US3917125A

US3917125A - Apparatus and method for dispensing materials into a melt composition

Info

Publication number: US3917125A
Application number: US457032A
Authority: US
Inventors: David M Heinz; Frederick S Stearns
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1974-04-01
Filing date: 1974-04-01
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04

Abstract

A simplified dispenser assembly for dispersing precision measured quantities of materials to single crystal growing systems such as liquid phase epitaxy deposition systems is disclosed. The dispenser assembly includes a vertically mounted, funnel-shaped container with an opening in its apex having a fine mesh screen thereover. The screen is used for metering the metal material through the opening in the base of the funnel and into the melt composition utilized in a liquid phase epitaxy deposition system. The container is supported by a tripod arrangement connected to a rod for lowering and raising the dispenser assembly.

Description

United States Patent [191 Heinz et a]. [4 Nov. 4, 1975 APPARATUS AND METHOD FOR 3,191,813 6/1965 Duff 222/356 DISPENSING MATERIALS MO A MELT 3,661,373 5/1972 Cheltsov et a1. 266/34 T COMPOSITION Primary Examiner-Stanley H. Tollberg [75] Inventors S gzi g g Assistant Examiner-Hadd Lane earns acen 0 a1 Attorney, Agent, or FirmH. Fredrick Hamann; G. [73] Assignee: Rockwell International Corporation, Donald Weber, Jr.; Roland G. Rubalcava El Segundo, Calif.

[22 Filed: Apr. 1, 1974 [57] ABSTRACT [21] A L N 457 032 A simplified dispenser assembly for dispersing precision measured quantities of materials to single crystal growing systems such as liquid phase epitaxy deposi- [52] US. Cl; 222/189; 222/465; 266/34 T tion Systems is disclosed The dispenser assembly [511 f B65D 5/58; A476 19/14; C21C 7/00 cludes a vertically mounted, funnel-shaped container [58] Fleld of Search ZZZ/189, 181, 466, 160, with an Opening i i apex having a fine mesh screen 222/356 465; 266/34 T thereover. The screen is used for metering the metal material through the opening in the base of the funnel [561 References C'ted and into the melt composition utilized in a liquid UNITED STATES PATENTS phase epitaxy deposition system. The container is sup- 4o,472 11/1863 Gerhardt 266/34 T ported y a tripod rr ngement connected to a rod for 98,291 12/1869 Nashold 222/466 lowering and raising the dispenser assembly. 1,298,229 3/1919 Levy 266/34 T 1,476,655 12/1923 Strickland 222/189 4 Clam, 3 Drawmg Flgures APPARATUS AND METHOD FOR DISPENSING MATERIALS INTOA MELT COMPOSITION The invention herein described was made in the course of, or under, Contract F336l-73-C-50l7 with the United States Air Force.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an improved simplified means for adding incremental amounts of materials to existing materials in systems utilized for growing single crystals and in particular to liquid phase epitaxy deposition systems.

2. Description of Prior Art Liquid phase epitaxy (LPE). deposition systems for oxide film growth are generally operated in the temperature range of 800l200C. The materials utilized in these systems often require the composition thereof to be changed or replenished during a deposition run as a result of losing melt constituents through deposition and vaporization. These melt compositions consist mainly of compounds dissolved in other compounds. As a result, the rates of evaporation vary substantially at the high deposition temperatures. Melt constituents are also lost through depletion of the constituents as a result of growing crystals from the melt composition. Existing methods for altering or modifying the composition of a melt require removal of the melt composition (in a crucible) from the'furnace, time allowance for the melt to cool, addition of the required amounts of material to the melt, return of the crucible to the furnace and re-establishment of the temperature required to return the melt to its liquid state and stabilization of the melt system. Another method for adding materials to a melt in an LPE deposition system is simply to dispense the required material to the existing melt through a long tube increasing the risk that all the particles of material will not get into the melt without losing the tube or without losing the particles in the tube.

Thus existing methods of adding materials to systems for growing crystals are time consuming, cumbersome,

unreliable and economically not feasible.

