JPH01147840A - Clamping jig - Google Patents

Abstract

PURPOSE:To perform a finer convergent optical system and to avoid a danger of mixing it with other substance by forming the body of a clamping jig of the same material as that of an object to be irradiated, and providing protrusionlike contacts for holding electric contacts with the object to be irradiated at the jig body. CONSTITUTION:A clamping jig is formed of an upper retaining plate 1, a lower retaining plate 2 and protrusions 3 formed as an integral structure with the plates 1, 2 and in electric contacts with a semiconductor wafer 4. The wafer 4 is interposed between the plates 1 and 2 to be held from both sides thereof, thereby holding fixedly the wafer 4, and the protrusions 3 are simultaneously in electric contacts with the wafer 4. A silicon crystalline wafer having the same material as that of the wafer 4 is employed as the plates 1, 2. Thus, a finer convergent optical system can be achieved, and a danger of mixing it with other substance is avoided.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to irradiation equipment for various ions, electron beams, etc. used in the manufacturing process of semiconductor devices, and in particular to a clamp jig for fixing a semiconductor wafer, which is an object to be irradiated. Regarding ingredients.

[Conventional technology]

Generally, this type of charged particle beam irradiation apparatus has a charged particle source 21. Electromagnetic coil 22° moving stage 24. It has a clamp jig 25 and a clamp hook 23 for setting the clamp jig 25 on the moving stage 24. The clamping jig used in this charged particle beam irradiation device is made of copper or stainless steel because it requires low electrical power to release the charge generated by the irradiated charged particle beam and high processing accuracy. The silicon wafer 4 was mounted on a clamping jig 25 with a wafer presser spring 26, as shown in 2nd [1ftl(a)]. Further, the clamping jig is also required to be made of a non-magnetic material. This is to eliminate the influence of magnetic fields in order to accurately perform microfabrication smaller than the wavelength of light, and also to improve the accuracy of fixing the irradiation target.
It is necessary to ensure a sufficient amount in the design of the particle beam optical system.

[Problem that the invention seeks to solve]

The conventional metal clamp jig described above is shaped by one machine cutting process. Machining accuracy at that time becomes a technical issue. A clamp jig used in a charged particle beam irradiation device needs to have not only a mechanical fixation/holding function but also an electrical contact mechanism with the irradiation target.

In order to make good electrical contact, a sharp needle-like tip is used. As for the reason.

This is because even if the overall pressure is small, a large contact pressure can be obtained locally at the tip.

However, from the viewpoint of processing accuracy, it is difficult to manufacture the above-mentioned protrusion shape with an integral structure by cutting metal, and generally a wafer holding spring 26 as shown in FIG. 2(b) is used. It was screwed onto a clamp jig and used as an electrical contact. However, in the additive structure,
Not only the machining accuracy of each individual but also the assembly accuracy when combining them is required, and this accuracy has to be maintained at all times during use.

Further, the wafer itself used for semiconductor manufacturing, which is the object of irradiation, is not preferably in contact with metal. it is,
Trace amounts of metal elements that adhere to the surface due to contact are diffused into the semiconductor crystal during high-temperature heat treatment during the manufacturing process.
This becomes a factor that deteriorates the electrical characteristics of semiconductor devices.

Furthermore, the material properties of the wafer and metal are different, and the modulus of elasticity, coefficient of thermal expansion, etc. do not match, which poses a problem in the design of the jig mechanism.

As mentioned above, the metal clamp jigs that have been used conventionally have many drawbacks.

An object of the present invention is to provide a clamp jig that solves the above problems.

[Differences between the invention and the prior art]

In contrast to the conventional metal processing clamp jig mentioned above.

The present invention is a silicon bond with sufficient thickness accuracy.
.

The difference is that a crystal wafer is used and the clamping jig is constructed as an integral structure.

This is because semiconductor device manufacturing has matured as an industry, and the precision of shaping the silicon crystal wafers used there, which can be called the raw material, is supported by extremely advanced technology.

Using slurry polishing and chemical etching methods, these wafers have achieved high wafer thickness accuracy on the order of several units, which is required for charged particle beam irradiation equipment, even for large diameter wafers such as 8 inches and 10 inches. be.

[Means for solving problems]

The present invention provides a clamp jig for fixing an irradiation target to be irradiated with a charged particle beam. This clamp jig is characterized by having a protruding contact portion that maintains electrical contact.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

(Example 1) FIG. 1 is a perspective view showing Example 1 of the present invention, and FIG. 3 is a sectional view thereof.

In the figure, the clamp jig is an upper presser plate 1.

It consists of a lower holding plate 2 and a protrusion 3 that is integrally formed with these holding plates 1 and 2 and makes electrical contact with the semiconductor wafer 4.

