DE8902307U1 - Device for thermal treatment of semiconductor materials - Google Patents

Description

Dr.Heinrich Söhlbrand',' WiVtsbaiieVnstraBe '26, D 8027 Neuried

Dr.S/s 0189G February 27, 1989

DEVICE FOR THE THERMOSTATIC TREATMENT OF SEMICONDUCTOR MATERIALS

The innovation relates to a device for the thermal treatment of semiconductor materials in which the semiconductor wafers or similar process gas mixtures to be treated are exposed to different and changing compositions and temperatures, whereby a vertically arranged process chamber is provided with a process tube that is open on one side and a heating cassette that cylindrically surrounds the process tube, in which the semiconductor wafers to be treated are arranged on a carrier, as well as a fluid flush provided in an annular chamber that surrounds the process tube.

Devices for carrying out such processes are also generally known under the term "diffusion furnace". They essentially consist of a process tube surrounded by a heating cassette and the loading device, usually a so-called cantilever system. Such diffusion furnaces are usually used as horizontal furnaces, i.e. the process tube is arranged horizontally and is loaded from the front with the semiconductor wafers to be treated. Vertical furnaces are also known in which the process tube is arranged vertically and which are loaded with the semiconductor wafers from below or from above. The known vertical furnaces essentially consist of the vertically arranged process tube, which is surrounded by a heating cassette.

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conventional design. The semiconductor wafers are stacked vertically on top of each other in the process tube in a hanging or standing tray at process-related intervals, but aligned horizontally. In the process tube they are subjected to heat treatment with different process gases that flow through the reaction chamber from bottom to top. The reaction chamber is largely sealed against the surrounding clean room atmosphere at its open end, bottom or top, by means of loosely placed closure elements with integrated gas supply and discharge lines. When carrying out the process, which is _adapted to the device, gas displacement flushing is used.

The disadvantages of such devices and the processes carried out in them are obvious. In particular, it is the inherent technological disadvantages that have a negative impact on the yield, such as the undefined gas atmosphere and regularly occurring back diffusion, which make it impossible to reproduce the process parameters and thus the process result from batch to batch. Other technological disadvantages are the unattainable isotherm in the reaction chamber, the lack of vacuum-tight separation of the reaction chamber from the outside world and a gas flow with significant defects that is characterized by thermals, convection and laminarity. In other words, the known processes and devices of this type are uneconomical, have a high material wear and are subject to a high risk of breakage. This is where the innovation aims to remedy the situation. The innovation, as characterized in the claims, Iöä'u the

Dr.Heinrich Söh!brand*, WiVtebauer'nstrebe 2&bgr;, D 8027 Neuried

The aim is to reliably avoid the disadvantages described above and to have a device for carrying out such processes which is adapted to the reading and in which the gas flow within the reaction chamber is controllable.

The innovation achieves several advantages at the same time. By influencing the process gas flow inside the process tube, i.e. in the reaction chamber, the yield is not only improved, but the process conditions and thus the reproducibility of the same are also ensured. In particular, the gas flows are not always directed at the same point on the semiconductor wafers to be treated, as was previously the case, thanks to the arrangement of the turbulence nozzles in the wall of the process tube, but rather they hit the surface of the semiconductor wafers at constantly changing angles. In addition, the inclined position of the semiconductor wafers on the rack ensures that no undesirable gas concentrations form on certain parts of the surface. Another advantage is the overall flow direction of the gas flows from top to bottom, i.e. the gas is removed from the bottom of the process chamber and cannot collect at the top or in other places. The use of inert purge gases to prevent any contamination from the area of the heating cassette is a further advantage. This means that no molecular or atomic contaminants can enter the reaction chamber. The effective cooling by purge gases in the inner and intermediate spaces contributes to rapid batch turnover and thus to the economical implementation of such processes. The device is adapted to the process conditions and has

Dr.Heinrich SOhlbrand, Wl rtebatie'rnetra&e'26, D &THgr;&Ogr;27 Neuried

In addition to a multi-pipe system consisting of an inner and an outer reaction tube, in particular a rotating turntable for the semiconductor wafers to be treated during the process, there are turbulence nozzles provided on the wall of the inner process tube for the introduction of the process gases into the process chamber.

The system design also has the advantage of being particularly suitable for carrying out heat treatment processes on a few or only a single semiconductor wafer, even very large ones (single-wafer processes or cassette-to-cassette single-wafer processes).

The innovation is explained in more detail below using the exemplary embodiments shown in the figures.

