Substrate treatment device

Abstract

A heating apparatus includes a plurality of zone heating apparatuses and a control apparatus. The reference variable of the control apparatus is a susceptor temperature. The controlled variable of the control apparatus is an actual temperature of the susceptor measured by a temperature sensor and the manipulated variable of the control apparatus is the total heating power fed into the heating apparatus. A heating power distributor receives the total heating power as an input variable and provides a zone heating power for each of the zone heating apparatuses as output variables. The sum of the zone heating powers corresponds to the total heating power and the zone heating powers have a specified ratio with respect to each other. In order to specify a robust control loop, the specified ratios are defined by distribution parameters, wherein at least one distribution parameter is a quotient of two zone heating powers.

Claims

1. A device for treating substrates, comprising a susceptor (7) which is disposed in a process chamber (6) and has a first side (7) that faces towards the process chamber (6) for accommodating at least one substrate (15) and a second side (7) that faces away therefrom and is heated by a heating apparatus having a plurality of zone heating apparatuses, and comprising a control apparatus, a reference variable of which is a susceptor temperature (T.sub.S), a control variable of which is an actual temperature of the susceptor (7) measured by a temperature sensor (10), and a manipulated variable of which is a total heating power (P.sub.tot) fed into the heating apparatus, comprising a heating power distributor (12) which receives only the total heating power (P.sub.tot) as an input variable and which provides a zone heating power (P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5) for each of the zone heating apparatuses (1, 2, 3, 4, 5) as output variables, wherein a sum of the zone heating powers (P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5) corresponds to the total heating power (P.sub.tot), wherein the zone heating powers (P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5) have specified ratios with respect to one another, wherein the specified ratios are specified by pre-selected distribution parameters (A, B, C, D), wherein the susceptor (7) has a circular disk shape, wherein a plurality of substrate holders (8) is disposed annularly about a center of the susceptor (7), each of the substrate holders (8) having a rotational axis and being configured to rotate about said rotational axis, wherein the zone heating apparatuses (1, 2, 3, 4, 5) are disposed annularly about the center of the susceptor (7) in such a manner that a middle one of the zone heating apparatuses (1) is disposed below respective centers of the substrate holders (8), a radially inner one of the zone heating apparatuses (3) is disposed in a region below an inner edge of the annular arrangement of the substrate holders (8), and a radially outer one of the zone heating apparatuses (2) is disposed in a region below an outer edge of the annular arrangement of the substrate holders (8), wherein a first one of the pre-selected distribution parameters (A, C) (i) is a quotient of the zone heating power fed into the radially outer zone heating apparatus (2) and the zone heating power fed into the radially inner zone heating apparatus (3), and (ii) controls a temperature of respective circumferential edge zones of the substrate holders (8), wherein the radially outer zone heating apparatus (2) is radially non-adjacent to the radially inner zone heating apparatus (3), and wherein a second one of the pre-selected distribution parameters (B) (i) specifies a ratio of the zone heating power (P.sub.1) fed into the middle zone heating apparatus (1) to the total heating power (P.sub.tot), and (ii) controls a temperature of respective central zones of the substrate holders (8).

2. The device according to claim 1, further comprising at least one further pair of zone heating apparatuses (4, 5), in which the zone heating powers (P.sub.4, P.sub.5) fed into the further pair of zone heating apparatuses (4, 5) have a specified ratio (C) with respect to one another.

3. The device according to claim 1, wherein the zone heating apparatuses (1, 2, 3, 4, 5) are high-frequency coils for outputting a high-frequency alternating field, which induce eddy currents in the susceptor (7).

