JPH0239525A - Heat treatment device for semiconductor - Google Patents

Abstract

PURPOSE:To make it possible to do temperature control to make the effective amounts of heat treatment uniform by installing a temperature transducer, a mechanical controller, and a main controller to control a temperature controller. CONSTITUTION:After inputting treatment conditions into a main controller 20, a treatment start command is input. According to this, a mechanical controller 22 loads a wafer 1 on a jig 8 and inserts it into a reaction tube 2. Also, a temperature transducer 23 takes in the values of a radiation thermometer 10 and a thermocouple 14 at that time and calculates emissivity by the signals which are issued from the mechanical controller 22 at the same time with the insertion of the wafer 1. And when it reached the treatment amounts being set, it judges that as heat treatment completion and instructs a mechanical controller 22 to draw out wafer 1. The drawn out wafer 1 is unloaded by the jig 8, and the mechanical controller 22 judges presence of another wafer 1 to be treated next, and in the case that the wafer 1 is present it repeats treatment from the wafer loading, and in the case that the wafer is not present it finishes the treatment. Hereby, uniform heat treatment can be done.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus for performing semiconductor heat treatment such as diffusion, annealing, and oxidation, and in particular, by performing suitable wafer radiation temperature measurement in a single-wafer type heat treatment apparatus. , relates to a semiconductor heat treatment apparatus that performs uniform wafer heat treatment.

[Conventional technology]

Batch-type semiconductor heat treatment equipment, typified by diffusion equipment, is
Approximately 25 to 100 wafers placed on a heat-resistant jig are inserted into a reaction tube and heated with a heater to perform heat treatment. The heater is usually divided into multiple parts, the temperature is measured with a thermocouple, the amount of heat generated is determined by a temperature control system (PID control) so that this becomes the target temperature (set temperature), and the power is supplied with a cable to control the wafer. 6 In addition, the set temperature of the heaters at both ends is increased to increase the amount of heat generated, and the temperature uniformity region (
The wafer is heat-treated at a uniform temperature within this soaking period.

[Problem to be solved by the invention]

In conventional batch heat treatment, the temperature history during insertion and withdrawal differs between the wafers that enter the reaction tube first and the wafers that enter the reaction tube later. Therefore, as the pattern becomes finer and the heat treatment time becomes shorter, the influence of insertion and withdrawal becomes relatively large, and variations in the effective amount of heat treatment become a problem.

On the other hand, single-wafer heat treatment equipment, which processes one or two wafers repeatedly, can make the temperature history of the wafer uniform, and has an advantage in terms of uniformity of heat treatment amount in a short processing time of several minutes. is very large.

However, in these short-time heat treatments, ffNJ is used to match the heater temperature to the target set temperature, as in the aforementioned diffusion device.
# alone makes it difficult to ensure temperature MW uniformity of the wafer. In other words, in single-wafer heat treatment, the process of repeatedly inserting cold wafers and withdrawing them when the temperature approaches the furnace wall temperature is repeated. This is because they will not be able to respond. Therefore, in a single wafer heat treatment apparatus, it is necessary to directly measure the temperature of the wafer and control the temperature based on this measurement.

An object of the present invention is to provide a semiconductor heat treatment apparatus that can perform temperature control to make the effective heat treatment amount uniform.

[Means to solve the problem]

The above purpose was to develop a mechanism for inserting the wafer into the reaction tube at high speed, and a mechanism for inserting the wafer into the reaction tube, and a heat radiation of the wafer (hereinafter, a range of 1 μm where no wafer transmission occurs).
(refers to the measurement wavelength of the radiation thermometer selected below m). A radiation thermometer, a thermometer that measures the temperature of the furnace wall (the part that emits thermal radiation that enters the radiation thermometer after being reflected on the wafer surface), and a thermometer that measures the temperature of the wafer from the output of this radiation thermometer and the furnace wall thermometer. This is achieved by providing a temperature converter for determining the wafer, a mechanical controller for controlling the wafer insertion mechanism, a temperature controller for controlling the amount of heat generated by the heater, and a main controller for controlling the temperature converter, the mechanical controller, and the temperature controller.

[Effect]

Generally, in wafer radiation temperature measurement in a semiconductor heat treatment apparatus, the thermal radiation received by a radiation thermometer can be expressed as follows.

