Moisture impurity test method for ultra-pure TEOS, and detection device

Abstract

A moisture impurity test method for ultra-pure TEOS for an integrated circuit, and a detection device. The test method comprises the following steps: step A, preparing a standard reagent, wherein the standard reagent comprises iodine of a calibrated concentration and sulfur dioxide of a calibrated concentration; preparing a coulomb detection apparatus, which at least comprises an electrolysis electrode, a test electrode and a current measurement device, and a titration apparatus, wherein the electrolysis electrode and the test electrode are placed in a solution in the titration apparatus in a working state, and the electrolysis electrode and the test electrode are electrically connected to the current measurement device at least in the working state; and step B, adding an appropriate amount of methanol to the titration apparatus, adding an appropriate amount of a standard reagent in the working state until the reading of the current measurement device is constant, adding a sample needing to be calibrated and to be subjected to measurement, using the standard reagent to perform titration until the reading of the current measurement device is constant, recording the volume of the standard reagent consumed at the moment as V4, and performing calculation accordingly to obtain a moisture content. The method is easily operated and high in operation efficiency, and efficiently implements rapid, efficient and high-precision measurement of traces of residual water.

Description

Ultrapure TEOS water impurity testing method and testing equipment

[0001] This application claims priority to Chinese patent application number 2023111062890, filed with the Patent Office of China on August 30, 2023, entitled “Method and Equipment for Testing Moisture Impurities in Ultrapure TEOS,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention relates to a detection technology, in particular to a method and equipment for testing moisture impurities in ultrapure TEOS for integrated circuits. Background Art

[0003] The main methods for forming oxide layers in semiconductor processes include thermal oxidation (for semiconductor materials that can form self-stable oxide layers), low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), and atmospheric pressure chemical vapor deposition (APCVD). Due to the high gas flow required and the relatively high particle generation during APCVD, it is rarely used in most semiconductor processes.

[0004] During LPCVD of tetraethyl orthosilicate (TEOS), TEOS evaporates from liquid to gas, decomposes at 700-750°C and 300mTOR pressure, and deposits on the surface of the silicon wafer to form a silicon dioxide film. The deposition rate of the silicon dioxide film can reach 50°C / min, and the thickness uniformity of the film is less than 3%. These excellent process characteristics and its significant features in terms of safety in use have gradually become the mainstream process for depositing silicon dioxide films.

[0005] Using tetraethyl orthosilicate (TEOS) LPCVD technology to deposit silicon dioxide on the SiC wafer surface, the process mitigates the drawbacks of the thin SiC oxide layer and the loose silicon dioxide layer produced by PECVD. The rational application of TEOS LPCVD and high-temperature oxidation ensures the density of the oxide layer and its adhesion to the SiC wafer, while also improving the device's electrical performance and yield. This technology also avoids the drawbacks of long, high-temperature oxidation cycles required to achieve a desired oxide thickness. This technology has significantly improved the DC yield of SiC chips, and comparative tape-out results for microwave power devices demonstrate a significant improvement in microwave performance, with power gain increasing by approximately 1.5 dB and power-added efficiency increasing by nearly 10% compared to the original process.

[0006] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0007] Summary of the Invention

[0008] The present invention aims to provide a method and apparatus for testing water impurities in ultrapure TEOS for integrated circuits, which are easy to operate and highly efficient, and effectively achieve rapid, efficient, and high-precision determination of trace residual water.

[0009] To achieve the above-mentioned objectives, an embodiment of the present invention provides a method for testing moisture impurities in ultrapure TEOS for integrated circuits, comprising the following steps: A. preparing a standard reagent, wherein the standard reagent includes iodine and sulfur dioxide of calibrated concentrations; preparing a coulometric detection device and a titration device comprising at least an electrolytic electrode, a test electrode, and a current detection device, wherein the electrolytic electrode and the test electrode are placed in a solution in the titration device in a working state, and the electrolytic electrode and the test electrode are at least electrically connected to the current detection device in a working state; B. adding an appropriate amount of methanol to the titration device, adding an appropriate amount of standard reagent in a working state until the current detection device reads a constant, adding a sample to be calibrated and tested, and titrating with the standard reagent until the current detection device reads a constant, recording the volume of the standard reagent consumed at this time as V4, and calculating the moisture content based on the volume.

