JP2002353158A - Heat treatment device for substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which can obtain necessary temperature increase speed, without producing an offset when raising the temperature at a fixed rate by heating a substrate, and can control so as to equalize the temperatures in each heating zone divided into a plurality of parts. SOLUTION: A temperature control means controls a heating means based on deviations between the temperatures of a substrate to be measured by a temperature-measuring means and the temperatures of the preset temperature increase/decrease changes, with the temperature control means has a control part structured, so that a pole of an open-loop transfer function has 0, 0; and specifically, the temperature control means has the control part, in which double integration circuits are connected in parallel to a PID controller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of carrying a substrate such as a semiconductor wafer, a glass substrate for a liquid display device, a glass substrate for a photomask, and a substrate for an optical disk one by one into a heat treatment furnace and heating the substrate by light irradiation or the like. The present invention relates to an apparatus for heat-treating a substrate to be heat-treated.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process,
A thermal oxide film is formed on the wafer surface by heating the wafer, such as by loading a substrate, for example, a semiconductor wafer one by one, into a heat treatment furnace and irradiating the substrate with light, as in a lamp annealing apparatus or CVD. A single-wafer heat treatment apparatus that forms a pn junction by thermally diffusing impurity atoms or performs various annealing treatments is widely used in various processes. FIG. 5 shows an example of the configuration of a lamp annealing apparatus which is one of the heat treatment apparatuses.

[0005] The lamp annealing apparatus whose schematic side sectional view is shown in FIG. 5 includes a heat treatment furnace 10 having an opening 12 for loading and unloading a semiconductor wafer W. The upper furnace wall of the heat treatment furnace 10 is formed of a material having infrared transmittance, for example, quartz glass, and serves as a light incident window 14. The opening 12 of the heat treatment furnace 10 is
To open and close. Although not shown, on the surface of the heat treatment furnace 10 facing the opening 12, the support arm supports the wafer W in a horizontal posture, and the wafer W before the heat treatment is carried into the heat treatment furnace 10 and is subjected to the heat treatment. Wafer W
A wafer loading / unloading device for unloading the wafer from the heat treatment furnace 10 is provided.

A wafer support ring 18 made of SiC or the like is disposed inside the heat treatment furnace 10, and the wafer support ring 18 is rotatably held in a horizontal posture by a wafer holding and rotating mechanism 20. I have. Wafer W
Are supported on the wafer support ring 18 in a horizontal posture.
Further, there is provided a wafer transfer mechanism 24 having a plurality of, for example, three support pins 22 for supporting the wafer W in contact with the lower surface of the wafer W and reciprocating vertically.

A lamp house 26 is provided above the heat treatment furnace 10 so as to face the light incident window 14. In the lamp house 26, a plurality of lamps 28 such as a halogen lamp and an arc lamp are arranged in the same plane, and a reflector 30 is provided for each lamp 28. Then, the infrared light emitted from each lamp 28 is efficiently condensed by the reflector 30 and transmitted through the light irradiation window 14 and irradiated into the heat treatment furnace 10.

In the inside of the heat treatment furnace 10, a plurality of gas blowout holes made of a material having infrared transmittance, for example, quartz glass, are opposed to the upper surface of the wafer W supported on the wafer support ring 18. A gas flow distribution plate 32 having a hole 34 is provided. This gas flow distribution plate 3
Between the light entrance window 2 and the light entrance window 14, a gas introduction chamber 36 into which a processing gas such as nitrogen is introduced is provided.
The flow path is connected to a processing gas supply source through a gas introduction path (not shown). On the other hand, an annular gas exhaust path 38 is formed between the wafer holding and rotating mechanism 20 and the inner peripheral wall surface of the heat treatment furnace 10, and the gas exhaust path 38 is connected to an exhaust port (not shown). Further, in order to keep the airtightness of the inside of the heat treatment furnace 10 high, O-rings 40 are respectively attached to a contact portion with the gate valve 16 and a joint portion with the light incident window 14.

A plurality of temperature detectors are provided at the bottom of the heat treatment furnace 10 so as to face the lower surface of the wafer W supported on the wafer support ring 18 and the lower surface of the wafer support ring 18.
For example, radiation thermometers 42a, 42b, 42c, and 42d are provided. These radiation thermometers 42a, 42b, 4
By 2c and 42d, the temperatures of a plurality of positions of the wafer W and the temperature of the wafer support ring 18 during the heat treatment are measured in a non-contact manner.

The lamp house 26 is divided into a plurality of heating zones, and the power supplied to the lamp 28 can be adjusted for each heating zone. In addition, the radiation thermometers 42a, 4a,
2b, 42c, 42d and a controller (not shown in FIG. 5) are provided. And as shown in the block diagram of the temperature control system in FIG. 6, the temperature control is performed individually for each heating zone.

