JPH1187282A - Film for semiconductor wafer device surface protection use and method of semiconductor wafer rear surface abrasion treatment using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To consistently protect the surface of a semiconductor wafer device in each process by a method, wherein two layers of a reinforcing layer, which absorbs the uneveness on the surface of the semiconductor wafer device at the time of back grinding, and a protective layer, which prevents an etching liquid from creeping into the surface of the device at the time of a spin etching, are formed for a film for semiconductor wafer device surface protection use. SOLUTION: A film 10 for semiconductor wafer device surface protection use is formed into a two-layered structure, which consists of a reinforcing layer 11 having an adhesive layer and a protective layer 12 having an adhesive layer such as the layer 11. As a base material 11a of the layer 11, a plastic film, such as a polyethylene film and a polyethylene terephthalate film is suitable, and as the suitable example of the adhesive layer 11b, which is applied on the layer 11, an acrylic resin, a silicone resin, natural rubber and the like are mentioned. As a base material 12a of the layer 12, a high-elastic constant film, such as a polyethylene terephthalate film, is suitable for the purpose of preventing the generation of curling of a semiconductor wafer, which is generated following spin etching. Moreover, as the thickness of the base material 12a, a thickness of 50 to 500 μm or thereabouts is suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer device surface protection method for protecting a semiconductor wafer device surface (hereinafter abbreviated as "device surface") from polishing debris and an etching solution during a back grinding process and a spin etching process. The present invention relates to a film and a method for back grinding and spin etching of a semiconductor wafer using the same.

[0002]

2. Description of the Related Art Semiconductor devices such as personal computers and word processors tend to be miniaturized and densified. Similarly, semiconductor packages and chips constituting the same have become smaller and thinner. As a method of reducing the size, in the case of a semiconductor chip, generally, the back surface of the semiconductor wafer after the fabrication of the semiconductor wafer device is mechanically polished to perform back grinding for thinning. Further, when the final thickness of the wafer is set to 200 to 250 μm or less, a process of chemically etching the back surface is performed in order to remove stress at the time of mechanical polishing and to improve the anti-deposition strength. This step is generally called spin etching because it is performed while rotating the wafer. Specifically, the wafer to be etched is fixed on a rotating table with the back side facing up, and about 1000 r.
This is a method in which a hydrofluoric / nitric acid-based etchant is dropped while rotating at pm, and chemically etched to a desired thickness. Conventionally, in these manufacturing processes, a semiconductor protective film has been used to protect the surface of a semiconductor wafer or chip. When this protective film is used, first, the protective film is attached to the surface of the semiconductor wafer, and the back surface polishing process (back grinding process and spin etching process) is performed. During the subsequent dicing, the protective film is mechanically peeled off. In this way, since the back surface polishing process of the semiconductor wafer can be performed in a state where the protective film is attached, the unevenness of the device surface is absorbed,
It is possible to prevent the semiconductor wafer surface from being contaminated or damaged by polishing debris, an etching solution or the like generated in this step.

[0003]

A problem in this semiconductor wafer back surface polishing process is that a protective film cannot be used consistently from back grinding to spin etching. This is because the spin etching process is a special method. In this spin etching method, for example, as described in Japanese Patent Application Laid-Open No. Hei 7-201805, a cooling fluid such as nitrogen gas is jetted to the device surface side in order to protect the device surface during spin etching. ing. However, when injecting a gas, it is inevitable that the etchant penetrates between the device surface and the protective film due to the flow of the etchant. As a further improvement, it has been proposed to use a protective film provided with a so-called overhang, which is slightly smaller than the size of the wafer.
It has been found that this can prevent erosion of the device surface due to penetration of the etching solution. However, since this protective film has a special size, it must be different from the back grind. The present invention has been made in view of the drawbacks of the conventional technique, and uses a semiconductor wafer device surface protection film capable of protecting a device surface consistently from a back grinding process to a spin etching process, and using the same. An object of the present invention is to provide a method for polishing a back surface of a semiconductor wafer.

