Image sensor processing method and analysis method

Abstract

The invention discloses an image sensor processing method and analysis method, in the image sensor processing method, an image sensor comprises an optical filter, a DAF film, a bare chip and a packaging substrate which are arranged in sequence, and the method comprises the following steps: forming a corrosion groove in a packaging material between the optical filter and a bonding wire of an image sensor sample; acid liquor is added into the corrosion tank, so that the DAF film is exposed; the corroded sample is baked, and a baked sample is obtained; heating the position of the optical filter in the baked sample until the DAF film in contact with the optical filter cracks, and separating out the optical filter to obtain the sample without the optical filter; and removing the DAF film on the surface of the bare chip in the sample from which the optical filter is removed to obtain an exposed component on the surface of the bare chip. According to the image sensor processing method provided by the invention, the surface of the bare chip can be exposed, and meanwhile, the bare chip is not damaged, so that subsequent analysis tests such as failure analysis and hotspot analysis on the bare chip are facilitated.

Description

Technical Field

[0001] The present invention relates to the field of chip testing technology, and in particular to an image sensor processing method and an analysis method. Background Art

[0002] Image sensors, as a key electronic device that converts optical images into electrical signals, are widely used in digital cameras, smartphones, security monitoring, medical imaging, and autonomous driving. As a core component of modern imaging systems, their performance directly determines key indicators such as image clarity, color reproduction, and dynamic range. With the rapid development of science and technology, the demand for image sensor chips in devices such as smart cars, robots, and drones is increasing, and the frequency of use has increased significantly, which has also led to the frequent failure of various image sensors. When performing image sensor chip failure analysis, the filters attached to the package surface often hinder hotspot analysis and visual inspection, which poses a significant challenge to failure analysis. However, at present, laboratories have not yet established a complete method for removing filters from the image sensor package surface without damaging the chip.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The object of the present invention is to provide an image sensor processing method and an analysis method to reduce bare chip damage caused during the process of peeling off the filter and DAF film in the image sensor.

[0005] The present invention is achieved in that: In a first aspect, the present invention provides an image sensor processing method, wherein the image sensor includes a filter, a DAF film, a bare chip, and a packaging substrate arranged in sequence, the method comprising: Grooving: creating an etching groove on the packaging material between the filter and the bonding wire of the image sensor sample; Acid corrosion, adding acid solution into the corrosion tank to corrode and clean the packaging material to expose the DAF film and obtain a corroded sample; Baking, baking the corroded sample to obtain a baked sample; Filter stripping: heating the position of the filter in the baked sample until the DAF film in contact with the filter cracks, separating the filter to obtain a sample without the filter; The DAF film is removed, and the DAF film on the surface of the bare chip in the sample after the filter is removed is removed to obtain a component with the bare chip surface exposed.

[0006] In an optional embodiment, the baking temperature is 115° C.-125° C., and the baking time is 3.5 h-4.5 h.

[0007] In an optional embodiment, the distance between the etching groove and the filter is greater than a preset value; And / or, before the grooving step, X-ray is used to observe the distance between the filter and the bonding wire in the image sensor sample and the thickness of the packaging material to avoid laser damage to the bare chip during grooving.

[0008] In an optional embodiment, the etching groove is opened on at least one side of the filter.

[0009] In an optional embodiment, the acid solution includes at least one of fuming nitric acid and concentrated sulfuric acid; And / or, the etching step is repeated twice or more, the etching temperature is 95° C.-105° C., and the etching time each time is 4 s-6 s.

[0010] In an optional embodiment, the lotion used in the cleaning step is selected from at least one of acetone and alcohol; and / or, each etching step corresponds to a cleaning step; And / or, the corroded sample is dried before baking.

[0011] In an optional embodiment, the heating temperature of the heating step is 300° C.-350° C.; And / or, in the heating step, a heat source is used to uniformly heat each position of the filter.

[0012] In an optional embodiment, the step of removing the DAF film includes: immersing the sample after removing the filter in a solvent, and then peeling off the DAF film on the surface of the bare chip to obtain a component with the bare chip surface exposed.

[0013] In an optional embodiment, the solvent is selected from acetone; And / or, the soaking time is 25 min-35 min.