In the lamp annealing apparatus, as shown in a block diagram of FIG. 7, radiation thermometers 42a, 42b,
The temperature Y of the wafer W measured by 42c and 42d
(s) and a deviation E (s) between the target temperature R (s) are calculated, and the controller 44 performs a control operation based on the calculated deviation E (s).
Feedback control such as calculating the power U (s) to be supplied to the lamp 28 is performed (C (s) in FIG. 7).
And G (s) denote the respective transfer functions of the controller and equipment (lamp and wafer). As shown in FIG. 8, the controller 44 performs proportional, integral, and derivative calculations on the temperature deviation e (t) at each time point (in FIG. 8, Kp, Ki, and Kd are used for adjustment). Conventionally, a PID controller that calculates the power u (t) supplied to the lamp by summing the results of these calculations is used.

One application of the lamp annealing apparatus is to form a pn junction by thermal diffusion. That is, in order to achieve high integration of a semiconductor device, high-speed operation as well as miniaturization of the device are important factors. For example, in order to increase the operation speed of a diode, it is necessary to reduce the depth of a pn junction. Therefore, it is necessary to electrically activate ions of B, As, P, etc. implanted in a wafer without diffusion. There is. For this purpose, a device is required to quickly raise the temperature of the wafer to the activation temperature of the ions and, after the temperature is raised, rapidly cool the wafer to a temperature at which the ions do not diffuse. A lamp annealing device is used for this purpose. You. In particular, in a process called spike annealing using a lamp annealing device, the sequence consists of only a temperature increase and a temperature decrease.The wafer is heated while maintaining a constant temperature increase rate, and the temperature is decreased immediately after the wafer reaches a predetermined temperature. Start. Then, in order to keep the heating rate constant, the target temperature is given by a ramp (Ramp; slope) function, and the temperature is controlled by PID control.

[0011]

When temperature control is performed using a general PID controller, as shown in FIG. 9A, when the target temperature is given by a step function, Has a steady-state deviation of zero. However, as shown in FIG. 9B, when the target temperature is given by a ramp function, a steady-state deviation always occurs. In the above-described spike anneal processing, a constant heating rate (° C. /
In sec), the wafer is heated, so that the target temperature function becomes a ramp function. Therefore, if the PID control is performed as in the related art, a steady-state deviation always occurs.

When a steady deviation occurs during the heating of the wafer,
It becomes difficult to accurately control the temperature of the wafer during the temperature raising process, and the following problem occurs. That is, the wafer heating rate does not match the target heating rate, and the required heating rate cannot be obtained. As a result, the heat treatment quality is affected. In addition, the temperature deviation changes for each heating zone, making it difficult to control the temperature of each heating zone to be equal, and causing a temperature variation between the heating zones. As a result, there is a problem that processing is uneven in a wafer surface and a slip defect occurs.

The present invention has been made in view of the above circumstances. When a substrate is heated and heated at a constant speed, a steady-state deviation does not occur, and a required heating speed can be obtained. It is another object of the present invention to provide a heat treatment apparatus for a substrate which can be controlled so that the temperatures of a plurality of divided heating zones are equal.

[0014]

The invention according to claim 1 is
A heat treatment furnace in which a substrate is loaded and held therein, heating means for heating the substrate held in the heat treatment furnace, temperature measurement means for measuring the temperature of the substrate in the heat treatment furnace, and this temperature measurement means A temperature control means for controlling the heating means based on a deviation between the temperature of the substrate at each time point measured by the temperature and the temperature of the substrate at the time point in a preset temperature rise / fall change. , Wherein the temperature control means has a control unit configured such that the pole of the open loop transfer function has 0,0.

According to a second aspect of the present invention, in the heat treatment apparatus according to the first aspect, the control unit comprises: a proportional + integral + differential +
It is characterized by generating a signal for a double integration control operation.

According to a third aspect of the present invention, in the heat treatment apparatus of the second aspect, the control unit is configured by connecting a double integrator to a PID controller in parallel.

According to a fourth aspect of the present invention, in the heat treatment apparatus according to the first aspect, the control section generates a signal of a proportional + integral + double integral or a control operation equivalent thereto. And

According to a fifth aspect of the present invention, in the heat treatment apparatus of the fourth aspect, the control unit connects a double integrator to a PI controller in parallel or connects an integrator to a PID controller in series. It is characterized by having been done.

According to a sixth aspect of the present invention, in the heat treatment apparatus according to any one of the first to fifth aspects, the control unit is used when the substrate in the heat treatment furnace is heated at a constant heating rate. Switching means for switching to perform the switching.