[0004]

According to the present invention, there is provided a film for protecting a semiconductor wafer device surface from a back grinding step to a spin etching step after a semiconductor wafer device is formed. This is achieved by a semiconductor wafer device surface protection film consisting of two layers, a reinforcement layer for absorbing device surface irregularities, and a protection layer that can be made slightly smaller than the wafer so that the etchant does not flow into the device surface during spin etching. .

[0005]

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 shows the structure of a film for protecting a surface of a semiconductor wafer device according to the present invention, which has a two-layer structure of a reinforcing layer 11 having an adhesive layer and a protective layer 12 having an adhesive layer as well. As the substrate 11a of the reinforcing layer used in the present invention, a plastic film is preferably used, and a polyolefin such as polyethylene or polypropylene or a copolymer thereof, a polyester such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), or a polychlorinated resin. Examples thereof include vinyl and polyvinyl acetate copolymers, and may be a single layer or a laminate of two or more layers. There is no limitation on the type and structure of the plastic film, but if the film is too hard, it cannot absorb irregularities on the device surface, and therefore needs some flexibility. The thickness of the plastic film is 25 to 200.
μm is preferred. If the thickness is smaller than this, the absorbability of the unevenness of the device surface during back grinding deteriorates, resulting in uneven polishing and cracking of the semiconductor wafer. On the other hand, if it is thicker than this, there is a problem that it is difficult to peel off. This plastic film is preferably subjected to one or both of physical and chemical treatments for the purpose of increasing the adhesion to the adhesive to be applied later. Examples of the physical treatment include sand blasting and polishing treatment, and examples of the chemical treatment include corona treatment, plasma treatment, and primer treatment. Corona treatment is more preferable in view of the balance between the treatment and the effect.

As the pressure-sensitive adhesive 11b applied to the reinforcing layer 11, a general-purpose pressure-sensitive adhesive, for example, acrylic resin, silicone resin, natural rubber, synthetic rubber or the like can be used. Any material having tackiness at room temperature may be used. Of those, an acrylic resin-based adhesive is often used. It is used because it is relatively easy to handle and easy to modify. Furthermore, it is also possible to crosslink with a crosslinking agent for the purpose of improving the cohesive force. Examples of the crosslinking agent include, but are not limited to, isocyanate, epoxy, amine, imide, and melamine resin. In addition, additives such as a tackifier and a coloring agent can be added. At room temperature, the adhesive strength of this adhesive is lower than the adhesive strength of the adhesive 12b of the protective layer described below, and more preferably half or less thereof. this is,
This is for selectively peeling off the film 11 of the reinforcing layer after back grinding. The reinforcing layer 11 is obtained by uniformly applying the adhesive 11b to the plastic film substrate 11a and drying the adhesive. There is no particular limitation on the method of coating, transporting and drying for producing the pressure-sensitive adhesive film, but it is necessary to be careful that the drying temperature is higher than the melting temperature of the plastic film substrate, since the film may be cut. is there. The thickness of the adhesive applied on the film is
It is determined in consideration of the adhesive strength, and is preferably 2 to 80 μm.

Next, as the base material 12a of the protective layer 12,
There is no limitation similarly to the base material 11a of the reinforcing layer described above. However, for the purpose of preventing curling of the semiconductor wafer caused by spin etching, a film having a high elastic modulus such as PET is preferable. The thickness is preferably from 50 to 500 μm. Similarly, various treatments can be performed to increase the adhesiveness with the adhesive. Further, in order to make the reinforcing layer 11 easily peelable, a release treatment may be performed on the back surface of the surface to which the adhesive is applied. For example, silicon peeling type, PVCA
(Polyvinyl carbonate) treatment and the like, but not limited thereto. Adhesive 1 applied to the above protective layer
A general-purpose pressure-sensitive adhesive may be used for 2b, but it is preferable that the adhesive force is reduced by some treatment. this is,
This is because the thickness of the semiconductor wafer after the spin etching is considerably thin, and if a large stress is applied during peeling, the wafer may be damaged. Some treatments include, but are not limited to, heating, cooling, irradiation with radiation such as UV and electron beams, and the like. Especially,
In a semiconductor manufacturing process, moisture, an electron beam and the like adversely affect a semiconductor device, which is not preferable. Therefore, a pressure-sensitive adhesive whose adhesive strength is reduced by applying heat is preferable.

