Disclosure of Invention
In view of the problems, the present application has been made to provide a method for delamination of a surface layer of a silicon carbide chip that overcomes the problems or at least partially solves the problems, comprising:
a method for removing a layer on a surface layer of a silicon carbide chip comprises the following steps:
removing the passivation layer of the silicon carbide chip through the ethanolamine solution;
removing the copper foil layer, the silver sintered layer and the nickel-palladium-gold layer of the silicon carbide chip by nitric acid;
performing an electrical test on the silicon carbide chip;
and removing the aluminum copper layer of the silicon carbide chip through aqua regia to obtain the silicon carbide chip with the surface layer removed.
Further, the step of removing the passivation layer of the silicon carbide chip by the ethanolamine solution comprises the following steps:
heating the ethanolamine solution to 150 ℃;
and placing the silicon carbide chip in the ethanolamine solution, and corroding for 30-60 min.
Further, the concentration of the ethanolamine solution is not less than 99%.
Further, the step of removing the copper foil layer, the silver sintered layer and the nickel palladium gold layer of the silicon carbide chip by nitric acid comprises the following steps:
alternately dripping nitric acid and deionized water to remove the copper foil layer of the silicon carbide chip;
and alternately dropwise adding nitric acid and deionized water into the silicon carbide chip to corrode, and removing the silver sintered layer and the nickel-palladium-gold layer.
Further, the nitric acid is fuming nitric acid with the concentration of not less than 95%.
Further, the step of performing an electrical test on the silicon carbide chip includes:
placing the silicon carbide chip in alcohol for ultrasonic oscillation cleaning;
taking out the cleaned silicon carbide chip and drying;
and performing electrical test and hot spot analysis on the dried silicon carbide chip.
Further, the step of removing the aluminum copper layer of the silicon carbide chip by aqua regia to obtain the silicon carbide chip with the surface layer removed comprises the following steps:
heating the aqua regia to 100 ℃;
and adding the heated aqua regia to the surface of the silicon carbide chip, and etching the silicon carbide chip to remove the copper-aluminum layer.
Further, the aqua regia is a mixed solution with the volume ratio of hydrochloric acid to nitric acid being 3:1; wherein the concentration of the hydrochloric acid is 36% -38%, and the concentration of the nitric acid is 69% -71%.
Further, the heated aqua regia is dripped on the surface of the silicon carbide chip, and after the step of corroding the silicon carbide chip to remove the copper aluminum layer, the method further comprises the following steps:
performing an electrical test on the silicon carbide chip; wherein the test voltage is less than 200V.
Further, after the step of removing the aluminum copper layer of the silicon carbide chip by aqua regia to obtain the silicon carbide chip with the surface layer removed, the method further comprises the following steps:
and placing the silicon carbide chip in alcohol, performing ultrasonic oscillation cleaning and drying.
The application has the following advantages:
in the embodiment of the application, for carrying out wet etching with only single etching solution among the prior art, easily produce the damage to the chip and can have a large amount of dirty shortcoming, the application provides the solution of getting rid of the different metal layers in chip surface respectively, specifically: removing the passivation layer of the silicon carbide chip through the ethanolamine solution; removing the copper foil layer, the silver sintered layer and the nickel-palladium-gold layer of the silicon carbide chip by nitric acid; performing an electrical test on the silicon carbide chip; and removing the aluminum copper layer of the silicon carbide chip through aqua regia to obtain the silicon carbide chip with the surface layer removed. The method solves the problem that a large amount of dirt exists to influence the removal efficiency by removing different metal layers of the silicon carbide chip step by step, and does not damage the silicon carbide chip body in the removal process; meanwhile, the electrical test is performed in the middle of removal, which metal layer affects the electrical parameters of the chip can be clarified, and different chip delamination degrees can meet specific failure analysis requirements, such as electrical performance test or hot spot positioning analysis.
Detailed Description
In order to make the objects, features and advantages of the present application more comprehensible, the present application is described in further detail below with reference to the accompanying drawings and detailed description. It will be apparent that the embodiments described are some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
The inventors found by analyzing the prior art that: in the prior art, the metal layer is removed by corrosion through hydrochloric acid or sodium hydroxide solution, so that the etching time is overlong for chips with a large number of layers, a large amount of dirt is generated during long-time etching, and the chip body structure is easily damaged.
