JP2008010883A - Method and apparatus for heat treatment by light irradiation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce stresses applied to an object to be heated by reducing temperature variation thereof by giving distributed light-irradiation intensity in a temperature raising step (an open-circuit control step) after starting the light irradiation. <P>SOLUTION: A method for heat treatment by light irradiation comprises a step for supporting the object 103 to be heated in a vessel and heat-treating the object 103 to be heated by a plurality of light-irradiation heating means 101 provided with a planar configuration and facing a surface of the object to be heated 103. In the step of raising the temperature of the object 103 to be heated by light irradiation from the light-irradiation heating means 101, the object 103 to be heated is irradiated with a light having such a planar light-intensity distribution as to make the maximum temperature difference within the surface of the object to be heated 70°C or lower. As a consequence, the temperature variation within the object 103 to be heated can be reduced in the open-circuit control step after the start of the light irradiation. Thereby, the stresses can be reduced; strains, deformations, bows, cracks and the like can be eliminated; characteristics fluctuations of the semiconductor devices formed in the object 103 to be heated can be suppressed; and reliability failures can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light irradiation heat treatment method and a light irradiation heat treatment apparatus in a manufacturing process of a semiconductor device.

  In the semiconductor manufacturing process, the lamp type light irradiation heat treatment apparatus, for example, implantation for threshold control, activation of impurities after ion implantation of source / drain, silicidation based on a refractory metal film, metal silicide Used for short-time heat treatment such as low resistance. A typical configuration of this type of heat treatment apparatus uses a large number of lamps to heat a plate-shaped object to be heated from both sides or one side thereof. The lamps are opposed to the surface of the object to be heated, and a large number of lamps are arranged with a uniform density at a distance close to the surface. While the heated object such as a semiconductor substrate is being heated at a substantially constant temperature, the heat treatment apparatus uses a plurality of pyrometers installed on both sides of the heated object or in the vicinity of the one surface. The wavelength of the electromagnetic wave radiated from the heated object is measured, converted into a temperature, and feedback controlled to the light irradiation intensity of the lamp so as to maintain the heated object at a predetermined temperature. Thus, the part which feeds back the measured temperature by a pyrometer and controls light irradiation intensity | strength is called a closed circuit control process. This closed circuit control process works effectively above a certain temperature at which sufficient radiation intensity can be obtained from the object to be heated. This temperature is usually 300 ° C. to 600 ° C. or higher.

  On the other hand, in the initial stage of starting the heat treatment of the object to be heated by the light irradiation heat treatment apparatus, the temperature of the object to be heated is controlled from 300 ° C. to 600 ° C. or higher at a constant light irradiation intensity that can be controlled in the closed circuit control process. Although there is a step of raising the temperature, this process is called an open circuit control process. As described above, the light irradiation heat treatment includes the open circuit control process and the closed circuit control process.

Also, in the light irradiation heat treatment process, since the temperature is raised to a high temperature in a short time, stress is applied to the object to be heated, but consideration has been given to alleviate this. For example, Patent Documents 1 to 4 describe such techniques. Yes.
JP-A-11-214323 JP-A-9-246200 JP-A-3-218624 JP 2004-31842 A

  However, in the above conventional technique, in the open circuit control process immediately after the start of light irradiation in the light irradiation heat treatment apparatus, the surface of the object to be heated such as a semiconductor substrate is used to rapidly heat the object to be heated with a constant light irradiation intensity. A temperature distribution is generated because the temperature rise rate generally differs depending on the position of the inside. Therefore, the heated body is stressed, and distortion, distortion, warpage, cracking, etc. occur. Further, in some cases, there is a problem that crystal defects may enter the object to be heated, causing variations in characteristics of semiconductor elements formed on the semiconductor substrate that is the object to be heated, and further causing poor reliability.

