Test piece, preparation method of test piece and monitoring method of furnace tube annealing process

Abstract

The invention discloses a test piece, a preparation method of the test piece and a monitoring method of a furnace tube annealing process, and the monitoring method of the furnace tube annealing process comprises the following steps: carrying out a first annealing process on the test piece by using a furnace tube to obtain a treated test piece, the test piece comprises a substrate, a first protection layer formed on the surface of the substrate and a reaction layer, the reaction layer is formed on the surface, away from the substrate, of the first protection layer, and the reaction layer is crystalline polycrystalline silicon. The surface, deviating from the first protective layer, of the reaction layer of the treated test piece is treated by the first annealing process and at least partially reacts; and detecting the reaction layer of the processed test piece so as to carry out abnormity monitoring. According to the scheme, the furnace tube annealing process abnormity can be monitored in time, the monitoring sensitivity is further high, and the abnormity in the passing process can be found in time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a test wafer, a method for preparing the test wafer, and a method for monitoring the furnace tube annealing process. Background Technology

[0002] Furnace tube annealing machines are mainly divided into atmospheric pressure oxidation and low-pressure deposition processes. One type of atmospheric pressure process involves high-temperature annealing using pure nitrogen. Because this process requires a high-temperature, pure nitrogen environment, it can cause the control plates to nitride and become damaged during subsequent recycling processes, ultimately affecting their lifespan. Nitrided control plates also lead to excessive particle size in monitoring results, making it impossible to accurately reflect actual anomalies in the furnace tube annealing process.

[0003] Therefore, the current industry practice is to eliminate the on-demand control wafer for the high-temperature pure nitrogen menu in the furnace tube (i.e., not using on-demand control wafer detection), and instead replace it with periodic empty tube testing (i.e., no product wafers are placed in the furnace tube, only control wafers are placed to detect anomalies in the high-temperature pure nitrogen menu). Empty tube testing affects production capacity, and because it is a periodic test, the timing of anomaly detection is delayed, making it impossible to detect abnormalities in the furnace tube annealing process in a timely manner. Summary of the Invention

[0004] The technical problem solved by this invention is how to improve the timeliness of monitoring abnormalities in the furnace tube annealing process.

[0005] To address the aforementioned technical problems, this invention provides a test piece comprising: a substrate; a first protective layer formed on the surface of the substrate; and a reaction layer formed on the surface of the first protective layer opposite to the substrate, wherein the reaction layer is crystalline polycrystalline silicon; wherein the test piece is used for anomaly monitoring of the first annealing process of the furnace tube.

[0006] Optionally, the thickness of the reaction layer is 5950 angstroms to 6050 angstroms; and / or, the thickness of the first protective layer is 1800 angstroms to 2200 angstroms; and / or, the material of the first protective layer includes silicon dioxide.

[0007] To address the aforementioned technical problems, this invention also provides a method for preparing a test piece, which is used for anomaly monitoring of the first annealing process of a furnace tube. The preparation method includes: providing a substrate, on the surface of which a first protective layer is formed; and forming a reaction layer on the surface of the first protective layer away from the substrate, wherein the reaction layer is crystalline polycrystalline silicon.

[0008] Optionally, forming a reaction layer on the surface of the first protective layer away from the substrate includes: forming the reaction layer on the surface of the first protective layer away from the substrate using a first deposition process, wherein the reaction gas used is silane, the carrier gas is nitrogen, and the reaction temperature is 580°C to 620°C.

[0009] Optionally, the formation process of the first protective layer includes: forming the first protective layer on the surface of the substrate using an oxidation process, wherein the reaction gas used includes one or more of oxygen, hydrogen, and dichloroethane, the reaction temperature is 800°C to 1200°C, and the reaction time is 40 to 50 minutes.

[0010] Optionally, after forming a reaction layer on the surface of the first protective layer away from the substrate, the preparation method further includes: forming a second protective layer on the surface of the reaction layer away from the first protective layer; performing a second annealing process on the test piece using the furnace tube; and removing the second protective layer using an etching process.

[0011] Optionally, in the step of forming a second protective layer on the surface of the reaction layer away from the first protective layer, the reaction gas used is oxygen, the volume of the reaction gas input into the furnace tube is 7 to 10 liters, the reaction time is 27 to 33 minutes, the reaction temperature is 720°C to 880°C, and the pressure in the furnace tube during the reaction is 715 hPa to 725 hPa.

