Analysis method and improvement method for wafer back gold abnormity reason

Abstract

The invention provides an analysis method and an improvement method for wafer back gold abnormity reasons, and the analysis method comprises the steps: verifying whether the wafer back gold is abnormal or not in different regional environments, determining an abnormal regional environment causing the back gold abnormity, and preliminarily determining environmental factors causing the back gold abnormity in the abnormal regional environment; collecting data of environmental factors in different regional environments, and further determining the environmental factors causing the back gold abnormality; respectively deteriorating each microenvironment in the environmental factors to verify whether the back metal is abnormal or not; and determining the microenvironment causing the back gold abnormality. According to the method, the wafer back gold is verified in different regional environments, the environmental factors causing the back gold abnormality are determined by controlling a single environmental variable and combining preliminary judgment and data collection, and a deterioration experiment is performed on each microenvironment in the environmental factors to verify the microenvironment causing the back gold abnormality. Factors causing wafer back gold abnormity can be quickly locked, the trial and error cost is reduced, and further expansion of online loss is avoided.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for analyzing and improving the causes of abnormal back-gold deposits on wafers. Background Technology

[0002] IGBTs (Insulated-Gate Bipolar Transistors) require metal deposition on the back side to bring out the P+ electrode as the collector. Commonly used metals include aluminum, titanium, silver, or nickel-vanadium alloys.

[0003] During the production process, it was discovered that after the back-end metal deposition of IGBTs was completed, some wafers would turn yellow, which would affect subsequent packaging and wire bonding, resulting in the inability to ship and causing a serious reduction in the output / input percentage (line yield). The cause of the yellowing could not be identified for a long time. Summary of the Invention

[0004] The purpose of this invention is to provide an analysis method and improvement method for wafer back-gold abnormality, which can quickly identify the factors causing wafer back-gold abnormality, reduce trial and error costs, and prevent further expansion of online losses.

[0005] To address the aforementioned technical problems, this invention provides a method for analyzing the causes of wafer back-side gold anomalies, comprising the following steps:

[0006] The presence of abnormalities in the back gold of the wafer was verified under different regional environments. The abnormal regional environments that caused the abnormalities were identified, and the environmental factors that caused the abnormalities in the abnormal regional environments were preliminarily determined.

[0007] Data on environmental factors that cause the anomaly of gold backing were collected in different regions to further identify the environmental factors that cause the anomaly of gold backing.

[0008] Each microenvironment among the environmental factors that exacerbate the anomaly of the gold backing is used to verify whether the gold backing is abnormal; and

[0009] Identify the microenvironment that causes the anomaly on the gold back.

[0010] Optionally, methods for initially determining the environmental factors in the abnormal area that lead to the gold-back anomaly include:

[0011] The environment of the abnormal area was sampled, and the content of each environmental factor was analyzed.

[0012] Based on the content of the aforementioned environmental factors, the environmental factors leading to the abnormal gold backing were preliminarily determined.

[0013] Optionally, while collecting data on environmental factors that cause back-gold anomalies in different regional environments, the method also includes: collecting data on the regions on the wafer where back-gold anomalies occur to determine whether the back-gold anomalies are related to the region.

[0014] Optionally, during the process of collecting areas on the wafer where back gold anomalies occur, the wafer can be placed in an environment that is more affected by environmental factors and an environment that is less affected by environmental factors.

[0015] Optionally, areas more affected by environmental factors include the outbound inspection area, the testing plant area, the BGBM area, or the BGBM nitrogen cabinet, while areas less affected by environmental factors include the yellow light area.

[0016] Optionally, the environmental area includes an outgoing inspection area, a testing plant area, a BGBM area, a BGBM nitrogen chamber, and a yellow light area, with the yellow light area used for comparison to determine whether there are any abnormalities in environmental factors.

[0017] Optionally, the environmental factors include VOCs, benzene compounds, halogenated organic compounds, anions, and cations.

[0018] Optionally, the microenvironment among the environmental factors includes Cl-, NO3-, and SO42-. 2- F- or NH4 + .

[0019] Optionally, the back gold anomaly includes a yellowing of the back gold.

[0020] Accordingly, the present invention also provides a method for improving wafer back-gold anomalies, comprising the following steps:

[0021] The presence of abnormalities in the back gold of the wafer was verified under different regional environments. The abnormal regional environments that caused the abnormalities were identified, and the environmental factors that caused the abnormalities in the abnormal regional environments were preliminarily determined.

[0022] Data on environmental factors that cause the anomaly of gold backing were collected in different regions to further identify the environmental factors that cause the anomaly of gold backing.

[0023] Each microenvironment among the environmental factors that exacerbate the back gold anomaly is used to verify whether the back gold is abnormal.

[0024] Identify the microenvironment that caused the anomaly on the gold back; and

[0025] A filtration device is used to filter the microenvironment that causes abnormal gold backing.

[0026] Optionally, the microenvironment leading to wafer back-gold abnormalities includes anions, such as Cl- and NO3-. - or SO4 2- .

[0027] Optionally, an anion exchange filter can be used to filter the microenvironment.

