JPS626344B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for dicing and cleaning semiconductor wafers.

[Prior art]

In manufacturing semiconductor elements such as transistors and semiconductor integrated circuits (ICs), the process begins with preparing ingot-shaped single crystal semiconductor materials and cutting these semiconductor ingots into a number of semiconductor wafers. The cutting operation of the semiconductor ingot is generally known as slicing, and the semiconductor ingot is cut with a diamond cutter or the like.

The semiconductor wafer thus obtained is then sent to various steps such as oxidation, diffusion, and vapor deposition, and a large number of semiconductor element regions are formed within the semiconductor wafer.

In order to individually separate the large number of semiconductor elements formed within the semiconductor wafer, the semiconductor wafer is then subjected to a dicing operation, and a large number of vertical and horizontal grooves are formed on the wafer surface so as to surround each element. Next, the wafer is subjected to a breaking operation, and the wafer is divided into a number of semiconductor pellets (dies or chips) by breaking the wafer along the dicing grooves. These pellets are then sorted and classified according to their characteristics, and then each pellet is brazed onto a support such as a lead frame or stem, followed by wire bonding and encapsulation to form semiconductor devices. It is assembled as.

By the way, in the above-mentioned series of manufacturing processes, the dicing work is a work to separate a large number of semiconductor pellets from a single semiconductor wafer on which a large number of semiconductor elements are formed, so the work can be done quickly and efficiently. It needs to be done efficiently.

FIG. 1 shows a series of conventional dicing operations in order of process. First, as shown in A, case 2 stores a large number of wafers 1 to be diced.
Next, as shown in B, pick up the wafers 1 one by one from the case 2 with the tweezers 3, place them on the dicing table 4, and position them.
Perform the original dicing work using the dicing blade 5 as shown in C. Next, as shown in D, the wafer 1 that has been diced is transferred from the table 4 by the tweezers 2, and then transferred to the case 2 again as shown in E.
stored inside.

However, the conventional dicing operation was inefficient because more time was spent on preparatory work related to the steps before and after the dicing operation than the time required for the actual dicing operation itself.

In other words, since all wafer handling work before and after dicing is done manually, and because it takes time to position (align) the wafer to be diced on a predetermined table, it is difficult to start the original dicing process. The number did not increase.

In addition, since handling such as setting and removing the wafer from the dicing table is done manually, the method and strength of the mechanical external force applied to the wafer becomes unstable, resulting in mechanical damage to the wafer. was inevitable.

[Problems with conventional technology]

By the way, in the past, after cutting with a rotary blade, it was left to dry, but according to the analysis of the present inventor, if the cutting waste is completely dried without being sufficiently removed, large and small particles will be removed. It has become clear that the cutting waste forms a ceramic-like mass and becomes a deposit that is extremely difficult to remove.

In order to prevent the formation of such strong deposits, the present inventor proposed spin cleaning, a combination of spraying cleaning water (waterjet) and rotating the wafer (suction spin table) immediately after the dicing process. The present invention was developed by paying attention to the fact that this is effective.

[Object of the present invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dicing device that can completely remove cutting waste and the like.

[Summary of the invention]

The gist of the present invention is to provide a dicing process in which the semiconductor wafer is fixed to a first table and the semiconductor wafer is diced with a rotating blade while supplying a cooling liquid; a transfer step of automatically transferring the semiconductor wafer to a second table separate from the first table; fixing the semiconductor wafer on the second table and applying a cleaning liquid to the surface of the semiconductor wafer while rotating the second table; The dicing and cleaning method includes a spin cleaning and drying step of cleaning the surface of the semiconductor wafer by spraying and then performing spin drying by rotating the second table.

〔Example〕

An automatic dicing apparatus used in carrying out the present invention will be described below as an example.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a dicing device (hereinafter referred to as the device) that includes a wafer loader section A, a wafer positioning section B,
It consists of a wafer alignment section, a dicing section C, a wafer cleaning section C, a wafer unloader section E, a wafer chuck section F, and the like. Particularly important in the above configuration is the wafer chuck part F. The chuck mechanism is a so-called Bernuy chuck that uses fluid (air, etc.) and buoyancy when sprayed onto the object to be processed, and is used to transfer the wafer between each component. The handling work is performed using this chuck without directly touching the object to be processed.