SUMMARY OF THE INVENTION This invention relates to a dispenser assembly with a container for carrying and dispensing required melt compositional ingredients to existing materials utilized in systems for growing single crystals such as liquid phase epitaxy deposition systems.

The container has a funnel-like, cone shaped configuration with an opening at its bottom(apex) and includes a porous member for metering the material out through the opening and into the deposition system.

The container is held by a tripod arrangement consisting of three arms, each arm connected to the edge of the container. The three arms are united to one member which is connected to a long rod which serves as a handle for lowering and raising the dispenser assembly when making additions to the LPE deposition system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of the invention.

FIG. 2 is a top view of a container used in the embodiment shown in FIG. 1.

FIG. 3 is a partially cutaway side view of the container shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a perspective view of dispenser assembly 10. The assembly 10 is fabricated of a suitable material (for example pure platinum metal) which is able to withstand the highly corrosive environments and high temperatures associated with LPE deposition systems. Platinum metal can, of course, withstand such temperature. Also platinum will not contaminate materials utilized by the LPE deposition system. In the preferred embodiment of this invention container 12 is a truncated cone-shaped container supported by the tripod arrangement of

arms

20, 22, and 24 which unite with rod 26 and includes a cross bar 30 approximately two inches from the end united with

arms

20, 22 and 24. Rod 28 is used to lower and raise container 12. Rod 28 is a hollow alumina rod that fits over rod 26 and abuts against cross bar 30. Rod 28 is secured to rod 26 by wrapping platinum wire around cross bar 30. Rod 28 is approximately 2 feet long in one embodiment. The length of rod 28 is determined by the LPE deposition apparatus which includes a deep well with a surrounding furnace. The crucible containing the melt composition is maintained in the furnace. Rod 28 must be long enough to lower and raise container 12 from the melt composition in the crucible to a work station available to the operator.

Arms

20, 22, and 24 may be attached to container 12 by suitable mechanical means including welding. The tripod arrangement assures stability of the container and prevents the container from tipping or from losing its charge. Container 12 includes an opening 14 at its apex and a screen 16 (not shown in FIG. 10 as discussed hereinafter.

FIG. 2 shows a top view of container 12 including opening 14 in the base thereof and screen 16 covering opening 14. The screen 16 consists of a suitable porous material such as fine platinum mesh screen which is fused to the interior wall of container 12 at point 18 as shown in FIG. 3. Opening 14 is approximately 0.25 inches in diameter in one embodiment. In one embodiment, the large diameter of the cone is approximately 1.25 inches. Screen 16 assures that the additional compositional ingredients will be accurately dispensed into the LPE deposition system. Prior to adding the required material to an LPE deposition system container 12 is lowered briefly into the melt composition which operates in the 800-1200C temperature range. When the container is withdrawn from the melt composition, flux from the melt composition solidifies in the pores of screen 16 such that container 12, in effect, is without an opening. container 12 may now hold material to be added to the deposition system whether solid or in the liquid state.

Referring to FIG. 3 is a partially cutaway side view of container 12 which shows screen 16 as it lines the interior wall at 18 of the base portion of container 12.

In the use of dispenser assembly 10, container 12 is held rigidly by the tripod arrangement of

arms

20, 22 and 24 at three points on the outer top rim of container 12 as shown.

Arms

20, 22 and 24 are connected to rod 26. Rod 26 is connected to rod 28 which is used as the handle. Screen 16 is fused onto the interior lower surface of container 12 and over opening 14 as shown in FIG. 2. Prior to adding any materials to container 12 it is lowered by rod 28 until container 12 is immersed in 3 a crucible containing some melt composition whose temperature varies from 800l200C. Immediately, container 12 is pulled out of the melt composition.

Flux from the melt composition solidifies in the pores of screen 16 effecting a sealed container. Container 12 is now ready to hold precisely measured material or liquidto be added to a single crystal growing system or a LPE deposition system. The required precisely measured material (within 0.1 of a mg) is placed in container 12. As the dispenser is lowered into the well containing the crystal growing system, the heat from the furnace melts the flux in the pores of screen 16 permitting the materials in the container to flow through the pores of screen 16 and into the melt compositions of the crystal growing system.

