TW202326106A - Method and device for measuring oxygen content in silicon wafer - Google Patents

Abstract

The embodiment of the invention discloses a method and device for measuring the oxygen content in a silicon wafer, and the method comprises the steps: putting a silicon wafer sample with an oxidation film and a reducing agent into a reaction chamber, carrying out the first-stage calcination so as to enable the oxidation film to be subjected to oxidation reduction, and obtaining the quality of the oxidation film through detecting CO and/or CO2 generated by the reaction, the calcination temperature of the first stage is lower than the melting point of the silicon wafer sample; carrying out second-stage calcination on the silicon wafer sample in the reaction chamber to melt the silicon wafer sample, and detecting CO and/or CO2 generated by reaction again to obtain the mass of the oxygen element in the silicon wafer sample; and obtaining the concentration of the oxygen element in the silicon wafer sample based on the mass of the oxidation film and the mass of the oxygen element in the silicon wafer sample.

Description

Method and device for measuring oxygen content in silicon wafer

Embodiments of the present invention belong to the technical field of silicon wafer processing, and in particular relate to a method and device for measuring oxygen content in silicon wafers.

At present, large-sized semiconductor-grade single-crystal silicon rods are usually drawn by Czochralski method. The Czochralski method involves melting polysilicon in a crucible made of quartz to obtain a silicon melt, immersing a seed crystal in the silicon melt, and continuously lifting the seed crystal upwards away from the surface of the silicon melt, whereby during the movement A single crystal silicon rod is grown at the solid-liquid interface.

It is known that oxygen is the most important impurity element in single crystal silicon rods obtained by the Czochralski method, and partially supersaturated oxygen elements will form oxygen precipitates during the growth, processing and device manufacturing of single crystal silicon rods, The formation of oxygen precipitates in single crystal silicon rods will have a great impact on device performance.

Specifically, for dopant-containing single crystal silicon rods, the crystal structure of single crystal silicon rods has changed due to the addition of a large amount of dopants, for example, heavily doped boron single crystal silicon rods belong to the P-type Heavily doped, compared with other types of heavily doped single crystal silicon rods, it has excellent characteristics. The specific performance is that the resistivity distribution is uniform, the concentration of oxygen element in the body increases, and the oxygen precipitation is enhanced, thereby improving the performance of this type of single crystal silicon rod. Silicon wafers made of silicon rods have internal gettering ability, and at the same time, heavily doped boron single crystal silicon rods have high mechanical strength, which can suppress VOID defects and improve the yield of devices.

In view of this, the embodiments of the present invention expect to provide a method and device for measuring the oxygen content in the silicon wafer; the oxygen content inside the silicon wafer can be measured more accurately.

The technical solution of the embodiment of the present invention is achieved in the following way: First, the embodiment of the present invention provides a method for measuring the oxygen content in a silicon wafer, the method includes: putting a silicon wafer sample formed with an oxide film into a reaction with a reducing agent The first stage of calcination is carried out in the chamber so that the oxide film is oxidized and reduced, and the quality of the oxide film is obtained by detecting the CO and/or _CO2 generated by the reaction, wherein the calcination temperature of the first stage is lower than The melting point of the silicon wafer sample; the silicon wafer sample is subjected to a second-stage calcining in the reaction chamber to melt the silicon wafer sample, and the silicon wafer is obtained by detecting the CO and/or CO ₂ produced by the second reaction The mass of the oxygen element inside the sample; the concentration of the oxygen element inside the silicon wafer sample is obtained based on the mass of the oxide film and the mass of the oxygen element inside the silicon wafer sample.

In a second aspect, an embodiment of the present invention provides a device for measuring the oxygen content in a heavily doped silicon wafer, the device comprising: a calcination unit, used to perform a first-stage calcination on a silicon wafer sample formed with an oxide film, The oxide film is completely oxidized and reduced, wherein the calcination temperature of the first stage is lower than the melting point of the silicon wafer sample; Melting; a detection unit for detecting the CO and/or _CO generated by the calcination reaction of the first stage to obtain the quality of the oxide film; and for detecting the CO and/or CO generated by the calcination reaction of the second stage or _CO2 to obtain the quality of the oxygen element inside the silicon wafer sample; the acquisition unit is used to obtain the oxygen element inside the silicon wafer sample based on the quality of the oxide film and the quality of the oxygen element inside the silicon wafer sample concentration.