[0014] In a second aspect, the present invention provides a die analysis method, comprising: The components exposed on the surface of the die obtained in the image sensor processing method described in any one of the aforementioned embodiments are analyzed.

[0015] In an optional embodiment, the image sensor includes, from top to bottom, a filter, a DAF film, a bare die A, a DAF film, a bare die B, and a packaging substrate; the surface of the bare die A is exposed using the image sensor processing method, and then the bare die A is analyzed. After the analysis of the bare die A is completed, the DAF films on the surfaces of the bare die A and the bare die B are then peeled off to expose the surface of the bare die B, and then the bare die B is analyzed.

[0016] The present invention has the following beneficial effects: The image sensor processing method in this application can expose the surface of the die without causing damage to the die, so that subsequent analysis and testing such as failure analysis and hot spot analysis can be performed on the die. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a flowchart of the image sensor processing method in this application; Figure 2 This is an appearance diagram of the image sensor sample in Example 1; Figure 3 This is a schematic structural diagram of an image sensor sample from one viewing angle in Example 1; Figure 4 Schematic diagram of the location of the etching groove of the image sensor sample in Example 1; Figure 5 This is an appearance diagram of the component with the bare die surface exposed obtained in Example 1; Figure 6 Schematic diagram of the location of the etching groove of the image sensor sample in Example 3.

[0019] Diagram: 1-filter; 2-DAF film; 3-Die A; 5-Die B; 6-package substrate; 7-wire bonding; 8-etching groove. DETAILED DESCRIPTION

[0020] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0021] In order to avoid the influence of the filter in the image sensor on the image sensor die, some studies have proposed directly dripping acid on the image sensor to corrode the outer package to obtain the inner die. However, since the filter on the surface of the image sensor die is usually made of DAF (Die Attach Film) or colloid and is tightly attached to the surface of the inner die, the acid corrosion process takes a long time, and the DAF film covered by the filter is difficult to peel off, which increases the risk of damaging the die when peeling off the filter and DAF film. Therefore, in some situations where the die needs to be intact and only the top filter and DAF film need to be removed for analysis and inspection, the above-mentioned method of directly dripping acid on the image sensor to corrode the outer package to obtain the inner die is obviously no longer applicable. In order to improve the efficiency and accuracy of image sensor analysis and reduce the damage to the die caused by the process of peeling off the filter and DAF film on the image sensor die, the embodiments of the present invention provide the following methods: A method for processing an image sensor, wherein the image sensor comprises a filter, a DAF film, a bare chip and a packaging substrate arranged in sequence, such as Figure 1 As shown, the method includes: Grooving: creating an etching groove on the packaging material between the filter and the bonding wire of the image sensor sample; Acid corrosion, adding acid solution into the corrosion tank to corrode and clean the packaging material to expose the DAF film and obtain a corroded sample; Baking, baking the corroded sample to obtain a baked sample; Filter stripping: heating the position of the filter in the baked sample until the DAF film in contact with the filter cracks, separating the filter to obtain a sample without the filter; The DAF film is removed, and the DAF film on the surface of the bare chip in the sample after the filter is removed to obtain a component with the bare chip surface exposed.

[0022] The image sensor processing method in this application is applicable to removing the filter and DAF film on the surface of the die. In some embodiments, the image sensor may include more than two dies (hereinafter referred to as Die). In this case, the method of this application can be used to first remove the DAF film and filter on the top die, so that the surface of the top die close to the filter is exposed for subsequent analysis; for other dies far from the filter, if analysis is required, other methods can be used. Therefore, unless otherwise specified, the die in this application refers to the die bonded to the filter through the DAF film.

[0023] In some embodiments, the image sensor has two dies, for example, Die A and Die B. The image sensor includes, from top to bottom, a filter, a DAF film, Die A (i.e., bare die A), a DAF film, Die B (i.e., bare die B), and a packaging substrate, and packaging material is used between the edge of the filter and the packaging substrate. After the image sensor is processed by the image sensor processing method of the present application, the resulting component with exposed die surface includes, from top to bottom, Die A, a DAF film, Die B, and a packaging substrate, wherein the upper surface of Die A is exposed to facilitate subsequent analysis and testing such as failure analysis and hot spot analysis of Die A.

