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`Samsung Electronics Co., Ltd. v. Demaray LLC
`Samsung Electronic's Exhibit 1044
`Exhibit 1044, Page 1
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`

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`US.Patent
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`Jan.23, 1990
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`4,895,631
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`Ex. 1044, Page 2
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`Ex. 1044, Page 2
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`

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`1
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`4,895,631
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`PROCESS AND APPARATUS FOR CONTROLLING
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`THE REACTIVE DEPOSIT OF COATINGS ON
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`SUBSTRATES BY MEANS OF MAGNETRON
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`CATHODES
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`10
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`2
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`breakdown of the reaction product on the sputtering
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`surface of the target takes, relatively, a very long time
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`on account of the sputtering rate which in this case is
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`very low.
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`It has already been recognized that this alternation
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`can be expressed by a hysteresis curve if the reaction
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`gas flow exceeding the stoichiometric ratio is plotted
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`overthe reaction gas flow (EP-OS 0 121 019), to which
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`U.S. Pat. No. 4,428,811 corresponds. Even a control
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`process founded on this relationship and using a mass
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`spectrometer does not lead to the elimination of the
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`instability problems, because the time constants of the
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`individual components of the measuring and control
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`circuit are too long.
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`In reactive coating processes the objectis, as a rule,
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`to produce a chemical compound having the required
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`coating properties. These coating properties are to be
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`produced within close tolerances and with great long
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`term stability. A whole series of proposals have been
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`madefor regulating a parameter of the process of mag-
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`netron sputtering by means of control circuits having a
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`sensor for detecting a particular coating property. All
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`proposals, however, have led to only very limited suc-
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`cess. This is because many coating properties cannot be
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`measured in the coating zone, or they can be measured
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`only very imprecisely due to the effect of the plasma on
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`the measuring signals. In such control circuits, there-
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`fore, the measurement has always been performed out-
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`side of the coating zone. An obstacle to the achievement
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`_Of close tolerances in this kind of procedure is the time
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`difference between the end of the coating process and
`the measurement. Since the time constant has to be
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`madesubstantially greater than this time difference, in
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`the interest of the stability of the control circuit, the
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`result is large substrate areas which fail to be coated
`within the tolerances. These substrate areas can extend
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`over several of the substrates or, in the case of film
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`coating, over great lengths of the film, which conse-
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`quently have to be considered as rejects.
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`Still more important than the disadvantages cited
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`above of using the measured value of a property ofthe
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`coating for control purposes is the disadvantage that
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`such control circuits do not guarantee the stability of
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`the reactive coating process. Causes of such instabilities
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`are, for example, undesired changesin the gas composi-
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`tion, and arc discharges at the target which express
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`themselves in variations in the properties of the depos-
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`ited coatings. Suchinstabilities can tilt the process away
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`from the “metallic mode”to the “reactive mode.” Such
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`a tilt during the coating of the substrate signifies com-
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`plete rejection as far as the coating properties are con-
`cerned.
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`This so-called “tilting” occursat a critical flow of the
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`reaction gas, under otherwise constant electrical sput-
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`tering parameters. This rate is a measure of the basic
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`stability of the reactive process. If the reaction gas flow
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`is less than the critical flow, the magnetron cathode
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`operates in the so-called “metallic range” in which the
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`discharge can bestabilized by very simple means.In this
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`range of operation the required coating processes are
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`generally achieved by keeping such process parameters
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`as powerand reaction gas flow constant, and by timing.
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`Onthe other hand,in the “metallic range”it is gener-
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`ally impossible to deposit coatings of reaction products
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`with the required stoichiometry. By taking special mea-
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`sures to eliminate the influence of the reaction gas on
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`the target or on the substrate, such coatings can be
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`This application is a continuation, of application Ser.
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`No. 059,559, filed Jun. 8, 1987 abondoned.
`BACKGROUND OF THE INVENTION
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`Theinvention relates to a process for controlling the
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`reactive deposit of a coating on a substrate with a mag-
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`netron cathode operated at constant power anda target
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`having an electrically conductive component of the
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`coating material. The process includes measuring the
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`intensity of at least one spectral line of the target mate-
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`rial in the plasma of a sputtering process, and admitting
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`reaction gas in the vicinity of the target according to
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`this intensity. PROCESS AND APPARATUS FOR
`20
`CONTROLLING THE REACTIVE DEPOSIT OF
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`COATINGS ON SUBSTRATES BY MEANS OF
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`MAGNETRON CATHODES
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`The inventionrelates to a controlling process accord-
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`ing to the general part of claim 1.
