JPH07234163A - Temperature detector for heat treatment apparatus - Google Patents

Abstract

PURPOSE:To optimize the power control of a heating means or the positional setting of a semiconductor wafer in a reaction tube, in measuring the surface temp. of the wafer by a thermocouple in a heat treatment device of the wafer, by reducing the error between a temp. measured value and the actual temp. at the time of processing to the utmost. CONSTITUTION:The thermal contact of the strand 61 (61a, 61b) of a thermocouple 6 is brought into contact with the surface of a semiconductor wafer. The exposed length of the strand 61 exposed from the cover pipe 6 made of alumina of the thermocouple 6 (6A-6C) is set to 40 times or more the diameter of the strand and, for example, when the diameter of the strand is 0.1mm, the exposed length of the strand is set to 4mm or more. By this constitution, even when the temp. rising and falling speed of the wafer is large, the heat transmitting through the strand 61 from the wafer to escape to the cover pipe 62 high in heat capacity is reduced and the error between a temp. measured value and the actual temp. at the time of processing is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature detecting device for a heat treatment apparatus.

[0002]

2. Description of the Related Art As semiconductor devices become finer and more highly integrated, the thickness of each layer of the device is becoming thinner, while semiconductor wafers (hereinafter referred to as "wafers") are also changed from 6-inch size to 8-inch or 12-inch size. Therefore, the development of ultra-thin film technology for large areas has become an important issue. In addition, for example, in the oxide film of the capacitor insulating film, the formation of the gate oxide film, or the diffusion process of the impurity ions, the film quality, the film thickness, and the diffusion depth are greatly affected by the thermal budget (thermal history). It is necessary to keep the heat treatment as small as possible.

Here, in a vertical type heat treatment apparatus which is one of the conventional batch type heat treatment apparatuses, a holder in which a large number of wafers are stacked in a rack is carried into a reaction tube surrounded by a heater to perform heat treatment. However, since the wafer is heated by the heater disposed on the side of the reaction tube, a large temperature gradient is generated between the central portion and the peripheral portion of the wafer when the wafer is rapidly heated, In addition, since a temperature gradient is unavoidable in the position of the reaction tube in the length direction, there is a limit to increase the in-plane uniformity and the inter-plane uniformity (wafer-to-wafer uniformity) in the heat treatment of the wafer. It is extremely difficult to form an ultrathin film having a large area and uniform for manufacturing a device.

From the above, the present inventor has improved the heat treatment furnace of the vertical heat treatment apparatus so that, for example, one wafer is placed on the holder in the reaction tube and carried into the set position, and then the temperature of the heating source is changed. Is being studied, or a method of controlling the temperature of the wafer by changing the height position of the wafer is being studied. According to this method, high uniformity of the in-plane temperature of the wafer can be expected.

By the way, in order to carry out such a method, it is necessary to measure the temperature of the wafer surface extremely accurately in the power control of the heating source and the work of setting the movement pattern of the wafer. In other words, if the temperature of the wafer cannot be accurately grasped, the reliability of the settings themselves such as the power control pattern and the movement pattern of the wafer will be low, and it will not be possible to obtain high in-plane uniformity of the wafer temperature during the actual heat treatment. is there. As a conventional method for detecting the surface temperature of a wafer, as shown in FIG. 7, a thermocouple 1 formed by coating a wire 11 having a wire diameter of 0.1 mm, such as platinum-platinum rhodium, with a coating tube 12 such as alumina. The wire 11 is exposed from the tip of the cladding tube 12 by, for example, about 2 mm, and the tip of the wire 11 (the joining end of the two wires 11a and 11b) is brought into contact with the surface of the wafer W to measure the surface temperature. Was.

[0006]

However, when the temperature of the wafer is rapidly raised or lowered from a certain temperature, for example, when the wafer is raised to a predetermined position near the heating source in the reaction tube, the temperature of the wafer is rapidly raised to the set temperature. However, in this case, if thermocouples are arranged at multiple points on the surface of the wafer and the temperature at each point is measured, the temperature at each point becomes unstable immediately after the temperature rises to around the set temperature, and the temperature at each point becomes unstable. There are variations in temperature between them. This variation in temperature causes the actual temperature of the wafer surface (actual surface temperature when the thermocouple is not mounted on the wafer) to be unstable when the temperature of the wafer is rapidly raised or lowered, and the in-plane non-uniformity. The existence of the uniformity is also one of the causes, but it is conceivable that the temperature detection value of the other thermocouple contains an error with respect to the actual temperature. It is considered that such an error is not so large, but when the heat treatment time is short, the fluctuation of the thermal history at the initial stage of the heat treatment greatly affects the treatment result. For example, since the oxide film used in the next-generation device is very thin, a difference in film thickness of several angstroms becomes a problem. For example, in the oxidation treatment at around 1000 ° C., if the film thickness differs by 1 ° C., the film thickness will differ by 1 angstrom.
There is also a problem in obtaining a shallow PN junction by the impurity diffusion process, and there is a problem that not only the method of heating the wafer but also the temperature measurement error with respect to the actual temperature must be suppressed as much as possible.

