KR20090119144A - Wafer back grind system - Google Patents

Abstract

PURPOSE: A wafer back grinding apparatus is provided to increase process efficiency by removing non-operation time of a device due to cleaning solution exhaust. CONSTITUTION: A wafer back grinding apparatus includes a vacuum part, a storage chamber, a level detecting part, an exhaust pump, and a pump driving part. The vacuum part(200) supplies vacuum to a chuck table(12), and absorbs a cleaning solution. The storage chamber(100) stores the cleaning solution absorbed through the vacuum part. The level detecting part(300) detects a level of the cleaning solution stored to the storage chamber. The exhaust pump(500) exhausts the cleaning solution stored to the storage chamber. The pump driving part(400) supplies a driving power to the exhaust pump according to an output signal of the level detecting part.

Description

Wafer back grinding device {Wafer back grind system}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer back grind apparatus, and more particularly, to vacuum cleaning liquid sprayed onto a chuck table in a wafer back grind apparatus in a chamber, and storing the cleaning liquid in a chamber. It relates to a device for discharging to the outside.

In general, semiconductor packages are completed through a multi-step process. That is, the photo, etching, diffusion, and thin film processes are repeatedly performed several times, followed by a FAB (fabrication) process for forming an electric circuit pattern on the wafer, and then the electrical characteristics and operating states of each chip constituting the wafer. It goes through an EDS (Electric Die Sorting) process that tests and sorts good and bad parts. In addition, the chip, which is determined to be good through the EDS process, is cut into chips and then assembled into a completed semiconductor package. On the other hand, wafers in the FAB process and the EDS process need to maintain some strength to withstand the impact and external force applied during the handling process, and must have a sufficient thickness for this. On the other hand, a thinner wafer is advantageous for miniaturization and high integration of the completed semiconductor package after cutting in chip units as described above.

Therefore, during FAB process and EDS process, the thickness of the wafer is generally maintained at about 750 μm, and then the back side of the wafer, that is, the surface opposite to the surface on which the electric circuit pattern is formed, is polished before the wafer is cut into chips for the assembly process. Is reduced to approximately 280 μm.

FIG. 1 is a schematic diagram illustrating a structure for discharging and cleaning a cleaning liquid used in a polishing process in a conventional wafer back surface polishing apparatus and then discharging the cleaning liquid to the outside.

Conventional wafer back surface polishing apparatus includes a chuck table 12 on which a wafer is placed, a vacuum chamber 14 storing a vacuum sucked cleaning liquid from the chuck table 12, and a main vacuum pump for vacuuming the vacuum chamber 14. In operation 16, the level of the cleaning liquid stored in the vacuum chamber 14 is sensed in stages (LOW, HIGH, and OVERFLOW) so that the cleaning liquid of the plurality of level sensing sensors 18a, 18b, and 18c and the vacuum chamber 14 is externally detected. And a discharge pump 20 for discharging. And a vacuum valve 22, an exhaust valve 24, and a discharge valve 26.

The operation of the wafer backside polishing apparatus of FIG. 1 will be briefly described as follows.

The vacuum chamber 14 is vacuumed by the main vacuum pump 16 while the wafer is being polished. At this time, the vacuum valve 22 is in an open state.

Since the vacuum chamber 14 is in a vacuum state, the cleaning liquid sprayed on the wafer for wafer polishing is vacuum sucked into the vacuum chamber 14 through the pores (not shown) of the chuck table 12 by the pressure difference, and stored.

As the cleaning liquid sucked in the vacuum is collected in the vacuum chamber 14 and the water level is gradually raised to a predetermined high level, the level sensor 18b detects this. When a detection signal is generated from the level sensor 18b, the wafer backside polishing apparatus drives the discharge pump 20 to forcibly discharge the cleaning liquid stored in the vacuum chamber 14 to the outside.

At this time, since the cleaning liquid is not normally discharged even when the discharge pump 20 is driven while the vacuum chamber 14 is in a vacuum state, the vacuum valve 22 is first closed, and the exhaust valve 24 and the discharge valve 26 are opened to open the vacuum. The vacuum in the chamber 14 is released.

However, when the pressure in the vacuum chamber 14 fails to maintain the vacuum state, the wafer placed on the chuck table cannot be sucked in vacuum, and thus the polishing operation cannot be continued in this state.

