WO2009116400A1

WO2009116400A1 - Annealing apparatus and overheat prevention system

Info

Publication number: WO2009116400A1
Application number: PCT/JP2009/054159
Authority: WO
Inventors: 河西　繁; 鈴木　智博
Original assignee: 東京エレクトロン株式会社
Priority date: 2008-03-19
Filing date: 2009-03-05
Publication date: 2009-09-24
Also published as: JP2009231353A

Abstract

Annealing apparatus (100) is provided with a chamber (2) for housing a wafer (W), heating sources (17a, 17b) which have a plurality of LEDs (33) irradiating the wafer (W) within the chamber (2) with light, a power source part (60) which feeds power to the LEDs (33) of the heating sources (17a, 17b), light transmission members (18a, 18b) which transmit light from the LEDs (33), an exhaustion mechanism which exhausts the inside of the chamber (2), a temperature calculation part (62) which calculates the temperature of the LEDs (33) on the basis of current-voltage properties in pn-junction of the LEDs (33) and those in the resistance of the LEDs, and an interlock part (63) which stops feeding of power by the power source part (60) when the temperature calculated by the temperature calculation part (62) exceeds a predetermined temperature.

Description

Annealing equipment and overheat prevention system

The present invention relates to an annealing apparatus that performs annealing by irradiating a semiconductor wafer or the like with light from a light emitting element such as an LED, and an overheat prevention system used therefor.

In the manufacture of semiconductor devices, there are various types of heat treatment such as film formation, oxidation diffusion treatment, modification treatment, annealing treatment on a semiconductor wafer (hereinafter simply referred to as a wafer) that is a substrate to be processed. With the demand for higher speed and higher integration, annealing after ion implantation, in particular, is directed to higher temperature rise and fall in order to minimize diffusion. As an annealing apparatus capable of such high-speed temperature rising / lowering, an apparatus using an LED (light emitting diode) as a heating source has been proposed (for example, JP-T-2005-536045).

Incidentally, when an LED is used as a heating source of the annealing apparatus, it is necessary to generate a large amount of light energy in response to rapid heating, and therefore, it is necessary to mount the LEDs at a high density.

However, it is known that the amount of light emitted from a LED rises due to temperature rise by heat, and the effect of heat generation of the LED itself (of the input energy that cannot be extracted as light) by mounting the LED at high density. When becomes larger, a sufficient amount of light emission cannot be obtained from the LED.

For this reason, a technique for cooling the LED to suppress a decrease in the amount of light emission due to heat has been proposed (for example, Japanese Patent Application Laid-Open No. 2008-16545). However, an excessive current flows through the LED even after cooling. May cause abnormal overheating. In such a case, the efficiency of the LED is not only lowered, but the LED may be destroyed if left as it is.

For this reason, the temperature in the vicinity of the LED is detected by a temperature sensor such as a thermocouple, and the interlock is applied when the temperature exceeds a predetermined temperature.

However, since the LEDs are very small and are mounted in a state of being arranged in a large number on the support, a temperature sensor cannot be installed at a position close to the LEDs, and the temperature cannot be measured with high accuracy. In addition, when a temperature sensor is used, the timing from when the LED is overheated until the temperature is detected is later than the timing at which failure destruction occurs. In order to avoid this, if the interlock value is installed in the vicinity of the overheating temperature, even if an abnormality occurs, it cannot be detected immediately, and the LED is destroyed. Therefore, the interlock value must be set low, but if so, the interlock function cannot be fully exhibited.

Summary of the Invention

An object of the present invention is to provide an annealing apparatus using a light emitting element such as an LED as a heating source, which can quickly and accurately grasp the temperature of the light emitting element and appropriately prevent overheating, and its An object of the present invention is to provide an overheat prevention system used in such an annealing apparatus.

According to a first aspect of the present invention, a processing chamber in which an object to be processed is accommodated and a plurality of light emitting elements having a pn junction that irradiates light to the object to be processed are provided, and at least one of the objects to be processed is provided. A heating source provided so as to face the surface, a power supply unit that supplies power to the light emitting element of the heating source, a light transmissive member that is provided corresponding to the heating source and transmits light from the light emitting element, An exhaust mechanism for exhausting the processing chamber, a temperature calculation unit for calculating a temperature of the light emitting element based on a current-voltage characteristic at a pn junction of the light emitting element or a current-voltage characteristic at a resistance of the light emitting element, and the temperature An annealing apparatus is provided that includes an interlock unit that stops power supply to the power supply unit when the temperature calculated by the calculation unit exceeds a predetermined temperature.