  Therefore, the object of the present invention is to provide a distribution in the light irradiation intensity of the open circuit control process according to the specific resistance related to the thermal conductivity of the material to be heated, and to vary the temperature variation of the object to be heated when the temperature rises. Provides a light irradiation heat treatment method and light irradiation heat treatment apparatus that can reduce the stress applied to the object to be heated, and can produce highly reliable semiconductor devices that are free from distortion, distortion, warping, cracking, etc. It is to be.

  In order to solve the above-mentioned problem, a light irradiation heat treatment method according to claim 1 of the present invention is a planar light irradiation method in which a heated object is supported in a container and provided to face one surface of the heated object. A light irradiation heat treatment method for heat-treating the object to be heated by a heating means, wherein in the step of increasing the temperature of the object to be heated by irradiating light from the light-irradiation heating means, a maximum temperature difference within the surface of the object to be heated The object to be heated is irradiated with light having a planar light intensity distribution such that the temperature becomes 70 ° C. or less.

  The light irradiation heat treatment method according to claim 2 is the light irradiation heat treatment method according to claim 1, wherein after the step of increasing the temperature of the object to be heated, the light irradiation heating means has a uniform intensity in a plane. A step of irradiating the object to be heated with heat having heat treatment.

  The light irradiation heat treatment method according to claim 3 is the light irradiation heat treatment method according to claim 1 or 2, wherein the object to be heated is circular, and the planar light intensity distribution from the light irradiation heating means is concentric. Distribution.

  The light irradiation heat treatment method according to claim 4 is the light irradiation heat treatment method according to claim 1 or 3, wherein the object to be heated is made of a semiconductor substrate.

  The light irradiation heat treatment apparatus according to claim 5 is a planar support provided to face a surface of a heated body supported by the support, and a support that supports the heated body provided in the container. Light irradiation heating means, temperature measuring means provided opposite to the other surface opposite to the one surface of the heated object, and when raising the temperature of the heated object, the maximum in the heated object plane Light intensity control means for controlling the light irradiation intensity distribution in the plane of the light irradiation heating means so that the temperature difference becomes 70 ° C. or less.

  The light irradiation heat treatment apparatus according to claim 6 is the light irradiation heat treatment apparatus according to claim 5, wherein the light irradiation heating means includes an assembly in which a plurality of heating lamps are arranged in a plane. The aggregate was divided into a plurality of planar areas, and each area could be set to an independent light irradiation intensity.

  The light irradiation heat treatment apparatus according to claim 7 is the light irradiation heat treatment apparatus according to claim 6, wherein the object to be heated is a semiconductor substrate, and the assembly of the heating lamps is arranged in a plurality of concentric areas in a plane. It is divided.

  According to the light irradiation heat treatment method of the first aspect of the present invention, the temperature variation of the object to be heated can be reduced in the open circuit control step after the start of light irradiation. Thereby, stress can be reduced, there is no distortion, distortion, warping, cracking, etc., and fluctuations in the characteristics of the semiconductor device built in the object to be heated can be suppressed and reliability defects can be reduced.

  In claim 2, since the step of raising the temperature of the object to be heated includes the step of irradiating the object to be heated with light having a uniform intensity in a plane from the light irradiation heating means, Therefore, it is possible to perform a closed circuit control step of controlling the light irradiation intensity by feeding back the measured temperature so as to maintain a predetermined temperature at which a sufficient radiation intensity can be obtained.

  In the third aspect, since the object to be heated is circular and the planar light intensity distribution from the light irradiation heating means is a concentric circular distribution, the light intensity distribution corresponding to the distance from the center of the object to be heated is Can be formed.

  According to the fourth aspect of the present invention, since the object to be heated is made of a semiconductor substrate, it can be implemented in the manufacturing process of the semiconductor device.

  According to the light irradiation heat treatment apparatus of the fifth aspect of the present invention, the temperature variation of the object to be heated can be reduced by the light irradiation intensity control means. Thereby, stress can be reduced, there is no distortion, distortion, warping, cracking, etc., and fluctuations in the characteristics of the semiconductor device built in the object to be heated can be suppressed and reliability defects can be reduced.

  According to a sixth aspect of the present invention, the light irradiation heating means is composed of an assembly in which a large number of heating lamps are arranged in a plane, and the assembly of heating lamps is divided into a plurality of planar areas, and each area is independent of each other. Since the light irradiation intensity can be set, the light intensity to be irradiated can be automatically set for each lamp collection area so that the distribution of the light irradiation intensity of a large number of lamp sets is generated.

  According to the seventh aspect of the present invention, the object to be heated is a semiconductor substrate, and the assembly of the heating lamps is divided into a plurality of concentric areas in a plane, so that the light intensity distribution corresponding to the distance from the center of the object to be heated Can be formed.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of a lamp type light irradiation heat treatment apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, this light irradiation heat treatment apparatus has a support 102 that supports a heated body 103 provided in a container, and one surface of the heated body 103 supported by the support 102. Based on the provided planar light irradiation heating means 101, the temperature measuring means 104 provided opposite to the other surface opposite to the one surface of the heated object 103, and the specific resistance of the heated object 103 And a light irradiation intensity control means for controlling the light irradiation intensity distribution in the plane of the light irradiation heating means 101 so that the temperature measured by the temperature measuring means becomes a predetermined temperature.

  In this case, a large number of cylindrical lamps (light irradiation heating means) 101 for heating and heating the object to be heated, particularly a plate-like substrate, are arranged in a plane in the apparatus, and the object to be heated support 102 The object to be heated 103 is supported by and faces a large number of lamps 101. This support body 102 only supports the heated body 103 at its very periphery, and the back surface of the heated body 103 is exposed.

  A plurality of pyrometers (temperature measuring means) 104 for measuring the temperature are installed facing the lamp 101 with the heated body 103 interposed therebetween. The pyrometer 104 measures the wavelength emitted by the heated object, and converts the temperature of the heated object from the measured wavelength value. An inert gas flows from the inert gas inlet 105 along the surface of the heated object 103 and is discarded from the inert gas outlet 106, and an exhaust pump 107 is connected to the end of the inert gas exhaust port 106. Yes. Further, a mechanism for rotating the heated object 103 together with the support 102 during the light irradiation heat treatment is provided.

  FIG. 2 shows a plan layout of lamps in the light irradiation heat treatment apparatus of FIG. In FIG. 2, a plurality of small circles indicate the arrangement of the lamps, and the numbers 1 to 12 described in the circles indicate that there are a total of 12 areas in which the power supplied to the lamp 101 can be controlled independently. That is, the lamp 101 in the heat treatment apparatus according to the embodiment of the present invention is configured so that its power can be controlled independently in 12 regions. A circle 108 indicates a position when the diameter of the semiconductor substrate 8 is 8 inches as the heated body 103 placed facing the lamp 101, and a circle 109 indicates the outer edge position of the heated body support 102. .

  The light irradiation heat treatment method of the embodiment of the present invention using the light irradiation heat treatment apparatus having the above configuration will be described. That is, an open circuit control step for raising the temperature of the object to be heated 103 at a constant light irradiation intensity up to a temperature controllable by the pyrometer 104, a wavelength at which the object to be heated 103 radiates is measured by the pyrometer 104, and a value of the wavelength A closed circuit control step of converting the temperature of the object to be heated 103 and adjusting the light irradiation intensity of the lamp 101.

  Specifically, when the object to be heated 103 is a semiconductor substrate, the independent power control region of the heating lamp is divided into three as shown in FIG. That is, the light irradiation intensity distribution of the lamp is divided into three regions. A circle region 203 having a radius 201 (about 80% of the substrate radius of the 8-inch aperture) that is inside the opposite substrate periphery and having a distance 201 from the substrate center, and that is inside the substrate periphery; and An area 204 other than the area 203 and an external area 205 of the substrate. The radius 202 is substantially the same as the outer periphery of the 8-inch caliber substrate. Thus, the to-be-heated body 103 is circular, and the planar light intensity distribution from the light irradiation heating means is a concentric distribution.

  When the substrate is actually heat-treated, if the specific resistance of the substrate (silicon) is 1 Ωcm or more, in the open circuit control step after the start of light irradiation, as shown in FIG. In the area 205, the same power is applied to the lamps in these areas so as to have the same light irradiation intensity, and the light irradiation intensity in the area 203 is made larger than those in the areas 204 and 205. Further, when the specific resistance of the substrate (silicon) is smaller than 1 Ωcm, the light irradiation intensity is set to the region 203, the region 204, and the region 205 as shown in FIG. Apply the same power to each lamp so that it is constant in all areas.

  FIG. 5 is a graph showing a change in temperature with time of an object to be heated by a conventional heat treatment. As in the prior art, the same uniform power is input to all of the many lamps 101 in FIG. 1, and the substrate is irradiated with light for heating to obtain a uniform light intensity distribution as shown in FIG. 4B. The time change of the temperature rise of the obtained substrate is shown. The horizontal axis of the graph is the light irradiation heat treatment time, and the first axis of the vertical axis is the temperature of the substrate measured by measuring the wavelength radiated by the heated substrate with the pyrometer 104 shown in FIG. T6 is a symbol indicating a pyrometer installed at a position facing the center and the periphery of the substrate, respectively. The measurement positions of T1 and T6 are shown in FIG. T1 corresponds to the temperature at the center of the substrate, and T6 corresponds to the temperature at the periphery. The black circles in the figure indicate the positions of pyrometers attached to the apparatus, and T1 to T6 indicate pyrometer symbols. The second axis of the vertical axis is the temperature difference between the highest temperature portion and the lowest temperature portion in the substrate plane, and this is indicated as delta. The material used is a CZ-Si substrate (specific resistance: 1-10 Ωcm), which is a substrate that is generally widely used for manufacturing semiconductor devices.

  In the open circuit control process, when the light irradiation intensity distribution shown in FIG. 4B is used as in the prior art, as shown in the measured temperature of 0 to 15 seconds in FIG. Become. This is because a sudden temperature rise occurs in the substrate and mechanical stress is applied, and the substrate is distorted. As a result, the substrate jumps on the support 102 in FIG. Leakage from the gap and direct incidence on the pyrometer 104 increased the ambient temperature (T6). Here, light leakage occurs at 4 seconds after the start of light irradiation.

  FIG. 7 shows a schematic diagram when such a situation occurs. Multiple lamps 501, heated object support 502, multiple pyrometers 503, heated object in normal position 504, heated object 505 after being distorted and bounced, The upper lamp light leaking from the gap between the supports is 506. In this way, the light 506 is incident on the pyrometer T6 located in the vicinity, and a temperature higher than the center is measured.

  Therefore, the temperature measured here is not the true temperature of the substrate, but the temperature erroneously measured due to the leakage of the lamp light. In this state, the measured temperature cannot be accurately fed back to the input power control to the lamp. It will be. Since this temperature variation is caused by distortion of the heated object, it can also be used as an index for determining the presence or absence of stress.

  On the other hand, FIG. 8 is a graph showing a change with time of the temperature of the object to be heated by the heat treatment according to the embodiment of the present invention. When the substrate heat treatment method according to the embodiment of the present invention is used, that is, in the open circuit control step after the start of light irradiation, the multiple lamps 101 in the light irradiation heat treatment apparatus of FIG. A change in substrate temperature when power control is performed so as to obtain an intensity distribution is shown. The semiconductor substrate used in the experiment of FIG. 8 has a specific resistance of 1-10 Ωcm, as in FIG. FIG. 8 shows that the temperature difference between the periphery (T6) and the center (T1) of the substrate can be reduced as shown in FIG. 8 by increasing the light irradiation intensity at the central portion and decreasing it at the peripheral portion in the lamp arrangement (FIG. 8). This is a period of about 0 to 20 seconds) This is because the stress caused by rapid substrate temperature rise is reduced as in conventional light irradiation heating, and the substrate is hardly warped, and the heating lamp light is directly incident on the pyrometer. It is thought that it was gone.