Therefore, the conventional wafer back surface polishing apparatus must inevitably stop the polishing operation for a predetermined time (about 2 to 3 minutes) for discharging the cleaning liquid stored in the vacuum chamber 14, that is, while the vacuum chamber 14 is not in a vacuum state. There is a problem of having downtime. Moreover, this non-operation time occurs every time the cleaning liquid is discharged, which causes a reduction in the efficiency of the overall process.

The present invention aims to increase process efficiency by eliminating equipment downtime due to cleaning liquid discharge during wafer backside polishing.

The wafer backside polishing apparatus of the present invention includes a vacuum unit for supplying a vacuum to the chuck table and sucking the cleaning liquid; A storage chamber storing the cleaning liquid sucked through the vacuum unit; A level sensor detecting a level of the cleaning liquid stored in the storage chamber; A discharge pump for discharging the cleaning liquid stored in the storage chamber; And a pump driver supplying driving power to the discharge pump according to the output signal of the water level detector.

In the present invention, the vacuum unit is an air supply unit for injecting air; And a vacuum valve for supplying a vacuum to the chuck table by adjusting a flow of air injected from the air supply unit. At this time, the vacuum valve vacuum- suctions the cleaning liquid of the chuck table by using the vacuum supplied to the chuck table and supplies it to the storage chamber. As the vacuum valve, a Venturi valve is used.

The level sensor may include a first level sensor configured to output a first detection signal when the level of the cleaning liquid reaches a preset first level; And a second water level sensor configured to output a second detection signal when the cleaning liquid reaches a preset second level. As such a water level sensor, a capacitive proximity sensor is used.

In the present invention, the pump driving unit is a self-holding circuit for supplying driving power to the discharge pump when the second detection signal is generated and performs a self-holding function according to the first detection signal. The pump driving unit may include a first connection terminal connected to an output terminal of the first water level detection sensor and receiving the first detection signal; A second connection terminal connected to a power input terminal of the discharge pump; A first relay switch connected to an output terminal of the second water level sensor and connected to the first connection terminal when the first detection signal or the second detection signal is applied; And a second relay switch connected to the driving power source and relayed to the first relay switch to be connected to the second connection terminal when the first relay switch is connected to the first connection terminal.

The wafer backside polishing apparatus of the present invention further includes an exhaust portion for discharging the air introduced into the storage chamber through the vacuum portion to the outside, and the exhaust portion is formed of an open valve which always opens the inside of the storage chamber to the outside.

The present invention improves the overall process efficiency by improving the structure of the wafer backside polishing apparatus so that the polishing apparatus can be continuously driven while the cleaning liquid stored in the chamber is discharged.

In addition, the preferred embodiment of the present invention for the purpose of illustration, those skilled in the art will be able to various modifications, changes, substitutions and additions through the spirit and scope of the appended claims, such modifications and changes are the following claims It should be seen as belonging to a range.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing the configuration of a wafer back surface polishing apparatus according to the present invention.

The wafer back surface polishing apparatus of the present invention includes a storage chamber 100, a vacuum unit 200, a water level detecting unit 300, a pump driving unit 400, a discharge pump 500, and an exhaust unit 600.

The storage chamber 100 temporarily stores the cleaning liquid sucked in the vacuum through the vacuum unit 300. Unlike the vacuum chamber 14 of FIG. 1, the storage chamber 100 of the present invention does not maintain its interior in a vacuum state during a polishing operation.

The vacuum unit 200 directly supplies the vacuum to the chuck table 12 so that the wafer placed on the chuck table 12 is vacuum-adsorbed to the chuck table 12, and the cleaning liquid on the chuck table 12 is sucked under vacuum to store the vacuum chamber. 100). That is, the vacuum unit 200 of the present invention supplies the vacuum directly to the chuck table 12 rather than supplying a vacuum to the chuck table 12 by making the interior of the storage chamber 100 in a vacuum state as in the related art. It is driven independently of the discharge pump 500 to continuously apply a vacuum to the chuck table 12 even while the discharge pump 500 is driven, thereby continuing the polishing operation while discharging the cleaning liquid stored in the storage chamber 100. It allows you to do it. The vacuum unit 200 is a venturi for supplying a vacuum to the chuck table 12 by using the air supply unit 210 for injecting high pressure air and the high pressure air injected from the air supply unit 210. Valve 220. At this time, the air supply unit 210 continuously injects air to the venturi valve 220 while the cleaning liquid of the storage chamber 100 is discharged. In addition, the venturi valve 220 adjusts the flow of air injected from the air supply unit 210 to form a vacuum according to the Pascal principle, and then supplies it to the chuck table 120 so that the wafer placed on the chuck table 12 is vacuumed. Adsorption and fixation may be performed, and the cleaning liquid used in the polishing process may be sucked under vacuum to be stored in the storage chamber 100. The venturi valve 220 forms a vacuum pressure of up to -88 Kpa when the air pressure supplied from the air supply unit 210 is 0.5 Mpa or more, and when the vacuum pressure is more than -80 Kpa, the suction flow rate is 12 L / Min ( ANR) level.