According to a second aspect of the present invention, there is provided an overheating prevention system for use in an annealing apparatus that performs an annealing process on a substrate in a processing chamber by a heating source including a plurality of light emitting elements having a pn junction. a temperature calculating unit that calculates a temperature of the light emitting element based on a current-voltage characteristic in a pn junction or a current-voltage characteristic in a resistance of the light emitting element; and the temperature calculated in the temperature calculating unit exceeds a predetermined temperature In some cases, an overheat prevention system including an interlock unit that stops power supply to the light emitting element is provided.

In the first and second aspects, the temperature calculation unit uses the current-voltage characteristics at the pn junction of the light emitting element when the current flowing through the light emitting element is a small current of a predetermined value or less. The temperature of the light emitting element can be calculated based on the current-voltage characteristics of the resistance of the light emitting element when the current flowing through the light emitting element is a large current equal to or greater than a predetermined value. .

In addition, as the light emitting element, an LED can be exemplified as a typical example.

According to the present invention, in such an annealing apparatus using a light emitting element such as an LED, the current-voltage characteristic at the pn junction of the light emitting element or the current-voltage characteristic at the resistance of the light emitting element such as bulk resistance and contact resistance is obtained. Based on this, the temperature calculation unit calculates the temperature of the light emitting element, and when the calculated temperature exceeds a predetermined value, the interlock unit issues a signal to stop power feeding, so the temperature of the light emitting element can be quickly and accurately determined. It is possible to grasp and appropriately prevent overheating of the light emitting element.

Also, since the temperature is estimated by calculation from the current-voltage characteristics when power is supplied to a large number of light emitting elements, the temperature can be grasped as an average value of the large number of light emitting elements. For this reason, temperature detection can be performed with higher accuracy than when a sensor is provided.

It is sectional drawing which shows schematic structure of the annealing apparatus which concerns on one Embodiment of this invention. It is sectional drawing which expands and shows the heating source of the annealing apparatus of FIG. It is sectional drawing which expands and shows the part electrically fed to LED of the annealing apparatus of FIG. It is a figure which shows the specific LED arrangement | sequence and electric power feeding method of the LED array of the annealing apparatus of FIG. It is a figure for demonstrating the connection form of LED of the annealing apparatus of FIG. It is a bottom view which shows the heating source of the annealing apparatus of FIG. It is a figure which shows the relationship between the preset temperature at the time of wafer heating, and the power supplied to LED. It is a figure which shows the electric current and voltage of LED. It is a figure which shows the IV characteristic obtained by flowing the pulse current of various values so that temperature may not rise to LED, and measuring the voltage at that time. FIG. 4 is a diagram showing current-voltage characteristics of an LED, divided into pn junction contribution and resistance component contribution. It is a figure which expands and shows the low current part of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, an example of an annealing apparatus for annealing a wafer having impurities implanted on the surface will be described.
1 is a cross-sectional view showing a schematic configuration of an annealing apparatus according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view showing a heating source of the annealing apparatus of FIG. 1, and FIG. 3 is an LED of the annealing apparatus of FIG. It is sectional drawing which expands and shows the part which supplies electric power to.

The annealing apparatus 100 is hermetically configured and has a processing chamber 1 into which a wafer W is loaded. The processing chamber 1 includes a columnar annealing processing unit 1a in which the wafer W is disposed and a gas diffusion unit 1b provided in a donut shape outside the annealing processing unit 1a. The gas diffusion portion 1b is higher in height than the annealing treatment portion 1a, and the cross section of the processing chamber 1 is H-shaped. The gas diffusion portion 1 b of the processing chamber 1 is defined by the chamber 2. Circular holes 3a and 3b corresponding to the annealed portion 1a are formed in the upper wall 2a and the bottom wall 2b of the chamber 2, and these holes 3a and 3b are made of Al or Al alloy, which is a high thermal conductivity material, respectively. The

cooling members

4a and 4b are fitted. The

cooling members

4a and 4b have

flange portions

5a and 5b, and the

flange portions

5a and 5b are supported by the upper wall 2a and the bottom wall 2b of the chamber 2 via a thermal insulator 80 such as Ultem. The thermal insulator 80 is provided in order to minimize the heat input from the chamber 2 because the

flange portions

5a and 5b are cooled to, for example, −50 ° C. or lower as described later. Seal members 6 are interposed between the

flange portions

5a and 5b and the thermal insulator 80, and between the thermal insulator 80 and the upper wall 2a and the bottom wall 2b, and are in close contact with each other. Further, portions of the

cooling members

4a and 4b that are exposed to the atmosphere are covered with a heat insulating material.