It shows:

Figure 1 shows a longitudinal section through the renovation Contraption.

Figure 2 shows a variant (W Figure 1, Figure 3 shows another variant, Figure 4 shows a complete diffusion furnace and Figure 5 shows a variant of the diffusion furnace.

The device shown in Figure 1 represents the main component of a so-called diffuser, namely the actual process unit, which essentially consists of the inner process tube 1, the outer process tube 2, which are preferably made of quartz, the jacket tube 3, for example made of ceramic, the heating cassette 4 with the additional heating elements 17

Dr. Heinrich Söh!brand. We tSbauWcnfftfäfte, <2C{ 1 ^: D 8027 Neu r led

and 18 as well as the reaction chamber sealing system 15 and the rotary table 14.

The approximately bell-shaped heating cassette 4 is still enclosed on the outside by the hood 6. This hood 6 has an opening at its upper end for the purge gas outlet nozzle 24 and the cooling gas outlet nozzle 25 of the heating cassette casing cooling 5.

In the cavity 9, the so-called Pfözessyää-Zwi »&Ogr;&iacgr;&idiagr;&ogr;&Pgr;&Ggr;&aacgr;&udigr;&iacgr;&idigr;&idigr;, the flowing process gas is always under a slight overpressure in order to achieve a good distribution of the process gas mixture before it is blown into the reaction chamber 8. The process gas is introduced through at least one row of holes 7 into the inner isothermal reaction chamber 8 in such a way that the semiconductor wafers 11 located on the rotary table 14, i.e. its wafer carrier 13 with its wafer holders 12, are surrounded on all sides by the process gas. The rows of holes 7 are therefore preferably provided in a helical shape with different pitches and an indeterminate number of holes in the wall of the inner reaction tube 1, with the diameters of the holes being approximately 0.5 mm or larger and the spatial axis of the holes being disoriented relative to the central tube axis. The semiconductor wafers 11 are stacked on top of one another on the wafer holder 12 in a slightly inclined arrangement so that their entire surface is exposed to the gas flow from the row(s) of holes 7 during treatment. A batch consists of a typical batch size of 25 semiconductor wafers 11 plus a few dummies. In non-critical processes, more semiconductor wafers can also be fed in and treated at the same time.

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The process gas mixture is introduced into the process gas space 9 through the El &eegr; IcBstutzen 28 and removed from the system again through the process gas outlet IaBrohr 30.

Between the outer reaction tube 2 and the ceramic tube 3 carrying the heating cassette 4, an outer ring-shaped flushing chamber 10 is provided, through which flushing ^gas flows in so-called "low-flow mode ^" or "high-flow mode" in order to prevent the reaction chamber from being contaminated by components of the heating cassette 4 in "low-flow mode" with a few liters of flushing gas per minute, on the one hand, and to achieve rapid cooling in "high-flow mode". In this way, the entire system is quickly cooled to temperatures well below the previously usual stand-by temperatures of 700° to 800° C. Stand-by temperatures of 300° C and below (down to room temperature) can thus be achieved, i.e. the so-called "fast heating cassette" is thus realized. Between the outer casing of the heating cassette 4 and the hood 6 there is a further cooling chamber 5 which surrounds the heating cassette 4 and has at its base at least one tangential blow-in nozzle 19 for the jacket cooling which, after flowing through the cooling chamber 5, leaves it again through the nozzle 25. The hood 6 which serves as the heating cassette casing is designed to be suitable for use in a room, for which stainless steel is well suited.

Below the reaction tube 1 there is a process gas preheater 16, which is designed as a cylindrical, double-I-walled ring with a wide flange and supports the reaction tube 1. A heating element 16 is integrated into this ring as well as one or more

Dr.Heinrich Sohlbrand^Wlrt^aifarnktfaBd ZS, D 8027 Neuried £

Process gas inlet and outlet nozzles 28 and 30 respectively. For rapid system cooling, at least one gas inlet nozzle 27 is also provided for purge gas. The heating element 17, arranged below the reaction tube 1 in the reaction chamber closure system 15, is supported by a support ring 21.

The process gas preheater 16 contains a cylindrical heating element 18 and has one or more process gas inlet channels 28 in its collar, which is formed as a flange made of -. The pot-shaped cavity 20 located by the reaction chamber closure system 15, below the disk-shaped heating element 17, is filled with quartz, rock wool or the like. The support tube 21 is arranged on the support tube bearing shell 22 with integrated cooling made of heat-resistant, lubricant-free material, such as ceramic, with the air cooling cooling the bearing 35 made of ceramic or metal or plastic. A flange connection is designated by 26.