4. A method for treating substrates, in which at least one substrate (15) is disposed on a first side (7) of a susceptor (7) which is disposed in a process chamber (6) and the second side (7) of which facing away from the first side (7) is heated by a heating apparatus having at least three zone heating apparatuses (1, 2, 3, 4, 5) annularly disposed about a center of the susceptor (7), wherein a total heating power (P.sub.tot) fed into the heating apparatus is controlled by a controller (11), a reference variable of which is a susceptor temperature (T.sub.S), a control variable of which is an actual temperature of the susceptor (7) measured by a temperature sensor (10), and a manipulated variable of which is only the total heating power (P.sub.tot), wherein a heating power distributor (12) feeds a zone heating power (P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5) into each of the zone heating apparatuses (1-5), a sum of which is the total heating power (P.sub.tot), and wherein the distribution of the total heating power (P.sub.tot) among the individual zone heating powers (P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5) is carried out according to pre-selected distribution parameters (A, B, C, D), wherein on the first side (7) of the susceptor (7), a plurality of substrate holders (8) is disposed annularly about the center of the susceptor (7), each of the substrate holders (8) having a rotational axis and being configured to rotate about said rotational axis, wherein a middle one of the zone heating apparatuses (1) is disposed below the respective centers of the substrate holders (8), a radially inner one of the zone heating apparatuses (3) is disposed in a region below an inner edge of the annular arrangement of the substrate holders (8), and a radially outer one of the zone heating apparatuses (2) is disposed in a region below an outer edge of the annular arrangement of the substrate holders (8), wherein a first one of the pre-selected distribution parameters (A, C) (i) is a quotient of the zone heating power fed into the radially outer zone heating apparatus (2) and the zone heating power fed into the radially inner zone heating apparatus (3), and (ii) controls a temperature of respective circumferential edge zones of the substrate holders (8), wherein the radially outer zone heating apparatus (2) is radially non-adjacent to the radially inner zone heating apparatus (3), and wherein a further one of the pre-selected distribution parameters (B) (i) specifies a ratio of the zone heating power (P.sub.1) fed into the middle zone heating apparatus (1) to the total heating power (P.sub.tot), and (ii) controls a temperature of respective central zones of the substrate holders (8).

5. The method according to claim 4, further comprising at least one further pair of zone heating apparatuses (4, 5), wherein the zone heating powers (P.sub.4, P.sub.5) fed into the at least one further pair of zone heating apparatuses (4, 5) have a specified ratio (C) with respect to one another.

6. The method according to claim 4, wherein the pre-selected distribution parameters (A, B, C, D) are adapted to a total gas pressure set in the process chamber (6).

7. The method according to claim 4, wherein the pre-selected distribution parameters (A, B, C, D) are adapted to a maximum process temperature.

8. The method according to claim 4, wherein temperature ramps are implemented with the pre-selected distribution parameters (A, B, C, D) being kept at a fixed value.

9. The method according to claim 4, wherein the pre-selected distribution parameters (A, B, C, D) are determined through simulation calculations.

10. The method according to claim 4, wherein the pre-selected distribution parameters (A, B, C, D) are determined through measurements in preliminary tests.

11. The method according claim 4, wherein the pre-selected distribution parameters (A, B, C, D) are determined through simulation calculations and through measurements in preliminary tests.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are explained below with reference to the accompanying drawings. In the figures:

(2) FIG. 1 shows a top view of a circular-disk-shaped susceptor on which six substrate holders 8 are disposed, each of which is fitted with a substrate 15; the zone heating apparatuses 1, 2, 3 disposed below the susceptor 7 and extending annularly about the center Z of the susceptor 7 are illustrated in dashed lines;

(3) FIG. 2 shows a section according to the line II-II;

(4) FIG. 3 shows a block diagram of a control apparatus of the first exemplary embodiment;

(5) FIG. 4 shows an illustration similar to FIG. 2 of a second exemplary embodiment;

(6) FIG. 5 shows the block diagram of a control apparatus of the second exemplary embodiment;

(7) FIG. 6 shows a schematic illustration of the surface temperature occurring over the diameter of a substrate holder 8 at different distribution parameters B.

