JP3915679B2 - Heat treatment method for semiconductor wafer - Google Patents

Description

【００２２】
次に、ウェハ処理中の反射エネルギーＶ_W（ｚ，Ｔ）、熱放射エネルギ−Ｉ（Ｔ）、及び先に求めた反射率の炉内補正係数Ｋ（ｚ）に基づいて、次の関数（２）及びプランクの法則式（３）より、熱処理中における実際のウェハ温度Ｔが得られる。なお、放射率ε（Ｔ）と反射率Ｒ（Ｔ）は、ε（Ｔ）＝１−Ｒ（Ｔ）に示される関係にある（ここでは、透過率はゼロである。フィルタリングにより、透過率がゼロになる波長帯の放射エネルギーをパイロメータに読ませている。）。
【００２３】
【数２】

【００２４】
ここで、Ｉは熱放射エネルギー（Ｗ/ｍ²）、εは物体の放射率、λは熱放射の波長（ｍ）、Ｔは物体の温度（Ｋ）、Ｃ₁、Ｃ₂はそれぞれプランクの第１、第２定数である。
【００２５】
以上より、光検出器を用いて放射率補正を行うことにより、パイロメータを用いてウェハ処理中の温度測定を行うことが出来る。
【００２６】
【特許文献１】
特開２００１−１９４０７５号公報（段落番号００６５〜００６７）
【特許文献２】
特開平１０−５５９７４号公報（段落番号００１８〜００３２）
【００２７】
【発明が解決しようとする課題】
しかしながら、実際に熱処理をする際にウェハの放射率εが低いと、放射率測定誤差が温度測定に与える影響が大きくなる。
【００２８】
具体的には、式（３）のεにウェハの放射率そのものを用いる場合の温度誤差と放射率誤差の関係を表わすと図５のようになる（式（３）のεにウェハの放射率そのものを用いない場合もある。例えば特開平１０−５５９７４号公報）。図５より、放射率εが低いほど、少しの放射率誤差でも温度誤差としては大きく影響してしまうことが分かる。
【００２９】
しかし放射率εが高すぎると、図１に示したホットウォールタイプの装置では、光を用いてウェハ裏面の放射率を直接測定するシステムを用いているため、温度測定エラーが発生する。それは、放射率εと反射率Ｒの関係式ε（Ｔ）＝１−Ｒ（Ｔ）から、放射率εが高いということは反射率Ｒが低いということであり、ウェハからの光の反射量が微弱となるためである。その結果、光検出器に発生する電圧信号が、ノイズの大きさと同様かまたはそれ以下になるため、正確に放射率を算出することが出来ない。
【００３０】
よって本発明では、図１に示した装置のように、ウェハの放射率を直接測定するシステムにおいて、光検出器自体のノイズの影響を受けにくい範囲でウェハ裏面の放射率εを測定することにより、正確かつ正常にウェハを処理する方法を提供することを目的とする。
【００３１】
【課題を解決するための手段】
上記課題を解決するために、本発明では、ウェハに光を照射し、その放射率からウェハ温度を算出するシステムを有する熱処理装置において、ウェハ裏面における放射率が光検出器の検出範囲内にある場合は、熱処理工程中に測定した放射率に基づいて温度を算出し、ウェハ裏面における放射率が光検出器の検出範囲外にある場合は、熱処理工程前に測定した放射率に基づいて温度を算出することを特徴とする、半導体ウェハの製造方法を提供する。
【００３２】
その結果、ウェハ裏面の反射率が低すぎる場合においても、より正確にウェハ処理時の温度を求めることができるため、温度測定エラーの発生を抑え、精度良く熱処理を行うことが出来る。
【００３３】
【発明の実施の形態】
本発明の実施形態について、図面を参照しながら説明する。
【００３４】