`25
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`In such coating processes, an electrically conductive
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`target, usually a metal target, is sputtered in a reactive
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`atmosphere so that the magnetron cathode can be sup-
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`plied with direct current. A coating of the reaction
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`productof the target material then depositsitself on the
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`substrate, and the composition of the coating material
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`depends very greatly on the atmosphere surrounding
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`the magnetron cathode.
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`In this kind of coating process, three different modes
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`of operation of the magnetron cathode are distin-
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`guished, namely the “metallic mode,” “reactive mode,”
`and “transitional mode.” In the “metallic mode” the
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`sputtering surface of the target is of a metallic, ie.
`conductive character. In the “reactive mode” a corre-
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`sponding reaction product is found on the sputtering
`40
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`surface of the target, and, as a rule, it is an electrical
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`insulator, and the sputtering rate, i.c., the amount of
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`target material sputtered per unit time, is considerably
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`reduced. The “transitional mode” is between these two
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`operating modes and is considered to be unstable to a
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`very great extent, because it threatens totilt in the one
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`peculiarity typical of magnetron cathodes, in which an
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`erosion pit forms due to the locally restricted sputtering
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`process, and becomes increasingly deeper. While the
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`walls of the erosionpit can still be kept very largely free
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`of reaction products, the rest of the target surface be-
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`comes coated with the reaction products, and thus pro-
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`duces the unstable operating behavior previously de-
`scribed.
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`55
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`In order to prevent or suppress this unstable opera-
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`tion insofar as possible, it is already knownto feed the
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`reaction gas in at a point that is remote from the target
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`surface and shielded by a mask, and to feed into the
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`vicinity of the target an inert gas which produces the
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`sputtering (DE-OS33 31 707). If, when employing such
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`a measure, the feeding of the reaction gas is performed
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`according to the intensity of one or morespectral lines,
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`the result would be time constants that are extraordi-
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`narily long for such a control method, and which are
`65
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`unacceptable in a production process, especially a con-
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`tinuous production process. Moreover, in such a case a
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`slow alternation takes place between the “metallic
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`mode”and the “reactive mode” especially because the
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`Ex. 1044, Page 3
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`Ex. 1044, Page 3
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`

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`4,895,631
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`3
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`produced at correspondingly lowerrates (see, for exam-
`SUMMARYOF THE INVENTION
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`ple, the previously mentioned DE-OS 33 31 707).
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`In the procedures described abovefor the attainment
`The intensity of the spectral line of the target material
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`of the required coating properties, the reaction gas flow
`is measured in the plasma between the target and the
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`and/or an electrical working parameter have beenei-
`substrate. At least one property of the finished coating
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`ther kept constant or controlled.
`is measured and a reference value is produced which is
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`In controlling the process on the basis of a measured
`slidingly adjustedin relation to said property. Reaction
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`property of the coating, however, not only is the previ-
`gas admitted during the build-up of the coating is regu-
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`ously mentioned time interval between the end of the
`lated according to the intensity of the spectral line and
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`coating and the measurement disadvantageous, but also
`the reference value so that a pre-established coating
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`the time lag in the covering of the target is even more
`property is kept substantially constant.
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`critical. Necessary changes in the covering of the tar-
`It is important that the measurement be performedat
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`get, which occur for example in the case of a change in
`least of one spectral line in the plasma between target
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`the power, can bring about a time lag that is greater
`and substrate. This is an optical measurement, i.e., a
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`than the above-mentioned time interval resulting from
`measurement made with a spectral photometer aimed
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`the location of the point of measurementof the coating
`directly at the plasma. This means, when a magnetron
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`parameters. This time shift can amount to between sev-
`cathodeis used, that the optical sensor must be aimed at
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`eral seconds and several minutes, so that unacceptable
`elements of volumevery close to the target surface. The
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`changes in the coating process are the consequence.
`area in which the measurementis performedparallel to
`20
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`For economical reasons, coatings generally can be
`the target surface is preferably about 10 to 30 mm in
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`achieved with a high reactivity of the compound and
`front of the target surface.
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`high rates of deposition only in the so-called “transi-
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`The accuracy of such a measurement also differs
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`tional mode,” which is an unstable or metastable state of
`decidedly from a measurement performed with a mass
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`operation of the sputtering process, which has been
`spectrometer in which elements of volume of the gas
`25
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`referred to above.In the erosion pit in the target, coat-
`atmosphere are aspirated out of the coating area and
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`ing with reaction products is just barely prevented,
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`analyzed at a point remote therefrom. This method of
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`while the reaction products are deposited on the sub-
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`measurement suffers from a considerable time lag, and
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`strate with a high reactivity and at high rates. Working
`furthermore has the disadvantage that the composition
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`in the “transitional mode” requires the stabilization of
`of the gas can change along the way.
