JP2018166204A - Film forming apparatus and film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film forming apparatus capable of accurately controlling temperature of a substrate and therefore allows for improvement in productivity.SOLUTION: The film forming apparatus comprises: a film forming chamber 2 accommodating a substrate W and performing film forming process per substrate; a gas supply unit 3 supplying a gas onto the substrate; a heater 7 heating the substrate; a window 2a provided in the film forming chamber; a radiation thermometer 10 measuring temperature of the substrate through the window; a parameter acquiring unit 12 acquiring a parameter correlated with the temperature of the substrate; a correcting unit correcting temperature of the substrate based on a change from an initial value of the parameter; and a controlling unit 11 controlling the heater based on temperature of the substrate or the temperature of the substrate thus corrected.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a film forming apparatus and a film forming method.

  A film forming apparatus such as a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus is industrially important for forming a thin film on a substrate having a uniform and large area. In such a thin film forming apparatus, since the film quality of the thin film is greatly influenced by the temperature of the substrate during film formation, it is necessary to measure and control the temperature of the substrate during film formation. Regarding the measurement of the temperature of the substrate, a method using a radiation thermometer is widely used among various measurement methods. The radiation thermometer is a method for measuring the intensity of heat radiation from a heated measurement object and obtaining the temperature of the measurement object from the measured heat radiation intensity. The features of temperature measurement with a radiation thermometer are that temperature measurement is possible without contact with the object to be measured, and that the time required for measurement is very short. It is suitably used in a thin film forming apparatus such as an MOCVD apparatus, which normally forms films in different atmospheres and conditions.

  On the other hand, in order to accurately measure the temperature of the measurement object with the radiation thermometer, it is necessary to accurately measure the intensity of heat radiation from the measurement object. Generally, in order to measure the heat radiation light intensity from the measurement object with the film forming apparatus, a light transmission window is provided on the wall surface of the film forming apparatus, and the heat radiation light intensity is measured through this window. In general, an optically transparent member such as quartz is used as a member of the light transmission window.

  On the other hand, when the thin film forming operation is repeatedly executed, deposits gradually adhere to the inner surface of the temperature measuring window member. The adhesion of the deposit causes clouding of the window member. When the window member is clouded, the intensity of heat radiation from the substrate on which the thin film is formed decreases, so that the radiation thermometer cannot accurately measure the substrate temperature via the window member.

  When the error in the temperature measured by the radiation thermometer becomes large, the film forming apparatus cannot form a thin film having a desired film thickness or film quality. Therefore, every time the window member is clouded, it is necessary to open the film forming apparatus that needs to isolate the inside of the apparatus from the atmospheric atmosphere and perform maintenance on the window member. Such maintenance deteriorates the throughput of the film forming process and leads to a decrease in productivity.

Japanese Patent Application Laid-Open No. 2006-066657

  A film forming apparatus capable of accurately controlling the temperature of a substrate and improving productivity.

  The film forming apparatus according to the present embodiment includes a film forming chamber that accommodates a substrate and performs film forming processing for each substrate, a gas supply unit that supplies a gas onto the substrate, a heater that heats the substrate, and a film forming chamber. A provided window, a radiation thermometer that measures the temperature of the substrate through the window, a parameter acquisition unit that acquires a parameter correlated with the temperature of the substrate, and the temperature of the substrate based on a variation from the initial value of the parameter And a control unit that controls the heater based on the substrate temperature or the corrected substrate temperature.

  The correction unit may correct the temperature of the substrate taking into account that the emissivity fluctuates due to the temperature or the optical interference effect caused by the formed thin film.

  The correction unit includes: a first reflected light intensity acquired as a parameter before the first film forming process; and a second reflected light intensity acquired as a parameter before the second film forming process after the first film forming process. Based on this, the temperature of the substrate may be corrected.

  The film forming apparatus further includes an environmental thermometer that measures the environmental temperature of the film forming chamber, and the correction unit includes a first reflected light intensity and a second reflected light intensity measured at substantially the same environmental temperature. , The temperature of the substrate may be corrected.

The correction unit corrects the temperature of the substrate based on the ratio between the first reflected light intensity and the second reflected light intensity.
The correction unit calculates the corrected emissivity by correcting the emissivity based on the ratio between the first reflected light intensity and the second reflected light intensity, and the temperature of the substrate is calculated using the thermal radiation intensity and the corrected emissivity. It may be calculated.

  The correction unit may correct the temperature of the substrate based on the growth rate of a predetermined film formed on the substrate acquired as a parameter.

  The correction unit may correct the temperature of the substrate based on the refractive index of a predetermined film formed on the substrate acquired as a parameter.

  The film forming method according to the present embodiment is a film forming method for supplying a gas onto a substrate while heating the substrate housed in the film forming chamber to a predetermined temperature with a heater, and includes a window provided in the film forming chamber. The temperature of the substrate is measured via a parameter, a parameter correlated with the temperature of the substrate is obtained, the temperature of the substrate is corrected based on a variation from the initial value of the parameter, and the corrected temperature of the substrate is equal to the predetermined temperature. The heater is controlled so that

The figure which shows schematic structure of the film-forming apparatus by 1st Embodiment. Schematic which shows a mode that a radiation thermometer and an optical monitor are measuring the heat radiation light intensity | strength and reflected light intensity | strength through a light transmission window. The figure which shows the measured value of the initial reflected light intensity ratio of the wafer with respect to the frequency | count of the film-forming process. The flowchart which shows an example of operation | movement of the film-forming apparatus by 1st Embodiment. The figure which shows the measured value of the half value width of the diffraction intensity peak of the (102) plane of AlN by the X-ray rocking curve method. The figure which shows the measured value of the time change of the reflectance in the film-forming of AlN and AlGaN. The figure which shows the measured value of the growth rate ratio of GaN. The flowchart which shows operation | movement of the film-forming apparatus by 2nd Embodiment. The figure which shows the example of the measurement point of the environmental temperature of a chamber.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment does not limit the present invention. FIG. 1 is a diagram showing a schematic configuration of a film forming apparatus 1 according to the first embodiment. In the present embodiment, a silicon substrate, specifically a silicon wafer (hereinafter simply referred to as a wafer) W, is used as a substrate for film formation, and a single film or a plurality of thin films are stacked on the wafer W. An example of film formation will be described. Hereinafter, MOCVD is specifically described as an example of the vapor phase growth method.

  A film forming apparatus 1 in FIG. 1 includes a chamber 2 that forms a film on a wafer W, a gas supply unit 3 that supplies a raw material gas to the wafer W in the chamber 2, and a raw material discharge unit 4 that is positioned above the chamber 2 A susceptor 5 that supports the wafer W in the chamber 2, a rotating unit 6 that rotates while holding the susceptor 5, a heater 7 that heats the wafer W, and a gas discharge unit 8 that discharges the gas in the chamber 2. An exhaust mechanism 9 that exhausts gas from the gas exhaust unit 8, a radiation thermometer 10 that measures the temperature of the wafer W, a control unit 11 that controls each unit, and an optical that measures the intensity of reflected light from the wafer W And a monitor 12.

  The chamber 2 as the film forming chamber has a shape (for example, a cylindrical shape) that can store the wafer W to be formed, and the susceptor 5, the heater 7, a part of the rotating unit 6, etc. are accommodated in the chamber 2. Has been.

  The gas supply unit 3 includes a plurality of gas storage units 3a that individually store a plurality of gases, a plurality of gas pipes 3b that connect the gas storage units 3a and the material discharge unit 4, and a gas that flows through the gas pipes 3b. And a plurality of gas valves 3c for adjusting the flow rate of the gas. Each gas valve 3c is connected to a corresponding gas pipe 3b. The plurality of gas valves 3 c are controlled by the control unit 11. The actual piping can take a plurality of configurations such as coupling a plurality of gas pipes, branching one gas pipe into a plurality of gas pipes, or combining the branching and coupling of gas pipes.

  The source gas supplied from the gas supply unit 3 is released into the chamber 2 through the source release unit 4. The source gas (process gas) released into the chamber 2 is supplied onto the wafer W, whereby a desired film is formed on the wafer W. In addition, the kind of source gas to be used is not specifically limited.

  A shower plate 4 a is provided on the bottom surface side of the raw material discharge portion 4. The shower plate 4a can be configured using a metal material such as stainless steel or an aluminum alloy. Gases from the plurality of gas pipes 3b are mixed in the raw material discharge section 4 and supplied into the chamber 2 through the gas outlet 4b of the shower plate 4a. Note that a plurality of gas flow paths may be provided in the shower plate 4a, and a plurality of types of gases may be supplied to the wafer W in the chamber 2 while being separated.