本発明は、図１〜３のような光検出器などを用いてウェハの反射率（または放射率）を測定する装置の場合、ウェハの反射率の値によって実際の温度測定で用いない反射率を選択することに特徴がある。その場合、熱処理温度は、主に２つのパラメータである、パイロメータにより測定される熱放射エネルギーＩと、光検出器により測定される熱放射率ε（つまり、反射率Ｒ）に基づいて導き出される。なお、ウェハを透過しない波長帯の熱放射エネルギーを用いることにより、放射率εと反射率Ｒは、ε＝１−Ｒの式で表わされる関係にある。以下、図４のフロー図を用いて具体的に説明する。
【００３５】
まず、図４（ａ）の工程前において、ウェハ裏面に膜の堆積、あるいは膜の除去等により、低反射率の膜、例えばＳｉＮ，ＴＥＯＳ、又はＳｉＣ等の膜を表面に露出させ、熱処理装置に搬入する。
【００３６】
次に、図４（ｂ）の工程において、熱処理装置の炉内に導入される前に、室温におけるウェハ裏面の反射率を測定する。本工程は、図３（ａ）に示すステップに該当し、積分球６により、炉外におけるウェハ裏面の反射率Ｒ₀を測定する。
【００３７】
その後、図４（ｃ）の工程において、ウェハ裏面の反射率Ｒがしきい値と比較して大きいか小さいかを確認する。しきい値は、図５に示した温度エラーと放射率エラーの関係、及び光検出器の検出限界に基づいて設定する。
【００３８】
具体的には、放射率誤差が比較的大きくなったとしても、温度誤差としてはほとんど変化しない値で、光検出器で測定可能な反射率の範囲の値であることが望ましい。それは、図５より放射率εが高いほど、つまり反射率Ｒが低いほど、反射率Ｒに基づく温度エラーの値は小さくなるが、反射率Ｒが小さすぎるとパイロメータに反射してくる光も弱くなるためである。
【００３９】
ここで、図３に示す装置において、パイロメータはウェハからの熱放射エネルギーＩを読み取る働きをし、ウェハの放射率εは光検出器により感知され、温度測定はこれら２つのパラメータ、つまり熱放射エネルギーＩと放射率εから計算される。よって、ウェハの反射率Ｒが小さすぎて、反射光があまりにも弱いと、得られる変換電圧が光検出器自体の誤差範囲内に含まれてしまい、正確な測定ができない。従って、光検出器の測定可能範囲内である値のしきい値を、例えば放射率０．９８以上、つまり反射率０．０２以下に設定する。
【００４０】
その結果、放射率ε、もしくは反射率Ｒがしきい値より大きいか小さいかによって、最適な温度測定方法が異なってくる。
【００４１】
まず、図４（ｄ）に示すように、しきい値より反射率Ｒが小さい場合、つまり放射率εが大きい場合について説明する。
【００４２】
しきい値より反射率Ｒが小さい場合は、つまり図５でいうと放射率εが大きいほど、反射率の誤差が温度の誤差に対してほとんど影響を及ぼさなくなる。しかし、反射率Ｒが小さすぎるとウェハからの反射光が弱くなり、光検出器の検出限界を超えて誤差範囲に含まれてしまう。よって、熱処理中のウェハにおいて、光検出器を用いて放射率を測定することが出来ない、もしくは測定できたとしても、正確な値を得られる可能性が大変低くなる。
【００４３】
従って、反射率Ｒがしきい値以下である場合は、熱処理前のウェハにより測定した反射率Ｒ₀を、熱処理中のウェハにおける反射率Ｒとする。図５より、反射率Ｒが低い、つまり放射率εが高い場合は放射率εの値に関わらず、ほぼ温度誤差は一定であるので、実測値を用いなくても正確な温度測定が出来る。この理由について、以下より具体的に説明する。
【００４４】
熱放射を利用する温度計測では、物体の表面から放射される熱放射量が物体の温度の他に、物体の性質と光学的な要因によって決まる放射率εの影響を受ける。物体の表面から放射される熱放射エネルギーＩは、温度と波長の関数（プランクの法則）で下記式（３）のように表わされる。
【００４５】
【数３】

