A method for cleaning wafer before evaporation

Abstract

The present invention relates to the field of semiconductor electronic technology, and specifically to a method for cleaning a wafer before evaporation, comprising the following steps: Step 2: a plasma glue machine performs two ionization processes on its cavity; Step 3: the semi-finished wafer obtained in Step 2 is placed in ionized water, and nitrogen is filled into the ionized water to cause bubbles in the ionized water; Step 4: the semi-finished wafer obtained in Step 3 is placed in a cleaning tank, and then ionized water is flushed twice at different rates, and then three times with different average powers of spin-drying. The beneficial effect of the present invention is that the multiple ionizations, ionized water flushings, and spin-dryings of different powers provided by the present invention can enable polymers to be removed by a removal process with a more appropriate power, and the multiple processes with different powers cooperate to more completely remove impurities on the surface of the semi-finished wafer, thereby improving the cleanliness of the surface of the semi-finished wafer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor electronic technology, in particular to a method for cleaning a wafer before evaporation. Background Art

[0002] LED chip is a solid-state semiconductor device whose main function is to convert electrical energy into light energy.

[0003] An LED chip consists of two main components: a P-type semiconductor with positively charged holes inside, and an N-type semiconductor with a negative charge. The P-type and N-type semiconductors are connected to form a PN junction. When current flows through the chip, negative electrons are pushed from the N-type semiconductor to the holes in the P-type semiconductor. The electrons and holes are converted into photons, emitting energy.

[0004] In the LED wafer process, P-type and N-type semiconductors are electrically connected to the outside of the wafer via deposited metal electrodes, facilitating the application of current. The adhesion of the deposited electrodes determines their contact resistance and reliability. If impurities remain on the surface of the semi-finished wafer before metal electrode deposition, they will be trapped beneath the electrodes after deposition, increasing the contact resistance and voltage of the finished wafer. Furthermore, during wire bonding, the electrodes can easily become detached, causing quality issues. Therefore, it is essential to develop a method to improve electrode adhesion by cleaning the semi-finished wafer surface before deposition. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for cleaning a wafer before evaporation, so as to reduce the impurities in the P-type semiconductor holes and the impurities in the N-type semiconductor holes as much as possible.

[0006] In order to solve the above technical problems, the present invention adopts a technical solution: a method for cleaning a wafer before evaporation, comprising the following steps:

[0007] Step 1: After covering the semi-finished wafer with photoresist, a photolithography process is used to open P-type semiconductor holes and N-type semiconductor holes in the photoresist;

[0008] Step 2: placing the semi-finished wafer obtained in step 1 into the cavity of a plasma glue machine, and causing the plasma glue machine to perform two ionization processes on the cavity, with the power of the second ionization process being lower than the power of the first ionization process;

[0009] Step 3: Place the semi-finished wafer obtained in step 2 into deionized water, and fill the deionized water with nitrogen to cause bubbles to form in the deionized water;

[0010] Step 4: Place the semi-finished wafer obtained in step 3 into the cleaning tank, rinse with ionized water twice at different rates, and then spin dry three times at different average powers.

[0011] The present invention has the beneficial effect of: in the photoresist residue removal process, such as the ionization process, the deionized water flushing process, and the spin-drying process, the higher the power, the better the effect of breaking down the adhesion of the polymer at the inner corners of the P-type semiconductor holes and the N-type semiconductor holes. Moreover, the adhesion of the polymer at the inner corners of multiple P-type semiconductor holes or multiple N-type semiconductor holes to the semi-finished wafer varies.

[0012] The multiple ionizations, ionized water flushing and drying at different powers provided by the present invention can enable the polymer to be removed by a removal process with a more appropriate power, and the multiple processes with different powers have a coordinated effect, so that impurities on the surface of the semi-finished wafer are removed more completely, thereby improving the cleanliness of the surface of the semi-finished wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the overall structure of a wafer according to a specific embodiment of the present invention;

[0014] Figure 2 A schematic diagram of a portion of the structure of a semi-finished wafer according to a specific embodiment of the present invention;

[0015] Figure 3 A schematic diagram of a portion of the structure of a semi-finished wafer according to a specific embodiment of the present invention;

[0016] Description of labels:

[0017] 1. Sapphire substrate; 2. N-type semiconductor layer;

[0018] 3. Multiple quantum well layer; 4. P-type semiconductor layer;

[0019] 5. Conductive layer ITO; 6. Photoresist; 7. P-type semiconductor hole;

[0020] 8. Photoresist base film; 9. Polymer. DETAILED DESCRIPTION

[0021] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.

