FR2476689A1 - Liq. phase epitaxy cell - for successive deposition of two layers on substrates, esp. for mass prodn. of LEDs, and using slide which can be sepd. into two parts - Google Patents

Abstract

The cell is used for the successive deposition of two semiconductor layers on one or more semiconductor substrates, which are located in a recess in a flat plate forming a slideway in the base of the cell. A slide consisting of two separate flat plates can travel along the slideway; and one of the plates carries a reservoir filled with one liq., whereas the second liq. remains above the slide. When the slide is moved in one direction, the substrates are exposed to the liq. in the reservoir; then only the sliding plate carrying the reservoir is moved in the opposite direction, so the substrates are exposed to the second liq. in the cell. Used e.g., in mfg. GaAlAs light emitting diodes. The cell is easy to use in the industrial mfr. of semiconductor devices.

Description

"NACELLE USABLE FOR EPITAXIC DEPOSITS
IN LIQUID PHASE AND DEPOSITION METHOD
IN GAME SAID NACELLE "
The invention relates to a nacelle usable in an epitaxial liquid phase deposition device, designed for the successive formation of two semiconductor layers on at least one semiconductor substrate from two liquid solutions, and in which there is, essentially, a flat base. hollowed out of a recess intended to receive said substrate, surmounted by a carriage carrying liquid solutions, which carriage can be moved through the nacelle on said base by unidirectional sliding.

 The invention relates to epitaxial deposits in general, but relates more particularly to deposits of 111-V semiconductor compounds which it is difficult to obtain according to an industrial mode.

 Epitaxial growth in the liquid phase belongs to the known technique. Apparatus for implementing this technique is described in US Patent No. 3,690,965.

The apparatus described in this patent comprises three essential elements
-a reservoir in which the solution is placed
liquid,
-a first flat plate on which the
tank and which forms the bottom of it,
-a second flat plate placed under the prece
tooth and in a recess of which is
the semiconductor substrate to be covered.

 The two plates are movable by sliding relative to one another and relative to the reservoir, in a defined direction.

 The first flat plate is pierced with an opening whose shape and section are substantially equivalent to those of the base of the tank and substantially 8pivalent also to those of the recess where the substrate is located.

 As a first step in the operating process, the base of the reservoir, said opening and said recess are matched. The liquid solution then covers the substrate and fills the opening.

 Then, the two plates are slid integrally with respect to the reservoir in said direction and in a given direction. The substrate in its recess and the opening filled with a small volume of solution are thus removed from the reservoir which is therefore closed at its base. It is from the only small volume of liquid solution limited laterally by the opening that the epitaxial layer is then deposited on the substrate, by the usual means of a controlled drop in temperature.

 The method, according to the aforementioned American patent, consisting of forming an epitaxial layer from a volume of liquid solution arranged in a relatively thin layer above the substrate, has the advantage -as well as indicated in said patent! that the layer obtained is particularly remarkable as regards the quality of its surface condition.

 Unfortunately, the apparatus described, if it allows the simultaneous production of epitaxial layers of substantially identical characteristics on several substrates each arranged in a recess distinct from the second plate, and slil also allows the production of multilayer deposits, is absolutely not suitable for industrial use. Both of these embodiments lead to the use of complex equipment, bulky and inconvenient, the use of ovens having many distinct heating zones and a long and delicate operating process.

 The present invention aims to make available to those skilled in the art an apparatus of an industrial nature, that is to say simple, of easy implementation, making it possible to process several substrates simultaneously.

 According to the invention, a nacelle usable in a liquid phase epitaxial deposition device, designed for the successive formation of two semiconductor layers on at least one semiconductor substrate from two liquid solutions, and in which there is, essentially, a base hollowed out plane of a recess intended to receive said substrate, surmounted by a carriage carrying liquid solutions, which carriage can be moved through the nacelle on said pedestal by unidirectional sliding, is notably remarkable in that said carriage is divided into a first and a second planar elements resting directly on said base and arranged in the extension of one another, the first of these elements supporting a reservoir intended to receive the first of the liquid solutions to be brought into contact with the substrate.