The present invention has been made under the above circumstances, and an object thereof is to measure the temperature of the surface to be processed of the wafer with high accuracy, and thereby to make the temperature uniform on the wafer. It is an object of the present invention to provide a temperature detecting device for a heat treatment apparatus capable of performing heat treatment.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in consideration of the fact that the error between the actual temperature and the temperature measurement value when the wafer is actually heat-treated is affected by the thermocouple cladding tube. is there. That is, according to the invention of claim 1, in a heat treatment apparatus for a semiconductor wafer, in a temperature detection device for detecting the temperature of a semiconductor wafer by a thermocouple in which an element wire is covered with a coating tube, the element exposed from the tip of the coating tube. The exposed length of the wire is set to be 40 times or more the wire diameter of the strand.

According to a second aspect of the invention, in the first aspect of the invention, the semiconductor wafer is subjected to a temperature change of 20 ° C./min or more. According to the invention of claim 3, in the invention of claim 1 or 2, a heating region is formed on one end side of the reaction tube of the heat treatment apparatus, and the semiconductor wafer is moved from the other end side of the reaction tube to the heating region. Characterize. The invention of claim 4 is characterized in that, in the invention of claim 1, 2 or 3, the heat treatment performed in the reaction tube is oxidation, diffusion treatment or thermochemical vapor deposition reaction (Chemical vapor deposition).

[0010]

When the tip of the wire of the thermocouple (bonding end of the wire) is brought into contact with the surface of the wafer or when the wire is welded, the sheath of the strand has a large heat capacity, so heat escapes to this sheath. For example, when the heating source is located above the wafer, it is assumed that the radiant heat from above is absorbed by the cladding tube. Therefore, when the temperature of the wafer is rapidly changed, the trackability of the measured temperature value to the actual temperature deteriorates, but by increasing the exposed length of the wire exposed from the cladding tube, the temperature measurement of the cladding tube The influence is mitigated, and by setting the exposed length to be 40 times or more the wire diameter of the strand, the measured temperature value becomes substantially equal to the actual temperature, and uniform heat treatment can be performed. it can.

[0011]

FIG. 1 is a diagram showing the overall construction of an embodiment of the present invention. Reference numeral 2 in FIG. 1 denotes a bottomed cylindrical reaction tube made of quartz, and the reaction tube 2 is arranged in a cylindrical heat insulator 21 with its open end facing downward. A heating means 22, for example, a resistance heating element is provided on the upper side of the reaction tube 2. As the resistance heating element, for example, molybdenum disilicide (M
oSi ₂ ), Kanthal (trade name) wire which is an alloy wire of iron, chromium and aluminum can be used.

A heat control plate 23 made of, for example, silicon carbide (SiC) is arranged between the reaction tube 2 and the heating means 22 so as to face a wafer W described later. The heat control plate 23 is for causing the radiant heat that has entered from the heating means 22 to enter perpendicularly to the surface to be processed of the wafer W, and in order to uniformly heat the entire surface of the wafer W, the outer diameter Is more than twice as large as the wafer W.

At the lower end of the heat insulator 21, there is attached a cooling means 30 which forms a coolant passage through which a coolant such as water passes. Further, a metallic manifold 32 is provided below the reaction tube 2, and a gas supply pipe 31 and an exhaust pipe (not shown) are connected to the manifold 32.
The inner end side of the gas supply pipe 31 extends upward in the reaction tube 2, and the supply port is located diagonally above the wafer W. The manifold 32 has a wafer loading / unloading port (not shown) that is opened / closed by a shutter. At the lower end side of the manifold 32, there is provided a lid 33 that hermetically seals the processing space.

A wafer holder 4 is provided inside the reaction tube 2 at the top of an elevating shaft 51. This wafer holder 4
Is made of, for example, silicon carbide (SiC), and has, for example, 3 to 4 holding projections for holding the wafer W formed at the peripheral edge portion. The elevating shaft 51 penetrates the lid 33 in a gastight manner, for example, via a magnetic seal portion 34 so as to rotate and elevate freely, and the lower end of the elevating shaft 51 is connected to a rotating mechanism 53 provided on an elevating arm 52. Has been done. The lifting arm 52
Is screwed into a ball screw 54 driven by a motor 55, and is configured to be able to move up and down while being guided by a guide rod (not shown) by the rotation of the ball screw 54.