  The structure of the raw material discharge portion 4 should be selected in consideration of the uniformity of the formed film, the raw material efficiency, the reproducibility, the manufacturing cost, etc., but is not particularly limited as long as these requirements are satisfied. The thing of a well-known structure can also be used suitably.

  The susceptor 5 is provided in the upper part of the rotating unit 6 and has a structure in which the wafer W is placed and supported in a spot facing provided on the inner peripheral side of the susceptor 5. In the example of FIG. 1, the susceptor 5 has an annular shape having an opening at the center thereof, but may have a substantially flat plate shape without an opening.

  The heater 7 is a heating unit that heats the susceptor 5 and / or the wafer W. There is no particular limitation as long as it satisfies requirements such as the ability to heat the object to be heated to a desired temperature and temperature distribution, and durability. Specific examples include resistance heating, lamp heating, and induction heating.

  The exhaust mechanism 9 exhausts the reacted raw material gas from the inside of the chamber 2 through the gas exhaust unit 8, and controls the inside of the chamber 2 to a desired pressure by the action of the exhaust valve 9b and the vacuum pump 9c.

  The radiation thermometer 10 is provided on the upper surface of the raw material discharge unit 4. The radiation thermometer 10 measures the temperature of the wafer W. The wavelength range of the heat radiation measured by the radiation thermometer 10 is the wavelength range from the visible part to the near-infrared part, and the wafer W is transparent in the above wavelength range such as sapphire and silicon carbide (SiC) (hereinafter referred to as transparent substrate). In this case, since the radiation thermometer cannot directly measure the temperature of the wafer W, it is common to measure the temperature of the susceptor 5 using the intensity of heat radiation from the susceptor 5 that has passed through the transparent substrate. The temperature of the wafer W can be monitored by the temperature of the susceptor 5 measured in this way. In the present embodiment, the substrate is a wafer W that is opaque in the wavelength range measured by the radiation thermometer. However, even if the wafer W is a transparent substrate, the method of correcting the influence of clouding of the light transmission window, which will be described in detail below, can be similarly performed for the temperature of the susceptor 5.

  The radiation thermometer 10 receives thermal radiation from the wafer W and measures the thermal radiation intensity. The radiation thermometer 10 calculates the temperature of the wafer W using the heat radiation light intensity. The radiation thermometer 10 has a data calculation unit therein. This data calculation unit obtains the temperature of the wafer W from the heat radiation intensity. The data calculation unit can be configured by a general-purpose computer, for example. The measured temperature of the wafer W in the radiation thermometer 10 is fed back to the control unit 11 and used to control the actual temperature of the wafer W to a predetermined temperature.

  A light transmission window 2 a is provided on the upper surface of the raw material discharge portion 4, and light from the light source of the optical monitor 12, reflected light from the wafer W, and heat radiation light pass through the light transmission window 2 a. The light transmission window 2a can take an arbitrary shape such as a slit shape, a rectangular shape, or a circular shape. A transparent member is used for the window in the wavelength range of light measured by a radiation thermometer. When measuring a temperature from room temperature to about 1500 ° C., it is preferable to measure the wavelength of light from the visible region to the near-infrared region, in which case quartz glass or the like is suitably used as the window member.

  The control unit 11 includes a computer that centrally controls each unit in the film forming apparatus 1 and a storage unit that stores film forming process information and various programs related to the film forming process. The control unit 11 controls the rotation mechanism, the exhaust mechanism 9 and the like of the gas supply unit 3 and the rotation unit 6 based on the film forming process information and various programs, and controls the heating of the wafer W by the heater 7. For example, the control unit 11 controls the heater 7 so that the measurement temperature of the wafer W measured by the radiation thermometer 10 becomes a predetermined temperature.

  When the wafer W is heated to a high temperature, the chamber 2, the material discharge unit 4, the gas discharge unit 8, and the like may be cooled. When the upstream side of the wafer W such as the raw material discharge part 4 becomes higher than necessary, a gas phase reaction such as pre-decomposition of the raw material, which is undesirable for film formation on the wafer W, occurs in the part where the temperature is higher than necessary. . Further, impurities are released into the raw material gas from a portion where the temperature is higher than necessary, and the film formed on the wafer W contains many impurities. In order to prevent the above undesirable gas phase reaction from occurring, it is preferable to maintain the temperature upstream of the wafer W at room temperature or higher and 250 ° C. or lower. More preferably, it is 60 degreeC or more and 200 degrees C or less.

  Further, if the temperature of a portion such as the chamber 2 that separates the reaction chamber from the atmosphere becomes higher than necessary, there is a risk that a burn may occur if the human body touches this portion. In order to avoid such a risk, it is preferable to keep the portion exposed to the atmosphere at 100 ° C. or lower.

  As for the above-described method for controlling the temperature, it is general that an appropriate flow path is provided in a portion where the temperature needs to be controlled, and the refrigerant is caused to flow inside the flow path. About said refrigerant | coolant, the solution with the liquid which melt | dissolves in water or water, the liquid of an organic material, or an inorganic material can be used. Use of these refrigerants for temperature control with the temperature kept constant is effective for film formation with good reproducibility.

Similar to the radiation thermometer 10, the optical monitor 12 is provided on the upper surface of the raw material discharge unit 4.
The optical monitor 12 may be provided apart from the radiation thermometer 10, but is preferably provided at a position close to the radiation thermometer 10.

  Further, in the film forming apparatus 1 shown in FIG. 1, the optical monitor 12 and the radiation thermometer 10 are provided on the opposite side with respect to the rotation axis of the wafer so that the distance from the rotation axis of the wafer W is substantially the same. More preferred. When clouding occurs unevenly in the light transmission window 2a, the film forming apparatus 1 shown in FIG. 1 is substantially rotationally symmetric with respect to the rotation axis of the wafer W, so that the clouding of the light transmission window 2a is also approximately the rotation of the wafer W. It occurs symmetrically about the axis. Therefore, by installing the optical monitor 12 and the radiation thermometer 10 in the arrangement as described above, the optical monitor 12 and the radiation thermometer 10 can be arranged at a position where the degree of cloudiness is substantially equal. The influence of the non-uniformity of the cloudiness of 2a can be reduced. Even when a plurality of radiation thermometers 10 and a plurality of optical monitors 12 are installed, by installing the radiation thermometer 10 and the optical monitor 12 at a position substantially symmetrical with respect to the rotation axis of the wafer W, The influence of the non-uniformity of the cloudiness of the light transmission window 2a can be reduced, and each radiation thermometer 10 can have the effect of this embodiment.

  More preferably, the optical axis through which heat radiation passes from the wafer W to the radiation thermometer 10 and the optical axis of the optical monitor 12 are matched. By matching the optical axis of the optical monitor 12 and the radiation thermometer 10, the optical monitor 12 can directly evaluate the region of the light transmission window 2 a that affects the measurement of the thermal radiation light intensity of the radiation thermometer 10. become. This arrangement can be suitably used even when the non-uniformity of the cloud of the light transmission window 2a has no symmetry. In order to make the optical axes of the optical monitor 12 and the radiation thermometer 10 coincide with each other, optical components such as a light source and a half mirror of the optical monitor 12 may be appropriately combined.

  When a transparent substrate is used, the radiation thermometer 10 may be provided on the susceptor.

  The optical monitor 12 as a parameter acquisition unit irradiates the wafer W with light through the light transmission window 2a, and measures the reflected light intensity from the wafer W as a parameter through the light transmission window 2a. The optical monitor 12 is installed, for example, above the central portion and / or the outer peripheral portion of the wafer W or thin film, and measures the reflected light intensity of the corresponding wafer W portion. The reflected light intensity is used to correct the measured value of the temperature of the wafer W calculated by the radiation thermometer 10. Correction of the measured value of the temperature of the wafer W will be described later.

  By the way, when the film forming apparatus 1 repeatedly performs film formation, clouding occurs in the light transmission window 2a due to the deposit, and thus the transmittance Tr of the light transmission window 2a is reduced.

  As the transmittance Tr decreases, the reflected light intensity measured by the optical monitor 12 and the heat radiation intensity measured by the radiation thermometer 10 are decreased. For example, the transmittance Tr of the light transmission window 2a before clouding is 1, but when clouding occurs, the transmittance Tr of the light transmission window 2a is reduced to a value smaller than 1 and approaches zero. That is, the transmittance Tr of the light transmission window 2a can vary within a range of 1 to 0 (0 ≦ Tr ≦ 1) depending on the deposits attached to the light transmission window 2a.

