JP4371732B2 - Method for forming device surface protection film of semiconductor wafer in semiconductor wafer processing - Google Patents

Description

  The present invention relates to a method for forming a device surface protection film of a semiconductor wafer, which protects a device surface (hereinafter abbreviated as a device surface) of a semiconductor wafer from an etchant in a semiconductor wafer back surface polishing process (spin etching process).

  Semiconductor devices such as personal computers and word processors tend to be smaller and more dense. Similarly, the semiconductor packages and chips constituting the same are becoming smaller and thinner. As a method for reducing the size, in the case of a semiconductor chip, back grinding is generally performed by mechanically polishing and thinning the back surface of the semiconductor wafer after the production of the semiconductor wafer device. Furthermore, in order to remove the stress at the time of mechanical polishing and improve the bending strength, the back surface is chemically etched. Since this process is generally performed while rotating the wafer, it is called spin etching. Specifically, a method of chemically etching to a desired thickness while dropping a hydrofluoric acid / nitric acid based etching solution while fixing the wafer to be etched on the rotary table with the back side of the wafer facing up and rotating at about 1000 rpm. It is.

  Conventionally, in these manufacturing processes, when protecting the surface of a semiconductor wafer or chip, a protective film is formed on the device surface and a back surface polishing process is performed. Thereafter, the protective film is peeled off during dicing. The role of the protective film is to absorb the irregularities on the device surface and prevent contamination or breakage of the semiconductor wafer due to polishing debris or etching solution generated during this process.

  Examples of the device surface protective material for semiconductor wafers include rubber tapes and films. However, it is known that when a rubber-based tape or film is used, the edge of the protective film shrinks due to the heat of the etching reaction, and the etching solution penetrates from there. In order to prevent this, as described in Patent Document 1, for example, a method of injecting a cooling fluid such as nitrogen gas to the device surface side can be mentioned. However, it is inevitable that the etchant penetrates between the device surface and the protective film during spin etching. The penetration of the etching solution causes a problem that a circuit such as an electric element on the device surface is corroded or destroyed.

As a further improvement, it has also been proposed to use a protective tape with a so-called overhang that is slightly smaller than the size of the wafer. For example, as described in Patent Document 2, a semiconductor wafer device surface unevenness is absorbed at the time of back grinding and a pre-cut is made slightly smaller than the wafer so that an etching solution does not flow around the device surface at the time of spin etching. A film for protecting the surface of a semiconductor wafer device comprising two protective layers. In such a method, it is difficult to make a cut slightly smaller than the wafer with high accuracy as a protective layer at the time of spin etching, and it is also difficult to peel only the upper layer.
JP-A-7-201805 Japanese Patent Laid-Open No. 11-87282

  As described above, in the method of Patent Document 1, it is unavoidable that the etching solution penetrates between the device surface and the protective film during spin etching, and the method of Patent Document 2 is a protective layer at the time of spin etching. Therefore, it is difficult to make a cut that is slightly smaller than the wafer with high accuracy, and it is also difficult to peel only the upper layer.

  The present invention has been made in view of these drawbacks of the prior art. When spin etching the back surface of a semiconductor wafer, the penetration of an etching solution is prevented, the device surface is protected, and variations in the outer periphery of the wafer are achieved. It is an object of the present invention to provide a method for forming a protective film that can eliminate the problem.

  In order to achieve the above object, the present inventor uses a polymer compound capable of forming a film by coating on the device surface protective material, and after forming the device surface protective film on the device surface, the size of the periphery of the wafer The present inventors have found that by removing the outer peripheral portion of the protective film with high accuracy so as to be smaller, it is possible to prevent the penetration of the etching solution and the accumulation of the outer peripheral portion of the wafer.

That is, the method for forming a device surface protective film of a semiconductor wafer according to the present invention is a method for forming a protective film for protecting a device surface of a semiconductor wafer from an etching solution in a spin etching process after the device is formed on the semiconductor wafer. In the device surface protective film forming method, the device surface is covered with an adhesion improving layer containing a polyetheramide resin for improving the adhesion between the device surface and the protective film, and the protective film is formed by coating. After covering the adhesion improving layer with a cyclized rubber-based photoresist that can be formed, the protective film is formed by patterning using photolithography so as to be smaller than the periphery of the semiconductor wafer and cover the device. Using the patterned protective film as a mask, the adhesion improving layer is dry-etched. Characterized by patterning using a ring.

  The protective film is preferably a film that is not affected by highly reactive chemicals such as hydrofluoric acid / nitric acid etching solution used for spin etching. For example, a cyclized rubber resin is used. it can. And it is desirable for this cyclized rubber to have photosensitivity.

  According to the present invention, after forming a protective film such as cyclized rubber on the device surface, the outer peripheral portion of the protective film is formed by patterning so as to be smaller than the periphery of the semiconductor wafer and larger than the device surface. It can be removed with high accuracy.

  According to the present invention, since the penetration of the etching solution into the device surface and the wafer outer peripheral portion accumulation can be prevented, the device is not damaged.

  In addition, there is no variation in the outer periphery of the wafer, chipping is unlikely to occur, yield is improved, and variation in orientation flats and notches is not affected. Nothing will happen.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to this embodiment.

(First embodiment)
FIG. 1 is a cross-sectional view showing a state in which a semiconductor wafer device protective material according to this embodiment is formed on a semiconductor wafer device surface. In FIG. 1, 12 is a semiconductor wafer, 11 is a device surface on the semiconductor wafer 12, and 10 is a protective material (protective film) for protecting the device surface 11.
It is preferable that the protective material 10 has excellent chemical resistance, can be selectively removed only at the outer peripheral portion with high accuracy after formation, and can be easily removed after the polishing process. For example, a cyclized rubber-based resin is preferable because it can be coated at room temperature and has excellent resistance to an etching solution.

