DE2106049A1 - Improved process for the manufacture of pore-free thin layers by vacuum evaporation - Google Patents

Description

IMPROVED PROCESS FOR PRODUCING PORE-FREE THIN FILMS BY VACUUM EVAPORATION The invention relates to a process for the production of pore-free Thin layers on an insulating basis by vacuum evaporation. Such procedures will be in the optical industry e.g. in the manufacture of surface mirrors and light filters and monochromators, in the semiconductor manufacturing companies, e.g. in manufacturing applied by metal masks, resistive layers and capacitors. In bigger and bigger For the mass, thin (0.1 micron thick) layers are required that are practically pore-free and are also resistant to mechanical stress.

The quality of the thin films produced by the known processes is still unsatisfactory in this regard. The amount of scrap that will be generated is largely due to the inequalities or

Unevenness of the support surface and the pores in the applied layer influenced. For example, metal layers can also be used which, in terms of their quality Approx. 20-30 pores / cm2 are considered to be good, and also in the Layers that are exposed to mechanical stress create ever more pores.

Up until now it was believed that the pores in the layers were after evaporation because there is no corresponding in the course of the process Cleanliness of the air could be assured and the iii dtt layer entered Impurities (dust grains, etc.) that are not bound in the layer, also prevent the binding of the material particles that are deposited on them, so that separate these particles from the layer upon mechanical action (fall out len). In the case of metal layers, one has already been staked, the layer one to expose subsequent mechanical stress, e.g. with which textiles to rub, and then to vaporize another layer, possibly the stress and to repeat the subsequent re-steaming several times, whereby the Probability increases significantly that also the bodies of the impurities caused pores are covered. However, this recommendation has so far not led to any practical application of a process with which a much lower pore formation could have been achieved.

The inventive method enables the production of layers, their pore density by an order of magnitude lower than the previously manufactured, i.e. 2-3 pores / cm2, on large areas and under relatively harsh manufacturing conditions, as there are no special ones Air dedusting methods must be used in the course of the procedure. I) he individual steps of the procedure guarantee that the number of on contaminating granules located on the support surface, either in the course the surface preparation work or from the environment, e.g. in the stable the carrier surface and which later detach a pore formation (holes) in the shift can cause, at the end of the procedure in the finished shift does not exceed the aforementioned value, i.e. 2-3 particles / cm2 molar.

The essence of the invention is the knowledge that pore formation in the thin layers produced by vacuum vapor deposition in the usual way with the strongly adhering to the support surface and from there through cleaning processes including buffing and ultrasonic cleaning - non-removable Granules the size of egg.

nem micron or below, or with the shielding effect of the same and other surface irregularities. The one from the evaporation source The coming material jet of steam cannot be applied to the area behind the granules settle so that this area; remains empty.

Just as essential is the knowledge that the on the support surface strongly adhering granules just hunter the action of in the by vacuum evaporation The resulting mechanical stresses then become loose and that, in terms of which granules this effect occurs, the operating conditions of steaming play a fairly large role. By evaporation with a small one Evaporation source at a directional angle can loosen the predominant Majority of these particles are reached, and the subsequent ones mechanical Stress (e.g. cleaning by ultrasound or other polishing) leads to their removal. With a renewed steaming can now a well-adhering coating can also be achieved on the pore areas thus created. The shielding effect is only removed in the case when this second Evaporation no longer comes from a small evaporation source, in a directional one Angle, but practically evenly, from all directions of the half-noise angle he follows.

This evenness can of course be varied to varying degrees, e.g. by arranging some point-like sources in different places of the Get closer to the half-space angle.

For a completely different task and with a different effect a vapor deposition from such a space angle has already been used, However, not for the creation of porn-free (hole-free) layers. The procedure is significant for the reason that it eliminates the possibility that the Particles or depressions protruding from the original surface of the primordial carrier a shielding effect with regard to the material vapor streams of the evaporation material exercise.

In the case of those manufactured with the known and previously used technology This shielding effect can be clearly observed in layers: in the vicinity of the sharp ones Projections and granules, possibly depressions, appear shadows on the finished Layer. When using the method according to the invention, however, these are omitted Shadows, and 80 are the layers produced with the method according to the invention to be clearly distinguished from those manufactured in the known manner which, as a result of the lack of clarification of the actual causes, the shielding Effect could not yet be eliminated.

So the end result will be due to the on the Circumstances and causes of pore formation (hole formation) relating new knowledge the inventive method, in which the first vapor deposition process a mechanical stress and then a further vaporization process follow, thereby characterized in that the first evaporation process is from a point-like evaporation source takes place at a directed angle, whereas the second vapor deposition process is carried out uniformly from the entire half-space angle regardless of direction. The experiments proved that the extent of the relaxation of the not; sufficient adhering grains required evaporation depending on the material is, however, lags with the materials used in practice, such as chrome and other metals, the first vapor deposition in the case with the desired success, when it reaches an average layer thickness of 0 400 ~ 800 A is made. In the case of directional vapor deposition, the direction lies in the direction of the vapor deposition beam and the angle of incidence advantageously included between 20 and 800.

In an advantageous embodiment, that according to the invention In the process, the surface of the I-zolier base is chemically polished, u.zw. with an etchant, the composition of which is based on glass or quartz from the literature is known: 5% in ?, 35% HNO3, 60% H2O. Another advantage is secured by if the rinsing and drying following the etching is carried out by centrifugation.