  Here, the transmittance of the light transmission window 2a is affected by reflection on the surface of the window member, light absorption and scattering of the window member. However, in the following discussion, these effects are ignored and the transmittance in a state where the light transmission window 2a is not cloudy is set to 1, but there is no problem in the effectiveness of this embodiment. This is because in the present embodiment, the influence of the clouding of the light transmission window 2a is expressed as a comparison with a state without clouding. In order to eliminate the influence of the actual transmittance of the light transmission window 2a when there is no cloudiness, the radiation thermometer 10 is corrected in advance using a temperature measurement method that is not affected by the transmittance of the light transmission window 2a. Need to do. As a temperature measuring method that is not affected by the transmittance of the light transmitting window 2a, a method of melting a material whose melting point is known, a method using a two-color radiation thermometer, a thermal radiation spectrum is measured, and black body radiation is measured. The method of fitting with the formula of is mentioned. Of the above methods, the method using a two-color radiation thermometer and the method of measuring the thermal radiation spectrum are methods for obtaining the temperature of the measurement object from the wavelength distribution of the thermal radiation light intensity, and in principle the transmission through the light transmission window 2a. Unaffected by rate. On the other hand, it is known that when a thin film is grown on a substrate, the reflectance has a large wavelength distribution due to the light interference effect. Therefore, with the two-color radiation thermometer and the method of measuring and analyzing the thermal radiation spectrum, it is difficult to measure the temperature during the thin film deposition, and the measurement wavelength is narrowly limited for the temperature measurement during the thin film deposition. It is necessary to use a radiation thermometer.

  The temperature error of the wafer W will be described in detail with reference to FIG.

  FIG. 2 is a schematic view showing a state in which the radiation thermometer 10 and the optical monitor 12 measure the heat radiation light intensity and the reflected light intensity through the light transmission window 2a. In FIG. 2, one radiation thermometer 10 and one optical monitor 12 are shown. However, the plurality of radiation thermometers 10 and the plurality of optical monitors 12 correspond to the central portion, the outer peripheral portion, and the like of the wafer W. It may be provided.

  When the radiation thermometer 10 measures the temperature of the wafer W, the heat radiation light L1 passes through the light transmission window 2a once. When deposits adhere to the light transmission window 2a by the film forming apparatus 1 performing a film forming operation, the transmittance Tr of the light transmission window 2a becomes smaller than 1. In this case, the light L1 is multiplied by Tr every time it passes through the light transmission window 2a. Therefore, the heat radiation light intensity measured by the radiation thermometer 10 is not clouded in the light transmission window 2a (Tr = 1). In the case of (2)). In such a case, the radiation thermometer 10 cannot measure the accurate temperature of the wafer W. The temperature measured by the radiation thermometer 10 is fed back to the control unit 11 and used to control the actual temperature of the wafer W. Therefore, the error in the measured temperature causes an error in the actual temperature of the wafer W.

  Therefore, according to the present embodiment, the optical monitor 12 as the parameter acquisition unit measures the first initial reflected light intensity before the first film forming process as the first film forming process, and after the first film forming process. The second initial reflected light intensity is measured before the second film forming process. The optical monitor 12 calculates the ratio of the first initial reflected light intensity and the second initial reflected light intensity as the initial reflected light intensity ratio of the wafer W, and transmits light from the initial reflected light intensity that decreases due to clouding of the light transmitting window 2a. The transmittance Tr of the window 2a is obtained. And the film-forming apparatus 1 correct | amends an emissivity or measurement temperature using the transmittance | permeability Tr. The initial reflected light intensity is the reflected light intensity of the wafer W before the film forming process measured by the optical monitor 12 in the film forming process of each wafer W. That is, the initial reflected light intensity of the wafer W is the reflected light intensity measured through the light transmission window 2a after the wafer W is loaded into the chamber 2 in each film forming process and before the film forming process of the wafer W. is there.

  FIG. 3 is a diagram showing measured values of the initial reflected light intensity ratio of the wafer W with respect to the number of film forming processes. The horizontal axis indicates the number of film forming processes, and the vertical axis indicates the initial reflected light intensity ratio. The data of FIG. 3 is obtained from an arrangement in which three chambers 2 are installed in one film forming apparatus and these chambers 2 are processed in parallel. In FIG. 3, PM1 to PM3 indicate three chambers 2 included in the film forming apparatus.

  The initial reflected light intensity ratio is the initial reflected light intensity (first initial reflected light intensity) Ir1 measured before a certain film forming process (first film forming process) and the second composition after the first film forming process. It is a ratio (Ir2 / Ir1) with the initial reflected light intensity (second initial reflected light intensity) Ir2 measured before the film treatment. When the number of film forming processes is 0, the initial reflected light intensity ratio is the ratio of the first initial reflected light intensity Ir1 to the first initial reflected light intensity Ir1 (Ir1 / Ir1 = 1).

  The first initial reflected light intensity Ir1 is the initial reflected light intensity measured through, for example, a new (immediately after replacement) light transmission window 2a before the first film formation process. That is, the first initial reflected light intensity Ir1 is the initial reflected light intensity measured after the light transmission window 2a is replaced and before the first film formation processing of the wafer W. The second initial reflected light intensity Ir2 is the initial reflected light intensity measured before the execution of any film forming process after the second time. That is, the second initial reflected light intensity Ir2 is the initial reflected light intensity measured after the light transmission window 2a is replaced and before the second and subsequent film forming processes of the wafer W. It should be noted that the first initial reflected light intensity Ir1 may be measured after several film formation processes if the light transmission window 2a is not clouded. In this case, the second initial reflected light intensity Ir2 is a reflected light intensity measured before any film forming process after the first initial reflected light intensity Ir1.

  When the number of film forming processes is 0, the initial reflected light intensity ratio is the ratio (Ir1 / Ir1 = 1) between the first initial reflected light intensity Ir1 and the first initial reflected light intensity Ir1, as described above. When the number of film forming processes is 1 or more, the initial reflected light intensity ratio (Ir2 / Ir1) tends to decrease as the number of film forming processes increases.

  Thus, since the transmittance Tr of the light transmission window 2a correlates with the initial reflected light intensity ratio, the radiation thermometer 10 or the optical monitor 12 according to the present embodiment can transmit the transmittance based on the initial reflected light intensity ratio. Tr can be calculated. The radiation thermometer 10 or the control unit 11 corrects the emissivity or the measured temperature using the transmittance Tr.

  Hereinafter, calculation of transmittance Tr and correction of emissivity or measurement temperature will be described in more detail.

(Calculation of transmittance Tr of light transmission window 2a)
Please refer to FIG. 2 again. When the optical monitor 12 measures the reflected light intensity, the light L2 from the optical monitor 12 passes through the light transmission window 2a having the transmittance Tr, is reflected by the wafer W, and passes through the light transmission window 2a again. Return to the optical monitor 12. Therefore, in order for the optical monitor 12 to measure the reflected light intensity, the light L2 reciprocates between the optical monitor 12 and the wafer W and passes through the light transmission window 2a twice. Here, as described above, each time the light passes through the light transmission window 2a, it becomes Tr times. Therefore, the intensity (reflected light intensity) of the light L2 measured by the optical monitor 12 is applied to the light transmission window 2a. compared with the case where there is no cloudiness (Tr) is ^doubled. If the transmittance Tr of the light transmission window 2a is smaller than 1 by the film forming apparatus 1 performing the film forming operation, the intensity of the reflected light measured by the optical monitor 12 must be changed accordingly. if ^(Tr) will be reduced ^twice.

Here, in general, the reflectance R and emissivity ε of a substance have the relationship of Equation 1. It is assumed that the transmittance of this substance is zero (opaque).
ε + R = 1 (Formula 1)
The emissivity ε of the wafer W during film formation can be obtained from the reflectance R using Equation 1. When the thin film is formed on the wafer W, the emissivity ε may change greatly. However, since the emissivity ε during film formation can be evaluated by measuring the reflectance R according to Equation 1, Accurate temperature measurement becomes possible. In general, the reflectance of a material is predetermined as a value unique to the material. For example, in the case of silicon, the reflectivity R in the vertical direction of the wafer is about 0.3 at room temperature for light having a wavelength in the vicinity of 1 μm. Therefore, before the growth is started, the reflected light intensity is measured using a material having a known reflectance such as the wafer W, and the relationship between the reflected light intensity and the reflectance can be calibrated by the known reflectance.

At this time, the film forming apparatus 1 can obtain the transmittance Tr of the light transmission window 2a from the measured value of the initial reflected light intensity of the wafer W. For example, if the light transmission window 2a is cloudy, the transmittance Tr becomes smaller than 1, and accordingly, the initial reflected light intensity measured by the optical monitor 12 decreases to (Tr) ² times. The optical monitor 12 can calculate the transmittance Tr of the light transmission window 2a by calculating (a decrease rate of the initial reflected light intensity) ^1/2 .

