KR20000037951A - Method for measuring deposited amount of interstitial type oxygen of silicon wafer in which large amount of metal is doped - Google Patents

Abstract

PURPOSE: A method for measuring a deposited amount of interstitial type oxygen of a silicon wafer in which a large amount of metal is doped is provided to prevent the silicon wafer from being damaged when the measuring process is performed. CONSTITUTION: In a method for measuring a deposited amount of interstitial type oxygen of a silicon wafer in which a large amount of metal is doped, an initial X-ray intensity and an amount of a deposited oxygen amount are first measured, then a final X-ray intensity and an amount of a deposited oxygen amount are measured. Linear relations between the initial and final X-ray intensities and the two deposited oxygen amounts are calculated. Next, an X-ray intensity of a silicon wafer sample is measured and the same is annealed. An X-ray intensity of the annealed sample is then measured. An amount of oxygen deposited in the silicon wafer is measured by using the X-ray intensities before and after the annealing process and the linear relations.

Description

Method for measuring the amount of piercing oxygen precipitates in a silicon wafer doped with a large amount of metal

The present invention relates to a method for measuring an interstitial type oxygen precipitate (Delta [Oi]) present in a crystal grown silicon wafer, and more particularly, in the process of processing a crystal grown silicon wafer. The present invention relates to a method capable of accurately measuring the amount of infiltrating oxygen precipitates.

Silicon wafers, which are mainly used as substrates in the manufacture of semiconductor devices, generally produce high purity polycrystalline silicon rods, followed by single crystal rods according to the Czochralski crystal growth method or the float zone crystal growth method. It is produced by producing, cutting it thinly, mirror-polishing one surface of a silicon wafer, and cleaning. The fabricated silicon wafer has a film forming step of growing or adding a thin film of various materials to the surface of the silicon wafer, a pattern forming step of selectively removing the thin film from the silicon wafer, and changing the selected resistivity and conductivity of the silicon wafer with the addition of impurities. A semiconductor device or a circuit may be processed through a silicon wafer processing process including a doping step. During the crystal growth of silicon wafers, a small amount of oxygen inevitably enters the crystals. Especially, in the case of silicon wafers grown by Czochralski crystal growth method, the oxygen content required for high-quality semiconductors due to the high supersaturated oxygen content in the silicon wafers. There is a problem of exceeding the content.

In addition, the supersaturated oxygen in the grown silicon wafer forms an oxygen precipitate during the silicon wafer processing process, which increases the stacking defects caused by oxidation, thereby increasing the leakage current defect rate in the semiconductor device. There is a problem to reduce. Conventional measurements of the amount of chipped oxygen precipitates before or after annealing silicon wafers have been performed using Fourier Transform Infrared Ray Spectrometry (FTIR), but this method does not allow a small amount of metal to be doped. It can be applied to measure the amount of chipped oxygen deposits present in the silicon wafers, but it is strong in infrared to measure the amount of chipped oxygen deposits on a large amount of metal doped silicon wafers used as the substrate of the Epi wafer. There is difficulty due to the absorption rate. Therefore, the amount of chipped oxygen precipitates present inside the silicon wafer doped with a large amount of metal was measured using a gas fusion analysis (GFA) or a secondary ion mass spectroscopy (SIM). However, the method of measuring the amount of chipped oxygen precipitate using GFA or SIMS is not only damaging the silicon wafer but also cannot distinguish the amount of the chipped oxygen precipitate from the total oxygen concentration present inside the silicon wafer. There is a problem. Therefore, it is impossible to measure the amount of infiltrating oxygen precipitates by the conventional measuring method. In particular, this problem becomes a big problem when the production of high quality Epi wafer is required in the future. It is very important to analyze this correctly.

Accordingly, the present invention is to solve the above problems, an object of the present invention is to provide a method for accurately analyzing the amount of the piercing oxygen precipitates present in the silicon wafer doped with a large amount of metal without damaging the silicon wafer will be.

In order to achieve the above object, the present invention uses the X-ray dissection method

a) preparing a silicon wafer sample by doping a small amount of metal onto the silicon wafer;

b) measuring the initial X-ray intensity (I _i ) and the initial pleated oxygen precipitate amount (O _i ) of the silicon wafer sample prepared in step a);

c) annealing the silicon wafer sample from step b) in two steps;

d) measuring the X-ray final intensity (I _f ) and the final pleated oxygen precipitate amount (O _f ) of the silicon wafer sample subjected to step c);

e) deriving a linear relationship between I _i / I _f and O _i / O _{f, which} is the ratio of the X-ray intensity measured in steps b) and d), respectively, to the amount of chipped oxygen precipitates;

f) preparing a silicon wafer sample by doping a large amount of metal onto the silicon wafer;

g) measuring the initial X-ray intensity of the silicon wafer sample prepared in step f);

h) annealing the silicon wafer sample subjected to step g) in two steps;

i) measuring the final X-ray intensity of the silicon wafer sample subjected to step h); And

j) quantitatively evaluating the amount of chipped oxygen precipitate present in the silicon wafer doped with a large amount of metal.