[0010] In one or more embodiments of the present invention, the moisture content is calculated using the following formula:

[0011] T = (V4*T) / (m0*10) or T = (V4*T) / (V0*ρ*10), where:

[0012] M0 is the mass of the solid sample, in grams (g);

[0013] V0 is the volume of the liquid sample, in milliliters (mL);

[0014] V4: The volume of standard reagent consumed during the determination, in milliliters (mL);

[0015] ρ is the density of the liquid sample at 20 degrees, in grams per milliliter (g / mL);

[0016] T is the calculated titer of the standard reagent in milligrams per milliliter (mg / mL).

[0017] In one or more embodiments of the present invention, the standard reagent is prepared by dissolving an appropriate amount of iodine in a first solvent, adding a second solvent and mixing, and then dissolving an appropriate amount of sulfur dioxide.

[0018] In one or more embodiments of the present invention, the first solvent is selected from methanol and ethylene glycol methyl ether.

[0019] In one or more embodiments of the present invention, the second solvent is selected from pyridine.

[0020] In one or more embodiments of the present invention, the environment in which the standard reagent is prepared is a low-temperature environment.

[0021] In one or more embodiments of the present invention, the low temperature environment is an ice water bath, an ice salt bath, an ice bath, or a dry ice bath.

[0022] In one or more embodiments of the present invention, the electrolysis electrode and the test electrode are platinum electrodes.

[0023] In one or more embodiments of the present invention, the current detection device is an ammeter.

[0024] In one or more embodiments of the present invention, the detection equipment adopts the moisture impurity testing method of ultrapure TEOS for integrated circuits as claimed in claim 1, and the equipment at least includes a coulometric detection device and a titration device provided with an electrolytic electrode, a test electrode and a current detection device.

[0025] Compared with the prior art, the moisture impurity testing method and detection equipment for ultrapure TEOS for integrated circuits according to the embodiments of the present invention achieve high-precision and rapid determination of residual moisture with the assistance of electrolysis. During the titration process, the reaction and electrolysis detection can be completed synchronously, which is easy to operate and highly efficient, and effectively achieves rapid, efficient and high-precision determination of trace residual water. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0027] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0028] When determining moisture content, water reacts with iodine and sulfur dioxide in the presence of methanol and alkali as follows, where RN is the organic base: H2O + I2 + SO2 + CH3OH + 3RN → [RHN] SO4CH3 + 2[RHN]I-----(1)

[0029] In volumetric titrations, iodine is added as a titrant, whereas in coulometric titrations, iodine is produced electrochemically by oxidation in the electrolytic cell: 2I- → I2 + 2e-----(2)

[0030] As long as there is water in the electrolyte, the iodine produced will react according to the chemical reaction formula (1). I2 and H2O will react with each other in a 1:1 ratio. According to Faraday's law, the amount of iodine produced is proportional to the charge. The relationship between charge and water content is estimated to be 10.72mC / 1μgH2O. Therefore, the current consumption can be used as the basis for measuring water content. Once all the water participates in the chemical reaction, a small amount of excess iodine will form in the anode area of ​​the electrode. The excess iodine can be measured using a polarized electrode. The current stops flowing and no more iodine is produced.

[0031] Test system composition

[0032] The test system mainly consists of a titration cell, a support rod, a magnetic stirrer, an electrolytic electrode, a test electrode, a drying tube, etc.

[0033] Start stirring with the stirring beads. If the reaction cup contains water and the instrument is not ready, you need to start electrolysis and balance. Make the electrolyte in the reaction cup form a vortex, but do not splash onto the wall of the cell.

[0034] If you're using fresh electrolyte for the first time, there may be an excess of iodine. In this case, inject an appropriate amount of pure water. Use a 50μL injector to draw an appropriate amount of pure water (generally, a new reagent requires approximately 20-50μL of pure water; here, 30μL is acceptable). Insert the injection stopcock and slowly inject it into the reagent. Continue until the reagent's color slowly changes from dark brown to light yellow, and until the electrolyte is completely water-rich, stop injecting pure water, remove the injection needle, and wait for equilibrium to complete before testing.