 The reservoir is located in the immediate vicinity of one end of the first planar element, the remaining planar section of this element extending, partly, outside the volume of the nacelle, while the second planar element also extends , partly, outside the nacelle.

 The two planar elements arranged contiguously, at least during part of the epitaxial deposition process, then cover the whole of said base and form, apart from the space occupied by said tank, a rectangular flat reception area for the second of the liquid solutions.

 According to another important characteristic of the arrangement arranged according to the invention, said carriage, measured in a direction perpendicular to that of its movement is longer than said tank.

 Furthermore, the recess dug in the base of the nacelle and intended to receive the substrate (s) is placed in the middle part of said base, the tank having on this base two parking areas provided at two opposite ends of the nacelle according to the sliding direction of the carriage.

 The arrangements described above contribute, taken as a whole, to making the nacelle according to the invention an apparatus permlettant to effect these epita xic deposits according to an industrial mode. Housing the tank at one or the other end of the nacelle - this depending on the operating process - has the advantage of leaving a large place for the recess dug in the base too, can we -provision this long and wide recess and have there several substrates which are thus treated simultaneously and under identical conditions. However, the basket retains reasonable dimensions that allow the ovens to be used in place. Furthermore, the heating zone, which requires very precise adjustment - that in which the substrates are located - remains narrow, which facilitates this adjustment.

 The recess is dug shallow - about two millimeters - and it is planned, in the operating process, that this recess is covered by the first element of the carriage during the deposition of the first epitaxial layer.

The confinement of the substrates under a sheet of thin liquid solution is advantageous, as has been seen previously, in that it promotes obtaining quality deposits. With regard to the deposition of the second epitaxial layer, the very wide layer of liquid solution may have the thickness chosen; it is easy, as during the deposition of the first layer, to make it not very thick.

 The nacelle, of simple structure, also offers the advantage of being easy to implement, its control requiring only two interventions after introduction of the nacelle into the oven.

 Indeed, the deposition method using said nacelle is characterized in particular in that, firstly of the operating process prior to the deposition of the first epitaxial layer, the first and the second elements of the carriage then placed contiguous are miis relative to the base so that the tank filled with the first liquid solution and disposed on a first of its two parking areas, is transported on the second of these two areas Q the opposite end of the nacelle, and in this that, in a second step of the same operating process, after the deposition of said first layer, the first element of the carriage is moved alone relative to the base and in the opposite direction to that of its first movement so that the reservoir is transported again on the first of its two parking areas, the two elements of said carriage being thereby separated.

 The deposition process is further characterized in that the first liquid solution is distributed, at least in part, from the reservoir into the recess where the substrate / s lie / s during said first time, the second solution liquid, initially and mainly retained on the second element of the carriage, then flowing, along the reservoir, onto the first element of this carriage where it remains during the deposition of the first epitaxial layer.

 The second liquid solution is partly distributed in the recess during said second time in replacement of the remainder of the first liquid solution which then enters the tank.

 The epitaxial deposits obtained with a nacelle according to the invention are of high quality, remarkable in particular by their surface condition comparable to that of deposits produced by epitaxy in the vapor phase.

 The nacelle according to the invention is suitable for the formation of epitaxial deposits on any substrate suitable for this kind of deposit. Although designed for the epitaxial deposition of 111-V materials, in particular GaAlAs, in view1 for example, of the manufacture of light-emitting diodes, it is of useful use in all cases of deposition of semiconductor compounds on the scale industrial.

 The description which follows will make it possible to understand clearly how a nacelle according to the invention is structured and how this nacelle is used.

 Figure 1 shows such a nacelle seen from above.

 Figure 2 is a sectional view along the line II-II in Figure 1.

 FIGS. 3A, 3B and 3C illustrate three successive phases of the operating process leading to the formation of two epitaxial layers on substrates treated in a nacelle according to the invention.

 The nacelle according to the invention is intended to be used in an epitaxial deposition device of conventional structure, well known to those skilled in the art, comprising in particular a horizontal enclosure in which said nacelle is placed, and a heating oven . Only the nacelle object of the invention is shown in the figures.