By developing a series of process steps including a provides a method for accurately analyzing the amount of the chipped oxygen precipitate of the silicon wafer doped with a large amount of metal without damaging the silicon wafer.

Hereinafter, the present invention will be described in detail.

In order to accurately analyze the amount of chipped oxygen precipitate of a large amount of metal doped silicon wafer according to the present invention without damaging the silicon wafer, a silicon wafer sample is first prepared for measuring the amount of chipped oxygen precipitate.

A small amount of metal is doped into a silicon wafer sample by putting a small amount of polycrystalline silicon and a metal to be doped into a graphite furnace and melting it. In this case, the resistivity of the metal-doped silicon wafer is measured using FTIR, Silver varies depending on the type and concentration of the metal to be doped, but is preferably 0.1 Ω · cm or more. When the resistivity of the silicon wafer is less than 0.1 Ω · cm, the IR is absorbed by the electrons of the silicon wafer within the wavelength and the intensity is lowered. Therefore, the accurate detection of the FTIR is impossible. It is not preferable because it cannot be measured. The metal material to be doped may be a compound of Group III and Group V elements, a halide or a single element, but boron metal is preferably doped to produce a high quality EPi wafer substrate. There are many forms, but the preferred form is boron oxide (B ₂ O ₃ ). When boron is doped to the silicon wafer, it is preferable to dope the boron so that the specific resistance value is 2-20 Ω · cm, preferably 5-15 Ω · cm.

When a silicon wafer sample doped with a small amount of metal is thus prepared, the initial X-ray intensity I _i of the silicon wafer sample is measured. At this time, the initial X-ray intensity is measured by X-ray dissection method using an X-ray diffraction apparatus. When the amount of metal doped in the silicon wafer is excessive or too small, the correlation between the X-ray intensity and the amount of chipped oxygen precipitates It is not preferable because cannot be derived. The silicon wafer sample from which the initial X-ray intensity was measured is transferred to an infrared spectrometer to measure the amount of initial infiltrating oxygen precipitate (O _i ). When measuring the amount of infiltrating oxygen precipitates by infrared spectroscopy, the amount of metal doped is important, and when a large amount of metal is doped, it is difficult to accurately measure the amount of infiltrating oxygen precipitates because of the strong absorption of infrared rays. In general, the amount of doped metals suitable for accurately measuring the amount of chipped oxygen precipitates by infrared spectroscopy generally has a specific resistance value of 0.1 Ω · cm or more of the metal-doped silicon wafer, but this value depends on the type of doped metal. can be different.

A two-step annealing is performed on the silicon wafer sample from which the initial chipped oxygen precipitate amount was measured. In general, the annealing of the silicon wafer is carried out to recover the crystallinity of the silicon wafer after performing some processing on the silicon silicon wafer, or to improve the physical properties of the silicon wafer, and there are various annealing methods. In order to confirm the change of the oxygen precipitates of the silicon wafer using the annealing method, the oxygen concentration present in the silicon wafer is reduced by performing annealing of the silicon wafer, which is a two-step silicon wafer comprising forming an oxygen precipitate nucleus and growing the nucleus formed. Let's do it. In the annealing method, the silicon wafer is first placed in a conventional diffusion furnace, and the temperature is gradually raised to bring the temperature in the furnace to 600-800 ° C., and the heat treatment of the silicon wafer sample is performed at this temperature for 200-700 minutes. The temperature is raised to 800-1200 ° C. and the silicon wafer is heat treated again at this temperature for 700-1200 minutes to perform a two step annealing. Since the annealing conditions of the silicon wafer, that is, the annealing temperature and time have a significant influence on the physical properties of the silicon wafer sample, it is desirable to maintain the annealing conditions accurately according to the physical properties of the silicon wafer to be manufactured. The final X-ray intensity (I _f ) and the amount of final chipped oxygen precipitate (O _f ) of the annealed small amount of metal doped silicon wafer sample are measured using X-ray dissection and infrared spectroscopy, respectively. In this case, it is possible to confirm that most of the oxygen removed by annealing from the FTIR peak is chopped oxygen. The correlation between the initial and final X-ray intensity values measured above and the amount of the initial and final pleated oxygen precipitates is derived. It is a linear representation of I _i / I _f and O _i / O _f by plotting the X-ray intensity on the x-axis, plotting the amount of infiltrating oxygen deposits on the y-axis, and displaying the measured values on the graph. Correlate.