  As the cyclized rubber-based resin, a negative photoresist conventionally used in photolithography can be used. An example is OMR-83 (negative resist) manufactured by Tokyo Ohka Kogyo. In the case of using OMR-83, coating is first performed with a spinner and then dried with an oven to form an etching protective film.

  Next, as shown in FIG. 2, the photosensitive cyclized rubber is exposed using a photomask 21 that is larger than the device surface 11 and that strikes light 20 inside the wafer outer peripheral portion (peripheral portion). Reference numeral 22 denotes a device region whose surface is the device surface 11.

  Then, the photosensitive cyclized rubber is developed using an OMR developer (manufactured by Tokyo Ohka Kogyo Co., Ltd.) so that it is slightly smaller than the semiconductor wafer 12 and protects the device surface as shown in FIG. The formed cyclized rubber is formed with high accuracy.

  As described above, the semiconductor wafer device surface protective material 10 is formed on the semiconductor wafer device surface 11, and the back surface thereof is polished. That is, as shown in FIG. 4, the rotating shaft 42 is rotated at 1000 rpm while the semiconductor wafer 12 is held from the protective material side by a vacuum chuck as the wafer fixing base 41, and hydrofluoric acid and nitric acid are mixed from the back side of the semiconductor wafer. A system etching solution 40 is dropped.

  As shown in FIG. 5, since the protective film 10 protects the surface side of the semiconductor wafer 12 on which the device surface is formed, the immersion of the etching solution 50 (40) does not occur. Further, even when the thickness of the wafer is extremely thin, since there is no protective material in the beveling portion of the wafer, no etching solution pool occurs in the wafer outer peripheral portion, and the wafer outer peripheral portion does not vary. 5 corresponds to an enlarged view of the portion A after etching in FIG.

(Second Embodiment)
FIG. 6 is a schematic view of a second embodiment of the present invention. The present embodiment is different from the first embodiment in that the device surface protective layer has an adhesion improving layer 70 for improving the adhesion between the wafer device surface and the device surface protective layer, and the device surface protective layer thereon. 10 is a two-layer structure forming 10.

  The adhesion improving layer 70 is provided to improve the adhesion of the device surface protective layer 10 to be formed later with respect to the device surface, is resistant to an etching solution, and Adhesion is good. In addition, the device surface protective layer has good adhesion. That is, as compared with the case where the cyclized rubber 1 layer is used as the device surface protective layer described above, the adhesion with the device surface is further improved.

  As a material for the adhesion layer, any material satisfying the above-mentioned requirements may be used. Among them, the polyetheramide resin is particularly preferable because of excellent acid / alkali etching resistance.

  As the polyetheramide resin, for example, HIMAL HL-1200 (manufactured by Hitachi Chemical Co., Ltd.) can be used, and this is coated with a spinner to a thickness of 2 μm and then dried, and then the cyclized rubber which is a device surface protective layer Form.

  After patterning the outer periphery of the cyclized rubber with a desired shape with high accuracy, the polyether amide resin as the adhesion improving layer is patterned using the pattern as a mask. The patterning of the polyetheramide resin can be performed by dry etching.

  As described above, even when the device surface protective film has a two-layer structure of a layer having a function of improving adhesion and a layer having excellent chemical resistance, the same effect as that of the first embodiment can be obtained.

  The present invention relates to a semiconductor wafer which is required to prevent the etching liquid from penetrating into the device surface and the peripheral portion of the wafer, for example, the production of a heater board for an ink jet printer utilizing bubbles generated by heating an ink liquid Can be used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 conceptually shows a process for forming a semiconductor wafer device surface protective film for explaining a first embodiment of the present invention, and is a cross-sectional view of a semiconductor wafer when a protective film is applied. It is a figure which shows notionally the process of forming the semiconductor wafer device surface protective film for explaining 1st Embodiment of this invention, and shows a protective film exposure process. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 conceptually shows a process of forming a semiconductor wafer device surface protective film for explaining a first embodiment of the present invention, and is a cross-sectional view of a semiconductor wafer when developing a protective film. It is a figure which shows notionally the process of forming the semiconductor wafer device surface protective film for demonstrating 1st Embodiment of this invention, and shows a spin etching process. It is a figure which shows notionally the process of forming the semiconductor wafer device surface protective film for demonstrating 1st Embodiment of this invention, and shows the mode of the wafer edge part in a spin etching process. The semiconductor wafer device surface protective film for describing 2nd Embodiment of this invention is shown notionally, and is sectional drawing of the semiconductor wafer at the time of protective film development.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor wafer device surface protective film 11 Device surface 12 Semiconductor wafer 20 Light 21 Photomask 22 Device area 40 Etching liquid 41 Wafer fixing base 42 Rotating shaft 70 Adhesion improvement layer

Claims (2)

In the device surface protective film forming method of a semiconductor wafer, a protective film for forming a protective film for protecting the device surface of the semiconductor wafer from an etchant in a spin etching step after the device is created on the semiconductor wafer ,
Covering the device surface with an adhesion improving layer containing a polyetheramide resin for improving the adhesion between the device surface and the protective film,
After covering the adhesion improving layer with a cyclized rubber-based photoresist that can be formed by coating as the protective film, the protective film is smaller than the periphery of the semiconductor wafer by patterning using photolithography, and Forming over the device ;
A device surface protective film forming method , wherein the adhesion improving layer is patterned by dry etching using the patterned protective film as a mask . 2. After forming a protective film on one main surface of a semiconductor wafer formed with a device by the device surface protective film forming method according to claim 1 , the other main surface of the semiconductor wafer opposite to the side on which the protective film is formed A method for polishing a semiconductor wafer, characterized by spin etching.

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