Unsealing method and application of copper bonding lead semiconductor device

Abstract

The invention discloses an unsealing method and application of a copper bonding wire semiconductor device. The unsealing method comprises the following steps of: 1, confirming a chip position of the device, an area to be unsealed and a material of a bonding wire; step 2, after determining that the material of the bonding lead is copper, thinning the package of the device in the area to be unsealed through a laser unsealing machine to form an exposed area; 3, a chemical reagent is prepared, the chemical reagent is formed by mixing concentrated nitric acid, a copper nitrate saturated solution and a copper material, and the chemical reagent is left to stand and stored in a dark place; 4, dropping the chemical reagent on the exposed area until the chip area is completely exposed; and 5, carrying out surface cleaning and drying on the unsealed device. By means of the mode, corrosion to the copper bonding lead can be reduced while the plastic packaging material is removed completely, and subsequent chip failure analysis is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of electronic component unsealing, and in particular to an unsealing method and application of a copper bonding lead semiconductor device. Background Art

[0002] With the development of the integrated circuit packaging industry, copper bonding leads are increasingly used in plastic-sealed integrated circuits due to their unique advantages. In the process of chip failure analysis, the traditional unsealing method is to use 95% concentrated nitric acid with strong oxidizing properties to corrode the plastic sealing material to achieve the purpose of unsealing. However, for plastic-sealed devices bonded with copper wires, the copper wires will undergo a chemical reaction and be corroded after contacting concentrated acid, resulting in the inability to conduct relevant analysis later. Generally, for plastic-sealed devices bonded with copper wires, laser unsealing equipment is used, and then concentrated nitric acid is used for corrosion. In this case, the copper bonding leads will still be partially corroded.

[0003] Therefore, in order to preserve the bonding structure of the device, an effective unsealing method must be explored to remove the plastic packaging material while reducing corrosion to the copper bonding wires, which is beneficial for subsequent chip failure analysis. Summary of the invention

[0004] The purpose of the present invention is to provide a method for unsealing a semiconductor device with copper bonding wires and its application, which can reduce corrosion to the copper bonding wires while removing the plastic packaging material, thus facilitating subsequent chip failure analysis.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a method for unsealing a copper bonding wire semiconductor device, comprising the following steps:

[0006] Step 1: confirm the chip position of the device, the area to be unsealed and the material of the bonding wire;

[0007] Step 2: After confirming that the material of the bonding wire is copper, thinning the package of the device in the area to be unsealed by a laser unsealing machine to form an exposed area;

[0008] Step 3: preparing a chemical reagent, wherein the chemical reagent is mixed with concentrated nitric acid, a saturated copper nitrate solution and a copper material, and storing the mixture in a static manner away from light;

[0009] Step 4: dripping the chemical reagent on the exposed area until the chip area is completely exposed;

[0010] Step 5: Clean and dry the surface of the unpacked device.

[0011] The step 1 includes: using X-rays to locate the chip position and number of the device, determining the area to be unsealed, preliminarily determining the type of bonding wires, performing preliminary thinning of the device package using a laser unsealing machine, and after the bonding wires appear, using an energy spectrometer to confirm the material of the bonding wires. The use of X-rays to make a preliminary judgment on the material of the bonding wires may involve the risk of misjudgment, and further confirmation using an energy spectrometer is performed. After confirming that the bonding wires are copper, the next step is performed.

[0012] In the step 3, the volume ratio of the saturated copper nitrate solution to concentrated nitric acid is greater than or equal to 3:1, and the content of the copper material is 0.1 g / ml. By preparing a mixed solution of concentrated nitric acid, a saturated copper nitrate solution and a copper material, the saturation effect of copper ions is utilized to reduce the corrosion of the acid solution on the copper bonding wire during the unsealing process.

[0013] The volume ratio of the saturated copper nitrate solution to the concentrated nitric acid is 3 to 15: 1. When the volume ratio of the concentrated nitric acid to the saturated copper nitrate solution is 1: 3 to 1: 15, the chip opening effect is better.

[0014] The step three also includes heating the chemical reagent in a constant temperature furnace at 120±5° C. If the temperature is too low, the reaction time is too long, resulting in a long corrosion packaging time; if the temperature is too high, the concentrated nitric acid in the chemical reagent is easy to volatilize.

[0015] In the step three, the copper material is one of copper powder or copper wire.

[0016] The step 4 includes dropping the chemical reagent on the exposed area, then performing propanol and ultrasonic cleaning, and repeating the above operations until the chip area is completely exposed.