[0024] In other embodiments, the image sensor has only one die, and the image sensor includes a filter, a DAF film, a die and a packaging substrate from top to bottom, and the edge of the filter and the packaging substrate are encapsulated with packaging material; after the image sensor is processed by the image sensor processing method in this application, the components exposed on the surface of the bare die include the die and the packaging substrate, and the die can be subsequently subjected to analysis and testing such as failure analysis and hotspot analysis.

[0025] The image sensor processing method of the present application can expose the surface of the die without causing damage to the die.

[0026] In an optional embodiment, the baking temperature is 115° C.-125° C., and the baking time is 3.5 h-4.5 h.

[0027] The main purpose of baking in this application is to remove the residual lotion and water vapor in the sample after corrosion. In an optional embodiment, the baking temperature can be 115°C-125°C, specifically 115°C, 117°C, 119°C, 121°C, 123°C, 125°C or any value between 115°C-125°C. Properly increasing the temperature is conducive to the rapid evaporation of lotion and water vapor, etc., so as to improve efficiency, but too high a temperature may cause damage to the die due to excessive gasification of lotion and water vapor. In an optional embodiment, the baking time is 3.5h-4.5h, specifically 3.5h, 3.7h, 3.9h, 4.1h, 4.3h, 4.5h or any value between 3.5h-4.5h. Compared with the conventional unsealing of the die that does not involve the filter, the present application requires a longer baking time to reduce the damage to the die in the subsequent filter stripping step.

[0028] In an optional embodiment, the distance between the etching groove and the filter should not be too small to avoid damage to the underlying die during the grooving process. The distance between the etching groove and the filter can be greater than a preset value, for example, 50 μm. In some embodiments, the grooving can be performed using laser irradiation.

[0029] In an optional embodiment, before the grooving step, the distances between the filter and the wire bonding and the thickness of the encapsulation material in the image sensor sample are observed by X-ray, and the die is avoided from being damaged by laser during grooving.

[0030] By observing the distances between the filter and the wire bonding and the thickness of the encapsulation material in the image sensor sample by X-ray, the grooving depth of the etching groove can be preliminarily estimated, and the die side can be avoided from being damaged in the subsequent steps, which affects the subsequent analysis of the die.

[0031] In an optional embodiment, the etching groove is formed on at least one side of the filter. In some embodiments, the etching groove can be arranged on one side of the die, or on any two sides, any three sides or four sides of the filter. The number of the etching grooves can be one, two or even more. Specifically, in some embodiments, the etching groove can be arranged along one side of the filter; in some other embodiments, a "冂"-shaped etching groove can be arranged along three sides of the filter; in some other embodiments, a linear etching groove can be arranged around the four sides of the filter. However, it should be noted that regardless of the shape and number of the etching grooves, a preset distance needs to be maintained between the etching groove and the filter to avoid damage to the die by laser during grooving, and the preset distance can be determined according to the distances between the filter and the wire bonding and the thickness of the encapsulation material observed by X-ray in the image sensor sample.

[0032] In an optional embodiment, the acid solution includes at least one of fuming nitric acid and concentrated sulfuric acid. Specifically, the acid solution can be fuming nitric acid, or concentrated sulfuric acid, or a mixed acid of fuming nitric acid and concentrated sulfuric acid, as long as it can etch the encapsulation material.

[0033] In an optional embodiment, the etching step is repeated more than twice, the etching temperature is 95°C - 105°C, and the etching time for each time is 4s - 6s.

[0034] Specifically, the corrosion temperature can be 95°C, 97°C, 99°C, 101°C, 103°C, 105°C or any value between 95°C and 105°C. Properly increasing the corrosion temperature can accelerate the corrosion rate and improve efficiency. However, if the corrosion temperature is too high, the corrosion rate is too fast, which may cause excessive corrosion and damage to the bare chip. The corrosion time can be 4s, 4.5s, 5s, 5.5s, 6s or any value between 4s and 6s. In order to avoid excessive corrosion, multiple short-term corrosions can be performed. After each corrosion is completed, observe whether the DAF film is exposed. If the single corrosion time is too long, direct corrosion to the bare chip may occur, causing damage to the bare chip. If the single corrosion time is too short, the corrosion reaction will be frequently stopped, resulting in reduced efficiency. In an optional embodiment, the detergent used in the cleaning step is selected from at least one of acetone and alcohol. Specifically, the detergent can be acetone, alcohol, or a mixture of acetone and alcohol. The detergent is used to wash away the acid solution in the acid corrosion process to stop the corrosion reaction.