As an example of the pressure-sensitive adhesive whose adhesive strength is reduced by heat, there is a comb-shaped polymer in which the number of carbon atoms in the side chain of the polymer is 8 or more. Comb-shaped polymer
ateet.et.al.; J.Polym.Sci.; Mcromolecular Reviews, 8,
As defined in 117-253 (1974), one main chain has many branches, and a monomer constituting a polymer has a side chain having 4 or more carbon atoms. In the present invention, those having 8 or more carbon atoms in the side chain are used. Examples thereof include poly (α-olefin), poly (alkyl acrylate), poly (alkyl methacrylate), poly (vinyl alkyl ether), poly (vinyl alkyl ester), poly (alkyl styrene) and the like. . Of these, poly (alkyl acrylate) and poly (alkyl methacrylate) are particularly preferred.
0 to 80% by weight must be an alkyl ester having 9 or more, preferably 12 or more carbon atoms. This is because the ester has 9 or more carbon atoms and has side-chain crystallinity, and a primary transition point (melting point) is observed. Examples of these monomers include dodecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, octadecyl acrylate, docosan acrylate, and the like.The same applies to methacrylic acid derivatives, but is not limited thereto. is not. Alkyl esters are preferably straight-chain,
It may be branched. If the amount of these long-chain ester monomers is less than 20% by weight of the total monomers, the decrease in the adhesive force at a temperature higher than the melting point of the polymer becomes unfavorable. The amount of the long-chain ester monomer is 80% by weight.
If the amount is larger than the above range, the adhesive strength near the melting point becomes low and cannot be used as a pressure-sensitive adhesive. The type of the long-chain ester monomer is selected according to a desired melting point. The melting point of this pressure-sensitive adhesive is preferably lower than the temperature at which the protective film is used, and more specifically, it is preferably from 0 to 40C. If the film has a melting point lower than the melting point of the pressure-sensitive adhesive, the adhesive strength may be reduced and the film may not be held.

For the polymer of the adhesive 12b, a general-purpose acrylic acid (methacrylic acid) derivative can be used for controlling the adhesive strength and the like. General-purpose acrylic monomers include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, acrylic acid -2-hydroxypropyl, acrylamide, glycidyl acrylate, 2-cyanoethyl acrylate, acrylonitrile and the like, but are not limited thereto. The same applies to methacrylic acid derivatives. As long as the object of the present invention is not lost, it may be copolymerized with the above-mentioned long-chain ester monomer, blended with two or more homopolymers thereof, or may be used in combination. Rather, it is preferable to modify in order to satisfy the desired properties. The polymer of an acrylic acid (methacrylic acid) derivative used for the pressure-sensitive adhesive 12b is polymerized by a conventionally known method, and is not limited to a polymerization method, a polymerization solvent, a polymerization initiator, and the like, but its weight average molecular weight is expressed in terms of polystyrene. It is preferably from 300,000 to 1.5 million, more preferably from 500,000 to 1,000,000. If the molecular weight is 300,000 or less, the pressure-sensitive adhesive tends to cause cohesive failure when the pressure-sensitive adhesive film is peeled off, which is not preferable. Further, if it exceeds 1.5 million, it is not preferable because the adhesive strength to the adherend becomes weak or it becomes difficult to dissolve in a general-purpose solvent. This pressure-sensitive adhesive 12b also needs to be cross-linked with a cross-linking agent for the purpose of improving its cohesive strength. As the cross-linking agent, those described above may be used, but are not limited thereto. In addition, additives such as a catalyst for promoting the reaction of the crosslinking agent, a tackifier, and a coloring agent can also be added to the pressure-sensitive adhesive. The protective layer 12 is obtained by uniformly applying and drying the pressure-sensitive adhesive 12b on the plastic film substrate 12a. There are no particular restrictions on the conditions for producing the pressure-sensitive adhesive film. The thickness of the pressure-sensitive adhesive applied on the plastic film substrate needs to be large enough to absorb irregularities on the device surface. Generally, it is preferably 30 to 60 μm, but there is no limitation.