In the present embodiment, the transmittance of the new light transmission window 2a immediately after replacement is assumed to be 1, and the first initial reflected light intensity Ir1 is used as the denominator. Therefore, if the initial reflected light intensity measured before the second growth process is Ir2, the transmittance Tr is calculated as (Ir2 / Ir1) ^1/2 .

  Some points to note here are listed below. First, when obtaining the above-mentioned transmittance Tr, it is not always necessary to measure the initial reflected light intensity of each wafer to be subjected to the film formation process in advance. That is, the transmittance Tr of the light transmission window 2a may be obtained periodically using a measurement wafer (standard sample wafer) made of the same material and having the same optical properties. However, when the film is frequently formed using the same type of wafer, it is preferable to periodically measure the transmittance using the wafer to be subjected to the film forming process. In this case, there is no need to replace the standard sample wafer and the film formation target wafer, and productivity is not impaired.

  Next, even if the material is the same, the reflectance of the material may be different. For example, the reflectivity of a material generally depends on temperature, and when the material is crystalline, it may depend on the plane orientation, polarization direction, and the like. When measuring the initial reflected light intensity for measuring the transmittance, it is necessary to make the elements that affect the above-described reflectance the same.

  In general, in order to increase the productivity of film formation, it is necessary to take out the wafer W after the film formation process from the chamber 2 at an early stage during the temperature drop. For this reason, when a new wafer W is carried into the chamber 2, the temperature inside the chamber 2 is not sufficiently lowered, and the temperature of the wafer W newly carried into the chamber 2 is lowered with time. Become. The initial reflected light intensity measured in such a situation is still not stable, and it is necessary to pay close attention when measuring the initial reflected light intensity.

  Specifically, as a method for accurately measuring the initial reflected light intensity, the ambient temperature in the chamber 2 is measured, and the temperature in the chamber 2 when measuring the initial reflected light intensity is the same for each measurement. Or the same process from the end of the film formation process to the measurement of the initial reflected light intensity performed before the next film formation.

  FIG. 9 shows an example of measurement points of the environmental temperature of the chamber 2 described above. Examples of the environmental temperature of the chamber 2 include temperatures (T21 and T41) on the outlet side of the refrigerant that cools the chamber 2 or the raw material discharge unit 4. Moreover, as said environmental temperature, temperature T81 of the exhaust gas in the gas exhaust part 8 is mentioned. Moreover, as said environmental temperature, the temperature (T22 and T82) of the wall surface of the chamber 2 or the gas exhaust part 8 is mentioned. The temperature of the wall surface is the atmospheric side wall surface or the inner wall portion of the film forming apparatus 1. Moreover, as said environmental temperature, the gas temperature of the lower part 61 inside the chamber 2 can be mentioned. The lower part 61 inside the chamber 2 is inside the rotating part 6 below the heater 7. The difference between the gas temperature of the lower part 61 inside the chamber 2 and the wafer W increases as the distance from the heater 7 increases. Therefore, if the measurement point at the lower part 61 is too far from the heater 7, the relationship between the gas temperature and the temperature of the wafer W is It is not clear. The temperature difference between the gas temperature in the lower portion 61 of the chamber 2 and the wafer W depends on the gas flow rate flowing inside the rotating unit 6 or the heater 7 and its peripheral structure. However, if the linear distance from the heater 7 to the measurement point is approximately within 30 cm, the correlation between the gas temperature of the lower portion 61 of the chamber 2 and the temperature of the wafer W becomes clear, and is suitable as the environmental temperature of the chamber 2 of the present embodiment. Can be used. The ambient temperature can be easily measured with a thermocouple, a resistance thermometer, or the like.

  With respect to making the above processes the same, it is important that the film forming process immediately before newly loading a wafer W is completed under the same conditions every time. Examples of the conditions at the end of the film forming process include the temperature of the wafer W, the type of atmospheric gas, the flow rate, the pressure, the rotational speed of the wafer W, and the power applied to the heater 7. In the case where these conditions are the same, the time elapses for carrying out and carrying in the wafer W may be made the same, and the time from when the newly loaded wafer W is carried in until the initial reflected light intensity is measured may be made the same. Can be mentioned. If the conditions at the end of the film formation process are different from normal, the initial reflected light intensity of the wafer W newly loaded after that may not be measured accurately. In that case, after the film formation process with an end condition different from normal is completed, a dummy run with the same film formation process end condition is processed separately, and then a new wafer W is carried in, so that the initial reflected light Intensity may be measured.

  Furthermore, the light source for measuring the initial reflected light intensity needs to be stable over a long period of time. If the irradiation light intensity is not stable in the wavelength region where the initial reflected light intensity measurement of the light source is performed, the reflected light intensity cannot be obtained accurately, and the transmittance of the window member of the light transmission window 2a is accurately obtained. I can't. Therefore, the light source needs to feed back the light emission intensity to the drive circuit of the light source to realize a stable light emission intensity for a long time. Alternatively, the emission intensity may be output to the optical monitor 12 to correct the reflected light intensity. Further, when a semiconductor light emitting element such as a light emitting diode is used as a light source, a stable light emission intensity can be obtained by driving the light emitting element with a driving power source capable of supplying a stable driving current. When driving a light emitting element with a constant current, it should be noted that the temperature of the light emitting element itself is stable and that a sufficient time for stabilizing the light emission intensity is provided after the light emitting element is driven. It is.

  Moreover, it is preferable that the wavelength of the reflected light measured by the optical monitor 12 and the wavelength of the heat radiation light intensity measured by the radiation thermometer 10 are as close as possible. This is because the cloud generated in the light transmission window 2a may show different transmittance depending on the wavelength. Such a problem can be eliminated by bringing the wavelength of the light measured by the optical monitor 12 close to the wavelength of the heat radiation light measured by the radiation thermometer 10.

(Correction of measurement temperature of wafer W)
On the other hand, assuming that the intensity of thermal radiation with a wavelength λ (μm) emitted from a substance having a temperature of T (K) and an emissivity of ε is L, the thermal radiation intensity L can be calculated by the Planck's equation shown in Equation 2. expressed.
Note that c1 and c2 are constants. The constant c2 is about 14388 K · μm.

As an example, the temperature T of the wafer W during film formation is about 1000 ° C. to about 1500 ° C., and the measurement wavelength λ of the heat radiation light is 1 μm, for example. In this case, since the first term of the denominator is sufficiently larger than 1, “−1” of the second term of the denominator on the right side of Equation 2 may be ignored. That is, the radiation thermometer 10 may obtain the temperature T of the wafer W using Equation 3. The radiation thermometer 10 can calculate the temperature T of the wafer W from Expression 3 using the values of emissivity ε, thermal radiation light intensity (observed value) L, and wavelength λ.

  Here, when there is no cloudiness in the light transmission window 2a and the transmittance Tr of the light transmission window 2a is 1, the temperature T calculated by the radiation thermometer 10 is a substantially accurate temperature of the wafer W. On the other hand, when the light transmission window 2a is cloudy and the transmittance Tr is smaller than 1, the thermal radiation light intensity L decreases, so the temperature T calculated by the radiation thermometer 10 is lower than the actual wafer temperature. The temperature includes an error (hereinafter, apparent temperature).

  Assuming that the actual temperature of the wafer W (hereinafter, actual temperature) is Ta, in order to calculate the actual temperature Ta from the measured value L of the thermal radiation intensity, the preset emissivity ε is corrected by correcting the preset emissivity εc. It is necessary to. That is, the actual temperature Ta can be calculated by using the measured value L of the heat radiation intensity and the corrected emissivity εc. For this purpose, there is a method (method 1) in which the corrected emissivity εc is obtained from the transmittance Tr of the light transmission window 2a and the actual temperature Ta is calculated using the corrected emissivity εc. There is also a method (method 2) for directly calculating the actual temperature Ta from the transmittance Tr.

Method 1 utilizes the fact that εc / ε is equal to the transmittance Tr of the light transmission window 2a. The radiation thermometer 10 corrects ε in Equation 3 to εc (ie, ε × Tr), and substitutes ε × Tr into ε in Equation 3. The temperature T thus calculated becomes the actual temperature Ta. Therefore, Equation 4 is obtained.
After correcting the emissivity ε, the radiation thermometer 10 calculates Equation 4 using the measured value L of the thermal radiation intensity.
Thereby, the radiation thermometer 10 can obtain the actual temperature Ta of the wafer W. That is, in the method 1, the radiation thermometer 10 may correct the emissivity ε to the corrected emissivity εc and obtain the temperature of the wafer W from the measured value L of the heat radiation intensity as usual. Thereby, the radiation thermometer 10 can obtain the actual temperature Ta of the wafer W. In this case, since the radiation thermometer 10 outputs the actual temperature Ta of the wafer W as the measurement temperature, the control unit 11 may control the heater 7 based on the measurement temperature from the radiation thermometer 10.

