Improved method for cutting LED chips with offset

Abstract

The present application relates to a kind of improved offset LED chip cutting method.The method includes the following steps: (1) glueing;(2) photoetching: the LED chip P face after gluing is exposed, and the identification cutting path and offset scale mark are obtained;(3) developing;(4) etching;(5) removing glue;(6) pasting film;(7) cutting.The present application improves the conventional LED chip cutting process, adds the identification cutting path and offset scale mark, cuts by letting blade along the identification cutting path, and sets offset scale mark on the path of identification cutting path to carry out visual data adjustment, equivalent to a ruler to carry out real-time offset measurement, effectively improves the problem of adjusting offset in conventional LED chip cutting process by experience, greatly improves the qualified rate of chip cutting, reduces production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to an improved offset LED chip cutting method, belonging to the technical field of LED chips. BACKGROUND

[0002] LED chips, as the core components of semiconductor lighting, play an important role in the lighting industry. LED is called the fourth generation of lighting or green light source, with the characteristics of energy saving, environmental protection, long service life, small size, etc., and is widely used in various fields such as indication, display, decoration, backlight, general lighting and urban night scene. According to the different use functions, it can be divided into five categories: information display, signal lamp, vehicle lamp, liquid crystal screen backlight, and general lighting. LED chips have high luminous efficiency, wide color range, and long service life, and have been widely used in large-screen display, landscape lighting, traffic signal lights, and automobile state display. Therefore, the final appearance shape of LED chips will directly affect the quality of their electrical performance parameters, so the requirements for chip appearance in the LED industry are quite strict, especially for smaller sizes. The important factor affecting the appearance of LED chips and the subsequent encapsulation wire bonding quality is the offset of the cutting mark during the cutting process (also known as sawing offset in the industry, which is a direct explanation of the distance between the P electrode of the LED chip and the edge of the chip. Unequal length), which will cause the solder ball position to deviate during LED chip soldering, affecting the light output and other performance parameters.

[0003] In the LED chip preparation process, cutting is the process of dividing the entire chip after basic processes such as photolithography, film plating, and thinning into single dies of the required size, which is an indispensable post-process in the preparation process of semiconductor light-emitting diode chips. For LED chips, the most widely used cutting method in the industry is blade cutting. Blade cutting is a process in which a high-speed rotating spindle drives a blade installed on the upper edge to cut the chip completely into single dies according to the desired program. During the cutting process, the cutting mark of the blade will experience a small offset (offset affected by the adjustment accuracy of the operator, the quality of the cutting mark, etc.) with the continuous cutting time, which will further exacerbate the offset and directly affect the appearance, even causing edge damage or back collapse of the LED chip. This is one of the abnormal problems that need to be solved and improved in LED chip cutting.

[0004] The patent CN107946284A discloses a kind of LED chip cutting path identification and its manufacturing method, which includes: by making cutting path identification on the GaP layer of LED chip to determine whether the knife mark is offset during cutting process, the manufacturing method of identification is wet etching, the identification part is protected by photoresist during etching process of chip, and the desired identification can be obtained after etching, which can be circular, square and other shapes.The patent indeed plays a certain identification role on the position of knife mark during cutting process, but the disadvantage of this method is that the identification part is not etched and drilled, but the part connected with the identification is etched and drilled, and GaP itself is prone to collapse during cutting process, plus the difference between etched and not etched surface, which can increase the damage to the blade and aggravate the cutting collapse, and the collapse is more serious, which can cause cutting offset. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides an LED chip cutting method for improving offset.

[0006] The technical solution of the present application is as follows:

[0007] An LED chip cutting method for improving offset, comprising the following steps:

[0008] (1) Gluing: coating photoresist on the surface of LED chip P face to form a mask film on the LED chip P face;

[0009] (2) Photolithography: exposing the LED chip P face after gluing to obtain identification cutting path and offset scale identification; the identification cutting path is a straight line from left to right through the entire LED chip P face; the offset scale identification is a vertical short line with vertical scale identification located on both sides of the edge of LED chip;

[0010] (3) Development: baking the LED chip after photolithography, and then developing and etching;

[0011] (4) Etching: cleaning and drying the LED chip after development, and then performing dry etching on the identification cutting path not covered by photoresist, with etching depth extending to GaP layer;

[0012] (5) Glue removal: chemically etching the LED chip after etching to remove the photoresist mask film covered on the surface of LED chip;

[0013] (6) Film pasting: pasting the LED chip P face without photoresist mask film downward on the blue film;

[0014] (7) Cutting: cutting the LED chip along the mark cutting path formed in step (2), and detecting and adjusting the position of the blade cutting mark in real time according to the offset scale mark formed in step (2) during the cutting process, so as to complete the cutting of the LED chip.