The level detecting unit 300 detects the level of the cleaning liquid stored in the storage chamber 100 by levels LS1, LS2, and LS3, and outputs detection signals indicating the current level of the cleaning liquid. , 300b, 300c). At this time, the water level sensor 300a, 300b, 300c of the present invention detects the change in capacitance due to the movement and separation of the charge in the object existing in the electric field by using the electric field generated by the voltage applied to the electrode Capacitive proximity sensors are used. Such capacitive proximity sensors 00a, 300b, and 300c are preferably installed within 10 mm from the surface of the storage chamber 100. Since the capacitive proximity sensor itself is a general one, a detailed description thereof will be omitted. In addition, the water level LS1, LS2, LS3 of the cleaning liquid detected by the water level detection sensors 300a, 300b, and 300c is the same as in FIG. 1.

The pump driver 400 selectively drives the discharge pump 600 according to the detection signals generated by the water level detector 300 so that the cleaning liquid is not stored above the predetermined predetermined level LS2 in the storage chamber 100. do. That is, the pump driving unit 400 supplies a driving power to the discharge pump 500 when the cleaning liquid stored in the storage chamber 100 reaches the high level LS2 and a detection signal is generated from the water level detection sensor 300b. Drive 500. At this time, the pump driving unit 400 operates as a self-holding circuit to continuously supply driving power to the discharge pump 500 until the level of the cleaning liquid is lowered below the low level LS1.

The discharge pump 500 is driven according to the driving power supplied from the pump driver 400 to forcibly discharge the cleaning liquid stored in the storage chamber 100 to the outside of the storage chamber 100.

The exhaust part 600 allows the air introduced into the storage chamber 100 from the vacuum part 200 to be discharged to the outside of the chamber 100. That is, the exhaust unit 600 is composed of an open valve that always opens the inside of the storage chamber 100 to the outside so that the inside of the storage chamber 100 is always open to the air without being sealed.

3 is a flowchart illustrating the operation of the wafer back surface polishing apparatus according to the present invention described above.

While the apparatus is running and the wafer backside is polished, the air supply 210 ejects high pressure air to the venturi valve 220 (step 210).

The high pressure air injected from the air supply unit 210 forms a vacuum while passing through the venturi valve 220 of FIG. 4 to supply a vacuum to the chuck table 12 (step 220).

In other words, according to Pascal's principle, when the air introduced through the input stage suddenly passes through the narrow tube, the air flow suddenly increases and the pressure of the narrow tube is drastically lowered, so that the fluid is sucked in from the bottom. At this time, when the pressure of the air flowing into the input stage is high, the pressure of the narrow tube is almost close to the vacuum state. The vacuum unit 200 of the present invention supplies a vacuum to the chuck table 12 using the Pascal principle.

According to this principle, the vacuum is supplied to the chuck table 12 so that the wafer is vacuum-adsorbed to the chuck table 12, and the cleaning liquid used in the polishing process is vacuum sucked by the venturi valve 220 and stored in the storage chamber 100. .

When the amount of the cleaning liquid stored in the storage chamber 100 increases in this way and the level of the cleaning liquid reaches the low level LS1 (step 230), the first water level sensor 300a detects this to detect the first detection signal. (Step 240).

The first detection signal is applied to the b terminal of the pump driver 400. The first detection signal is continuously generated until the level of the cleaning liquid is lowered below the low level LS1.