The entire system 1 to 28 is supported by a common mounting device 29, to which a water cooling channel 31 and an air cooling channel 32 are also attached.

The coaxial support tube 33 of the turntable 14 is provided with an air cooling tube 33a on the inside. This support tube 33 i β t is mounted in the bearings 34 and 35. An inert gas purge i 81 is provided in the protective tube 36 and has an extraction device with a multi-way valveI.

The drive 37 of the turntable 14 is arranged in the frame 40, which supports the system that can be inserted into the reaction tube unit from below and is guided in bearings 39 on the rail system 38. The rail system 38

T:

Dr.Heinrich Söhlbrand, Wl rtsbauernstraBe "26, O 8027 Neuried Is attached to the frame 41.

The cylindrical closure system of the reaction chamber, designated 15, has a multiple function. Firstly, it serves to seal the reaction chamber 8 on the loading side, i.e. from below, in a vacuum-tight manner. It carries the adjustable heating element 17, which is required to maintain the isothermal temperature and is fixed in the position shown by the support ring 21. The closure system 15 is preferably made of semiconductor-compatible material, for example quartz, poly-silicon, SiC or other

&ogr; Ceramic material, which can withstand temperatures well over 1300 C must be dimensionally stable.

While according to Figure 1 the turntable 14 together with the closure system of the reaction chamber 8 is moved into the stationary reaction tube 1 from below after loading with semiconductor wafers 11, the variant shown in Figure 2 provides that the complete reaction unit, consisting of the inner reaction tube 1, the outer reaction tube 2, the jacket tube 3, the heating cassette 4 with the hood 6 and the supply and discharge lines 27 for the purge gas and the jacket cooling 5, is moved upwards while the turntable 14 remains stationary. For this purpose, the closure system of the reaction chamber 15 is again held in the frame 40 and the frame 41 for the rail system 44 is arranged to the side. A holding plate 42 with two ring flanges carries the movable reaction unit and slides over the sliding bearings 39 on the bars of the rail system 44. 43a is the upper ring flange and 43b the lower ring flange. An inner, adjustable heating cylinder 45 is provided below the turntable 14. The preheating of the

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Or.Heinrich Sohl brand, Wirtsbauernstrasse 26, D 8027 Neurl ed

Process gases according to Fig. 2 are ensured by the arrangement of the heating elements 45 and 46 and the process gas inlets and outlets 28 and 30 provided in the closure system 15 of the reaction chamber 8. The closure plate of the pipe closure system is designated 47. This carries the adjustable heating elements 17, 45 via 46, arranged in such a way that the process gases flowing in from below are preheated and condensation of exhaust gases flowing out downwards in the overall system is prevented. Remaining cavities are filled with quartz wool inside the jacket 48 in order to ensure the necessary thermal insulation. Finally, an annular seal 49 with fluid cooling is provided.

A further design variant is shown in Figure 3. It shows in particular a different design of the process gas preheater 16 according to Figure 1, or 17, 45 and 46 according to Figure 2.

The process gas preheater according to Figure 3 consists of the cylindrical heating element 50 and a U-profile-shaped ring flange 51, which can optionally also be composed of individual segments, and a heating element 52. This heating element 52 can be formed from individual, rod-shaped heating elements forming a ring, as well as from a heating coil wound around the U-profile-shaped flange 51, or from individual insertable heating element segments that are adapted to the U-profile-shaped ring flange 51. Such an arrangement of the heating elements 50 and 52 enables rapid exchange and easier adaptation to different process parameters.
Figure 4 shows the side view of a diffuser furnace with vertical, stationary reaction unit and

■Heinrich Söhlbrand, Wl rtsbauernstrasse 26, D 8027 Neuried

downwards movable turntable 14.

A robot 54 is mounted on a clean room table 53, outside the actual reaction unit, as described in Fig. 1, which automatically loads and unloads the turntable 14. The turntable 14 is loaded with semiconductor wafers 11 - top left in the picture - and, after being lowered, is moved to the right using the displacement device 56 in order to move to the right and upwards into the reaction tube 1. 55a and 55b designate blowers, including filter units, to ensure that during the up and down and translation movements in the tunnel under the clean room table 53 the wafers are only moved in clean room air of class 1-5.

Figure 5 shows a diffusion furnace according to Figure 2 with a stationary turntable 14 and a reaction unit that can be moved upwards. For loading and unloading, the reaction unit is raised so that the robot 54 can insert the semiconductor wafers 11 into the turntable 14 or remove them from it.