By sandwiching the semiconductor wafer 4 from both sides with the upper presser plate 1 and the lower presser plate 2, the semiconductor (silicon) wafer 4 is fixedly held, and at the same time, the protrusion 3 makes electrical contact with the semiconductor wafer 4.

FIG. 4 is an enlarged view of this protrusion 3. In the present invention, silicon crystal wafers of the same quality as the semiconductor wafer 4 are used as the holding plates 1 and 2, and a protrusion 3 is integrally formed on the surface of the wafer 1.2. That is, a silicon crystal wafer 1.2 having an (ioo) surface is subjected to crystal anisotropic etching with a potassium hydroxide solution, and a protrusion with the (nt) plane 5 as a side surface is formed by this etching. 3 was formed.

Next, a method for forming protrusions 3 on silicon crystal wafers 1 and 2 as holding plates will be explained using FIG.

As shown in FIG. 5(a), first, the oxide film 52.52
Silicon wafers 53 as presser plates 1 and 2 having
The location of the protrusion shape is determined by patterning the resist 51 using the method.

Next, as shown in FIG. 5(b), the oxide film 52 is etched using the resist 51 as a mask. Thereafter, the cyst 51 is removed and the silicon wafer 53 is etched with a potassium hydroxide solution. The oxide film 52 serves as a mask material for etching at this time. After etching to a desired depth, the oxide film 52 is removed (FIG. 5(C)).

Upon investigation, it was found that etching at a depth of about 20 to 200 mm is effective.

One important thing about this forming method is that since the oxide film 52 remains as a mask material until the end of etching, the thickness accuracy of the original shape of the wafer is preserved at the tip of the protrusion 3. Even if the oxide film is finally removed, it can be controlled to within the order of magnitude using the silicon oxidation method used in the semiconductor manufacturing process, and the thickness can be controlled to within the order of the order of the wafer's original thickness accuracy. Now, compared to ordering several houses, it can be practically ignored.

Therefore, if the original wafer thickness accuracy is good, a clamping jig corresponding to the original wafer thickness accuracy can be obtained.

Such advantages of the present invention are brought about by an etching method that utilizes crystal anisotropy. (11
1) The etching speed of the (100) surface is about 2 to 3 orders of magnitude slower than that of the (100) surface, so it is possible to
Etching progresses in the depth direction with an angle of 54.7° between the (111) plane and the (100) plane.

Therefore, even if metal is etched in the same manner, for example, it is etched isotropically, so that the shape of the tip of the protrusion is eroded as it progresses in the depth direction due to the so-called side etch effect.

(Example 2) FIG. 6 is a sectional view of Example 2 of the present invention. Normally, the n-type silicon wafer 63 used in semiconductor manufacturing contains n-type or p-type impurities, but the n-type silicon wafer 63 that is the object of charged particle beam irradiation and the wafer used in the clamping jig according to the present invention is a p-type, and the types of impurities are different.

The configurations of the p-type silicon wafer 61 as the upper holding plate and the p-type silicon wafer 65 as the upper holding plate are the same as in Example 1, but the portions having the projections 3 were doped with n-type impurities. Silicon n-type layer 62.64
has. As the doping treatment, ion implantation technology and diffusion technology using heat treatment, which are used in semiconductor manufacturing processes, can be used.

Furthermore, it is also possible to similarly create the aluminum electrode 66 using a semiconductor manufacturing process.

〔Effect of the invention〕

As explained above, according to the present invention, by using an etching method that utilizes the anisotropy of silicon crystal, a protrusion shape having a certain angle can be formed, so that thickness accuracy can be easily ensured. This has the effect of enabling a finer convergence optical system because the fluctuation in focus of the charged particle beam can be suppressed as much as possible. Moreover, unlike conventional products, the use of the same type of material as the irradiation target has the effect of avoiding the risk of contamination with other substances due to contact.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing Embodiment 1 of the present invention, Fig. 2(a)
2(b) is a diagram showing the configuration of a charged particle beam irradiation device, FIG. 2(b) is a diagram showing a conventionally used clamping jig, FIG. 3 is a sectional view showing Embodiment 1 of the present invention, and FIG. A partial diagram showing the features of the embodiment 1. Figures 5(a) and (b). (c) is a cross-sectional view showing the manufacturing method according to the embodiment of the present invention in the order of steps, and FIG. 6 is a cross-sectional view showing the second embodiment of the present invention.

Claims (1)

[Claims] (1) In a clamp jig for fixing an irradiation target to be irradiated with a charged particle beam, the main body of the clamp jig is made of the same material as the irradiation target, and the jig body is made of the same material as the irradiation target. A clamp jig characterized by having a protruding contact portion that maintains electrical contact.