The embodiment of the present invention provides a method and device for measuring the oxygen content in a silicon wafer; the method includes performing two calcinations on a silicon wafer sample formed with an oxide film, wherein the temperature of the first calcination is lower than that of the silicon wafer sample melting point, but it can make the oxide film of the silicon wafer sample be oxidized and reduced, and the temperature of the second calcination can make the silicon wafer sample melt _. Finally, the concentration of oxygen element inside the silicon wafer sample is obtained; using the method provided according to the embodiment of the present invention, there is no need to add a cleaning step to remove the oxide film on the surface of the silicon wafer sample before the calcination operation, but the oxide film is obtained through the calcination operation The quality of the silicon wafer sample, thus obtaining the actual mass of the silicon wafer sample that does not contain the oxide film, and then based on the actual mass of the silicon wafer sample, the oxygen content inside the silicon wafer sample is obtained. This oxygen content will not include the oxygen content in the oxide film, so it is more For accuracy, the error caused by the oxidation of the surface of the silicon wafer to the measurement of the oxygen content inside the silicon wafer sample is eliminated.

In order for Ligui examiners to understand the technical characteristics, content and advantages of the present invention and the effects it can achieve, the present invention is hereby combined with the accompanying drawings and appendices, and is described in detail in the form of embodiments as follows, and the drawings used therein , the purpose of which is only for illustration and auxiliary instructions, and not necessarily the true proportion and precise configuration of the present invention after implementation, so it should not be interpreted based on the proportion and configuration relationship of the attached drawings, and limit the application of the present invention in actual implementation The scope is described first.

In the description of the embodiments of the present invention, it should be understood that the terms "length", "width", "upper", "lower", "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 embodiments of the present invention and simplifying the description , rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and thus 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 embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention.

In the process of preparing single crystal silicon rods by the Czochralski method, oxygen mainly enters the molten silicon through the dissolution of the quartz crucible, and 95% of the oxygen exists in the silicon lattice in the interstitial state. Interstitial oxygen has a great influence on the gettering ability, mechanical strength and resistivity of silicon wafers. The interstitial oxygen content is related to the density and shape of oxygen deposits. Too high an oxygen content will easily cause the silicon wafer to slip and warp, making it difficult to obtain a sufficient depth of cleaning area, but too low an oxygen content will cause the silicon wafer to lack internal gettering. Capability, and thus the control of the oxygen content in the silicon wafer, is critically linked to device performance.

In view of the above situation, it is necessary to measure the oxygen content inside the silicon wafer during the silicon wafer manufacturing process. At present, for lightly doped silicon wafers, Fourier Transform infrared spectroscopy (FTIR for short) is usually used for measurement, which is a relatively simple non-destructive measurement technique; for heavily doped silicon wafers, such as Silicon wafers heavily doped with boron, due to the high boron content inside, cannot use common methods to measure the oxygen content inside, so the related technology is based on the FTIR method and improves the infrared in order to apply it to heavy doping The measurement of the oxygen content inside the silicon wafer, but the measurement results are not ideal.

In addition, the gas phase fusion analysis method (Gas Fusion Analysis, referred to as GFA) is also used in this field to measure the oxygen content inside the heavily doped silicon wafer. The GFA method mainly includes: putting the silicon wafer into a graphite crucible, heating it and melting it, The oxygen in the silicon wafer fully reacts with the excess carbon in the graphite crucible to form carbon monoxide, which is converted into carbon dioxide after being heated by copper oxide, and then the carbon dioxide is quantitatively measured by FTIR method, so as to calculate the concentration of oxygen in the silicon wafer. Gas Fusion Analysis (GFA) can be used to measure the content of oxygen, nitrogen and hydrogen in refractory metals and other inorganic materials. The measurement of oxygen, nitrogen and hydrogen in silicon wafers requires the use of gas phase fusion analysis (GFA) .

Referring to Fig. 1, it shows the flow chart of the method for measuring oxygen content in conventional silicon wafer, and this method has used GFA method to measure the oxygen content inside silicon wafer, and this method comprises the following steps: S101: Cut silicon wafer into Small sample; S102: Soak the small sample in HF solution; S103: Put the soaked small sample into a graphite crucible and heat it to 1400°C to melt and detect the generated CO and CO ₂ to obtain the oxygen content.

Among them, since the surface of the small sample is easily oxidized to form an oxide film after contacting with air, it is necessary to soak the small sample in HF solution to remove the surface oxide film, and the whole heating process is in a closed inert gas such as argon environment carried out in.