Referring to fig. 1, a method for removing a silicon carbide chip surface layer according to an embodiment of the present application is shown;
the method comprises the following steps:
s110, removing a passivation layer of the silicon carbide chip through an ethanolamine solution;
s120, removing the copper foil layer, the silver sintered layer and the nickel-palladium-gold layer of the silicon carbide chip through nitric acid;
s130, performing electrical test on the silicon carbide chip;
and S140, removing the aluminum copper layer of the silicon carbide chip through aqua regia to obtain the silicon carbide chip with the surface layer removed.
In the embodiment of the application, for carrying out wet etching with only single etching solution among the prior art, easily produce the damage to the chip and can have a large amount of dirty shortcoming, the application provides the solution of getting rid of the different metal layers in chip surface respectively, specifically: removing the passivation layer of the silicon carbide chip through the ethanolamine solution; removing the copper foil layer, the silver sintered layer and the nickel-palladium-gold layer of the silicon carbide chip by nitric acid; performing an electrical test on the silicon carbide chip; and removing the aluminum copper layer of the silicon carbide chip through aqua regia to obtain the silicon carbide chip with the surface layer removed. The method solves the problem that a large amount of dirt exists to influence the removal efficiency by removing different metal layers of the silicon carbide chip step by step, and does not damage the silicon carbide chip body in the removal process; meanwhile, the electrical test is performed in the middle of removal, which metal layer affects the electrical parameters of the chip can be clarified, and different chip delamination degrees can meet specific failure analysis requirements, such as electrical performance test or hot spot positioning analysis.
Next, a method of removing a layer from the surface layer of a silicon carbide chip in this exemplary embodiment will be further described.
The passivation layer of the silicon carbide chip is removed by the ethanolamine solution as described in the step S110.
In one embodiment of the present invention, the specific process of "removing the passivation layer of the silicon carbide chip by ethanolamine solution" described in step S110 may be further described in conjunction with the following description.
Heating the ethanolamine solution to 150 ℃ as follows;
and (3) placing the silicon carbide chip in the ethanolamine solution, and corroding for 30-60 min.
As described in the following steps, the concentration of the ethanolamine solution is not less than 99%
It should be noted that, when the chip surface passivation layer (polyimide) is etched by using an ethanolamine solution with a concentration not less than 99.0%, the chip is placed in a liquid ethanolamine solution for etching when the chip surface passivation layer (polyimide) is removed, and during the etching process, the ethanolamine only etches the chip surface passivation layer (polyimide) and does not cause chemical etching to other layers, the chip to be analyzed is placed in the ethanolamine solution, and the ethanolamine heating temperature is 150 ℃ and the etching time is 0.5-1 hour.
The copper foil layer, the silver sintered layer and the nickel palladium gold layer of the silicon carbide chip are removed by nitric acid as described in the step S120.
In one embodiment of the present invention, the specific process of "removing the copper foil layer, the silver sintered layer, and the nickel palladium gold layer of the silicon carbide chip by nitric acid" described in step S120 may be further described in conjunction with the following description.
The method comprises the following steps of alternately dripping nitric acid and deionized water to remove the copper foil layer of the silicon carbide chip;
alternately dropwise adding nitric acid and deionized water into the silicon carbide chip to corrode the silicon carbide chip, and removing a silver sintered layer and a nickel-palladium-gold layer;
the nitric acid is fuming nitric acid with a concentration of not less than 95%, as described in the following steps.
The copper foil layer, the silver sintered layer and the nickel palladium gold layer on the surface of the chip are sequentially subjected to acid-dropping corrosion by fuming nitric acid with the concentration of not less than 95.0%, the surface copper foil layer, the silver sintered layer and the nickel palladium gold layer can be removed rapidly, the heating temperature of fuming nitric acid is 100 ℃, fuming nitric acid and deionized water are needed to be alternately performed when the copper foil layer is removed by acid-dropping, the reaction time of dilute nitric acid on the copper foil layer is short, the effect is better, in addition, the nickel layer in the nickel palladium gold layer is at the lowest layer, the upper palladium gold layer can drop from the chip along with the nickel layer after the nickel layer is removed, and the fuming nitric acid does not react with the aluminum copper layer at normal temperature, so that the copper foil layer is removed, the lower aluminum copper layer cannot be corroded by fuming nitric acid when the silver sintered layer and the nickel palladium gold layer, and the aluminum copper layer can be reserved as a test probe contact connection layer.
