KR20070040797A - Epitaxial reactor with susceptor controlled positioning - Google Patents

Abstract

The present invention relates to a system for controlling the positioning operation of the susceptor 2 rotating in the reaction chamber 3 of the stacked reactor. The control is carried out on the basis of the other line of the laser beam transmitted by the source 15 when reflected by the pin 8 arranged on the susceptor 2.

Susceptors, positioning, stacked reactors, CVD, laser beams, fins, protruding elements.

Description

Stacked Reactor with Susceptor Under Position Control {EPITAXIAL REACTOR WITH SUSCEPTOR CONTROLLED POSITIONING}

The present invention relates to an epitaxial reactor used for the production of a substrate by chemical vapor deposition (CVD); It also includes a method of controlling the susceptor position of the reactor.

In particular, in the field of reactors used herein, used in the microelectronics industry, the term "susceptor" is used in substrate (also commonly referred to as 'slice' or 'wafer' terms during an epitaxial growth process) ) Refers to a heated support.

The susceptor is typically placed inside a reaction chamber made of quartz, while the substrate is of a substrate type (generally in the form of a disc), except for small clearances used to position the substrate. It is located on the top surface, which is an inner individual seating portion.

As is known, lamination growth is the result of a chemical reaction between two or more gases, and the reaction product is a pure material deposited on the substrate surface to form a crystal structure. Since the reaction takes place at very high temperatures, it is necessary to heat the substrate via susceptor means.

Rotary susceptors are generally used to improve the uniformity of the deposition layer. In this rotation scheme, the radial temperature and ratio of the growth profile are averaged along the azimuth coordinate, making it more uniform.

The susceptor has a susceptor having a property for only one substrate or a plurality of substrates, and the latter is used to improve the productivity of the reactor; In addition, in order to further improve productivity, the loading / unloading operation of the substrate is performed by a known method using a robotic arm.

In this case, the susceptor rotates during the process so that the system needs to control the positioning angle to move to the pre-arranged position to allow loading / unloading operation; This angular movement is controlled electronically with the angle of the robotic arm.

In view of the nature of the CVD process, systems for angular positioning of susceptors should not contaminate the reaction chamber by introducing metal particles or releasing other materials, for example due to sliding components.

Another fundamental requirement is that the positioning system must be capable of operating at high temperatures (about 1000 ° C. or more) that will appear in the stack reaction chamber.

In view of these stringent conditions, prior art systems for controlling the position of the susceptor are preferably of the optical type.

One of the prior art systems provided a laser beam directed from the outside of the reaction chamber toward the edge of the susceptor disk and provided with a notch for this purpose. When the susceptor disk reaches the bottom of the laser beam as a result of the susceptor's rotation, its presence is detected and can be repositioned to the action required for the purpose.

The various steps in the adjustment process are managed electronically by a control unit which is known per se.

The control system of the type described above is satisfactory in terms of angular positioning. However, the system is limited in terms of the mechanical strength of the susceptor.

To understand this fact, it should be borne in mind that the susceptor is subjected to high thermal strain due to the heating cycle applied to the susceptor. It can be easily deduced that the presence of notches with repeated expansion and contraction cause all the undesirable consequences raised here, causing splitting or cracking in the susceptor.

The problem solved by the present invention is to produce a multilayer reactor in which the angular position of the susceptor is free from the above-mentioned defects.

The idea to solve this problem is to use an element that protrudes from the surface of the susceptor and can reflect the laser beam or other electromagnetic radiation used, instead of a notch or other likeness that degrades the mechanical properties of the susceptor structure. To produce a susceptor.

A protruding element consisting of a pin with a large area of head allows detection of the result of the change in the path of the incident ray as opposed to when radiation is reflected off the surface of the susceptor. The altered angular position is then well adjusted by the method of making the present invention.

Protruding elements that reflect the line of incidence are located on the surface of the susceptor and do not damage its structure, thereby not suscepting the susceptor.

The projecting element is also preferably made of the same material as the susceptor so as to have the same properties of strength and reflectivity in the hot gases in the reaction chamber.

DETAILED DESCRIPTION OF THE INVENTION Characteristic details of the present invention will be clearly understood through the embodiments described below as non-limiting examples with reference to the accompanying drawings.

1 is a view showing the susceptor according to the present invention from above.

FIG. 2 is a cross-sectional view taken along the plane indicated by line B-B in FIG.

3 is a cross-sectional view of the stacked reactor in which the susceptor is located in FIG.

4 is a view schematically showing the reflection of the laser line of the reactor in the previous drawing.