[0012] Optionally, in the step of performing the second annealing process on the test piece using the furnace tube, the reaction gas used is nitrogen, the volume of the reaction gas input into the furnace tube is 15 to 20 liters, the reaction time is 1.5 to 2 hours, the reaction temperature is 1050°C to 1100°C, and the pressure in the furnace tube during the reaction is 715 hPa to 725 hPa.

[0013] To address the aforementioned technical problems, this invention also provides a method for monitoring a furnace tube annealing process, comprising: performing a first annealing process on at least one product wafer and a test wafer using the furnace tube to obtain a processed test wafer, wherein the test wafer includes a substrate, a first protective layer formed on the surface of the substrate, and a reaction layer, the reaction layer being formed on the surface of the first protective layer opposite to the substrate, the reaction layer being crystalline polycrystalline silicon, and the surface of the reaction layer of the processed test wafer opposite to the first protective layer undergoing at least a partial reaction after being processed by the first annealing process; and detecting the reaction layer of the processed test wafer for anomaly monitoring.

[0014] Optionally, detecting the reaction layer of the treated test piece includes: detecting the thickness of the film formed after the reaction layer of the treated test piece has undergone a first annealing process and / or the particle size of the film surface.

[0015] Optionally, the test piece is reusable. Before the test piece is subjected to the first annealing process again using the furnace tube, the monitoring method further includes: performing a first etching process on the treated test piece to remove the portion of the surface of the reaction layer away from the first protective layer that reacted during the first annealing process.

[0016] Optionally, the monitoring method further includes: determining, based on the abnormal monitoring results, to perform a second cleaning process on the processed test piece to remove the reaction layer and the first protective layer.

[0017] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:

[0018] This invention provides a test piece, comprising: a substrate; a first protective layer formed on the surface of the substrate; and a reaction layer formed on the surface of the first protective layer opposite to the substrate, wherein the reaction layer is crystalline polycrystalline silicon. The test piece is used for anomaly monitoring of the first annealing process of the furnace tube. By adding a first protective layer to the surface of the substrate, the substrate surface is protected, preventing nitriding damage to the substrate during the furnace tube annealing process and extending the service life of the test piece. Furthermore, a reaction layer is added on the first protective layer (i.e., the side of the first protective layer opposite to the substrate). The reaction layer is made of crystalline polycrystalline silicon. Compared to amorphous silicon or non-crystalline polycrystalline silicon, crystalline polycrystalline silicon has a relatively flat and stable film layer, enabling better monitoring of relevant values ​​(e.g., the thickness of the film layer formed after the first annealing process). In addition, crystalline polycrystalline silicon is more sensitive to oxygen leakage during the annealing process, thus making it more effective at detecting anomalies during the transit process.

[0019] This invention provides a method for preparing a test piece used for anomaly monitoring of the first annealing process of a furnace tube. The preparation method includes: providing a substrate, on the surface of which a first protective layer is formed; and forming a reaction layer, which is crystalline polycrystalline silicon, on the surface of the first protective layer opposite to the substrate. By sequentially forming the first protective layer and the reaction layer on the substrate surface, the substrate surface is protected from nitriding damage during the furnace tube annealing process, and the sensitivity of the test piece to monitoring process anomalies in the first annealing process is improved, thereby obtaining more accurate anomaly monitoring results.

[0020] This invention provides a method for monitoring a furnace tube annealing process, comprising: performing a first annealing process on a test piece using the furnace tube to obtain a processed test piece, wherein the test piece includes a substrate, a first protective layer formed on the surface of the substrate, and a reaction layer, the reaction layer being formed on the surface of the first protective layer opposite to the substrate, the reaction layer being crystalline polycrystalline silicon, and the surface of the reaction layer of the processed test piece opposite to the first protective layer undergoing at least a partial reaction after being processed by the first annealing process; detecting the reaction layer of the processed test piece for anomaly monitoring.

[0021] This implementation scheme protects the substrate by forming a first protective layer on the surface of the test piece, preventing nitriding damage to the substrate during the furnace tube annealing process. Test pieces unaffected by nitriding can be used at any time as needed, thus enabling timely monitoring of abnormalities in the furnace tube annealing process. Furthermore, the first protective layer also helps prevent nitriding of the test piece from affecting the accuracy of abnormality monitoring results, extending the lifespan of the test piece.

[0022] Furthermore, in the step of performing the first annealing process on the test wafer using the furnace tube, the furnace tube is also used to perform the first annealing process on at least one product wafer. Therefore, the test wafer specially prepared using this embodiment can be used as a control wafer during shipment. Each shipment can detect the thickness and particle size of the film layer formed on the surface of the test wafer that has undergone the furnace tube annealing process, thereby enabling daily monitoring of the furnace tube annealing process and facilitating the timely detection of anomalies during shipment.