In Method 2, the heat radiation intensity L obtained by substituting the corrected emissivity εc and the actual temperature Ta into Equation 3 is the heat radiation intensity L obtained by substituting the original emissivity ε and the apparent temperature T into Equation 3. Take advantage of being equal to That is, the fact that Formula 5 holds is used.
Solving Equation 5 gives Equation 6.
Since εc / ε is equal to the transmittance Tr of the light transmission window 2a, Expression 6 is expressed as Expression 7.
The radiation thermometer 10 can calculate the actual temperature Ta from the transmittance Tr of the light transmission window 2a and the measured value L of the heat radiation intensity obtained through the light transmission window 2a using Equation 7. In this case, the radiation thermometer 10 may calculate Equation 7 and output the actual temperature Ta of the wafer W. However, the radiation thermometer 10 may output the apparent temperature T of the wafer W, and the control unit 11 may calculate the actual temperature Ta of the wafer W by calculating Equation 7.

  The film forming apparatus 1 can control the heater 7 based on the accurate temperature of the wafer W by using either the method 1 or the method 2.

  For example, when the transmittance Tr of the light transmission window 2a is 95%, the wavelength λ of the heat radiation light is 0.95 μm, and the apparent temperature T is 1273 K (1000 ° C.), the actual temperature Ta of the wafer W is 1278K (1005 ° C.). Such an error between the apparent temperature T and the actual temperature Ta is caused by determining that the temperature of the wafer W is 5 ° C. lower than the predetermined temperature (1000 ° C.) due to a decrease in the transmittance Tr of the light transmission window 2a.

  If the radiation thermometer 10 outputs the apparent temperature T and the control unit 11 controls the heater 7 using the apparent temperature T, the control unit 11 controls the temperature of the wafer W with respect to the set temperature 1000 ° C. The heater 7 is controlled to 1005 ° C.

  On the other hand, according to the present embodiment, the radiation thermometer 10 outputs the actual temperature Ta calculated using the corrected emissivity εc or the actual temperature Ta corrected by the transmittance Tr. Thereby, the control part 11 can control the heater 7 using the actual temperature Ta. Therefore, for example, the control unit 11 can control the heater 7 so that the temperature of the wafer W becomes 1000 ° C. with respect to the set temperature 1000 ° C. Alternatively, the control unit 11 may calculate the actual temperature Ta corrected by the transmittance Tr, and control the heater 7 using the actual temperature Ta. As described above, the film forming apparatus 1 according to the present embodiment can accurately control the temperature of the wafer W even if the transmittance Tr of the light transmission window 2a is lowered. As a result, a maintenance cycle such as replacement of the light transmission window 2a can be lengthened, and productivity can be improved.

  Next, the operation of the film forming apparatus 1 according to the present embodiment will be described.

  FIG. 4 is a flowchart showing an example of the operation of the film forming apparatus 1 according to the present embodiment. First, the optical monitor 12 measures the first initial reflected light intensity Ir1 before the first film forming process as the first film forming process (S10). The first film forming process is, for example, the first film forming process of the wafer W after the replacement of the light transmission window 2a. The optical monitor 12 outputs the measured first initial reflected light intensity Ir1 to the radiation thermometer 10. The radiation thermometer 10 stores the first initial reflected light intensity Ir1 in an internal memory (not shown). In the first film formation process, it is assumed that the light transmission window 2a is not cloudy and the transmittance Tr of the light transmission window 2a is 1 (Ir1 / Ir1 = 1). Therefore, the radiation thermometer 10 outputs the emissivity ε and the apparent temperature T without substantially correcting. At this time, the control unit 11 controls the heater 7 based on the measured temperature from the radiation thermometer 10.

  After the completion of the first film forming process, the film forming apparatus 1 unloads the wafer W after the film forming process, and then loads the second wafer W for executing the film forming process (S20). The optical monitor 12 measures the second initial reflected light intensity Ir2 before the second film formation process (S30). The optical monitor 12 outputs the second initial reflected light intensity Ir2 measured before the second film formation process to the radiation thermometer 10. The radiation thermometer 10 stores the second initial reflected light intensity Ir2 in the internal memory.

  Further, before the film forming process, the radiation thermometer 10 calculates a ratio of the second initial reflected light intensity Ir2 to the first initial reflected light intensity Ir1 (initial reflected light intensity ratio = Ir2 / Ir1) (S40).

Next, as described above, the radiation thermometer 10 calculates the transmittance Tr of the light transmission window 2a from the initial reflected light intensity ratio, and multiplies the transmittance Tr of the wafer W by the transmittance Tr, thereby emissivity of the wafer W. ε is corrected (S50). For example, the transmittance Tr is the square root of the initial reflected light intensity ratio (Ir2 / Ir1) ^1/2 . As a result, the radiation thermometer 10 can calculate the corrected emissivity εc (εc = ε × Tr) using the method 1 and calculate the actual temperature Ta of the wafer W.

  Alternatively, the control unit 11 can calculate the actual temperature Ta of the wafer W from the transmittance Tr using the method 2.

  When the method 2 is used, the optical monitor 12 may output the first and second initial reflected light intensities Ir1 and Ir2 to the control unit 11. In this case, the control unit 11 stores the first and second initial reflected light intensities Ir1 and Ir2 in an internal memory (not shown), and calculates the initial reflected light intensity ratio (S40). The control unit 11 calculates the transmittance Tr from the initial reflected light intensity ratio, and corrects the measured temperature (apparent temperature) measured by the radiation thermometer 10 to the actual temperature Ta using the transmittance Tr (S50). The control unit 11 controls the heater 7 based on the corrected actual temperature Ta.

  The third and subsequent film forming processes are executed in the same manner as the second film forming process. The initial reflected light intensity measured before the third and subsequent film formation processes is also referred to as a second initial reflected light intensity Ir2 for convenience. That is, after completion of each film forming process, the film forming apparatus 1 unloads the wafer W after the film forming process, and then loads the wafer W to be subjected to the film forming process (S20). The optical monitor 12 measures the second initial reflected light intensity Ir2 before each film forming process (S30). The optical monitor 12 outputs the second initial reflected light intensity Ir2 measured before each film forming process to the radiation thermometer 10. The radiation thermometer 10 also stores the second initial reflected light intensity Ir2 before the third and subsequent film formation processes in the internal memory.

  Next, before each film forming process, the radiation thermometer 10 calculates the ratio of the second initial reflected light intensity Ir2 to the first initial reflected light intensity Ir1 (initial reflected light intensity ratio = Ir2 / Ir1) (S40). ).

  Next, the radiation thermometer 10 calculates the transmittance Tr of the light transmission window 2a from the initial reflected light intensity ratio, and corrects the emissivity ε of the wafer W by multiplying the emissivity ε of the wafer W by the transmittance Tr. (S50). Thereby, the radiation thermometer 10 calculates the corrected emissivity εc (εc = ε × Tr) using the method 1, and calculates the actual temperature Ta of the wafer W. Alternatively, the radiation thermometer 10 uses method 2 to calculate the actual temperature Ta of the wafer W from the transmittance Tr (S50). The control unit 11 controls the heater 7 based on the calculated actual temperature Ta.

  Based on the initial reflected light intensity ratio, the controller 11 may warn the user that there is a problem with the clouding of the light transmission window 2a. For example, the control unit 11 determines whether or not the initial reflected light intensity ratio has become a predetermined value or less (S60). When the number of times of film formation is small and the initial reflected light intensity ratio is larger than the predetermined value (NO in S60), the film forming apparatus 1 performs steps S20 to S50 again after the film formation is completed. On the other hand, when the initial reflected light intensity ratio is equal to or less than the predetermined value (YES in S60), the film forming apparatus 1 notifies the user that there is a problem with the clouding of the light transmission window 2a after the film formation ends (S70). ). The notification to the user may be output to a monitor (not shown) or an alarm sound may be sounded by a speaker (not shown).

  As described above, the film forming apparatus 1 according to the present embodiment measures the initial reflected light intensity of the wafer W and calculates the initial reflected light intensity ratio, thereby correcting the emissivity or measuring temperature. Thereby, the film forming apparatus 1 can measure the accurate temperature of the wafer W even when the light transmission window 2a is cloudy.

  FIG. 5 is a diagram showing measured values of the half-value width of the diffraction intensity peak of the (102) plane of AlN by the X-ray rocking curve method. The data shown in FIG. 5 is measurement data for a sample formed by a run corresponding to the 82nd run in terms of the number of runs (number of treatments) used in FIG. The horizontal axis indicates the distance from the center of the wafer W, and the vertical axis indicates the half width. The half width of the diffraction peak in the rocking curve method is used for the evaluation of crystallinity. For example, the full width at half maximum increases as the crystallinity deteriorates due to crystal lattice distortion or crystal defects.