DETAILED DESCRIPTION

(8) The exemplary embodiment concerns a MOCVD reactor. In a non-illustrated reactor housing, which is gas-tight with respect to the outside, a susceptor 7 is located which has the shape of a circular disk and is rotationally driven about its axis Z. The center of the susceptor is situated in a gas inlet zone in which process gases are fed into the process chamber 6 through a gas inlet member 14. In a growth zone extending annularly about the gas inlet zone there are altogether six substrate holders 8 in the exemplary embodiment. The substrate holders lie in pockets 9 of the top side 7 of the susceptor 7. Means are provided by means of which the substrate holders 8 can be rotationally driven about their rotation axis 16. For this purpose, the circular-disk-shaped substrate holders 8 preferably lie on a gas cushion formed by a carrier gas that is fed from below into the pockets 9. By means of the carrier gas, a rotational movement can be imposed on the substrate holders 8. On each of the substrate holders 8 there is a substrate 15 to be coated. A process chamber ceiling 13, which can be cooled, is located above the process chamber 6. The gas inlet member 14 extends out of the center of the process chamber ceiling 13 towards the susceptor 7 and has a plurality of gas outlet openings through which, for example, gases with elements of the main groups III and V can be introduced into the process chamber 6. These process gases, which are introduced into the process chamber together with a carrier gas, for example hydrogen or nitrogen, degrade in the gas phase but also on the surface of the substrate 15, wherein a III-V-layer is deposited on the substrates 15. The carrier gas and the reaction products are discharged from the process chamber 6 by means of a vacuum pump, which is not illustrated.

(9) Below the susceptor 7, thus below the bottom side 7 of the susceptor 7, there is a plurality of zone heating apparatuses disposed annularly about the center Z. In the exemplary embodiment illustrated in the FIGS. 1 to 3, three zone heating apparatuses 1, 2, 3 are provided, and five zone heating apparatuses 1, 2, 3, 4 and 5 are provided in the exemplary embodiment illustrated in the FIGS. 4 and 5.

(10) The zone heating apparatuses can be resistance heaters or induction heaters. However, the heating apparatuses 1 to 5 are preferably induction coils which are disposed about the center Z in the manner of a spiral winding or concentric winding. All zone heating apparatuses 1 to 5 are disposed in one plane, wherein adjacent zone heating apparatuses 1 to 5 are situated next to each other as close as possible.

(11) Provided is a central zone heating apparatus 1 which extends annularly below the centers 16 of the substrate holder 8. In the region of this zone heating apparatus 1, the temperature of the susceptor 7 is also measured using a temperature measuring apparatus 10. In the exemplary embodiment, the temperature measuring apparatus 10 is illustrated as a thermocouple which is located at the bottom side 7 of the susceptor 7. The susceptor temperature can also be measured pyrometrically and in particular by means of a light pipe. A plurality of temperature measuring apparatuses 10 can be provided, which measure the temperature of the susceptor 7 at different radial positions or at different circumferential positions. If the susceptor temperature is measured at different circumferential positions, the measurement is preferably performed at the same radial spacing so that temperature averaging can be carried out. Preferably, the apparatus has only one temperature measuring apparatus 10 and/or the susceptor temperature is measured at only one radial position, but optionally by means of a plurality of individual temperature measuring apparatuses. The measurement is preferably carried out on the circular arc line on which the centers 16 of the substrate holders 8 are located.

(12) In the exemplary embodiment illustrated in the FIGS. 1 to 3, there is a radially inner zone heating apparatus 3 extending below the radially inner periphery of the growth zone, in addition to the central zone heating apparatus. The zone heating apparatus 3 extends substantially below the growth zone, thus below the substrate holder 8; however, an edge portion thereof extends also below the inlet zone, thus a zone that is not taken by a substrate holder 8.

(13) Radially outside of the middle zone heating apparatus 1 there is a radially outer zone heating apparatus 2, which likewise is located substantially below the growth zone, i.e., below the region of the susceptor side 7 taken by the substrate holders 8. However, here too, a portion of the zone heating apparatus 2 extends outside of the growth zone, thus outside of the region that is taken by the substrate holders 8.

(14) In the exemplary embodiment illustrated in the FIGS. 4 and 5, there is another zone heating apparatus 4 situated between the radially outer zone heating apparatus 2 and the central zone heating apparatus 1. Another zone heating apparatus 5 is situated between the middle zone heating apparatus 1 and the radially inner zone heating apparatus 3.

(15) The two outer zone heating apparatuses 2, 3 form in each case a pair. Likewise, the zone heating apparatuses 4 and 5 disposed between the outer zone heating apparatuses 2 and 3 and the middle zone heating apparatus 1 form a pair.