The further details of the method according to the invention become on the basis of an advantageous implementation variant described as an example describe: l. Preparation of the surface of the support In the one considered as an example Case is that Wear a Hariglas peeled in optical quality. The etching of the glass takes place in a kempensierende effect Etching agents determine this process, the inhomogeneities on the surface - remove or remove quartz and surface roughness

reduce the position of the margins of the inhemenitaten. The composition the etching agent is indicated separately. The etching time depends on the hardness and the texture of the glass 1 20 minutes. Effective removal of the caustic agent from the Oberli ehe is possible, for example, by rinsing in nitric hydrochloric acid, whereby di.e Rinsing time is 4-5 minutes.

Both after etching and after bathing in nitric acid the carrier is rinsed twice in distilled water. The last rinse is required also in distilled water but in a centmifuge in such a way that the distilled water 11 of the rotating centrifuge in the center of the plate or there and also in several of the rotational axis in the radial direction further and further lying points hits the surface in the form of rays. the The time for rinsing in the centrifuge is 3 minutes.

The drying takes place in such a way that the workpiece continues revolves in the centrifuge (rotated), but with the rinse water taps are closed, and arranged by the along the rotation diameter Nozzles warm (90 - 100 ° C), carefully dedusted (filtered) stickstotj S minutes long blown onto the workpiece In the method described above Pay particular attention to the following: The preparation of the carrier has to be expedient to take place in a closed, dust-free booth. To rinse is careful Use filtered, dust-free, double-distilled water.

The walls of the centrifuge housing are to be designed in such a way that the Liquid particles ejected from the rotating plate and hitting the walls do not rebound on the support surface. The housing is expediently pyramid-shaped with an angle of at least 150 standing side surfaces.

The carrier must be kept in a closed container and from one work process to the other. It must also be ensured that the surface cannot dry from the etching until the last rinse.

2. Production of the metal layer in the given vacuum deposition apparatus is at the pressure <and trigger temperature values caused by the layer quality a metal layer with an average thickness of 500 R from the evaporation source Vaporized onto the support surface (in the lengthwise direction of the apparatus used this process can possibly be carried out on several carriers at once.) The carrier removed from the apparatus is placed in a closed container placed in filtered and twice distilled water and in the Bell container one Subjected to ultrasonic treatment, which in the metal layer according to the im During the course of the process, the loosened grains of the loosened tension arise Surface removed (instead of ultrasonic treatment, another mechanical Effect, e.g. rubbing).

Then, while avoiding intermediate drying, rinsing with distilled Water and then also drying during spinning in the centrifuge performed.

On those pretreated in this way and already covered with a layer Another metal layer is used as the carrier with an average Thickness of about 500 ß in such a way that the support surface of the entire half-space angle is swept (hit) by the steam jets. This evaporation can be realized 1 that the evaporation sources along half a circular arc and the carrier around the vertical Axis rotates, or that an evaporator source is used and in the vertical axis is arranged around which the carrier is then rotated during the vapor deposition and simultaneously Swiveled back and forth around the horizontal axis in an angular range from 0 to + 900 can be. The quotient of the periods of the rotating and the pivoting movement must be as an irrational number can be chosen.

Claims (9)

PATENT CLAIMS 1. Process for the vapor deposition of layers by vacuum vapor deposition, in the course of which the surface riacll the first evaporation process of a mechanical Is exposed to stress (e.g. ultrasound, even friction by wiping) whereupon a second vapor deposition process is carried out, thereby g e k e n n æ e i c h -n e t that the first evaporation of a point-like Source is done at a directed angle, followed by the second vapor deposition is made uniformly from the entire half-space angle regardless of direction. 2. The method according to claim 1, characterized in that g e -k e n n z e i c h n e -t that in the course of the first vapor deposition a layer with an average Thickness of 300-800 Å is applied. 3. The method according to claim 1 or 2, characterized in that g e -k e n n z e i c h n e t that at the first vaporization of the by the direction of the carrier of a small source of reaching (hitting) material beam and the incidence plumb bob included angles has a value of 20 - 800. 4. The method according to any one of claims 1 to 3, characterized g e k e n nz e i c h II e t that the first vapor deposition process and the subsequent one mechanical action - possibly several times - repeated and the second, from evaporation, which finally takes place uniformly from the half-space angle is made afterwards. 5. The method according to any one of claims 1 to 4, characterized g e k e n It should be noted that the evaporation sources are related to the second evaporation process be arranged in an ItalbkreLsbogen around the carrier and that the Triger is rotated around the vertical axis during the vapor deposition process. 6. The method according to any one of claims 1 to 4, characterized g e k e n It should be noted that the second evaporation process involves an evaporation source is arranged in the vertical axis and that the carrier is rotated about this axis and during the duration of the steaming, in addition to the rotating movement, also around the horizontal axis is pivoted back and forth. 7. The method according to any one of claims 1 to 6, characterized g e k e n Note that the second vapor deposition process was done two or more times will. 8. The method according to any one of claims 1 to 7, characterized g e k e n notify that in the course of preparing the substrate for vapor deposition this is subjected to etching by an etching agent, the composition of which 5% HF, 35% HHO3 and 60% H2O. 9. The method according to any one of claims 1 to 8, characterized g e k e n I would like to point out that in the course of the procedure the final rinsing and drying operations be carried out in a centrifuge.