[0028] In summary, the method for analyzing the causes of wafer back-gold anomalies provided by this invention first verifies whether there is an anomaly in the wafer back-gold under different regional environments, identifies the abnormal regional environment causing the anomaly, and preliminarily identifies the environmental factors causing the anomaly in the abnormal regional environment; then, it collects data on the environmental factors causing the anomaly in different regional environments to further identify the environmental factors causing the anomaly; next, it deteriorates each microenvironment among the environmental factors causing the anomaly to verify whether the back-gold is abnormal; and finally, it identifies the microenvironment causing the anomaly. This invention verifies the wafer back-gold under different regional environments, determines the environmental factors causing the anomaly by controlling a single environmental variable and combining preliminary judgment and data collection, and conducts deterioration experiments on each microenvironment among the environmental factors to verify the microenvironment causing the anomaly. This can quickly pinpoint the factors causing the wafer back-gold anomaly, reduce trial-and-error costs, and prevent further expansion of online losses.

[0029] In the method for improving wafer back-gold defects provided by this invention, after identifying the microenvironment causing the defect, only a filtration device is needed to filter that microenvironment. There is no need to add filtration devices to all areas, thus saving costs and avoiding additional expenses. Simultaneously, adding a filtration device maintains environmental stability, thereby improving the wafer back-gold defect problem and enhancing device performance. Attached Figure Description

[0030] Figure 1 This is a flowchart of a method for analyzing the causes of wafer back-gold abnormalities, provided in an embodiment of the present invention.

[0031] Figure 2a This is a schematic diagram of anion and cation data statistics in the yellow light region provided in an embodiment of the present invention.

[0032] Figure 2b This is a schematic diagram of anion and cation data statistics for a test plant area provided in an embodiment of the present invention.

[0033] Figure 2c This is a schematic diagram of anion and cation data statistics in the outgoing inspection area provided by an embodiment of the present invention.

[0034] Figure 2d This is a schematic diagram of anion and cation data statistics for the BGBM region provided in an embodiment of the present invention.

[0035] Figure 2e This is a schematic diagram of the anion and cation data statistics of the BGBM nitrogen cabinet provided in an embodiment of the present invention.

[0036] Figure 2f This is a schematic diagram of the anion and cation data statistics of the BGBM cutting region provided in an embodiment of the present invention.

[0037] Figures 3a to 3c This is a schematic diagram illustrating the yellowing of the gold-backed surface of a wafer under a 5% hydrochloric acid environment.

[0038] Figures 4a to 4h This is a schematic diagram illustrating the yellowing of the gold-backed surface of a wafer under a 10% hydrochloric acid environment.

[0039] Figures 5a to 5d This is a schematic diagram showing the yellowing of the gold back surface of a wafer under 25% nitric acid conditions.

[0040] Figures 6a to 6d This is a schematic diagram illustrating the yellowing of the gold back surface of a wafer under a high-concentration sulfuric acid environment. Detailed Implementation

[0041] To make the objectives, advantages, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clarify the explanation of the embodiments of this invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and may sometimes use different scales.

[0042] As used herein, the singular forms “a,” “an,” and “the” include plural objects unless otherwise expressly indicated. As used herein, the term “or” is generally used to include “and / or” unless otherwise expressly indicated. As used herein, the term “a number” is generally used to include “at least one” unless otherwise expressly indicated. As used herein, the term “at least two” is generally used to include “two or more” unless otherwise expressly indicated. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature.

[0043] Based on the aforementioned issue of wafer back-gold anomalies, the inventors, through experience, confirmed that the problem is primarily caused by environmental factors. Therefore, this invention mainly analyzes and confirms these environmental factors. The core idea of ​​this invention is to determine the root cause of wafer back-gold anomalies through a reverse degradation experiment by controlling a single environmental variable and combining it with long-term environmental monitoring.

[0044] Figure 1 This is a flowchart illustrating a method for analyzing the causes of wafer back-side gold defects according to an embodiment of the present invention. Please refer to it. Figure 1 As shown, the method for analyzing the causes of wafer back-side gold anomalies provided in this embodiment of the invention includes the following steps:

[0045] S1: Verify whether there are any abnormalities in the back gold of the wafer under different regional environments, determine the abnormal regional environment that causes the abnormal back gold, and preliminarily determine the environmental factors in the abnormal regional environment that cause the abnormal back gold.

[0046] S2: Collect data on environmental factors that cause abnormal gold backing in different regional environments, and further identify the environmental factors that cause abnormal gold backing.

[0047] S3: Deteriorate each microenvironment among the environmental factors that cause the back gold anomaly to verify whether the back gold is abnormal; and

[0048] S4: Identify the microenvironment that causes the back gold anomaly.

[0049] Back-gold deposited on the back of a wafer is a metal deposited on the wafer's back side. This invention provides a method for analyzing and determining what factors cause abnormalities in the metal on the wafer's back side. This invention is applicable to any power device that requires back-gold deposition, such as IGBTs (Insulated-Gate Bipolar Transistors) and Trench MOSFETs (Trench Metal-Oxide-Semiconductor Field-Effect Transistors).

[0050] In this embodiment of the invention, the case of yellowing back gold is used as an example of the gold-backed abnormality, but it is also applicable to other cases of gold-backed abnormality.

[0051] In step S1, the presence of abnormalities in the back gold of the wafer is verified under different regional environments to determine the abnormal regional environment that causes the abnormality, and the environmental factors that cause the abnormality in the abnormal regional environment are preliminarily determined.

