JP2602866B2 - Processing of thin disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a method of processing a thin disk by forming a protective film on the back surface of a workpiece, bonding or suction-holding the back surface side, and performing polishing. It is about.

(Prior Art) For example, an elastic polishing cloth is used for a thin disk such as a Si wafer for a semiconductor (hereinafter, referred to as "workpiece") as disclosed in JP-A-62-51226. Prior to polishing, one surface of the workpiece (hereinafter referred to as “back surface”) is subjected to a protective film forming process of coating paraffin wax or pine. This protective film forming treatment is performed for the purpose of reinforcing and protecting the surface to be adhered and adsorbed at the time of the above-mentioned polishing processing. And hold it on a rotating plate.
A paraffin-based wax or the like is dropped at the center of a workpiece rotating at 0 to 5000 rpm (starting up in 0.1 to 0.5 sec), and then a uniformly distributed thin film (protective film: 10 μm or less) is obtained.

The protective film on the back surface of the workpiece thus formed is dried naturally during rotation of the rotating plate, or dried at a temperature of 50 to 100 ° C. for several tens to several hours using an oven or the like. The workpiece is pressed and fixed to the working / pressing plate using vacuum suction or a template, and is polished (see FIG. 1 (b)).

(Problems to be Solved by the Invention) However, the protective film formed by the conventional method does not sufficiently exhibit the expected function. In particular, during high-temperature and high-pressure processing, rear surface contamination and flaws occur, and the yield is improved. Some countermeasures were needed to achieve this.

This is because there is a hydrophilic group -OH on the surface of the workpiece,
On the other hand, the material for forming the protective film is an organic material and has a hydrophobic group, and a strong protective film cannot be formed because the affinity between these groups is poor, and scratches and the like have been generated by polishing. Understood.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above problems, and a polishing film is formed by forming a protective film on the back surface of a workpiece, and bonding or suction-holding the back surface side. This is a method of processing a thin disk, in which a back surface of a workpiece is subjected to a water-repellent treatment to form a post-protection film and polishing is performed (see the flowchart shown in FIG. 1A).

Here, the water-repellent treatment means a treatment for eliminating the hydrophilic group, and is eliminated by corrosion removal as shown in FIG. 2 (A) and the hydrophilic group is converted into a hydrophobic group as shown in FIG. 2 (B). It is a concept that includes both extinction. The treatment is a concept including both immersion in a certain chemical solution and placing in a certain atmosphere.

More specifically, immersing the workpiece in a chemical such as HF (hydrofluoric acid) or NH ₄ FHF (ammonium hydrogen fluoride) is to eliminate the hydrophilic group by corrosion,
Placing the workpiece in the atmosphere of (hexamethyldisilazane) is to extinguish the hydrophilic group by conversion to a hydrophobic group.

(Operation) Therefore, in the present invention, first, since the workpiece is subjected to a water-repellent treatment, no hydrophilic group is present on the back surface of the workpiece at the time of forming the protective film, and the protective film such as paraffin wax is used. The forming agent adjusts to the workpiece to obtain a strong protective film, and the polishing process is performed on the workpiece having the strong protective film.

(Example) Hereinafter, an example is described.

The Si wafer is left in the atmosphere of HMDS for 5 to 10 minutes, and as shown in FIG. 2 (b), the hydrophilic group existing on the back surface is converted into a hydrophobic group to make the surface of the Si wafer water-repellent. Thereafter, the water-repellent Si wafer was adsorbed on a rotating plate with its back surface facing upward, and liquid paraffin-based wax was dropped at the center of the Si wafer, and the rotating plate was moved to 500 rpm.
After spinning at ~ 5000 rpm to form a uniform protective film in a short time and drying naturally, this was vacuum-adsorbed to a processing / pressing plate and subjected to polishing under high temperature and high pressure. .

Therefore, the protective film strength (Kg / cm ² ), the contact angle (degree), and the water-repellent treatment time (min) of the Si wafer after the above-mentioned natural drying.
Was tested, and the results shown in FIG. 3 were obtained. By the way, in the conventional method, there is no water repellency on the surface of the Si wafer,
The contact angle becomes zero, and the strength of the protective film also becomes a value close to zero. From this, it is possible to recognize a sufficient water-repellent treatment effect in the above embodiment.

In the above embodiment, although HMDS is used, HF or
Similar effects can be obtained by using HN ₄ .F.HF.

(Effects of the Invention) As described above, according to the present invention, the obtained protective film is very strong, and a sufficient effect of the protective film can be obtained even under high temperature and high pressure processing conditions. Contamination and flaw generation can be suppressed, processing under high temperature and high pressure is possible, and productivity can be greatly improved.Since even a very thin protective film has sufficient strength, unevenness in film thickness can be reduced. In addition, a wide range of effects can be obtained, such as a reduction in the amount of a protective film forming agent used as a consumable, and a reduction in the thickness of the protective film to shorten the drying time.

[Brief description of the drawings]

FIG. 1 (a) is a flowchart of the method of the present invention, FIG. 1 (b) is a flowchart of the conventional method, FIG. 2 (a) is an explanatory diagram of disappearance of the hydrophilic group due to corrosion, and FIG. FIG. 3 is an explanatory diagram of disappearance of a hydrophilic group, and FIG. 3 is a graph showing the effect of the present invention.

Claims (1)

(57) [Claims] 1. A method for processing a thin disk, comprising forming a protective film on the back surface of a workpiece, adhering or holding the back surface side, and performing polishing, wherein the back surface of the workpiece is water-repellent. Forming a post-protection film and performing a polishing process.