[0035] When the instrument is in the ready state and the electrolysis value is relatively stable (that is, the reading no longer fluctuates significantly), it can be calibrated with standard water or pure water. It is recommended to use standard water for calibration by weighing. The relationship between the water mass and the power consumption of the electrolysis of the coulometric moisture meter is fixed. In theory, no calibration operation is required. If there is any doubt about the moisture measurement result, a calibration operation can be performed. Extract standard water with a water mass of about 500μg, wipe the needle dry, and then inject the sample below the liquid surface to start the analysis. Wait for the analysis to end. The water mass of the analysis result should be the theoretical water mass ± 10μg. It is recommended to calibrate more than 3 times. If the deviation between the measured water mass and the theoretical water mass exceeds 5%, it is recommended to adjust the correction factor in the method.

[0036] Weigh the sample to be tested and add it into the reaction cup.

[0037] Standard reagent configuration

[0038] Place 670 mL of methanol or ethylene glycol monomethyl ether in a dry, 1-liter, stoppered brown glass bottle. Add approximately 85 g of iodine, seal the bottle, and shake until the iodine is completely dissolved. Then, add 270 mL of pyridine, seal the bottle tightly, and shake again until thoroughly mixed. Dissolve 65 g of sulfur dioxide in the solution using the following method. When introducing sulfur dioxide, replace the bottle with a rubber cap. Attach the rubber cap to a thermometer, a glass inlet tube (10 m from the bottom, approximately 6 mm in diameter), and a capillary tube for atmospheric ventilation.

[0039] Place the entire apparatus and ice bath on a balance and weigh to the nearest 1g. Connect the sulfur dioxide cylinder (or the outlet of the sulfur dioxide generator) to the desiccant-filled drying tower and the glass inlet tube via a flexible hose. Slowly open the inlet valve. Adjust the flow rate so that the sulfur dioxide is completely absorbed and the liquid level in the inlet tube does not rise. As the mass slowly increases, adjust the balance weight to maintain equilibrium. Keep the solution temperature below 20°C. When the mass reaches 65g, immediately close the inlet valve.

[0040] Quickly remove the connecting hose and weigh the glass bottle and air inlet. The mass of dissolved sulfur dioxide should be 60-70g, with an appropriate excess. Tightly cap the bottle, mix the solution, and store in a dark place for at least 24 hours before use. The reagent titer should be 3.5mg / mL to 4.5mg / mL.

[0041] If prepared with methanol, a standard reagent with a lower titer can be prepared by diluting the prepared solution with the sample solvent.

[0042] The reagent should be stored in a brown reagent bottle in a dark place and protected from moisture in the atmosphere.

[0043] Since the reaction is exothermic, the brown glass bottle should be cooled from the beginning of the reaction and kept at a temperature of about 0°C, for example, by immersing it in an ice bath or crushed dry ice.

[0044] instrument

[0045] All glassware used in the instrument were pre-dried in an oven controlled at approximately 130°C for 30 min, then cooled and stored in a desiccator containing desiccant.

[0046] Automatic burette: 25mL, fine tip, graduation 0.05mL, connected to the protective tube filled with reagent to prevent atmospheric moisture from entering the tube.

[0047] Titration container: effective capacity 100mL, connected to the automatic burette with a frosted glass joint, and has two branches, one for inserting the platinum electrode during titration, and the other for plugging the rubber stopper so that the liquid sample can be injected with a syringe without opening the container.

[0048] Platinum electrode, weld the platinum wire electrode into the glass tube, insert it into the bottom of the titration container, and connect it to the two copper wires of the end point coulometric device.

[0049] The electromagnetic stirrer is fixed on a height-adjustable base and uses a soft steel rod wrapped in glass or polytetrafluoroethylene for stirring at a speed of 150 to 300 r / min.

[0050] Reagent bottle for standard reagent, capacity 3L, made of brown glass, inserted into the feeding tube of the automatic burette through the frosted stopper.

[0051] The double rubber ball is connected to the drying bottle filled with desiccant to pressurize the air into the reagent bottle so that the reagent fills the burette.

[0052] End point coulometric device.

[0053] Medical syringes of suitable capacity and calibrated for volume.

[0054] A small glass tube (weighing sample tube), closed at one end and sealed with a rubber stopper at the other end, is used to weigh samples and add materials to the titration container.

[0055] test

[0056] A power supply, ammeter, and two electrodes are connected to form a circuit so that a potential difference is formed between the two electrodes immersed in the solution. When water is present in the solution, the cathode polarizes against the flow of current, and the endpoint of the titration is indicated by cathode depolarization accompanied by a sudden increase in current (indicated by a suitable electrical device).