[0052] In this embodiment of the invention, wafers with gold backing are placed in different environmental regions to verify which region exhibits anomalies in the gold backing. The regions exhibiting these anomalies are designated as anomalous regions. Then, the environmental factors causing the gold backing anomalies in these anomalous regions are preliminarily determined. The method for preliminarily determining the environmental factors causing the gold backing anomalies in these anomalous regions includes: sampling the environment in the anomalous region, analyzing the content of each environmental factor, and then preliminarily determining the environmental factors causing the gold backing anomalies based on the content of the environmental factors.

[0053] In one embodiment of the present invention, the different regional environments include areas that may affect the back gold coating, namely, the area where the back gold coating is fabricated and the areas it passes through after fabrication. For example, the regional environments include the Outgoing Quality Assurance (OQA) area, the testing facility area, and the BGBM (Backside Grinding and Backside Metal) area. It should be noted that the OQA and testing facilities involve inspection and testing, and the inspection and testing times are generally greater than 2 hours. The BGBM area is equipped with a BGBM nitrogen cabinet, and the wafer must be placed in the BGBM nitrogen cabinet when no wafer operations are required. Wafer operations in the BGBM area are also completed within 0.5 hours. Since the operation time in the BGBM area is relatively short, in this embodiment, the BGBM area is replaced by a BGBM nitrogen cabinet. That is, in this embodiment of the present invention, the presence of abnormalities in the wafer back gold coating is verified under different regional environments, where the regional environments include the OQA area, the testing facility area, and the BGBM nitrogen cabinet.

[0054] In one embodiment of the present invention, the presence of anomalies in the back gold is verified within the same time period in three different regional environments. For example, six wafers are provided, and metal is formed on the back gold of the wafers. They are placed in different regional environments for a period of time, and the yellowing of the back gold is detected.

[0055] Table 1

[0056]

[0057]

[0058] Table 1 shows the placement of 6 wafers. Two wafers are placed in the outbound inspection area, two in the testing area, and two in the BGBM nitrogen cabinet. One wafer is a cleaned POD (Polydiment Object Deposit Box), and the other is an uncleaned POD. A POD refers to a white material box used in the factory to hold wafers. A cleaned POD is one from which the wafers will be removed for verification, while an uncleaned POD is one from which the wafers will not be cleaned. After placing the wafers, the back gold is checked for yellowing every 24 hours.

[0059] After 24 hours, inspection revealed that both wafers in the BGBM nitrogen cabinet had turned yellow. Wafers in the outgoing inspection area with cleaned PODs were yellowing, while those without cleaned PODs were not. Wafers in the testing area were not yellowing. After 48 hours, the number of yellowed wafers remained the same, but the two cleaned POD wafers showed a tendency to yellow. The results after 72 hours were essentially the same as those after 48 hours.

[0060] The above experiments show that the BGBM nitrogen chamber is malfunctioning. Environmental sampling and analysis were then conducted on the BGBM nitrogen chamber.

[0061] In one embodiment of the present invention, while performing environmental sampling and analysis on the BGBM nitrogen cabinet, the nitrogen cabinets in different areas are also verified to determine whether the nitrogen cabinets in other areas will cause the back gold to turn yellow, and the BGBM area is also verified.

[0062] Table 2

[0063] Number of wafers 24 hours 48 hours Nitrogen cabinet in the shipping area 1 Not yellowed Not yellowed Nitrogen cabinet at the testing plant 1 Not yellowed Not yellowed BGBM Nitrogen Chamber 1 Not yellowed Yellowing BGBM area 1 Not yellowed Yellowing

[0064] Table 2 shows the results of verifying the yellowing of the gold backing in different regions, including the nitrogen cabinet and the BGBM region. One wafer was placed in each of the four regions, and the yellowing of the gold backing was checked every 24 hours. Table 2 shows that yellowing of the gold backing was observed in both the BGBM nitrogen cabinet and the BGBM region after 48 hours. This indicates that the region causing the gold backing abnormality is the BGBM nitrogen cabinet, which is an abnormal environment. In this embodiment, the BGBM region is also an abnormal environment.

[0065] Table 3

[0066]

[0067] Table 3 shows the results of environmental sampling and analysis in the BGBM region and inside the BGBM nitrogen tank. As can be seen from Table 3, the total VOC (volatile organic compounds) content inside the BGBM nitrogen tank is higher than that in the BGBM region, and the anion concentration inside the BGBM nitrogen tank is also higher than that in the BGBM region, by at least one order of magnitude, especially Cl. - The concentration was even three orders of magnitude higher.

[0068] Therefore, a preliminary assessment suggests that abnormal environmental fluctuations can cause the hair on the back to turn yellow, possibly due to Cl. - This is one of the factors causing the yellowing, and it is further hypothesized that anions may also cause the back gold to turn yellow. That is, in this step, it is preliminarily determined that the abnormal environment causing the back gold abnormality is the BGBM nitrogen cabinet and the BGBM area, and the environmental factors causing the back gold abnormality in the abnormal environment are anions, especially Cl-.

[0069] In step S2, data on environmental factors that cause back gold anomalies in different regional environments are collected to further identify the environmental factors that cause back gold anomalies.

[0070] The environmental factors causing the gold-back anomaly were initially identified in the previous step, such as anions. This step involves collecting data on these environmental factors in different regions, specifically anion data, to further determine whether anions are indeed causing the gold-back anomaly. In one embodiment of this invention, data on both cations and anions are collected simultaneously.

