JPH0729859A - Manufacture of semiconductor device and semiconductor manufacturing apparatus - Google Patents

Abstract

PURPOSE:To provide a method in which ice is not produced on the surface of a wafer by the fixation method (by a refrigerant chuck) of the wafer by freezing when a wafer treatment for performing an alignment operation is executed and to provide a semiconductor manufacturing apparatus used for the method. CONSTITUTION:Before an alignment operation, a substance 8, whose freezing point is lower than a freezing temperature, as an antifreezing material, e.g. methyl alcohol, is discharged from a nozzle 9 arranged on a wafer 1 on a water layer formed on a cooling table 2, and a methyl alcohol film is formed on the surface of the wafer 1. Thereby, the water film is cooled, and an ice layer 16 is formed. When the wafer 1 is fixed and bonded to the table 2 by the ice layer 16, no freezing is caused on the wafer 1, an alignment mark can be visually observed sufficiently, and an alignment operation can be performed easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fixing a semiconductor wafer (hereinafter referred to as a wafer) during a semiconductor device manufacturing process and a semiconductor manufacturing apparatus used for the fixing method.

[0002]

2. Description of the Related Art A semiconductor device such as an IC or an LSI is designed to design an integrated circuit formed on a semiconductor substrate, a mask forming process for drawing an electron beam used to form the integrated circuit, a single crystal. A wafer manufacturing step of forming a wafer of a predetermined thickness from an ingot, a wafer processing step of forming semiconductor elements such as integrated circuits on the wafer, an assembly step of forming a semiconductor device by separating the wafer into each semiconductor substrate and packaging each. It is formed through an inspection process and the like. A manufacturing apparatus required for each process is prepared for each process. In addition to these, as the semiconductor manufacturing apparatus, equipment such as a pretreatment apparatus and an exhaust gas processing apparatus and a manufacturing apparatus necessary for the environment are also used. In an exposure process for a photosensitive material used for forming a mask for forming a pattern on a wafer, a backside grinding process for reducing the thickness of the wafer, or a dicing process for cutting the wafer to form a plurality of semiconductor chips, etc. , The wafer must be fixed to the processing table or the stage. Conventionally, for example, an adhesive synthetic resin tape called a wafer sheet has been used to hold a wafer or a diced semiconductor chip.

In particular, a dicing process for forming kerfs in order to divide the wafer into individual semiconductor chips, a crevice is formed along the grooves processed in the streets of the wafer, and individual chips are formed. In the breaking process for dividing, the backside grinding process for grinding the backside of the wafer to make the wafer have a predetermined thickness, and the die bonding process for individually positioning the chips at predetermined positions of the lead frame or package, this is It's being used. The technique of dividing the semiconductor chip formed on the wafer into individual pieces is called dicing, and a cutting groove is made along the chip with a laser or diamond needle to mechanically divide the scribing method and the thin diamond wheel at high speed. There is a dicing saw method that can make deep cuts and divide into individual chips when cutting. FIG. 11 shows a conventional dicing device. The wafer 1 is attached to an adhesive tape 14, and the adhesive tape 14 is placed on the chuck table 10. The adhesive tape 14 is fixed around the periphery thereof by a fixing ring 13, and the fixing ring 13 is fixed by a fixing ring holding claw 12 attached to the moving stage 5 to fix the wafer 1 to the moving stage 5. .

On the stage 5, first, the dicing line is recognized by using the alignment camera 6, the stage 5 is arranged at a predetermined position, and then the dicing blade 7 is used to form the dicing line on the wafer 1. A notch is made along it to divide it into individual chips. But,
In this method, the wafer has to be fixed to the fixing ring by using an adhesive tape before dicing, which takes time. Further, it is necessary to prepare an adhesive device for fixing the wafer, which tends to complicate the manufacturing process. This is the same in complexity in the back surface grinding process for the wafer, and is a common problem in the manufacturing process in which the wafer is fixed using an adhesive tape. There is a method of solving this common problem and simply utilizing freezing to fix the wafer to the dicing stage (for example, Japanese Patent Laid-Open No. 62-79956). This is a method of spraying water between a wafer and a dicing stage prior to dicing, and fixing the wafer to the stage by freezing the wafer, water, and the dicing stage (hereinafter,
It is called a frozen chuck. FIG. 12 is a cross-sectional view showing a conventional process of fixing a wafer by freezing.

