How to open the GaAs chip

Abstract

The present invention provides a gallium arsenide chip unsealing method, belonging to the field of chip technology. The method comprises the following steps: S1: grinding the target unsealing area of ​​the gallium arsenide chip to a rough surface; S2: dropping a mixed acid liquid on the roughened target unsealing area, heating the gallium arsenide chip to a target temperature, timing from the reaction of the target unsealing area to produce brown-red bubbles, to the first preset reaction time, and cleaning the gallium arsenide chip; S3: repeatedly executing S2 until the surface of the gallium arsenide chip is visible to the naked eye; S4: adjusting the reaction time to the second preset time, repeatedly executing S2 until the target unsealing area no longer reacts, cleaning the gallium arsenide chip and completing the unsealing, and obtaining a chip exposing the surface circuit of the gallium arsenide chip. Grinding the target unsealing area can remove the oxide layer and dirt on the surface, limit the reaction area, realize local unsealing, and use the encapsulation body to protect the gallium arsenide substrate to prevent the acid from reacting with gallium arsenide.

Description

Technical Field

[0001] The present invention relates to the field of chip technology, and in particular to a gallium arsenide chip unsealing method. Background Art

[0002] The chip is composed of multiple layers of metal wires, dielectric layers and through holes, where each layer of metal wires is isolated by the dielectric layer and connected through through holes. When the chip fails or the internal circuit structure is analyzed, the packaging material on the chip surface needs to be removed.

[0003] Removing the packaging material from the chip surface, referred to as unsealing, uses physical or chemical methods to remove the packaging material to expose the chip surface circuit for subsequent process or circuit analysis.

[0004] Gallium arsenide is an important semiconductor material, belonging to the III-V group of compound semiconductors. The electron mobility of gallium arsenide is 5 to 6 times greater than that of silicon, so it is widely used in the manufacture of microwave devices and high-speed digital circuits. The chemical properties of gallium arsenide are relatively stable at room temperature, but it can react with hot concentrated nitric acid, hydrochloric acid and sulfuric acid.

[0005] Gallium arsenide radio frequency chips refer to chips that are made of gallium arsenide as a semiconductor material and are used in the radio frequency field. In these chips, gallium arsenide is often used as a substrate material, and other circuits are formed on the substrate material.

[0006] The existing method for decapsulating gallium arsenide RF chips is to directly immerse the chip in concentrated nitric acid or concentrated sulfuric acid to heat and corrode the packaging material. Due to the property of gallium arsenide that it can react with hot concentrated nitric acid, hydrochloric acid and sulfuric acid, the above method will cause the gallium arsenide substrate to be corroded, making it difficult to obtain a complete chip and impossible to analyze the chip surface circuit. Summary of the invention

[0007] The purpose of the embodiment of the present invention is to provide a gallium arsenide chip unsealing method. After polishing the target unsealing area, the surface oxide layer or other dirt can be removed, the initial reaction rate can be accelerated, and the rough surface can limit the reaction area. In this way, the surface of the gallium arsenide chip can be partially unsealed, and the packaging body can be fully utilized to protect the gallium arsenide substrate, prevent the acid from reacting with gallium arsenide, and obtain a complete chip after unsealing.

[0008] In order to achieve the above object, the present invention provides a method for unpacking a gallium arsenide chip in a first aspect, the method comprising the following steps:

[0009] S1: Polish the target opening area of ​​the GaAs chip to a rough surface;

[0010] S2: dropping the mixed acid liquid on the roughened target unsealed area, heating the GaAs chip to a target temperature, and timing from the time when brown-red bubbles are generated in the target unsealed area to the first preset reaction time, thereby cleaning the GaAs chip;

[0011] S3: Repeat S2 until the surface of the GaAs chip is visible to the naked eye;

[0012] S4: adjusting the reaction time to a second preset time, and repeatedly executing S2 until the target unsealing area no longer reacts, and the unsealing is completed after the gallium arsenide chip is cleaned to obtain a chip with the surface circuit of the gallium arsenide chip exposed.

[0013] Further, the target temperature is 60°C-80°C; the first preset time is 10-20s;

[0014] The step S2 specifically includes:

[0015] S201: dropping 2-3 drops of mixed acid liquid on the roughened target opening area;

[0016] S202: heating the gallium arsenide chip to a target temperature, and counting the time from when the target unsealed area reacts to produce brown-red bubbles, to a first preset reaction time;

[0017] S203: placing the gallium arsenide chip in a cleaning agent, and taking it out after ultrasonic cleaning for a third preset time.

[0018] Optionally, the target temperature is 70°C; and the first preset time is 15s.

[0019] Optionally, the cleaning agent is acetone or butanone.

[0020] Optionally, the third preset time is 1-2 minutes.