[0071] In one embodiment of the present invention, the environmental area includes an outbound inspection area, a testing plant area, a BGBM area, a BGBM nitrogen chamber, and a yellow light area. The yellow light area serves as a comparison to determine whether there are any abnormalities in the environmental factors of the other areas. Since the yellow light area is equipped with a chemical filter, which can reduce the presence of anions and cations in the environment, data on anions and cations in the yellow light area are also collected and compared with the data from the other areas to determine whether there are any abnormalities in the anions and cations in the other areas.

[0072] Figures 2a to 2f This is a schematic diagram illustrating the statistical data of cations and anions in the yellow light area, testing plant area, outgoing inspection area, BGBM area, BGBM nitrogen cabinet, and BGBM cutting area, provided in an embodiment of the present invention. The horizontal axis represents the date (in days, with the starting day of statistics designated as day 1, and 3 representing day 3), the vertical axis represents the ion concentration, and the horizontal black line represents the specification line. In this embodiment, the collected anions are Cl... - NO3 - SO4 2- With F-, oxygen ions are collected by NH4. + Of course, it's not limited to that.

[0073] Figure 2a This is a schematic diagram of anion and cation data statistics in the yellow light region provided in an embodiment of the present invention. Please refer to it. Figure 2a As shown, the concentrations of anions and cations in the yellow light (LT) region are relatively stable and below the specification line. Figure 2b This is a schematic diagram of anion and cation data statistics for a test plant area provided in an embodiment of the present invention. Please refer to it. Figure 2b As shown, starting from day 31, the ion concentration in the testing area fluctuated significantly, especially the Cl concentration. - With NO3 - It exceeds the specification line. Figure 2cThis is a schematic diagram of anion and cation data statistics in the outgoing inspection area provided by an embodiment of the present invention. Please refer to it. Figure 2c As shown, starting from day 28, the ion concentration in the Outbound Quality Assurance (OQA) area fluctuated significantly, especially the Cl concentration. - With NO3 - It exceeds the specification line. Figure 2d This is a schematic diagram of cation and anion data statistics for the BGBM region provided in an embodiment of the present invention. Figure 2e This is a schematic diagram of the anion and cation data statistics for the BGBM nitrogen tank. Figure 2f This is a schematic diagram showing the statistical data of anions and cations in the BGBM cleavage region. Please refer to it. Figures 2d to 2f As shown, the fluctuation range of anions and cations in the BGBM region, BGBM nitrogen chamber, and BGBM die saw region has been relatively large, and some of the ions have exceeded the specification limits.

[0074] from Figures 2a to 2f It is known that the environment in areas without chemical filters fluctuates significantly, posing a risk of exceeding specifications and becoming uncontrollable. Furthermore, the test results for anions and cations vary across different time periods and regions, further illustrating that the environment is an unstable factor.

[0075] In one embodiment of the present invention, while collecting data on environmental factors causing back-gold abnormalities in different regional environments, the method also includes: collecting regions on the wafer where back-gold abnormalities occur to determine whether the abnormalities are related to the region. During the process of collecting regions on the wafer where back-gold abnormalities occur, the wafer is placed in both a region heavily affected by environmental factors and a region less affected by environmental factors. For example, regions heavily affected by environmental factors include the outbound inspection area, the testing plant area, the BGBM area, or the BGBM nitrogen chamber; regions less affected by environmental factors include the photolithography area.

[0076] As described above, the yellow light area is the region where the chemical filter is installed, and its environmental fluctuations are relatively small, making it suitable for comparison with other regions where environmental fluctuations are larger. In other embodiments, other regions where the chemical filter is installed can also be selected, and it is not limited to the yellow light area.

[0077] In one embodiment of the present invention, nine wafers with only back-side metallization (BSM) processing are selected and placed in the BM (backside metallization) nitrogen cabinet of the BGBM region, the BM region of the BGBM region, and the yellow light region, respectively. In each region, one uncleaned POD wafer, one cleaned POD wafer, and one bare wafer are placed, where a bare wafer refers to a wafer with only back-side gold forming on its surface. The yellowing of the wafers is observed every 24 hours.

[0078] Table 4

[0079]

[0080]

[0081]

[0082]

[0083]

[0084] The results for the nine wafers at the same time point should be in the same row. Due to horizontal size limitations, the results for the three regions at the same time point are placed in different rows and tables, and are collectively presented as Table 4. Table 4 shows the inspection results of the nine wafers placed in the BGBM-BM nitrogen cabinet, the BGBM-BM region, and the yellow light region for different times. As can be seen from Table 4, the bare wafers in the BGBM-BM region showed slight yellowing after 192 hours. The wafers in the BGBM-BM nitrogen cabinet and the BGBM-BM region gradually yellowed after 192 hours, and yellowing also appeared in the yellow light region after 408 hours. In addition, the yellowing first occurred around the edges, and then the width of the yellowing increased until the entire surface was slightly yellow and then the entire surface was yellowed.

[0085] It should be noted that in Table 4, the wafer is divided into 5 regions, including the central region and the outer region surrounding the central region. Then, the outer region is divided into four regions along the horizontal and vertical directions: S1 is located above and to the left of the central region; S2 is located below and to the left of the central region; S3 is located below and to the right of the central region; S4 is located above and to the right of the central region; and the central region is S5. The specific locations of these regions can be found in [reference needed]. Figures 3a to 3c As shown.