A thermocouple 6 for measuring the surface temperature of the wafer W is provided on the wafer W. In this embodiment, as shown in detail in FIGS. , Three thermocouples 6A to 6C are used so as to measure the temperatures at the three regions of the area between the peripheral portion and the central portion and the central portion of the wafer, respectively. The thermocouple 6 (6A ~
6C) is a wire 6 made of, for example, two kinds of metal, which is made of, for example, platinum-platinum rhodium, in which each tip is connected to form a thermal contact 60.
1 (61a, 61b) and this wire 61 (61a, 61b)
a coating tube 62 made of, for example, alumina for coating b).

The exposed length of the wire 61 exposed from the coating tube 62 is set to be 40 times or more the wire diameter of the wire 61. The wire diameter of the wire 61 is, for example, 0.1 mm
In this case, the exposed length of the wire 61 is 4 mm or more. In this embodiment, the wire 6 is inserted from the tip of the cladding tube 62.
1 extends horizontally and further bends in an L-shape, and as shown in FIG. 3, the length H of the exposed horizontal portion and the length P of the exposed vertical portion are set to 2 mm and 2 mm, respectively. However, the exposed portion of the wire 61 may extend linearly as shown in FIG. 4, and may be in contact with the surface of the wafer W obliquely at a predetermined angle. In this case, the exposed length L of the wire 61 needs to satisfy the above conditions.

Each thermocouple 6 is led out to the control section 7 in an airtight manner from the manifold 32, for example. The control unit 7 has a function of processing the temperature detection signal of the thermocouple 6 to display the temperature of each point of the wafer W on a display (not shown), and controlling the electric power of the heating means 22 and the drive control of the motor 55. . For example, the operator of the heating means 22 may obtain an optimum temperature profile based on the temperature profile of the wafer W obtained from the thermocouple 6 when the wafer W is placed on the holder 5 and moved to a predetermined heating region. A power control pattern and a lifting / lowering pattern of the wafer W (control pattern of the motor 55) are set, and the heat treatment apparatus is operated based on the set patterns.

Next, the operation of the above embodiment will be described. First, the wafer holder 4 is lowered to the position of the manifold 32, the wafer W is placed on the wafer holder 4 from a carry-in / out port (not shown), and the thermocouples 6 (6A to 6C) are respectively attached to the wafer W as described above. Set to the predetermined position. On the other hand, a radiant heat radiated from the heating means 22 through the heat control plate 23 into the reaction tube 2 forms a heating region in the reaction tube 2 which is heated to a completely uniform temperature in the plane of the wafer. ing. Then, after closing the loading / unloading port, the elevating shaft 51 is raised, and the gas as the dummy, for example, N ₂ gas is supplied from the gas supply pipe 31 at the same flow rate as in the actual process.
Supply in. Then, in a certain movement pattern of the wafer W, the surface temperature of the wafer W rises at, for example, 50 ° C./minute and then settles to a constant value. In this case, each thermocouple 6A to 6A is used.
The temperature measurement values of C are uniform as shown in FIG. 5, and the actual temperature during the process is accurately reproduced.

This effect is confirmed by changing the exposed length of the wire 61 and measuring it. That is, when the wire diameter of the wire 61 is 0.1 mm, the exposed length is 2 mm, 3 mm,
The temperature of each thermocouple was set to 5 mm (4 mm, 5 mm, 6 mm), each thermocouple was attached to the surface of a common wafer, and the temperature measurement value was examined at a high heating rate of 50 ° C./sec. Based on the measured temperature of a thermocouple with an exposed length of 4 mm, the variation in the measured values is 2 mm and 3 m in the temperature rising state.
The exposure length of m is -30 ° C to -50 ° C, which is 5
For exposed lengths of mm and 6 mm, it was about several degrees Celsius. In the region where the temperature rises to the stable state, the exposure length of 2 mm and 3 mm is -10 ° C to
The temperature was −20 ° C., and was 1-2 ° C. for the exposed lengths of 5 mm and 6 mm. Note that FIG. 6A and FIG.
3 is a graph showing measured temperature values of thermocouples with exposed lengths of mm and 2 mm.

Therefore, when the exposed length of the thermocouple is 2 mm or 3 mm, the measured temperature value is lower than the actual temperature,
In particular, before the temperature stabilizes at the target temperature, the error is large. Therefore, when the in-plane temperature of the wafer is measured, the error in each measured value is large, whereas if the exposure length is 4 mm or more, it is close to the actual temperature. Therefore, it can be seen that the dispersion of each measured value in the plane of the wafer becomes small.