 The nacelle 1 of Figures 1 and 2 comprises a container or crucible 10, of parallelepiped shape, on the bottom of which is a plate 11. This plate 11, which is hollowed out in its middle part of a rectangular recess 12 intended to receive semiconductor substrates form the base of the nacelle. On the base 11 rests a carriage 13 which crosses the walls of width 101 and 102 of the crucible 10. The carriage 13 can be moved by sliding on the base 11 (from right to left and vice versa in Figures 1 and 2), by example using a hook which is introduced into the end hole 14. Advantageously, the carriage 13 is held, laterally with respect to its direction of movement, in grooves 15 machined in the thickness of the walls of length 103 and 104 of crucible 10.

 According to the invention, the nacelle 1 is characterized in particular in that said carriage 13 is divided into a first, 131, and a second, 132, planar elements resting directly on said base 11 and arranged in the extension of one of the other, the first of these elements supporting a reservoir 16 intended to receive the first of the liquid solutions 2 brought into contact with the substrate.

 For reasons of ease of machining, assembly and disassembly of the nacelle, the side partitions of the tank 16 are provided removable relative to the planar element 131 of the carriage 13. They form a monolithic assembly 17 which is adjusted in a groove 18 of said element. It is also for machining reasons that the base 11 is produced in the form of a removable plate that is slid into the bottom of the nacelle 1; in fact, the bottom of the nacelle is also part of the base.

 The reservoir 16 touches the base 11 through a rectangular opening 133 pierced in the element 131. Advantageously, the edges of this opening perpendicular to the direction of movement of the carriage are chamfered, in order to facilitate the distribution of the first liquid solution and the recovery of the remainder of this solution after the deposition of the first epitaxial layer.

 The reservoir 16 is located in the immediate vicinity of one end 131A of the first element, the remaining flat section of this element extending partly outside the volume of the nacelle. The second planar element 132 also extends partly outside the nacelle.

 The two planar elements 131 and 132 can be arranged contiguous as it appears in FIGS. 1 and 2, the contact being made along a line 19 (drawn in double line in these figures to clearly distinguish the two elements). They then cover the entire base 11 and form, apart from the space occupied by the tank 16, a reception area 20, flat, rectangular.

 The tank 16 does not occupy the entire width of the planar element 131. Corridors 21 remain on the area 20 between the walls of the tank and the walls of length 103 and 104 of the nacelle.

 Furthermore, the recess 12 dug in the base 11 is located in the middle part of said base, the tank having on this base two parking areas 111 and 112 provided at the two ends of the length of the nacelle, at the edge of the recess 12.

 The parts constituting the nacelle 1 are, for example, made of graphite, as is usually done.

 Reference is now made to FIGS. 3, which correspond to the explanations which follow concerning the implementation of the nacelle 1.

 In these explanations, it has been deliberately disregarded certain particular chemical or physical considerations such as, for example, the nature of the liquid solutions, that of the substrates, the temperature, the time, which presides over the elaboration of an epitaxial deposit. given according to the conventional method, well known to those skilled in the art. The process is studied only under the single aspect of the use of the nacelle.

 Before the deposition of the first epitaxial layer, the nacelle is as it was shown in FIG. 3A.

Substrates 30 rest in the recess 12. The carriage 13 is pulled so that the reservoir 16 is then placed on the parking area 111, in contact, or almost in contact, with the wall 101 of the nacelle. The two planar elements 131 and 132 of the carriage 13 are arranged contiguous. The reservoir 16 contains the first liquid solution 161 while the second, 162, of liquid solutions is spread over the whole of the reception area 20, where it is distributed for the most part on the flat element 132.

 In the first stage of the operating process, the carriage 13 is moved through the nacelle, from right to left, until the tank 16 comes to be placed on the parking area 112 at the opposite end of said nacelle; it is then practically in contact with the wall 102. During the movement of the carriage, the reservoir 16, open at its base when it passes over the recess 12, lets there flow at least part of the liquid solution 161 which thus covers the substrates 30. The planar elements 131 and 132 remain contiguous during this movement. Also the liquid solution 162 remains retained on the carriage; the movement of this carriage pushes it from the left to the right of the tank 16, it borrows to flow the corridors 21 and is finally resting, for the most part, on the planar element 131. there it looks as shown in Figure 3B.