(16) FIG. 3 shows a control apparatus by means of which the zone heating apparatuses 1, 2, 3 are supplied with heating power. The reference variable is a specified substrate temperature T.sub.S. The temperature measured by the temperature measuring apparatus 10 is to be adjusted to this reference variable. For this purpose, the controller 11 outputs a total heating power P.sub.tot to a heating power distributor 12.

(17) The controller can be a PID controller. In the heating power distributor, the total heating power P.sub.tot is distributed as zone heating power P.sub.1, P.sub.2, P.sub.3 among the individual zone heating apparatuses 1, 2, 3. For this purpose, distributor parameters A, B are used which are found through preliminary tests or simulation calculations. The distribution parameters are substantially freely selectable and are different for different process conditions such as, for example, different total pressures or gas compositions. They are substantially a function of the specific thermal conductivity of the carrier gas used and of the geometry adjacent to the inner and outer edges of the susceptor. A first distribution parameter A corresponds to the quotient of the powers fed into the outer zone heating apparatuses 2, 3. Thus, it corresponds to a loss ratio of the inner to the outer surface.

(18) $A=\frac{P_2}{P_3}$

(19) A second distribution parameter B determines the portion of the total power that is fed into the middle zone heating apparatus 1.

(20) $B=\frac{P_1}{P_{\mathrm{tot}}}$

(21) With the distribution parameter A, the effect of the heating apparatus on the edge region of the substrate holder 8, thus on the edge of the substrate 15 resting thereon can be influenced. With the distribution parameter B, the power fed into the center of the rotating substrate is leveled. Thus, the center temperature of the substrate 15 can be increased by increasing the distribution parameter B and can be decreased by decreasing the distribution parameter B, respectively.

(22) FIG. 6 shows three temperature curves a, b, c which illustrate the surface temperature of substrate holder 8 that is heated from below. Curve a shows an energy supply with the distribution parameter B having a low value. It is apparent that the surface temperature in the middle of the substrate holder 8 is lower than at the edge.

(23) Curve b shows the temperature progression over the diameter of a substrate holder 8 with the distribution parameter B being increased. Since the total heating power P.sub.tot remains constant, less power is fed into the edge regions, i.e., in the peripheral zone heating apparatus 2, 3, than was the case for curve a. Accordingly, the difference between edge temperature and center temperature has decreased.

(24) Curve c shows how the surface temperature in the center of the substrate holder 8 can be further increased if the distribution parameter B is increased. Since here too, the total power P.sub.tot is kept constant, the power P.sub.2, P.sub.3 fed into the peripheral zone heating apparatuses 2 and 3 has decreased.

(25) Here, the distribution parameter A is kept constant.

(26) In the exemplary embodiment illustrated in the FIGS. 4 and 5, not only the two peripheral zone heating apparatuses 2 and 3 are coupled via a distribution parameter so as to form a pair. The intermediate zone heating apparatuses 4, 5 are also coupled via the distribution parameter C.

(27) $C=\frac{P_4}{P_5}$

(28) According to the invention, in each case two zone heating apparatus pairs are coupled to each other in terms of power, wherein this concerns zone heating apparatuses which are disposed symmetrically with respect to a middle zone heating apparatus 1.

(29) With the distribution parameter D, the power which is fed into the pair of zone heating apparatuses can be set as a percentage or, respectively, the power which is fed into one of the two zone heating apparatuses 3 can be set.

(30) $D=\frac{P_3}{P_{\mathrm{tot}}}$

(31) In an alternative, it is also conceivable to couple, via the fourth parameter, the two pairs of the zone heating apparatuses, thus the zone heating apparatuses 2 and 3, to the zone heating apparatuses 4 and 5.

(32) The susceptor 7 does not necessarily have to have a circular disk shape. It can also be formed from a body that has a flat surface onto which the substrates 15 to be coated can be placed. A central extension, for example in the form of a pin, can protrude from the back side of the susceptor and extend into the coils so that the coupling to the RF field is improved.

(33) Coupling the individual coils can also be carried out in a different way; for example, it is conceivable that directly adjacent coils are coupled to one another.

