GB2148471A - Thermal treatment apparatus and method - Google Patents

Abstract

In a method of subjecting semi conductor wafers to a thermal treatment in a furnace tube (102) a horizontally extending carrier (141) having a portion (141a) adapted to a plurality of wafer jigs thereon is moved to a predetermined position (Fig. 10B) in the furnace and the wafer jigs are located at this position. The carrier is then withdrawn to another position close to the opening of the furnace tube (Fig. 10C) and the opening of the furnace tube is closed by inner and outer caps (143, 144). The wafers on the jigs are subjected to thermal treatment while the carrier (141) is advanced and withdrawn periodically to and from the said predetermined position to lift of wafer jigs to prevent fusion of the jigs to the tube. The apparatus includes means for automatic control of the movement of the semi conductor wafers in accordance with thermal treatment conditions. <IMAGE>

Description

SPECIFICATION Thermal treatment apparatus and method The present invention relates to a method and apparatus for thermal treatment techniques for semiconductor wafers, such as thermal oxidation treatment, diffusion treatment, CVD (Chemical Deposition) treatment, annealing treatment and the like.

According to one aspect of the present invention, there is provided a thermal treatment apparatus comprising a horizontally extending furnace tube for subjecting wafers to a thermal treatment, said furnace tube having an opening, a carrier extending in horizontal direction and having a portion adapted to have a plurality of wafer jigs placed thereon, moving means for moving said carrier from a first position outside the furnace tube to a second position inside the furnace tube and from the second position inside the furnace tube to the first position outside the furnace tube, control means, coupled to said moving means, for controlling movement of said carrier between said first and said second position in accordance with a plurality of predetermined modes.

According to a further aspect of the invention, there is provided a method of subjecting wafers to a thermal treatment in a furnace tube, comprising the steps of preparing a horizontally extending furnace tube having an opening, and a horizontally extending carrier having a portion adapted to have a plurality of wafer jigs placed thereon, placing the plurality of wafer jigs together with a plurality of wafers at said portion of the carrier, moving the carrier to a predetermined position in the furnace tube, locating the plurality of wafer jigs at the predetermined position, withdrawing the carrier from the predetermined position to another position which is close to the opening of the furnace tube, closing the opening of the furnace tube, conducting a thermal treatment in the furnace tube, advancing the carrier to the predetermined position in the furnace tube, lifting the plurality of wafer jigs with the carrier, re-locating the plurality of wafer jigs at the predetermined position, repeating said withdrawal step.

The invention will be further described by way of example with reference to the accompanying illustrative drawings, in which: Figure 1 is a perspective view of a thermal treatment apparatus for use in the present invention; Figure 2 is a perspective view of a soft landing loader for the apparatus of Fig. 1; Figure 3 is a perspective view of the wafer jig indicated in Fig. 2; Figures 4 to Figure 6(A), Figure 6(B) and Figure 6(C) further illustrate the soft landing loader; Figure 7(A) to Figure 7(G) illustrate the operation of a fork of the soft landing loader; Figure 8 is a sectional view of a fork of a soft landing loader in the thermal treatment apparatus particularly showing the fork being inserted into a process tube; Figure 9(A) to Figure 9(G) illustrate the operation of the thermal treatment apparatus;; Figure 10(A) to Figure 10(C) illustrate the positions of the fork of a soft landing loader in the operation of the apparatus; Figure 11 illustrates the operation of the fork when the soft landing loader is in each of three different modes; Figure 12 is a front view of a control panel for the soft landing loader; and Figure 13 to Figure 16 illustrate operation sequences of the soft landing loader of thermal treatment apparatus according to the present invention in the respective modes of Fig.

11.