[0015] According to the application, preferably, in step (1), the specific process of the gluing is: the LED chip is adsorbed on the chuck of the glue spreading machine by vacuum adsorption, and the negative photoresist is applied on the P surface of the LED chip by using the glue spreading machine, the rotating speed of the chuck of the glue spreading machine is 3000-7000 r / min, and the gluing thickness is 5-15 μm.

[0016] According to the application, preferably, in step (2), the light intensity during the exposure is 5-10 μW / cm 2 , and the exposure time is 5-15 s. The mark pattern is formed, that is, the mark cutting path penetrating through the P surface of the LED chip from left to right and the offset scale mark located on both sides of the edge of the LED chip with vertical scale marks.

[0017] According to the application, preferably, in step (3), the baking temperature is 90-110 ℃, the baking time is 10-20 min, the concentration of the developing etching solution is 2-4.5%, and the etching time is 25-35 s.

[0018] Further preferably, the developing etching solution is a tetramethylammonium hydroxide solution.

[0019] According to the application, preferably, in step (4), the dry etching is ICP etching, and the specific process is: the gas introduced during the etching is Cl2 and BCl3, the gas content is 1-100 sccm, the chamber pressure of the etching machine is 1-10 Torr, the ICP RF power is 100-500 w, the BIAS RF power is 100-500 w, the tray temperature is 5-60 ℃, the depth of the ICP etching mark cutting path is 1.5-5 μm, the width of the mark cutting path is greater than the width of the blade cutting seam by 2 μm, the scale line width of the offset scale mark is the width of the LED chip, and the scale of the offset scale mark is spaced by 1-3 μm.

[0020] According to the application, preferably, in step (5), the specific process of the chemical etching is: the LED chip is first placed in an acetone solution, the acetone solution temperature is 45-52 ℃, and the time is 5-10 min, then the LED chip is placed in a 99.5% ethanol solution, the ethanol temperature is 70-73 ℃, and the time is 5-10 min, after air drying, the LED chip is placed in an ethanol solution, the ethanol temperature is 70-73 ℃, and the time is 5-10 min.

[0021] According to the application, preferably, in step (6), the temperature of the film is 50-60 DEG C, the model of the film is SPVS-224, and the size is (100-500m)*220mm.

[0022] According to the application, preferably, in step (7), the cutting is performed by using a sawing machine work platform, and the specific process is as follows: the cutting blade moves along the marked cutting path, the offset scale mark is used to confirm the offset position and make correction when cutting the edge of the LED chip; the penetration cutting blade height is 40-120 microns, the feed speed is 2-8 mm / s, and the operation speed is 10-40 mm / s.

[0023] The parts not described in the application are conventional technologies in the field.

[0024] The application has the following advantages:

[0025] 1. The application improves the conventional LED chip cutting process, adds the marked cutting path and offset scale mark, and cuts by making the blade move along the marked cutting path, and sets the offset scale mark on the path of the marked cutting path to visually adjust the data, which is equivalent to adding a ruler to make real-time offset measurement, effectively improves the problem of adjusting the offset by experience in the conventional LED chip cutting process, greatly improves the pass rate of chip cutting, and reduces the production cost.

[0026] 2. The application has simple process and convenient operation, focuses on visual data adjustment, does not need to add additional mechanical equipment, and is suitable for popularization and application in industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a chip surface schematic diagram of the marked cutting path and offset scale mark of the application.

[0028] Figure 2 It is an N surface schematic diagram of the chip obtained after cutting by the method of Example 1.

[0029] Figure 3 It is an N surface schematic diagram of the chip obtained after cutting by the method of Comparative Example 1.

[0030] In the figure, 1 is an LED chip, 2 is a marked cutting path, and 3 is an offset scale mark. DETAILED DESCRIPTION

[0031] The application will be described in detail below in combination with specific embodiments and the drawings of the specification, but is not limited thereto.

[0032] Example 1

[0033] An improved offset LED chip cutting method, comprising the following steps:

[0034] (1) Coating photoresist: the LED chip is vacuum adsorbed on the chuck of a spin coater, and the P surface of the LED chip before cutting is coated with negative photoresist by using the spin coater, the chuck rotation speed of the spin coater is 4000 r / min, and the coating thickness is 20-30 μm. A mask film is formed on the P surface of the LED chip.

[0035] (2) Photolithography: the LED chip coated with photoresist is placed on the platform of a photoetching machine, the light intensity is set to 6 μW / cm 2 , the exposure time is 10 s, and light exposure is performed to expose the mark cutting path and the offset scale mark on the negative photoresist; the mark cutting path is a straight line from left to right through the P surface of the entire LED chip; and the offset scale mark is a vertical short line with a vertical scale mark on both sides of the edge of the LED chip, which will be described in detail below. Figure 1

[0036] (3) Development: the LED chip after photoetching is placed in an oven, the temperature is set to 90 ℃, and the baking time is 10 min, and then the LED chip is placed in a 2.5% tetramethylammonium hydroxide solution for development and etching, the protected electrode and part of the light emitting area are protected, and the rest of the photoresist with changed properties is etched away.