The processing chamber 1 is provided with a support member 7 for horizontally supporting the wafer W in the annealing processing section 1a. The support member 7 can be moved up and down when the wafer W is transferred by a lifting mechanism (not shown). Yes. Further, a processing gas introduction port 8 into which a predetermined processing gas is introduced from a processing gas supply mechanism (not shown) is provided on the top wall of the chamber 2, and a processing gas pipe for supplying the processing gas to the processing gas introduction port 8. 9 is connected. An exhaust port 10 is provided on the bottom wall of the chamber 2, and an exhaust pipe 11 connected to an exhaust device (not shown) is connected to the exhaust port 10. Further, a loading / unloading port 12 for loading / unloading the wafer W into / from the chamber 2 is provided on the side wall of the chamber 2, and the loading / unloading port 12 can be opened and closed by a gate valve 13. The processing chamber 1 is provided with a temperature sensor 14 for measuring the temperature of the wafer W supported on the support member 7. The temperature sensor 14 is connected to a measurement unit 15 outside the chamber 2, and a temperature detection signal is output from the measurement unit 15 to a process controller 70 described later.

Circular recesses 16 a and 16 b are formed on the surfaces of the

cooling members

4 a and 4 b facing the wafer W supported by the support member 7 so as to correspond to the wafer W supported by the support member 7. And in this recessed

part

16a, 16b, the

heat sources

17a and 17b which mounted the light emitting diode (LED) are arrange | positioned so that the

cooling members

4a and 4b may be directly contacted.

Light transmitting members

18a and 18b that transmit light from LEDs mounted on the

heating sources

17a and 17b to the wafer W side so as to cover the

recesses

16a and 16b on the surfaces of the

cooling members

4a and 4b facing the wafer W. Is screwed. For the

light transmitting members

18a and 18b, a material that efficiently transmits light emitted from the LED is used, and for example, quartz is used.

Cooling

medium channels

21a and 21b are provided in the

cooling members

4a and 4b, and a liquid cooling medium capable of cooling the

cooling members

4a and 4b to 0 ° C. or less, for example, about −50 ° C. therein. For example, a fluorine-based inert liquid (trade name: Fluorinert, Galden, etc.) is passed. Cooling

medium supply pipes

22a and 22b and cooling

medium discharge pipes

23a and 23b are connected to the cooling

medium flow paths

21a and 21b of the

cooling members

4a and 4b. As a result, the cooling medium can be circulated through the cooling

medium flow paths

21a and 21b to cool the

cooling members

4a and 4b.

Note that a cooling water flow path 25 is formed in the chamber 2, and normal temperature cooling water flows therethrough, thereby preventing the temperature of the chamber 2 from rising excessively. .

As shown in an enlarged view in FIG. 2, the

heating sources

17 a and 17 b are supported by an insulating high heat conductive material, typically a support 32 made of AlN ceramics, and supported by the support 32 via an electrode 35. In addition, the LED array 34 includes a plurality of LEDs 33 and a heat diffusing member 50 made of Cu, which is a highly thermally conductive material bonded to the back side of the support 32. The support 32 is formed with a pattern of a highly conductive electrode 35, for example, gold-plated on copper, and the LED 33 is attached to the electrode 35 with a silver paste 56 which is a bonding material having a high thermal conductivity. Moreover, the support body 32 and the thermal diffusion member 50 are joined by solder 57 which is a high thermal conductive joining material from the viewpoint of reliability. Further, the heat diffusion member 50 and the cooling member 4a (4b) on the back surface side of the LED array 34 are screwed together with a silicon grease 58 as a high thermal conductive bonding material interposed therebetween. With such a configuration, the cooling heat transferred from the cooling medium to the

cooling members

4a and 4b having high thermal conductivity with high efficiency is in contact with the entire surface, the heat diffusion member 50 having high heat conductivity, the support 32, and the electrode 35. The LED 33 is reached via In other words, the heat generated by the LED 33 is cooled by the cooling medium through a path with good thermal conductivity such as the silver paste 56, the electrode 35, the support 32, the solder 57, the heat diffusion member 50, and the silicon grease 58. The

members

4a and 4b can escape very effectively.