Fig. 1 is a perspective view of a thermal treatment apparatus 100 according to the present invention. In the figure, a reference numeral 97 designates a thermal treatment furnace which is employed as, e.g., a diffusion furnace for the thermal diffusion treatment for a semiconductor wafer, a thermal oxidation furnace for forming a thermal oxidation film on a semiconductor wafer, a CVD furnace for forming a CVD film on a semiconductor wafer or an annealing furnace for annealing a semiconductor wafer. The thermal treatment furnace has three process tubes 102 disposed in the upper, intermediate and lower stages respectively. Aiso the thermal treatment furnace 97 has a control panel 97A and the like disposed on a side thereof for a control system for controlling the thermal treatment furnace, and a doping cabinet 98 disposed in the rear part thereof.

Moreover, a reference numeral 101 denotes a soft landing loader, and three soft landing loaders are disposed in the upper, intermediate and lower stages in correspondence with the three process tubes 102 of the thermal treatment furnace 97. A reference numeral 101A designates a control panel for controlling the soft landing loaders.

The thermal treatment technique using this apparatus will be described hereinunder through a detailed description of one of the soft landing loaders 101.

Fig. 2 is a perspective view illustrating, in detail, the soft landing loader 101 in the thermal treatment apparatus 100 according to the present invention. The soft landing loader 101 is disposed adjacent to the opening side of one of the process tubes 102, made of quartz, of the thermal treatment furnace 97, not shown in detail, and is adapted to be capable of loading as well as unloading wafers 104, forming the objects to be treated, mounted in alignment on a wafer jig 103 made of quartz, shown in Fig. 10, together with the wafer jig 1 03. The soft landing loader 101 has a base 105 and a rear wall 106 vertically disposed in the rear part of the base. The rear wall 106 has a pair of upper and lower guide rails 107 extending in the axial direction (referred to as "longitudinal direction", hereinafter) of the quartz process tube 102.The guide rails 107 are slidably fitted with upper and lower support plates 109, 110, respectively, integrally connected by means of a pair of guide rods 108 extending vertically, as shown in Fig. 4. A feed shaft 11 2 supported by the rear wall 106 so as to be parallel with the guide rails 107 fitted through a block 111 integrally formed with the lower support plate 110. As shown in Fig.

2, the feed shaft 11 2 has both ends rotatably supported by bearings 11 3 and has a pulley 114, secured to one end thereof, connected to an output pulley 11 6 of a longitudinal movement motor 11 5 through a belt 11 7 so that the feed shaft is rotated by the motor 11 5. In addition, the block 111 incorporates a mechanism for axially (longitudinally) moving the block in co-operation with the feed shaft 1 2. When the feed shaft is rotated by the mechanism, the block 111, and thus the upper and lower support plate 109, 110, can be integrally moved in the longitudinal direction in accordance with the sense of the feed shaft rotation.

A projection 11 9 of a substantially L-shaped movable plate 118 is fitted on each of the guide rods 108 provided between the upper and lower support plates 109, 110 so that the movable plate 11 8 can vertically move with respect to the support plates 109, 110.

Moreover, a block plate 1 20 projects from a substantially central portion of the rear surface of the movable plate 11 8 and engages the thread of a worm rod 121 vertically and rotatably supported between the support plates 109, 110 so that the movable plate 118 can be vertically moved with respect to the support plates 109, 110 by the rotation of the worm rod 121. The worm rod 121 has a pulley 122 provided integrally with the lower end thereof, and a belt 1 25 connects the pulley 122 to a pulley 124 of a motor 1 23 secured to the support plate 110, thereby driving the worm rod.

On the other hand, a sliding plate 127, capable of moving in the direction (referred to as "lateral direction", hereinafter) perpendicular to the longitudinal direction along steps 1 26 provided at the front and the rear respectively, is mounted on the horizontal part of the movable plate 11 8. The slicing plate 1 27 has a vertical member 1 28 integrally formed at one end of the upper surface thereof. The vertical member 1 28 is threaded with a lateral regulation bolt 1 30 rotatably supported by a fixed vertical member 1 29 which is vertically disposed at the left end of the movable plate 118 so as to face to the vertical member 1 28.