Next, in order to measure the amount of the chipped oxygen precipitate of the silicon wafer doped with a large amount of metal, a large amount of metal is doped in the same manner as described above. In this case, the specific resistance value of the silicon wafer doped with a large amount of metal may vary depending on the metal to be doped. On average, the resistivity value is preferably 0.0001 Ω · cm to less than 0.1 Ω · cm, and when boron is doped to the silicon wafer, It is preferable to dope boron so that it may become 0.0001-0.01 ohm * cm. When a silicon wafer sample doped with a large amount of metal is prepared as described above, the X-ray intensity of the silicon wafer sample is measured in the same manner as described above, and then the sample is subjected to two-step annealing using the same method and conditions as described above. X-ray intensity is measured. The measured initial and final X-ray intensities are applied to the linear correlations between the I _i / I _f and O _i / O _f obtained above for a small amount of metal, which are present before and after annealing on a large amount of metal doped silicon wafer sample. The amount of piercing oxygen precipitate is obtained. The amount of oxygen precipitates obtained is an important data in the production of high quality silicon wafers because the density of the deposition defects of the silicon wafers that may occur in the processing steps of the silicon wafers is known.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are provided only to more easily understand the present invention and do not limit the present invention.

Example 1

After boron was placed in a graphite furnace together with silicon crystals to grow the crystals, it was cut, polished, and washed to prepare a silicon wafer sample so that the resistivity value was 5-15 Ω · cm. Initial X-ray intensity (I _i ) and amount of initial piercing oxygen precipitate (O _i ) of the silicon wafer sample were measured by X-ray dissection and infrared spectroscopy, respectively. The silicon wafer sample was placed in a diffusion furnace and the temperature was raised to 700 ° C., followed by a first anneal at this temperature for 300 minutes, and again the temperature in the furnace was raised to 1000 ° C. to perform a second annealing at this temperature for 800 minutes. . End of the annealed silicon wafer sample in the same manner as the X-ray intensity (I _f) and the amount of intrusion oxygen precipitates (O _f) of the measurement, measured in the I _i and O _i with the ratio of I _i / I _f and O _i / O _f were derived. Boron was doped to the prepared silicon wafer sample so that the resistivity value was 0.001-0.01 Ω · cm, and the initial X-ray intensity was measured by the same method as above, and then annealed under the same conditions as above, and the final X-ray intensity was measured. The initial and final X-ray intensities measured on boron-doped silicon wafers with a resistivity value of 0.001-0.01 Ω · cm were applied to the linear relationship between I _i / I _f and O _i / O _f derived before and after annealing. The amount of the subsequent chipped oxygen precipitate was derived.

Example 2

The amount of piercing oxygen precipitate before and after annealing of the boron-doped silicon wafer was derived in the same manner as in Example 1 except that the first annealing was performed at 700 ° C. for 450 minutes.

Example 3

The amount of piercing oxygen precipitate before and after annealing of the boron-doped silicon wafer was derived in the same manner as in Example 1 except that the first annealing was performed at 700 ° C. for 600 minutes.

As can be seen from the above, the present invention was able to accurately analyze the amount of chipped oxygen precipitates present inside a silicon wafer doped with a large amount of metal using an X-ray dissection method without damaging the silicon wafer.

The present invention makes it possible to develop high quality Epi wafer substrates by accurately analyzing the amount of infiltrating oxygen deposits present inside a silicon wafer doped with a large amount of metal using an X-ray dissection method without damaging the silicon wafer. can do.

Claims (4)

In the method for measuring the amount of piercing oxygen precipitates of a silicon wafer doped with a large amount of metal, a) preparing a wafer sample by doping a metal so that a resistivity value is 0.1 ohm * cm or more on a silicon wafer; b) measuring the initial X-ray intensity (I _i ) and the amount of chipped oxygen precipitate (O _i ) of the wafer sample prepared in step a); c) annealing the wafer sample passed through step b) in two steps; d) measuring the final X-ray intensity (I _f ) and the amount of chipped oxygen precipitate (O _f ) of the wafer sample subjected to step c); e) deriving a linear relationship between I _i / I _f and O _i / O _{f, which} is the ratio of the X-ray intensity measured in steps b) and d), respectively, to the amount of chipped oxygen precipitates; f) preparing a wafer sample by doping a large amount of metal so that the resistivity value is less than 0.0001 Ω · cm to less than 0.1 Ω · cm; g) measuring the X-ray intensity of the wafer sample prepared in step f); h) annealing the wafer sample subjected to step g) in two steps; i) measuring the X-ray intensity of the wafer sample subjected to step h); And j) quantitatively evaluating the amount of infiltrating oxygen precipitate present in the wafer doped with a large amount of metal. Method of measuring the amount of infiltrating oxygen precipitates comprising a. The method of claim 1, A method for measuring the amount of infiltrating oxygen precipitates wherein the metal doped into the silicon wafer sample is boron. The method of claim 1, The two-step annealing of steps c) and h) is a chipped oxygen precipitate that performs a first annealing for 200-700 minutes at a temperature of 600-800 ° C. and a second annealing for 700-1200 minutes at a temperature of 800-1200 ° C. Method of measuring quantity. The method of claim 1, X-ray intensity is measured using an X-ray dissection method, and the amount of infiltrating oxygen precipitates of a silicon wafer doped with a small amount of metal is measured using infrared spectroscopy.