[0022] Please refer to Figure 1-3 A method for cleaning a wafer before evaporation, comprising the following steps:

[0023] Step 1: After covering the semi-finished wafer with photoresist 6, a photolithography process is used to open a P-type semiconductor hole 7 and an N-type semiconductor hole on the photoresist;

[0024] Step 2: placing the semi-finished wafer obtained in step 1 into the cavity of a plasma glue machine, and causing the plasma glue machine to perform two ionization processes on the cavity, with the power of the second ionization process being lower than the power of the first ionization process;

[0025] Step 3: Place the semi-finished wafer obtained in step 2 into deionized water, and fill the deionized water with nitrogen to cause bubbles to form in the deionized water;

[0026] Step 4: Place the semi-finished wafer obtained in step 3 into the cleaning tank, rinse with ionized water twice at different rates, and then spin dry three times at different average powers.

[0027] As can be seen from the above description, the beneficial effect of the present invention is that: in the method for cleaning the wafer before evaporation provided by the present invention, the impurities on the surface of the semi-finished wafer mainly refer to the photoresist bottom film 8 in the P-type semiconductor holes and the N-type semiconductor holes. It is usually difficult to avoid leaving a photoresist bottom film on the photoresist 6 after the traditional photolithography process.

[0028] During the two ionization processes at different powers on the semi-finished wafer in step 2, the oxygen ions generated rapidly oxidize and remove the photoresist film. The first ionization process with higher power effectively removes the photoresist film 8 in the middle of the P-type semiconductor hole 7 and the N-type semiconductor hole. However, it has difficulty in promptly removing the photoresist film 8 at the inner corners of the P-type semiconductor hole and the N-type semiconductor hole, causing polymer 9 to accumulate at these inner corners. The second ionization process with lower power can reduce the accumulation of polymer 9 at the inner corners of the P-type semiconductor hole and the N-type semiconductor hole.

[0029] The method of step three is to better wet the polymer at the negative corners of the P-type semiconductor hole and the N-type semiconductor hole, so that the polymer is easier to fall off.

[0030] In step 4, multiple flushing with ionized water at different rates and multiple drying with different powers can fully clean the P-type semiconductor holes 7 and the N-type semiconductor holes, and flush and remove the polymer 9 at the corners of the P-type semiconductor holes and the N-type semiconductor holes.

[0031] During the photoresist residue removal process, such as the ionization, ionized water flushing, and spin drying steps, higher power does not necessarily mean a better effect on breaking down the adhesion of polymer at the inner corners of P-type and N-type semiconductor holes. Furthermore, the adhesion of polymer at the inner corners of multiple P-type or N-type semiconductor holes to the semi-finished wafer may vary.

[0032] The multiple ionizations, ionized water flushing and drying at different powers provided by the present invention can enable the polymer to be removed by a removal process with a more appropriate power, and the multiple processes with different powers have a coordinated effect, so that impurities on the surface of the semi-finished wafer are removed more completely, thereby improving the cleanliness of the surface of the semi-finished wafer.

[0033] Furthermore, in the step 2, a scavenging process is provided before and after the ionization process; the scavenging process is to fill oxygen into the cavity of the plasma glue machine to replace the gas in the cavity of the original plasma glue machine.

[0034] As can be seen from the above description, the purge process takes away the photoresist base film that is ionized and detached, and maintains the oxygen content in the cavity, so that the cleaning effect of ionization can be maintained to a certain extent.

[0035] Furthermore, in the step 2, "placing the semi-finished wafer obtained in step 1 into the cavity of the plasma glue machine" is specifically: placing the semi-finished wafer obtained in step 1 on the turntable of the plasma glue machine; in both ionization processes, oxygen is filled into the cavity of the plasma glue machine.

[0036] As can be seen from the above description, the above arrangement can maintain the oxygen content in the cavity, so that the ionization cleaning effect can be maintained to a certain extent.

[0037] Furthermore, the step 2 is specifically as follows: (1) setting the glue turntable to 10 r / min (revolutions per minute), and after the cavity vacuum reaches 40 mTorr, introducing 20 sccm (milliliters per minute) of oxygen into the cavity to perform oxygen pre-purge of the cavity, maintaining the pressure for 30 seconds, thereby increasing the oxygen content in the cavity and reducing residual impurities in the cavity;

[0038] (2) The glue turntable is set to 10 r / min, the oxygen flux is maintained at 20 sccm, the RF power is increased to 130 W, and the ionization operation is maintained for 400 s, so that the oxygen generates ions to quickly oxidize the bottom film photoresist, and the material is extracted from the cavity by vacuum;