The bolt 1 30 is adapted, to move the sliding plate 1 27 laterally, thereby to regulate the position of the sliding plate 1 27 with respect to the movable plate 11 8. The bolt 1 30 has a knob 131 disposed at its end. Manually rotating the knob 131 permits the bolt 1 30 to revolve on its axis, thereby allowing the sliding plate 1 27 to move laterally on the movable plate 11 8.

On the sliding plate 127, a vertically swinging plate 1 32 adapted to support a fork, described hereinafter in detail, is supported by bearings 1 33 and a shaft (not shown) at one end 1 32a thereof. Moreover, an eccentric cam 1 34 in the form of a short cylinder is horizontally disposed at a position corresponding to a substantially central portion of the vertically swinging plate 1 32 and supported by bearings 1 35 so that the vertically swinging plate 1 32 can rotate in the vertical direction. In addition, the eccentric cam has a worm wheel 1 36 secured to one end thereof.

The worm wheel 1 36 is engaged with a rotating worm 1 38 of a swing motor 1 37 secured on the sliding plate 1 27 so that the eccentric cam 1 34 can be revolved on its axis by the motor 137.

A fork holder 1 39 having a substantial Vshaped section is secured to the vertically swinging plate 1 32 by means of a bolt 140, at an end portion thereof, and on the holder 139 a fork 141 is substantially horizontally supported in the longitudinal direction by means of two belts 142. The fork 141 is formed into a tubular shape using quartz material, and an upper end portion 141a thereof is formed by cutting away the upper part of the tube, so as to be able to mount a plurality of wafer jigs 103 in a row, as shown in Fig. 2.Accordingly, as shown in Fig. 5, since the central part of the vertically swinging plate 1 32 is supported by the circumferential surface of the eccentric cam 134, the end 141 a of the fork 141, together with the vertical swinging plate 1 32 and the fork holder 139, can be swung vertically when the eccentric cam 1 34 is rotated as shown by chain lines of the figure. Moreover, when the bolt 140 is loosened, the fork end 1 41 a can be swung in the horizontally lateral direction with respect to the vertically swinging plate 132.

Further, an inner cap 143 and an outer cap 144 can be set inside and outside the substantially central portion of the fork 141 respectively, as shown in Fig. 6(A), Fig. 6(B) and Fig. 6(C). These caps 143, 144 have outer casings made of quartz glass and the insides filled with quartz wool and are provided with handles 143a, 1 44a and air vents 143b, 1 44b respectively. The inner cap 143 is formed as a short cylinder and can be loaded in the fork 141, while the outer cap 144 is formed into a thick crescent-shaped disc having a semi-elliptical reentrant portion 1 44c and can be mounted on the upper part of the fork.When the fork 141 thus fitted with the inner and outer caps 143, 144 is entered into the process tube 102 made of quartz, as described hereinafter, these caps 143, 144 can close off the entry end of the quartz process tube 102.

The function of the soft landing loader having the above-mentioned arrangement will be described hereinunder.

Fig. 7 illustrates a process for setting the wafer jigs 103 in the quartz process tube 102. On the end 141a of the fork 141 prepared as shown in Fig. 7(A), a plurality of wafer jigs 103 are mounted as shown in Fig.