Here, the cause of the occurrence of the steady-state deviation in the process of heating the substrate to increase the temperature will be described. The “internal model principle” is generally known as a condition under which the steady-state error does not occur. According to the internal model principle, “in order for the steady-state error to be zero, the pole of the open-loop transfer function is Must include the poles. "

First, the poles of the open loop transfer function are determined. In the feedback control system as shown in FIG. 7, the open loop transfer function is C (s) G (s). When the device is approximated by a first-order lag system, the transfer function G (s) of the device can be expressed by the following equation: G (s) = K / (Ts + 1) (1) In the equation (1), K is a gain constant, T is a time constant, and s is a Laplace operator.

Further, the controller of the transfer function C (s), in the conventional Such PID controller, C (s) = Kp + Ki × (1 / s) + Kd × s = (Kp × s + Ki + Kd × s 2) / s (2) From equations (1) and (2), the open-loop transfer function C
(s) G (s) is a C (s) G (s) = [(Kp × s + Ki + Kd × s 2) K ] / [s (Ts + 1)] ... (3). To find the pole of the open loop transfer function, (3)
Solving for s with the denominator = 0 in the right-hand side of the equation,
It can be seen that there are two poles, s = 0 and s = -1 / T.

Next, the pole of the target temperature function R (s) is obtained. (1) When the target temperature function is a step function, R
Since (s) = 1 / s, the pole is s = 0. (2) If the target temperature function is a ramp function, R (s)
Since = 1 / s ² , the pole is s = 0,0.

When the target temperature function is a step function,
The pole is 0, which is the pole of the open loop transfer function 0, -1 /
T. Therefore, no steady-state deviation occurs as shown in FIG. On the other hand, if the target temperature function is a ramp function, the poles are 0,0, which are not included in poles 0, -1 / T of the open loop transfer function. Therefore, P
When an ID controller is used, a steady-state deviation always occurs, as shown in FIG.

From the above considerations, when the target temperature function is a ramp function, the poles of the open loop transfer function need to have 0,0 in order to prevent the occurrence of the steady-state deviation. It can be seen that it is necessary to increase the order of the denominator of the transfer function C (s) of the controller.

In the substrate heat treatment apparatus according to the first aspect of the present invention, the temperature of the substrate is set in advance by temperature control means having a control unit configured so that the pole of the open loop transfer function has 0,0. The heating means is controlled so as to cause the vertical change. Therefore, the poles of the open-loop transfer function include all the poles of the target temperature function, which is a ramp function, and satisfy the conditions of the “internal model principle”. Does not occur.

In the heat treatment apparatus according to each of the second to fifth aspects of the present invention, the control unit is configured so that the pole of the open loop transfer function has 0,0.

In the heat treatment apparatus according to the present invention, when the substrate in the heat treatment furnace is heated at a constant heating rate, that is, when the target temperature is given by a ramp function, the open-loop transmission is performed by the switching means. Since the switching is performed so that the control unit configured so that the pole of the function has 0,0 is used, no steady-state error occurs at that time. In other cases, the temperature of the substrate may be controlled by PID control or the like.

[0029]

Preferred embodiments of the present invention will be described below with reference to the drawings.

The present invention is applied to a lamp annealing apparatus as shown in FIGS. 5 to 7, for example. Since the configuration of the lamp annealing apparatus has been described above, the description is omitted here.

In the lamp annealing apparatus according to the present invention,
A controller 4 configured such that the open-loop transfer function has 0,0 in a feedback control system as shown in FIG.
4 is used. Specifically, as shown in FIG. 1, a double integrator is connected in parallel to an existing PID controller, and the controller 4
4 are configured. The double integrator is obtained by connecting two integrators in series. The transfer function of such a controller, C (s) = Kp + Ki × (1 / s) + Ki2 × (1 / S 2) + Kd × s = (Kp × s 2 + Ki × s + Ki2 + Kd × s 3) / s 2 ... (4) Above (1) and equation (4), the open loop transfer function C (s) G (s) is, C (s) G (s) = ^{[(Kp × s 2 + Ki ×} s + Ki2 + Kd × s 3) K ] / [S ² (Ts + 1)] (5) In the equation (5), Ki2 is a parameter for adjusting the double integrator.

When the pole of the open loop transfer function is obtained by setting the denominator of the right side of the equation (5) to 0, s = 0, 0, -1 /
It becomes T. Since these include all of the poles 0 and 0 of the ramp function, no steady-state deviation occurs in the process of heating the wafer at a constant heating rate. By eliminating the temperature deviation in this way, the target temperature matches the wafer temperature, and
The temperature difference between a plurality of heating zones is also eliminated. Therefore, the target heating rate is kept constant, and high in-plane uniformity is obtained in wafer processing.