First, pure water 15 is sprinkled on the cooling table 2 from the nozzles 18 and the like, and the wafer 1 is placed thereon. The pure water 15 wets the surfaces of the cooling table 2 and the wafer 1 that face each other, and forms a uniform water film therebetween. Next, a cooling device (not shown) is used to cool the cooling table 2 connected thereto. Then, the pure water film 15 is changed to a uniform ice layer 16. Cooling temperature is -1
Keep the temperature below 5 ° C, and keep this temperature
It is maintained until predetermined wafer processing such as backside grinding and exposure process is completed. After the wafer processing is completed, the ice layer 16 is melted by hot air or the like, and the wafer 1 is separated from the cooling table 2. The adhesive strength due to this freezing is 10 to 8
It is about 0 kg / cm ² , and becomes maximum at around −10 ° C.

[0006]

However, a method (freezing chuck) utilizing freezing as a method for fixing a wafer is as follows.
The manufacturing process is simplified by eliminating the step of attaching the adhesive tape to the wafer and the use of an adhesive device, but water drops on the surface of the wafer due to the temperature difference with air during the process of freezing water. Water droplets are generated, and the water droplets also freeze on the surface of the wafer in white. That is, as described in FIG. 12, the ice layer 17 is sometimes formed on the surface of the wafer 1 due to the water contained in the atmosphere in which the cooling table is placed. Therefore, the alignment mark is recognized by the camera, and based on this, for example, alignment work for positioning the wafer during dicing cannot be performed, and the wafer cannot be accurately processed. The present invention has been made under such circumstances, and in a method of manufacturing a semiconductor device for executing a wafer process including an alignment work,
It is an object of the present invention to provide a method of preventing ice from being generated on the surface of a wafer by a method of fixing a wafer by freezing (freezing chuck), and a semiconductor manufacturing apparatus used in this method.

[0007]

SUMMARY OF THE INVENTION According to the present invention, when carrying out a wafer process for performing alignment work, ice is not generated on the surface of the wafer by a method of fixing the wafer by a freeze chuck. -The surface of the c is characterized in that it is coated with a substance having a freezing point lower than the freezing chucking temperature (the temperature at which the freezing chuck is performed). The method for manufacturing a semiconductor device of the present invention comprises a step of forming a water layer on the surface of the cooling means, and a semiconductor wafer having an alignment mark formed on the surface thereof on the surface of the cooling means on which the water layer is formed. The step of placing, the step of forming a film of an anti-icing material on the surface of the semiconductor wafer, the layer of water is frozen at a predetermined freezing temperature using the cooling means, changing it to an ice layer, Fixing the semiconductor wafer to the cooling means by this layer of ice, detecting the alignment mark, determining the position of the semiconductor wafer based on the result, and processing the positioned semiconductor wafer It is characterized by having.
The anti-freezing material is made of a substance having a freezing point lower than the predetermined freezing temperature. The film of the anti-icing material is formed at least on the alignment mark of the semiconductor wafer and in the vicinity thereof.

Further, this method of manufacturing a semiconductor device can be applied to a dicing process of a semiconductor wafer.
Furthermore, the semiconductor manufacturing apparatus of the present invention, a cooling means for freezing a layer of water to change into a layer of ice to bond the semiconductor wafer,
Water is supplied to the surface of the cooling means to form a water layer, and means for supplying an anti-icing material to the surface of the semiconductor wafer placed on the water layer. Is characterized by. The means for supplying the anti-icing material to the surface of the semiconductor wafer has at least one anti-icing material supply nozzle.

[0009]

By coating the surface of the wafer with a substance having a freezing point lower than the freezing chucking temperature, freezing of the surface of the wafer is prevented. Therefore, since the alignment mark is not covered with a layer of white ice, it is possible to clearly see the image with the camera and easily perform the alignment work.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the dicing apparatus of the present invention. The wafer 1 is placed on the cooling table 2. The wafer 1 is fixed on this table by freezing. The cooling table 2 has an electronic refrigeration element such as a Peltier effect element enclosed therein and is controlled by the cooling control device 4 via the wiring 3 to cool the wafer 1 placed on its surface. It has a structure to decompress. The cooling table 2 is placed on the moving stage 5, and the dicing process is advanced in accordance with the movement thereof. Before dicing, the position of the alignment mark formed on the surface of the wafer 1 in advance is confirmed by the alignment camera 6, and then the wafer 1 is cut along a predetermined cutting line to form individual chips.
In this embodiment, prior to this alignment work, a substance 8 having a freezing point lower than the freezing temperature, which is an antifreezing material, such as methyl alcohol (melting point = −94 ° C.) is discharged from a nozzle 9 arranged on the wafer 1. Then, the surface of the wafer 1 is covered. However, when the method of fixing the wafer 1 to the table by freezing (freezing chuck) is used, the freezing may be formed on the surface.