The process sequence in reaction tube 1 (oxidation, H, tempering, diffusion, deposition) is as follows:

Example 1: Oxidation (explained using Fig.4)
First, the inner isothermal γ reaction chamber 8 is heated to starting temperatures between room temperature and
300° C and the turntable 14 is loaded with semiconductor wafers 11 by the robot 54 removing these wafers from a storage rack (not shown) and placing them in wafer holders 12 of the wafer carrier 13. The wafer holders 12 are preferably round and are stable up to well over 130 ^° C. Slipping of the inclined wafers

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Dr. Heinrich Söhlbrand, Wirtebauernstrasse 26, D 8027 Neuried

11 is avoided by a stop in the disk holder. The turntable 14 then moves downwards and then to the left, before moving upwards again into the reaction chamber 8 of the reaction unit, as can be seen in Figures 1 and 4. In the design variant according to Figures 2 and 5, the turntable 14 remains stationary, but the reaction unit with the reaction chamber 8 is raised so that the loading process can be carried out by the robot. After loading is complete, the reaction unit is lowered again.

After the semiconductor wafers 11 to be treated have been introduced into the inner reaction chamber 8, a gas exchange is first carried out, whereby the initially largely atmospheric composition of the gases (in the reaction chamber 8) is exchanged for the process gas mixture already heated by the process gas preheater 16 by means of a "soft pump-down" step, i.e. by evacuating once or several times and refilling with the desired process gas mixture. The exchange of gases takes place through the process gas inlet nozzles 28 and the process gas outlet pipe(s) 30. The pressure in the inner reaction tube 8 is set to the required values depending on the process. O /HCL in a ratio of 97/3 vol.% is very suitable as a process gas mixture, for example. The process gases flow through the process gas intermediate chamber 9, which is constant with a slight overpressure and through the holes 7 in the wall of the inner reaction tube 1 into the inner reaction chamber 8, where they, always flowing downwards, hit the surface of the semiconductor disks 11 rotating obliquely in the gas flow with the turntable 14. By the heating cassette 4 and the heating element 17

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Or .Heinrich Son ibf and',' WiVisbaueVfist r«Be'26, D 8027 Neurfed

If the temperature is raised to 800° C, the temperature in the inner reaction tube rises to 800° C. During this so-called "ramp-up" phase, the surface and the lattice sites near the surface of the semiconductor wafers 11 are decontaminated, particularly through the action of chlorine. After a certain dwell time at 800° C, further "ramp-up" takes place up to the actual process temperature of around 900° C. Now the flow of chlorine gas is stopped and the oxidation phase is initiated, which takes place in three or four variants, some of which can also be connected in series:

I.Introduction of dry O^, or

2.Introduction of moist O ₁ , �O _λ /�EEgr; ₂ 1 : 1.7

3.Introduction of dry O _x , with inert gas

(e.g. Ar) diluted,

4. Introduction of dry or moist Q, with or without inert gas (e.g. Ar), but under low pressure, i.e. variants 1 to 3, but with reduced working pressure and other independently variable process parameters.

The variants like 4. are particularly suitable for producing thin gate oxide layers of about 2-10 nM (20 - 100 X) with the best possible reproducibility and the lowest process tolerances. The oxidation is terminated by repeating the process gases with N ₁ by means of another "soft pump down" step. This is followed by a linear "ramping down" to about 800°C and a different length of time at this temperature. Now the process gas inlet nozzle 27 and outlet nozzle 24 are switched from "low flow mode" to "high flow mode" using N ₁

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Dr,Heinrich Sflhihrand, Wfrt«bau»rneJfcraS*e.^ft _$ 'D 8027 Nteurled

&ogr; switched to "quickly heat up the entire system to about 300 C, or, depending on the process, to room temperature.

After this temperature has been reached, the treated semiconductor wafers 11 are moved out again with the turntable 14, or the reaction unit is lifted and replaced by the robot 54 with a new batch, and the process now begins again. As a result of the vacuum-tight reaction chamber 6, other process variants can also be carried out during oxidation that were previously not possible with the known vertical devices. For example, it is possible to use the device to carry out low-pressure oxidation or low-pressure oxidation while simultaneously diluting the residual gas atmosphere with inert gas (e.g. N, Ar, He, Kr, Xe, etc.). With both variants, perfect control of the oxide growth under extreme conditions is possible, i.e. even small growth rates can be achieved with extremely thin oxide layers.

ten (ZO - 100 A) can be achieved if in-situ surfaces are offered.