[0035] In an optional embodiment, each etching step corresponds to a cleaning step to stop the etching reaction. Therefore, if the single etching time is too short, the cleaning step will be increased, which will cause waste of detergent, increase cost and reduce efficiency.

[0036] In an optional embodiment, the corroded sample is dried before baking. Drying first removes most of the detergent and moisture in the corroded sample, which can reduce the change in the internal pressure of the corroded sample caused by the vaporization of the detergent and moisture during baking, and avoid damage to the bare chip caused by excessive internal pressure of the corroded sample during baking.

[0037] In an optional embodiment, the heating temperature of the heating step is 300°C-350°C. Specifically, the heating temperature can be 300°C, 310°C, 320°C, 330°C, 340°C, 350°C or any value between 300°C and 350°C. The purpose of the heating step is to accelerate the deterioration of the DAF film and remove the stickiness of the DAF film so that the filter can be peeled off. Therefore, appropriately increasing the heating temperature is beneficial to improving efficiency. However, if the heating temperature is too high, it may cause damage to the bare chip. Therefore, the heating temperature needs to be reasonably selected.

[0038] In an optional embodiment, the heating step utilizes a heat source to uniformly heat all locations on the filter, causing cracks to form uniformly across the DAF film. If, during the filter peeling process, the DAF film remains sticky despite cracks in some areas, peeling the filter becomes more difficult and significantly increases the risk of damaging the die. In some embodiments, the heat source is applied around the edge of the filter, with the radius of the circle gradually decreasing until the filter is evenly heated and cracks form relatively uniformly across the DAF film. Heating is then stopped.

[0039] In some embodiments, when cracks occur in the DAF film, a scalpel or a structure similar to a scalpel can be used to gently lift up from the bonding point between the DAF and the filter to remove the filter.

[0040] In an optional embodiment, the step of removing the DAF film includes: immersing the sample after removing the filter in a solvent, and then peeling off the DAF film on the surface of the bare chip to obtain a component with the bare chip surface exposed.

[0041] During the soaking process, the DAF film dissolves and swells, weakening its bond with the die. The remaining DAF film can be peeled off the die surface with minimal force. In some implementations, a cotton swab or a soft, similar object can be used to gently wipe the die surface to avoid scratches or cracks on the die surface caused by excessive force or a wiping material that is too hard.

[0042] In an optional embodiment, the solvent is selected from acetone to promote the dissolution or swelling of the DAF membrane. In some embodiments, the solvent can also be appropriately heated to improve efficiency. However, it should be noted that acetone itself has a strong volatility. Therefore, when soaking, it is recommended to be carried out in a closed container or fume hood to avoid damage to the operator.

[0043] In an optional embodiment, the immersion time is 25min-35min, specifically it can be 25min-35min or any value between 25min-35min. Appropriately extending the immersion time is beneficial to weakening the bonding force between the DAF film and the bare chip. If the immersion continues after the bonding force between the DAF film and the bare chip is weakened, it will only result in a decrease in efficiency.

[0044] An embodiment of the present invention further provides an image sensor analysis method, comprising: The components exposed on the surface of the die obtained in the image sensor processing method described in any one of the aforementioned embodiments are analyzed.

[0045] The analysis includes failure analysis and hotspot analysis. Failure analysis aims to determine the physical and electrical causes of die failure, while hotspot analysis is specifically used to locate local high-temperature areas within the die caused by defects (such as short circuits and leakage). The combination of the two can more effectively evaluate the causes of image sensor failure.

[0046] In an optional embodiment, the image sensor includes, from top to bottom, a filter, a DAF film, a bare die A, a DAF film, a bare die B, and a packaging substrate; the surface of the bare die A is exposed using the image sensor processing method, and then the bare die A is analyzed. After the analysis of the bare die A is completed, the DAF films on the surfaces of the bare die A and the bare die B are then peeled off to expose the surface of the bare die B, and then the bare die B is analyzed.