【００４６】
ここで、Ｉは熱放射エネルギー（Ｗ/ｍ²）、εは物体の放射率、λは熱放射の波長（ｍ）、Ｔは物体の温度（Ｋ）、Ｃ₁、Ｃ₂はそれぞれプランクの第１、第２定数である。
【００４７】
波長が一定ならば、上式（３）において熱放射の強さＩと物体の放射率εは温度Ｔのみの関数となる。
【００４８】
パイロメータでは、熱放射エネルギーＩと熱放射によって得られる電流値が一次の関係にあり、波長が既知であると、物体の放射率εが分かれば温度Ｔが求められる。温度測定に使用する熱放射の波長λのオーダーは１０^-3ｍ、Ｔのオーダーは１０³Ｋ程度であるので、ｅ^c2/λ^T≒１となる。したがって式（３）は下記式（４）のように近似できる（ウィーンの公式）。
【００４９】
【数４】

【００５０】
上式（４）の左辺はパイロメータの読み値であるから、一定としてＴについて微分すると下式（５）が得られる。
【００５１】
【数５】

【００５２】
上式（５）においてウェハ放射率εの誤差ｄε及びウェハ温度Ｔの誤差ｄＴの関係をグラフで表わした結果が、先でも説明した図５である。図５より放射率εが大きい場合は、温度誤差ｄＴが小さくなることが分かる。高放射率のウェハを処理する場合、室温での放射率εと処理中（高温）での放射率εの変化は非常に小さいため、室温での放射率εを処理中の放射率εとして見なしても、大きな誤差は発生しない。
【００５３】
例えば、放射率が０．９８〜０.９９のウェハを処理する場合は、放射率誤差ｄε=０．００５程度となることが分かっている。その場合、図５よりｄＴ＝−５．０程度の温度誤差となる。従って、熱処理前に測定した放射率εを処理中のウェハの放射率εと見なしても大きな誤差を生じることはなく、実測値の代わりに用いることが出来る。
【００５４】
次に、図４（ｅ）に示すように、しきい値より反射率Ｒが大きい場合、つまり放射率εが小さい場合について説明する。
【００５５】
反射率Ｒがしきい値より大きい場合は、つまり図５で言うと放射率εが小さいほど、反射率エラーが温度エラーに対して大きな影響を及ぼす。よって、先で説明したように処理前の反射率Ｒ₀を代わりに使用することは出来ず、処理中の反射率Ｒを正確に測定する必要がある。この場合、熱処理中の反射率Ｒは、光検出器の測定限界であるしきい値以上の値であるため、基本的には正確に熱処理中の温度測定することが出来る。
【００５６】
本実施形態におけるしきい値は、光検出器の検出限界に基づいて求められた反射率Ｒであり、裏面につける膜の種類や熱処理時の温度によって、ある程度影響され変化する。よって、本実施形態では仮に、しきい値はＲ＝０．０２としたが、これらの値に限定されるものではない。
【００５７】
また本発明では、放射率に基づいて温度を算出する方法について説明したが、放射率から反射率を求めることが出来るので、反射率を用いて温度を算出することも出来、放射率の測定に限定されるものではない。よって、初めに反射率を測定して、反射率に基づいて温度を求めることも出来る。
【００５８】
【発明の効果】
以上本発明によると、ウェハに光を照射し、その反射率及び反射光強度に基づいてウェハ温度測定をする場合において、ウェハ裏面における反射率によって、温度測定方法を変えることにより、温度測定誤差を最小限に抑えることが出来る。例えば、ウェハ裏面の反射率が低すぎて、光検出器の検出限界を超えて、放射率の測定が不可能である場合は、その代わりに熱処理前の放射率を用いて温度を求めることが出来る。
【図面の簡単な説明】
【図１】ホットウォールタイプの熱処理装置を示す図
【図２】ホットウォールタイプの装置におけるウェハの位置と炉内温度の関係を示す図
【図３】ホットウォールタイプの熱処理装置を示す図
【図４】ホットウォールタイプの装置における測定フローを示す図
【図５】温度エラーと放射率エラーの関係を示す図
【符号の説明】
１ トランスファーロボット
２ ヒーター
３ エレベーター
４ パイロメータ
５ 光検出器
６ 積分球
７ ウェハ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring a wafer temperature, particularly in a method for manufacturing a semiconductor wafer.
[0002]
[Prior art]
In recent years, an increasing number of processes using rapid thermal processing (Rapid Thermal Annealing) in the manufacturing process of semiconductor wafers.
[0003]
The apparatus used for the rapid thermal processing can be classified into those that measure the temperature of the wafer being processed and those that measure the temperature of a heat source such as a heater without directly measuring the wafer temperature.
[0004]
In order to perform rapid thermal processing with high accuracy, it is necessary to accurately measure and control the wafer temperature during processing, so the former is a more effective system for rapid thermal processing.
[0005]
There are two methods for measuring the wafer temperature, one using a thermocouple and the other using a pyrometer. In particular, the method using a pyrometer can measure the temperature of the wafer more accurately than a thermocouple, and is becoming the mainstream of rapid thermal processing equipment.
[0006]
Here, there are two types of heat sources used in the rapid thermal processing apparatus: a lamp and a heater. The former is generally called a cold wall type device and the latter is a hot wall type device.
[0007]
Currently, lamp type devices are mainly used, but hot wall type devices are also being used in recent years.
[0008]
A typical hot wall type apparatus and its temperature measuring method will be described below.
[0009]
First, a typical structure of a hot wall type heat treatment apparatus is shown in FIG. As shown in FIG. 1, the wafer 7 is introduced into the furnace of the heat treatment apparatus by the transfer robot 1. In the furnace of this heat treatment apparatus, there is a heater 2 along the side wall portion.