FIG. 2A shows a linear change in the target temperature, FIG. 2B shows a simulation result for the PID controller of the conventional apparatus, and FIG. 2C shows a simulation result for the controller of the apparatus according to the present invention. Are respectively shown. As the simulation conditions, the control was started at a temperature of 500 ° C., and the wafer was heated to a temperature of 1100 ° C. while maintaining a rate of temperature increase of 100 ° C./sec. FIG. 2 (b)
As shown in the figure, in the PID controller of the conventional apparatus, a deviation close to 5 ° C. occurs between the target temperature and the wafer temperature in the steady state, whereas in the controller of the apparatus according to the present invention, the stationary deviation Has not occurred.

As a controller configured so that the open-loop transfer function has 0,0, as shown in FIG.
One in which an integrator is connected in series to a D controller, or one in which a double integrator is connected in parallel to a PI controller as shown in FIG. 4 (this is equivalent to the one shown in FIG. 3) Can be used.

In the above-described embodiment, the feedback control system is constituted by using the PID controller, the double integrator, and the like. However, the microcomputer is programmed to perform the same control operation. You may make it comprise a control part.

[0036]

When the substrate heat treatment apparatus according to the first aspect of the present invention is used, no steady-state deviation occurs when the substrate is heated and heated at a constant speed, so that the temperature of the substrate during the temperature rising process can be accurately determined. Can be managed. For this reason, a required temperature rising rate can be obtained, and the quality of the heat treatment can be improved. Further, it is possible to control the temperature of each of the plurality of divided heating zones to be equal, to improve the uniformity of the processing on the substrate surface, and to prevent the occurrence of slip defects. Can be.

In the heat treatment apparatuses according to the second to fifth aspects of the present invention, the above effects of the first aspect of the invention can be reliably obtained.

In the heat treatment apparatus according to the sixth aspect of the invention, when the substrate is heated at a constant heating rate, the temperature can be controlled so as not to cause a steady-state deviation. Thus, the required temperature management can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment of the present invention and showing a configuration example of a controller used in a lamp annealing apparatus.

FIG. 2 is a diagram for explaining a difference between an operation of temperature control by a PID controller of a conventional device and an operation of temperature control by a controller of the device according to the present invention. (B) shows a simulation result for the PID controller of the conventional device, and (c) shows a simulation result for the controller of the device according to the present invention.

FIG. 3 is a configuration diagram of a controller showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of a controller showing still another embodiment of the present invention.

FIG. 5 is a schematic side sectional view showing an example of a configuration of a lamp annealing apparatus which is one of the heat treatment apparatuses.

FIG. 6 is a block diagram showing an example of a temperature control system of the lamp annealing apparatus shown in FIG.

FIG. 7 is a block diagram showing a feedback control system in the lamp annealing apparatus.

FIG. 8 shows a PID used in a conventional lamp annealing apparatus.
It is a block diagram of a controller.

FIG. 9 is a diagram for explaining a steady-state deviation that occurs when temperature control is performed using a PID controller,
(A) shows that the steady-state error becomes 0 when the target temperature is given by the step function, and (b) shows that the steady-state error always occurs when the target temperature is given by the ramp function.

[Explanation of symbols]

 Reference Signs List 10 heat treatment furnace 14 light entrance window 18 wafer support ring 28 lamp 42a, 42b, 42c radiation thermometer 44 controller W wafer

Claims (6)

[Claims] 1. A heat treatment furnace in which a substrate is loaded and held therein, a heating means for heating the substrate held in the heat treatment furnace, and a temperature measurement means for measuring the temperature of the substrate in the heat treatment furnace Temperature control means for controlling the heating means based on a difference between the substrate temperature at each time point measured by the temperature measurement means and the substrate temperature at the time point in a preset temperature rise / fall change. An apparatus for heat treating a substrate, wherein the temperature control means has a controller configured so that a pole of an open loop transfer function has 0,0. 2. The heat treatment apparatus for a substrate according to claim 1, wherein the control unit generates a signal for a control operation of proportional + integral + differential + double integral. 3. The substrate heat treatment apparatus according to claim 2, wherein the control unit is configured by connecting a double integrator to a PID controller in parallel. 4. The substrate heat treatment apparatus according to claim 1, wherein the control unit generates a signal of a proportional + integral + double integral or control operation equivalent thereto. 5. The heat treatment apparatus for a substrate according to claim 4, wherein the control unit is configured by connecting a double integrator to a PI controller in parallel or by connecting an integrator to a PID controller in series. 6. The substrate according to claim 1, further comprising a switching unit configured to switch the control unit to be used when the substrate in the heat treatment furnace is heated at a constant heating rate. Heat treatment equipment.