 After a rest period during which a first epitaxial layer grows on the substrates 30 from the solution 161, and in a second stage of the operating process, the carriage 13 is pulled into the nacelle from left to right until that the tank 16 rests again on the parking area 111 (see figure Suc). It is the only planar element 131 of said carriage 13 and the reservoir 16 which is integral therewith which then move; element 132 remains in place, almost out of the nacelle. The liquid solution 162 is introduced into the opening created between said elements 131 and 132 which are then separated and comes to replace, in the recess 12, the liquid solution 161 which is recovered in the tank 16.

The second epitaxial layer is then grown on the substrates 30.

 The structural arrangements adopted in the nacelle according to the invention make it possible, due to the large space reserved for the recess 12, to treat a large number of substrates simultaneously. As an indication, in a basket used by the Applicant and measuring, overall, substantially 40 x 10 cm l'év the recess occupies 150 to 200 cm2 and one can treat there eight to ten substrates, this using the ovens in place. An increase in capacity would be possible without changing anything in the structure of the nacelle except in its dimensions, provided, it goes without saying, that the capacity of the oven in which it is placed is increased in parallel.

Claims (8)

- CLAIMS  1.- Nacelle (1) usable in an epitaxial liquid phase deposition device, designed for the successive formation of two semiconductor layers on at least one semiconductor substrate (30) from two liquid solutions (161,162), and in which distinguishes, essentially, a flat base (11) hollowed out of a recess (12) intended to receive said substrate, surmounted by a carriage (13) carrying liquid solutions, which carriage can be mt through the nacelle on said base by unidirectional sliding, characterized in that said carriage (13) is divided into a first (131) and a second (132) planar elements resting directly on said base (11) and arranged in the extension of one another , the first (131) of these elements supporting a reservoir (16) intended to receive the first (161) of liquid solutions to be in contact with the substrate.  2. A nacelle according to claim 1, characterized in that the reservoir (16) is located in the immediate vicinity of an end (131A) of the first planar element (131), the remaining planar section of this element extending, for part, outside the volume of the nacelle, while the second planar element (132) also extends, partly, outside the nacelle.  3.- Nacelle according to one of claims 1 and 2, characterized in that the two planar elements (131,132) arranged contiguously (19), at least during part of the epitaxial deposition process, then cover the whole of said base and form , apart from the space occupied by said reservoir, a rectangular rectangular reception area (20) for the second of the liquid solutions (162).  4. A nacelle according to one of the preceding claims, characterized in that said carriage (13), measured in a direction perpendicular to that of its movement, is longer than said tank (16).  5. Nacelle according to one of the preceding claims, characterized in that the recess (12) hollowed out in the base (11) of the nacelle and intended to receive the substrate / s / s (30) is placed in the part average of said base, the reservoir having on this base two parking areas (111,112) provided at two opposite ends of the nacelle in the sliding direction of the carriage.  6.- epitaxial liquid deposition process for the successive formation of two semiconductor layers on at least one semiconductor substrate, using a nacelle according to all of claims 1 to 5, characterized in that, in a first time of the operating process prior to the deposition of the first epitaxial layer, the first (131) and the second (132) elements of the carriage (13), then placed contiguously (19), are ripe relative to the base so that the reservoir (16) filled with the first liquid solution (161) and placed on a first of its two parking areas (111), or transported on the second (112) of these two areas at the opposite end of the nacelle, and by that, in a second step of the same operating process, after the deposition of said first layer, the first element of the carriage is moved alone relative to the base (11) and in the opposite direction to that of its first movement so that let the tank be tra nsporté again on the first (111) of its two parking areas, the two elements of said carriage being thereby separated.  7.- Method according to claim 6, characterized in that the first liquid solution is distributed, at least in part, from the reservoir into the recess where the substrate / s lie / s during said first time, the second solution liquid, initially and mainly retained on the second element of the carriage; then flowing, along (21) the reservoir (16), on the first element of this carriage where it remains during the deposition of the first epitaxial layer.  8.- Method according to claim 6, characterized in that the second liquid solution is partly distributed in the recess during said second time in replacement of the remainder of the first liquid solution which then enters the tank.