However, when the small sample is taken out from the HF and has not been put into the graphite crucible, it will be oxidized and form an oxide film on the surface again when it is in contact with the air again. Both will produce additional oxidation on the small sample. When using the conventional GFA method, the oxygen in the oxide film will also be included in the internal oxygen content of the silicon wafer, and the mass of the oxide film will also be included in the total of the small sample. Quality, so it will affect the measurement accuracy of the oxygen content inside the silicon wafer, usually, the error will reach about 5%. If you want to accurately measure the oxygen content inside the silicon wafer, you must exclude the oxygen in the oxidized part of the silicon wafer surface, and also exclude the mass of the oxide film when calculating the total mass of the silicon wafer.

Based on the above problems, see Figure 2, which shows a method for measuring the oxygen content in a silicon wafer provided by an embodiment of the present invention, the method includes: S201: put the silicon wafer sample with an oxide film and a reducing agent into the reaction chamber Carry out the first-stage calcining in order to redox the oxide film, and obtain the quality of the oxide film by detecting the CO and/or _CO2 generated by the reaction, wherein the calcining temperature of the first stage is lower than that of the silicon The melting point of the wafer sample; S202: Carry out the second-stage calcining of the silicon wafer sample in the reaction chamber to melt the silicon wafer sample, and obtain the silicon wafer by detecting the CO and/or CO ₂ generated by the reaction again The mass of the oxygen element inside the sample; S203: Obtain the concentration of the oxygen element inside the silicon wafer sample based on the mass of the oxide film and the mass of the oxygen element inside the silicon wafer sample.

The method provided by the embodiment of the present invention includes two stages of calcination. The silicon wafer sample is put into the reaction chamber together with the reducing agent for calcination. The oxygen of the silicon wafer sample is reduced to carbon monoxide and/or carbon dioxide by the reducing agent, and By detecting the carbon monoxide and/or carbon dioxide produced by the two-stage calcination, the mass of oxygen reduced by the two calcinations can be obtained, and the mass of oxygen obtained by the two calcinations represents the mass and oxygen element in the oxide film on the surface of the silicon wafer sample respectively. The quality of the oxygen element inside the silicon wafer sample, thus the quality of the oxide film can be obtained to obtain the real quality of the silicon wafer sample without the oxide film, based on which the concentration of the oxygen element inside the silicon wafer sample will be closer to actual value.

An embodiment of the present invention provides a method for measuring the oxygen content in a silicon wafer; the method includes performing two calcinations on a silicon wafer sample formed with an oxide film, wherein the temperature of the first calcination is lower than the melting point of the silicon wafer sample , but the oxide film of the silicon wafer sample can be oxidized and reduced, and the temperature of the second calcination can melt the silicon wafer sample. By detecting the CO and/or CO ₂ produced during the two calcination operations, the final Obtain the concentration of oxygen element inside the silicon wafer sample; using the method provided according to the embodiment of the present invention, it is not necessary to add a cleaning step to remove the oxide film on the surface of the silicon wafer sample before the calcination operation, but obtain the oxide film by calcination operation quality, thus obtaining the actual mass of the silicon wafer sample without the oxide film, and then obtaining the oxygen content inside the silicon wafer sample based on the actual mass of the silicon wafer sample. This oxygen content will not include the oxygen content in the oxide film, so it is more Accurate, eliminating the error caused by the oxidation of the surface of the silicon wafer to the measurement of the oxygen content inside the silicon wafer sample.

According to an optional embodiment of the present invention, obtaining the quality of the oxide film by detecting CO and/or _CO2 generated by the reaction includes: measuring the concentration of CO and/or _CO2 generated by the reaction by an infrared detector to obtain The concentration of oxygen element in the oxide film, and then obtain the quality of the oxide film.

According to another optional embodiment of the present invention, the obtaining the quality of the oxygen element inside the silicon wafer sample by detecting the CO and/or _CO generated by the second reaction includes: using an infrared detector to detect the CO and/or CO generated by the second reaction Or the concentration of CO ₂ is measured to obtain the concentration of oxygen element inside the silicon wafer sample, and then obtain the mass of oxygen element inside the silicon wafer sample.