[0023] Furthermore, the reaction layer is prepared using a special process (e.g., deposited at a suitable temperature and then subjected to a second annealing process) to ensure that the reaction layer is crystalline polycrystalline silicon. Compared to amorphous silicon or non-crystalline polycrystalline silicon, the film layer of crystalline polycrystalline silicon is relatively flat and stable, allowing for better monitoring of relevant values ​​(e.g., the thickness of the film layer formed after the first annealing process). In addition, crystalline polycrystalline silicon is more sensitive to oxygen leakage during the annealing process, thus making it easier to detect anomalies during the shipping process. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a test piece according to an embodiment of the present invention;

[0025] Figures 2 to 5 This is a schematic diagram of the device cross-sectional structure corresponding to each step in the preparation process of a test piece according to an embodiment of the present invention;

[0026] Figure 6 This is a flowchart of a monitoring method for a furnace tube annealing process according to an embodiment of the present invention;

[0027] Figure 7This is a schematic diagram of the process flow of a monitoring method for furnace tube annealing in a typical application scenario of an embodiment of the present invention. Detailed Implementation

[0028] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] Figure 1 This is a schematic diagram of a test piece according to an embodiment of the present invention.

[0030] The test piece in this implementation scheme can be used for anomaly monitoring of the first annealing process of the furnace tube. The first annealing process refers to the furnace tube annealing process that requires anomaly monitoring, that is, the actual process used when processing goods (e.g., product wafers after previous processes) using this furnace tube. For example, the first annealing process can be a pure nitrogen high-temperature annealing process.

[0031] Specifically, this implementation scheme can be applied to process monitoring scenarios, specifically to the anomaly monitoring of high-temperature annealing processes using pure nitrogen in atmospheric pressure furnace tubes for semiconductors. Here, "high temperature" typically refers to the furnace tube's operating temperature of approximately 900–1100°C; in practical applications, this temperature range can be adjusted as needed. The gas pressure within the furnace tube during operation is typically one standard atmosphere. In practical applications, the atmospheric pressure furnace tube can be connected to a vacuum pump as needed to reuse the furnace tube to achieve low-pressure processes (e.g., low-pressure chemical vapor deposition processes) to a certain extent.

[0032] The furnace tube annealing process monitored in this implementation scheme can be one of the steps in manufacturing power devices (e.g., power MOSFETs (metal-oxide-semiconductor field-effect transistors, or simply metal-oxide-semiconductor field-effect transistors) or one of the steps in manufacturing BCDs (bipolar-complementary metal-oxide-semiconductor field-effect transistors-double-diffused metal-oxide-semiconductor field-effect transistors, or bipolar-CMOS-DMOS).

[0033] It should be noted that this implementation scheme can also be applied to the anomaly monitoring of other types of furnace tube annealing processes, as long as the test pieces used in the existing anomaly monitoring process (which have not been specially treated according to this implementation scheme) are affected by the furnace tube annealing process and cannot obtain accurate monitoring results. The other types of furnace tube annealing processes may, for example, use reaction gases other than nitrogen.

[0034] Specifically, refer to Figure 1 The test piece described in this embodiment may include: a substrate 201; a first protective layer 202 formed on the surface of the substrate 201; and a reaction layer 203 formed on the surface of the first protective layer 202 away from the substrate 201, wherein the reaction layer 203 is crystalline polycrystalline silicon.

[0035] Furthermore, the test piece used for monitoring the furnace tube annealing process in this embodiment is a test piece with an improved structure, manufactured using an improved preparation method. Next, we will combine... Figures 1 to 5 The preparation process of the test piece is described in detail.

[0036] In a specific implementation, refer to Figure 2 A substrate 201 is provided. The substrate 201 may be, for example, a semiconductor substrate, and the material of the semiconductor substrate may be, for example, silicon, germanium, silicon germanide, silicon carbide, gallium arsenide or indium gallium.

[0037] Further, refer to Figure 3 A first protective layer 202 is formed on the surface of the substrate 201 (e.g., the front side from the illustrated view). The first protective layer 202 can be used to isolate the surface of the substrate 201 from the outside environment (e.g., the internal environment of the furnace tube) to suppress or even avoid the reaction between the surface of the substrate 201 and the reaction gas (e.g., nitrogen) inside the furnace tube during the first annealing process.