Container 12 may be directly immersed into the melt compositon for stirring purposes and for solidifying another coating on screen 16 in preparation for another material addition. Where the material to be added is of a volatile or of a reactive nature, the weighed reactive material may be covered with a material having a lower melting point than the active material e.g. such as lead oxide so that when container 12 is lowered in the well the lower melting lead oxide will tend to melt first and flush out the active material as soon as the flux melts from the pores in screen 16 thereby substantially retarding the rapid evolution of gases. The rate at which the dispenser is lowered can also inhibit the rapid escape of gases from the weighed materials.

Thus it has been shown that a simplified dispenser assembly of the type described herein can receive and dispense precisely weighted amounts of material (to within 0.1 of a mg) to a high temperature corrosive environments with substantially no loss of the material in dispensing.

Once the screen in the container is coated the material in the container to be added cannot be dispensed prematurely. The rigidity of the tripod arrangement also assures that the material will not be lost as a result of the container tipping. The alumina rod gives the dispenser the flexibility of dispensing materials into deep wells which are utilized in the LPE deposition systems. As a result, this invention is not only reliable, stable and safe but eliminates down time periods which consequently is expedient and economically feasible. The embodiment shown and described is illustrative only. It is not meant to be limitative of the invention. Rather, the scope of the invention is to be defined by the claims appended hereto.

What is claimed is:

4 1. A dispenser assembly comprising: a container having an openingandmeans for accommodating material to be precisely dispensed; said container having an inverted cone-shaped configuration with said opening at the apex thereof;

porous means adjacent said opening whereby said fitted over said vertical arm and attached thereto.

so that said cross bar acts as a stop for said hollo rod. 2. The dispenser assembly recited in claim 1 wherein said porous means consists of a fine mesh screen mate rial.

3. A method of dispensing materials into a molten melt by means of a porous container comprising the steps of positioning said porous container adjacent said mol-1 ten melt;

immersing said porous container in said molten melt;

removing said porous container from said molten melt with a coating of the material in said molten melt thereon;

permitting said coating of molten melt to solidify and form a sealing coat on said porous container;

adding a precision measured quantity of materialto i said coated container; lowering said coated container with said material therein into said molten melt; and

permitting heat from said molten melt to melt said sealing coat from said porous container whereby said measured quantity of material is dispensed through said porous container into said molten melt.

4. The method recited in claim 3 including the step of adding a second material having a lower melting point than said measured quantity of material over said measured quantity of material whereby said measured material is flushed through said porous container into said molten melt preventing the rapid escape of gases.

Claims

1. A dispenser assembly comprising: a container having an opening and means for accommodating material to be precisely dispensed; said container having an inverted cone-shaped configuration with said opening at the apex thereof; porous means adjacent said opening whereby said porous means may be selectively sealed for holding material in either the solid or the liquid state and selectively unsealed to permit said material to be dispensed through said opening of said container: means for supporting said container; said means for supporting said container consisting of a plurality of arms attached to said container, a vertical arm connected to said plurality of arms, a cross member connected to said vertical arm, and a hollow rod for lowering and raising said container fitted over said vertical arm and attached thereto so that said cross bar acts as a stop for said hollow rod.

2. The dispenser assembly recited in claim 1 wherein said porous means consists of a fine mesh screen material.

3. A method of dispensing materials into a molten melt by means of a porous container comprising the steps of positioning said porous container adjacent said molten melt; immersing said porous container in said molten melt; removing said porous container from said molten melt with a coating of the material in said molten melt thereon; pErmitting said coating of molten melt to solidify and form a sealing coat on said porous container; adding a precision measured quantity of material to said coated container; lowering said coated container with said material therein into said molten melt; and permitting heat from said molten melt to melt said sealing coat from said porous container whereby said measured quantity of material is dispensed through said porous container into said molten melt.