[0057] 1. Calibration of standard reagents

[0058] Lubricate the joint with silicone grease, inject 25 mL of methanol into the titration vessel through the rubber stopper using a syringe, turn on the electromagnetic stirrer, and connect the endpoint coulometric device.

[0059] Adjust the instrument so that there is a 1V to 2V potential difference between the electrodes and the ammeter indicates a low current, usually a few microamperes. To react with the trace amount of water present in the methanol, add the standard reagent until the ammeter indicates a sudden increase in current to about 10 to 20 microamperes and remains stable for at least 1 minute.

[0060] Add approximately 0.040 g of water from a dropping bottle for calibration. Weigh the mass of the dropping bottle before and after adding it to the titration vessel and determine the mass of water used (m4) by subtracting the difference.

[0061] Titrate the known amount of water added with the standard reagent to be calibrated until the ammeter pointer reaches the same deflection and remains stable for at least 1 min. Record the volume of standard reagent consumed (V3).

[0062] 8.2.2 Determination

[0063] Drain the remaining liquid in the titration vessel through the drain nozzle. Use a syringe to inject 25 mL (or the volume specified for the sample to be tested) of methanol solvent through the rubber stopper. Turn on the electromagnetic stirrer. In order to react with the trace amount of water in the methanol, add the standard reagent dropwise until the ammeter pointer suddenly deflects and remains stable for at least 1 minute.

[0064] Addition of sample: If the sample is liquid, inject with a syringe; if the sample is solid powder, weigh an appropriate amount of sample in a small glass tube, accurate to 0.0001g. Titrate the standard reagent to the endpoint and record the volume of standard reagent consumed during the measurement (V4)

[0065] The titer T of the standard reagent, expressed in mg / mL, is calculated according to formula (1):

[0066] Formula (1) T = m4 / V3

[0067] m4: represents the mass of water added, in milligrams (mg)

[0068] V3: The volume of the standard reagent consumed during calibration, in milliliters (mL)

[0069] The water content of the sample X is expressed as a mass percentage and is calculated according to formula (2) or formula (3):

[0070] Formula (2) T = (V4*T) / (m0*10)

[0071] Formula (3) T = (V4*T) / (V0*ρ*10)

[0072] Where:

[0073] M0 is the mass of the sample (solid sample), in grams (g);

[0074] V0 is the volume of the sample (liquid sample), in milliliters (mL);

[0075] V4: The volume of standard reagent consumed during the determination, in milliliters (mL);

[0076] ρ is the density of the sample (liquid sample) at 20 degrees Celsius, in grams per milliliter (g / mL);

[0077] T is the calculated titer of the standard reagent in milligrams per milliliter (mg / mL).

[0078] Example 1

[0079] A. Prepare standard reagents, which include 1 mol iodine and 3 mol sulfur dioxide of calibrated concentration (the preparation of a large number of reagents is shown here, and in actual operation, it can be proportionally reduced to the actual amount used, the same below); prepare a coulometric detection device and a titration device including at least an electrolytic electrode, a test electrode, and a current detection device, wherein the electrolytic electrode and the test electrode are placed in the solution in the titration device under working conditions, and the electrolytic electrode and the test electrode are at least electrically connected to the current detection device under working conditions; B. Add 50 mol methanol to the titration device, add an appropriate amount of standard reagent under working conditions until the current detection device reading is constant, add a sample to be calibrated and tested, titrate with the standard reagent until the current detection device reading is constant, record the volume of the standard reagent consumed at this time as V4, and calculate the moisture content accordingly. The present invention is easy to operate and has high operating efficiency, and effectively realizes the rapid, efficient and high-precision determination of trace residual water.

[0080] When titrating with standard reagents:

[0081] Add a certain volume of methanol (enough to immerse the platinum electrode) to the reaction flask and titrate to the endpoint with the standard reagent under stirring. Add m mg of water (accurate to 0.0001 g), titrate to the endpoint and record the amount of standard reagent used (V). The titer of the standard reagent is calculated as follows:

[0082] V

[0083] Where:

[0084] T—Titer of the standard reagent, in milligrams per milliliter (mg / mL)

[0085] m—mass of water, in milligrams (mg);

[0086] V—The amount of standard reagent consumed in titrating water, in milliliters (mL).