Et=A・[w・E('],'-)+Ell
・=(1) Et: Total heat radiation received by the radiation thermometer A: Constant EW depending on the characteristics of the optical element placed in the measurement optical path: Wafer emissivity E(T): Heat radiated by a black body at temperature T Radiation Eo: Disturbance radiation Here, disturbance radiation refers to, for example, thermal radiation from the inner wall of the reactor, which is incident on the radiation thermometer after being reflected by the surface of the wafer or reaction tube. Therefore, in order to accurately measure the wafer temperature, it is necessary to correct the disturbance radiation and the wafer emissivity to obtain E('r,).

Hereinafter, the operation of each component of the single wafer heat treatment apparatus will be explained in sequence.

The radiation thermometer is installed to receive the wafer thermal radiation that has entered a predetermined location within the reaction tube. At this time, the holding angle of the wafer and the inclination of the radiation thermometer are adjusted so that the source of the disturbance radiation is the furnace wall where the temperature is relatively uniform in the furnace,
Furthermore, a thermometer is provided to measure the temperature of this part. The thermometer for the furnace wall may be a thermocouple or a radiation thermometer (
In that case, the emissivity of the furnace wall can be evaluated as 1).

By adjusting the optical system in this way, equation (1) can be transformed as follows.

Et=A・εwsE(Tw)+B・ρ+r”E(Th)
'・' (2) ρW (=1-2w): Wafer reflectance (no transmission) Th: Furnace wall temperature B: Constant depending on the characteristics of the optical element placed in the measurement optical path Also, consider the surface reflection of the reaction tube If you need it,
The following formula is obtained.

Et=A-EW-E(Tw)+B-p#-E(Th)+
C-ps-E(Th') - (3) ρS: Surface reflectance of the reaction tube (assumed to be known) 'rh': Temperature of the reactor wall that emits disturbance radiation due to reaction tube surface reflection C: Placed in the measurement optical path Here, when the room temperature wafer is inserted into the reaction tube at high speed,
When the wafer stops at a predetermined position, the temperature of the wafer has not yet risen significantly (for example, the wafer is placed in a 1000°C furnace for 200°C).
300 when inserted in about 5 seconds at a speed of 0++n/s
~400℃ or less). Since the thermal radiation emitted by the wafer increases exponentially as the temperature rises, the thermal radiation received by the radiation thermometer immediately after inserting the wafer is expressed by the formula (2
).

The first term on the right side of (3) can be ignored (E(TV) 0), and an output only due to disturbance radiation can be obtained.

Using this, calculate the wafer emissivity as follows.

The disturbance radiation is roughly evaluated and corrected based on the furnace wall temperature, enabling accurate wafer radiation temperature measurement. First, the mechanical controller sends the timing for inserting the wafer to the temperature converter via the main controller, and the temperature converter takes in the outputs of the radiation thermometer and furnace wall thermometer at that time. Next, the wafer emissivity is determined as follows using equations (2) and (3) with each measured value as E tQ and Thot Tho'.

...(5) Wafer emissivity correction is performed using this value, but when processing multiple wafers of the same type, the above calculation only needs to be performed for the first wafer, and subsequent wafers with the same emissivity Can be corrected by value. Now ε1. Now that the value of ρ is known, the next step is to take in the outputs of the radiation thermometer and the furnace wall thermometer at appropriate time intervals, and calculate E(TV) based on equations (2) and (3). Furthermore, this is converted into a temperature T based on the characteristics of the radiation thermometer.

In this way, appropriate correction can be made for changes in disturbance radiation due to a decrease in furnace wall temperature immediately after inserting a cold wafer and subsequent recovery.

Furthermore, the main controller attempts to equalize the amount of wafer heat treatment based on the wafer temperature determined above. That is,
The wafer temperature T obtained for each measurement is converted into the corresponding heat treatment amount (in the case of oxidation: oxide film thickness, annealing: sheet resistance, diffusion: impurity concentration distribution) in the main controller, and this value is converted for each wafer. Integrate. Then, when a predetermined amount of heat treatment is reached, a command is issued to the mechanical controller to pull out the wafer, thereby making it possible to perform uniform heat treatment. In this case, the heat treatment time for the wafer will change accordingly, but conversely, with the treatment time constant, the appropriate heater temperature setting for the next wafer treatment can be calculated from the deviation between the predetermined heat treatment amount and the measured value. Therefore, it is easy to make the heat treatment uniform by predictive control such as rewriting the settings of the temperature controller.

