US3780696A

US3780696A - Substrate holder for arc plasma deposition

Info

Publication number: US3780696A
Application number: US00270747A
Authority: US
Inventors: R Babbitt; J Locicero
Original assignee: United States Department of the Army
Current assignee: United States Department of the Army
Priority date: 1972-07-11
Filing date: 1972-07-11
Publication date: 1973-12-25
Anticipated expiration: 1990-12-25

Abstract

A tubular container, of refractory material has an opening in a top portion thereof. A horizontally disposed, thermally stable, perforated plate is supported by vertical portions of said container. A substrate, in alignment with said opening, is supported on said plate and clamped thereon by flanged pins combined with the perforations. An arc plasma gun deposits on the clamped substrate.

Description

Unlted States Patent 1 1 1111 3,780,696

Babbitt et al. 1 Dec. 25, 1973 [5 1 SUBSTRATE HOLDER FOR ARC PLASMA 1,534,918 4/1925 Claybourn 118/503 ux DEPOSITION 3,343,518 9/1967 Westeren et al l l8/49.5

3,473,510 10/1969 Sheng et al. 118/495 1 Inventors: Richard Babbitt, a Haven; 3,690,291 9/1972 Judd et al. 118/49.l

gtflsrelpii LoClcero, Middletown, both OTHER PUBLICATIQNS I I IBM Technical Disclosure Bulletin, Apparatus for In- Asslgneel The Unled States of America as troduction of Substrates Into a Vapor Deposition Sysrepresented y the Secretary of the tem, Silvestri, v. 1., v01. 8, No. 5 Oct. 1965). Army, Washington, DC. [22] Filed: Juy 11, 1972 Primary Examiner-Morris Kaplan Att0rneyHarry M. Saragovitz et al. [2]] Appl. No.: 270,747

[57] ABSTRACT [52] US. Cl 1l8/49.5, 118/503, 219/121 EB A ar n in of r ry m rial h n [51] Int. Cl. C23c 13/08 opening in a top portion thereof. A horizontally dis- [58] Field of Search 118/491, 49.5, 48, p rm y Stable, perforated plate is supported 118/49, 503; 219/158, 121 EB; l17/93,l by vertical portions of said container. A substrate, in alignment with said opening, is supported on said plate [56] References Cited and clamped thereon by flanged pins combined with UNITED STATES PATENTS the perforations. An arc plasma gun deposits on the 3,010,009 11/1961 Ducati 117/934 R clamped substrate 1,503,396 7/1924 Voight 118/503 UX 3 Claims, 6 Drawing Figures PATENTEI] UECZ 5 I973 FIG. 1 $1 G,?

IZWIM IO yl il IESQI'R/B n FIG. 4

FIG. 6 I-C)- FIG. 5 (8-8) SUBSTRATE HOLDER FOR ARC PLASMA DEPOSITION BACKGROUND OF THE INVENTION Arc plasma techniques are fairly well known and are used for metallizing. They are not readily useable for plasma deposition on ceramics, or on very delicate substrates, because of the unavoidable thermal shock, as well as the mechanical problems associated with holding thin, extremely delicate substrates or wafers steady against the blast of hot gasses from an arc-plasma gun.

The thermal shock of arc-plasma deposition can be overcome by preheating, but a thin substrate or wafer must be held quite securely to avoid its being blown off the baseplate by the blast of hot gasses. Spring clips have been tried but they do not survive in the extreme heat. Their springs usually burn out after only a few exposures to the blast from the gun. More rigid clips have been tried, but these tend to interfere with thermal expansion and produce a high percentage of damage to the wafers due to cracking or chipping along the lines of stress.

Vacuum techniques avoid some of these problems and can be used to hold a substrate down on a flat surface. These techniques require a perforated baseplate with a vacuum pump and conduits to apply the vacuum to the perforations adjacent to one side of the substrate. The vacuum pressure can be adjusted to any desired amount. However, vacuum equipment is inherently bulky and cumbersome and may not fit into, or be compatible to, available ovens.

Such bulky equipment may require the use of a form of hotplate, instead of an oven, with the substrate held on the perforated baseplate on top of the hotplate. However, in this case, the heat must go through the ceramic substrate to the surface to be coated. This presents problems because ceramic materials are almost always poor conductors. With vacuum techniques, again, a high percentage of substrates develop faults where the substrate adjoins the vacuum holes. In addition, the vacuum mounting equipment, to hold a substrate to a baseplate for arc-plasma deposition, is comparatively expensive.

SUMMARY OF THE INVENTION This invention is an improved device for arc-plasma deposition on a thin substrate. A baseplate for the substrate is made of material with minimum thermal expansion, such as a ceramic or lava, that will not melt or react at high temperatures. This baseplate material is machined to fit into an elongated tube or conduit, that is, preferably, of a diameter equal to one of the dimensions of the substrate. The baseplate is drilled to provide holes at intervals equal to the other dimension of the substrate, which is positioned between the holes. Weighted pins, fitting loosely in these holes, and having projecting heads to engage the substrate are used to hold the substrate in a given place along the baseplate during the arc-plasma deposition. The substrate may also be notched to engage the shanks of the pins to be held more securely, or so that a given baseplate can accommodate smaller substrates.