[0021] Optionally, the third preset time is 1.5 minutes.

[0022] Optionally, the mixed acid solution is a mixed acid of concentrated nitric acid and acetic acid, the volume ratio of concentrated nitric acid to acetic acid is 1:1 to 1:2, the concentrated nitric acid is 98% by mass, and the acetic acid is 99.5% by mass of analytical grade acetic acid. By using a mixed acid of concentrated nitric acid and acetic acid, acetic acid can buffer the reaction rate of concentrated nitric acid. When the mixed acid reacts with the packaging material, the initial rate is slower than that of concentrated nitric acid. After a period of reaction, the concentrated nitric acid is diluted, but due to the buffering of acetic acid, a relatively fast reaction rate can be guaranteed, and the integrity of the gallium arsenide chip after opening can be further ensured.

[0023] Optionally, the volume ratio of concentrated nitric acid to acetic acid in the mixed acid solution is 1:1.5.

[0024] Optionally, the second preset time is 5-10s.

[0025] Optionally, the second preset time is 8s.

[0026] Through the above technical scheme, a method for unsealing a gallium arsenide chip is provided. The method can remove the oxide layer or other dirt on the surface by polishing the target unsealing area, which can accelerate the initial reaction rate. At the same time, the rough surface can limit the reaction area. In this way, the surface of the gallium arsenide chip can be partially unsealed, and the packaging body can be fully utilized to protect the gallium arsenide substrate, prevent the acid from reacting with gallium arsenide, and obtain a complete chip after unsealing.

[0027] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0029] Figure 1 It is a flow chart of a method for unsealing a gallium arsenide chip provided by one embodiment of the present invention;

[0030] Figure 2 This is a microscope observation picture of the gallium arsenide chip after opening obtained in Experimental Example 1 of the present invention;

[0031] Figure 3 This is a microscope observation picture of the gallium arsenide chip after opening obtained in Experimental Example 2 of the present invention;

[0032] Figure 4 This is a microscope observation picture of the gallium arsenide chip after opening obtained in Experimental Example 3 of the present invention. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0034] Figure 1 The flowchart of the method for unsealing a gallium arsenide chip provided in one embodiment of the present invention is shown in FIG1 . The method comprises the following steps:

[0035] S1: Grind the target unsealing area of ​​the GaAs chip to make it rough. In this application, the GaAs chip is fixed on a stainless steel or ceramic substrate with the chip surface circuit facing upward. The target unsealing area is located on the side directly facing the chip surface circuit. The target unsealing area can be circular, square, etc.;

[0036] S2: After dropping the mixed acid liquid on the roughened target unsealed area, heat the gallium arsenide chip to make it at the target temperature, start timing from the reaction of the target unsealed area to produce brown-red bubbles, and end the reaction for the first preset time, and clean the gallium arsenide chip. In this application, the target temperature is 60°C-80°C; the first preset time is 10-20s. The specific steps include:

[0037] S201: dropping 2-3 drops of mixed acid liquid on the roughened target opening area;

[0038] S202: heating the GaAs chip to a target temperature, and counting from the time when brown-red bubbles are generated in the target unsealed area, to the time when the reaction lasts for a first preset time;

[0039] S203: placing the gallium arsenide chip in a cleaning agent, and taking it out after ultrasonic cleaning for a third preset time. In the present application, the cleaning agent is acetone or butanone; the third preset time is 1-2 minutes.

[0040] S3: Repeat S2 until the surface of the GaAs chip is visible to the naked eye;

[0041] S4: Adjust the reaction time to a second preset time, and repeat S2 until the target unsealing area no longer reacts. After cleaning the GaAs chip, the unsealing is completed to obtain a chip with the GaAs chip surface circuit exposed. In the present application, the second preset time is 5-10s.

[0042] In a preferred embodiment, the target temperature is 70° C.; and the first preset time is 15 seconds.

[0043] In a preferred embodiment, the third preset time is 1-2 minutes.

[0044] In a preferred embodiment, the third preset time is 1.5 minutes.

[0045] In the present application, the mixed acid solution is a mixed acid of concentrated nitric acid and acetic acid, the volume ratio of concentrated nitric acid to acetic acid is 1:1 to 1:2, the concentrated nitric acid is 98% nitric acid by mass, and the acetic acid is 99.5% acetic acid by mass of analytical grade. By using a mixed acid of concentrated nitric acid and acetic acid, acetic acid can buffer the reaction speed of concentrated nitric acid. When the mixed acid reacts with the packaging material, the initial speed is slower than that of concentrated nitric acid. After a period of reaction, the concentrated nitric acid is diluted, but due to the buffering of acetic acid, a relatively fast reaction speed can be guaranteed, and the integrity of the gallium arsenide chip after opening can be further ensured.