This makes the portion of the wafer surface where the alignment mark is formed white, and the alignment work is substantially impossible, and the accuracy of wafer cutting is reduced.
However, by forming the film 23 of methyl alcohol on the surface of the wafer, the freezing is eliminated and the alignment mark can be sufficiently observed. The nozzle 9 arranged above the wafer 1 is connected to a supply tank (not shown) through a pipe, and methyl alcohol is supplied from this supply tank.

FIG. 2 is a plan view showing the surface of a silicon semiconductor wafer to be processed by this semiconductor manufacturing apparatus. FIG. 3 is an enlarged plan view of the area A in the previous figure, and FIG.
FIG. 5 is a cross-sectional view of the B'portion, and FIG. 5 is a schematic plan view of the cooling table and the associated supply nozzle. A semiconductor element 20, such as an integrated circuit, is formed on the surface of the wafer 1 in a region where the surface of the wafer 1 is finally cut to form individual chips. Each chip formation region is formed on the wafer 1 in a dice pattern. The semiconductor element 20 is formed in this chip formation region, and electrodes and wirings are formed on the surface thereof via an interlayer insulating film, and these are protected by a passivation film. Therefore, this portion is the surface of the silicon wafer. It is about several μm thicker. Therefore, the lattice-shaped grooves 24 having the bottom surface of the wafer are formed between the semiconductor elements 20. An alignment mark 21 having a shape as shown in FIG. 3 is further formed on the wafer 1. This shape is arbitrary and is formed to have a size of about 50 μm square. In order to form this mark, first, an aluminum film or the like is applied to the wafer 1
It is deposited by vapor deposition or the like on the top, and this is patterned using a photoresist or the like as a mask. The aluminum film 22 is left on the peripheral portion of the surface of the wafer 1.

Methyl alcohol is dripped onto the surface of the wafer 1 from the nozzle 9 shown in FIG. 3 and 4
As shown in, the methyl alcohol coating 23 does not need to cover the entire surface of the wafer, and only needs to cover a portion where icing is not necessary. In this case, alignment work can be performed smoothly, It is formed on the alignment mark 21 and its periphery. If the film 23 is held until the alignment work is completed, it is not necessary thereafter. Even if the coating film 23 of methyl alcohol is dropped a little more, since the groove 24 serves as a barrier, it does not unnecessarily diffuse. The alignment mark 21 is used for the semiconductor element 20.
It is formed on the bottom surface of the groove 24 between them. Then, since the methyl alcohol film 23 is coated mainly on it, even when the wafer 1 is fixed to the cooling table 2 by the freeze chuck, the wafer surface has an ice layer 17 as shown in the conventional example. Not formed (see FIG. 12). Even after the wafer 1 is fixed on the table, the temperature is kept at -15 ° C or lower until the dicing is completed. Therefore, it is necessary to take care not to freeze the wafer surface until the alignment work is completed. In this embodiment, the methyl alcohol coating 23 is applied on the alignment marks 21 at four locations. The alignment marks 21 are usually formed on several points on one wafer.

Therefore, for example, the nozzles 91, 92, 93, 94 for supplying the coating film 23 of a substance having a freezing point lower than the frozen chucking temperature such as methyl alcohol are provided and provided in the vicinity of each alignment mark 21. It is improving efficiency. Then, methyl alcohol is supplied from each nozzle to form the coating 23 on the alignment mark 21 in the vicinity thereof. Next, the dicing process of this embodiment will be described with reference to FIGS. 6, 7, and 8. FIG. 6 is a flow chart for explaining the process from fixing the wafer to freeing it after the dicing process, and FIGS. 7 and 8 are manufacturing process sectional views for explaining the process for fixing the wafer. And a cooling table to which the wafer is fixed. The cooling table 2 is composed of a support 25 and a chuck head 26, and the wafer 1 is placed and fixed on the chuck head 26 supported on the surface of the support 25. As shown in FIG. 1, the support base 25 contains the wiring 3 from the cooling control device 4 and is connected to a cooling element (not shown) arranged in the support base 25 to control this cooling element. To do. For the cooling element, for example, an electronic refrigeration element utilizing the Peltier effect is used.