[0086] As shown in Table 4 above, bare wafers are more prone to yellowing than POD wafers, and the degree of yellowing increases over time. Furthermore, yellowing also appears in the yellow light area over time, further verifying that there are environmental factors that induce yellowing of the back light of the wafer.

[0087] In step S3, each microenvironment among the environmental factors that cause the back gold abnormality is worsened to verify whether the back gold is abnormal.

[0088] In this embodiment, the environmental factors causing the back gold anomaly include cations and anions, and the microenvironment among the environmental factors causing the back gold anomaly includes Cl. - NO3 - SO4 2- F - or NH4 + The following methods deteriorate the microenvironment to determine whether it will cause the wafer to yellow.

[0089] In one embodiment of the present invention, the microenvironment Cl- is first degraded, i.e., a high concentration of Cl- is provided. For example, 5% hydrochloric acid (HCl) is placed in a measuring cup, and the wafer and the measuring cup are placed in the same sealed POD. At the same time, 10% hydrochloric acid (HCl) is placed in a measuring cup, and the wafer and the measuring cup are placed in the same sealed POD. In addition, a wafer is provided separately placed in a sealed POD. Then, the yellowing of the back gold is observed every 6 hours.

[0090] Observation of the yellowing of the back wafers revealed that wafers placed alone in a sealed POD did not yellow, while wafers placed at the same time as the measuring cups yellowed over time. Figures 3a to 3c This diagram illustrates the yellowing of the gold-back surface of a wafer under a 5% hydrochloric acid environment. For wafers sealed together with a measuring cup containing 5% hydrochloric acid, no yellowing was observed after 6 hours; after 12 hours, please refer to [the provided text]. Figure 3a As shown, region S4 has an area of ​​0.25 cm². 2 The macula; please refer to the following after 18 hours. Figure 3a As shown, the macular area in region S4 remains at 0.25 cm². 2 Please refer to the following after 24 hours. Figure 3b As shown, the macular area in region S4 is 0.25 cm². 2 Yellow spots also appeared in area S5, with a slightly yellowish ring around the edge (i.e., a ring of tiny yellow dots about 0.1cm in diameter around the yellowish edge); please refer to [the image / diagram] after 30 hours. Figure 3c As shown, in Figure 3b Based on this, a 0.2cm increase appeared in region S3. 2 The yellowing of the macular region; after 36 to 48 hours, the yellowing of the back hair was similar to that of the macular region. Figure 3c They are all quite similar, with a ring of tiny yellow dots about 0.1 cm in diameter around the yellowish edges. Both regions S4 and S5 contain one yellow spot, approximately 0.25 cm in size. 2 There is a yellow spot in region S3, with an area of ​​approximately 0.2 cm. 2 .

[0091] Figures 4a to 4h This diagram illustrates the yellowing of the gold-back surface of a wafer under a 10% hydrochloric acid environment. For wafers sealed together with a measuring cup containing 10% hydrochloric acid, please refer to the diagram after 6 hours. Figure 4a As shown, the wafer edges are yellowish; please refer to the image after 12 hours. Figure 4b As shown, the yellowing area at the wafer edge has increased, with the S5 region showing an area of ​​0.25 cm². 2 Two yellow spots; after 18 hours, please refer to... Figure 4c As shown, the yellowing area at the wafer edge has increased, with regions S3, S4, and S5 together covering an area of ​​0.25 cm².2 Six yellow spots; please refer to [the relevant information] after 24 hours. Figure 4d As shown, the yellowing areas at the wafer edges have increased, and the number of yellow spots has also increased; please refer to [the image / data] after 30 hours. Figure 4e As shown, the edges are yellowish, and within this yellowish area, there is a ring of tiny yellow dots approximately 0.1 cm in diameter. The entire wafer contains about 30 such dots, each 0.25 cm² in size. 2 The yellow spots are mainly concentrated in the S2, S3, and S5 regions, as well as near the wafer notch. Larger yellow spots, measuring 7cm in length and 5cm in width, appear, covering the S3, S4, and S5 regions. Please refer to [the relevant documentation] after 36 hours. Figure 4f As shown, the larger macula increased in size to 7cm in length and 6cm in width; after 42 hours, please refer to... Figure 4g As shown, the edges are yellowish, and within this yellowish area, there is a ring of tiny yellow dots approximately 0.1 cm in diameter. The entire wafer contains about 40 such dots, each with an area of ​​0.25 cm². 2 The yellow spots are mainly concentrated within 10cm of the wafer diameter and show a spreading trend. Only a 1.5cm diameter area about 3cm from the wafer edge remains unaffected. Please refer to [the website / reference] after 48 hours. Figure 4h As shown, the edges are yellowish, and within this yellowish area, there is a ring of tiny yellow dots approximately 0.1 cm in diameter. The entire wafer contains about 40 such dots, each 0.5 cm² in size. 2 ~1cm 2 The yellow spots are mainly concentrated in the area within 10cm of the wafer diameter, and there is a tendency for them to spread. Only a 1cm diameter area around 3cm from the edge of the wafer is not yellowed.

[0092] The above reverse degradation experiment revealed that the factors causing the yellowing of the golden hair on the back include Cl in the environment. - Ions, Cl - The higher the concentration of Cl, the more severe the yellowing of the wafer, and the higher the concentration of Cl. - The longer the wafer is placed in an ion-rich environment, the more severe the yellowing phenomenon becomes.