A wire 36 is connected between one LED 33 and the electrode 35 of the adjacent LED 33. Further, a reflective layer 59 containing, for example, TiO ₂ is provided on the surface of the support 32 where the electrode 35 is not provided, and the light emitted from the LED 33 toward the support 32 is reflected effectively. It can be taken out. The reflectance of the reflective layer 59 is preferably 0.8 or more.

A reflecting plate 55 is provided between the adjacent LED arrays 34, so that the entire circumference of the LED array 34 is surrounded by the reflecting plate 55. As the reflection plate 55, for example, a Cu plate that is gold-plated is used so that light traveling in the lateral direction can be reflected and effectively extracted.

Each LED 33 is covered with a lens layer 20 made of, for example, a transparent resin. The lens layer 20 has a function of extracting light emitted from the LED 33 and can also extract light from the side surface of the LED 33. The shape of the lens layer 20 is not particularly limited as long as it has a lens function. However, considering the ease of manufacturing and efficiency, a substantially hemispherical shape is preferable. This lens layer 20 has a refractive index between the LED 33 having a high refractive index and air having a refractive index of 1, in order to alleviate total reflection caused by direct emission of light from the LED 33 into the air. Provided.

The space between the support 32 and the

light transmission members

18a and 18b is evacuated, and both sides (upper surface and lower surface) of the

light transmission members

18a and 18b are in a vacuum state. Therefore, the

light transmitting members

18a and 18b can be made thinner than the case where the

light transmitting members

18a and 18b function as a partition between the atmospheric state and the vacuum state.

The LED 33 of the heating source 17a is fed with power from the power supply unit 60 through the feeding line 61a, the feeding member 41 and the feeding rod 38 (see FIG. 3), and the LED 33 of the heating source 17b is fed from the power supply unit 60 with the feeding line 61b and feeding member. Power is supplied through 41 and the power supply rod 38.

Feed control units

42a and 42b are connected to the feed line 61a and the feed line 61b.

As shown in FIG. 3 in an enlarged manner, a feeding electrode 51 is inserted into

holes

50a and 32a formed in the thermal diffusion member 50 and the support body 32, respectively, and this feeding electrode 51 is connected to the electrode 35 by soldering. Has been. An electrode rod 38 extending through the inside of the

cooling members

4 a and 4 b is connected to the power supply electrode 51 at an attachment port 52. A plurality of, for example, eight electrode bars 38 are provided for each LED array 34 (only two are shown in FIGS. 1 and 3), and the electrode bars 38 are covered with a protective cover 38a made of an insulating material. The electrode rod 38 extends to the upper end portion of the cooling member 4a and the lower end portion of the cooling member 4b, and the receiving member 39 is screwed there. An insulating ring 40 is interposed between the receiving member 39 and the

cooling members

4a and 4b. Here, gaps between the protective cover 38a and the cooling member 4a (4b) and between the protective cover 38a and the electrode rod 38 are brazed to form a so-called feedthrough.

The power supply member 41 is connected to a receiving member 39 attached to each electrode bar 38. The power supply member 41 is covered with a protective cover 44 made of an insulating material. A pogo pin (spring pin) 41 a is provided at the tip of the power supply member 41, and when each pogo pin 41 a comes into contact with the corresponding receiving member 39, the power supply line 61 a, the power supply member 41, and the electrode rod 38 are connected from the power supply unit 60. Power is supplied to each LED 33 of the heating source 17a via the power supply electrode 51 and the electrode 35, and power is supplied to each LED 33 of the heating source 17b via the power supply line 61b, the power supply member 41, the electrode bar 38, the power supply electrode 51 and the electrode 35. It has become so. In this case, the power

supply control units

42a and 42b supply the LED 33 with the voltage applied by the power supply unit 60 as a DC waveform voltage. Conventionally, power supply to the LED is generally PWM drive that provides a pulsed voltage with a predetermined duty ratio. However, by using direct current drive in this manner, a heat generation margin is improved. The DC waveform voltage means a voltage that always drives the LED in the ON state, not a voltage that drives the LED on and off in a pulsed manner.