It is preferable that the adhesive strength of the protective layer 12 be somewhat high near the melting point of the pressure-sensitive adhesive, and be reduced at a high temperature at which the adhesive is peeled off by heating. Specifically, the adhesive strength to the silicon wafer is preferably 50 gf / 25 mm or more near the melting point of the pressure-sensitive adhesive and 20 gf / 25 mm or less at 60 ° C. If the melting point is not more than 50 gf / 25 mm near the melting point, the protective layer 12 may be peeled off at the time of polishing the back surface of the semiconductor wafer. On the other hand, if it is 20 gf / 25 mm or more at 60 ° C., the stress at the time of peeling the protective layer becomes large, and a load may be applied to the semiconductor wafer to cause breakage. The two adhesive films thus obtained are laminated to form a semiconductor wafer device surface protection film 10. There are no particular restrictions on the pressure and speed of this laminate, but the temperature conditions are
If the height is too high, the pressure-sensitive adhesive undergoes flow deformation to increase the adhesive strength, so that the reinforcing layer 11 is difficult to peel off from the protective layer 12. Therefore, it is necessary to perform temperature management. Particularly, room temperature is preferable. In addition, a separator can be attached to the pressure-sensitive adhesive surface of the protective layer 12. Examples of the paper and the base material include the above-mentioned plastic films. It is also possible to perform a surface release treatment such as the release agent described above. The semiconductor wafer device surface protection film 10 having a two-layer structure created in this manner is attached to the device surface of the semiconductor wafer after device formation. At this time, the protective film 10 cut in the form of a semiconductor wafer in advance is attached. Although there is no limitation on the attaching method and the cutting method, as described above, an excessively high temperature is not preferable. What is important at this time is that the protective layer 12 is made slightly smaller than the semiconductor wafer. This may be performed by sticking to the upper reinforcing layer 11 and then making a cut by punching or the like, or laminating the first punching of the reinforcing layer 11. Here, the former is easier. In the semiconductor wafer to which the protective film 10 has been attached, the so-called overhang from the end of the protective layer 12 to the semiconductor wafer needs to be 1.0 mm or more, and preferably 1.5 mm or more, and more preferably 2.
It is more preferable that the distance is 5 mm or more. It is preferable that the amount of overhang is uniform for the purpose of preventing spin-out of the wafer during spin etching.

As described above, the semiconductor wafer device surface protection film 10 is attached to the device surface of the semiconductor wafer, and the back surface thereof is polished. During the back surface polishing process, the semiconductor wafer device surface protection film protects the devices of the semiconductor wafer. That is, the method of back grinding the semiconductor wafer to which the semiconductor wafer device surface protection film 10 is attached is not particularly limited as long as it is performed by a conventional method.
The temperature is preferably in the range of 10 ° C. lower to 5 ° C. higher than the melting point. This is 1 point higher than the melting point of the adhesive 12.
If the back grind is performed at a temperature lower by 0 ° C., the pressure-sensitive adhesive is hardened, and the adhesive strength may be reduced and peeled off.
If the temperature is higher by 5 ° C., the adhesive strength becomes too high. After the back grinding is completed, only the reinforcing layer 11 is selectively peeled off. This peeling method may be performed by a conventional back grinding tape peeling method, and is not particularly limited. At this time, if the adhesive force of the pressure-sensitive adhesive 11b of the reinforcing layer to the plastic film substrate 12a of the protective layer is high, it is not preferable because only the reinforcing layer 12 cannot be peeled off. Here also, temperature control is performed from the relationship of the adhesive force.