[0046] In a preferred embodiment, the volume ratio of concentrated nitric acid to acetic acid in the mixed acid solution is 1:1.5.

[0047] In a preferred embodiment, the second preset time is 8 seconds.

[0048] In this application, metal or ceramic tweezers are required to take and place the GaAs chip, and the entire unsealing process needs to be carried out in a fume hood. The mixed acid solution is sucked and dripped onto the target unsealing area of ​​the GaAs chip using a 90mm or 100mm rubber-tipped dropper.

[0049] Experimental Example 1

[0050] In the first experimental example of this application, the steps for unsealing the GaAs chip are as follows:

[0051] Step 1: Polish the target opening area of ​​the GaAs chip until it is rough;

[0052] Step 2: Drop 3 drops of mixed acid solution on the roughened target unsealed area, where the volume ratio of concentrated nitric acid to acetic acid in the mixed acid solution is 1:1; heat the gallium arsenide chip to 60°C, observe the state of the target unsealed area, and start timing from the time when the target unsealed area reacts to produce brown-red bubbles. The reaction time is 10s, and the heating is stopped; use metal or ceramic tweezers to put the reacted gallium arsenide chip into acetone cleaning agent for ultrasonic cleaning for 2 minutes and then take it out;

[0053] Step 3: Repeat step 2 4 times, at which point the surface of the GaAs chip is visible to the naked eye;

[0054] Step 4: Drop 3 drops of mixed acid solution on the target unsealing area of ​​the GaAs chip obtained in step 3, with the volume ratio of concentrated nitric acid to acetic acid in the mixed acid solution being 1:1; heat the GaAs chip to 60°C, observe the state of the target unsealing area, and start recording the reaction time from the time when brown-red bubbles begin to appear in the target unsealing area. After 5 seconds of reaction, stop heating; use metal or ceramic tweezers to put the reacted GaAs chip into acetone cleaning agent for ultrasonic cleaning for 2 minutes and then take it out. At this time, the surface circuit of the GaAs chip is not completely exposed;

[0055] Step 5: Repeat step 4 once. After cleaning, the surface circuit of the GaAs chip is completely exposed and the unsealing is completed. Place the unsealed GaAs chip under a microscope for observation and collect images such as Figure 2 As shown in the figure, the circuit on the chip surface has been completely exposed, the packaging material in the target area is obviously uneven after corrosion, and there is no obvious corrosion on the gallium arsenide substrate.

[0056] Experimental Example 2

[0057] In the second experimental example of the present application, the steps for unsealing the GaAs chip are as follows:

[0058] Step 1: Grind the target opening area on the front of the GaAs chip until it is rough;

[0059] Step 2: Drop 2 drops of mixed acid solution on the roughened target unsealed area, where the volume ratio of concentrated nitric acid to acetic acid in the mixed acid solution is 1:1.5; heat the gallium arsenide chip to 70°C, observe the state of the target unsealed area, and start timing from the time when the target unsealed area reacts to produce brown-red bubbles. The reaction time is 15s, and then stop heating; use metal or ceramic tweezers to put the reacted gallium arsenide chip into acetone cleaning agent for ultrasonic cleaning for 1.5 minutes and then take it out;

[0060] Step 3: Repeat step 2 5 times. At this time, the surface of the GaAs chip can be clearly seen by the naked eye.

[0061] Step 4: Drop 2 drops of mixed acid liquid on the target unsealing area of ​​the GaAs chip obtained in step 3. The volume ratio of concentrated nitric acid to acetic acid in the mixed acid liquid is 1:1.5; heat the GaAs chip to 70°C, observe the state of the target unsealing area, and start recording the reaction time from the time when brown-red bubbles begin to appear in the target unsealing area. After 8 seconds of reaction, stop heating; use metal or ceramic tweezers to put the reacted GaAs chip into acetone cleaning agent for ultrasonic cleaning for 1.5 minutes and then take it out. At this time, the surface circuit of the GaAs chip has been completely exposed and the unsealing is completed. Place the unsealed GaAs chip under a microscope for observation and collect images such as Figure 3 As shown in the figure, the circuit on the chip surface has been completely exposed, the bonding wires are clearly visible, and there is no obvious corrosion on the gallium arsenide substrate.