The LED 33 emits light by being fed in this way, and the annealing process is performed by heating the wafer W from the front and back surfaces with the light. Since the pogo pin 41a is urged toward the receiving member 39 by a spring, the power supply member 41 and the electrode bar 38 can be reliably contacted.

In FIG. 1, the middle of the power supply member 41 is drawn, and the structure of the electrode rod 38, the power supply electrode 51, and the connection portion thereof is omitted. In FIG. 2, the feeding electrode 51 is omitted.

The LED array 34 has a hexagonal shape as shown in FIG. In the LED array 34, it is extremely important how to supply a sufficient voltage to each LED 33 and reduce the area loss of the power feeding portion to increase the number of LEDs 33 to be mounted. Here, the LED array 34 is equally divided into two

regions

341 and 342, and these

regions

341 and 342 are divided into three

power supply regions

341a, 341b, 341c and 342a, 342b, 342c, respectively.

As electrodes for supplying power to these power supply regions, three

negative electrodes

51a, 51b, 51c and one common positive electrode 52 are arranged in a straight line on the region 341 side, and three negative electrodes are disposed on the region 342 side. 53a, 53b, 53c and one common positive electrode 54 are arranged in a straight line. The common positive electrode 52 supplies power to the

power supply regions

341a, 341b, and 342c, and the common positive electrode 54 supplies power to the

power supply regions

342a, 342b, and 341c.

As shown in FIG. 5, the plurality of LEDs 33 in each power feeding area are arranged in parallel in two sets connected in series. By doing in this way, the dispersion | variation in each LED and the dispersion | variation in voltage can be suppressed.

The LED array 34 having such a structure is arranged on the cooling member 4a (4b) without a plurality of gaps as shown in FIG. In one LED array 34, about 1000 to 2000 LEDs 33 are mounted. As the LED 33, one having a wavelength of emitted light in the range of ultraviolet light to near infrared light, preferably in the range of 0.36 to 1.0 μm is used. Examples of such a material that emits light in the range of 0.36 to 1.0 μm include compound semiconductors based on GaN, GaAs, GaP, and the like. Among these, a material made of a GaAs-based material having a radiation wavelength in the vicinity of 850 to 970 nm, which has a high absorptance with respect to a silicon wafer W used as a heating target, is preferable.

A common temperature calculation unit 62 is connected to the power

supply control units

42a and 42b. The temperature calculation unit 62 calculates the temperature of the LED 33 based on the current-voltage (IV) characteristics at the pn junction of the LED 33 or the current-voltage (IV) characteristics at the resistance of the LED 33 such as bulk resistance and contact resistance. .

That is, the IV characteristics in the pn junction of the LED 33 and the IV characteristics in the resistance such as the bulk resistance and the contact resistance are expressed as a function of temperature as will be described later. By using either of these, The temperature can be calculated, and the temperature of the LED 33 can be estimated from the calculated temperature.

The interlock unit 63 is connected to the temperature calculation unit 62. The interlock unit 63 receives the temperature signal calculated by the temperature calculation unit 62, determines whether or not the temperature exceeds a predetermined temperature, and when the temperature exceeds the predetermined temperature, the power supply unit 60 receives a power supply stop signal. The power supply is stopped to prevent overheating and destruction of the LED 33. That is, the temperature calculation unit 62 and the interlock unit 63 function as an overheat prevention system.

Each component of the annealing apparatus 100 is connected to and controlled by a process controller 70 having a microprocessor (computer), as shown in FIG. For example, the process controller 70 performs transmission of control commands to the power

supply control units

42a and 42b, drive system control, gas supply control, and the like. Connected to the process controller 70 is a user interface 71 including a keyboard on which an operator inputs commands for managing the annealing apparatus 100, a display for visualizing and displaying the operating status of the annealing apparatus 100, and the like. . Further, the process controller 70 causes each component of the annealing apparatus 100 to execute processing according to a control program for realizing various processes executed by the annealing apparatus 100 under the control of the process controller 70 and processing conditions. A storage unit 72 capable of storing a program for processing, that is, a processing recipe, is connected. The processing recipe may be stored in a fixed storage medium such as a hard disk, or set in a predetermined position of the storage unit 72 while being stored in a portable storage medium such as a CDROM or DVD. May be. Furthermore, you may make it transmit a recipe suitably from another apparatus via a dedicated line, for example. Then, if necessary, an arbitrary processing recipe is called from the storage unit 72 by an instruction from the user interface 71 and is executed by the process controller 70, so that the desired processing in the annealing apparatus 100 is performed under the control of the process controller 70. Is performed.