`30
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`the discharge by additional means.
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`The regulation of the reaction gas inlet with the
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`U.S. Pat. No. 4,166,784 discloses a method of regula-
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`shortest possible time constant is to be seen in conjunc-
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`tion by detecting the intensity of a characteristic line of
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`tion with the admission of the reaction gas close to the
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`the target material in the plasma. Thestabilization of a
`target. In this mannerit is possible to adapt the flow of
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`working point of the reactive dischargeis performed by
`the reaction gas very quickly to any change in the
`35
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`meansof a controlcircuit by which an electrical param-
`working conditions.
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`eter of the power supply at constantreaction gas flow is
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`The measurementofat least one property ofthe fin-
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`regulated on the basis of the intensity signal as the found
`ished coating is performed necessarily with a decidedly
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`value, or the reaction gasflow is controlled at constant
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`longertime constant, because first the substrate with the
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`electrical operating parameters.
`finished coating has to be transported from the coating
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`Through DD-PS 239,810 it is known to tune light
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`zone to the measuring zone. So in this case the adapta-
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`radiation out of a plasma discharge and use a spectral
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`tion of the reference value is performed at a slower
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`line or group of spectral lines to form a signal for the
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`speed. This, however, as experience has shown,is en-
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`purpose of regulating the gas flow. DD-PS 239,811 also
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`tirely sufficient for the achievementof the object of the
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`invention.
`discloses howareferencesignal can be found forfixing
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`45
`the position of the working point.
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`Whatis involved in principle is the superimposition
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`control circuits for assuring the processstability of a
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`of two regulating circuits, one of which has an ex-
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`given working pointof the dischargein a reactive cath-
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`tremely short and the other a markedly longer time
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`ode sputtering processutilizing an emission signal gen-
`constant. By controlling the weighting of the influence
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`erally cannot prevent the properties of the coating from
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`of the measured signals on the plasma side, on the one
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`being outof tolerance and/or from shifting over a long
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`hand, and on the substrate side on the other, the stability
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`period of time. There are a numberofreasons forthis:
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`of the overall regulating process can be decidedly im-
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`When new substrate surfaces are brought into the coat-
`proved.It is possible, for example, to set the percentage
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`ing area, surface coatings are released by the action of
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`of the measured signal from the plasmaat 60 to 90% and
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`the plasmaon thesubstrate. This causes the gas com-
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`the percentage of the measured signal from the sub-
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`35
`position in the discharge, and consequently also the
`strate measurement at 10 to 40%.
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`emission signal, to vary in an uncontrollable manner.
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`The procedure accordingto the invention, of achiev-
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`Desorption from parts of the apparatus after a target
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`ing a necessary process stability on the one hand andat
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`change likewise produces undesired changes in the
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`the same time achieving the necessary constancy of the
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`emission signals. Whatis critical in this phenomenon
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`coating properties on the other, by means based on
`60
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`is its uncontrollability and the fact that it is present
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`different principles, has proven to be an extremely ef-
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`over long periods of time, even for hours.
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`fective solution of the stated problem.It has been found
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`Furthermore, ail geometrical changes during the coat-
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`that a qualitative improvementof the control of plasma
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`ing process, especially progressive target erosion,
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`emission for process stabilization is made possible when
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`produce unwanted changes in the emission signal.
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`the time constant of the control circuit in question is
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`The problem to which the invention is addressed is to
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`kept as short as possible. Reducing the time constants of
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`devise a processof the kind described above, wherebyit
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`this control circuit can be achieved, however, only if
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`will be possible in a reactive coating process to regulate
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`the time lag in the feeding of the reaction gas is over-
`come.
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`the coating properties and achieve close tolerances.
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`40
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`4
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`Ex. 1044, Page 4
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`Ex. 1044, Page 4
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`

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`4,895,631
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`5
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`Short paths for the diffusion of the reaction gas from
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`the inlet to the area of the dense plasma in the magnetic
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`trap over the erosion profile are assured by admitting
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`the reaction gas as closely as possible to the target. This
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`kind of admission, in which the target area and the
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`substrate are coupled very closely, would result in a
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`drastic reduction of the basic stability of the discharge
`were it not for continuous variation of the reference
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`value. The close coupling between the inlet of the reac-
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`tion gas and the target surface is contrary to the stan-
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`dard practice of providing for extensive decoupling
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`betweenthe target and the substrate area in the interest
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`of a high basic stability.