As described above, since there is no variation in the amount of heat treatment between wafers, the yield can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 schematically shows a cross section of a heating furnace of a single wafer type heat treatment apparatus to which the present invention is applied, and continuously shows the flow of signals between each controller and temperature converter.

The structure of the heating furnace includes flat heaters 4A to 4 divided into multiple parts.
A heat insulating material 7 is provided outside C, a soaking tube 3 (made of SiC) is provided inside the flat heaters 4A to 4C, and a reaction tube 2 (made of quartz) is provided inside the same.

The flat heaters 4A to 4C are connected to the PI by the temperature controller 21.
D control, an appropriate calorific value is determined from the heater temperature measured by the control thermocouple 5 and the set temperature, and power is supplied through the cable 6. The wafers 1 are usually held almost vertically, singly or in pairs, by a jig 8 with one end fixed to a transport mechanism 9 controlled by a mechanical controller 22, and are inserted into the reaction tube 2 from the F side to undergo heat treatment. conduct.

The optical path of the thermal radiation emitted by the wafer 1 is bent by the quartz prism 11 and the mirror 12 held by the prism stand 13, and then the radiation thermometer 10 ( Measurement wavelength 0.9nm
, half-value IIJ 100 nm or less). Further, a thermocouple 14 is provided to measure the temperature of the soaking tube 3 facing the wafer 1, and the value of this thermocouple 14 is used as the temperature of the furnace wall, which is the source of the disturbance radiation described in the first section.

FIG. 2 shows the optical path of thermal radiation received by the radiation thermometer 10. The solid line is the thermal radiation of the wafer 1, and the dotted line is the disturbance radiation.

The jig 8 holds the wafer 1 tilted several degrees in a certain direction. This stabilizes the posture of the wafer 1 and prevents the position of the furnace wall that emits disturbance radiation from moving (the furnace wall, which has approximately the same temperature as the measurement position of the thermocouple 14, is the generation position of the disturbance radiation). That is the purpose. In addition, although the thermocouple 14 should originally measure the temperature of the furnace wall 3A, in this embodiment, the temperature of the furnace wall 3B on the sending side is considered to be almost the same, so it is necessary to measure the temperature of the furnace wall 3B. I made it.

Returning to FIG. 1, a radiation thermometer 10 and a thermocouple 14 are connected to the temperature converter 23, and the temperature of the wafer 1 is calculated from these signals by correcting disturbance radiation and correcting the wafer emissivity. The main controller 20 includes a temperature controller 21. Mechanical controller 22. It is connected to the temperature converter 23 and manages these devices comprehensively.

FIG. 3 shows an example in which the functions of these devices related to the present invention are extracted and described along the flow of processing, which will be explained in order.

First, prior to heat treatment, processing conditions are input to the main controller 20. For example, the setting items include processing temperature, processing time, i-degree monitoring conditions, and gas pattern. The main controller 20 selects the temperature controller 21 . Main controller 22. Temperature converter 2
In response to the information, each device performs initial settings or condition settings for heat treatment, and then enters a standby state.

Next, in the standby state, a processing start command is input to the main controller 2o. In response to this, the mechanical controller 22 loads the wafer 1 onto the jig 8 and inserts it into the reaction tube 2. Further, the temperature converter 23 receives the values of the radiation thermometer 10 and the thermocouple 14 at that time in response to a signal issued from the mechanical controller 22 at the same time as the wafer 19 is inserted, and calculates the emissivity. The basic equation for calculation of wafer emissivity and subsequent temperature monitoring is based on equation (3), and the transmittance of the reaction tube 29 and the quartz prism 11.

Considering the reflectance of the mirror 12, T h '=
The following formula was used considering T h.

Et=(τg'τp'ρJ"εw-E(Tw)+rp'
ρ, (ρw+ρ5)E(Th)...(6) ρs: Reaction tube permeability (0,067at0.9 prr
+) τ5 (=1-ρs): Transmittance of reaction tube (=0.93
3ato, 9μm) τP: Transmittance of quartz prism (=Q, 933゜ato
, 9 μm) ρ, : Mirror reflectance (=0.865 at 0.9 μm) If the output of the radiation thermometer 10 immediately after inserting the wafer is Eto, and the output of the thermocouple 14 is ThO, the wafer insertion speed is fast. For E (TV)<: E (TI,)
holds, and the emissivity can be calculated as follows.