[0093] Then the microenvironment deteriorates due to NO3 - That is, to provide high concentrations of NO3 - Environment. For example, place 25% nitric acid (HNO3) in a measuring cup and place the wafer and measuring cup in the same sealed POD. At the same time, place 35% nitric acid (HNO3) in a measuring cup and place the wafer and measuring cup in the same sealed POD. In addition, wafers placed separately in sealed PODs are also provided. Then, observe the yellowing of the back gold every 6 hours.

[0094] Observation of the yellowing of the back wafers revealed that wafers placed alone in a sealed POD did not yellow, while wafers placed at the same time as the measuring cups yellowed over time. Figures 5a to 5d This diagram illustrates the yellowing of the gold-back surface of a wafer under 25% nitric acid conditions. For wafers sealed together with a measuring cup containing 25% nitric acid, please refer to the diagram after 6 hours. Figure 5a As shown, a yellowish area extends from the outer edge of the wafer to the inner edge, approximately 0.2 cm away. This area has a radial width of about 2-3 cm and contains approximately 16 yellow spots scattered across 5 regions. The size of the yellow spots in regions S1 to S4 is approximately 0.3-0.5 cm, while the size of the yellow spots in region S5 is approximately 1 cm. Please refer to [the image / data] after 12 hours. Figure 5b As shown, with Figure 5a In comparison, the size of the yellow spots increased, with the spots in regions S1 to S4 increasing to approximately 0.8cm–1.2cm, and the spots in region S5 increasing to approximately 1.5cm. Furthermore, the back gold color was darker overall about 1–2cm from the edge. Please refer to the following after 18 hours. Figure 5c As shown, the entire wafer is yellowed, with severe yellowing extending inwards from approximately 1 cm from the wafer edge. There are about 18 yellow spots, each about 1 cm in size. Please refer to the results after 24 to 48 hours. Figure 5d As shown, the entire wafer is yellowed, with severe yellowing extending inward from about 1 cm from the edge of the wafer. There are approximately 20 yellow spots, each about 1 cm in size.

[0095] For the wafer sealed with a measuring cup containing 35% nitric acid, after 6 hours, the entire area extending inward from about 0.2 cm from the wafer edge was slightly yellow, and a ring area about 0.5 cm to 1 cm from the wafer edge was yellow. After 12 hours, approximately 35 yellow spots were distributed in five areas, with the size of the yellow spots being approximately 0.5 cm to 1 cm. After 18 hours, the entire wafer was yellow, with severe yellowing in the area extending inward from about 2 cm from the wafer edge, with about 7 to 8 yellow spots, each about 2 cm. After 24 hours, the entire wafer was yellow, with severe yellowing in the area extending inward from about 2 cm from the wafer edge, with about 7 to 8 yellow spots, each about 2 cm, and small yellow spots concentrated in the S3 region, each about 1 mm to 2 mm. After 30 hours, the entire wafer surface turned yellow, with severe yellowing extending inwards from about 2 cm from the wafer edge. There were approximately 10 yellow spots, each about 2 cm in size. Smaller yellow spots were concentrated in the S3 region, each about 1 mm to 2 mm in size. After 36 hours, the entire wafer surface turned yellow, with severe yellowing extending inwards from about 2 cm from the wafer edge. There were approximately 12 yellow spots, each about 2 cm in size. Smaller yellow spots were concentrated in the S3 region, each about 1 mm to 2 mm in size. After 18 hours, the entire wafer surface turned yellow, with severe yellowing around the edge and approximately 12 large yellow spots.

[0096] The above-mentioned reverse degradation experiment revealed that the factors causing the yellowing of the back hair include NO3 in the environment. - Ions, NO3 - The higher the concentration of NO3, the more severe the yellowing of the wafer, and the higher the concentration of NO3. - The longer the wafer is placed in an ion-rich environment, the more severe the yellowing phenomenon becomes.

[0097] Then the microenvironment deteriorates due to SO4. 2- That is, to provide high concentrations of SO4 2- Environment. For example, placing a high concentration of sulfuric acid (H2SO4) in a measuring cup, placing the wafer and the measuring cup in the same sealed POD, with some wafers close to the measuring cup and some wafers far away from the measuring cup.

[0098] Figures 6a to 6d This diagram illustrates the yellowing process of the gold-backed surface of a wafer under a high-concentration sulfuric acid environment. Please refer to the diagram after the wafer has been left to stand for 6 hours. Figure 6a As shown, the wafer closest to the measuring cup appears yellowish within approximately 2cm of the wafer edge, while the area beyond 2cm appears whitish. Please refer to [the image / reference]. Figure 6b As shown, on the wafer farther from the measuring cup, the area within approximately 6cm of the center diameter is whitish, a ring of white is about 2cm from the wafer edge, and the remaining area is yellowish. There are four white marks, approximately 1cm in diameter, in area S2 above the wafer notch (facing down in the image). Please refer to [the image / data] after 12 hours. Figure 6c As shown, the wafer closest to the measuring cup exhibits yellowing within approximately 2 cm of the wafer edge. Irregular yellowing occurs at the boundary between regions S1 and S2, and fingerprint-like yellowing is observed at the edges of regions S2, S3, and S4. Please refer to [reference needed]. Figure 6d As shown, the wafers farther from the measuring cup have a white area within about 6cm of the wafer center, a white area around about 2cm from the wafer edge, and other areas are yellow. There are three white marks in area S2 above the wafer notch, each about 1cm in diameter, and the yellow area in area S3 increases.