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`The short time constant, and with it the close feed-
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`back of the measurement signal from the plasma, in
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`conjunction with the continuous variation of the preset
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`value, permit stable operation at arbitrarily selected
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`working points in the “transition range.” This means in
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`practice the gaining of degreesof liberty in the process,
`20
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`e.g., for the achievementof coatings with a wide range
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`ofspecifically controllable properties. For example, the
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`index of refraction of aluminum nitride coatings can be
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`varied in a range from 1.95 to 2.1. In the production of
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`indium-tin oxide coatings the specific resistance can be
`25
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`varied by orders of magnitude.
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`If the coupling created by the plasma emission con-
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`trol between the target area and the substrate areaisstill
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`further
`strengthened,
`coating properties
`can be
`achieved which have never before been achieved with
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`means of the prior art. For example, indium-tin oxide
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`coatings are produced on unheated substrates with sur-
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`face resistances under 1 x 10—4 ohms/cm, as compared
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`with 8x 10-4 ohms/cm with prior-art methods.
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`~ An explanation as to why the discharge can neverthe-
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`less be kept stable in the procedure according to the
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`invention can‘beseen in the fact that, on accountof the
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`close coupling, the percentage ofthe reaction gas thatis
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`reacted to the desired chemical compoundrelatively
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`increases because the excitation of the reaction gas in
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`the vicinity of the substrate also increases. On the other
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`hand, the close coupling andthe basic stability thereby
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`produced has the consequence that changes in the gas
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`composition as a result of desorption processes lead to
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`an intensified effect on the emission signal and hence on
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`45
`the coating properties.
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`Dueto the close coupling of the partial processes at
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`the target on the one hand, and at the substrate on the
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`other, the control process according to the invention
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`makesthe influence exercised bythe state of erosion of
`50
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`the target (the change in which leads to a shift in the
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`sputtering rate and in the excitation of the reaction gas)
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`on the coating properties becomerelatively greater.
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`The shift in the coating properties provoked by the two
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`effects, however, has a great time constant and can be
`35
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`effectively prevented by the coupling of the control
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`process according to the invention via the continuous
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`adjustment of the reference value.
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`Thus,it is especially advantageous that the regulation
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`according to the invention is not performed until after
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`the conditioning of the target surface is completed. By
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`this is meant the cleaning of the surface of a new target
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`or of a target that has been exposed to the ambientair.
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`In this case it is especially advantageous to proceed,
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`after the conditioning of the target surface is completed,
`65
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`by setting process parameters close to the working
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`point as required for the needed coating properties by
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`programmingthetimingofthe influx of the reaction gas
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`and steadily increasing it within d given adjustment
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`6
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`period until a flow of the reaction gas is reached which
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`approximately determines the level to be preset for at
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`least one coating property.
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`It is then especially advantageousif the value of the at
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`least one intensity signal measured for the flow of the
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`reaction gas at the end of the conditioning period and
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`adjustment period is compared with the reference value
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`for the coating properties. The reference value for the
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`first control circuit is formed on the basis of the compar-
`ison.
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`The emission intensity measured at the end of the
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`conditioning characterizes a defined starting state. The
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`working point in the reactive operation at which the
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`required coating property is achievedis initially identi-
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`fied by a reference intensity value which is determined
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`on the basis of preliminary experiments.
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`The invention also relates to an apparatus for the
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`performance of the process described above. For the
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`solution of the same problem, this apparatus is charac-
`terized in that
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`(a) An optical sensor of a spectral photometer system is
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`aimed at the space between the magnetron cathode
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`and the substrate, the sensor beam path being parallel
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`to the target surface and being disposed very close to
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`the latter,
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`(b) A gas distributing system is disposed close to the
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`target surface and is connected through a control
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`valve to a source of the reaction gas,
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`(c) The output of the spectral photometer system is
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`connected through an amplifier and a controller to an
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`actuatorof the control valve, the optical sensor, spec-
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`tral photometer system, amplifier, controller, actua-
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`tor and control valve forming a first control circuit
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`with a short time constant, equal to or less than 150
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`ms and preferably equal to or jess than 50 ms,
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`(d) In the path of the substrate coated immediately
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`before, a second sensorfor sensing at least one prop-
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`erty of the coated substrate is disposed, the output of
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`the second sensor being delivered to a second ampli-
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`fier whose output is delivered to a reference value
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`generator for the controller, while the secondsensor,
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`the second amplifier, the reference value generator,
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`the controller,
`the actuator and the control valve
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`connected to the output form a second controlcircuit
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`with a longer time constant than that of the first con-
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`trol circuit, and the first and second control circuits
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`are connected together in the controller.