[0039] (3) Set the glue turntable to 10 r / min, maintain an oxygen flux of 20 sccm, lower the RF power to 0 W, maintain for 30 s, and remove free impurities through oxygen purge;

[0040] (4) Adjust the photoresist turntable speed to 5 r / min and the oxygen flux to 10 sccm, adjust the RF power to 100 W, and maintain the ionization operation for 400 s. The RF power is adjusted from 130 W in the first section to 100 W, the turntable speed is reduced by 5 r / min, and the oxygen flux is 10 sccm. This can reduce the polymer accumulation caused by the inability to remove the photoresist on the sidewalls in time due to the rapid ionization under high power, especially the impurity residues at the edge of the small electrode hole structure;

[0041] (5) Maintaining the turntable speed at 5 r / min and the oxygen flux at 10 sccm, the RF power was lowered to 0 W and maintained for 30 s, and free impurities were removed by oxygen purge.

[0042] Furthermore, in the step 4, during the ion water flushing process, the semi-finished wafers are rotated on a spin dryer in the cleaning tank.

[0043] As can be seen from the above description, during the rotation of the semi-finished wafer in the spin dryer, the multiple P-type semiconductor holes and N-type semiconductor holes thereon can be evenly flushed by ionized water, thereby improving the cleanliness of the P-type semiconductor holes and N-type semiconductor holes.

[0044] Furthermore, in step 4, the two flushings with ionized water include a first flushing with ionized water and a second flushing with ionized water, and the rotation speed of the spin dryer during the first flushing with ionized water is lower than the rotation speed of the spin dryer during the second flushing with ionized water.

[0045] As can be seen from the above description, the above arrangement provides a reasonable sequence of the two ionized water flushing processes.

[0046] Furthermore, the flow rate of the ionized water in the first flush is lower than the flow rate of the ionized water in the second flush.

[0047] As can be seen from the above description, the above configuration provides a variation in the ionized water flow rate during the ionized water flushing process with excellent cleaning effect.

[0048] Furthermore, in step 4, during the drying process, the air blowing valve of the cleaning tank is opened.

[0049] From the above description, it can be seen that opening the air blowing valve can better dry the semi-finished wafers.

[0050] Furthermore, the step 4 is specifically as follows: (1) the spin dryer is set to rotate at 150 r / min, the ionized water flushing is maintained for 150 s, and the ionized water is sprayed into the porous structure under slow flushing to ensure sufficient wetting of the wafer, especially the deep pore structure under the small electrode;

[0051] (2) The spin dryer is set to a speed of 800 r / min and the flushing is maintained for 50 s. The water in the pore structure is replaced by medium-speed ionized water flushing to initially remove the polymer;

[0052] (3) Set the spin dryer to 800 rpm, turn off the water, open the air blow valve, and keep blowing for 60 seconds to remove most of the moisture on the wafer surface;

[0053] (4) The spin dryer is set to a speed of 2000r / min-1000r / min, the temperature in the chamber is set to 75℃, the flushing is turned off, the air blowing valve is opened, and the speed is increased from 800r / min to 2000r / min within 4s and maintained for 360s. The speed is reduced from 2000r / min to 1000r / min within 4s and maintained for 240s. The speed is increased from 1000r / min to 2000r / min within 4s and maintained for 600s. The speed is reduced from 2000r / min to 1000r / min within 4s and maintained for 10s. This process uses the change of high and low centrifugal rates to fully remove the residues in the porous structure and ensure the surface is dry;

[0054] (5) Reduce the spin dryer speed to 500 r / min, turn off the flushing, open the air blow valve, maintain 75 ° C, maintain for 50 seconds, and completely remove all moisture on the wafer surface and pore structure.

[0055] The application background of the method for cleaning a wafer before evaporation provided by the present invention is when the surface of a semi-finished wafer needs to be cleaner to improve the adhesion of the evaporated motor.

[0056] Example 1

[0057] Please refer to Figure 1-3 A method for cleaning a wafer before evaporation, comprising the following steps:

[0058] Step 1: After covering the semi-finished wafer with a photoresist 6, a photolithography process is used to open a P-type semiconductor hole 4 and an N-type semiconductor hole on the photoresist 6;

[0059] Specifically, a gallium nitride-based N-type semiconductor layer 2, a multi-quantum well layer 3, and a P-type semiconductor layer 4 are grown on a sapphire substrate 1 using a metal organic chemical vapor deposition method; a current blocking layer is evaporated on the gallium nitride substrate using a plasma enhanced chemical vapor deposition method; and a transparent conductive layer ITO 5 is evaporated using a sputtering method.