Next, in a spin etching method, the semiconductor wafer device surface on which the protective layer 12 is adhered is fixed downward on a rotary table with the semiconductor wafer back surface facing upward, and rotated at 500 to 1500 rpm. An etching solution of a mixed system of hydrofluoric acid and nitric acid is dropped. On the other hand, nitrogen gas or the like is injected from below. This method is not particularly limited as long as it is a known method, but requires temperature control due to the adhesive force. The present invention provides a back-grinding process by forming two layers, a reinforcing layer for absorbing the unevenness of the semiconductor wafer device surface and a protective layer that can be slightly smaller than the semiconductor wafer so that the etchant does not flow around the semiconductor wafer device surface. The semiconductor wafer device surface can be protected consistently up to the spin etching step. Further, since curling can be prevented, the thickness of the semiconductor wafer can be further reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. However, the present invention is not limited to this embodiment. FIG. 1 is a sectional view conceptually showing a configuration of a semiconductor wafer device surface protection film according to the present embodiment. In the protective film 10 shown in FIG.
0 μm) was used as the base material 11a, and a general-purpose acrylic pressure-sensitive adhesive was applied to the pressure-sensitive adhesive 11b at 3 to 5 μm. Adhesive strength is 30 ~
It was 60 gf / 25 mm. For the protective layer 12, a PET film (188 μm thick) is used for the base material 12a.
For the adhesive 12b, use the above-mentioned high-temperature and low-peelable adhesive,
The melting point was set at 15 ° C. The adhesive strength of this adhesive is 25
℃, 100-200gf / 25mm, 60 ℃
When heated to 5 to 20 gf / 25 mm. Both were pasted at room temperature under the conditions of 2 kgf / cm and 2 m / min. Further, first, the whole was punched into a 6-inch semiconductor wafer, and then only the protective layer 12 was punched into a shape 2.5 mm smaller than the 6-inch wafer, and a cut 12 c was formed to form an overhang 13.

Next, a method of using the semiconductor wafer device surface protection film 10 according to the present embodiment will be described with reference to FIGS. (1) First, a 6-inch semiconductor wafer 21 (600 μm thick)
The die pad 23 is formed on each of the many devices formed in m) and each circuit thereof, and each of them is inspected. Then, a bad mark 22 is attached to the product determined to be defective in this inspection by hitting ink (FIG. 2). This size is formed in the shape of a protrusion having a height of about 5 to 30 μm. (Inspection Step) (2) Next, as shown in FIG. 3, the protective film 10 having the above-described configuration is attached to the surface of the semiconductor wafer 21 on which the ink is applied. (Attaching Step) (3) Then, as shown in FIG.
Is held by the vacuum chuck 31 from the protective film 10 side, and the back surface of the semiconductor wafer 21 is polished by rotatingly pressing a grindstone 32. Here, the semiconductor wafer 21
Is thinned to 250 μm. (Back grinding step) At this time, in this embodiment, since the pressure-sensitive adhesive 11b of the reinforcing layer of the protective film 10 is sufficiently thick, the ink projections 22 are formed.
The height can be absorbed. Therefore, even when the semiconductor wafer 21 is held by the vacuum chuck 31 and back grinding is performed, the contact portion between the vacuum chuck 31 and the semiconductor wafer 21 becomes a point contact, and the semiconductor wafer 21
Will not be damaged.

(4) Next, as shown in FIG.
Is peeled off with a back grinding film peeling tape 41. At this time, the overhang 13 of the protective layer having a small contact area can be easily peeled off from the cut 12c.
It can be removed together with the reinforcing layer 11. (Reinforcing layer peeling step) (5) Next, as shown in FIG. 6, the semiconductor wafer with the protective film is placed on the turntable 5 with the protective layer 12 side down.
It is set to 1 and rotated at 1100 rpm, and an etching solution 52 of a mixed solution of hydrofluoric acid and nitric acid is dropped from the back side of the semiconductor wafer. On the other hand, nitrogen gas 53 is injected from below. Here, the thickness of the semiconductor wafer could be reduced to 50 μm.
At this time, no infiltration of the etching solution was observed on the semiconductor wafer device surface. (6) Finally, the protective layer 12 after the spin etching is completed
After the attached semiconductor wafer 21 was heated to lower the adhesive strength of the protective layer 12, the semiconductor wafer 21 was peeled off with a back grinding peeling tape or the like. The heating method at this time can be heating using a hot plate, an oven, or the like, but is not limited thereto. However, the method using a hot plate is most suitable in the process. At this time, no breakage of the semiconductor wafer was observed. Thus, by using this protective film 10,
During the polishing process of the back surface of the semiconductor wafer,
Almost no outside influences were observed.