[0010]
Next, the wafer 7 introduced into the furnace is moved up to a certain height by the elevator 3 and is heated by the heater 2 on the side wall in the furnace to be heat-treated. In the case of this apparatus, the emissivity ε from the back surface of the wafer is measured by a photodetector (photodetector) 5 installed at the bottom of the elevator 3 in addition to the pyrometer 4.
[0011]
In this heat treatment apparatus, as shown in FIG. 2, the temperature change of the wafer itself is controlled by providing a temperature distribution in the furnace.
[0012]
Specifically, as shown in the graph in which the horizontal axis in FIG. 2 is the furnace temperature (° C.) and the vertical axis is the wafer position (mm), the furnace has a higher temperature in the upper part of the furnace, The higher the position of the wafer in the furnace, the higher the temperature of the wafer. Therefore, the temperature change of the wafer is controlled to an arbitrary temperature by adjusting the position of the wafer in the furnace by moving the elevator up and down and changing the time that the wafer stays at that position.
[0013]
Next, a temperature measurement method in a heat treatment apparatus equipped with a photodetector and a pyrometer will be described with reference to FIG.
[0014]
First, in the integrating sphere 6 shown in FIG. 3A, the reflectance R ₀ of the wafer at room temperature before being introduced into the furnace is measured.
[0015]
Specifically, the reflected energy V _W from the wafer and the energy V _REF of the light source are measured as converted voltage values by a photodiode, respectively, using a photodetector. Further, the influence constant C of the integrating sphere 6 itself is measured using a wafer having a known reflectance. Thereafter, the value is substituted into the relational expression R ₀ = C (V _W / V _REF ) to obtain the wafer reflectivity R ₀ at room temperature.
[0016]
Next, by sweeping the elevator 3 without a wafer in the furnace shown in FIG. 3B, the stray light energy V ₀ (z) in a state where no wafer is introduced into the furnace is obtained for each height in the furnace. Is measured using a photodetector (z represents height).
[0017]
Thereafter, the wafer is introduced into the furnace, and the elevator-3 is swept in a state where the wafer is placed, so that the stray light energy V _W0 (z) in the furnace is detected for each height in the furnace. To measure. Here, since the elevator 3 is swept in a short time, the wafer temperature hardly rises and the wafer temperature is about 150 ° C. or less.
[0018]
Subsequently, with the wafer placed on the elevator 3, the wafer is actually heat-treated, and the reflected energy V _W (z, T) of the wafer being heat-treated by the photodetector is converted into the thermal radiation energy I (T) by the pyrometer. Measure.
[0019]
Using the above measurement results, the actual wafer temperature T during the heat treatment can be derived.
[0020]
Specifically, based on the wafer reflectivity R ₀ , the stray light energy V ₀ (z) when there is no wafer in the furnace, and the stray light energy V _W0 (z) when there is a wafer in the furnace, the following relational expression Using (1), the in-furnace correction coefficient K (z) of the reflectance at each height is obtained.
[0021]
[Expression 1]