`BRIEF DESCRIPTION OF THE DRAWING
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`Thesole figure is a partial section view of the vacuum
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`chamber, and also schematically shows the apparatus
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`and circuitry for controlling the reactive gas.
`DETAILED DESCRIPTION OF THE
`
`
`PREFERRED EMBODIMENT
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`In the drawing is represented a section of a vacuum
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`chamber 1 through which a substrate 2 is guided along
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`a path of movement whichis indicated by broken lines.
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`In a floor plate 3 of the vacuum chamber, surrounded
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`on all sides by an insulating spacethat is smaller than the
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`dark space to be observed underoperating conditions,is
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`a magnetron cathode 4 which consists of the following
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`parts: a basic cathode body 5 with a face plate 6 is in-
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`serted into the floor plate 3 with the interposition of a
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`ring 7 of insulating material.
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`On the upperside of the face plate 6, which is pro-
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`vided with cooling passages,is a target 8 ofan electri-
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`cally conductive material constituting the one compo-
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`Ex. 1044, Page 5
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`Ex. 1044, Page 5
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`

`

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`4,895,631
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`7
`8
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`nent of the coating material. On the bottom of the face
`of the substrate 2, the signal correspondingto the coat-
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`plate 6 is a magnet system 9 which consists of a ferro-
`ing properties is produced with a time delay which is
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`Magnetic yoke plate and permanent magnets disposed
`great in comparison to the time constant of the first
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`one inside the other thereon, the inner and outer mag-
`control circuit. As a rule the lag will amountto at least
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`nets having opposite polarity, whichis indicated by the
`0.5 second. The elements from the sensor 21 through
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`arrows. In the immediate marginal area of the target 8 is
`the reference value generator 25 to the control valve 11
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`a gas distributing system 9, but, as seen in plan, it comes
`constitute a second control circuit with a large time
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`just short of overlapping the target 8. The gas distribut-
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`constant, parts of the first and second control circuit
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`ing system 9 consists of one or two tubes which follow
`after the controller 19 being identical.
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`10
`the periphery of the target, at least on a large portion of
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`Furthermore, in the path of the substrate 2 just ahead
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`the circumference, and have perforations through
`of the coating station formed by the magnetron cathode
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`which the reaction gas can flow toward the target. The
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`4 with the reaction zone 14, a third sensor 28 is disposed
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`gas distribution system 9 is connected throughthrottle
`for detecting the properties of the substrate entering the
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`valves 10 and a commonregulating valve 11 to a source
`coating station, which is connected through a third
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`12 of a reaction gas or of a mixture of a reaction gas and
`amplifier 29 to the microprocessor 24. In the micro-
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`a working gas (argon). The voltage source for supply-
`processor 24 the signals of the sensors 21 and 28 are
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`ing the magnetron cathode 4 with a negative direct-cur-
`compared, so that only changesin the properties of the
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`rent voltage between 400 and 1000 volts has been omit-
`substrate in the coating station occurring within the
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`ted for the sake of simplicity.
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`reaction zone 14 are determined. This measure is impor-
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`Between the magnetron cathode 4 andthe substrate 2
`tant for the case, amongothers, that the coatingstation
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`a shield system 13 is disposed close to the substrate and
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`with the reaction zone 14 is preceded by another coat-
`can serve also as an anode and can either be at the same
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`ing station, so that the substrate enters the reaction zone
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`potential as the vacuum chamberor at a higher positive
`14 with one or more previous coatings.
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`Weclaim:
`potential. The target 8, the substrate 2 and the shield
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`25
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`system 13 substantially define a reaction zone 14 in
`1. Process for controlling the reactive deposit of a
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`which a reactive process takes place to coat the sub-
`coating on a substrate using a magnetron cathodeoper-
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`strate 2 with a compoundofthe target material and the
`ated at constant power and having a target with an
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`reaction gas.
`electrically conductive componentof the coating mate-
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`Anvoptical sensor 15 is aimed at a narrow portion of
`rial, said method comprising the steps of
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`the reaction zone 14 along a beam path running parallel
`introducing said substrate into a coating zone adja-
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`to the target 8. This beam pathis situated within a range
`cent to said target,
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`of 10 to 30 mm abovethe target 8. From the optical
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`admitting a reaction gas in the immediate vicinity of
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