[0087] Similarly, when titrating a sample, the water content is calculated

[0088] A=V4T / m4*100%

[0089] Where: A is the moisture content of the sample to be tested

[0090] V4 Volume of standard reagent consumed in titration

[0091] m4 weighs the mass of the sample

[0092] The detection process is the same below.

[0093] Example 2

[0094] A. Prepare standard reagents, which include 5 mol iodine and 15 mol sulfur dioxide at a calibrated concentration; prepare a coulometric detection device and a titration device comprising at least an electrolytic electrode, a test electrode, and a current detection device; the electrolytic electrode and the test electrode are placed in a solution in the titration device in a working state; the electrolytic electrode and the test electrode are at least electrically connected to the current detection device in a working state; B. Add 250 mol methanol to the titration device, add an appropriate amount of standard reagent in a working state until the current detection device reads a constant, add a sample to be calibrated and tested, and titrate with the standard reagent until the current detection device reads a constant. Record the volume of the standard reagent consumed at this time as V4, and calculate the moisture content accordingly. The present invention is easy to operate and has high operating efficiency, and effectively realizes the rapid, efficient, and high-precision determination of trace residual water.

[0095] Example 3

[0096] A. Prepare standard reagents, which include 3 mol iodine and 9 mol sulfur dioxide at a calibrated concentration; prepare a coulometric detection device and a titration device comprising at least an electrolytic electrode, a test electrode, and a current detection device; the electrolytic electrode and the test electrode are placed in a solution in the titration device in a working state; the electrolytic electrode and the test electrode are at least electrically connected to the current detection device in a working state; B. Add 150 mol methanol to the titration device, add an appropriate amount of standard reagent in a working state until the current detection device reads a constant, add a sample to be calibrated and tested, and titrate with the standard reagent until the current detection device reads a constant. Record the volume of the standard reagent consumed at this time as V4, and calculate the moisture content based on this. The present invention is easy to operate and has high operating efficiency, effectively achieving rapid, efficient, and high-precision determination of trace residual water.

[0097] Table 1 Test results of Examples 1-3

[0098] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for testing water impurities in ultrapure TEOS for integrated circuits, comprising the following steps: A. Prepare standard reagents, wherein the standard reagents include iodine and sulfur dioxide of calibrated concentrations; prepare a coulometric detection device and a titration device including at least an electrolytic electrode, a test electrode and a current detection device, wherein the electrolytic electrode and the test electrode are placed in a solution in the titration device in a working state, and the electrolytic electrode and the test electrode are at least electrically connected to the current detection device in a working state; B. Add an appropriate amount of methanol to the titration device, add an appropriate amount of standard reagent in the working state until the current detection device reads a constant, add the sample to be calibrated and tested, and titrate with the standard reagent until the current detection device reads a constant. Record the volume of the standard reagent consumed at this time as V4, and calculate the moisture content based on this.

2. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 1, characterized in that: The moisture content is calculated using the following formula: T=(V4*T) / (m0*10) or T=(V4*T) / (V0*ρ*10), where: M0 is the mass of the solid sample, in grams (g); V0 is the volume of the liquid sample, in milliliters (mL); V4: The volume of standard reagent consumed during the determination, in milliliters (mL); ρ is the density of the liquid sample at 20 degrees, in grams per milliliter (g / mL); T is the calculated titer of the standard reagent in milligrams per milliliter (mg / mL).

3. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 1, characterized in that: The standard reagent is obtained by dissolving an appropriate amount of iodine in a first solvent, adding a second solvent and mixing well, and then dissolving an appropriate amount of sulfur dioxide.

4. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 3, characterized in that: The first solvent is selected from methanol and ethylene glycol methyl ether.

5. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 3, characterized in that: The second solvent is selected from pyridine.

6. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 3, characterized in that: The environment in which the standard reagent is prepared is a low temperature environment.

7. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 6, characterized in that: The low temperature environment is an ice water bath, an ice salt bath, an ice bath, or a dry ice bath.

8. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 1, characterized in that: The electrolysis electrode and the test electrode are platinum electrodes.

9. The method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 1, characterized in that: The current detection device is an ammeter.

10. A testing device, using the method for testing water impurities in ultrapure TEOS for integrated circuits as claimed in claim 1, wherein the device comprises at least a coulometric testing device and a titration device provided with an electrolytic electrode, a testing electrode and a current testing device.

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