[0060] Apply photoresist 6, and use exposure to transfer the pattern of the photoresist mask to replicate the P-type semiconductor hole 7 and the N-type semiconductor hole;

[0061] A developer such as tetramethylammonium hydroxide is used to remove most of the photoresist in the P-type semiconductor holes and the N-type semiconductor holes, thereby revealing the holes.

[0062] Step 2: placing the semi-finished wafer obtained in step 1 into the cavity of a plasma glue machine, and causing the plasma glue machine to perform two ionization processes on the cavity, with the power of the second ionization process being lower than the power of the first ionization process;

[0063] Specifically: (1) Set the glue turntable to 10 r / min (revolutions per minute), and after the chamber vacuum reaches 40 mTorr, introduce 20 sccm (milliliters per minute) of oxygen into the chamber to perform oxygen pre-purge of the chamber, maintaining it for 30 s to increase the oxygen content in the chamber and reduce the residual gas in the chamber;

[0064] (2) The glue turntable is set to 10 r / min, the oxygen flux is maintained at 20 sccm, the RF power is increased to 130 W, and the ionization operation is maintained for 400 s, so that the oxygen generates ions to quickly oxidize the bottom film photoresist, and the material is extracted from the cavity by vacuum;

[0065] (3) Set the glue turntable to 10 r / min, maintain an oxygen flux of 20 sccm, lower the RF power to 0 W, maintain for 30 s, and remove free impurities through oxygen purge;

[0066] (4) Adjust the photoresist turntable speed to 5 r / min and the oxygen flux to 10 sccm, adjust the RF power to 100 W, and maintain the ionization operation for 400 s. The RF power is adjusted from 130 W in the first section to 100 W, the turntable speed is reduced by 5 r / min, and the oxygen flux is 10 sccm. This can reduce the polymer accumulation caused by the inability to remove the photoresist on the sidewalls in time due to the rapid ionization under high power, especially the impurity residues at the edge of the small electrode hole structure;

[0067] (5) Maintaining the turntable speed at 5 r / min and the oxygen flux at 10 sccm, the RF power was lowered to 0 W and maintained for 30 s, and free impurities were removed by oxygen purge.

[0068] Step 3: Place the semi-finished wafer obtained in step 2 into deionized water, and fill the deionized water with nitrogen to cause bubbles to form in the deionized water;

[0069] Specifically, the wafer is placed in the cleaning tank, and the upper and lower synchronous water supply mode is set. Ionized water is flushed from the top to the wafer and from the bottom to the wafer and fills the cleaning tank. The input is 3kg / cm 2 The high-pressure nitrogen was bubbled for 120 seconds and then discharged. The upper and lower water supply and bubbling methods were used to enhance the infiltration of the deep pore structure under the small electrode.

[0070] Step 4: Place the semi-finished wafer obtained in step 3 into the cleaning tank, rinse with ionized water twice at different rates, and then spin dry three times at different average powers.

[0071] Specifically: (1) the spin dryer is set to a speed of 150 r / min, the ionized water flushing is maintained for 150 s, and the ionized water is sprayed into the porous structure under slow flushing to ensure sufficient infiltration of the wafer, especially the infiltration of the deep pore structure under the small electrode;

[0072] (2) The spin dryer is set to a speed of 800 r / min and the flushing is maintained for 50 s. The water in the pore structure is replaced by medium-speed ionized water flushing to initially remove the polymer;

[0073] (3) Set the spin dryer to 800 rpm, turn off the water, open the air blow valve, and keep blowing for 60 seconds to remove most of the moisture on the wafer surface;

[0074] (4) The spin dryer is set to a speed of 2000r / min-1000r / min, the temperature in the chamber is set to 75℃, the flushing is turned off, the air blowing valve is opened, and the speed is increased from 800r / min to 2000r / min within 4s and maintained for 360s. The speed is reduced from 2000r / min to 1000r / min within 4s and maintained for 240s. The speed is increased from 1000r / min to 2000r / min within 4s and maintained for 600s. The speed is reduced from 2000r / min to 1000r / min within 4s and maintained for 10s. This process uses the change of high and low centrifugal rates to fully remove the residues in the porous structure and ensure the surface is dry;

[0075] (5) Reduce the spin dryer speed to 500 r / min, turn off the flushing, open the air blow valve, maintain 75 ° C, maintain for 50 seconds, and completely remove all moisture on the wafer surface and pore structure.