[0038] For example, an oxidation process can be used to form a first protective layer 202 on the surface of substrate 201. The step of forming the first protective layer 202 can be completed inside a furnace tube. By introducing a certain proportion of oxygen during heating, an oxide layer can be generated on the silicon crystal surface as a protective layer (i.e., the first protective layer 202). In practical applications, a process machine other than the furnace tube used for the first furnace tube process can also be used to form the first protective layer 202.

[0039] In some embodiments, the oxidation process may include a wet oxidation process, and the reaction gas used may include one or more of oxygen, hydrogen, and dichloroethane (C2H4Cl2, DCE). For example, oxygen and hydrogen may be introduced into the furnace tube to form silicon dioxide as a first protective layer 202 on the surface of substrate 201 using a wet oxidation process.

[0040] In some embodiments, the oxidation process may include a dry oxidation process, and the reaction gas used may be, for example, oxygen.

[0041] Furthermore, in the step of forming the first protective layer 202 using an oxidation process with a furnace tube, the reaction temperature inside the furnace tube can be between 800°C and 1200°C. The temperature range can be determined by comprehensively considering factors such as the reaction rate and the thickness of the first protective layer 202. For example, too low a temperature may mean requiring more reaction time, affecting production capacity. Preferably, the temperature inside the furnace tube can be controlled to be maintained at around 1000°C during the formation of the first protective layer 202.

[0042] Furthermore, in the step of forming the first protective layer 202 using an oxidation process within a furnace tube, the reaction time of the substrate 201 within the furnace tube can be 40 to 50 minutes. For example, a wet oxidation process at 1000°C can be used on the substrate 201 for 45 minutes to form approximately 2000 angstroms on the surface of the substrate 201. Silica.

[0043] Furthermore, in the step of forming the first protective layer 202 using an oxidation process with a furnace tube, the pressure inside the furnace tube can be between 715 hPa and 725 hPa. Similar to temperature, the pressure range can also be determined by comprehensively considering factors such as reaction rate and thickness of the first protective layer 202. Preferably, it can be 720 hPa.

[0044] In some embodiments, the thickness of the first protective layer 202 can be between 1800 angstroms and 2200 angstroms. This thickness range can be determined by taking into account both the reliability of protection for the substrate 201 and manufacturing efficiency.

[0045] In a specific implementation, refer to Figure 4 A reaction layer 203 is formed on the surface of the first protective layer 202 facing away from the substrate 201. The reaction layer 203 can be used to react with the reaction gas in the furnace tube during the first annealing process, so that the thickness and surface particle size of the reaction-generated film can be detected to monitor whether there are any abnormalities in the first annealing process.

[0046] For example, it can be Figure 3 A layer of polycrystalline silicon is deposited on the formed silica surface to detect film thickness and particle size. Polycrystalline silicon is more sensitive to oxygen leakage during the annealing process, thus making it more effective at detecting anomalies during the transit process.

[0047] In some embodiments, a first deposition process can be used to form a reaction layer 203 on the surface of the first protective layer 202 facing away from the substrate 201. The step of depositing the reaction layer 203 can also be performed in a furnace tube, or it can be performed on other process equipment.

[0048] Specifically, the first deposition process can be selected from: Low Pressure Chemical Vapor Deposition (LPCVD), Atmospheric Pressure Chemical Vapor Deposition (APCVD), Plasma Chemical Vapor Deposition (PCVD), and Physical Vapor Deposition (PVD).

[0049] Furthermore, in the step of forming the reaction layer 203 using the furnace tube with the first deposition process, the reaction gas used can be silane (SiH4), and the carrier gas can be nitrogen.

[0050] Furthermore, in the step of forming the reaction layer 203 using a furnace tube with the first deposition process, the reaction temperature inside the furnace tube can be between 580°C and 620°C. For example, during the formation of the reaction layer 203 on the surface of the first protective layer 202, the temperature inside the furnace tube can be controlled to be maintained at around 620°C, allowing for a faster deposition rate and ensuring that the deposit is crystalline polycrystalline silicon, thereby ensuring the stability of the film thickness formed on the surface of the reaction layer 203 during subsequent film thickness measurement. In this embodiment, the temperature inside the furnace tube during the step of forming the reaction layer 203 cannot be too low (e.g., not lower than 580°C) to minimize the formation of amorphous polycrystalline silicon.