[0099] The above-mentioned reverse degradation experiment revealed that the factors causing the yellowing of the gold hair include SO4 in the environment. 2- Ions, SO4 2- The higher the concentration of SO4, the more severe the yellowing of the wafer, and the more pronounced the yellowing phenomenon. 2- The longer the wafer is placed in an ion-rich environment, the more severe the yellowing phenomenon becomes.

[0100] At the same time, it worsened F - With NH4 + Despite the microenvironment, no yellowing occurred on the wafers.

[0101] It should be noted that the wafers used in the above experiments were all dummy wafers, i.e. test wafers, on which metals were deposited to conduct experiments in different environments.

[0102] In step S4, the microenvironment that causes the back gold anomaly is determined.

[0103] Based on the above analysis, especially the reverse deterioration experiment in step S3, it was determined that the main factor causing the yellowing of the back gold is anions in the environment, primarily Cl-. - NO3 - With SO4 2- It is unrelated to environmental VOCs and cations. Furthermore, the severity of yellowing increases with the increase of anion concentration in the environment and the accumulation of time.

[0104] It should be noted that the back gold of a wafer exhibits a yellowing phenomenon under high-concentration microenvironment, while Figures 3a to 3c ,4a to Figure 4h , Figures 5a to 5d as well as Figures 6a to 6d In the middle, as time went on, when the yellowing became more severe, it was marked in red, meaning that the color in the attached picture does not represent the actual color of the gold back.

[0105] This invention verifies the back gold coating of wafers under different regional environments. By controlling a single environmental variable and combining preliminary judgment with data collection, the environmental factors causing back gold coating anomalies are identified. Each microenvironment among the environmental factors is subjected to deterioration experiments to verify the microenvironment causing the back gold coating anomaly. This can quickly pinpoint the factors causing the back gold coating of wafers to turn yellow, reduce trial and error costs, and prevent further expansion of online losses.

[0106] The experimental method described in this invention has determined that the factor causing the yellowing of the back hair is Cl in the environment. - NO3 - With SO4 2- Using anion exchange, this verification method can quickly pinpoint back-gold anomalies in products caused by environmental anomalies, reducing trial-and-error costs and preventing further spread of online losses.

[0107] Furthermore, by installing chemical filters in the BGBM area, the stability of the environment can be controlled. According to experimental results, it is only necessary to install anion chemical filters in the BGBM and other gold-related areas to control and solve the problem of gold-backing abnormalities. There is no need to install a full range of chemical filters, which saves one-third of the cost and avoids additional cost expenditures.

[0108] In summary, the method for analyzing the causes of wafer back-gold anomalies provided by this invention first verifies whether there is an anomaly in the wafer back-gold under different regional environments, identifies the abnormal regional environment causing the anomaly, and preliminarily identifies the environmental factors causing the anomaly in the abnormal regional environment; then, it collects data on the environmental factors causing the anomaly in different regional environments to further identify the environmental factors causing the anomaly; next, it deteriorates each microenvironment among the environmental factors causing the anomaly to verify whether the back-gold is abnormal; and finally, it identifies the microenvironment causing the anomaly. This invention verifies the wafer back-gold under different regional environments, determines the environmental factors causing the anomaly by controlling a single environmental variable and combining preliminary judgment and data collection, and conducts deterioration experiments on each microenvironment among the environmental factors to verify the microenvironment causing the anomaly. This can quickly pinpoint the factors causing the wafer back-gold anomaly, reduce trial-and-error costs, and prevent further expansion of online losses.

[0109] Accordingly, the present invention also provides a method for improving wafer back gold defects. The method for analyzing the causes of wafer back gold defects as described above is used to analyze and determine the microenvironment that causes the back gold defects. Then, a filtration device is used to filter the microenvironment that causes the back gold defects, thereby improving the wafer back gold defects.

[0110] The method for improving wafer back-gold defects provided in this embodiment of the invention includes the following steps:

[0111] Step S1: Verify the presence of anomalies in the back gold coating of the wafer under different regional environments, identify the abnormal regional environments causing the anomalies, and preliminarily determine the environmental factors causing the anomalies in the abnormal regional environments. In this embodiment of the invention, wafers with formed back gold coatings are placed in different regional environments to verify which regional environment causes the anomalies. The regional environments where the back gold coatings are abnormal are identified as abnormal regional environments, and then the environmental factors causing the anomalies in the abnormal regional environments are preliminarily determined. For example, the abnormal regional environments preliminarily determined to cause the back gold coating anomalies are the BGBM nitrogen cabinet and the BGBM region, and the environmental factors causing the back gold coating anomalies in the abnormal regional environments are anions, especially Cl. - .

[0112] In step S2: Data on environmental factors causing the gold-back anomaly are collected in different regional environments to further determine the environmental factors causing the gold-back anomaly. In this embodiment, data on anions in different regional environments are collected to further determine the environmental factors causing the gold-back anomaly, that is, to further determine whether the environmental factors causing the gold-back anomaly are anions.