By introducing an external flushing chamber 10, which can be operated in "high-flow" and "low-flow ^" mode, it is ensured that the heating cassette 4 cannot contaminate the reaction chamber 8. A flush with a few liters of flushing gas per minute ("low-flow" mode) is sufficient. When using the "high-flow" mode, ie flow of large quantities of flushing gas, a rapid cooling of the heating cassette 4 and thus of the entire system is possible within a very short time. The stand-by temperatures of 700° - 800° C, which could not be undercut or were usually maintained, are very quickly reduced linearly or

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.Heinrich Sohlbrarcd-iWirtSDfcdefnstf &Agr;&bgr;&bgr;.,26, D 8027 Neuried

exponentially reduced to approx. 300 C and below or room temperature (so-called "snap heating cassette"). The turntable 14 rotates slowly during the entire process, with possibly changing angular speeds, with the semiconductor wafers 11 in the radial gas flow that is between the semiconductor wafers. &lgr; r* K &agr; i K^n uortal H iinH cnmlfr ria r an noeamto OHo rf I Arha

In this way, an extremely uniform, reproducible process result is achieved. The turntable 14 is preferably made of poly(vinyl chloride),

Ceramics or other conductive materials,

&ogr; like 7.B. SiC or others and is up to well over 1300

C forrnstjbU, designed as a disk, which has a downwardly projecting coaxial support tube 33 made of the same material with double bearings 34,35 with internal 33a and external 22 cooling.

Example 2: Tempering. First, the Turntable 14 is loaded as in the LJÜ 1OfSIVI I UGOVIII IWt7l1.

The tempering of semiconductor wafers is carried out in the device, which is an absolutely closed, vertically arranged furnace system, has clearly defined gas inlet and outlet openings and enables both the start and termination of the process carried out therein at room temperature, in 100% pure hydrogen in a cold-hot-cold cycle. This is possible because the advantages of the innovative device advantageously allow a process to be carried out with assured gas exchange (first undefined clean room air is exchanged for N ₂ , and then the nitrogen for 100% pure H 2 ) at room temperature, ramping up to the

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Dr. Heinrich Söhlbrand, Wirtsbauernstraße 26, D 8027 Neuried

desired drag temperature (typically: 420°- 490 ⁰ C or higher), process-dependent dwell time at

this temperature and then defined cooling in the 100% H^ atmosphere to room temperature and then - still in the closed system - exchange of this 100% H ₂ for N ₂ and then, after an appropriate purging time with purge gas, exchange of the same for the clean room atmosphere for discharging as in Example 1.

Example 3: Diffusion, coating with dopant. A further advantage of the device according to the innovation is that, for the first time in conjunction with the "soft pump-down" step, at any predeterminable time during the process, the clearly defined immediate termination of coating with dopant, ie the immediate termination of the feeding of the dopant into the reaction chamber 8 and the spontaneous extraction of this dopant gas mixture from the reaction chamber 8, can be brought about. In this way, even very low doping with minimal penetration depths xj and high layer resistance values RgSVa , ie the lowest surface concentrations, can be achieved. In any case, a significantly better process quality and reproducibility is achieved by the device according to the innovation. The design of the inner process tube 1, which acts as a so-called Injector tube is designed, because through this measure the entire system is adapted from the outset to the so-called "in-cage" process control, ie for all processes of oxidation, tempering, diffusion/coating, drive-in, deposition etc. the so-called "cage boats" are no longer required. Disc carriers are placed in these

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Dr. Heinrich Sohl brand',' 'fri V tebatuern Straße «26, D 8027 Neuried

in closed cylinders with end plates and several rows of holes in the cylinder surface (for the process gas inlet). The disadvantages associated with this "cage-boat" technology in process control, namely the fixed position of the semiconductor wafers relative to the holes in the rows of holes and the resulting uneven flow, are excluded in the device proposed according to the invention. The semiconductor wafers 11 and the rows of holes 7 are arranged at an angle to one another, with the semiconductor wafers being in a rotational movement relative to them and thus also relative to the injection flow on the turntable 14.