Next, the annealing process operation in the annealing apparatus 100 as described above will be described.
First, the gate valve 13 is opened, the wafer W is loaded from the loading / unloading port 12, and placed on the support member 7. Thereafter, the gate valve 13 is closed to make the inside of the processing chamber 1 hermetically sealed, the inside of the processing chamber 1 is exhausted by an exhaust device (not shown) through the exhaust port 11, and the processing gas pipe 9 and the processing gas are supplied from a processing gas supply mechanism (not shown). A predetermined processing gas such as argon gas or nitrogen gas is introduced into the processing chamber 1 through the gas inlet 8 and the pressure in the processing chamber 1 is maintained at a predetermined pressure in the range of 100 to 10,000 Pa, for example.

On the other hand, the cooling

members

4a and 4b circulate a liquid cooling medium, for example, a fluorine-based inert liquid (trade name Fluorinert, Galden, etc.) in the cooling

medium flow paths

21a and 21b, and cause the LED element 33 to have a predetermined temperature of 0 ° C. The temperature is preferably cooled to a temperature of −50 ° C. or lower.

Then, power is supplied from the power source 60 to each LED 33 of the heating source 17a through the power supply line 61a, the power supply member 41, the electrode bar 38, the power supply electrode 51, and the electrode 35, and the power supply line 61b, the power supply member 41, the electrode bar 38, power supply Power is supplied to each LED 33 of the heating source 17b through the electrode 51 and the electrode 35, and the LED 33 is caused to emit light.

The light from the LED 33 is directly or once reflected by the reflection layer 59 and then transmitted through the lens layer 20 and further through the

light transmission members

18a and 18b. The electromagnetic radiation due to the recombination of electrons and holes is used for extremely high speed. The wafer W is heated.

Here, when the LED 33 is kept at a normal temperature, the light emission amount of the LED 33 is decreased due to the heat generated by the LED 33 itself. In this embodiment, a cooling medium is passed through the

cooling members

4a and 4b, as shown in FIG. Thus, since LED33 is cooled via the

cooling members

4a and 4b, the heat-diffusion member 50, the support body 32, and the electrode 35, LED33 can be cooled efficiently.

However, even when the LED 33 is cooled in this manner, the LED 33 may be overheated due to excessive current flowing through the LED 33, and the efficiency of the LED 33 may be extremely reduced or the LED 33 may be destroyed. . For example, in the present embodiment, as shown in FIG. 7, a DC voltage is applied to the LED 33 to heat the wafer W, but the power supplied to the LED 33 immediately before the wafer W reaches the maximum temperature ( That is, the LED current increases most, and the temperature of the LED 33 increases most at that time. Therefore, it is necessary to measure the temperature of the LED 33 at this time.

Conventionally, in order to measure the temperature of such an LED 33, the temperature in the vicinity of the LED has been detected by a temperature sensor such as a thermocouple. However, in this case, the temperature cannot be measured with high accuracy, and The timing from when the LED is overheated until the temperature is detected is later than the timing at which failure destruction occurs.

On the other hand, in the present embodiment, the temperature calculation unit 62 receives data related to the IV characteristics of the LED 33 from the power

supply control units

42a and 42b, estimates the temperature based on the data, and based on the estimated temperature, calculates the interface. When the lock unit 63 exceeds the set temperature, a signal for cutting off the power supply from the power supply unit 60 is generated. As a result, the temperature of the LED can be grasped more accurately and quickly than when the temperature of the LED is measured using a temperature sensor, and the interlock can be applied based on this, so that the LED 33 can be appropriately used. Can be prevented from overheating.

The temperature calculation at this time will be specifically described.
The IV characteristics of the LED depend on the IV characteristics at the pn junction and the IV characteristics of the bulk resistance and contact resistance of the LED. Then, the voltage of a single LED, as illustrated in FIG. 8, the voltage of the pn junction and V _D, if the voltage corresponding to the bulk resistance and the resistance of the contact resistance or the like was _{_{V R, V = V D +}} V _R can be represented.

The IV characteristic in the pn junction can be expressed by the following equation (1).

Here, k is a Boltzmann constant, T is an absolute temperature, Eg is a band gap, Is is a reverse leakage current, and q is a charge amount of one electron.
Is can be expressed by the following equation (2). When this is substituted into the above equation (1), V _D is expressed as shown in the following equation (3).