[0051] The difference between crystalline polycrystalline silicon and amorphous polycrystalline silicon (also known as amorphous polycrystalline silicon) lies in their internal structure: the former is predominantly crystalline with little or no amorphous structure, while the latter is partially crystalline and partially amorphous. The film stability of crystalline polycrystalline silicon is significantly better than that of amorphous or amorphous polycrystalline silicon. Furthermore, the former is significantly more sensitive to oxygen leakage during the annealing process than monocrystalline silicon. Generally, deposition temperatures below 580°C (e.g., 530°C) result in polycrystalline silicon that resembles amorphous silicon, i.e., amorphous polycrystalline silicon. However, in this application, by controlling the furnace tube temperature to be no lower than 580°C, the prepared reaction layer 203 is ensured to be crystalline polycrystalline silicon.

[0052] Furthermore, in the step of forming the reaction layer 203 using the furnace tube with the first deposition process, the reaction time of the substrate 201 in the furnace tube can be 50 to 60 minutes. For example, the LPCVD process can be used at a temperature of 620°C for 60 minutes to deposit 6000 angstroms of polycrystalline silicon on the first protective layer 202.

[0053] Furthermore, in the step of forming the reaction layer 203 using the furnace tube with the first deposition process, the pressure inside the furnace tube can be 30 to 45 Pa. In this embodiment, the pressure inside the furnace tube can be appropriately increased when forming the reaction layer 203 to improve the deposition rate.

[0054] In some embodiments, the thickness of the reaction layer 203 can be from 5950 angstroms to 6050 angstroms.

[0055] In one specific implementation, after deposition... Figure 4 After the reaction layer 203 is shown, it can be further processed, for example, by annealing using a specific menu (i.e., a second annealing process) to better ensure that the reaction layer 203 is crystalline. This specific menu can be dedicated to preparing the test piece described in this embodiment. This helps avoid subsequent uses (e.g., Figure 6 The thickness of the reaction layer 203 surface film is unstable during monitoring in step S102.

[0056] Specifically, refer to Figure 5 Before annealing (referred to as the second annealing process), a second protective layer 204 can be formed on the surface of the reaction layer 203 opposite to the first protective layer 202. The second protective layer 204 can play a protective and isolating role in the specific menu described in this embodiment, preventing the reaction layer 203 from contacting the reaction gases in the furnace tube during the subsequent second annealing process. This step can also be carried out in the furnace tube.

[0057] For example, similar to forming the first protective layer 202, a second protective layer 204 can be formed on the surface of the reaction layer 203 opposite to the first protective layer 202 using a wet oxidation process or a dry oxidation process. The material of the second protective layer 204 can be the same as that of the first protective layer 202; for example, both can be silicon dioxide.

[0058] In some embodiments, in the step of forming a second protective layer 204 on the surface of the reaction layer 203 opposite to the first protective layer 202, the reaction gas used can be oxygen, the volume of the reaction gas introduced into the furnace tube can be 7 to 10 liters, the reaction time can be 27 to 33 minutes, the reaction temperature can be 720°C to 880°C, and the pressure in the furnace tube during the reaction can be 715 hPa to 725 hPa. For example, a first deposition process is used in the furnace tube to form a second protective layer 204. Figure 4 After the reaction layer 203 shown, the furnace tube can be heated to 800°C and 10 liters of oxygen can be introduced to oxidize for 30 minutes, so as to form another layer of silicon dioxide on the surface of the reaction layer 203 as a second protective layer 204. During the reaction, the pressure inside the furnace tube is maintained at about 720 hPa.

[0059] Thus, by introducing a larger dose of oxygen into the furnace tube, a second protective layer 204 is formed on the surface of the reaction layer 203 before annealing.

[0060] Furthermore, after forming the second protective layer 204, a second annealing process can be performed on the test wafer using a furnace tube to change at least a portion of the molecular structure of the reaction layer 204 into a crystalline state. Specifically, based on the deposition of crystalline polycrystalline silicon by controlling the process parameters of the first deposition process (e.g., reaction temperature and / or pressure), the annealing treatment further ensures the uniformity of the crystalline distribution within the reaction layer 203, that is, ensures that the molecular structure at all points in the reaction layer 203 is crystalline.

[0061] In the second annealing process using a furnace tube on the test piece, the process parameters used may differ from those used in the first annealing process. Specifically, the process parameters for the first annealing process are determined based on the furnace tube annealing process required for anomaly monitoring, and vary depending on the actual process parameters used when processing goods using the furnace tube. Conversely, the process parameters for the second annealing process are used to further ensure that the reaction layer 203 is entirely crystalline.