[0047] When the image sensor includes more than two dies, the analysis result of die A can be used to determine whether to analyze die B. In some cases, to obtain more reliable analysis results, die B can be analyzed regardless of the analysis result of die A.

[0048] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0049] Example 1 This embodiment provides an image sensor processing method, which specifically includes the following steps: Step 1: Sample observation and measurement; First, X-ray was used to observe the internal structure of the image sensor sample, and the distance from the filter to the bonding wire and the thickness of the packaging material were measured. Figure 2 As shown, the structure of the image sensor sample is as follows Figure 3 As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0050] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0051] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 50 μm.

[0052] Step 3: acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 100° C. and heated for 5 seconds, and then rinsed with acetone.

[0053] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0054] Step 4: Bake; The corroded samples were dried and then baked in an oven at 120°C for 4 hours to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0055] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 320°C. When the DAF film 2 produces fine cracks due to the high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0056] Step 6: Soak the sample after removing the filter 1 in acetone for half an hour, then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the bare surface of Die A. Figure 5 shown.

[0057] Step 7. Use an optical microscope to inspect the surface of Die A for abnormalities such as damage, scratches, and burns. If no abnormalities are found, perform subsequent failure analysis and hotspot analysis on Die A 3.

[0058] Example 2 This embodiment provides an image sensor processing method, which specifically includes the following steps: Step 1: Sample observation and measurement; First, X-rays were used to observe the internal structure of the image sensor sample, measuring the distance from the filter 1 to the bonding wire 7, as well as the thickness of the packaging material. From top to bottom, the image sensor sample consists of the filter 1, DAF film 2, die, and packaging substrate 6. The edge of the filter 1 is encapsulated with packaging material, and the die is connected to the packaging substrate 6 via bonding wires 7.

[0059] Step 2: Slotting; Based on the results of X-ray observation and measurement in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying die.

[0060] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 60 μm.

[0061] Step 3: acid corrosion; Fuming nitric acid was dropped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 95° C. and heated for 6 seconds, and then rinsed with a mixture of acetone and alcohol in a mass ratio of 1:1.

[0062] The above-mentioned steps of adding mixed acid and rinsing were repeated 9 times to expose the DAF film 2 and obtain a corroded sample; repeating the steps of adding mixed acid and rinsing can ensure that the packaging material will not be over-corroded. When the corrosion causes the DAF layer between the filter 1 and the die to be exposed, the corrosion can be stopped.

[0063] Step 4: Bake; The corroded samples were dried and then baked in an oven at 115°C for 6 hours to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0064] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 300°C. When the DAF film 2 produces fine cracks due to high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0065] Step 6: Soak the sample after removing the filter 1 in acetone for 35 minutes, and then use a cotton swab to wipe off the DAF film 2 on the die surface.

[0066] Step 7. Use an optical microscope to inspect the die surface for abnormalities such as damage, scratches, and burns. If no abnormalities are found, proceed to subsequent failure analysis and hotspot analysis.

[0067] Example 3 This embodiment provides an image sensor processing method, which specifically includes the following steps: Step 1: Sample observation and measurement; First, use X-ray to observe the internal structure of the image sensor sample, measure the distance from the filter 1 to the bonding wire 7 and the thickness of the packaging material. Figure 3 As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0068] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0069] Slot position Figure 6 As shown, the etching groove 8 is arranged in a "mouth" shape around the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 50 μm.

[0070] Step 3: acid corrosion; Concentrated sulfuric acid was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 105° C. and heated for 4 seconds, and then rinsed with alcohol.

[0071] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0072] Step 4: Bake; The corroded samples were dried and then baked in an oven at 125° C. for 3 h to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0073] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 350°C. When the DAF film 2 produces fine cracks due to high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0074] Step 6: Soak the sample after removing the filter 1 in acetone for 25 minutes, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A 3.

[0075] Step 7. Use an optical microscope to inspect the Die A surface for abnormalities such as damage, scratches, and burns. If no abnormalities are found, proceed to subsequent failure analysis and hotspot analysis.

[0076] Example 4 This embodiment provides an image sensor processing method, which differs from the first embodiment mainly in that the baking time is shortened. The method specifically includes the following steps: Step 1: Sample observation and measurement; First, use X-ray to observe the internal structure of the image sensor sample, measure the distance from the filter 1 to the bonding wire 7 and the thickness of the packaging material. Figure 3As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0077] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0078] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 50 μm.