When the polishing process continues and the cleaning liquid sucked through the chuck table 12 gradually increases, and the level of the cleaning liquid stored in the storage chamber 100 reaches the high level LS2 (step 250), the second water level detection sensor 300b ) Detects this and generates a second detection signal (step 260).

The second detection signal is applied to the relay switch RS1 of the pump driving unit 400 and is continuously generated until the level of the cleaning liquid is lowered below the high level LS2.

When the second detection signal is generated, the relay switch RS1 of the pump driver 400 is switched from a connection terminal to b connection terminal. In addition, the relay switch RS2 is also relayed with the relay switch RS1 to switch from the c connection terminal to the d connection terminal. That is, the relay switch RS1 is connected to the a connection terminal while the detection signal is not applied, and is switched to the b connection terminal when the detection signal is applied, and is connected to the b connection terminal. At this time, the relay switch RS2 is relayed to the relay switch RS1 and switched in the same direction, that is, from the c connection terminal to the d connection terminal.

When the relay switch RS2 is connected to the d connection terminal by the relay driving, the driving power source AC 110V connected to the relay switch RS2 is connected to the power input terminal of the discharge pump 500 through the relay switch RS2 and the d connection terminal. The discharge pump 500 is driven by being applied to. Accordingly, the cleaning liquid stored in the storage chamber 100 is forcibly discharged to the outside of the storage chamber 100 by driving the discharge pump 500 (step 270).

Even while the cleaning liquid is discharged, the air supply unit 210 continues to spray high pressure air. That is, the air supply unit 210 continues to inject air to the venturi valve 220 regardless of the driving of the discharge pump 500, so that the chuck table 12 can be continuously supplied with vacuum even while the cleaning liquid is discharged. . Therefore, even when the cleaning liquid is discharged, the polishing operation can be continued without stopping.

When the cleaning liquid is discharged by the driving of the discharge pump 500, the level of the cleaning liquid is gradually lowered. When the level of the cleaning liquid is lower than the high level LS2, the second water level sensor 300b detects the level of the second detection signal. Stop occurrence.

However, even if the generation of the second detection signal is stopped, the pump driving unit 400 according to the present invention performs a self-maintaining function using the first detection signal without immediately stopping supplying power to the discharge pump 500, so that the level of the cleaning liquid is low. Power supply to the discharge pump 500 is continued until it becomes lower than LS1. That is, the pump driving unit 400 according to the present invention starts to supply power to the discharge pump 500 by the second detection signal and then maintains the power supply to a certain time using the first detection signal regardless of the second detection signal. It operates as a self-holding circuit that performs the holding function.

Referring to the self-maintenance function of the pump drive unit 400 in more detail as follows.

If the power supply to the discharge pump 500 is determined according to whether or not the second detection signal is generated, the second detection signal is stopped and the discharge of the cleaning solution is stopped as soon as the level of the cleaning liquid is lower than the high level LS2. do. Then, when the level of the cleaning liquid reaches the high level LS2 again, the cleaning liquid is discharged again, and when the level of the cleaning liquid is lower than the high level LS2 again due to the discharge of the cleaning liquid, the cleaning liquid is stopped again. Therefore, the level of the cleaning liquid is continuously lowered slightly around the high level LS2, and the process of reaching the high level is repeated, and the driving of the discharge pump 500 is also frequently repeated.

Therefore, the discharge of the cleaning liquid starts when the level of the cleaning liquid reaches the high level LS2 (when the second sensing signal is generated) and when the level is lower than the low level LS1 (the generation of the first sensing signal is stopped). Must be continued).

To this end, the pump driving unit 400 of the present invention performs a self-maintenance function using the first detection signal. That is, even if the generation of the second detection signal is stopped, since the level of the cleaning liquid is still higher than the low level LS1, the first detection signal is continuously generated and applied to the b connection terminal of the pump driver 400. Therefore, the relay switch RS1 physically connected to the b connection terminal continues to receive the first detection signal through the b connection terminal even though the second detection signal from the second water level detection sensor 300b is not applied. It remains connected to the connection terminal. As the relay switch RS1 remains connected to the b connection terminal, the relay switch RS2 also remains connected to the d connection terminal, so that the discharge pump 500 can continue to receive driving power. do.