[0062] In some embodiments, the process parameters used in the second annealing process may include: the reaction gas used may be nitrogen, the volume of the reaction gas input into the furnace tube may be 15 to 20 liters, the reaction time may be 1.5 to 2 hours, the reaction temperature may be 1050°C to 1100°C, and the pressure in the furnace tube during the reaction may be 715 hPa to 725 hPa.

[0063] For example, after depositing the reaction layer 203 (e.g., polycrystalline silicon), the furnace tube temperature is first raised to 800°C and 10 liters of oxygen are introduced for oxidation for 30 minutes to form a second protective layer 204 (e.g., silicon dioxide) on the surface of the reaction layer 203. Then, the furnace tube temperature is further raised to 1100°C and 20 liters of nitrogen are introduced for annealing for 2 hours to ensure that the polycrystalline silicon is crystalline and to prevent unstable film thickness in subsequent use. Furthermore, nitrogen can be introduced into the furnace tube while waiting for it to heat up from 800°C to 1100°C.

[0064] Furthermore, after the second annealing process is completed, an etching process can be used to remove the second protective layer 204, so that the reaction layer 203 is exposed on the surface of the test piece, resulting in... Figure 1 The test piece is shown. Therefore, the reaction layer 203, after the specific menu annealing treatment described above, is more prone to oxidation during the first annealing process. If oxygen leakage occurs during the first annealing process, the reaction layer 203 used in this embodiment can more accurately detect the oxygen leakage problem, thereby better identifying abnormalities in the transit process.

[0065] In some embodiments, the etching process may include a wet etching process, and the etching solution used in the wet etching process may include an acidic solution, such as hydrofluoric acid (HF). For example, a wet etching process of HF+SC1+SC2 can be used to remove the second protective layer 204 on the surface of the test piece. SC1 (Standard Cleaning 1) and SC2 (Standard Cleaning 2) are two steps of RCA cleaning: the SC1 cleaning process uses an APM solution (ammonia-hydroxide-hydrogen peroxide-water mixture) of the RCA cleaning method to remove organic matter and particles; the SC2 cleaning process uses a solution typically composed of 6 parts deionized water, 1 part hydrochloric acid, and 1 part hydrogen peroxide or HPM (hydrochloric acid / peroxide mixture), which effectively removes residual trace metal (ionic) contaminants, some of which may have been introduced in the SC1 cleaning step.

[0066] Alternatively, an alkaline etching solution can be used to remove the second protective layer 204, such as one or more of ammonia (NH4OH) or potassium hydroxide aqueous solution (KOH).

[0067] Alternatively, different types and / or different acidity / alkalinity etching solutions can be used to perform multiple etching processes on the test piece to ensure that the second protective layer 204 is completely removed, so that all parts of the surface of the reaction layer 203 can be exposed.

[0068] In some embodiments, the etching process may include a dry etching process, and the etching gas used in the dry etching process may include one or more of octafluoroisobutylene (C4F8), hydrobromic acid (HBr), boron trichloride (BCl3), carbon tetrafluoride (CF4), chlorine (CL2), and trifluoromethane (CHF3).

[0069] In some embodiments, wet etching and dry etching processes can be used sequentially to perform multiple etching processes on the sample substrate to ensure complete removal of the second protective layer 204, so that all parts of the surface of the reaction layer 203 can be exposed.

[0070] Thus, the reaction layer 203 is prepared by a special process (for example, the reaction layer is deposited under suitable temperature conditions and then subjected to a second annealing process) to ensure that the reaction layer is crystalline polycrystalline silicon.

[0071] From above, after Figures 2 to 5 The preparation process described in the illustrated embodiment yields the following product: Figure 1 The test piece shown can be used as a control piece accompanying the shipment for execution. Figure 6 Steps S101 and S102 in the illustrated embodiment are used to monitor the first annealing process.

[0072] In a specific implementation, refer to Figure 6The monitoring method for the furnace tube annealing process described in this embodiment may include the following steps:

[0073] Step S101: The test piece is subjected to a first annealing process using the furnace tube to obtain a treated test piece, wherein the surface of the reaction layer of the treated test piece is at least partially reacted after being treated by the first annealing process.

[0074] Step S102: Detect the reaction layer of the processed test piece for anomaly monitoring.