On the other hand, I-V characteristics of the bulk resistance and the contact resistance is expressed by the following equation (4) as an expression representing the V _R.

However, Ea is the activation energy of the impurity level.

Therefore, the entire voltage V can be expressed by the following equation (5).

However, it is difficult to derive the temperature T directly from the equation (5). Therefore, when the slope of the IV characteristic is obtained by differentiating the above equation (5) with the current I, the following equation (6) is obtained.

As can be seen from the equation (6), when I is small, the contribution of the pn junction portion is large, and when I is large, the contribution of the resistance component is large. This can also be understood from FIG. FIG. 9 shows IV characteristics obtained by flowing various values of pulse current to the LED 33 so that the temperature does not rise and actually measuring the voltage at that time, and shows two temperatures of 300K and 420K. FIG. 10 is a graph in which the above equation (5) is fitted to the values shown in FIG. 9 and the IV characteristics in the above equations (3) and (4) are divided into graphs. These are the graphs which expand and show the minute electric current part of FIG. Thus, the constants I ₀ and R ₀ in the formulas (3) and (4) can be obtained by fitting the formula (5) to the actually measured values. From these figures, the slope of the IV characteristic at the pn junction is much larger than the slope of the IV characteristic at the resistance component at a very small current of 4 mA or less, and the slope of the IV characteristic at the resistance component at 200 mA or more. Is much larger than the slope of the IV characteristic in the pn junction.

Utilizing this, (a) a method for obtaining the temperature of the LED 33 from the relationship between the pn junction and the temperature using a low current, and (b) a relationship between the resistance component such as a bulk resistance and the temperature using a large current. Two types of methods of obtaining the temperature of the LED 33 using the above can be adopted.

In the method (a), since the voltage change due to the pn junction is larger than the voltage change due to the resistance at a very small current of 4 mA or less, the resistance component can be ignored for temperature estimation. At this time, the voltage V can be expressed by the following equation (7).

Here, the voltage difference ΔV (= V _H −V _L ) when two different voltage currents (V _H , I _H and V _L , I _L ) are passed at the same temperature is expressed by the following equation (8). Given.

In equation (8), η is an ideal factor, ideally 1, but a value that varies depending on the process and structure.
In the above equation (8), k and q are known, and η is determined by the device structure. Therefore, when (η × k) / q is K, the temperature T is obtained by the following equation (9). Can do.

In the method (b), when the current is 200 mA or more, the slope of the IV characteristic is sufficiently larger for the resistance component than for the pn junction. Can be ignored. At this time, the following expression (10) is established based on the above expression (6).

Here, when two different voltage currents (V _H , I _H and V _L , I _L ) are flown at the same temperature, and V _H −V _L = ΔV and I _H −I _L = ΔI, the above (10) From the equation, the temperature T can be expressed by the following equation (11).

That is, in both cases (a) and (b), the temperature T is obtained by flowing two types of current while heating the LED. This temperature calculation is performed by the temperature calculation unit 62, and when the interlock unit 63 that has received the temperature calculation result detects that the value exceeds a predetermined value, it is determined as abnormal overheating, Power supply from the power supply unit 60 is stopped.

Here, as the measurement of the LED temperature in the actual annealing apparatus 100, the power supply control unit 42a (42b) emits power (current) as shown in FIG. A temperature calculation unit 62 at this time, the time t ₁ and t ₂ minute time in becomes highest near the region set temperature (the encircled area S in FIG.) Δt = t ₂ -t ₁ in FIG. 7 The above two types of current and voltage are measured. The smaller the minute time, the better, but 5 to 100 msec. Since the current value in this case is 200 mA or more based on the data obtained here, the temperature calculation unit 62 calculates the temperature of the LED 33 from the equation (11), and the value exceeds a predetermined value. In this case, the interlock unit 63 applies the interlock.

In the above description, the temperature calculation is performed for only one LED 33, but the temperature can also be calculated for each group of LEDs 33, for example, the LED array 34. In this case, it is considered that m serial LEDs 33 are connected in parallel. Here, assuming that the voltage applied to the LED array 34 is V _mn and the flowing current is I _mn , and all the LEDs 33 are averaged and treated as a uniform element, the voltage applied to each LED 33 is V _mn / m, and the current is I _mn / n. Further, the above two types of voltage / current are V _mnH , I _mnH and V _mnL , I _mnL , respectively, and V _mnH −V _mnL = ΔV _mn and I _mnH −I _mnL = ΔI _mn . Then the temperature calculation formula in the case of small current and a large current flows (9), [Delta] V in _{(11), ΔI, I H} , each _{_{I L ΔV mn / m, ΔI}} mn / n, I mnH / n, I mnL / When n is substituted into these equations, the following equations (9 ′) and (11 ′) are obtained.