  FIG. 5 shows that the crystallinity of the chamber PM1 deteriorates from the center portion of the wafer W toward the outer peripheral portion. The reason is as follows. The measured value L of the heat radiation intensity decreases due to the clouding of the light transmission window 2a, and the radiation thermometer 10 outputs an apparent temperature T lower than the actual temperature Ta of the wafer W. Thereby, the control part 11 controls process temperature higher than desired temperature. As a result, the crystallinity of the thin film formed on the wafer W deteriorates. In the chamber PM1, since the processing temperature is controlled to be high at the outer peripheral portion of the wafer W, its crystallinity is deteriorated.

  In contrast, the film forming apparatus 1 according to the present embodiment accurately measures the actual temperature Ta of the wafer W, and controls the processing temperature of the wafer W based on the measured temperature. Thereby, the film-forming apparatus 1 can suppress the deterioration of crystallinity due to temperature and can form a high-quality thin film.

  As described above, the film forming apparatus 1 according to the present embodiment calculates the transmittance Tr of the light transmission window 2a based on the initial reflected light intensity of the wafer W even when the light transmission window 2a is clouded. Then, the emissivity ε or the measurement temperature T can be corrected. As a result, the film forming apparatus 1 can form a film having a desired film thickness or quality, and the frequency of maintenance of the light transmission window 2a is reduced, improving the throughput of the film forming process and the productivity of the semiconductor device. Can be made.

  The reason why the first initial transmitted light intensity of the light transmission window 2a is measured every time the light transmission window 2a is replaced is to eliminate the influence of individual differences in window members. The window member used for the light transmission window 2a is an optical component processed with high precision, but due to errors in processing dimensions, surface finishing, installation work, etc., temperature measurement is performed by replacing the window member when replacing the window member. It is difficult to obtain a light transmittance reproducibility that does not cause the above error. On the other hand, since the above-mentioned errors do not occur after the window member is attached, by evaluating the initial reflected light intensity based on the first initial reflected light intensity measured immediately after the replacement of the window member, the light transmitting window 2a It is possible to accurately evaluate the effects of cloudy weather. If the reproducibility of the window member and the mounting so that the above error can be ignored is obtained, the measurement of the first initial reflected light intensity immediately after the replacement of the light transmission window 2a is unnecessary.

  In addition, the light transmittance of an optical member may increase by depositing on the surface of an optical member very rarely. This is because the reflectance of the surface of the optical member is lowered due to the influence of the deposit. In such a case, Tr> 1, but the temperature correction described so far can be performed in exactly the same way.

  Note that the change in emissivity ε is not taken into consideration in Equation 2. The emissivity of a substance changes with temperature. Alternatively, the emissivity when a thin film of a different material is formed on the surface of the material changes due to the optical interference effect of the formed thin film. Even in that case, the relationship between the reflectance and the emissivity in Equation 1 holds. Therefore, the reflectivity of the wafer W can be measured, and the emissivity of the wafer W can be measured even when there is an optical interference effect due to any temperature or film formation. By using the emissivity thus measured in Equation 2, even when the temperature changes or when a thin film is formed on the surface of the wafer W, the temperature can be accurately evaluated. The method of correcting the change in emissivity by performing the temperature change or the film forming process while measuring the reflectivity in this manner is known as emissivity correction pyrometry (ECP (Emissivity Correcting Pyrometry)). By combining ECP and the method of measuring the initial reflected light intensity according to the present embodiment, the temperature during film formation can be evaluated more accurately than when the emissivity does not change. In addition, in a normal radiation thermometer that does not measure the reflectance of the measurement object, the interference effect due to the formation of a thin film on the wafer W may be reduced by adjusting the optical characteristics of the radiation thermometer. is there. Specifically, the above adjustment method is to adjust the measurement wavelength range of the heat radiation light measured by the radiation thermometer. Preferably, the measurement wavelength range is set to 5% or more with respect to the center value of the wavelength range. For example, when the center of the measurement wavelength of the thermal radiation light of the radiation thermometer is 1 μm, the measurement wavelength range is set to a range of 975 nm or more and 1025 nm or less. A more preferable measurement wavelength range is 10% or more, most preferably 20% or more of the center wavelength of the wavelength range. By setting the measurement wavelength range in this way, the interference effect can be effectively reduced when forming a thin film with a film thickness greater than or equal to the center value of the measurement wavelength, and accurate temperature measurement is possible even with a normal radiation thermometer. Is possible.

(Second Embodiment)
The film forming apparatus 1 according to the first embodiment measures the initial reflected light intensity of the wafer W and corrects the emissivity or the measurement temperature. In contrast, the film forming apparatus 1 according to the second embodiment measures the growth rate of a film formed on the wafer W as a parameter and corrects the measurement temperature. The growth rate is obtained by dividing the thickness of the formed film by the formation time of the thin film, and is expressed in units obtained by dividing the thickness by time, such as nanometers / minute and microns / hour. The growth rate correlates with the temperature of the wafer W or the film formation temperature. The film forming temperature is the temperature of the wafer W. This correlation occurs because the film formation temperature affects the thin film formation mechanism. Examples of the elementary process of the thin film formation mechanism that the specific film forming temperature affects include thermal decomposition of the raw material in the gas phase and thermal desorption of the raw material adsorbed on the wafer.

In thin film formation using a thermally decomposable raw material such as MOCVD, when the film forming temperature is low, the raw material does not decompose and the thin film does not grow. When the film formation temperature exceeds a certain level, the raw material starts to decompose, and the film formation rate increases with the temperature rise. When the film forming temperature is further increased, thermal decomposition of the raw material in the gas phase becomes remarkable, and the raw material cannot reach the wafer.
In this case, the film formation rate decreases as the film formation temperature increases. Further, the raw material adsorbed on the surface on which the thin film is formed is desorbed again into the gas phase when the film forming temperature is high, and the substantial growth rate is reduced. In order to obtain a thin film with good film quality, it is common to increase the film forming temperature. In such a temperature range, the film formation rate decreases as the film formation temperature increases. The film forming apparatus 1 measures the growth rate by using the correlation between the film forming temperature and the growth rate, and measures the exact temperature of the wafer W.

  The film forming apparatus 1 measures the growth rate using the reflected light intensity measured by the optical monitor 12. Since the configuration of the film forming apparatus 1 according to the second embodiment is the same as that of the film forming apparatus 1 according to the first embodiment, a detailed description thereof will be omitted.

  The growth rate can be detected in situ by monitoring the change in light reflectance over time. In this method, the substrate is irradiated with light through an optical window provided on the wall surface of the film forming apparatus, and the reflectance of light having a specific wavelength is measured during the film forming process. When the surface of the substrate is mirror-like, the light applied to the thin film formed on the substrate is observed by the interference effect between the reflected light on the surface of the thin film and the reflected light at the interface between the substrate and the thin film. The reflected reflectance periodically changes with respect to the thickness of the thin film. That is, the reflectance is a periodic function of the film thickness. Therefore, the optical constant and film thickness of the thin film to be formed can be calculated from values such as the period of change in reflectivity with respect to the film thickness, the minimum value and the maximum value of the reflectivity, and the film formation time. The growth rate can be calculated from

  FIG. 6 is a diagram showing measured values of the temporal change in reflectance during the deposition of AlN and AlGaN. The vertical axis represents reflectance, and the horizontal axis represents time. G0401 and G0446 indicate process numbers of the film forming process. For example, the film forming apparatus 1 executes the process G0401, then repeats the film forming process 44 times, and then executes the process G0446. The film forming apparatus 1 according to the second embodiment can be used for forming various films on the wafer W. Hereinafter, for example, when depositing AlN, GaN, AlGaN, or InGaN on the silicon wafer W, Will be explained.

  Here, referring to FIG. 6, the period of time change of the reflectance of the wafer W in the process G0446 is longer than the period of time change of the reflectance of the wafer W in the process G0401. As described above, the reflectance is a periodic function of the film thickness of the thin film, so that a longer period indicates that the growth rate of the thin film is reduced. For example, the reflectivities in the processes G0401 and G0446 change with substantially the same period in the deposition of the thin films AlN-1 and AlN-2. That is, in the processes G0401 and G0446, the thin films AlN-1 and AlN-2 are grown at substantially the same speed. However, in the formation of the thin films AlGaN-1 and AlGaN-2, the reflectance of the process G0446 changes with a delay from the reflectance of the process G0401. In other words, in the formation of the thin films AlGaN-1 and AlGaN-2, the growth rate of the process G0446 is lower than that of the process G0401. Thus, the growth rate of the process G0446 is slower than the growth rate of the process G0401, and the film formation temperature of the process G0446 is higher than the film formation temperature of the process G0401.