7(B). In this case, since the fork end is downwardly deformed by the weight of the wafer jigs, the vertical movement motor 1 23 is driven to rotate the worm rod 1 21 in order to move upwardly the movable plate 118, thereby to move upwardly the whole of the fork 141 as shown in Fig. 7(C). Moreover, the vertical swing motor 1 37 is driven to rotate the eccentric cam 134, thereby allowing the fork end 141a to swing upwardly as shown in Fig. 5. Consequently, the position of the fork end is corrected so as to be substantially horizontal as shown in Fig. 7 (D).Then, when the longitudinal movement motor 11 5 is driven to rotate the feed shaft 112, the block 111 actuates the support plates 109, 110 to advance towards the right of the figure, so that the fork 141 enters into the quartz process tube 102 and stops at a given position as shown by solid lines in Fig. 7(E). Hereupon, reversing the vertical movement motor 1 23 permits the whole of the fork 141 to move downwardly as shown by chain lines in Fig. 7(E), and the lower ends of the wafer jigs 103 are brought into contact with the inner bottom surface of the quartz process tube 102 at a given position of lowering. In this connection, a larger scale illustration of the position reached is shown in Fig. 8.Thereafter, when the vertical movement motor 1 37 is reversed in order to swing the fork end 141a downwardly, the downwardly moved end is released from supporting the wafer jigs 103 as shown in Fig. 7(F). Accordingly, when the longitudinal movement motor 11 5 is then reversed in order to allow the fork 141 to move towards the left of the figure and withdrawn from the quartz process tube 102 and at the same time, the vertical movement motor 1 23 is rotated so as to move the fork 141 upwardly, the fork is returned to its initial position as shown by solid lines or dash and two-dotted lines of the Fig. 7(G). According to the process described above, the wafer jigs 103 can be entered into the quartz process tube 102 without the loader contacting with the inside thereof and gently mounted inside the process tube.

Fig. 9 illustrates a process for unloading the wafer jigs from the quartz process tube, when their wafers have completed a thermal treatment. The fork 141 is advanced from the position of readiness shown in Fig. 9(A) into the quartz process tube 102 by operating the longitudinal movement motor 115, and the fork end 141a is advanced under the wafer jigs 103 as shown in Fig. 9(B). Then, the vertical movement motor 1 23 is operated in order to move the whole of the fork vertically, thereby allowing the fork end to scoop up the wafer jigs 103 as shown in Fig. 9(C). On doing this, the end 141a is downwardly deformed by the weight of the wafer jigs 1 03.

Therefore, operating the vertical swing motor 1 37 permits the fork end to be swung upwardly, so that the fork supports the wafer jigs with the end kept substantially horizontal as shown in Fig. 9(D). Thereafter, reversing the longitudinal movement motor 11 5 permits the fork to retreat out of the quartz process tube 102 as shown by solid lines of Fig. 9(E) and at substantially the same time, the vertical movement motor 1 23 is driven in order to move the whole of the fork downwardly as shown by chain lines of the figure, and moreover the vertical swing motor 1 37 is driven in order to swing the fork end 1 41 a downwardly to its initial state as shown in Fig. 9(F).

Accordingly, when the operator removes the wafer jigs 103 from the fork under this state, the fork is returned to its initial state as shown in Fig. 9(G). The wafer jigs 103 are thus also unloaded without the fork contacting the quartz process tube in the wafer jig unloading process.

Therefore, there is no possibility of generation of dust particles due to wear between the wafer jigs 103 and the inner surface of the quartz process tube 102, since the wafer jigs 103 are moved along the quartz process tube 102 without contacting with the inner surface thereof when the wafer jigs are loaded and unloaded in the above-mentioned processes.

Moreover, since the fork 141 can not only move vertically and longitudinally but also swing the end 141a vertically, even when the fork is deformed due to the weight of the wafer jigs, it can support them in a substantially horizontal state, so that there is little chance that the wafer jigs will fall from the fork. In this case, there is also the advantage that even when the fork is moved downwardly, the fork and the quartz process tube will not foul each other, because if the fork endis deformed downwardly, this is corrected upwardly.

An example of the use of this soft landing loader with the above-mentioned basic functions will be described hereinunder. First, in this thermal treatment apparatus, the relative positions of the fork with respect to the quartz process tube 102 are separately shown in Fig.

10(A), Fig. 10(B) and Fig. 10(C), and the respective positions are referred to below as Pl, P2 and P3: at P1, the fork 141 is completely withdrawn from the quartz process tube 102, at P2, the fork end 141a is positioned in a soaking part 1 02a of the quartz process tube 102, namely the wafer jigs are positioned within the soaking part 102a; and at P3, although having been withdrawn from the soaking part 1 02a of the quartz process tube 102, the fork end 141a is still within the quartz process tube 102 and at this time, the abovementioned inner and outer caps 143, 144 are at the end of the quartz process tube where they close off the entry opening.