This will be described with reference to FIG. 3. FIG. 3 shows a stacked reactor generally indicated by the numeral '1' which includes a disc shaped susceptor 2 housed in a reaction chamber 3 of parallel hexahedral form.

The susceptor is preferably made of graphite and has a series of circular seats 5 (in this case 8) for receiving the substrate. The susceptor rotates about a vertical axis X which is known per se and is driven by an electronically controlled motor not shown in the figure. In effect, the structure is such that the electric motor is coupled to a pulse generator (encoder) to divide the 360 ° rotation about the axis X into a predetermined interval of number (eg 200 × 10 ³ ).

The reactor 1 also includes a robotic arm that loads the substrate into the susceptor (and unloads the substrate from the susceptor). The arm is of a well-known type, for example as described in European patent application 99962242 and is not shown in the drawings.

The reaction chamber 3 has a wall made of quartz, and both ends are open so that gas passes through as indicated in FIG.

On the edge of the susceptor, a pin 8 having a flat, large area base 8a and a head 8b is fitted, the base 8a and the head 8b as described more clearly below. It is made approximately bobbin-shape so that it can reflect the laser line and be properly installed on the susceptor.

According to this example of the present invention, the pin base 8a is seated in the hollow portion 10 shown enlarged in FIG. The hollow part 10 makes the base 8a of the pin more stable and generally shallower at the surface.

In one position on the pin 8, outside the reaction chamber 3, the module 15 is arranged with a laser line transmitter and receiver, as is known per se. The module is supported by an actuator 18 of pneumatic, electromechanical or other type, such that the operating position of the laser line is directed downward towards the susceptor and the ratio of operating in a direction away from the reaction chamber 3. -To be moved between the operating position.

Preferably, on the upper wall of the reaction chamber 3 through which the laser line passes, the surface of the quartz is flat, so that the nonuniformity in the upper wall is eliminated and the optical window 20 can reduce the precision of the operation. It is installed so that there is no diffusion phenomenon of the laser line.

In the operating position, the module 15 delivers the laser beam to the surface of the susceptor 2 at a predetermined angle of incidence, which reflects the beam towards the detector in the module.

As a result of the rotation of the susceptor 2, if the pin 8 passes under the module 15, the beam transmitted by the module 15 is projected relative to the surface of the susceptor 2. In a manner reflected by the flat head 8b. 4 is a diagram schematically showing another line of the same incidence line when reflected by the susceptor 2 and by the head 8b of the pin.

The difference in the beam line is detected by the module 15 which signals the presence of a pin to an electronic control unit (CPU) that controls the adjustment of the susceptor. This takes place on the basis of a program previously input to the control device in the following operation steps in this embodiment.

As a first step, the system is initialized; The susceptor (2) is rotated clockwise at a low speed (three revolutions per minute), the laser beam is projected onto the surface and the value of the beam's track is obtained for several seconds; The values are averaged to determine the measured value as the average distance of the susceptor surface from the laser module 15.

If a distance value smaller by a predetermined amount relative to the average distance is obtained, this means that the laser beam is shining on the fin 8, and then the adjustment is carried out in the following manner.

a) The speed decreases slowly with the speed decreasing slope until the susceptor 2 stops at a braking angle of approximately 100 ° / 120 °.

b) The susceptor 2 previously rotated at a low speed (1 revolution / minute) counterclockwise in the direction opposite to the direction.

c) As a result of the reverse rotation, when the beam illuminates the pin 8 once again, the angular position SZ1 of the susceptor is based on a signal supplied by the pulse generator correlating with the motor that rotates the susceptor. Save it.

d) The susceptor slowly slows down until it stops quickly (breaking space approximately 11 ° / 13 °).

e) Subsequently, with the precise movement of the susceptor (speed 0.1 to 0.05 revolutions per minute), the pin 8 goes back under the laser beam and this angle position is 0 ° which is used to initialize the pulse generator relative to the motor. It becomes the standard position.

At this point, after the laser module 15 is raised to the non-operational position, the robotic arm unloads the substrate from the susceptor and loads the substrate into the susceptor.

This practice allows the rotation of the susceptor 2 to be precisely controlled based on the signal supplied by the pulse generator correlated with the actuating motor, so that the seating portion 5 is positioned in a position necessary for loading / unloading of the substrate by the robotic arm. Let go.

From the foregoing description, it will be appreciated how the control of the angular position implemented according to the invention overcomes the limitations pointed out in the conventional reactor.