The elongated tube is positioned in an oven and must be made of a material that can withstand the heat of the oven. An arc-plasma gun is directed at the surface of the substrate through an opening in the tube. Both the tube and the elongated baseplate may be moved to control the position of the substrate with respect to the gun or to bring another substrate under the arc-plasma gun.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a plan view of a portion of a baseplate and a substrate of the same width;

FIG. 2 shows a plan view of the portion of the baseplate with a smaller substrate;

FIG. 3 shows a cross section of the baseplate and substrate along the lines A--A of FIG. 1',

FIG. 4 shows a plan view of an oven with a tube in position to hold the baseplate;

FIG. 5 shows a cross section of the tube, baseplate substrate, and the arc-plasma gun along the lines B-B of FIG. 4; and

FIG. 6 shows a cross section ofa portion of the same along the lines CC of FIG. 4.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to FIG. 1, the plan view shows a portion of a base 10 supporting a substrate 11 with

pins

14 and 15, having flanges l2 and 13 that engage the substrate.

FIG. 2 shows the plan view of a portion of the base 10, supporting a substrate 11A, of smaller dimensions than 11, with the

pins

14 and 15 having

flanges

12 and 13 that engage the substrate.

FIG. 3 shows the cross sectional view of the device along the lines AA of FIG. 1. This illustrates the portion of the baseplate 10, the substrate 11 and the

pins

14 and 15. This cross section also shows the

holes

16 and 17, through the baseplate, that contain the shanks I8 and 19 of the

pins

14 and 15 respectively. This cross section also shows the projecting heads or

flanges

12 and 13 of the pins that hold the substrate.

FIG. 4 shows the plan view of a typical assembly for arc-plasma deposition. An oven 20'contains an elongated tube 22 which extends through both ends of the oven. The tube has an opening 23 through which the substrate 11, the

pins

14 and 15, and a portion of the baseplate 10 can be seen. The arc-plasma gun and the cover of the oven are omitted here to more clearly show the position of the equipment for the arc-plasma deposition.

FIG. 5 shows the transverse cross section of the portion of the assembly of FIG. 4 along the lines B-B with the pipe 22, at the opening 23, containing the baseplate 10, with the pin 14 holding the substrate 11. An arcplasma gun 30 is shown in position adjacent to the substrate 11; the oven is omitted for simplicity.

FIG. 6 shows the axial cross section of a portion of the same assembly along the lines C C of FIG. 4 with the pipe 22, the opening 23, the baseplate 10, the substrate 11,

pins

14 and 15, and the arc-plasma gun 30. The oven 15, again, omitted for simplicity.

In operation, the substrate 11 is positioned on the baseplate 10 between two holes, such as 16 and 17.

Pins

14 and 15, with

shank portions

18 and 19, fit loosely in

holes

16 and 17 respectively. The

flanged heads

12 and 13 of the pins overlap the substrate 11 at both ends, and the pins are weighted to hold the substrate down under the normal turbulence 'created by the arc-plasma gun. This assembly is placed in the tube 22 so that the substrate is under the opening 23.

In the example shown, in all figures except FIG. 2, the substrate is as wide as the tubes diameter and the wall of the tube holds the sides of the substrate to limit lateral motion. With narrow substrates, as in FIG. 2, the ends of the substrate should extend past a portion of the pin and should be notched to accommodate the pins. These notches can limit lateral motion.

While the base holds the substrate near the center of the tube in these figures, it is obvious that the substrate could be positioned higher or lower in the tube and still be restrained by the walls of the tube. However, it should be noted that the substrate should not be in rigid contact with the walls of the tube since damage could result from mechanical stresses due to thermal or other causes.

Such techniques will be obvious, and the notches may be of any convenient size and shape. The notches here are consealed by the

heads

14 and 15 and are omitted for simplicity.

The arc-plasma gun 30 is directed at the surface of the substrate 11. Normally, the surface of the substrate is larger than the arc plasma stream and the gun must be moved with relation to the substrate in a consistent pattern in a well known manner to provide an even coverage of the desired surface. For this purpose, the baseplate, or the tube, or the arc plasma gun itself should be moveable with respect to each other.

After the desired deposition of arc plasma is completed, the assembly is allowed to cool, the baseplate is withdrawn from the tube, and the substrate is removed from the baseplate. The substrate can be cut to any desired size, or, in any case, the edges should be trimmed far enough in to avoid the effects of the pins as well as the inevitable nonlinearity of thedeposition of the plasma along the edges and corners.

The substrate may be masked to provide for depsition of the plasma in a specific area or in a specific shape. For example, the plasma may be deposited in the form of a strip waveguide or a microwave circulator.