[0075] In some embodiments, during the step of performing the first annealing process on the test wafer using the furnace tube, at least one product wafer is also subjected to the first annealing process using the furnace tube. In other words, the test wafer with a first protective layer and a reactive layer sequentially formed on its surface can be used as a control wafer and fed into the furnace tube along with the product wafer to be processed for the first annealing process. Therefore, the test wafer that has undergone the furnace tube annealing process can be detected with each shipment, thereby enabling daily monitoring of the furnace tube annealing process and facilitating timely detection of anomalies during shipment.

[0076] Furthermore, in step S102, the thickness of the film layer formed after the reaction layer undergoes the first annealing process, as well as the particle size of the film layer surface, can be detected. The particle size (also known as the particle count) characterizes the surface morphology of the reaction layer on the treated test piece. For example, a scanning probe microscope can be used to observe the surface morphology of the reaction layer, such as roughness, the number of grown particles, and the degree of particle undulation.

[0077] It should be noted that the action of manufacturing the test piece using the aforementioned preparation process and the action of performing the first annealing process on the test piece using a furnace tube in step S101 can be performed in a discontinuous time dimension. That is, they can be performed in advance. Figures 1 to 5 The fabrication process shown is used to prepare a test wafer. The prepared test wafer can be temporarily stored elsewhere and then placed in the furnace along with the product wafer during the next processing of the product wafer. Alternatively, after preparing the test wafer, the product wafer can be placed immediately in the same furnace to undergo the first annealing process together with the test wafer.

[0078] In one specific implementation, the test piece can be reused, that is, after... Figures 1 to 5 The test piece obtained by the preparation process described in the embodiment can be repeatedly placed into the furnace tube for the first annealing process, and the reaction layer 203 is detected after each first annealing process to obtain monitoring results.

[0079] Furthermore, before the next use of the furnace tube to perform the first annealing process on the test piece, the monitoring method described in this embodiment may also include the step of: performing a first etching process on the treated test piece to remove the portion of the surface of the reaction layer 203 that reacted during the first annealing process.

[0080] For example, refer to Figure 7 After the above Figures 1 to 5 After the test piece is prepared by the process shown, it can be used in a furnace tube at high temperature with pure nitrogen for no more than m times, where m is a positive integer. After each use in the furnace tube, before being placed in the furnace tube for the next use, it must first undergo a recycling process (i.e., the first etching process). The recycling process can use a wet etching process to clean the surface of the treated test piece to remove the nitride layer on the substrate surface.

[0081] Furthermore, after the test piece is reused more than 5 times, a second cleaning process can be performed on the processed test piece after the last execution of step S102 to remove the reaction layer 203 and the first protective layer 202.

[0082] In some embodiments, the second etching process may include a wet etching process, specifically using a variety of different etching solutions to sequentially clean the test wafer to remove different film layers. For example, hydrofluoric acid can be used to clean away the first protective layer 202 (e.g., silicon dioxide), and a mixed solution of hydrofluoric acid and nitric acid can be used to clean away the reaction layer 203 (e.g., polysilicon).

[0083] In some embodiments, the value of m can be fixed, for example, m = 5 times. When performing this embodiment, the test piece is reused 5 times after passing through the furnace tube, i.e., all surface films are washed away, and the process is repeated. Figures 2 to 6 The preparation process is shown in the diagram. Five times is a relatively optimal value determined in the laboratory. Exceeding this number results in severe surface damage to the reaction layer 203, requiring the reaction layer 203 to be prepared again.

[0084] In some embodiments, the value of m can be dynamically changed. After each use of the furnace tube, it can be determined whether a second cleaning process should be performed on the treated test piece based on the abnormal monitoring results of step S102. In other words, when different process parameters are used in the first annealing process, the service life (i.e., the value of m) of the test piece may also differ.

[0085] For example, the degree of damage to the surface of the treated test wafer can be measured based on the abnormal monitoring results (e.g., particle size) from step S102. If the damage is severe, it is determined that a second etching process is required to re-grow a first protective layer 202 and a reactive layer 203 on the substrate.

[0086] In some embodiments, continue to refer to Figure 7During the second etching process, all film layers on the surface of the treated test piece can be removed, leaving only the layers shown in the image. Figure 2 The semiconductor substrate 201 is shown. Then, the following is performed. Figures 3 to 6 The test piece was prepared using the process steps shown.

[0087] In one variation, during the second etching process, only the reactive layer 203 can be removed, while the first protective layer 202 remains. In other words, during each large cycle, it can be removed from the reactive layer 203, leaving the first protective layer 202 intact. Figure 3 Starting with the semiconductor device structure shown, the following steps are executed sequentially. Figures 4 to 5 The process steps shown yielded the following product: Figure 1 The test piece shown is an example of this. This reduces the number of steps and improves preparation efficiency.