  The optical monitor 12 outputs the change in reflectance over time to the control unit 11. The control unit 11 measures the growth rate using the change in reflectance with time.

  Hereinafter, a method for calculating the optical constant and growth rate of the film to be formed from the film thickness dependence of the reflectance will be described.

When light is incident perpendicular to the substrate, the reflectance of the electric field on the surface of air (refractive index = 1) and the thin film (refractive index = n, absorption coefficient = 0) formed on the substrate is represented by r ₀ . Then, r ₀ is expressed by the following formula 8. In the following embodiment, “air” may be read as “vacuum” or “gas”.
r ₀ = (1−n) / (1 + n) (Formula 8)

  When the thin film absorbs light in Equation 8, the refractive index n may be replaced with the complex refractive index = n + ik (k is an absorption coefficient). In Expression 8, i is an imaginary unit (hereinafter the same).

The reflectivity r ₁ at the interface between the thin film and the substrate is expressed by the following Equation 9 using the absorption coefficient k _s of the substrate and the refractive index n _{s of the} substrate.
r ₁ = (n−ik _s −n _s ) / (n + ik _s + n _s ) (Formula 9)

Reflected light from the actual thin film passes through the reflected light at the interface between the air and the thin film and the interface between the air and the thin film, and then passes p times (p Is the sum of all the light that passes through the interface between the thin film and air and returns to the air after reciprocating. Further, since the phase changes when the light passes through the thin film, the electric field _{Er of the} reflected light is expressed by the following Expression 10 when the change in the phase is taken into consideration.
_{E r = E 0 r 0 +} E 0 (1-r 0 2) r 1 · exp (i2φ) {1-r 1 r 0 · exp (i2φ)
+ (− R ₁ r ₀ ) 2exp (i4φ) +.
_{= E 0 r 0 + E 0} (1-r 0 2) r 1 · exp (i2φ) / {1 + r 1 r 0 · exp (i2φ)}
= E ₀ {r ₀ + r ₁ · exp (i2φ)} / {1 + r ₁ r ₀ · exp (i2φ)} (Formula 10)

E ₀ in Equation 10 is an electric field of light irradiated on the thin film. Therefore, the electric field reflectivity r of the thin film is expressed by the following formula 11.
r = E _r / E ₀ = {r ₀ + r ₁ · exp (i2φ)} / {1 + r ₁ r ₀ · exp (i2φ)} (Formula 11)

Here, a phase difference (hereinafter referred to as a phase) φ generated when light travels back and forth within the thin film is expressed by the following equation 12 using the refractive index n of the thin film, the film thickness d of the thin film, and the wavelength λ of the light. It is represented by
φ = 2πnd / λ (Formula 12)

As shown in Equation 12, the phase φ is proportional to the film thickness d and increases linearly as the film thickness d increases. The reflectivity (energy reflectivity) of the observed light is proportional to the square of the amplitude of the reflectivity of the electric field. That is, the electric field reflectivity and energy reflectivity are periodic functions of film thickness. Conversely, assuming that the thickness of the thin film is proportional to the growth time, n, n _s , k _s , and the growth rate (d / hour) used in Equation 11 are obtained from Equation 8 and Equation 9 from the change in reflectance over time. be able to.

  By using such a method, the control unit 11 can measure the growth rate from the change in reflectance with time.

  Note that the control unit 11 may measure the growth rate using a time of one wavelength from a certain peak to the next peak in the change in reflectance over time, instead of the above growth rate calculation method. In this case, although the accuracy of the growth rate is lower than that of the above method, the control unit 11 can more easily measure the growth rate.

  FIG. 7 is a diagram showing measured values of the growth rate ratio of GaN with respect to the number of film forming processes. The horizontal axis indicates the number of film forming processes (process number), and the vertical axis indicates the growth rate ratio.

  The growth rate ratio is the first growth rate Gr1 measured through a new (immediately after replacement) light transmission window 2a in a certain film formation process (first film formation process) and the second growth rate after the first film formation process. It is a ratio (Gr2 / Gr1) to the second growth rate Gr2 measured through the light transmission window 2a in the film forming process. In the first film formation process, the growth rate ratio is the ratio between the first growth rate Gr1 and the first growth rate Gr1 (Gr1 / Gr1 = 1). In the example shown in FIG. 7, the process G0401 is the first film formation process, and the growth rate ratio at this time is 1.

The first growth rate Gr1 is a growth rate measured when the first film formation process is performed. That is, the first growth rate Gr1 is a growth rate calculated using the reflected light intensity measured at the time of performing the first wafer W film formation process. The second growth rate Gr2 is a growth rate calculated using the reflected light intensity measured at the time of execution of an arbitrary film forming process after the second time. That is, the second growth rate Gr2 is a growth rate measured at the time of performing the second and subsequent wafer W film forming processes.
It should be noted that the first growth rate Gr1 may be measured in the film forming process after several film forming processes are performed if the light transmission window 2a is not clouded. In this case, the second growth rate Gr2 is measured when an arbitrary film forming process after the first growth rate Gr1 is executed. In addition, the first and second growth rates Gr1 and Gr2 may be measured for each of the thin films AlN-1, AlN-2, AlGaN-1, and AlGaN-2, or may be measured for any one of them. Also good. However, the thin films with which the growth rate ratios are compared are preferably the same.

  In the first film forming process G0401, the growth rate ratio indicates the ratio (Gr1 / Gr1 = 1) between the first growth rate Gr1 and the first growth rate Gr1. When the number of film formation processes is 1 or more, the growth rate ratio (Gr2 / Gr1) tends to decrease as the number of film formation processes increases. For example, in the process G0446, the growth rate ratio (Gr2 / Gr1) is 0.99 or less. This is because, in the process G0446, clouding occurs in the light transmission window 2a, thereby increasing the film formation temperature of GaN. The controller 11 corrects the film forming temperature using this growth rate ratio.

  For example, as shown in FIG. 7, the growth rate ratio of G0446 is about 99% (about 0.99), which is about 1% lower than that of G0401. In the example of this embodiment, it is empirically found that when the growth rate ratio is reduced by 1% at an apparent temperature of 1000 ° C., the actual temperature is about 1002 ° C. to 1003 ° C. Actually, the temperature dependence of the growth rate depends on the deposition conditions, deposition equipment, etc., so it is necessary to acquire data on the temperature dependence of the deposition rate in advance according to the actual deposition. is there. The controller 11 stores such an empirical correlation between the growth rate and the film formation temperature as a relational expression. Therefore, the control unit 11 calculates a temperature error from the decrease in the growth rate ratio, and uses the temperature error to calculate the measured temperature (apparent temperature T) obtained from the radiation thermometer 10 with an accurate film formation temperature ( Correct to actual temperature Ta). Thereby, the control part 11 can control the heater 7 using the exact actual temperature Ta.

  Next, the operation of the film forming apparatus 1 according to the second embodiment will be described.

FIG. 8 is a flowchart showing the operation of the film forming apparatus 1 according to the second embodiment. First, the optical monitor 12 measures the change in reflectance over time during the first film formation process as the first film formation process. The first film forming process is, for example, the first film forming process of the wafer W after the replacement of the light transmission window 2a.
The optical monitor 12 outputs the measured change in reflectance over time to the control unit 11. The controller 11 calculates the first growth rate Gr1 of the first film formation process (S11). The control unit 11 stores the first growth rate Gr1 in an internal memory (not shown). In the first film formation process, it is assumed that the light transmission window 2a is not cloudy and the transmittance Tr of the light transmission window 2a is 1. Therefore, the control unit 11 outputs the apparent temperature T from the radiation thermometer 10 without substantially correcting it.

  After the completion of the first film forming process, the film forming apparatus 1 unloads the wafer W after the film forming process, and then loads the second wafer W for executing the film forming process (S21). Next, the optical monitor 12 measures the temporal change in the reflectance of the thin film in the second film formation process. The controller 11 measures the second growth rate Gr2 for the second film formation process (S31). Next, the controller 11 calculates a growth rate ratio (Gr2 / Gr1) (S41). Further, the control unit 11 corrects the apparent temperature T from the radiation thermometer 10 to the actual temperature Ta by calculating an error of the film forming temperature from the growth rate ratio (S51). The control unit 11 controls the heater 7 based on the corrected actual temperature Ta.