Thereafter, the temperature converter 23 during wafer heat treatment uses this emissivity ε,
The wafer temperature is calculated from equation (6) using The main controller 20 integrally calculates the amount of heat treatment of the wafer 1 to date from this value, determines that the heat treatment is complete when the set amount of treatment is reached, and instructs the mechanical controller 22 to pull out the wafer 1.

The pulled out wafer 1 is unloaded from the jig 8,
The mechanical controller 22 determines whether or not there is a wafer 1 to be processed next. If there is a wafer 1, the process is repeated from wafer loading, and if there is no wafer 1, the process is terminated. Further, after setting the heat treatment conditions, the temperature controller 21 always controls the temperatures of the heaters 4A to 4C to a constant value.

The above was a case where the processing time of the wafer 1 was changed to make the amount of heat treatment uniform. When the treatment time is exactly the same and the set temperature of the heater is changed, the heat treatment flow is as shown in FIG. 4. In other words, the setting of heat treatment conditions and the 2m degree monitor for wafer insertion are the same as in the previous case, but the integral value of the heat treatment amount is no longer compared with a predetermined value for each measurement, and immediately after withdrawal, The next heater setting temperature is determined from the deviation between the predetermined amount of heat treatment and the measured value. The processing time is always constant, and if the amount of heat treatment this time is not enough, the set temperature of the heater will be increased the next time, and if it is too much, the set temperature will be lowered.

In order to convert the wafer temperature into the amount of heat treatment, there is a relational expression appropriate for each treatment, so this can be used. Furthermore, if the relationship between the temperature and the amount of heat treatment is known through experiments, simulations, etc., that relationship may be stored as data in the main controller 2o and referred to.

Next, the radiation thermometer 1o obtained in the above heat treatment
, @mm Value converted from 4 contact outputs to temperature without correction,
FIG. 5 shows a typical pattern of the wafer temperature obtained by adding and correcting the temperature. The solid line is the radiation thermometer 10. The broken line is the thermocouple 14. - The dashed line indicates the wafer temperature. Immediately after the wafer is inserted, the output of the radiation thermometer 10 suddenly decreases to a minimum value, and then gradually increases. This minimum value is the output due to disturbance radiation. Further, the furnace wall temperature measured by the thermocouple 14 also decreased by 20 to 30'Ca degrees immediately after inserting the wafer, and gradually recovered. (Temperature monitoring is stopped when there are no wafers in the furnace, but if this continues, a phenomenon will occur in which there will be a step in the measured value when the wafer is pulled out, as shown in Figure 5.This occurs at the moment the wafer is pulled out.) (This is because the temperature of the furnace wall is measured.) The value of disturbance radiation due to this temperature change changes as shown in the lower part of Fig. 5, but after proper correction is made using equation (6), Correct wafer temperature is required.

Finally, we will discuss the validity of the wafer emissivity values obtained using the method described above. The inventors found that through the interference effect of thin films formed on the wafer.

It was confirmed that the emissivity value, which changes sinusoidally, can be estimated using the following formula (the formula for a single-layer thin film, and a combination of these for multi-layer thin films).

...(8) λ ρl : Reflectance on the thin film surface ρ2 : Reflectance at the boundary between the thin film and the base 0 : Angle between the measurement direction of the radiation thermometer and the wafer normal λ : Measurement wavelength of the radiation thermometer n : Refractive index of film d: Thickness of thin film Here, ρ1 is determined from Fresnel's formula as follows.

...(9). . 8θ−Shihyaku:πn”a ””cosfJ+ππ=ShiRpz+Rs” ρ (This formula is also effective when calculating the transmittance of a quartz prism and a quartz reaction tube, taking into account the surface reflection.) Also, ρ1 The refractive index is known for (oxide film S 1Oz
= 1.45), and was determined through experiments using samples of wafers with various film thicknesses.