The power supply to the discharge pump 500 is continued until the level of the cleaning liquid in the storage chamber 100 is lowered below the low level LS1 so that the first detection signal does not occur. As described above, the pump driving unit 400 of the present invention is supplied to the discharge pump 500 when the second detection signal is generated, but since the generation of the second detection signal is stopped, the first detection signal is not immediately stopped. The self-maintenance function is performed to maintain the power supply until the generation of the first detection signal is stopped.

When the cleaning liquid continues to be discharged by the self-maintaining function such that the level of the cleaning liquid becomes lower than the low level LS1, the first water level sensor 300a stops generating the first detection signal (step 280).

When the detection signal is no longer applied to the relay switch RS1 due to the interruption of the first detection signal, the relay switch RS1 switches from the b terminal to the a terminal again, so that the relay switch RS2 is also relayed. It disconnects from d terminal and switches back to c terminal.

As such, when the relay switch RS2 is moved to the c terminal, the power supply to the discharge pump 500 is cut off through the d terminal, and thus the discharge pump 500 is no longer driven, thereby discharging the cleaning liquid. (Step 290).

After the level of the cleaning liquid is lower than the low level LS1, the processes subsequent to step 230 are repeated.

As such, in the related art, the vacuum is supplied to the chuck table by making the chamber into a vacuum state using a main vacuum pump. However, the present invention provides a vacuum to the chuck table without discharging the chamber, thereby discharging the cleaning liquid stored in the chamber. Vacuum can be continuously supplied to the induction table, eliminating equipment downtime.

1 is a schematic view showing a structure for discharging a cleaning liquid used during a polishing process in a conventional wafer backside polishing apparatus after vacuum suction and storage and then discharging the cleaning liquid to the outside.

Figure 2 is a block diagram showing the configuration of a wafer back surface polishing apparatus according to the present invention.

Figure 3 is a flow chart for explaining the operation of the wafer back surface polishing apparatus according to the present invention described above.

4 shows the structure of a venturi valve.

Claims (12)

A vacuum unit for supplying a vacuum to the chuck table and sucking the cleaning liquid; A storage chamber storing the cleaning liquid sucked through the vacuum unit; A level sensor detecting a level of the cleaning liquid stored in the storage chamber; A discharge pump for discharging the cleaning liquid stored in the storage chamber; And And a pump driver configured to supply driving power to the discharge pump according to the output signal of the water level detector. The method of claim 1, wherein the vacuum unit And operate independently of the discharge pump to supply a vacuum to the chuck table while the discharge pump is driven. The method of claim 1, wherein the vacuum unit And a vacuum supply directly to the chuck table without passing through the storage chamber. The method of claim 1, wherein the vacuum unit An air supply unit for injecting air; And And a vacuum valve for supplying a vacuum to the chuck table by adjusting a flow of air injected from the air supply unit. The method of claim 4, wherein the vacuum valve The back surface polishing apparatus according to claim 1, wherein the cleaning liquid of the chuck table is sucked under vacuum and supplied to the storage chamber by using the vacuum provided to the chuck table. The method of claim 4, wherein the vacuum valve Wafer back surface polishing apparatus, characterized in that the Venturi (Ventury) valve. According to claim 1, wherein the water level detection unit A first level sensor configured to output a first detection signal when the level of the cleaning liquid reaches a preset first level; And And a second level sensor configured to output a second detection signal when the cleaning liquid reaches a preset second level. The method of claim 7, wherein the water level sensor A wafer backside polishing apparatus, characterized in that it is a capacitive proximity sensor. The method of claim 7, wherein the pump drive unit And a magnetic holding circuit for supplying driving power to the discharge pump and performing a self-holding function according to the first sensing signal when the second sensing signal is generated. The method of claim 7, wherein the pump drive unit A first connection terminal connected to an output terminal of the first water level detection sensor and receiving the first detection signal; A second connection terminal connected to a power input terminal of the discharge pump; A first relay switch connected to an output terminal of the second water level sensor and connected to the first connection terminal when the first detection signal or the second detection signal is applied; And And a second relay switch connected to the driving power source and relayed to the first relay switch, the second relay switch being connected to the second connection terminal when the first relay switch is connected to the first connection terminal. The method of claim 1, And an exhaust unit for discharging air introduced into the storage chamber to the outside through the vacuum unit. The method of claim 11, wherein the exhaust portion And an open valve for always opening the inside of the storage chamber to the outside.

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