[0017] In step 5, the cleaning process is: cleaning with silicon detergent and deionized water, the volume ratio of silicon detergent to deionized water is 1:500, and then cleaning with anhydrous ethanol. After the device is cleaned with acetone and ultrasonic in step 4, dust may still be attached to the sample surface. Using silicon detergent to clean the device can remove dust and dirt on the sample surface and make the sample surface cleaner.

[0018] In the step 5, the drying process is: blowing nitrogen gas on the chip surface to dry it.

[0019] Another object of the present invention is to provide an application of the unsealing method of the copper bonding wire semiconductor device in failure analysis of packaged chips.

[0020] The beneficial effects of the present invention are as follows: the unsealing method and application of a copper bonding wire semiconductor device of the present invention can reduce the corrosion of the copper bonding wire while removing the plastic packaging material, which is beneficial to the subsequent chip failure analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a flow chart of a method for unsealing a copper bonding wire semiconductor device provided by an embodiment of the present invention;

[0023] Figure 2 It is a photo of a semiconductor device after the chip is opened using existing technology;

[0024] Figure 3 This is a photo of a semiconductor device after the chip is opened provided by Example 1 of the present invention.

[0025] A is the location of the copper bonding wire. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the present invention shown in the accompanying drawings and described according to the accompanying drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0027] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0028] Example 1

[0029] See also Figure 1 , an embodiment of the present invention provides a method for unsealing a copper bonding wire semiconductor device, comprising:

[0030] Step 1: Confirm the chip position of the device, the area to be opened, and the material of the bonding wire.

[0031] Specifically, the step one includes locating the chip position area and the number of chips of the device under X-rays, confirming the area to be unsealed, and preliminarily determining the type of bonding wires. Since the unsealing method provided by the present invention is applicable to semiconductor devices with copper bonding wires, it is necessary to confirm whether the type of bonding wires is copper before unsealing the semiconductor device. The type of bonding wires can be preliminarily determined using X-rays, but there may be a risk of misjudgment, and it is necessary to use an energy spectrometer to further confirm the material of the bonding wires. After confirming that the bonding wires are copper wires, the area to be unsealed is determined. Furthermore, the device package is preliminarily thinned by a laser unsealing machine to expose part of the bonding wires, and then the material of the bonding wires is confirmed using an energy spectrometer.

[0032] Step 2: After confirming that the material of the bonding wire is copper, the package of the device is thinned in the area to be unsealed by a laser unsealing machine to form an exposed area.

[0033] The device package is thinned again by laser decapsulation, and the thickness of the package is reduced as much as possible without exposing the surface of the chip area. The package is thinned by laser, which can shorten the time that the acid liquid contacts the copper bonding wire.

[0034] Step 3: prepare chemical reagents, which are prepared by mixing concentrated nitric acid, a saturated copper nitrate solution and a copper material, and store them in a static and dark place.

[0035] Furthermore, the volume ratio of the saturated copper nitrate solution to concentrated nitric acid is greater than or equal to 3:1. Preferably, the volume ratio of the concentrated nitric acid to the saturated copper nitrate solution is 1:3 to 1:15, and the content of the copper material is 0.1 g / ml. In this embodiment, 10 ml of concentrated nitric acid, 30 ml of saturated copper nitrate solution and 4 g of copper powder are used to prepare chemical reagents. Stir the prepared chemical reagents evenly and put them into a dark brown chemical glass reagent bottle for light protection. Use a constant temperature furnace to heat the chemical reagent at a heating temperature of 120±5°C.

[0036] In another embodiment, the chemical reagent is prepared using 10 ml of concentrated nitric acid, 100 ml of a saturated copper nitrate solution, and 11 g of copper powder.

[0037] For plastic-encapsulated devices bonded with copper wires, the existing unsealing method is to use laser unsealing equipment and then corrode with concentrated nitric acid. In this case, the copper bonding wires will still be corroded, making it impossible to conduct subsequent experiments, such as Figure 2 As shown, the copper bonding wire at position A where the copper bonding wire is located is corroded.

[0038] In this embodiment, the device is corroded by preparing a chemical reagent of concentrated nitric acid, a saturated copper nitrate solution and copper powder. The unsealing effect is shown in FIG. Figure 3It can be seen that at position A where the copper bonding wire is located, the semiconductor device after being unsealed maintains the complete bonding shape of the copper wire, and the unsealing effect is good. The concentrated nitric acid in this chemical reagent can remove the oxidized plastic on the surface of the chip on the one hand, and on the other hand, it can form a layer of aluminum oxide film on the surface of the aluminum layer of the chip window connected to the copper bonding wire to protect the aluminum layer from further corrosion. The saturated copper nitrate solution and copper powder in this chemical reagent are used to provide copper ions, and the saturation effect of copper ions is used to avoid the concentrated nitric acid from directly reacting with the copper bonding wire, weaken the corrosion of the concentrated nitric acid on the copper bonding wire, and retain the original appearance of the copper bonding wire.