[0037] (4) Dry etching: the LED chip after development is cleaned and dried, and the dried LED chip is etched by using an ICP etching machine on the places not covered by the photoresist, and the etching depth extends to the depth of the GaP layer; the gas for ICP etching machine etching is Cl2 and BCl3, the gas content is 10 sccm, the etching chamber pressure is 2 Torr, the ICP RF power is 200 w, the BIAS RF power is 150 w, the tray temperature is 30 ℃, the ICP etching depth is 2 μm, the width of the mark cutting path is 22 μm (20 μm + 2 μm), and the width of the scale line of the offset scale mark is the width of the LED chip size, and the scale of the offset scale mark is 1 μm apart.

[0038] (5) Photoresist removal: the LED chip after etching is chemically etched to remove the photoresist mask on the surface of the LED chip; the LED chip is placed in an acetone solution, the temperature is 50 ℃, and the time is 5 min, then the chip is placed in an ethanol solution, the ethanol temperature is 73 ℃, and the time is 5 min, after drying, the LED chip is placed in an ethanol solution, the ethanol temperature is 73 ℃, and the time is 5 min.

[0039] (6) Film pasting: the P surface of the LED chip after removing the photoresist mask is attached to a blue film with the P surface facing down, the film pasting temperature is 55 ℃, and the type of the blue film used is SPVS-224, 100 m*220 mm.​

[0040] (7) Cutting: Place the LED chip on the sawing machine work platform, set the cutting parameters, and then cut the LED chip along the mark cutting path formed in step (2). During the cutting process, the position of the blade cutting mark is detected and adjusted in real time according to the offset scale mark formed in step (2) to achieve visual data adjustment and improve the offset that occurs during cutting. The knife height for through cutting is 60 μm, the feed rate is 5 mm / s, and the working speed is 25 mm / s. When the offset scale mark at both ends of the chip is cut, the position where the cutting blade and the offset scale mark are perpendicular to each other is the distance from the center origin. For example, if it deviates upward by 2 μm, adjust the cutting position downward by 2 μm for calibration, and then continue cutting.

[0041] In this example, 100 chips were continuously cut, and the cumulative output of 41,000 K independent dies was obtained. 300 K independent dies were damaged or back collapsed due to cutting offset, and the yield was 99.27%. For details, see Figure 2 .

[0042] Example 2

[0043] An improved LED chip cutting method for offset, the steps are as described in Example 1, except that in step (4), the ICP etching depth is 1.5 μm for the surface GaP layer, the mark cutting path width is 20 μm (blade cutting seam width 18 μm + 2 μm), and the offset scale mark width at both ends is the LED chip size width. The scale of the offset scale mark is spaced at 1.5 μm.

[0044] In this example, 100 chips were continuously cut, and the cumulative output of 41,000 K independent dies was obtained. 280 K independent dies were damaged or back collapsed due to cutting offset, and the yield was 99.32%.

[0045] Example 3

[0046] An improved LED chip cutting method for offset, the steps are as described in Example 1, except that in step (7), when the offset scale mark at both ends of the chip is cut, the position where the cutting blade and the offset scale mark are perpendicular to each other is the distance from the center origin. For example, if it deviates upward by 1 μm or less, no calibration is needed to continue cutting.

[0047] In this example, 100 chips were continuously cut, and the cumulative output of 41,000 K independent dies was obtained. 315 K independent dies were damaged or back collapsed due to cutting offset, and the yield was 99.22%.

[0048] Comparative Example 1

[0049] The current industry mainly cuts the method, the normal process of the previous section (mainly refers to the photolithography operation, the conventional process operation is that the LED chip P surface is photoetched to form an electrode pattern, and no other surface is treated) is pasted after the film is placed on the sawing machine for cutting operation.

[0050] (1) Paste film: the P surface of the LED chip is attached to the blue film with the film temperature of 55℃, and the type of the blue film used is SPVS-224, 100m*220mm.

[0051] (2) Cutting: the LED chip is placed on the working platform of the sawing machine, and the cutting parameters are set for cutting operation, the knife height of the through cutting is 65μm, the feeding speed is 5mm / s, and the operation speed is 25mm / s; the cutting mark position is checked manually after every 100 cuts during the chip cutting operation, the checking mainly relies on the experience of the operator to judge the distance offset degree of the cutting mark position from the two side LED chips, and then it is determined whether to adjust the cutting mark position and how much to adjust, which has a large randomness.

[0052] Under the existing cutting method, 41000K independent dies are output after 100 chips are continuously cut (the number of particles is not affected), 750K independent dies appear back collapse, and the qualified rate is 98.17%, please see Figure 3 .