[0022]
Next, on the basis of the reflected energy V _W (z, T) during the wafer processing, the thermal radiation energy −I (T), and the in-furnace correction coefficient K (z) of the reflectance obtained previously, the following function ( From 2) and Planck's law equation (3), the actual wafer temperature T during the heat treatment can be obtained. Note that the emissivity ε (T) and the reflectance R (T) have a relationship represented by ε (T) = 1−R (T) (here, the transmittance is zero. By filtering, the transmittance is zero). The pyrometer reads the radiant energy in the wavelength band where becomes zero.)
[0023]
[Expression 2]

[0024]
Where I is the thermal radiation energy (W / m ² ), ε is the emissivity of the object, λ is the wavelength of the thermal radiation (m), T is the temperature of the object (K), and C ₁ and C ₂ are Planck's, respectively. First and second constants.
[0025]
As described above, by performing emissivity correction using a photodetector, temperature measurement during wafer processing can be performed using a pyrometer.
[0026]
[Patent Document 1]
JP 2001-194075 A (paragraph numbers 0065 to 0067)
[Patent Document 2]
JP-A-10-55974 (paragraph numbers 0018 to 0032)
[0027]
[Problems to be solved by the invention]
However, when the emissivity ε of the wafer is low during the actual heat treatment, the influence of the emissivity measurement error on the temperature measurement becomes large.
[0028]
Specifically, the relationship between the temperature error and the emissivity error when using the wafer emissivity itself as ε in equation (3) is as shown in FIG. 5 (ε in the equation (3) represents the emissivity of the wafer). In some cases, it is not used (for example, JP-A-10-55974). From FIG. 5, it is understood that as the emissivity ε is lower, even a slight emissivity error greatly affects the temperature error.
[0029]
However, if the emissivity ε is too high, the hot wall type apparatus shown in FIG. 1 uses a system that directly measures the emissivity on the backside of the wafer using light, so that a temperature measurement error occurs. From the relational expression ε (T) = 1−R (T) between the emissivity ε and the reflectivity R, a high emissivity ε means that the reflectivity R is low, and the amount of light reflected from the wafer. Is because it becomes weak. As a result, the voltage signal generated in the photodetector is the same as or smaller than the magnitude of noise, and the emissivity cannot be calculated accurately.
[0030]
Therefore, in the present invention, in the system that directly measures the emissivity of the wafer as in the apparatus shown in FIG. 1, the emissivity ε on the back surface of the wafer is measured within a range that is not easily affected by the noise of the photodetector itself. An object of the present invention is to provide a method for processing a wafer accurately and normally.
[0031]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, in a heat treatment apparatus having a system for irradiating a wafer with light and calculating the wafer temperature from the emissivity, the emissivity on the back surface of the wafer is within the detection range of the photodetector. In this case, the temperature is calculated based on the emissivity measured during the heat treatment process, and when the emissivity on the back surface of the wafer is outside the detection range of the photodetector, the temperature is calculated based on the emissivity measured before the heat treatment process. A method for manufacturing a semiconductor wafer is provided.
[0032]
As a result, even when the reflectance on the back surface of the wafer is too low, the temperature at the time of wafer processing can be obtained more accurately, so that temperature measurement errors can be suppressed and heat treatment can be performed with high accuracy.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0034]
In the case of an apparatus that measures the reflectance (or emissivity) of a wafer using a photodetector or the like as shown in FIGS. 1 to 3, the present invention uses a reflectance that is not used in actual temperature measurement depending on the value of the reflectance of the wafer. There is a feature in selecting. In this case, the heat treatment temperature is derived based on two main parameters, thermal radiation energy I measured by a pyrometer and thermal emissivity ε (that is, reflectance R) measured by a photodetector. Note that, by using thermal radiation energy in a wavelength band that does not transmit through the wafer, the emissivity ε and the reflectance R are in a relationship represented by the equation ε = 1−R. This will be specifically described below with reference to the flowchart of FIG.
