus according to  FIG. 9  to explain the changing of crystal resonators. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  a coating installation  1  is depicted, which comprises a housing  2 , in which are disposed two electron beam vaporizers  3 ,  4  and a plasma source  5 . The electron beams  6 ,  7  emerge from (not shown) electron beam sources and are curved through magnetic fields such that they impinge onto the material to be vaporized in the electron beam vaporizers  3 ,  4 . 
     The vaporized material migrates upwardly and coats substrates disposed on substrate holders  8  to  10  and  55 . These substrate holders  8  to  10  and  55  are mounted by special apparatus  11 ,  12 . In the center of the substrate holders  8  to  10  or  55  is disposed the lower end of the apparatus  13  for devices for determining properties of vapor-deposited layers. This means that simultaneously with the substrate the lower region of the apparatus  13  is also coated. Since the location at which this region is located, is not identical with the locations of the substrates, a conversion factor must be drawn on in order to draw conclusions from the thickness of the layer disposed on the apparatus to the thickness of the layer on the substrates. 
       FIG. 2  shows once again the apparatus  13  in isolation. The apparatus  13  comprises a cylindrical sleeve  14 , an optical emitter  15 , an optical receiver  16  as well as four amplifiers  17  to  20  for four sensors, not shown in  FIG. 2 , and a diaphragm disk  21 . 
     The diaphragm disk  21  is again depicted in  FIG. 3  in a view from below. It can be seen that the diaphragm disk  21  has two throughbores  22 ,  23 , with the throughbore  22  uncovering a glass plate and the throughbore  23  a crystal resonator. Glass plate and crystal resonator are not visible in  FIG. 3 . 
       FIG. 4  shows the apparatus  13  again in perspective view and from the side. Again the diaphragm disk  21  is evident with the two throughbores  22 ,  23 , the cylindrical sleeve  14 , the optical emitter  15 , the optical receiver  16  as well as the amplifiers  17  to  20 . Furthermore can be seen two measuring sliding devices  24 ,  25  with two adjusting screws each for the x-y adjustment of light waveguides, of which in  FIG. 4  only one adjusting screw  26 ,  27  is shown. By  28 ,  29  are denoted water connections for the running in and out of cooling water. With the aid of the cooling water the crystal resonators are cooled. The test glass has substantially the temperature of the substrate (max. 300° C.). A high degree of isolation of the test glasses with respect to the crystal resonators is attained. 
       FIG. 5  shows a view from below onto the apparatus  13 , with the diaphragm disk  21  removed. An outer ring  30  can be seen which is provided with twelve circular openings, as well as an inner disk  31  encompassed by the ring  30 , which disk has four circular openings. 
     Into the openings of ring  30  are placed test glasses, while into the openings of disk  31  crystal resonators are placed. Instead of individual test glasses, a closed test glass ring can also be placed, which will yet be described. The outer ring  30  consequently contains test glasses for an optical measuring method. The outer ring  30  and the inner disk  31  are rotatable independently of one another. Thus, each of the four crystal resonators can be brought to the throughbore  23  and each of the twelve test glasses to the throughbore  22  of the diaphragm disk  21 . The appearance of the rotating mechanism is represented in  FIGS. 7 to 10  described in the following in further detail. 
       FIG. 6  shows the optical emitter  15  and the optical receiver  16  in a sectional representation on an enlarged scale compared to  FIG. 2 . By  44  is denoted a light beam which emerges from light waveguide fibers not shown in  FIG. 6 . The light waveguide fibers enter through the upper opening, extend parallel to and between elements  33 ,  34  and terminate at the lower end of bushing  37 . The light beam  44  is projected via a lens  42  onto a thin layer  46  on a test glass  47 , which is disposed in one of the recesses in ring  30 . From there the light beam  44  is reflected as light beam  45  and, via lens  43 , reaches a light waveguide disposed in a receiving bushing  38 , which conducts it further to an evaluation device, which is not shown. 
       FIG. 7  shows the changing apparatus  13  according to  FIG. 4 , however without the optical emitter  15  and receiver  16 . 
     In the cylindrical sleeve  14  are disposed two electrical geared motors  60 ,  61 , of which the one geared motor  61  via a receiving bushing  62  for a needle (roller) bearing with free-wheeling and a shaft  63 , rotates the crystal resonator magazine  64  with four crystal resonators. The other geared motor  60  rotates via a shaft  65 , a driving gear  66  and a bushing  83  the ring  30  with the test glass  67 . The bushing  83  and the ring  30  are part of a hollow shaft. By  68  is denoted a vacuum-side plug for four position sensors, of which two position sensors  71 ,  73  are evident in  FIG. 7 . The plug  68  establishes the connection between sensors  71 ,  73  and the amplifiers  17  to  20 . 
     The lower portion of  FIG. 7  is shown again in  FIG. 8  but at an enlarged scale. Apart from sensors  71 ,  73 , two further sensors  70 ,  77  are evident. The sensors  71 ,  73  serve for acquiring the current position and the zero position of a test glass, while sensors  70 ,  77  serve for acquiring the current position and the zero position of a crystal resonator. The sensors  70  involved are infrared light sensors serving as micro-light barrier. 
     As can be seen in  FIG. 8  the test glasses and the crystal resonators are disposed in one plane. Therewith is attained the shadow-free disposition of the crystal resonator magazine  31  and ring  30  with the test glasses. Through the sensors  71 ,  73 ;  70 ,  77  in connection with an evaluation circuit not shown, it is possible to localize the individual positions of the test glasses and of the crystal resonators. Thus, a test glass in a specific position can be multiply coated. This multiple utilizing of a test glass in a specific position entails advantages with respect to the length of the process, since the process for changing of the ring  30  for test glasses does not need to be interrupted. 
     By  75  is denoted a hexagon nut beneath which are disposed five plate springs  50  to exert a defined pressure onto the ceramic disk disposed beneath. Above the nut  75  is disposed a further nut  51 , which counters the superjacent contact nut  52 . By  76  is denoted a driving shaft for the crystal resonator magazine  31  and by  78  a test glass. On the test glass  78  is reflected a light beam. 
       FIG. 9  shows the way in which the test glasses are exchanged. For this purpose the threaded pins  90  are loosened, a disk  81  rotated until disengaged and subsequently lifted. Now the test glasses in bores  91  to  97  are exchanged. Disk  81  is subsequently placed on again and rotated until aligned. Three threaded pins—in  FIG. 9  only one threaded pin  90  is shown—-are now tightened. By  82 ,  83  are denoted parts of the driving sleeve  88  for the test glass magazine. Above this driving sleeve  88  is disposed a sensor holder  84 , wherewith the sensors  71 ,  73 , not visible in  FIG. 9 , are connected with the sensor holder  84  by means of nuts  85 ,  86 . 
     In a variant of the test glass magazine a device is provided with an inner tubular part and an outer tubular part, with the height of the inner part being greater than that of the outer part. A receiving ring for test glasses is subsequently placed between the two tubular parts. This receiving ring comprises several circular and equidistant cutouts over the circumference. Onto this receiving ring is subsequently placed a test glass ring, i.e. no circular individual test glasses are employed but rather a closed test glass ring. Onto this test glass ring is subsequently also set a contact ring. 
     In  FIG. 10  is shown the way in which the crystal resonators are exchanged. Two cylinder screws are loosened, of which only one cylinder screw  103  is shown. Hereupon the disk  31  serving as crystal resonator holder is pulled off, the crystals are removed and new crystals are emplaced. The crystal resonator holder  31  is subsequently connected by screws with a basic body  104 .