The Peltier effect is achieved by using two kinds of metals, or
It is a thermoelectric phenomenon of a solid that generates and absorbs heat other than Joule heat when a current is applied by connecting a metal and a semiconductor. This phenomenon is reversible and is the opposite of the Seebeck effect of the similar thermoelectric phenomenon. The cooling element operates a switch attached to the cooling control device to cool the chuck head 26. First, (1) Pure water is dropped from the nozzle 18 connected to a water supply tank (not shown) onto the surface of the chuck head 26 of the cooling table 2 to form a water film 15 (FIG. 7A). ). Next, (2) the wafer 1 is placed on the water film 15 (FIG. 7B). Next, (3) methyl alcohol as an anti-icing agent is discharged from a nozzle 9 connected to a supply tank (not shown) to form at least an alignment mark (not shown) on the surface of the wafer 1. The film 23 is formed on the existing portion (FIG. 8).
(A)). Next, (4) the cooling control device is operated to cool the cooling table 2. The temperature of about -10 ° C to -20 ° C is maintained for several tens of seconds to change the water film 15 into the ice film 16. The wafer 1 is firmly fixed to the chuck head 26 of the cooling table by the ice film 16 (FIG. 8).
(B)). The adhesive strength of this ice film 15 is about 1 at -10 ° C.
It is 0 to 80 kg / cm ² .

During this cooling, since the methyl alcohol film 23 is present at least in the region where the alignment mark is formed on the surface of the wafer 1 and in the vicinity thereof, the ice layer 16 as shown in FIG. 12 is formed. Not done. Therefore, the alignment work using the next camera is smoothly performed. After the wafer 1 is fixed to the chuck head 26, the cooling table 2 is placed on the moving stage 5 shown in FIG. 1 where the wafer processing is performed. The cooling table 2 may be placed on the moving stage 5 before the wafer is fixed by the freeze chuck. The moving stage is provided with an alignment camera 6 and a rotary blade 7 at its alignment portion and cut portion, respectively. Next, (5) the alignment camera is used to recognize the alignment marks on the wafer and perform alignment work for adjusting the position of the wafer. Next, (6)
The wafer arranged at a predetermined position is diced, and the semiconductor chips formed on the wafer are individually separated. Next, (7) the ice layer 16 fixing the wafer to the chuck head 26 of the cooling table is melted to take out each semiconductor chip from the wafer processing apparatus. When thawing, the cooling element attached to the cooling table is used. It usually takes about 10 seconds to thaw. The heat absorption phenomenon is used for fixing the wafer, and the heat generation phenomenon is used for thawing.

Next, a method of supplying the anti-icing material formed on the surface of the wafer will be described with reference to FIGS. These are all plan views of the cooling table. When forming an ice layer for a freeze chuck on the surface of the chuck head 26 according to the flowchart of the wafer fixing method shown in FIG. 6, an anti-icing material such as methyl alcohol is supplied to the wafer from a nozzle connected to a supply tank. . The anti-icing material is supplied to prevent freezing of the wafer surface during the freeze chuck, and by preventing this freezing, the alignment mark formed on the wafer surface can be clearly identified by the camera. Therefore, the film of this anti-icing material, at all times of the processing steps using the predetermined wafer processing equipment,
And, it need not be applied to the entire surface of the wafer. This film may be present in the region where the alignment mark is formed on the wafer surface when forming the ice layer for the freeze chuck performed in the processing step, and when the alignment work is completed, the treatment is performed. This coating is unnecessary even if the process is not completed. That is, as shown in FIG. 5, for example, if the alignment marks 21 are formed at four positions on the surface of the wafer 1, the film 23 of an anti-icing material such as methyl alcohol is formed only in the vicinity thereof.