In this way, the tightest process tolerances and the best possible reproducibility can be achieved in semiconductor technology, which can be used to advantage in CVD processes of all kinds; because these processes are extremely dependent on the flow conditions in the reaction chamber 6 and the variable rotation speed of the turntable 14 and the reaction tube 1 as a "cage boat" replacement. Of course, the smallest possible diameter ratio of reaction tube 1 / semiconductor wafer 11 (Qw^) ^ 1»3 - typically 1.26 to 1.2 and, depending on the diameter of the semiconductor wafers 11, even smaller - also contributes to the advantages of the vertically operating device proposed in the innovation.

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Or. Heinrich Söhlbrand, Wirtsbauernstr. 26, 8027 Neuried

STOCK LIST

1 - Inner process pipe

2 - outer process pipe

3 - Jacket pipe

4 - Heating cassette

5 - Heating cassette jacket cooling

6 - Hood

7 - Rows of holes

&dgr; - reaction space 9 - cavity?« so-called process gas space

10 - outer ring-shaped flushing chamber

11 - Semiconductor wafers

12 - Disc holder

13 - Disc carrier

;4 - Turntable = Turn table

15 - iteaktiwisraumverschlüsse-System

16 - Process preheater

17 - Heating element (adjustable, disc-shaped)

18 - Heating element

19 - Injection nozzle (tangential, for jacket cooling?

20 - Cavity

21 - Support tube

22 - Cooling chamber with inlet nozzle (with tangential injection)

and outlet nozzle

23 - Support tube bearing shell with integrated cooling

24 - Purge gas outlet nozzle

25 - Cooling gas outlet

26 - Flange connection

27 - Purge gas inlet nozzle

28 - Process gas inlet nozzle

29 - Mounting device

30 - Process gas outlet nozzle

31 - Water cooling channel

32 - Air cooling duct

33 - Support tube

33a) Air cooling (for the support tube 33)

Dr. Heinrich Söhlbrand, Wirtsbauernstr. 26, 8027 Neuried

34 - Warehouse

35 - Warehouse

36 - Protection (cooling/extraction) pipe

37 - Drive

38 - Rail system

39 - Warehouse

40 - Frame

41 - Frame

42 - Holding plate

43 a) upper ring flange

43 b) lower ring flange

44 - Rail system

45 - Heating cylinder (inner, adjustable)

46 - Heating element, adjustable

47 - End plate

48 - (Steel) Mantle

49 - Seal, ring-shaped (with fluid cooling)

50 - cylindrical heating element

51 - U-profile ring flange

52 - Heating element

53 - Cleanroom table

54 - Robots

55 a) Blower with filter units 55b) Blower with filter units

56 - Shifting device

Claims (5)

fl f · ·· &igr;,,, Dr. Heinrich Sohl brandT'Wi Vtsbä'ueMieträS'e '28, D 8027 Neuried DEVICE FOR THE THERMAL TREATMENT OF SEMICONDUCTOR MATERIALS Protection claims 1. Apparatus for carrying out processes for the thermal treatment of Ha I at termati Mallen, di ·? a vertically arranged isothermal process chamber with a process tube open on one side and a cylindrical heating cassette enclosing the process tube, the semiconductor wafers to be treated being arranged on a carrier located within the process chamber, and a fluid flushing provided in an annular space enclosing the process tube, characterized in that several process tubes (1,2,3) with hollow spaces (9,10) remaining between them are provided, the inner process tube (1) encloses the reaction chamber (8) and is equipped with several turbulence boxes (7) in its wall and a turntable (14) is arranged in the reaction chamber (8) which can be moved in and out by means of a relative movement relative to the process tube (1), the process tubes (1,2,3) are surrounded by several heating devices, of which the heating cassette (4) encloses the reaction chamber (8) laterally and above, while the heating block (17) is inserted into the closure element (15) of the reaction chamber (8) and the process gas preheater (16) surrounds the heating block (17) outside and is centrally connected to the 17 Dr. Heinrich Söhlbrand,:.WI:rteb^vef;n8i rlaßfe '&iacgr;&bgr;, D 8027 Neuried Drive shaft of the turntable (14) is penetrated. 2. Device according to claim 1 , characterized in that
that a process gas preheater 16 is provided. 3. Device according to claim 1 and 2, characterized in that it is designed to carry out "in-cage" processes by equipping the inner process tube 8 with one or more rows of holes 7 as inlet openings for the process gases. 4. Device according to claims 1 to 3, characterized in that the turntable 14 is arranged stationary, while the reaction unit can be moved upwards. 5. Device according to claims 1 to 4, characterized in that the reaction unit is arranged stationary, while the turntable 14 can be moved downwards and sideways on rails 56 to a table 53 with a robot 54 for loading and unloading in a clean room atmosphere. 18