[0079] Step 3: acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 100° C. and heated for 5 seconds, and then rinsed with acetone.

[0080] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0081] Step 4: Bake; The corroded sample was dried and then baked in an oven at 120°C for 2 hours to evaporate the water vapor and detergent introduced during the treatment process, thereby obtaining a baked sample.

[0082] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 320°C. When the DAF film 2 produces fine cracks due to the high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0083] Step 6: Soak the sample after removing the filter 1 in acetone for half an hour, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the Die A surface exposed.

[0084] Step 7. Use an optical microscope to inspect the die surface for abnormalities such as damage, scratches, and burns. If no abnormalities are found, perform subsequent failure analysis and hotspot analysis on Die A 3.

[0085] Example 5 This embodiment provides an image sensor processing method, which differs from the first embodiment mainly in that the baking temperature is too high. The method specifically includes the following steps: Step 1: Sample observation and measurement; First, use X-ray to observe the internal structure of the image sensor sample, measure the distance from the filter 1 to the bonding wire 7 and the thickness of the packaging material. Figure 3 As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0086] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0087] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 50 μm.

[0088] Step 3: acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 100° C. and heated for 5 seconds, and then rinsed with acetone.

[0089] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0090] Step 4: Bake; The corroded samples were dried and then baked in an oven at 180°C for 4 hours to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0091] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 320°C. When the DAF film 2 produces fine cracks due to the high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0092] Step 6: Soak the sample after removing the filter 1 in acetone for half an hour, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the Die A surface exposed.

[0093] Step 7. Use an optical microscope to inspect the surface of Die A for abnormalities such as damage, scratches, and burns. If no abnormalities are found, perform subsequent failure analysis and hotspot analysis on Die A 3.

[0094] Example 6 This embodiment provides an image sensor processing method, which differs from the first embodiment mainly in that the distance between the etching groove 8 and the filter 1 is too small. The method specifically includes the following steps: Step 1: Sample observation and measurement; First, use X-ray to observe the internal structure of the image sensor sample, measure the distance from the filter 1 to the bonding wire 7 and the thickness of the packaging material. Figure 3 As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0095] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0096] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 30 μm.

[0097] Step 3: acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 100° C. and heated for 5 seconds, and then rinsed with acetone.

[0098] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0099] Step 4: Bake; The corroded samples were dried and then baked in an oven at 120°C for 4 hours to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0100] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 320°C. When the DAF film 2 produces fine cracks due to the high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0101] Step 6: Soak the sample after removing the filter 1 in acetone for half an hour, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the Die A surface exposed.

[0102] Step 7. Use an optical microscope to inspect the surface of Die A for abnormalities such as damage, scratches, and burns. If no abnormalities are found, perform subsequent failure analysis and hotspot analysis on Die A 3.

[0103] Example 7 This embodiment provides an image sensor processing method, which differs from the first embodiment mainly in that the temperature in the heating step is too low. The method specifically includes the following steps: Step 1: Sample observation and measurement; First, use X-ray to observe the internal structure of the image sensor sample, measure the distance from the filter 1 to the bonding wire 7 and the thickness of the packaging material. Figure 3 As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0104] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0105] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 50 μm.

[0106] Step 3: acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 100° C. and heated for 5 seconds, and then rinsed with acetone.

[0107] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0108] Step 4: Bake; The corroded samples were dried and then baked in an oven at 120°C for 4 hours to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0109] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 290°C. When the DAF film 2 produces fine cracks due to high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0110] Step 6: Soak the sample after removing the filter 1 in acetone for half an hour, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the Die A surface exposed.

[0111] Step 7. Use an optical microscope to inspect the surface of Die A for abnormalities such as damage, scratches, and burns. If no abnormalities are found, perform subsequent failure analysis and hotspot analysis on Die A 3.

[0112] Comparative Example 1 This comparative example provides an image sensor processing method, which differs from Example 1 mainly in that Steps 1 and 2 are omitted. The method specifically includes the following steps: Step 1: Acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dropped onto the image sensor sample, and the image sensor sample was placed in a heating furnace at 100°C and heated for 5 seconds, and then rinsed with acetone.