After these positions, P1, P2 and P3, are set, by interactive means between the furnace control system and the loader control system sequential control is performed in modes such as shown in Fig. 11(A), Fig. 11(B) and Fig.

11(C), thereby to make it possible to effect control corresponding to various treatments.

Namely, MODE A and MODE B shown in Fig.

11 are employed when treatment temperatures are relatively high, e.g., in case of diffusion treatment, thermal oxidation treatment or CVD treatment for wafers. In MODE A, after the fork is moved to P2 in order to set the wafer jigs within the soaking part in a step S, shown in Fig. 11, the fork is retreated to P3 in a step S2. Then, with the quartz process tube closed by means of the inner and outer caps, a thermal treatment such as diffusion, thermal oxidation, CVD, annealing or the like is conducted. Since the fork end is near the end of the quartz process tube at this time, it is hardly affected by heat.Although in thermal treatments it may be possible that the quartz wafer jigs fuse with the quartz process tube due to the treatment heat and the contact positions (lower ends) thereof, and adhere to the inner surface of the tube, this is prevented by means of a step S3 in which the fork is operated according to a timer control.

In other words, by the operation of an interval timer, the fork advances to P2 from P3 at suitable intervals, and at P2, the fork end is upwardly swung and positioned there for a short period. Thereby, the wafer jigs are lifted during that period, so that they are separated from the inner surface of the quartz process tube to prevent them from fusing with the inner surface thereof. On completion of the operation, the fork returns to P3 again. The operation is repeated at suitable intervals during the treatment to make it possible to reliably prevent the fusing of the wafer jigs with the process tube.After the thermal treatment is completed, the fork end enters under the wafer jigs again in a step S4, and the wafer jigs are unloaded from the quartz process tube at a step 55. Accordingly, even in high-temperature treatments, it is possible to prevent the fusing of the wafer jigs as well as the thermal deformation of the fork, so that satisfactory thermal treatments can be completed.

In MODE B, as shown by steps Ss, S7 illustrated in Fig. 11, after the wafer jigs are entered into the quartz process tube the fork is retreated to P1, i.e., the fork is completely drawn out of the quartz process tube, and then a thermal treatment is conducted. On completion of the thermal treatment, the fork is inserted and withdrawn again in steps S8, S9 to make it possible to unload the wafer jigs from the quartz process tube. The MODE B is appropriate for thermal treatments at extremely high temperatures, and it is more effective if an automatic cap for the quartz process tube is used at the same time.

MODE C is appropriate for treatments at relatively low temperatures, such as annealing treatment. In the MODE C in a step S,O shown in Fig. 11, the fork is advance to P2 in order to enter the wafer jigs within the soaking part of the quartz process tube, and with this condition maintained, a thermal treatment is conducted. On completion of the thermal treatment, the wafer jigs are unloaded from the quartz process tube in a step S11. Since the treatment temperature is low, needless to say, there is no possibility of any thermal deformation of the fork.

It suffices that the above-mentioned modes are previously programmed and fed to a mi crocomputer so that a desired mode can be obtained by depressing a selection switch. In case of arranging the apparatus so as to be an all-purpose machine, the arrangement is such that the fork can be manually operated, e.g., it suffices to arrange the switch panel of the control panel 101A such as shown in Fig. 12.

In such an apparatus, an operation switch group 145 in the lower part of the panel for controlling the operation of the fork can be used in semiautomatic and manual modes. In the manual mode, the fork is operated only while a switch of the group is being depressed, while in the semiautomatic mode, once the switch is depressed the fork is automatically moved and stopped at the subsequent position. In addition, the above-mentioned modes A, B and C, are made available through selection of switches 1 46 corresponding to A, B and C respectively.

The function of each of switches of the control panel shown in Fig. 1 2 is as foilows.