As an example and not limitation, the CO and _CO generated by the reaction are detected by non-dispersive infrared absorption method. Specifically, referring to Fig. 3, since CO and _CO have an absorption effect on infrared light of a specific wavelength, It shows a unique absorption peak in the infrared absorption spectrum, and the concentration of CO and CO ₂ can be obtained by integrating the absorption peak and then converted into oxygen concentration. As shown in Figure 3, it shows the curve graph of the oxygen concentration detected by non-dispersive infrared absorption method as a function of time, wherein, t1 represents the time of the calcination of the first stage, and t2 represents the time of the calcination of the second stage Time, the solid line curve M1 represents the test curve of the oxygen concentration in the oxide film on the surface of the silicon wafer sample obtained by reducing the oxide film of the silicon wafer sample through the first stage of calcination, and the solid line curve M2 represents the test curve after the second stage The test curve of the oxygen concentration inside the silicon wafer sample obtained by melting the silicon wafer sample by calcination, by performing Gauss-Lorentz split peak fitting on the test curves M1 and M2, the dotted curves N1 and N2 can be obtained respectively, Integrate the curves N1 and N2 to obtain the CO and CO ₂ concentrations generated by the two stages of calcination respectively, and then convert them into oxygen concentrations. Since it is difficult for oxygen to be completely oxidized to CO ₂ at one time during the calcination process, in order to To achieve the purpose of accurate measurement, for example, the tested CO can be oxidized to CO ₂ by using heated copper oxide, and then the CO ₂ can be detected, so that the measurement results can be verified bidirectionally.

For the selection of silicon wafer samples, the appropriate mentioned silicon wafer samples can be selected according to needs, for example, a part of a single silicon wafer can be selected. Before being put into the reaction chamber for the first stage of calcination, the method further includes: weighing the silicon wafer sample with the oxide film formed, which is used for subsequent calculation of the concentration of oxygen element.

According to an optional embodiment of the present invention, the concentration of oxygen element inside the silicon wafer sample based on the mass of the oxide film and the mass of oxygen element inside the silicon wafer sample is obtained by the following formula: in, Represents the concentration of oxygen in the wafer sample, Represents the mass of oxygen element inside the silicon wafer sample, Represents the quality of the silicon wafer sample with the oxide film formed, represents the quality of the oxide film.

For the two-stage calcination, optionally, in the first stage, the silicon wafer sample is heated to 1100-1200°C for 30-60 seconds, so that the oxide film is completely oxidized and reduced without causing the silicon wafer The sample is melted; in the second stage, the silicon wafer sample is heated to 1400-1500° C. for 120-180 s, so that the silicon wafer sample without the oxide film is melted.

According to an optional embodiment of the present invention, the reducing agent includes carbon powder.

According to an optional embodiment of the present invention, the reaction chamber includes a graphite crucible, and the silicon wafer sample can be put into the graphite crucible for calcining, and the carbon in the graphite crucible can also reduce the oxygen in the silicon wafer sample block to CO and/or or CO ₂ .

Referring to FIG. 4 , the embodiment of the present invention also proposes a device 300 for measuring the oxygen content in a heavily doped silicon wafer. The device 300 for measuring the oxygen content in a heavily doped silicon wafer includes: The silicon wafer sample of the oxide film is calcined in the first stage, so that the oxide film is completely oxidized and reduced, wherein, the calcining temperature of the first stage is lower than the melting point of the silicon wafer sample; and, for the silicon wafer The sample is subjected to the second stage of calcination, so that the silicon wafer sample is melted; the detection unit 302 is used to detect the CO and/or _CO2 generated by the first stage of the calcination reaction to obtain the quality of the oxide film; and, use To detect the CO and/or _CO2 generated by the calcination reaction in the second stage to obtain the quality of the oxygen element inside the silicon wafer sample; an acquisition unit 303, the acquisition unit is used to The mass of oxygen element inside the sample obtains the concentration of oxygen element inside the silicon wafer sample.

According to another optional embodiment of the present invention, the acquisition unit 303 is configured to: obtain the concentration of oxygen element inside the silicon wafer sample based on the mass of the oxide film and the mass of oxygen element inside the silicon wafer sample by the following formula get: in, Represents the concentration of oxygen in the wafer sample, Represents the mass of oxygen element inside the silicon wafer sample, Represents the quality of the silicon wafer sample with the oxide film formed, represents the quality of the oxide film.

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.

The above are only preferred embodiments of the present invention, and are not used to limit the implementation scope of the present invention. If the present invention is modified or equivalently replaced without departing from the spirit and scope of the present invention, it shall be covered by the protection of the patent scope of the present invention. in the range.