[0113] The above-mentioned steps of adding mixed acid and rinsing were repeated 15 times to expose the DAF film 2 and obtain a corroded sample; Step 2: Bake; The corroded samples were dried and then baked in an oven at 120°C for 4 hours to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0114] Step 3: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 320°C. When the DAF film 2 produces fine cracks due to the high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0115] Step 4: Soak the sample after removing the filter 1 in acetone for half an hour, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the bare die surface exposed.

[0116] Step 5: Use an optical microscope to check whether there are any abnormalities on the die surface, such as damage, scratches, burns, etc. If there are no abnormalities, perform subsequent failure analysis and hot spot analysis on Die A 3.

[0117] Comparative Example 2 This comparative example provides an image sensor processing method, which differs from Example 1 mainly in that step 4 is omitted and specifically includes the following steps: Step 1: Sample observation and measurement; First, use X-ray to observe the internal structure of the image sensor sample, measure the distance from the filter 1 to the bonding wire 7 and the thickness of the packaging material. Figure 3 As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0118] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0119] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 50 μm.

[0120] Step 3: acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 100° C. and heated for 5 seconds, and then rinsed with acetone.

[0121] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0122] Step 4: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 320°C. When the DAF film 2 produces fine cracks due to the high temperature, use a scalpel to gently lift up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0123] Step 5: Soak the sample after removing the filter 1 in acetone for half an hour, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the Die A surface exposed.

[0124] Step 6. Use an optical microscope to inspect the surface of Die A for abnormalities such as damage, scratches, and burns. If no abnormalities are found, perform subsequent failure analysis and hotspot analysis on Die A 3.

[0125] Comparative Example 3 This comparative example provides an image sensor processing method, which differs from Example 1 mainly in that the heating temperature in step 5 is too short. The method specifically includes the following steps: Step 1: Sample observation and measurement; First, use X-ray to observe the internal structure of the image sensor sample, measure the distance from the filter 1 to the bonding wire 7 and the thickness of the packaging material. Figure 3 As shown, the image sensor sample includes, from top to bottom, a filter 1, a DAF film 2, a Die A 3, a DAF film 2, a Die B 5, and a packaging substrate 6. The edge of the filter 1 and the packaging substrate 6 are packaged with packaging material, and Die A 3 and Die B 5 are both connected to the packaging substrate 6 through bonding wires 7.

[0126] Step 2: Slotting; Based on the X-ray observation and measurement results in step 1, a laser is used to open an etching groove 8 on the packaging material between the filter 1 and the bonding wire 7 to prevent the laser from passing through the filter 1 and damaging the underlying Die A 3.

[0127] Slot position Figure 4 As shown, the etching groove 8 is arranged on one side of the filter 1, and the shortest distance between the etching groove 8 and the filter 1 is 50 μm.

[0128] Step 3: acid corrosion; A mixture of fuming nitric acid and concentrated sulfuric acid in a mass ratio of 1:1 was dripped into the etching tank 8, and the image sensor sample was placed on a heating furnace at 100° C. and heated for 5 seconds, and then rinsed with acetone.

[0129] The above-mentioned steps of adding the mixed acid and rinsing were repeated 8 times to expose the DAF film 2 and obtain a corroded sample. Repeating the steps of adding the mixed acid and rinsing can ensure that the packaging material will not be excessively corroded. The corrosion can be stopped when the DAF layer between the filter 1 and Die A 3 is exposed.

[0130] Step 4: Bake; The corroded samples were dried and then baked in an oven at 120°C for 4 hours to evaporate and remove the water vapor and detergent introduced during the treatment process, thereby obtaining baked samples.

[0131] Step 5: Remove filter 1; The baked sample is placed in a fixture and placed under a microscope to uniformly heat the position of the filter 1 to 320°C and maintain for 5 minutes. When the DAF film 2 has no fine cracks, use a scalpel to lift it up from the bonding point between the DAF and the filter, remove the filter 1, and obtain the sample without the filter 1.

[0132] Step 6: Soak the sample after removing the filter 1 in acetone for half an hour, and then use a cotton swab to wipe off the DAF film 2 on the surface of Die A3 to obtain a component with the Die A surface exposed.