Therefore, the temperature for each LED array 34 can be calculated from these equations (9 ′) and (11 ′). In addition, among a large number of LED arrays 34 arranged on the cooling member 42a (42b), the temperature is calculated based on the above at a plurality of locations away from each other, and a more detailed temperature distribution of the entire heating source 17a (17b) is obtained. You can also

In the present embodiment, the temperature calculator 62 determines the current of the LED 33 based on the current-voltage characteristics at the pn junction of the LED 33 or the current-voltage characteristics of the resistance of the LED 33 such as the bulk resistance and contact resistance. When the temperature is calculated and the calculated temperature exceeds a predetermined value, the interlock unit 63 issues a signal to stop power supply. Therefore, the temperature of the LED 33 can be grasped quickly and with high accuracy, and the LED 33 is overheated appropriately. Can be prevented.

Further, since the temperature is estimated by calculation from the current-voltage characteristics when power is supplied to a large number of LEDs 33, the temperature can be grasped as an average value of the large number of LEDs. For this reason, temperature detection can be performed with higher accuracy than when a sensor is provided.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above-described embodiment, the example in which the heat source having the LEDs is provided on both sides of the wafer that is the object to be processed has been described, but the heat source may be provided on either one. Moreover, although the case where LED was used as a light emitting element was shown in the said embodiment, you may use other light emitting elements, such as a semiconductor laser. Furthermore, the object to be processed is not limited to the semiconductor wafer, and other objects such as a glass substrate for FPD can be targeted.

The present invention is suitable for applications that require rapid heating, such as annealing of a semiconductor wafer after impurities are implanted.

Claims

A processing chamber in which an object to be processed is stored;
A heat source provided with a plurality of light emitting elements having a pn junction for irradiating light to the object to be processed, and provided to face at least one surface of the object to be processed;
A power supply for supplying power to the light emitting element of the heating source;
A light transmissive member provided corresponding to the heating source and transmitting light from the light emitting element;
An exhaust mechanism for exhausting the processing chamber;
A temperature calculation unit for calculating a temperature of the light emitting element based on a current-voltage characteristic at a pn junction of the light emitting element or a current-voltage characteristic at a resistance of the light emitting element;
An annealing apparatus comprising: an interlock unit that stops power supply to the power supply unit when the temperature calculated by the temperature calculation unit exceeds a predetermined temperature.
The temperature calculation unit calculates the temperature of the light emitting element by using a current-voltage characteristic at a pn junction of the light emitting element when a current flowing through the light emitting element is a small current of a predetermined value or less. Annealing equipment.
2. The temperature calculation unit according to claim 1, wherein the temperature calculation unit calculates the temperature of the light emitting element based on a current-voltage characteristic of a resistance of the light emitting element when a current flowing through the light emitting element is a large current of a predetermined value or more. Annealing equipment.
The annealing apparatus according to claim 1, wherein the light emitting element is an LED.
An overheating prevention system used in an annealing apparatus that performs an annealing process on a substrate in a processing chamber by a heating source including a plurality of light emitting elements having a pn junction,
A temperature calculation unit for calculating a temperature of the light emitting element based on a current-voltage characteristic at a pn junction of the light emitting element or a current-voltage characteristic at a resistance of the light emitting element;
An overheat prevention system comprising: an interlock unit that stops power supply to the light emitting element when the temperature calculated by the temperature calculation unit exceeds a predetermined temperature.
The temperature calculation unit calculates the temperature of the light emitting element using a current-voltage characteristic at a pn junction of the light emitting element when a current flowing through the light emitting element is a small current of a predetermined value or less. Overheating prevention system.
6. The temperature calculating unit according to claim 5, wherein the temperature of the light emitting element is calculated based on a current-voltage characteristic of the resistance of the light emitting element when a current flowing through the light emitting element is a large current equal to or greater than a predetermined value. Overheat prevention system.
The overheat prevention system according to claim 5, wherein the light emitting element is an LED.