[0035]
First, before the step of FIG. 4A, a low-reflectance film such as SiN, TEOS, or SiC is exposed on the surface by depositing or removing the film on the back surface of the wafer, and a heat treatment apparatus. Carry in.
[0036]
Next, in the step of FIG. 4B, the reflectance of the wafer back surface at room temperature is measured before being introduced into the furnace of the heat treatment apparatus. This step corresponds to the step shown in FIG. 3A, and the reflectance R ₀ of the wafer back surface outside the furnace is measured by the integrating sphere 6.
[0037]
Thereafter, in the step of FIG. 4C, it is confirmed whether the reflectance R on the back surface of the wafer is larger or smaller than the threshold value. The threshold value is set based on the relationship between the temperature error and the emissivity error shown in FIG. 5 and the detection limit of the photodetector.
[0038]
Specifically, even if the emissivity error becomes relatively large, it is desirable that the temperature error is a value that hardly changes and is within the range of reflectance that can be measured by the photodetector. As shown in FIG. 5, the higher the emissivity ε, that is, the lower the reflectance R, the smaller the temperature error value based on the reflectance R. However, if the reflectance R is too small, the light reflected on the pyrometer is weaker. It is to become.
[0039]
Here, in the apparatus shown in FIG. 3, the pyrometer serves to read the thermal radiant energy I from the wafer, the emissivity ε of the wafer is sensed by the photodetector, and the temperature measurement is based on these two parameters, namely the thermal radiant energy. Calculated from I and emissivity ε. Therefore, if the reflectance R of the wafer is too small and the reflected light is too weak, the obtained conversion voltage is included in the error range of the photodetector itself, and accurate measurement cannot be performed. Therefore, the threshold value having a value within the measurable range of the photodetector is set to emissivity of 0.98 or more, that is, reflectance of 0.02 or less.
[0040]
As a result, the optimum temperature measurement method differs depending on whether the emissivity ε or the reflectance R is larger or smaller than the threshold value.
[0041]
First, as shown in FIG. 4D, the case where the reflectance R is smaller than the threshold value, that is, the case where the emissivity ε is large will be described.
[0042]
When the reflectance R is smaller than the threshold value, that is, in FIG. 5, as the emissivity ε is larger, the reflectance error has little influence on the temperature error. However, if the reflectance R is too small, the reflected light from the wafer becomes weak and exceeds the detection limit of the photodetector and is included in the error range. Therefore, even if the emissivity cannot be measured using the photodetector in the wafer being heat-treated, even if it can be measured, the possibility of obtaining an accurate value is very low.
[0043]
Therefore, when the reflectance R is equal to or less than the threshold value, the reflectance R ₀ measured by the wafer before the heat treatment is set as the reflectance R of the wafer during the heat treatment. As shown in FIG. 5, when the reflectance R is low, that is, when the emissivity ε is high, the temperature error is almost constant regardless of the value of the emissivity ε. Therefore, accurate temperature measurement can be performed without using actual measurement values. The reason for this will be described more specifically below.
[0044]
In temperature measurement using thermal radiation, the amount of thermal radiation radiated from the surface of an object is influenced by the emissivity ε determined by the properties of the object and optical factors in addition to the temperature of the object. The thermal radiant energy I radiated from the surface of the object is expressed by the following equation (3) as a function of temperature and wavelength (Planck's law).
[0045]
[Equation 3]