Therefore, the anti-icing material supply tank is mounted on the cooling table or in the vicinity thereof so that the nozzles 91, 92, 93 and 94 for supplying the anti-icing material are arranged near the alignment mark 21. . Further, the film 23 of the anti-icing material can be formed almost on the front surface of the wafer 1 as shown in FIG. In this case, since the number of the nozzles 9 for supplying the anti-icing material can be one, the structure of the wafer processing apparatus can be simplified. As described above, the anti-icing material is liquid, but gas can be used. For example, as shown in FIG. 10, when nitrogen is used as the anti-icing material, the water layer 15 formed between the cooling table 2 and the wafer 1 is changed to the ice layer 16, that is, the freeze chuck. It is possible to adopt a method in which the nitrogen of the anti-icing material 8 is continuously supplied from the nozzle 9 until the above is completed and the alignment work is completed. Liquids such as methyl alcohol will naturally dissipate without any special removal work after their function ends, but it takes time. On the other hand, the gas is scattered immediately when the supply is stopped, so that the influence on the subsequent process can be ignored. In consideration of these, as the anti-icing material, nitrogen can be applied as a gas, and as the liquid, alcohol such as methyl alcohol or ethyl alcohol, or other materials can be applied. Further, the wafer processing is applied not only to the dicing process but also to a process that requires alignment work such as an exposure process.

[0019]

As described above, according to the present invention, since the wafer is placed on the moving stage without using the adhesive tape or the fixing ring, a working device for attaching these is not required. Further, since the freezing of the wafer surface caused by the freeze chuck is prevented, the alignment work using the camera is facilitated, and the wafer processing including this work such as the dicing process can be easily carried out.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of a wafer used in the semiconductor manufacturing apparatus according to the embodiment of the present invention.

FIG. 3 is an enlarged plan view of a region A of FIG.

FIG. 4 is a cross-sectional view taken along the line BB ′ of FIG.

5 is a plan view of a cooling table of the semiconductor manufacturing apparatus of FIG.

FIG. 6 is a flowchart showing the manufacturing process of the embodiment of FIG.

FIG. 7 is a sectional view of the manufacturing process of the embodiment of FIG.

FIG. 8 is a sectional view of a manufacturing process of the embodiment of FIG.

FIG. 9 is a plan view of a cooling table of the semiconductor manufacturing apparatus of the present invention.

FIG. 10 is a sectional view of a semiconductor manufacturing apparatus according to another embodiment of the present invention.

FIG. 11 is a sectional view of a conventional semiconductor manufacturing apparatus.

FIG. 12 is a sectional view showing a method for fixing a wafer used in a conventional semiconductor manufacturing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Wafer 2 Cooling table 3 Wiring for cooling table 4 Cooling control device 5 Moving stage 6 Alignment camera 7 Dicing blade 8 Anti-icing material 9, 91, 92, 93, 94, Anti-icing material supply nozzle 10 Chuck Table 12 Fixing ring Holding claw 13 Fixing ring 14 Adhesive tape 15 Water layer 16, 17 Ice layer 18 Water supply nozzle 20 Semiconductor element 21 Alignment mark 22 Aluminum film 23 Anti-freezing agent film 24 Groove 25 Chuck head 26 Support Stand

Claims (6)

[Claims] 1. A step of forming a water layer on the surface of the cooling means, and a step of placing a semiconductor wafer having alignment marks formed on the surface thereof on the surface of the cooling means on which the water layer is formed. , A step of forming a film of an anti-icing material on the surface of the semiconductor wafer, freezing the water layer at a predetermined freezing temperature using the cooling means, changing it to an ice layer, and by this ice layer A step of fixing the semiconductor wafer to the cooling means; a step of detecting the alignment mark and determining a position of the semiconductor wafer based on the result; and a step of processing the positioned semiconductor wafer. A method for manufacturing a semiconductor device, comprising: 2. The method for manufacturing a semiconductor device according to claim 1, wherein the anti-icing material is made of a substance having a freezing point lower than the predetermined freezing temperature. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the film of the anti-icing material is formed on and near the alignment mark of the semiconductor wafer. 4. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor wafer is subjected to a dicing process in the step of processing the positioned semiconductor wafer. 5. Cooling means for freezing a water layer to turn it into an ice layer for adhering semiconductor wafers; supply means for supplying water to the surface of the cooling means to form a water layer; And a means for supplying an anti-icing material to the surface of the semiconductor wafer placed on the layer. 6. The semiconductor manufacturing apparatus according to claim 5, wherein the means for supplying the anti-icing material to the surface of the semiconductor wafer has at least one nozzle.