S101-S103: Steps S201-S203: Steps 300: A device for measuring oxygen content in heavily doped silicon wafers 301: Calcination unit 302: detection unit 303: get unit

Fig. 1 is a flow chart of a conventional method for measuring the oxygen content in a silicon wafer; Fig. 2 is a flow chart of a method for measuring the oxygen content in a silicon wafer provided by an embodiment of the present invention; Fig. 3 is the graph that adopts the oxygen concentration that the non-dispersive infrared absorption method detects to change with time; FIG. 4 is a schematic diagram of a device for measuring oxygen content in a silicon wafer provided by an embodiment of the present invention.

S201-S203: Steps

Claims (10)

A method for measuring the oxygen content in a silicon wafer, wherein the method includes: putting a silicon wafer sample formed with an oxide film and a reducing agent into a reaction chamber for the first stage of calcination so that the oxide film is oxidized and reduced, and The quality of the oxide film is obtained by detecting the CO and/or _CO2 generated by the reaction, wherein the calcination temperature of the first stage is lower than the melting point of the silicon wafer sample; the second stage is performed on the silicon wafer sample in the reaction chamber Two-stage calcination to melt the silicon wafer sample, and obtain the quality of oxygen element inside the silicon wafer sample by detecting the CO and/or CO ₂ generated by the second reaction; based on the quality of the oxide film and the inside of the silicon wafer sample The mass of oxygen element obtained the concentration of oxygen element inside the silicon wafer sample. The method for measuring the oxygen content in a silicon wafer as described in Claim 1, wherein the CO and/or CO generated by the detection reaction to obtain the quality of the oxide film includes: the CO and/ _or CO generated by the reaction through an infrared detector Or the concentration of CO ₂ is measured to obtain the concentration of oxygen element in the oxide film, and then obtain the quality of the oxide film. The method for measuring the oxygen content in a silicon wafer as described in Claim 1, wherein, the CO and/or CO obtained by detecting the re-reacted CO and/or _CO2 to obtain the quality of the oxygen element inside the silicon wafer sample includes: The concentration of CO and/or CO ₂ generated by the second reaction is measured to obtain the concentration of oxygen element inside the silicon wafer sample, and then obtain the mass of oxygen element inside the silicon wafer sample. The method for measuring oxygen content in a silicon wafer as described in Claim 1, wherein, before putting the silicon wafer sample with an oxide film and the reducing agent into the reaction chamber for the first stage of calcination, the method further includes: The silicon wafer sample with the oxide film formed is weighed. The method for measuring the oxygen content in a silicon wafer as described in Claim 1, wherein, the concentration of the oxygen element inside the silicon wafer sample is obtained based on the quality of the oxide film and the quality of the oxygen element inside the silicon wafer sample through the following formula get: in, Represents the mass of oxygen element inside the silicon wafer sample, Represents the quality of the silicon wafer sample with the oxide film formed, represents the quality of the oxide film. The method for measuring the oxygen content in a silicon wafer as described in any one of claims 1 to 5, wherein, In the first stage, the silicon wafer sample is heated to 1100-1200°C for 30-60s, so that the oxide film is completely oxidized and reduced; In the second stage, the silicon wafer sample is heated to 1400-1500° C. for 120-180 s, so that the silicon wafer sample is melted. The method for measuring oxygen content in a silicon wafer according to any one of claims 1 to 5, wherein the reducing agent includes carbon powder. The method for measuring oxygen content in a silicon wafer according to any one of claims 1 to 5, wherein the reaction chamber includes a graphite crucible. A device for measuring the oxygen content in a heavily doped silicon wafer, wherein the device includes: a calcining unit, which is used to perform a first-stage calcining on a silicon wafer sample formed with an oxide film, so that the oxide film is completely oxidized and reduced , wherein, the calcination temperature of the first stage is lower than the melting point of the silicon wafer sample; The CO and/or _CO2 generated by the calcination reaction of the first stage to obtain the quality of the oxide film; and, used to detect the CO and/or _CO2 generated by the calcination reaction of the second stage to obtain the silicon wafer The mass of the oxygen element inside the sample; an acquisition unit, the acquisition unit is used to obtain the concentration of the oxygen element inside the silicon wafer sample based on the mass of the oxide film and the mass of the oxygen element inside the silicon wafer sample. The device for measuring oxygen content in a heavily doped silicon wafer as described in Claim 9, wherein the acquisition unit is configured to: acquire the silicon wafer sample based on the quality of the oxide film and the quality of oxygen element inside the silicon wafer sample The concentration of oxygen element inside is obtained by the following formula: in, Represents the mass of oxygen element inside the silicon wafer sample, Represents the quality of the silicon wafer sample with the oxide film formed, represents the quality of the oxide film.