  The third and subsequent film forming processes are executed in the same manner as the second film forming process. The growth rate measured during the third and subsequent film formation processes is also referred to as a second growth rate Gr2 for convenience. That is, after completion of each film forming process, the film forming apparatus 1 unloads the wafer W after the film forming process, and then loads the wafer W to be subjected to the film forming process (S21). The optical monitor 12 measures the second growth rate Gr2 in each film forming process (S31). The optical monitor 12 outputs the second growth rate Gr2 measured in each film forming process to the control unit 11. The controller 11 also stores the second growth rate Gr2 in the third and subsequent film formation processes in the internal memory. Next, the radiation thermometer 10 calculates the ratio of the second growth rate Gr2 to the first growth rate Gr1 (growth rate ratio = Gr2 / Gr1) (S41). Further, the control unit 11 corrects the apparent temperature T from the radiation thermometer 10 to the actual temperature Ta by calculating an error of the film forming temperature from the growth rate ratio (S51). The control unit 11 controls the heater 7 based on the corrected actual temperature Ta.

  The control unit 11 may warn the user that there is a problem with the clouding of the light transmission window 2a based on the growth rate ratio. For example, the control unit 11 determines whether or not the growth rate ratio has become a predetermined value or less (S61). When the number of film formation is small and the growth rate ratio is larger than the predetermined value (NO in S61), the film formation apparatus 1 performs steps S21 to S51 again after the film formation is completed. On the other hand, when the growth rate ratio is equal to or less than the predetermined value (YES in S61), the film forming apparatus 1 notifies the user that there is a problem with the clouding of the light transmission window 2a after the film formation ends (S71). The notification to the user may be output to a monitor (not shown) or an alarm sound may be sounded by a speaker (not shown).

  As described above, the film forming apparatus 1 according to the second embodiment corrects the measurement temperature from the radiation thermometer 10 by measuring the growth rate of the thin film and calculating the growth rate ratio. Thereby, the film-forming apparatus 1 by 2nd Embodiment can acquire the effect similar to the film-forming apparatus 1 by 1st Embodiment.

  In the present embodiment, an example including step S11 for measuring the first growth rate after replacing the transmission window is shown. However, if a standard growth rate is measured before that, step S11 is performed. May be omitted. This is because the cloud of the light transmission window does not significantly affect the accuracy of the growth rate when the temperature does not significantly affect the refractive index of the thin film. Specifically, the deposition temperature does not greatly affect the refractive index of the material to be deposited. One element or the stoichiometric ratio does not greatly depend on the growth rate, and the refractive index such as impurity concentration is affected. This is a case where the property that affects the temperature does not greatly depend on the temperature. Specifically, a case where a film is formed at a sufficiently high temperature using a one-element material such as silicon or germanium or a two-element material such as gallium nitride (GaN) or aluminum nitride (AlN) can be given.

  Similarly to the first embodiment, by adjusting the optical characteristics of ECP and the same radiation thermometer, it is possible to reduce the interference effect by forming a thin film during temperature measurement.

(Third embodiment)
The film forming apparatus 1 according to the second embodiment measures the growth rate of the thin film crystal during film formation on the wafer W and corrects the measurement temperature. In contrast, the film forming apparatus 1 according to the third embodiment measures the refractive index of the thin film during the film formation on the wafer W as a parameter, and corrects the measurement temperature. The refractive index of the thin film has a correlation with the temperature of the wafer W or the film formation temperature.

  For example, in a mixed crystal compound such as InGaN or AlGaN, the composition ratio of the mixed crystal changes depending on the film forming temperature, and the refractive index changes accordingly.

  The film forming apparatus 1 measures the refractive index of the thin film using the reflected light intensity measured by the optical monitor 12. Since the configuration of the film forming apparatus 1 according to the second embodiment is the same as that of the film forming apparatus 1 according to the first embodiment, a detailed description thereof will be omitted.

  The refractive index n calculated in the second embodiment may be used as the refractive index of the thin film. The refractive index n of the thin film has a correlation with the film forming temperature as well as the film forming speed, and is expressed as an empirical relational expression. The controller 11 stores a relational expression between the refractive index n and the film formation temperature. The control unit 11 calculates a refractive index ratio instead of the growth rate ratio of the second embodiment, and calculates a temperature error from the change in the refractive index ratio. The controller 11 corrects the measured temperature (apparent temperature T) obtained from the radiation thermometer 10 to an accurate film formation temperature (actual temperature Ta) using the temperature error. Thereby, the control part 11 can control the heater 7 using the exact actual temperature Ta.

  Similarly to the first embodiment, by adjusting the optical characteristics of ECP and the same radiation thermometer, it is possible to reduce the interference effect by forming a thin film during temperature measurement.

  The first to third embodiments may be arbitrarily combined. In this case, the corrected measured temperature used for controlling the heater 7 may preferentially use one of the measured temperatures obtained in the first to third embodiments, or may use an average value. .

  In the first to third embodiments, the growth apparatus for processing one wafer W as shown in FIG. 1 has been described as an example. However, the present invention is not limited to this, and the apparatus for processing a large number of wafers W at one time. It can also be applied to.

  In the present embodiment, the method of using the parameter correlated with the temperature measured for each growth as it is for temperature control of each growth is explained. However, the parameter correlated with the above temperature is about several different growths. You may utilize what gave the statistical process about what was measured. In other words, if there is a measurement error in the parameter correlated with the above temperature, and the parameter correlated with the temperature measured in each growth is used as it is for temperature control, the temperature control is not stable. By taking the average value of the above parameters for several runs, the influence of errors for each run can be suppressed. Alternatively, a certain standard value is provided for a parameter having a correlation with temperature, and when the value of the parameter having a correlation with temperature exceeds the standard value, this parameter can be reflected in the temperature control. For example, when the cloud of the light transmission window 2a gradually progresses as it grows, if the temperature error calculated from the parameter correlated with the temperature is less than the set standard value, this parameter is reflected in the temperature control. First, after the growth run in which the temperature error is equal to or greater than the standard value, the temperature can be controlled using a predetermined correction value obtained in advance. Thereafter, when the temperature error is less than the standard value, the predetermined correction value is continuously used for temperature control.

  As the statistical processing as described above, a known one can be used as appropriate according to the contents of film formation.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 Film-forming apparatus, 2 chamber, 2a light transmission window, 3 gas supply part, 3a gas storage part, 3b gas pipe, 3c gas valve, 4 raw material discharge | release part, 4a shower plate, 5 susceptor, 6 rotation part, 7 heater, 8 Gas exhaust section, 9 exhaust mechanism, 10 radiation thermometer, 11 control section, 12 optical monitor

Claims (9)

A film forming chamber for containing a substrate and performing a film forming process for each substrate;
A gas supply unit for supplying a gas onto the substrate;
A heater for heating the substrate;
A window provided in the film forming chamber;
A radiation thermometer for measuring the temperature of the substrate through the window;
A parameter acquisition unit for acquiring a parameter correlated with the temperature of the substrate;
A correction unit that corrects the temperature of the substrate based on a variation from an initial value of the parameter;
A controller that controls the heater based on the temperature of the substrate or the corrected temperature of the substrate;
A film forming apparatus comprising:   The film forming apparatus according to claim 1, wherein the correction unit corrects the temperature of the substrate in consideration of variation in emissivity due to temperature or an optical interference effect caused by a thin film formed.   The correction unit includes a first reflected light intensity acquired as the parameter before the first film forming process, and a second reflected light acquired as the parameter before the second film forming process after the first film forming process. The film forming apparatus according to claim 1, wherein the temperature of the substrate is corrected based on the intensity. An environmental thermometer for measuring the environmental temperature of the film forming chamber;
The said correction | amendment part correct | amends the temperature of the said board | substrate based on the said 1st reflected light intensity measured by making the said environmental temperature substantially the same, and a said 2nd reflected light intensity. Film forming equipment.   The film forming apparatus according to claim 3, wherein the correction unit corrects the temperature of the substrate based on a ratio between the first reflected light intensity and the second reflected light intensity.   The correction unit calculates a corrected emissivity by correcting the emissivity based on a ratio of the first reflected light intensity and the second reflected light intensity, and uses the thermal radiation light intensity and the corrected emissivity. The film forming apparatus according to claim 3, wherein the temperature of the substrate is calculated.   The film forming apparatus according to claim 1, wherein the correction unit corrects the temperature of the substrate based on a growth rate of a predetermined film formed on the substrate acquired as the parameter.   The film forming apparatus according to claim 1, wherein the correction unit corrects the temperature of the substrate based on a refractive index of a predetermined film formed on the substrate acquired as the parameter. A film forming method for supplying gas onto the substrate while heating the substrate accommodated in the film forming chamber to a predetermined temperature with a heater,
Measuring the temperature of the substrate through a window provided in the deposition chamber;
Obtaining a parameter correlated with the temperature of the substrate;
Correcting the temperature of the substrate based on a variation from an initial value of the parameter, and controlling the heater so that the corrected temperature of the substrate becomes a predetermined temperature;
Film forming method.