Apparatus for devices for determining properties of applied layers

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.

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.

DETAILED DESCRIPTION

InFIG. 1a coating installation1is depicted, which comprises a housing2, in which are disposed two electron beam vaporizers3,4and a plasma source5. The electron beams6,7emerge 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 vaporizers3,4.

The vaporized material migrates upwardly and coats substrates disposed on substrate holders8to10and55. These substrate holders8to10and55are mounted by special apparatus11,12. In the center of the substrate holders8to10or55is disposed the lower end of the apparatus13for devices for determining properties of vapor-deposited layers. This means that simultaneously with the substrate the lower region of the apparatus13is 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. 2shows once again the apparatus13in isolation. The apparatus13comprises a cylindrical sleeve14, an optical emitter15, an optical receiver16as well as four amplifiers17to20for four sensors, not shown inFIG. 2, and a diaphragm disk21.

The diaphragm disk21is again depicted inFIG. 3in a view from below. It can be seen that the diaphragm disk21has two throughbores22,23, with the throughbore22uncovering a glass plate and the throughbore23a crystal resonator. Glass plate and crystal resonator are not visible inFIG. 3.

FIG. 4shows the apparatus13again in perspective view and from the side. Again the diaphragm disk21is evident with the two throughbores22,23, the cylindrical sleeve14, the optical emitter15, the optical receiver16as well as the amplifiers17to20. Furthermore can be seen two measuring sliding devices24,25with two adjusting screws each for the x-y adjustment of light waveguides, of which inFIG. 4only one adjusting screw26,27is shown. By28,29are 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. 5shows a view from below onto the apparatus13, with the diaphragm disk21removed. An outer ring30can be seen which is provided with twelve circular openings, as well as an inner disk31encompassed by the ring30, which disk has four circular openings.

Into the openings of ring30are placed test glasses, while into the openings of disk31crystal resonators are placed. Instead of individual test glasses, a closed test glass ring can also be placed, which will yet be described. The outer ring30consequently contains test glasses for an optical measuring method. The outer ring30and the inner disk31are rotatable independently of one another. Thus, each of the four crystal resonators can be brought to the throughbore23and each of the twelve test glasses to the throughbore22of the diaphragm disk21. The appearance of the rotating mechanism is represented inFIGS. 7 to 10described in the following in further detail.

FIG. 6shows the optical emitter15and the optical receiver16in a sectional representation on an enlarged scale compared toFIG. 2. By44is denoted a light beam which emerges from light waveguide fibers not shown inFIG. 6. The light waveguide fibers enter through the upper opening, extend parallel to and between elements33,34and terminate at the lower end of bushing37. The light beam44is projected via a lens42onto a thin layer46on a test glass47, which is disposed in one of the recesses in ring30. From there the light beam44is reflected as light beam45and, via lens43, reaches a light waveguide disposed in a receiving bushing38, which conducts it further to an evaluation device, which is not shown.

In the cylindrical sleeve14are disposed two electrical geared motors60,61, of which the one geared motor61via a receiving bushing62for a needle (roller) bearing with free-wheeling and a shaft63, rotates the crystal resonator magazine64with four crystal resonators. The other geared motor60rotates via a shaft65, a driving gear66and a bushing83the ring30with the test glass67. The bushing83and the ring30are part of a hollow shaft. By68is denoted a vacuum-side plug for four position sensors, of which two position sensors71,73are evident inFIG. 7. The plug68establishes the connection between sensors71,73and the amplifiers17to20.

The lower portion ofFIG. 7is shown again inFIG. 8but at an enlarged scale. Apart from sensors71,73, two further sensors70,77are evident. The sensors71,73serve for acquiring the current position and the zero position of a test glass, while sensors70,77serve for acquiring the current position and the zero position of a crystal resonator. The sensors70involved are infrared light sensors serving as micro-light barrier.

As can be seen inFIG. 8the test glasses and the crystal resonators are disposed in one plane. Therewith is attained the shadow-free disposition of the crystal resonator magazine31and ring30with the test glasses. Through the sensors71,73;70,77in 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 ring30for test glasses does not need to be interrupted.

By75is denoted a hexagon nut beneath which are disposed five plate springs50to exert a defined pressure onto the ceramic disk disposed beneath. Above the nut75is disposed a further nut51, which counters the superjacent contact nut52. By76is denoted a driving shaft for the crystal resonator magazine31and by78a test glass. On the test glass78is reflected a light beam.

FIG. 9shows the way in which the test glasses are exchanged. For this purpose the threaded pins90are loosened, a disk81rotated until disengaged and subsequently lifted. Now the test glasses in bores91to97are exchanged. Disk81is subsequently placed on again and rotated until aligned. Three threaded pins—inFIG. 9only one threaded pin90is shown—-are now tightened. By82,83are denoted parts of the driving sleeve88for the test glass magazine. Above this driving sleeve88is disposed a sensor holder84, wherewith the sensors71,73, not visible inFIG. 9, are connected with the sensor holder84by means of nuts85,86.

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.

InFIG. 10is shown the way in which the crystal resonators are exchanged. Two cylinder screws are loosened, of which only one cylinder screw103is shown. Hereupon the disk31serving as crystal resonator holder is pulled off, the crystals are removed and new crystals are emplaced. The crystal resonator holder31is subsequently connected by screws with a basic body104.