Each component will be explained in detail below. FIG. 3 shows a wafer loader section, in which a cartridge 6 containing a certain number of wafers 1 (for example, about 20 to 25) to be diced is set at a predetermined position 7 of the apparatus. An air chute 8 is provided at this position 7, and when the wafer 1 is placed (supplied) from the cartridge 6 onto the end of the air chute 8, the wafer 1 is immediately exposed to the air indicated by the arrow on the air chute 8. It is transferred in the direction of spraying. The cartridge 6 is filled with wafers that are regularly arranged in a vertical line, for example, and the wafers at the bottom of the cartridges (the wafers placed on the air chute) are particularly exposed to light emitted from the light source 9. Light is placed in the beam path leading to phototransistor 10. The output signal of the phototransistor 10 is transmitted to the motor 11, and the operation of the motor 11 is controlled according to this output signal. For example, if the wafer is in the above path as shown in B (the state where the light beam is completely blocked), the phototransistor 10 transmits a "wafer present" signal to the motor 11, and the motor 11 does not operate at this time. When the wafer is transferred onto the air chute in the next instant as shown in A, the light beam path becomes conductive and the phototransistor 10 transmits a "no wafer" signal to the motor 11. is operated to lower the wafers 1 in the cartridge 6 one pitch at a time. Figure 3 C and D
1 shows other examples of wafer detection methods, C shows a method of detecting from the rear of the cartridge 6, and D shows a configuration in which another detection means is added to the above method C on the back side of the air chute. . In method D, if the wafer is caught for some reason at the air chute inlet, the phototransistor 10'
A feedback signal is transmitted from the motor to the motor to prevent the feeding of subsequent wafers. Each of the above methods can be selected as appropriate depending on the purpose.

The wafer sent onto the air chute is placed on an alignment table as shown in FIG. 4 at the other end of the air chute. First, the wafer 1 transferred to the other end of the air chute 8 is transferred onto the alignment table 12, and is sucked into a vacuum suction hole provided on the surface of the wafer 1, and a brake is applied to suppress the transfer speed. Then, the two guides 13 change the direction in a fixed direction. two guides 13
Three positioning pins 14 are provided at the center position between them as shown in C. Of these, the two pins at both ends remain fixed, but the one pin in the center is movable back and forth. It's getting old. Note that since an air blowing hole is also provided on the table 12 in addition to the vacuum suction hole, the wafer is in a floating state. In this state, as shown in E, the table 12 is tilted by the air cylinder 15 and rotated with the wafer 1 floating thereon to rotate the wafer. Then, when the wafer 1 is gradually rotated in the direction of the arrow as shown in C, it automatically stops as shown in D with the flat reference surface 16 of the periphery of the wafer 1 in contact with all three of the positioning pins 14. Positioning is performed. The table 12, which was tilted at this point, is returned to its original position.

The wafer, which has been positioned in a fixed direction as described above, is then spatially transferred onto a dicing table by a wafer chuck while maintaining this alignment direction. FIG. 5 shows a Bernuy chuck used as a wafer chuck.

Wafer holding surface 1 whose size corresponds to the area of the wafer
Air supplied from a tube 19 on the back side of the holding surface 17 is blown from a plurality of nozzles 18 provided approximately in the center of the holding surface 17. It works to suck the wafer 1 according to the principle. Reference numeral 20 denotes a wafer positioning portion provided on a part of the peripheral edge of the holding surface 17, and the wafer is attracted to the holding surface 17 with this portion as a reference. However, this positioning part is not always necessary.

The wafer transferred onto the dicing table 21 (Fig. 2) is attracted by a vacuum chuck placed on the edge of this table, and by retracting the table itself, the wafer is transported directly below the microscope 22 for dicing. Positioning (alignment) is performed. This positioning work is carried out using the X, Y and θ
This is done by controlling a direction fine adjustment mechanism (not shown) to align the center of the dicing area of the wafer with a reference plane (aligned with the position of the dicing blade) provided on the microscope. A specific example of the positioning work will be described below with reference to FIG. A shows the relationship between the reference line 22 that first appears on the microscope and the dicing area 23, which naturally do not match. Therefore, next, as shown in B, first adjust the θ direction mechanism to complete the positioning in the θ direction, then adjust the Y direction mechanism as shown in C to complete the positioning in the Y direction, and finally in the same manner as D. The positioning work is completed by adjusting the X-direction mechanism to completely align the reference line 22 with the center of the dicing area 23.

Next, the dicing blade is scanned along the reference line 22 to perform dicing in the Y direction (or X direction), and then the dicing table is rotated 90 degrees to perform dicing in the X direction (or Y direction). Perform area dicing. The rotation of the dicing table can be performed automatically. Further, even if the centers of rotation of the wafer and the dicing table do not coincide, there is no problem when rotating the wafer by 90 degrees.

In addition, since conventional dicing equipment was equipped with a positioning mechanism only in two directions, θ and Y directions, when actually dicing, after performing dicing in the Y direction at C in Fig. 6, Then, the dicing table had to be rotated 90 degrees and positioned in the X direction again as shown in D, and then dicing in the X direction had to be performed again. For this reason, continuous dicing in the X and Y directions is impossible, and the work must be interrupted midway and positioning must be done again, which inevitably leads to inefficiency in the work.

The width of the reference line 22 in the microscope is determined in consideration of the width of the dicing blade and the degree of chipping during the dicing operation. For example, if the width of the dicing blade is selected to be 30μ, the width including chipping will be approximately 50μ. Therefore, if this dimension is displayed on the reference line, there is no need to measure it each time with another measuring mechanism, and it can be known at a glance.