[0053] From Figures 1-2 , examples 1-3 and comparative example 1, the LED chip cutting method provided by the application improves the conventional chip cutting process, by adding the identification cutting path and the offset scale mark, the cutting blade is guided along the identification cutting path for cutting, and the offset scale mark is set on the identification cutting path for visual data adjustment, which is equivalent to adding a ruler for real-time offset measurement, effectively improving the problem of adjusting the offset by experience in the conventional LED chip cutting process, the number of chips with edge damage or back collapse is reduced from 750K to less than 330K, and the qualified rate is increased from 98.17% of the comparative example 1 to 99.27%, 99.32% and 99.21% of the examples 1-3, the range is 1.1-1.15%, the qualified rate is effectively improved, and the production cost is reduced.

Claims

1. A method for improving a cutting method of an offset LED chip, characterized by, The steps include the following: (1) Gluing: the P surface of the LED chip is coated with photoresist to form a mask film on the P surface of the LED chip; (2) Photoetching: the P surface of the LED chip after gluing is exposed to light to obtain a mark cutting path and a offset scale mark; the mark cutting path is a straight line from left to right through the entire P surface of the LED chip; the offset scale mark is a vertical short line with a vertical scale mark located on both sides of the edge of the LED chip; (3) Development: the LED chip after photoetching is baked and then developed and etched; (4) Etching: the LED chip after development is cleaned and dried, and then dry etching is performed on the mark cutting path not covered by the photoresist, and the etching depth extends to the GaP layer; Wherein, the scale line width of the offset scale mark is the width of the LED chip size, and the scale of the offset scale mark is spaced at 1-3 μm; (5) Glue removal: the LED chip after etching is chemically etched to remove the photoresist mask film on the surface of the LED chip; (6) Film pasting: the P surface of the LED chip after removing the photoresist mask film is attached to the blue film with the P surface facing down; (7) Cutting: the LED chip is cut along the mark cutting path formed in step (2), and the position of the blade cutting mark is detected and adjusted in real time according to the offset scale mark formed in step (2) during the cutting process, and the cutting of the LED chip is completed.

2. The offset-improved LED chip dicing method according to claim 1, wherein In step (1), the specific steps of gluing are as follows: the LED chip is vacuum adsorbed on the glue spreading machine suction disc, and the negative photoresist is spread on the P surface of the LED chip by using the glue spreading machine, the glue spreading machine suction disc rotates at a speed of 3000-7000 r / min, and the gluing thickness is 20000-50000 Å.

3. The offset-improved LED chip dicing method according to claim 1, wherein In step (2), the light intensity during exposure is 5-10 μW / cm², and the exposure time is 5-15 s.

4. The offset-improved LED chip dicing method according to claim 1, wherein In step (3), the baking temperature is 90-110 ℃, the baking time is 10-20 min, the concentration of the developing etching solution is 2-4.5%, and the etching time is 25-35 s.

5. The offset-improved LED chip dicing method according to claim 4, wherein The developing etching solution is a tetramethylammonium hydroxide solution.

6. The offset-improved LED chip dicing method according to claim 1, wherein In step (4), the dry etching is performed by using an ICP etching machine, and the specific process is as follows: Cl2 and BCl3 are introduced as the etching gas, the gas content is 1-100 sccm, the etching machine chamber pressure is 1-10 Torr, the ICP RF power is 100-500 w, the BIAS RF power is 100-500 w, the tray temperature is 5-60 ℃, the ICP etching mark cutting path depth is 1.5-5 μm, and the mark cutting path width is greater than the blade cutting seam width by 2 μm.

7. The offset-improved LED chip dicing method according to claim 1, wherein In step (5), the specific steps of chemical etching are as follows: the LED chip is first placed in an acetone solution, the acetone solution temperature is 45-52 ℃, and the time is 5-10 min; then the LED chip is placed in a 99.5% ethanol solution, the ethanol temperature is 70-73 ℃, and the time is 5-10 min; after drying, the LED chip is placed in an ethanol solution, the ethanol temperature is 70-73 ℃, and the time is 5-10 min.

8. The offset-improved LED chip dicing method according to claim 1, wherein In step (6), the temperature of the film is 50-60℃, the blue film model used is SPVS-224, and the size is (100-500m)*220mm.

9. The offset-improved LED chip dicing method according to claim 1, wherein In step (7), the cutting is performed by using a sawing machine work platform, and the specific process is as follows: the cutting blade travels in the marked cutting path, and when cutting the edge of the LED chip, the offset position of the cutting is confirmed and corrected by offsetting the scale mark corresponding to the scale position; the knife height for through cutting is 40-120μm, the feed speed is 2-8mm / s, and the operation speed is 10-40mm / s.

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