[0039] In addition, the inventors found in the early stage of the experiment that when the content of the saturated solution of copper nitrate is lower than that of concentrated nitric acid, the copper bonding wires are easily damaged and the unsealing effect is poor; when the proportion of concentrated nitric acid in the chemical reagent is too small, it will cause the corrosion packaging time to be too long, and it will also cause the aluminum layer of the chip window connected to the copper bonding wires to be damaged, and the unsealing requirements cannot be met.

[0040] In another embodiment, the copper powder in the chemical reagent can be replaced by copper wire.

[0041] Step 4: Drop the chemical reagent on the exposed area until the chip area is completely exposed.

[0042] Furthermore, this step includes dripping a chemical solvent on the exposed area of ​​the package, then performing propanol and ultrasonic cleaning, observing the semiconductor device after cleaning, and if the chip and bonding wires are not completely exposed, chemically corroding and cleaning the device again, and repeating the above operations multiple times until the chip area package is completely exposed.

[0043] Step 5: Clean and dry the surface of the unpacked device.

[0044] The unpacked device is cleaned with silicon detergent and deionized water, the volume ratio of the silicon detergent to deionized water is 1:500, and then cleaned with anhydrous ethanol, and the chip surface is purged with nitrogen to dry it. After the device is cleaned with acetone and ultrasonic in step 4, dust may still be attached to the sample surface. Cleaning the device with silicon detergent can remove dust and dirt on the sample surface and make the sample surface cleaner.

[0045] The unsealing method of a semiconductor device with copper bonding wires of the present invention can reduce the corrosion of the copper bonding wires while removing the plastic packaging material, which is beneficial to the subsequent chip failure analysis.

[0046] A method for unsealing a copper bonding wire semiconductor device provided by an embodiment of the present invention is applied in the field of failure analysis of packaged chips.

[0047] In addition, it should be noted that in this specification, "includes", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0048] It should be understood that although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for unsealing a copper bonded wire semiconductor device, characterized in that: The following steps are involved: Step 1: confirm the chip position of the device, the area to be unsealed and the material of the bonding wire; Step 2: After confirming that the material of the bonding wire is copper, thinning the package of the device in the area to be unsealed by a laser unsealing machine to form an exposed area; Step 3: preparing a chemical reagent, wherein the chemical reagent is mixed with concentrated nitric acid, a saturated copper nitrate solution and a copper material, and storing the mixture in a static manner away from light; Step 4: dripping the chemical reagent on the exposed area until the chip area is completely exposed; Step 5: Clean and dry the surface of the unpacked device.

2. The method for unsealing a copper-bonded lead semiconductor device according to claim 1, characterized in that: The step one includes: using X-rays to locate the chip position and chip number of the device, determining the area to be unsealed, preliminarily determining the type of bonding wires, performing preliminary thinning of the device package by a laser unsealing machine, and after the bonding wires appear, confirming the material of the bonding wires by an energy spectrometer.

3. The method for unsealing a copper-bonded lead semiconductor device according to claim 1, characterized in that: In the step three, the volume ratio of the saturated copper nitrate solution to concentrated nitric acid is greater than or equal to 3:1, and the content of the copper material is 0.1 g / ml.

4. The method for unsealing a copper-bonded lead semiconductor device according to claim 3, characterized in that: The volume ratio of the saturated copper nitrate solution to concentrated nitric acid is 3-15:

1.

5. The method for unsealing a copper-bonded lead semiconductor device according to claim 1, characterized in that: The step three also includes heating the chemical reagent using a constant temperature furnace, wherein the temperature of the constant temperature furnace is 120±5°C.

6. The method for unsealing a copper-bonded lead semiconductor device according to claim 1, characterized in that: In the step three, the copper material is one of copper powder or copper wire.

7. The method for unsealing a copper-bonded lead semiconductor device according to claim 1, characterized in that: The step 4 includes dropping the chemical reagent on the exposed area, then performing propanol and ultrasonic cleaning, and repeating the above operations until the chip area is completely exposed.

8. The method for unsealing a copper-bonded lead semiconductor device according to claim 1, characterized in that: In the step five, the cleaning process is: cleaning with a silicon detergent and deionized water, the volume ratio of the silicon detergent to deionized water is 1:500, and then cleaning with anhydrous ethanol.

9. The method for unsealing a copper-bonded lead semiconductor device according to claim 1, characterized in that: In the step 5, the drying process is: blowing nitrogen gas on the chip surface to dry it.

10. Use of the method for unsealing a semiconductor device with copper bonding wires according to any one of claims 1 to 9 in failure analysis of packaged chips.

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