[0133] Step 7. Use an optical microscope to inspect the surface of Die A for abnormalities such as damage, scratches, and burns. If no abnormalities are found, perform subsequent failure analysis and hotspot analysis on Die A 3.

[0134] The qualified status of the components with exposed Die A or Die surface prepared in the above-mentioned embodiments and comparative examples is shown in Table 1.

[0135] Table 1

[0136] Note: In each embodiment or comparative example, 10 image sensors were processed to obtain 10 component samples with exposed die surfaces. The qualified rate refers to the percentage of qualified samples among the 10 samples to the total number of samples. Qualified means that the component with the filter removed and the bare die surface exposed can be used for subsequent hot spot testing.

[0137] As can be seen from Table 1, in Examples 1-3, the filter can be completely removed, and the bare die samples (DieA or Die B) are not damaged in any way. All the obtained bare die samples can be subjected to subsequent hotspot testing. In Examples 4-7, individual parameters such as baking time, baking temperature, the distance between the etching groove 8 and the filter 1, and the temperature of the heating step are not set reasonably. Although qualified bare die samples can be obtained for subsequent testing, the pass rate is reduced. In contrast, all the bare die samples obtained in Comparative Examples 1-3 are damaged and cannot be subjected to hotspot testing, indicating that the grooving, water vapor baking, and heating steps are important for obtaining qualified bare die samples.

[0138] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for processing an image sensor, wherein the image sensor comprises a filter, a DAF film, a bare chip, and a packaging substrate arranged in sequence, characterized in that: The method comprises: Grooving: creating an etching groove on the packaging material between the filter and the bonding wire of the image sensor sample; Acid corrosion, adding acid solution into the corrosion tank to corrode and clean the packaging material to expose the DAF film and obtain a corroded sample; Baking, baking the corroded sample to obtain a baked sample; Filter stripping: heating the position of the filter in the baked sample until the DAF film in contact with the filter cracks, separating the filter to obtain a sample without the filter; The DAF film is removed, and the DAF film on the surface of the bare chip in the sample after the filter is removed is removed to obtain a component with the bare chip surface exposed.

2. The image sensor processing method according to claim 1, wherein: The baking temperature is 115℃-125℃, and the baking time is 3.5h-4.5h.

3. The image sensor processing method according to claim 1, wherein: The distance between the etching groove and the filter is greater than a preset value; And / or, before the grooving step, X-ray is used to observe the distance between the filter and the bonding wire in the image sensor sample and the thickness of the packaging material to avoid laser damage to the bare chip during grooving.

4. The image sensor processing method according to claim 1, wherein: The etching groove is opened on at least one side of the filter.

5. The image sensor processing method according to claim 1, wherein: The acid solution includes at least one of fuming nitric acid and concentrated sulfuric acid; And / or, the etching step is repeated twice or more, the etching temperature is 95° C.-105° C., and the etching time each time is 4 s-6 s.

6. The image sensor processing method according to claim 1, wherein: The cleaning agent used in the cleaning step is selected from at least one of acetone and alcohol; and / or, each etching step corresponds to a cleaning step; and / or, drying the corroded sample before baking; and / or, the heating temperature in the heating step is 300° C.-350° C.; And / or, in the heating step, a heat source is used to uniformly heat each position of the filter.

7. The image sensor processing method according to claim 1, wherein: The step of removing the DAF film includes: immersing the sample after removing the filter in a solvent, and then peeling off the DAF film on the surface of the bare chip to obtain a component with the bare chip surface exposed.

8. The image sensor processing method according to claim 7, wherein: The solvent is selected from acetone; And / or, the soaking time is 25 min-35 min.

9. A method for image sensor analysis, characterized in that: include: Analyze the components exposed on the surface of the die obtained in the image sensor processing method according to any one of claims 1 to 8.

10. The image sensor analysis method according to claim 9, characterized in that: The image sensor includes, from top to bottom, a filter, a DAF film, a bare die A, a DAF film, a bare die B, and a packaging substrate. The image sensor processing method is used to expose the surface of bare die A and then analyze bare die A. After the analysis of bare die A is completed, the DAF films on the surfaces of bare die A and bare die B are peeled off to expose the surface of bare die B, and then bare die B is analyzed.

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