The oven is a typical oven and may be of any well known make or type having a range of l,300 C. The oven must be large enough to contain the tube assembly and to include a port through which the gun can direct the arc plasma on the surface of the substrate.

The tube 22 with the opening 23 cut in the central portion is shown here as a typical, effective support for the baseplate and substrate. Besides keeping the substrate from moving in a lateral direction, as is apparent in FIG. 5, the sides of the tube also keep the arc-plasma stream from shooting past the baseplate and into the oven, where the'plasma might have an adverse effect on the oven itself.

The

pins

14 and 15 may be of any size and shape, but the

shank portions

18 and 19 must be of a size that can be held securely, but not rigidly, in the

holes

16 and 17 respectively. The pins must have wide

enough flanges

12 and 13 to securely engage the edges of a substrate,

and the pins must be of sufficient weight to hold down the substrate under the turbulent conditions generated by the arc-plasma gun. However, the pins should not be heavier than necessary and should not be heavy enough to risk damage to the substrate.

The are plasma gun may be of any of the types well known in the art. It provides a high velocity stream of inert gas, charged with metallic powder, at temperatures up to l0,000 C. The metallic powder will be deposited on any object to which the stream is directed. This jet stream at this high temperature and velocity provides a considerable thermal shock to anything it strikes and, although there is little physical inertia to the particles from the arc plasma gun, the wind generated by the blast could certainly blow away anything as small and fragile as a substrate.

The baseplate can be of any material, such as lava or perovskite, that can withstand the temperatures involved here with the minimum of expansion, contraction, or other adverse effects. The baseplate should be machinable, at least initially, to have the holes bored for the pins and to be cut to the desired size to accommodate the substrate and to fit into the tube. The holes are made very slightly larger than the pins to permit their easy insertion and withdrawal; to accommodate thermal expansion or contraction of the substrate or baseplate without damage to any of the parts; and to permit the pins to maintain a constant gravity pressure on the substrate. However, the holes should not be so much larger than the pins that they are loose enough to permit possible damage to the substrate through excessive motion.

In a typical embodiment of this invention, the electric oven 20 has a temperature of l,300 C; the tube 22 to be put within the oven is of alumina with an internal diameter of 1% inches and walls A thick; the tube has a length of 16 inches and the opening cut in the tube is 1 inch by 1% inches. The baseplate 10 is of perovskite, inches thick, 10 inches long, and 1% inch wide. It is formed to fit against the walls of the tube. The substrate 11 is of magnesium titanate, 2 inches long, 1% 'inches wide and 30 mils thick. The substrate is held by pins inch in diameter made of alumina. The are plasma gun is a $613 type made by Plasmodyne, Inc. It is charged with a ferrite powder.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What is claimed is:

1. In a device for arc-plasma deposition comprising:

an oven;

a refractory, tubular container of circular crosssection and having an opening in a top section thereof;

a horizontally arranged, elongated thermally stable baseplate extending longitudinally within said container and of a transverse width to be supported along its longitudinal edges by intermediate vertical portions of said container;

a substrate supported on said plate;

said plate being perforated and combined with a plurality of thermally stable pins which each fits freely in a respective one of said perforations;

each said pin being of a suitable weight and including a flanged element on its upper end whereby upon judicious choice of pins and apertures, said flange elements clamp the substrate to the baseplate;

said clamped substrate being aligned with said openan arc-plasma gun; and

means for directing the plasma stream through said opening whereby to deposit on the clamped substrate.

2. A device for arc-plasma deposition as in claim 1 wherein the inside diameter of said container is slightly larger than the width of said substrate and said conthe ends of said substrate are notched to fit around the shanks of said pins to keep said substrate from excessive motion in a lateral direction during said arc-plasma deposition.

Claims

1. In a device for arc-plasma deposition comprising: an oven; a refractory, tubular container of circular cross-section and having an opening in a top section thereof; a horizontally arranged, elongated thermally stable baseplate extending longitudinally within said container and of a transverse width to be supported along its longitudinal edges by intermediate vertical portions of said container; a substrate supported on said plate; said plate being perforated and combined with a plurality of thermally stable pins which each fits freely in a respective one of said perforations; each said pin being of a suitable weight and including a flanged element on its upper end whereby upon judicious choice of pins and apertures, said flange elements clamp the substrate to the baseplate; said clamped substrate being aligned with said opening; an arc-plasma gun; and means for directing the plasma stream through said opening whereby to deposit on the clamped substrate.

2. A device for arc-plasma deposition as in claim 1 wherein the inside diameter of said container is slightly larger than the width of said substrate and said container keeps said substrate from excessive motion in a lateral direction during said arc-plasma deposition.

3. A device for arc-plasma deposition as in claim 1 wherein the inside diameter of said container is substantially larger than the width of said substrate, and the ends of said substrate are notched to fit around the shanks of said pins to keep said substrate from excessive motion in a lateral direction during said arc-plasma deposition.