[0016]

According to the present invention, by performing back grinding and spin etching of a semiconductor wafer using a semiconductor wafer device surface protection film, the circuit surface of the semiconductor wafer is protected in the process, In addition, it is possible to easily remove the semiconductor wafer device surface protection film only by heating without performing radiation irradiation, thereby simplifying the process and reducing defects. Also,
The present invention can be applied not only to semiconductor wafers, but also to those that perform similar processing.

[Brief description of the drawings]

FIG. 1 is a sectional view conceptually showing a configuration of a film for protecting a surface of a semiconductor wafer device according to one embodiment of the present invention.

FIG. 2 is a cross-sectional process diagram for explaining a method of using the semiconductor wafer device surface protection film according to the example (a semiconductor wafer after an inspection process).

FIG. 3 is a cross-sectional process diagram for explaining a method of using the semiconductor wafer device surface protective film according to the example (protective film attaching step).

FIG. 4 is a cross-sectional process diagram for explaining a method of using the semiconductor wafer device surface protection film according to the example (back grinding process).

FIG. 5 is a sectional process view for explaining a method of using the semiconductor wafer device surface protection film according to the example (reinforcing layer removing step).

FIG. 6 is a cross-sectional process diagram for describing a method of using the semiconductor wafer device surface protection film according to the example (spin etching process).

FIG. 7 is a cross-sectional process diagram for explaining a method of using the semiconductor wafer device surface protection film according to the example (semiconductor wafer after a spin etching process).

[Explanation of symbols]

10: Semiconductor wafer device surface protection film 1
1: reinforcement layer 11a: substrate of reinforcement layer 1
1b: Adhesive for reinforcing layer 12: Protective layer 1
2a: Protective layer base material 12b: Protective layer adhesive 1
2c: Cut of protective layer 13: Outer edge (overhang) of cut of protective layer 2
1: semiconductor wafer 22: ink projection 2
3: die pad 31: vacuum chuck 3
2: Grinding stone 41: Back grinding peeling tape 5
1: Rotary table 52: Etching liquid 5
3: Nitrogen gas

Claims (6)

[Claims] 1. A film for protecting a semiconductor wafer device surface from a back grinding process to a spin etching process after a semiconductor wafer device is formed, wherein a reinforcing layer for absorbing irregularities on the semiconductor wafer device surface during back grinding is provided. A semiconductor wafer device surface protection film consisting of two protective layers that can be made slightly smaller than the wafer so that the etchant does not flow into the device surface during etching. 2. The semiconductor wafer device surface protective film according to claim 1, wherein the adhesive strength of the protective layer is higher than the adhesive strength of the reinforcing layer at a predetermined temperature, and the adhesive strength of the protective layer is reduced by some treatment. 3. The film for protecting a surface of a semiconductor wafer device according to claim 2, wherein the adhesive strength of the protective layer is reduced by increasing the temperature, particularly the temperature. 4. The film for protecting a surface of a semiconductor wafer device according to claim 1, wherein the thickness of the protective layer is 30 to 60 μm. 5. When the reinforcing layer and the protective layer are bonded together, they are the same size, and the lower protective layer is provided with a slightly smaller cut, and when the reinforcing layer is peeled off, the outer edge of the lower protective layer is cut. The semiconductor wafer device surface protective film according to any one of claims 1 to 5, wherein the film can be peeled off together with a part. 6. The semiconductor wafer device surface protecting film according to claim 1 is adhered to a surface of a wafer on which a semiconductor device is formed to perform back grinding, and thereafter, only the reinforcing layer is peeled off. And a method of polishing a back surface of a semiconductor wafer, comprising etching a wafer with a protective layer having an outer shape smaller than the outer shape of the wafer.