[0113] In step S3, each microenvironment among the environmental factors that cause the back gold anomaly is deteriorated to verify whether the back gold is abnormal. In this embodiment, the microenvironment among the environmental factors includes Cl -NO3 - SO4 2- F - or NH4 + The microenvironment was deteriorated to determine whether it would cause the wafer to yellow.

[0114] In step S4, the microenvironment causing the abnormal gold color on the back is identified. In this embodiment, based on the above analysis, especially the reverse degradation experiment in step S3, it is determined that the main factor causing the gold color on the back is anions in the environment, primarily Cl-. - NO3 - With SO4 2- It is unrelated to environmental VOCs and cations, and the severity of yellowing will increase with the increase of anion concentration in the environment and the accumulation of time.

[0115] In step S5, a filtration device is used to filter the microenvironment causing back-gold abnormalities. In this embodiment, the main factor causing back-gold yellowing is anion exchange in the environment. The filtration device includes anion exchange chemical filters, which filter out anions in the environment to improve the back-gold abnormality. Furthermore, according to experimental results, only anion exchange chemical filters need to be installed in the back-gold related areas such as the BGBM area to control and resolve the back-gold abnormality problem, eliminating the need for a full range of chemical filters and saving costs. Simultaneously, by installing chemical filters in the BGBM area, the stability of the environment can be controlled, thereby improving the wafer back-gold abnormality problem.

[0116] In summary, the method for improving wafer back-gold defects provided by this invention, after identifying the microenvironment causing the defect, only a filtration device is needed to filter that microenvironment; there is no need to add filtration devices to all areas, thus saving costs. Simultaneously, adding a filtration device maintains environmental stability, thereby improving the wafer back-gold defect problem and enhancing device performance.

[0117] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for analyzing the causes of back-side gold defects in wafers, characterized in that, Includes the following steps: The presence of abnormalities in the back gold of the wafer was verified under different regional environments. The abnormal regional environments that caused the abnormalities were identified, and the environmental factors that caused the abnormalities in the abnormal regional environments were preliminarily determined. Data on environmental factors that cause the anomaly of gold backing were collected in different regions to further identify the environmental factors that cause the anomaly of gold backing. Each microenvironment among the environmental factors that exacerbate the anomaly of the gold backing is used to verify whether the gold backing is abnormal; and Identify the microenvironment that causes the abnormal gold backing.

2. The method for analyzing the causes of wafer back-side gold anomalies according to claim 1, characterized in that, The methods for preliminarily determining the environmental factors in the abnormal area that lead to the gold-back anomaly include: The environment of the abnormal area was sampled, and the content of each environmental factor was analyzed. Based on the content of the aforementioned environmental factors, the environmental factors leading to the abnormal gold backing were preliminarily determined.

3. The method for analyzing the causes of wafer back-side gold anomalies according to claim 1, characterized in that, In addition to collecting data on environmental factors that cause back-gold anomalies in different regions, the study also includes collecting data on the regions on the wafer where back-gold anomalies occur to determine whether the anomalies are related to the region.

4. The method for analyzing the causes of anomalies in round-backed gold jewelry according to claim 3, characterized in that, During the process of collecting areas with back gold abnormalities on wafers, the wafers are placed in environments that are more affected by environmental factors and environments that are less affected by environmental factors.

5. The method for analyzing the causes of wafer back-side gold anomalies according to claim 4, characterized in that, Areas more affected by environmental factors include the outbound inspection area, the testing plant area, the BGBM area, or the BGBM nitrogen cabinet. Areas less affected by environmental factors include the yellow light area.

6. The method for analyzing the causes of wafer back-side gold anomalies according to claim 3, characterized in that, The environmental area includes the outgoing inspection area, the testing plant area, the BGBM area, the BGBM nitrogen cabinet, and the yellow light area, which is used as a comparison to determine whether there are any abnormalities in the environmental factors.

7. The method for analyzing the causes of wafer back-side gold anomalies according to claim 1, characterized in that, The environmental factors include VOCs, benzene compounds, halogenated organic compounds, anions, and cations.

8. The method for analyzing the causes of wafer back-side gold anomalies according to claim 7, characterized in that, The microenvironment among the environmental factors includes Cl- and NO3-. - SO4 2- F- or NH4 + .

9. The method for analyzing the causes of wafer back-side gold anomalies according to any one of claims 1 to 8, characterized in that, The aforementioned back gold anomaly includes yellowing of the back gold.

10. A method for improving wafer back-gold anomalies, characterized in that, Includes the following steps: The presence of abnormalities in the back gold of the wafer was verified under different regional environments. The abnormal regional environments that caused the abnormalities were identified, and the environmental factors that caused the abnormalities in the abnormal regional environments were preliminarily determined. Data on environmental factors that cause the anomaly of gold backing were collected in different regions to further identify the environmental factors that cause the anomaly of gold backing. Each microenvironment among the environmental factors that exacerbate the back gold anomaly is used to verify whether the back gold is abnormal. Identify the microenvironment that caused the anomaly on the gold back; as well as A filtration device is used to filter the microenvironment that causes abnormal gold backing.

11. The method for improving wafer back-gold anomalies according to claim 10, characterized in that, The microenvironment that leads to abnormal back-gold content in wafers includes anions, such as Cl-, NO3-, or SO42-. 2- .

12. The method for improving wafer back-gold anomalies according to claim 11, characterized in that, An anion exchange filter is used to filter the microenvironment.

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