The wafer after dicing is returned to its original position by moving the dicing table. Then, the vacuum suction is released and air is blown up to float above the table, whereupon it is suctioned by the Bernoulli check waiting above and sent to the next cleaning process.

By the way, when dicing the above-mentioned wafers, the wafers are cooled with liquid such as water, so it is very difficult to remove the wafers from the dicing table that are in close contact with the table due to water, etc., and many cracks occur. It was causing defects. For this reason, we considered the following method. FIG. 7 shows an air blowing method, in which A shows a top view and B shows a cross-sectional view, in which air 25 is partially blown onto the wafer 1 from a pipe 24 from diagonally above the wafer 1 to blow the liquid around the wafer. It is something that we try to eliminate.

The wafers are sucked from the dicing table by the Bernuich chuck and sent to the next cleaning process by rotating the chuck arm 90 degrees.

8A and 8B show the cleaning section for wafers transferred by the chuck, where the vacuum chuck 26
The wafer 1 is rotated while being held by the wafer 1, and water is sprayed from above and below by the nozzle 27, thereby cleaning the wafer. After finishing, drain the water and spin dry as shown in B. This cleaning step removes the deposits on the wafer and keeps it clean.

Next, the wafer is again sucked by the chuck and transferred to the wafer unloader section by rotating the chuck arm 90 degrees. That is, the wafer is fed onto the air chute and is transferred in the opposite direction to the loader. An empty cartridge is set at the end of the air chute, and wafers are sequentially supplied to this cartridge.

The cartridge automatically rises one pitch at a time in accordance with the timing of supplying wafers, and these operating mechanisms can be operated in the opposite direction to that of the loader. When the cartridge is full, an alarm is automatically issued and the operator sets an empty cartridge. However, the setting and resetting of these cartridges can be performed automatically.

The wafers stored in the cartridges are sent to the next breaking step, where desired operations are performed and the wafers are separated into individual pellets.

According to the present invention as explained above, handling of wafers to be diced from loading to dicing and unloading is all done automatically and no manual work is required, unlike conventional methods. The dicing work itself can now be done more intensively, and the number of starts has increased significantly.

Furthermore, since manual handling is not required, mechanical damage to the wafers caused by this can be completely prevented.

Furthermore, by configuring the wafer loader section and unloader section adjacent to each other, the size of the apparatus itself can be designed to be extremely compact. Since it is provided in the upper space of the chuck device for spatially transferring wafers between each work process, it does not take up any extra space. As shown in Figure 9, this chuck always rotates in a fixed direction intermittently so that wafers processed in each process are transferred to the next process at the same time, so there is no waste in movement and it is extremely efficient. work purposefully.

〔effect〕

As described above, by performing spin cleaning immediately after cutting, cutting debris and the like can be more completely removed.

Furthermore, by performing a cleaning treatment on the back surface, it is possible to improve the workability in pellet attachment work and the reliability of the final product.

[Brief explanation of the drawing]

FIGS. 1A to 1E are process diagrams showing the case of performing dicing work using a conventional device, FIG. 2 is a top view showing an outline of the device used in carrying out the present invention, and FIGS. A sectional view showing the wafer loader mechanism, FIG. 4 shows the wafer alignment mechanism, and A,
C and D are top views, B and E are cross-sectional views, Figure 5 shows the chuck mechanism, A is a cross-sectional view, B is a bottom view, and Figures 6 A to D show the method of positioning the wafer on the dicing table. 7 shows the wafer air blow mechanism, A is a top view, B is a sectional view, and FIG.
In the figure, A and B, which are the main parts of the present invention, are sectional views showing the wafer cleaning mechanism, and FIG. 9 is a trajectory showing the operating state of the wafer chuck. 1... Wafer, 2... Case, 3... Tweezers, 4, 21... Dicing table, 5... Dicing table, 6... Cartridge, 7...
Wafer loader position, 8...Air shoot, 9...
Light source, 10... Phototransistor, 11... Motor, 12... Positioning table, 13... Guide, 14... Positioning pin, 15... Air cylinder, 16... Wafer reference surface, 17... Chuck holding surface, 18, 27...nozzle, 19, 24
...Tube, 20...Stopper, 22...Microscope reference line, 23...Wafer dicing area, 25
...Air, 26...Vacuum chuck.

Claims (1)

[Claims] 1. A dicing step in which a semiconductor wafer is fixed on a first table and the semiconductor wafer is diced with a rotating blade while supplying a cooling liquid, and the first table is used immediately after dicing the semiconductor wafer diced in the dicing step. a transfer step of automatically transferring the semiconductor wafer to a separate second table; fixing the semiconductor wafer on the second table and spraying a cleaning liquid onto the surface of the semiconductor wafer while rotating the second table; A dicing and cleaning method comprising a spin cleaning and drying step of cleaning the surface and then performing spin drying by rotating the second table.