The reason why the temperature measurement value depends on the exposed length of the wire 61 when the temperature of the wafer W is rapidly increased in this way is that the radiant heat applied to the wafer W rapidly increases. Since the temperature rise of the coating tube 62 having a large heat capacity is delayed as compared with the temperature rise of the surface of the wafer W, when the exposed length of the wire 61 is small, a part of the heat is transmitted from the wafer W through the wire 61. It escapes to the coating tube 62 having a large heat capacity, and thus the surface temperature of the wafer W becomes temporarily unstable. On the other hand, when the exposed length of the wire 61 is large, that is, when the exposed length is 40 times or more the wire diameter of the wire, the heat escaping from the wire 61 to the coating tube 62 becomes small,
In the heating region where the temperature of the portion in contact with the wire 62 is stable, and therefore the temperature distribution in the surface direction of the wafer W is substantially completely uniform, the temperature measurement values of the thermocouples 6A to 6C are uniform. , The error of the measured temperature value with respect to the actual temperature is 1
It becomes as small as / 3 to 1/10. In the above-mentioned embodiment, since the radiant heat is radiated from the heat control plate 23 perpendicularly to the surface of the wafer W, the coating tube 62 is placed at the true position of the heat contact so that the coating tube 62 does not shade the heat contact. It is preferably not located above.

The phenomenon described above also occurs when the temperature of the wafer is rapidly lowered, and according to the experiments conducted by the inventor of the present invention, when the temperature rising or cooling rate of the wafer is 20 ° C./min or more, The effect of exposure length appears.

In the above, the present invention can also be applied to a batch type vertical heat treatment apparatus. FIG. 6 is a diagram showing an example thereof, in which the reaction tube 81 is surrounded by a heat insulator 82, and inside the heat insulator 82, for example, a resistance heating element divided into three in the height direction is formed. Heating means 83a to 83c are provided. Reference numeral 84 denotes a wafer boat that serves as a wafer holder. A large number of wafers W are stacked in a shelf shape and loaded and unloaded by the boat elevator 85. 86
Is a lid, 87 is a gas supply pipe, 88 is an exhaust pipe, and 89 is a controller. And several wafers W of different heights
On the other hand, in order to measure the surface temperature, the thermocouple 6 having the same structure as that of the above-described embodiment is provided.

By measuring the temperature of each wafer W in this manner, the temperature distribution between the surfaces of the wafer W (the temperature distribution between the wafers) can be accurately grasped, and furthermore, each wafer has a plurality of different temperatures. By measuring the temperature at the in-plane position, the in-plane temperature distribution of the wafer W can be accurately grasped. Therefore, based on this measurement result, for example, by setting the power control of each heating means 83a to 83c and improving the wafer boat,
Good heat treatment can be performed.

The present invention has a great effect when an oxidation treatment for obtaining an ultrathin oxide film such as a capacitor oxide film or a gate oxide film for a next-generation device or a diffusion treatment for obtaining a shallow PN junction is performed. However, the present invention can also be applied to an apparatus for performing various heat treatments such as CVD and ashing.

[0026]

According to the present invention, even when the temperature of the wafer is rapidly raised or lowered in measuring the temperature of the wafer, it is possible to obtain a temperature measurement value very close to the actual temperature. On the other hand, uniform heat treatment can be performed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a side view showing a main part of the embodiment of the present invention.

FIG. 3 is a perspective view showing a main part of an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a thermocouple according to an embodiment of the present invention.

FIG. 5 is a characteristic diagram showing temperature measurement values obtained according to an example of the present invention.

FIG. 6 is a characteristic diagram showing temperature measurement values for an example and a comparative example.

FIG. 7 is an overall configuration diagram showing another embodiment of the present invention.

FIG. 8 is an explanatory view showing a part of a conventional temperature measuring device.

[Description of Reference Signs] 2 reaction tube 22 heating means 23 thermal control plate 4 wafer holder W semiconductor wafer 6 thermocouple 61, 61a, 61b strand 62 coating tube 81 reaction tube 83a to 83c heating means 84 wafer boat

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yasushi Yagi 1-24-1 Machiya, Shiroyama-cho, Tsukui-gun, Kanagawa Tokyo Electron Tohoku Co., Ltd. Sagami Office

Claims (4)

[Claims] 1. A heat treatment apparatus for a semiconductor wafer, wherein in a temperature detecting device for detecting the temperature of a semiconductor wafer by a thermocouple in which an element wire is covered with a coating tube, the element wire exposed from the tip of the coating tube is exposed. A temperature detecting device for a heat treatment device, wherein the length is set to be 40 times or more the wire diameter of the strand. 2. The temperature detecting device for a heat treatment apparatus according to claim 1, wherein the semiconductor wafer is subjected to a temperature change of 20 ° C./min or more. 3. The heat treatment according to claim 1, wherein a heating region is formed on one end side of the reaction tube of the heat treatment apparatus, and the semiconductor wafer is moved from the other end side of the reaction tube to the heating region. Temperature detection device for equipment. 4. The temperature detecting device for a heat treatment apparatus according to claim 1, 2 or 3, wherein the heat treatment performed in the reaction tube is oxidation, diffusion treatment or thermochemical vapor phase reaction treatment.