Depressing the POWER switch permits all power sources of the soft landing loader to be turned ON. When MANUAL is turned ON, the manual mode is obtained, and each of switches 145 are made effective, so that while each is ON, the operation mode corresponding to that switch is actuated. When SEMI AUTO is turned ON, each of switches 145 are made effective such that when each is depressed (turned ON), the soft landing loader automatically moves to the subsequent position in the corresponding direction. When LOCAL is turned ON, the mode is changed into LOCAL MODE. When STOP is turned ON, the motion of the soft landing loader can be temporarily stopped.

Figs. 1 3 to 1 6 show the sequences of the soft landing loader respectively: Fig. 1 2 shows the sequence in LOCAL MODE: Fig. 14 shows the sequence in the MODE A shown in Fig. 11; Fig. 1 5 shows the sequence in the MODE B shown in Fig. 11; and Fig. 16 shows the sequence in the MODE C shown in Fig. 11.

The present invention is not limited to the above-mentioned preferred embodiment, and in practice devices for moving the fork longitudinally and vertically and for swinging the same vertically can take many forms.

As will be fully understood from the foregoing description, since in the thermal apparatus according to the present invention the wafer jigs can be lifted intermittently by putting the form in and out during a thermal treatment, it is possible to prevent the fusing of the wafer jigs with the process tube due to heat as well as to prevent the thermal deformation of the fork, thereby to make it possible to conduct thermal treatments very satisfactorily under high-temperature conditions. Moreover, in the apparatus described it is possible to prevent generation of dust particles by maintaining the inner surface of the process tube and the wafer jigs or the like out of contact with each other in loading and unloading of the wafer jigs, since the fork for transmitting the wafer jigs is adapted to be able to move at least vertically and longitudinally with respect to the thermal treatment furnace, and the wafer jigs can be moved vertically by swinging the fork end.

Claims (8)

1. A thermal treatment apparatus comprising: a horizontally extending furnace tube for subjecting wafers to thermal treatment, said furnace tube having an opening; a carrier extending in horizontal direction and having a portion adapted to have a plurality of wafer jigs thereon; moving means for moving said carrier from a first position outside the furnace tube to a second position inside the furnace tube and from the second position inside the furnace tube to the first position outside the furnace tube; control means, coupled to said moving means, for controlling movement of said carrier between said first and said second positions in accordance with a plurality of predetermined modes.

2. A thermal treatment apparatus according to claim 1, wherein in one of said modes said carrier is located inside of said furnace tube during thermal treatment, while in another of said modes, said carrier is located outside of said furnace tube during thermal treatment.

3. A thermal treatment apparatus according to claim 1 or claim 2, wherein said predetermined modes include different thermal treatments for the wafers.

4. A thermal treatment apparatus according to claim 3, wherein said different thermal treatments include treatments at different temperatures.

5. A thermal treatment apparatus according to claim 1, wherein said modes include one in which said carrier is intermittently passed into the furnace tube during the thermal treatment to lift the water jigs during said thermal treatment, whereby to prevent fusing of the wafer jigs during the thermal treatment.

6. A method of subjecting wafers to a thermal treatment in a furnace tube comprising the steps of: preparing a horizontally extending furnace tube having an opening, and a horizontally extending carrier having a portion adapted to have a plurality of wafer jigs placed thereon; placing the plurality of wafer jigs together with a plurality of wafers at said portion of the carrier; moving the carrier to a predetermined position in the furnace tube; locating the plurality of wafer jigs at the predetermined position; withdrawing the carrier from the predetermined position to another position which is close to the opening of the furnace tube; closing the opening of the furnace tube; conducting a thermal treatment in the furnace tube; advancing the carrier to the predetermined position in the furnace tube; lifting the plurality of wafer jigs with the carrier; ; re-locating the plurality of wafer jigs at the predetermined position; repeating said withdrawal step.

7. A method of subjecting wafers to a thermal treatment according to claim 6, wherein the sequence comprising the steps of advancing, lifting, re-locating and withdrawing are repeated a plurality of times.

8. A method of subjecting wafers to a thermal treatment substantially as described herein.