Specifically, in the experiment, the temperature uniformity was 1000℃±0.5
A wafer with a thermocouple glued to it is inserted from the back side into a furnace at °C.
A radiation thermometer was set to measure the temperature from the furnace mouth side to the opposite side to which the thermocouple was attached.

In this method, if the thermocouple indicates approximately the true temperature of the wafer and the wafer is directly facing the radiation thermometer (the wafer normal and the measurement optical path of the radiation thermometer match), it will receive thermal radiation from only the wafer. Yes (the wafer has a mirror surface). Therefore, the wafer emissivity is determined as follows.

ε,': Wafer emissivity E obtained from experiment: Output of radiation thermometer "rw': From experiment at wafer temperature measured by thermocouple or higher, n=1°45.ρ1=0.034 for oxide film.
We obtained (il) ρz=0.16.

As a result of the above, if the thickness of the oxide film is known, the emissivity of the wafer can be determined. For example, in the case of 6230 people, ε,=0.
704.

On the other hand, the estimated value of the wafer emissivity according to the present invention is as follows. The radiation thermometer 10 used had the following characteristics.

■: Output of the temperature T (K) of the radiation thermometer 10 relative to the black body (proportional to thermal radiation) A = 960.3228 x 1. O-'B=
-2,56976X 10-'C=6.804135X
Since 105 Cz = 0.014388 V(T)ccE(T), from equation (7), EtO
Letting the output for Vto be Vto.

In addition, when we conducted an experiment on the wafer on which the oxide film of the 6230 people described above was formed, we obtained Vro = 0.73274 (V) to = 949.0 (T:), and the ρ illusion τr entered in equation (6) , the emissivity is calculated from equation (12) using the value of ρS, ε1=0.6
It becomes 97. From the above results, it can be estimated that the emissivity estimation error according to the present invention is within about ±1%.

〔Effect of the invention〕

According to the present invention, it is possible to accurately correct the emissivity of a wafer in a single-wafer type heat treatment apparatus, and furthermore, it is possible to accurately correct the emissivity of a wafer, and furthermore, the disturbance caused by changes in furnace wall temperature when wafers are continuously inserted into and pulled out of the furnace for processing. Since radiation fluctuations can be properly predicted, accurate wafer temperature measurements can be made at all times. Furthermore, by directly measuring the temperature of the wafer, it becomes easier to adjust the heat treatment time or change the heater temperature setting, and uniform heat treatment becomes possible, which can be expected to improve yield.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a cross section of a heating furnace of a single-wafer type heat treatment apparatus which is an embodiment of the present invention, and a diagram showing the flow of signals between each controller, and Fig. 2 is a diagram showing the heat radiation received by a radiation thermometer constituting the present invention. FIGS. 3 and 4 are flowcharts of heat treatment according to the present invention, and FIG. 5 is a diagram showing outputs of a radiation thermometer and a furnace wall thermometer and changes in wafer temperature during heat treatment. 1... Wafer, 2... Reaction tube, 3... Soaking tube, 4
-1 to 4-3... Heater, 5... Control thermocouple, 6
...Cable, 7.Insulation material, 8.Jig, 9.
...Transportation mechanism, 1°...Radiation thermometer, 11...Quartz prism, 12...Mira 13...Prism stand,
14...Thermoelectric body for furnace wall, 20...Main controller, 21...Temperature controller, 2-2...Mechanical controller, 23...Temperature"JJ31 Figure JO...-Ekishotadado S Tenneri Carriedou Mekadai Senboku J, L (°C)

Claims (1)

[Claims] 1. In a semiconductor heat processing apparatus that has a heating furnace having an opening for loading and unloading the wafer, a jig for holding the wafer, and a wafer transport mechanism to which this jig is fixed, the heat radiation of the wafer inserted into the heating furnace is A radiation thermometer that receives light; a thermometer that measures the temperature of the part of the furnace wall of the heating furnace where the thermal radiation emitted from the wall is reflected on the wafer surface and then enters the radiation thermometer; A temperature converter that calculates the true temperature of the wafer by correcting the wafer emissivity and the effect of reflection of thermal radiation on the wafer surface from the output of A temperature control controller that integrally calculates the amount of wafer heat treatment from the true temperature of the wafer output from the temperature converter and controls the temperature of the wafer drawer and heating furnace based on this. A semiconductor heat treatment apparatus characterized by comprising: