TW202305209A - Method for calibrating thermometer of epitaxial furnace - Google Patents

Abstract

The embodiment of the invention discloses a method for calibrating a thermometer of an epitaxial furnace. The method comprises the following steps: introducing HCl gas into the epitaxial furnace so as to carry out gas phase etching on a first test silicon wafer in the epitaxial furnace; the temperature in the epitaxial furnace is monitored to serve as the reference temperature, and the etching amount of the first test silicon wafer is monitored to serve as the reference etching amount; fitting a linear relation between the reference temperature and the reference etching amount; and calibrating the thermometer of the epitaxial furnace by using the linear relationship between the reference temperature and the reference etching amount.

Description

A method for calibrating a thermometer of an epitaxial furnace

The invention belongs to the technical field of semiconductor manufacturing, in particular to a method for calibrating a thermometer of an epitaxial furnace.

In the field of semiconductors, silicon wafers are generally the raw material for integrated circuits. Compared with polished silicon wafers, epitaxial silicon wafers have the characteristics of less surface defects and controllable resistivity, so they are widely used in highly integrated integrated circuit (Integrated Circuit, IC) components and metal oxide Half field effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET), MOS) process.

At present, the most widely used method for epitaxial silicon wafers is atmospheric pressure epitaxial deposition. The deposition temperature is usually between 1100°C and 1150°C. Therefore, reasonable temperature control is of great significance to the performance of the epitaxial wafer.

In view of this, how to accurately monitor the temperature in the process of epitaxial technology is a technical problem that needs to be solved urgently in related technologies.

In order to solve the above technical problems, the embodiment of the present invention expects to provide a method for calibrating a thermometer of an epitaxial furnace.

The technical solution of the present invention is achieved as follows: the embodiment of the present invention provides a method for calibrating the thermometer of the epitaxial furnace, comprising: Introducing HCl gas into the epitaxial furnace to perform vapor phase etching on the first test silicon wafer in the epitaxial furnace; monitoring the temperature in the epitaxial furnace as a reference temperature and monitoring the etching amount of the first test silicon wafer as a reference etching amount; fitting the linear relationship between the reference temperature and the reference etching amount; Using the linear relationship between the reference temperature and the reference etching amount to calibrate the thermometer of the epitaxial furnace.

The embodiment of the present invention provides a method for calibrating the thermometer of the epitaxial furnace; first, use HCl gas to etch the test silicon wafer placed in the epitaxial furnace, and monitor the temperature in the epitaxial furnace and test the silicon wafer during the etching process. The etch amount of the sheet is used as the reference temperature and the reference etch amount respectively, and then the linear relationship between the obtained reference temperature and the reference etch amount is fitted, and this linear relationship can be used to calibrate the thermometer of the epitaxial furnace, the present invention The method for calibrating the thermometer of the epitaxial furnace avoids the disassembly and installation of parts in the cavity of the epitaxial furnace, thereby avoiding the reduction in production capacity and frequent technical verification caused by disassembly and assembly, and the method for calibrating the epitaxial furnace of the present invention The thermometer method can accurately determine the actual temperature in the cavity of the epitaxial furnace, and the measured value of the calibrated thermometer is closer to the actual temperature value.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

It should be noted that when an element is referred to as being “fixed” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

It is to be understood that the terms "length", "width", "top", "bottom", "front", "rear", "left", "right", "vertical", "horizontal", "top" , "bottom", "inner", "outer" and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying No device or element must have a specific orientation, be constructed, and operate in a specific orientation and therefore should not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of said features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

Referring to FIG. 1 , the entire chamber of the atmospheric pressure epitaxy furnace 1 is composed of an upper bell jar 50 , a lower bell jar 60 and a metal base ring 70 made of transparent quartz, and the halogen lamps arranged outside the upper bell jar 50 and the lower bell jar 60 Serving as a heating unit 40, the heating unit 40 provides the high temperature required by the chemical reactions occurring in the chamber through the action of heat radiation. The temperature reading of the atmospheric pressure epitaxy furnace 1 is realized by a high temperature infrared thermometer group, which includes an upper thermometer 101 , a lower thermometer 102 and an upper bell jar thermometer 103 . The temperature during the epitaxial layer deposition process is mainly monitored and fed back to the temperature of the upper surface of the wafer and the center point of the lower surface of the wafer base 80 through the upper thermometer 101 and the lower thermometer 102, and the controller adjusts the temperature of the heating unit 40 based on the feedback. The power ratio is used to adjust the temperature and uniformity of the wafer surface.

In the actual epitaxial growth process, if the deposition temperature of the epitaxial layer changes, the epitaxial wafer will slip, and parameters such as flatness and resistivity will change, affecting product quality. For example, after parts such as heating unit 40 or wafer base 80 have been replaced, the emissivity coefficient and linearity coefficient of the thermometer need to be adjusted to calibrate the accuracy of the thermometer. In the long run, there will be deviations in the measured values of each thermometer, making it impossible to accurately judge the temperature value of the chamber, and the temperature during the epitaxial growth process will also deviate from the set temperature, making the actual growth temperature higher or lower than the set temperature. temperature, thus affecting the quality of epitaxial products. At present, the calibration of the thermometer requires the use of a dedicated temperature calibration base, and the thermocouple is inserted into the base for calibration. To perform this method, the cavity needs to be disassembled, which takes a long time and seriously affects the production capacity; in addition, for the current calibration method In other words, due to the presence of by-products deposited on the upper bell jar, the temperature read by the thermometer will be inconsistent with the set value, and eventually the internal temperature of the chamber will deviate from the target temperature. A general calibration method will be described below.

In conventional techniques, the thermometer inside the epitaxial furnace is usually calibrated during the initial assembly of the epitaxial furnace. The calibration tool is a specially designed silicon chip base and thermocouple. The base is disc-shaped, and a hole is opened on the side of the disc to the center of the base. When assembling the chamber, put the base into the chamber, then extend the thermocouple into the chamber from the outside of the metal base ring 70 and pass through the hole on the side of the base to the center of the base, and then insert the epitaxy furnace into the chamber Assembly is complete. After the assembly is completed, after heating up and baking for 48 hours, by changing the power of the heating unit and adjusting the emissivity and linearity coefficients of the upper and lower thermometers according to the actual readings of the thermocouples, the reading values of the thermometers are within a certain range (700°C ~1200°C) and consistent with the temperature value read by the thermocouple. Then, the chamber is disassembled and installed again, and components required for epitaxial growth are replaced. However, this calibration method is time-consuming and labor-intensive, and seriously affects equipment productivity.

In addition, in actual operation, whenever the epitaxial furnace is maintained, such as replacing the heating unit or the wafer base, due to the change of the material of the component parts or the change of the space point, the thermometer needs to be recalibrated to make the inside of the chamber real. The temperature matches the reading. In order to avoid the cumbersome disassembly of the thermocouple temperature calibration method and the reduction in production capacity caused by it, the temperature when the heating unit reaches a certain power is used as a reference to adjust the thermometer emission and linear coefficient, which is approximately considered as an accurate value. However, due to the fact that the halogen lamp used as a heating unit will cause a deviation between the supplied power and its actual power according to the difference in its actual use time, after a long period of use, it is impossible to accurately determine the real temperature in the chamber, because when the above deviation occurs, When a certain power is reached, the temperature tends to drift, as shown in Figure 2, which affects the product quality.

In view of the above situation, how to provide a fast and convenient temperature calibration method is very important for the production of epitaxial wafers. Since the chamber is usually cleaned by injecting HCl gas after the epitaxial technology is performed, and the etching amount of the silicon wafer by the HCl gas is very sensitive to temperature changes, it can be achieved by adjusting the temperature gradient between different temperature gradients and the etching amount of the silicon wafer. Linear analysis is performed on the relationship between , so as to calibrate the thermometer according to the amount of etching. Therefore, the embodiment of the present invention proposes a method for calibrating the thermometer of the epitaxial furnace by using the characteristics of HCl gas.

Specifically, referring to FIG. 3, an embodiment of the present invention proposes a method for calibrating a thermometer of an epitaxial furnace, including: S01: inject HCl gas into the epitaxial furnace to perform vapor phase etching on the first test silicon wafer in the epitaxial furnace; S02: monitoring the temperature in the epitaxial furnace as a reference temperature and monitoring the etching amount of the first test silicon wafer as a reference etching amount; S03: fitting the linear relationship between the reference temperature and the reference etching amount; S04: Using the linear relationship between the reference temperature and the reference etching amount to calibrate the thermometer of the epitaxial furnace.

The embodiment of the present invention provides a method for calibrating the thermometer of the epitaxial furnace; first, use HCl gas to etch the test silicon wafer placed in the epitaxial furnace, and monitor the temperature in the epitaxial furnace and test the silicon wafer during the etching process. The etch amount of the sheet is used as the reference temperature and the reference etch amount respectively, and then the linear relationship between the obtained reference temperature and the reference etch amount is fitted, and this linear relationship can be used to calibrate the thermometer of the epitaxial furnace, the present invention The method for calibrating the thermometer of the epitaxial furnace avoids the disassembly and installation of parts in the cavity of the epitaxial furnace, thereby avoiding the reduction in production capacity and frequent technical verification caused by disassembly and assembly, and the method for calibrating the epitaxial furnace of the present invention The thermometer method can accurately determine the actual temperature in the cavity of the epitaxial furnace, and the measured value of the calibrated thermometer is closer to the actual temperature value.

According to an optional embodiment of the present invention, after the thermometer of the epitaxial furnace is calibrated, the reference temperature and the reference etching amount can be obtained and the linear relationship between the two can be fitted, and after the parts of the epitaxial furnace are replaced, for example, the heating Cells, wafer pedestals, etc. are then used to calibrate the thermometers in the epitaxial furnace using this linear relationship.

According to another optional embodiment of the present invention, using the linear relationship between the reference temperature and the reference etching amount to calibrate the thermometer of the epitaxial furnace includes: S101: injecting HCl gas into the epitaxial furnace to perform vapor phase etching on the second test silicon wafer in the epitaxial furnace; S102: Monitor the actual temperature in the epitaxial furnace and monitor the actual etching amount of the second test silicon wafer; S103: Comparing the actual temperature with the reference temperature under the condition that the actual etching amount is equal to the reference etching amount; S104: Make the actual temperature equal to the reference temperature by adjusting the parameters of the thermometer of the calibration epitaxial furnace.

According to the above-mentioned embodiments of the present invention, using the linear relationship between the reference temperature and the reference etching amount may specifically include: during the calibration process of the thermometer in the epitaxial furnace, perform Vapor phase etching, during this etching process, monitor the actual temperature in the epitaxial furnace and the actual etching amount of the test silicon wafer, and compare the actual temperature with the reference temperature when the actual etching amount is equal to the reference etching amount If there is a difference between the actual temperature and the reference temperature, adjust the parameters of the thermometer until the actual temperature is equal to the reference temperature, so as to achieve the purpose of calibrating the thermometer.

High-temperature infrared thermometers are usually used in epitaxy furnaces. The measurement of high-temperature infrared thermometers is achieved through the relationship between the size of the infrared radiation energy of the object and its surface temperature, and the emissivity of the material made of the object can reflect the infrared of the object. Radiation characteristics, therefore changing the emissivity, the high-temperature infrared thermometer will obtain different temperature readings, based on this, according to another optional embodiment of the present invention, by adjusting the parameters of the thermometer of the calibration epitaxial furnace to make the actual Equalizing the temperature to the reference temperature includes adjusting the emissivity and/or linearity coefficient of the thermometer.

After the maintenance of the epitaxial furnace, especially after the parts of the epitaxial furnace are replaced, the efficiency parameters of the epitaxial furnace and the spatial position of the internal components are changed, thus affecting the accuracy of the thermometer. In this case, it can be Deviations in thermometer measurements are simply and straightforwardly resolved by adjusting the emissivity and/or linearity coefficients of the thermometers to bring them back into line with the operating conditions of the maintained epitaxy furnace.

Because HCl gas may cause damage to the inner parts of the epitaxial furnace, especially the silicon wafer base, optionally, the method for calibrating the thermometer of the epitaxial furnace of the present invention also includes feeding HCl gas into the epitaxial furnace to check the temperature of the epitaxial furnace. Before the test silicon wafer in the epitaxial furnace is subjected to vapor phase etching, trichlorosilane gas is passed into the epitaxial furnace where the test silicon wafer is not placed, so as to deposit a silicon film on the surface of the silicon wafer base, so that the silicon wafer base play a protective role.

According to an example of the present invention, when feeding trichlorosilane gas into the epitaxial furnace, the flow rate of trichlorosilane gas is set to 15000 standard cubic centimeters per minute (Standard Cubic Centimeters per Minute, SCCM), and the _H gas flow rate is set to 50000 SCCM, the deposition time is set to 80 s, and the deposition temperature is 1130 °C.

According to an optional embodiment of the present invention, the vapor phase etching of the first test silicon wafer in the epitaxial furnace is performed according to a set temperature gradient.

According to an optional embodiment of the present invention, fitting the linear relationship between the reference temperature and the reference etching amount includes performing multiple etching experiments at the same set temperature to obtain an average value of the etching amount as the reference etching amount quantity.

In an example of the present invention, the flow rate of HCl gas is set to 15000 SCCM, the flow rate of _H2 gas is set to 50000 SCCM, the etching time of HCl gas is set to 20s, and the reference temperature gradient is set to 1100°C, 1120°C, 1140°C, 1160°C, 1180°C, 1200°C. Carry out more than 10 etching experiments for each temperature value, calculate the average value according to the results, and calculate the reference etching rate, as shown in Figure 4, the linear relationship between the temperature x and the reference etching rate y is the reference etching rate y=0.0103x+3.0745, when it is necessary to calibrate the thermometer of the epitaxial furnace, put another test silicon wafer into the epitaxial furnace and inject HCl gas for vapor phase etching. Adjust the heating power so that the actual etching rate is the same as the reference etching rate. Under this condition, compare the actual temperature gradient with the reference temperature gradient. If there is a difference, adjust the emissivity coefficient and linear coefficient of the thermometer so that the actual temperature The gradient is close to the reference temperature gradient, so as to achieve the purpose of calibrating the thermometer.

In order to accurately calibrate the thermometer of the epitaxial furnace, optionally, the first test silicon wafer and the second test silicon wafer are the same type of silicon wafers produced in the same batch, so as to avoid deviations caused by differences in the parameters of the test silicon wafers.

According to an optional embodiment of the present invention, the first test silicon chip and the second test silicon chip are P-type silicon chips or N-type silicon chips.

It should be noted that: the technical solutions described in the embodiments of the present invention can be combined arbitrarily if there is no conflict.

Embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementations, and the above-mentioned specific implementations are only illustrative, rather than restrictive, and those with ordinary knowledge in the art Under the enlightenment of the present invention, many forms can also be made without departing from the gist of the present invention and the protection scope of the claims, all of which belong to the protection of the present invention.

S01-S04: Steps 1: Atmospheric pressure epitaxy furnace 101: Go up the thermometer 102: lower thermometer 103: Upper bell thermometer 40: Heating unit 50: Upper bell jar 60: Lower the Bell Jar 70: metal base ring 80: wafer base

Fig. 1 is the structural representation of conventional atmospheric pressure epitaxial furnace; Fig. 2 is the graph of the relation of etching temperature and power; 3 is a flowchart of a method for calibrating a thermometer in an epitaxial furnace provided by an embodiment of the present invention; FIG. 4 is a graph showing the relationship between etching temperature and etching speed.

S01-S04: Steps

Claims (9)

A method for calibrating a thermometer of an epitaxial furnace comprising: Introducing HCl gas into the epitaxial furnace to perform vapor phase etching on the first test silicon wafer in the epitaxial furnace; monitoring the temperature in the epitaxial furnace as a reference temperature and monitoring the etching amount of the first test silicon wafer as a reference etching amount; fitting the linear relationship between the reference temperature and the reference etching amount; Using the linear relationship between the reference temperature and the reference etching amount to calibrate the thermometer of the epitaxial furnace. The method for calibrating the thermometer of the epitaxial furnace as described in claim 1, wherein, using the linear relationship between the reference temperature and the reference etching amount to calibrate the thermometer of the epitaxial furnace includes: Introducing HCl gas into the epitaxial furnace to perform vapor phase etching on the second test silicon wafer in the epitaxial furnace; monitoring the actual temperature in the epitaxial furnace and monitoring the actual etching amount of the second test silicon wafer; comparing the actual temperature with the reference temperature under the condition that the actual etching amount is equal to the reference etching amount; The actual temperature is equal to the reference temperature by adjusting the parameters of the thermometer of the calibration epitaxial furnace. The method for calibrating a thermometer of an epitaxial furnace as claimed in claim 2, wherein adjusting the parameters of the thermometer of the calibrating epitaxial furnace to make the actual temperature equal to the reference temperature comprises adjusting the emissivity and/or linearity of the thermometer coefficient. The method for calibrating the thermometer of the epitaxial furnace as described in claim 1, further comprising feeding HCl gas into the epitaxial furnace before gas-phase etching the test silicon wafer in the epitaxial furnace. Trichlorosilane gas is passed into the epitaxial furnace of the wafer. The method for calibrating the thermometer of the epitaxial furnace as described in Claim 1, wherein the vapor phase etching of the first test silicon wafer in the epitaxial furnace is performed according to a set temperature gradient. The method for calibrating the thermometer of the epitaxial furnace as claimed in item 2, wherein making the actual etching amount equal to the reference etching amount is realized by adjusting the heating power of the epitaxial furnace. The method for calibrating the thermometer of an epitaxial furnace as described in claim 1, wherein fitting the linear relationship between the reference temperature and the reference etching amount includes performing multiple etching experiments at the same set temperature to obtain etching The average value of the etching amount is used as the reference etching amount. The method for calibrating the thermometer of an epitaxial furnace as described in claim 2, wherein the first test silicon wafer and the second test silicon wafer are the same type of silicon wafers produced in the same batch. The method for calibrating the thermometer of an epitaxial furnace as described in claim 8, wherein the first test silicon wafer and the second test silicon wafer are P-type silicon wafers or N-type silicon wafers.

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