[0046]
Where I is the thermal radiation energy (W / m ² ), ε is the emissivity of the object, λ is the wavelength of the thermal radiation (m), T is the temperature of the object (K), and C ₁ and C ₂ are Planck's, respectively. First and second constants.
[0047]
If the wavelength is constant, the intensity I of thermal radiation and the emissivity ε of the object in the above equation (3) are functions of only the temperature T.
[0048]
In the pyrometer, the thermal radiation energy I and the current value obtained by thermal radiation are in a primary relationship, and if the wavelength is known, the temperature T can be obtained if the emissivity ε of the object is known. The order of the wavelength λ of thermal radiation used for temperature measurement is 10 ⁻³ m, and the order of T is about 10 ³ K. Therefore, e ^{c2 /} λ ^T ≈1. Therefore, the equation (3) can be approximated as the following equation (4) (Vienna formula).
[0049]
[Expression 4]

[0050]
Since the left side of the above equation (4) is a pyrometer reading, the following equation (5) is obtained by differentiating with respect to T as constant.
[0051]
[Equation 5]

[0052]
The result of expressing the relationship between the error dε of the wafer emissivity ε and the error dT of the wafer temperature T in the above equation (5) in the graph is FIG. 5 described above. FIG. 5 shows that the temperature error dT decreases when the emissivity ε is large. When processing high emissivity wafers, the change in emissivity ε at room temperature and emissivity ε during processing (high temperature) is very small, so emissivity ε at room temperature is regarded as emissivity ε during processing. However, a large error does not occur.
[0053]
For example, when processing a wafer having an emissivity of 0.98 to 0.99, it has been found that the emissivity error dε = 0.005. In that case, the temperature error is about dT = −5.0 from FIG. Therefore, even if the emissivity ε measured before the heat treatment is regarded as the emissivity ε of the wafer being processed, a large error does not occur and can be used instead of the actual measurement value.
[0054]
Next, as shown in FIG. 4E, the case where the reflectance R is larger than the threshold value, that is, the case where the emissivity ε is small will be described.
[0055]
When the reflectance R is larger than the threshold value, that is, in FIG. 5, as the emissivity ε is smaller, the reflectance error has a greater influence on the temperature error. Therefore, as described above, the reflectance R ₀ before processing cannot be used instead, and it is necessary to accurately measure the reflectance R during processing. In this case, the reflectance R during the heat treatment is a value equal to or higher than the threshold value which is the measurement limit of the photodetector, so that basically the temperature during the heat treatment can be accurately measured.
[0056]
The threshold value in the present embodiment is the reflectance R obtained based on the detection limit of the photodetector, and varies and is influenced to some extent by the type of film attached to the back surface and the temperature during heat treatment. Thus, in the present embodiment, the threshold value is assumed to be R = 0.02, but is not limited to these values.
[0057]
In the present invention, the method for calculating the temperature based on the emissivity has been described. However, since the reflectivity can be obtained from the emissivity, the temperature can also be calculated using the reflectivity. It is not limited. Therefore, the reflectance can be measured first, and the temperature can be obtained based on the reflectance.
[0058]
【The invention's effect】
As described above, according to the present invention, when the wafer temperature is irradiated and the wafer temperature is measured based on the reflectance and reflected light intensity, the temperature measurement error can be reduced by changing the temperature measurement method according to the reflectance on the back surface of the wafer. It can be minimized. For example, if the reflectance on the backside of the wafer is too low to exceed the detection limit of the photodetector and it is impossible to measure the emissivity, the temperature can be obtained using the emissivity before heat treatment instead. I can do it.
[Brief description of the drawings]
FIG. 1 is a diagram showing a hot wall type heat treatment apparatus. FIG. 2 is a diagram showing a relationship between a wafer position and a furnace temperature in the hot wall type apparatus. FIG. 3 is a diagram showing a hot wall type heat treatment apparatus. 4] Diagram showing measurement flow in hot wall type device [Fig. 5] Diagram showing relationship between temperature error and emissivity error [Explanation of symbols]
1 Transfer Robot 2 Heater 3 Elevator 4 Pyrometer 5 Photodetector 6 Integrating Sphere 7 Wafer

Claims (5)

In a system that measures the wafer temperature based on the emissivity obtained by irradiating light on the backside of the wafer and the thermal radiation energy from the wafer,
When the emissivity on the back surface of the wafer is outside the detection range of the photodetector, the wafer temperature is measured using the emissivity measured before the heat treatment step. In a system that measures the wafer temperature based on the emissivity obtained by irradiating light on the backside of the wafer and the thermal radiation energy from the wafer,
If the emissivity on the backside of the wafer is within the detection range of the photodetector, measure the wafer temperature using the emissivity measured during the heat treatment process,
When the emissivity on the back surface of the wafer is outside the detection range of the photodetector, the wafer temperature is measured using the emissivity measured before the heat treatment step. 3. The wafer heat treatment method according to claim 1, wherein the photodetector is out of a detection range when the emissivity is 0.98 or more. 3. The wafer heat treatment method according to claim 1, wherein the back surface of the wafer is in a state in which a low reflectance film is exposed. 5. The wafer heat treatment method according to claim 4, wherein the low reflectivity film is made of SiN, TEOS, or SiC.

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