(34) The above embodiments serve for illustrating the inventions which are covered overall by the patent application and which improve the prior art in each case independently at least by the following feature combinations, namely:

(35) A device, which is characterized by a heating power distributor 12 which receives only the manipulated variable P.sub.tot as an input variable and which provides a zone heating power P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5 for each of the zone heating apparatuses 1, 2, 3, 4, 5 as output variables, wherein the sum of the values of the zone heating powers P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5 corresponds to the manipulated variable P.sub.tot and the values of the zone heating powers P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5 have a fixed ratio with respect to one another, characterized in that the specified ratios can be changed by preselectable distribution parameters A, B, C, D.

(36) A device, which is characterized in that at least one distribution parameter A, C is a quotient of two values of zone heating powers P.sub.1, P.sub.2; P.sub.4, P.sub.5.

(37) A device, which is characterized in that the susceptor 7 has a circular disk shape, wherein a plurality of substrate holders 8 is disposed annularly about the center of the susceptor 7, wherein the zone heating apparatuses 1, 2, 3, 4, 5 are disposed annularly about the center of the susceptor 7 in such a manner that a central zone heating apparatus 1 is disposed below the center of the substrate holders 8, a radially inner zone heating apparatus 3 is disposed in the region below the inner edge of the annular arrangement of the substrate holders 8, and a radially outer zone heating apparatus 2 is disposed in the region below the outer edge of the annular arrangement of the substrate holders 8.

(38) A device, which is characterized in that the zone heating powers P.sub.1, P.sub.2, P.sub.3 fed into the radially inner zone heating apparatus 3 have a fixed ratio A with respect to one another.

(39) A device, which is characterized by at least one further pair of zone heating apparatuses 4, 5, in which the zone heating powers P.sub.4, P.sub.5 fed into the associated zone heating apparatuses 4, 5 have a fixed ratio C with respect to one another.

(40) A device, which is characterized in that the substrate holders 8 can be rotationally driven about their respective center axis.

(41) A device, which is characterized in that the zone heating apparatuses 1, 2, 3, 4, 5 are high-frequency coils for outputting a high-frequency alternating field, which induce eddy currents in the susceptor 7.

(42) A method, which is characterized in that the manipulated variable is divided by a heating power distributor 12 into a plurality of zone heating powers P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5, each of which is fed into an associated zone heating apparatus 1, 2, 3, 4, 5, wherein the sum of the zone heating powers P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5 is the manipulated variable P.sub.tot output by the control apparatus to the heating power distributor 12, and wherein the values of the zone heating powers P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5 have a specified, freely selectable fixed ratio with respect to one another.

(43) A method, which is characterized in that the distribution of the total heating power P.sub.tot among the individual zone heating powers P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5 is carried out according to preselectable distribution parameters A, B, C, D.

(44) A method, which is characterized in that the distribution parameters A, B, C, D are adapted to the type of gas fed into the process chamber.

(45) A method, which is characterized in that the distribution parameters A, B, C, D are adapted to the total gas pressure set in the process chamber.

(46) A method, which is characterized in that the distribution parameters A, B, C, D are adapted to a maximum process temperature.

(47) A method, which is characterized in that temperature ramps are implemented with the distribution parameters A, B, C, D being kept at a fixed value.

(48) A method, which is characterized in that the distribution parameters A, B, C, D are determined through simulation calculations and/or through measurements in preliminary tests.

(49) All features disclosed are (in themselves) pertinent to the invention. The disclosure content of the associated/accompanying priority documents (copy of the prior application) is also hereby included in full, including for the purpose of incorporating features of these documents in claims of the present application. The subsidiary claims in their optional subordinated formulation characterize independent inventive refinement of the prior art, in particular to undertake division applications based on these claims.

REFERENCE LIST

(50) 1 zone heating apparatus 2 zone heating apparatus 3 zone heating apparatus 4 zone heating apparatus 5 zone heating apparatus 6 process chamber 7 susceptor 7 top side 7 bottom side 8 substrate holder 9 pocket 10 temperature measuring apparatus 11 controller 12 heating power distributor 13 process chamber ceiling 14 gas inlet 15 substrate 16 centers A distribution parameter B distribution parameter C distribution parameter D distribution parameter P.sub.1 zone heating power P.sub.2 zone heating power P.sub.3 zone heating power P.sub.4 zone heating power P.sub.5 zone heating power P.sub.tot heating power T.sub.S susceptor temperature Z center