  In one substrate heat treatment method according to an embodiment of the present invention, in the open circuit control process after the start of the first light irradiation, the substrate is heated and the temperature is increased with the light irradiation intensity distribution shown in FIG. After the above temperature or the heating time has elapsed for a certain time, the closed circuit control process is performed with the uniform light irradiation intensity distribution shown in FIG.

  FIG. 9 is a diagram showing the relationship between the specific resistance of the heated object and the maximum temperature difference. The result of having applied the open circuit control process of light irradiation rapid thermal processing to the board | substrate material which has various specific resistance using the light irradiation intensity distribution shown to Fig.4 (a) is shown. The maximum temperature difference in the figure is the difference in temperature measured by the pyrometer located at T1 and T6 in FIG. The substrate is 8 inches in diameter, thermal SiO2 is a silicon substrate formed with a thermal oxide film, SiN is a silicon substrate formed with a SiN film, and P- / Pepi-Si is a medium concentration on the silicon substrate. P + / Pepi-Si has a medium concentration P type epitaxial growth layer formed on a high concentration silicon substrate, and dopedPolySi introduces phosphorus, boron, arsenic, etc. on the silicon substrate. A polysilicon film is formed.

  From this result, when the specific resistance is 1 Ω · cm or more, in the open circuit control step after the start of light irradiation, the light irradiation intensity for heating can have a distribution as shown in FIG. It is effective for reducing the stress of the heated object. If the maximum temperature difference in the body to be heated is 70 ° C or higher, the effect on general semiconductor device characteristics and reliability will be noticeable. Therefore, the maximum temperature difference is 70 ° C or lower and the specific resistance of the entire substrate is 1Ω · cm or higher. This is a standard for performing an open circuit control process having an irradiation intensity distribution.

  Next, when the specific resistance of the substrate is 1 Ω · cm or less, the maximum temperature difference is 70 ° C. or more. However, when the resistance is low, the response of the substrate to the temperature change and temperature distribution is fast, so the light irradiation of the lamp If the intensity is distributed, it is considered that the distribution directly reflects the temperature distribution in the substrate. Therefore, in the embodiment of the present invention, when most of the substrate has a specific resistance of 1 Ω · cm or less, the open circuit control step is performed with the light irradiation intensity of the lamp of the heat treatment apparatus made uniform.

  In the embodiment described above, when the specific resistance of the substrate is 1 Ω · cm or more, the light irradiation intensity of the lamp is divided into two regions 203 and 204 + region 205 as shown in FIG. It is possible to divide into more regions according to the specific resistance of the object to be heated, etc., and control the input power and light irradiation intensity for each region to form an intensity distribution.

  The light irradiation heat treatment apparatus according to the embodiment of the present invention is as shown in FIG. 1, but based on the experimental results as shown in FIG. 9 regarding the open circuit control process of heat treatment, the specific resistance of the object to be heated before the light irradiation heat treatment is performed. Based on the measurement means (specific resistance measurement means) and the measured specific resistance of the heated object, a distribution is generated in the light irradiation intensity of a large number of lamp sets provided in a plane so as to face the heated object. As described above, it is possible to provide an apparatus to which means (light irradiation intensity control means) for automatically setting the light intensity to be irradiated for each lamp collecting area is added. The relationship between the specific resistance of the object to be heated and the light irradiation intensity distribution of the lamp assembly in which the maximum temperature difference in the object to be heated in the open circuit control process of the heat treatment is 70 ° C. or less is obtained, and this is calculated as described above. The above apparatus can be realized if it is input to the setting means.