[0076] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for cleaning a wafer before evaporation, characterized in that: The steps include: Step 1: After covering the semi-finished wafer with photoresist, a photolithography process is used to open P-type semiconductor holes and N-type semiconductor holes in the photoresist; Step 2: placing the semi-finished wafer obtained in step 1 into the cavity of a plasma glue machine, and causing the plasma glue machine to perform two ionization processes on the cavity, with the power of the second ionization process being lower than the power of the first ionization process; The second step is specifically as follows: (1) setting the glue turntable to 10 r / min (revolutions per minute), and after the chamber vacuum reaches 40 mTorr, introducing 20 sccm (milliliters per minute) of oxygen into the chamber to perform oxygen pre-purge of the chamber, and maintaining the oxygen pre-purge for 30 seconds; (2) Set the glue turntable to 10 r / min, maintain an oxygen flux of 20 sccm, increase the RF power to 130 W, and maintain the ionization operation for 400 s; (3) Set the glue turntable to 10 r / min, maintain an oxygen flux of 20 sccm, and lower the RF power to 0 W for 30 s; (4) Adjust the speed of the glue turntable to 5 r / min and the oxygen flux to 10 sccm, adjust the RF power to 100 W, maintain the ionization operation for 400 s, adjust the RF power from 130 W in the first section to 100 W, reduce the turntable speed by 5 r / min, and the oxygen flux to 10 sccm; (5) Maintain the turntable speed at 5 r / min and the oxygen flux at 10 sccm, lower the RF power to 0 W, and maintain for 30 s; Step 3: Place the semi-finished wafer obtained in step 2 into deionized water, and fill the deionized water with nitrogen to cause bubbles to form in the deionized water; Step 4: Place the semi-finished wafer obtained in step 3 into the cleaning tank, rinse with ionized water twice at different rates, and then spin dry three times at different average powers.

2. The method for cleaning a wafer before evaporation according to claim 1, wherein: In the step 2, a scavenging process is provided before and after the ionization process respectively; the scavenging process is: filling oxygen into the cavity of the plasma glue machine to replace the gas in the cavity of the original plasma glue machine.

3. The method for cleaning a wafer before evaporation according to claim 1, wherein: In the step 2, "placing the semi-finished wafer obtained in step 1 into the cavity of the plasma glue machine" specifically means: placing the semi-finished wafer obtained in step 1 on the turntable of the plasma glue machine; and filling oxygen into the cavity of the plasma glue machine in both ionization processes.

4. The method for cleaning a wafer before evaporation according to claim 1, wherein: The step 3 is specifically as follows: put the semi-finished wafer obtained in step 2 into the cleaning tank, set the upper and lower synchronous water supply mode, and flush the semi-finished wafer from the top and from the bottom to the semi-finished wafer and fill the cleaning tank, using the input 3kg / cm 2 Nitrogen gas was bubbled at 1000 psi for 120 s.

5. The method for cleaning a wafer before evaporation according to claim 1, wherein: In the fourth step, during the ion water flushing process, the semi-finished wafers are placed on a spin dryer in the cleaning tank for rotation.

6. The method for cleaning a wafer before evaporation according to claim 5, characterized in that: In the step 4, the two flushings with ionized water include a first flushing with ionized water and a second flushing with ionized water, and the rotation speed of the spin dryer during the first flushing with ionized water is lower than the rotation speed of the spin dryer during the second flushing with ionized water.

7. The method for cleaning a wafer before evaporation according to claim 6, wherein: In the step 4, the flow rate of the ionized water in the first flush is lower than the flow rate of the ionized water in the second flush.

8. The method for cleaning a wafer before evaporation according to claim 1, wherein: In the step 4, during the drying process, the air blowing valve of the cleaning tank is opened.

9. The method for cleaning a wafer before evaporation according to claim 1, wherein: The step 4 is specifically as follows: (1) the spin dryer is set to rotate at 150 r / min, and the deionized water is slowly flushed for 150 seconds; (2) The spin dryer was set to a speed of 800 r / min and the deionized water was rinsed for 50 s; (3) Set the spin dryer speed to 800 r / min, turn off the flushing, open the air blowing valve, and maintain the air blowing for 60 seconds; (4) The spin dryer was set to a speed of 2000 r / min-1000 r / min, the chamber temperature was set to 75°C, the flushing was turned off, the air blow valve was opened, and the speed was increased from 800 r / min to 2000 r / min within 4 seconds and maintained for 360 seconds; decreased from 2000 r / min to 1000 r / min within 4 seconds and maintained for 240 seconds; increased from 1000 r / min to 2000 r / min within 4 seconds and maintained for 600 seconds; decreased from 2000 r / min to 1000 r / min within 4 seconds and maintained for 10 seconds; (5) Reduce the spin dryer speed to 500 r / min, turn off the flushing, open the air blow valve, maintain 75°C, and maintain for 50 seconds.

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