The present application eliminates the need for the presence of a pin on the disk of the susceptor to notch the edge of the susceptor as described at the outset. As a result of this, the risk of cracks or brakes being formed or propagated from the outset is eliminated from the outset due to the stress caused by the thermal cycle the susceptor receives.

In addition, the hollow portion 10 which provides the seating portion for the pin has the effect of making the pin more stable, but does not need to be strictly and may also be omitted. In this embodiment, it is only necessary to widen the base 8a in order to install the pin stably.

And since the hollow part 10 is shallow, the structural strength of the susceptor is not affected.

In general, the body of the fin is preferably narrowed without affecting the hydrodynamics of the reactor and without interference of the reactant gas (or as little interference as possible) to reduce friction between the gas and the fin.

To achieve these effects, one may produce a pin with a wide base and a narrow head, or integrate the pin directly into the susceptor as a protrusion of the susceptor.

Of course, the invention of the present application may make other modifications to the embodiments of the invention described above.

First, the basic principle described above is also effective for susceptors made of other materials in addition to graphite, which is problematic in cracks and brakes caused by thermal stress.

Other changes may also be made to the beams that illuminate the susceptor and how to transmit and detect them. For example, the beam is virtually possible in addition to the laser beam.

Finally, the present invention is not limited to only controlling the angular position of the susceptor, but may be applied to linear control. That is to say, in general, the present invention is applicable to a reactor for chemical vapor deposition in the vapor phase where there is a susceptor or other similar motion component in which the positioning operation is controlled.

Claims (17)

Chemical vapor deposition comprising a reaction chamber 3, a susceptor 2 moving in the reaction chamber, means 15 for transmitting electromagnetic radiation towards the susceptor, and means 15 for detecting the radiation. As reactor: a reactor, characterized in that at least one projecting reference element (8) is provided on the susceptor, capable of reflecting radiation towards the means for detecting radiation. The method of claim 1, Reactor, means for transmitting electromagnetic radiation and means for detecting radiation are arranged outside of the reaction chamber (3). The method of claim 2, The electromagnetic radiation is luminous and the walls of the reaction chamber (3) pass the radiation. The method of claim 3, The reflected radiation comprises a laser beam. The method according to any one of claims 1 to 4, The reflective element comprises a pin (8) projecting against the surface of the susceptor (2). The method of claim 5, The pin comprises a flat head (8b). The method of claim 6, The pin comprises a base (8a) for seating the pin on the susceptor. The method of claim 7, wherein The base (8a) of the fin (8) is seated in a hollow (10) formed on the surface of the susceptor (2). The method according to any one of claims 1 to 8, The reflective element (8) is made of the same material as the susceptor. The method of claim 9, And the material is graphite-based. The method according to any one of claims 1 to 10, The susceptor (2) rotates about an axis (X) and its rotational movement is caused by electronically controlled initialization operating means. The method according to any one of claims 1 to 11, Means for delivering electromagnetic radiation towards the susceptor and means for detecting radiation reflected by the susceptor are incorporated into the module 15, the module having a ratio in which the module moves in a direction away from the reaction chamber 3. A reactor movable between the operating position and the operating position facing towards the susceptor 2. The method according to any one of claims 1 to 12, The reactor comprises a window (20) in the region of the reaction chamber (3) through which electromagnetic radiation passes, which can avoid the spread of radiation. 14. A reactor supporting the substrate according to any one of claims 1 to 13, which provides a seat for the base 8a of the projecting element 8 capable of reflecting the electromagnetic radiation. Susceptor, characterized in that it comprises a hollow portion (10) on. 14. A susceptor according to any one of claims 1 to 13, comprising a protrusion on a surface supporting a substrate capable of reflecting electromagnetic radiation. A method of controlling the position of the susceptor 2 of a chemical vapor deposition reactor, the method comprising: Arranging an element 8 protruding from the surface of the susceptor, capable of reflecting electromagnetic radiation; Projecting a beam of electromagnetic radiation on the susceptor 2 in operation; Detecting the difference in the line of the beam when the beam is reflected by the projecting element (8); Inputting a position of susceptor 2 in accordance with detection of a differential path of the beam; And Causing the movement of the susceptor (2) based on the positional input. The method of claim 16, The method for inputting the position of the susceptor, Operating the susceptor 2 for a predetermined time period to average the distance values moved by the incident beam; Stopping the susceptor (2) in a predetermined space when the distance is changed by the reflective element (8) passing below the beam; Operating the susceptor 2 in the reverse direction to return the reflective element 8 to a position below the beam; -Initializing the susceptor 2 using this position as a reference.

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