  The light irradiation heat treatment method and the light irradiation heat treatment apparatus according to the present invention reduce the stress by reducing the temperature variation of the object to be heated after the start of light irradiation, and are free from distortion, distortion, warping, cracking, etc. It has the effect of suppressing fluctuations in the characteristics of the embedded semiconductor device and reducing reliability defects, and is used for various types of heat treatment in the semiconductor integrated circuit device manufacturing process. It can be applied to devices in which the occurrence of stress due to heat treatment is a problem.

It is the schematic of the light irradiation heat processing apparatus in embodiment of this invention. It is a lamp | ramp arrangement top view of the light irradiation heat processing apparatus by embodiment of this invention. It is a figure which shows the light intensity control area | region of the lamp | ramp of the light irradiation heat processing apparatus by embodiment of this invention. It is a figure which shows the light irradiation intensity distribution of the lamp | ramp in embodiment of this invention. It is a graph which shows the temperature change of the to-be-heated body by the conventional heat processing. It is a figure which shows the relative position of the temperature measurement pyrometer with respect to a lamp | ramp and a to-be-heated body. It is a figure which shows the curvature of a to-be-heated body when the light irradiation by a lamp | ramp is performed in a prior art example. It is a graph which shows the time change of the temperature of the to-be-heated body by the light irradiation heat processing method by embodiment of this invention. It is a figure which shows the relationship between the specific resistance of a to-be-heated body, and a maximum temperature difference.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Lamp 102 Heated object support body 103 Heated object 104 Pyrometer 105 Inert gas introduction port 106 Inert gas exhaust port 107 8 inch diameter heated object position 108 Heated object support position 201 Distance 202 from the center of the heated object Radius 203 of the object to be heated is inside the object to be heated and is a circle area 204 having a radius of 101. It is an area inside the object to be heated and is an area other than 103. Non-body region 501 Lamp 502 Heated object support 503 Pyrometer 504 Heated object 505 when no strain due to stress occurs Heated object 506 when stress due to stress occurs Direct incident on the pyrometer due to distortion of the heated object Lamp light

Claims (7)

  A light irradiation heat treatment method in which a heated body is supported in a container and the heated body is heat-treated by a planar light irradiation heating means provided facing one surface of the heated body, the light irradiation In the step of increasing the temperature of the object to be heated by irradiating light from the heating means, light having a planar light intensity distribution such that the maximum temperature difference in the surface of the object to be heated is 70 ° C. or less is heated. A light irradiation heat treatment method characterized by irradiating a body.   2. The light according to claim 1, further comprising a step of performing heat treatment by irradiating the object to be heated with light having a uniform intensity in a plane from the light irradiation heating unit after the step of increasing the temperature of the object to be heated. Irradiation heat treatment method.   The light irradiation heat treatment method according to claim 1, wherein the object to be heated has a circular shape, and a planar light intensity distribution from the light irradiation heating unit is a concentric distribution.   The light irradiation heat treatment method according to claim 1, wherein the object to be heated is a semiconductor substrate.   A support for supporting the heated body provided in the container, a planar light irradiation heating means provided facing one surface of the heated body supported by the support, and the heated body The temperature measuring means provided opposite to the other surface opposite to the one surface, and when the temperature of the object to be heated is increased, the maximum temperature difference in the surface of the object to be heated is 70 ° C. or less. A light irradiation heat treatment apparatus comprising: a light intensity control means for controlling a light irradiation intensity distribution in a plane of the light irradiation heating means.   The light irradiation heating means is composed of an assembly in which a large number of heating lamps are arranged in a plane, and the assembly of the heating lamps is divided into a plurality of planar regions, and each region has an independent light irradiation intensity. The light irradiation heat treatment apparatus according to claim 5, which can be set as follows.   The light irradiation heat treatment apparatus according to claim 6, wherein the object to be heated is made of a semiconductor substrate, and the assembly of the heating lamps is divided into a plurality of planar concentric regions.

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