[0088] Therefore, by adopting this implementation scheme, a first protective layer 202 is formed on the surface of the test piece to protect the substrate, preventing nitriding damage to the substrate during the furnace tube annealing process. Test pieces unaffected by nitriding can be used at any time as needed, thereby enabling timely monitoring of abnormalities in the furnace tube annealing process. Furthermore, the first protective layer 202 also helps to avoid the impact of test piece nitriding on the accuracy of abnormality monitoring results and extends the service life of the test piece.

[0089] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A test piece, characterized in that, include: substrate; A first protective layer is formed on the surface of the substrate; A reaction layer is formed on the surface of the first protective layer away from the substrate, and the reaction layer is crystalline polycrystalline silicon. The test piece is used to monitor for abnormalities in the first annealing process of the furnace tube.

2. The test piece according to claim 1, characterized in that, The thickness of the reaction layer is 5950 angstroms to 6050 angstroms; and / or, the thickness of the first protective layer is 1800 angstroms to 2200 angstroms; and / or, the material of the first protective layer includes silicon dioxide.

3. A method for preparing a test piece, wherein the test piece is used for anomaly monitoring of the first annealing process of a furnace tube, characterized in that, The preparation method includes: A substrate is provided, wherein a first protective layer is formed on the surface of the substrate; A reaction layer is formed on the surface of the first protective layer away from the substrate, and the reaction layer is crystalline polycrystalline silicon.

4. The preparation method according to claim 3, characterized in that, The step of forming a reactive layer on the surface of the first protective layer opposite to the substrate includes: The reaction layer is formed on the surface of the first protective layer away from the substrate using a first deposition process, wherein the reaction gas used is silane, the carrier gas is nitrogen, and the reaction temperature is 580°C to 620°C; and / or The formation process of the first protective layer includes: The first protective layer is formed on the surface of the substrate by an oxidation process, wherein the reaction gas used includes one or more of oxygen, hydrogen, and dichloroethane, the reaction temperature is 800°C to 1200°C, and the reaction time is 40 to 50 minutes.

5. The preparation method according to claim 4, characterized in that, After forming a reactive layer on the surface of the first protective layer away from the substrate, the preparation method further includes: A second protective layer is formed on the surface of the reactive layer opposite to the first protective layer; The test piece was subjected to a second annealing process using the furnace tube. The second protective layer is removed by an etching process.

6. The preparation method according to claim 5, characterized in that, In the step of forming a second protective layer on the surface of the reaction layer opposite to the first protective layer, the reaction gas used is oxygen, the volume of the reaction gas introduced into the furnace tube is 7 to 10 liters, the reaction time is 27 to 33 minutes, the reaction temperature is 720°C to 880°C, and the pressure in the furnace tube during the reaction is 715 hPa to 725 hPa; and / or In the second annealing process of the test piece using the furnace tube, the reaction gas used is nitrogen, the volume of the reaction gas input into the furnace tube is 15 to 20 liters, the reaction time is 1.5 to 2 hours, the reaction temperature is 1050°C to 1100°C, and the pressure in the furnace tube during the reaction is 715 hPa to 725 hPa.

7. A method for monitoring a furnace tube annealing process, characterized in that, include: The furnace tube is used to perform a first annealing process on at least one product wafer and a test wafer to obtain a processed test wafer. The test wafer includes a substrate, a first protective layer formed on the surface of the substrate, and a reaction layer. The reaction layer is formed on the surface of the first protective layer away from the substrate. The reaction layer is crystalline polycrystalline silicon. The surface of the reaction layer of the processed test wafer away from the first protective layer is treated by the first annealing process and at least partially reacts. The reaction layer of the processed test piece is inspected for anomaly monitoring.

8. The monitoring method according to claim 7, characterized in that, The detection of the reaction layer of the treated test piece includes: detecting the thickness of the film formed after the reaction layer of the treated test piece has undergone a first annealing process and / or the particle size of the film surface.

9. The monitoring method according to claim 7, characterized in that, The test piece is reusable. Before the next use of the furnace tube to perform the first annealing process on the test piece, the monitoring method further includes: The treated test piece is subjected to a first etching process to remove the portion of the reactive layer that reacted during the first annealing process on the surface of the reactive layer away from the first protective layer.

10. The monitoring method according to claim 7, characterized in that, Also includes: Based on the abnormal monitoring results, a second cleaning process is determined to be performed on the processed test piece to remove the reaction layer and the first protective layer.

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