The silicon carbide chip is electrically tested as described in the step S130. The step test can also be used for other related tests according to specific requirements.
In one embodiment of the present invention, the specific process of "performing electrical test on the silicon carbide chip" in step S130 may be further described in conjunction with the following description.
The silicon carbide chip is placed in alcohol for ultrasonic oscillation cleaning;
taking out the silicon carbide chip after cleaning and drying the silicon carbide chip;
and performing electrical testing and hot spot analysis on the dried silicon carbide chip as follows.
If the over-test voltage is higher than 200V, the chip can be placed into a beaker filled with alcohol before the aluminum copper layer is removed, the beaker is placed into an ultrasonic cleaner for ultrasonic vibration cleaning for about 2 minutes to remove surface contaminants, the chip is taken out and placed into a 125 ℃ oven for baking, and the chip can be taken out for testing and hot spot analysis after 5 minutes. If the aluminum-copper layer is stripped, the compressive strength of the chip is reduced because the aluminum-copper layer is removed, and only a low-voltage test can be performed, and a test for over 200V leakage failure and a hot spot analysis are performed before the removal of the copper-aluminum layer.
And (S140) removing the aluminum copper layer of the silicon carbide chip by using aqua regia to obtain the silicon carbide chip with the surface layer removed.
In an embodiment of the present invention, the specific process of "removing the aluminum copper layer of the silicon carbide chip by aqua regia to obtain the silicon carbide chip after surface layer delamination" in step S140 may be further described in conjunction with the following description.
Heating the aqua regia to 100 ℃ as follows;
the heated aqua regia is dripped on the surface of the silicon carbide chip, and the silicon carbide chip is corroded to remove a copper aluminum layer;
the aqua regia is a mixed solution with the volume ratio of hydrochloric acid to nitric acid of 3:1; wherein the concentration of the hydrochloric acid is 36% -38%, and the concentration of the nitric acid is 69% -71%.
It should be noted that, after the aluminum copper layer is removed, a layer of titanium+titanium nitride layer remains on the surface of the chip, so that the probe connection test analysis can be performed.
In an embodiment of the present application, after the step of dropping the heated aqua regia onto the surface of the silicon carbide chip and etching the silicon carbide chip to remove the copper-aluminum layer, an electrical test is further performed on the silicon carbide chip; wherein the test voltage is less than 200V.
It should be noted that, due to the peeling of the aluminum copper layer, the surface metal will not block photon scattering during the analysis of the bright point of the gallium arsenide indium micro-light microscope, and is easy to be captured by the infrared detector, thus being helpful for the localization of the failure analysis hot point, but the leakage test can only be performed under low pressure after the aluminum copper layer is removed, and the chip compressive strength is reduced and the test with voltage less than 200V can only be performed because the aluminum copper layer is removed.
In an embodiment of the present application, after the step of removing the aluminum copper layer of the silicon carbide chip by aqua regia to obtain the silicon carbide chip with the surface layer removed, the method further includes: and placing the silicon carbide chip in alcohol, performing ultrasonic oscillation cleaning and drying.
It should be noted that, placing the chip into a beaker containing alcohol, placing the beaker into an ultrasonic cleaner to clean for about 2 minutes by ultrasonic oscillation, then cleaning for about 2 minutes by ultrasonic oscillation again by using deionized water, taking out the chip, placing the chip into a 125 ℃ oven for baking and drying, and taking out the chip after 5 minutes for testing and hot spot analysis.
While preferred embodiments of the present embodiments have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the present application.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or terminal device comprising the element.
The foregoing has described in detail a method for removing a layer from a surface layer of a silicon carbide chip provided by the present application, and specific examples are applied herein to illustrate the principles and embodiments of the present application, where the foregoing examples are provided to assist in understanding the method and core ideas of the present application; meanwhile, as those skilled in the art will have modifications in the specific embodiments and application scope in accordance with the ideas of the present application, the present description should not be construed as limiting the present application in view of the above.