[0062] Experimental Example 3

[0063] In the third experimental example of the present application, the steps for unsealing the GaAs chip are as follows:

[0064] Step 1: Grind the target opening area on the front of the GaAs chip until it is rough;

[0065] Step 2: Drop 3 drops of mixed acid solution on the roughened target unsealed area, where the volume ratio of concentrated nitric acid to acetic acid in the mixed acid solution is 1:2; heat the gallium arsenide chip to 80°C, observe the state of the target unsealed area, and start timing from the time when the target unsealed area reacts to produce brown-red bubbles. The reaction time is 20s, and the heating is stopped; use metal or ceramic tweezers to put the reacted gallium arsenide chip into a butanone cleaning agent for ultrasonic cleaning for 2 minutes and then take it out;

[0066] Step 3: Repeat step 2 3 times, at this point the surface of the GaAs chip is visible to the naked eye;

[0067] Step 4: Drop 3 drops of mixed acid liquid on the target unsealing area of ​​the GaAs chip obtained in step 3. The volume ratio of concentrated nitric acid to acetic acid in the mixed acid liquid is 1:2; heat the GaAs chip to 80°C, observe the state of the target unsealing area, and start recording the reaction time from the time when brown-red bubbles begin to appear in the target unsealing area. After 10 seconds of reaction, stop heating; use metal or ceramic tweezers to put the reacted GaAs chip into acetone cleaning agent for ultrasonic cleaning for 2 minutes and then take it out. At this time, the surface circuit of the GaAs chip has been completely exposed and the unsealing is completed. Place the unsealed GaAs chip under a microscope for observation and collect images such as Figure 4 As shown in the figure, the circuit on the chip surface has been completely exposed, and there is no obvious corrosion on the gallium arsenide substrate.

[0068] Comparative Example 1

[0069] In a comparative example of the present application, the gallium arsenide chip is unsealed in the following manner.

[0070] The GaAs chip was immersed in hot concentrated nitric acid for 20 seconds, then taken out and ultrasonically cleaned in acetone, and repeated several times until the GaAs chip circuit was completely exposed. The chip's peripheral packaging materials were all corroded away, and the internal GaAs substrate and chip pins were severely corroded.

[0071] Comparing Experimental Examples 1 to 3 with the Comparative Example, Figure 2-4 It can be seen that the method of the present invention partially unseals the surface of the gallium arsenide radio frequency chip, making full use of the package to protect the gallium arsenide substrate and prevent the acid solution from reacting with gallium arsenide. Secondly, the present invention uses a mixed acid solution of concentrated nitric acid and acetic acid to reduce the reaction speed at the initial stage of the reaction and increase the reaction speed at the later stage of the reaction, making the reaction speed more balanced and increasing the integrity of the gallium arsenide chip after unsealing.

[0072] The optional embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, the technical scheme of the embodiments of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0073] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A method for unsealing a gallium arsenide chip, characterized in that: The method comprises the following steps: S1: Polish the target opening area of ​​the GaAs chip to a rough surface; S2: After dropping the mixed acid liquid on the roughened target unsealed area, heating the GaAs chip to make it at the target temperature, timing from the time when the target unsealed area reacts to produce brown-red bubbles to the first preset reaction time, cleaning the GaAs chip, the target temperature is 60°C-80°C; the first preset time is 10-20s; S3: Repeat S2 until the surface of the GaAs chip is visible to the naked eye; S4: adjusting the reaction time to a second preset time, and repeatedly executing S2 until the target unsealing area no longer reacts, and completing the unsealing after cleaning the GaAs chip to obtain a chip with the GaAs chip surface circuit exposed, wherein the second preset time is 5-10s.

2. The method for unsealing a gallium arsenide chip according to claim 1, characterized in that: The step S2 specifically includes: S201: dropping 2-3 drops of mixed acid liquid on the roughened target opening area; S202: heating the gallium arsenide chip to a target temperature, and counting the time from when the target unsealed area reacts to produce brown-red bubbles, to a first preset reaction time; S203: placing the gallium arsenide chip in a cleaning agent, and taking it out after ultrasonic cleaning for a third preset time.

3. The method for unsealing a gallium arsenide chip according to claim 2, characterized in that: The target temperature is 70° C.; the first preset time is 15 seconds.

4. The method for unsealing a gallium arsenide chip according to claim 2, characterized in that: The cleaning agent is acetone or butanone.

5. The method for unsealing a gallium arsenide chip according to claim 2, characterized in that: The third preset time is 1-2 minutes.

6. The method for unsealing a gallium arsenide chip according to claim 4, characterized in that: The third preset time is 1.5 minutes.

7. The method for unsealing a gallium arsenide chip according to claim 1 or 2, characterized in that: The mixed acid solution is a mixed acid of concentrated nitric acid and acetic acid, the volume ratio of concentrated nitric acid to acetic acid is 1:1-1:2, the concentrated nitric acid is 98% nitric acid by mass, and the acetic acid is 99.5% analytically pure acetic acid by mass.

8. The method for unsealing a gallium arsenide chip according to claim 7, characterized in that: The volume ratio of concentrated nitric acid to acetic acid in the mixed acid solution is 1:1.

5.

9. The method for unsealing a gallium arsenide chip according to claim 1, characterized in that: The second preset time is 8s.

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