JPH04124823A - Manufacture of semiconductor wafer - Google Patents

Abstract

PURPOSE:To obtain a wafer having surfaces having extremely excellent flatness through a double-side polishing method while eliminating the factor of the deterioration of yield in a post-process by forming both the surface and the rear of the semiconductor wafer in mirror surfaces having superior flatness through polishing and forming the rear in a non-mirror surface. CONSTITUTION:Both the surface and the rear of a semiconductor wafer are formed in mirror surfaces 2, 3 having excellent flatness through polishing, and the rear 3 is formed in a non-mirror surface 6. A double-side mirror-surface wafer 1 having superior flatness is manufactured through a double-side lapping- polishing method. An etching protective film 4 is formed onto the surface 2 by a photo-resist, etc. When the wafer 1 is exposed in an etching gas atmosphere 5 such as air containing 10-1000ppm HF and NH3 and is left for one to tens of hours under the state, a section not protected by the resist 4, a silicon surface mainly using the rear 3, is finished in the non-mirror surface 6. Lastly, when the wafer 1 is extracted from said atmosphere and washing and the removal of the protective film 4 are conducted, the wafer 1 having the surface as the mirror surface and the rear 3 as the non-mirror surface 6 is acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming the front and back surfaces of a semiconductor wafer, particularly a silicon wafer.

(Prior Art) As is well known, silicon wafer manufacturing is performed through the following steps.

Preparation of silicon polycrystal - single crystal pulling - one slice → beveling - lapping - etching → polishing → cleaning Of these steps, the one that is relevant to the present invention is the lapping-polishing process to flatten the surface of the wafer and make it mirror-like. , the conventional method for that part will be explained below.

FIG. 2 shows the configuration of the wrapping device, and the double-sided simultaneous wrapping and living method shown in FIG. 2(b) is usually used. This is because in the single-sided lapping method shown in FIG.
3 has a point that is not completely parallel, and that plate 1
This is because the wafer 3 and the lapping plate 12 are not completely parallel to each other, resulting in poor wafer flatness (usually referred to as TTV) after lapping. The main reason for poor TTV is that the surface of the sea urchin is finished in a tapered shape.

In the double-sided simultaneous lapping method shown in FIG. 12(b), the upper lapping plate 15 and the lower lapping plate 14 rotate in opposite directions, and the carrier 16 rotates on its own axis while being sandwiched between them, resulting in a finished wafer 11 with extremely good flatness.

That is, a lap wafer with a TTV of 1 μm or less can be easily manufactured.

After this lapping process is completed, etching is performed using a chemical solution to remove processing distortion caused by lapping.

Next, a bonoshing process is performed to finish the surface of the wafer to a mirror finish. This polishing method also includes a single-sided polishing method and a double-sided polishing method, and the single-sided polishing method is currently used. The device has the same configuration as the lapping device described above, so it will not be described here, but the double-sided polishing method produces wafers with good flatness for the same reason as the double-sided lapping method. Figure 3 (a) shows an example of measuring the TTV value of a single-sided polished wafer, and Figure 3 (b) shows an example of measuring the TTV value of a double-sided polished wafer. is small. This is due to the small taper component of the wafer surface. However, in the double-sided polishing method, the back side also becomes a mirror surface, which causes the following problems and is not currently in practical use. That is, (a) since both the front and back surfaces of the wafer are mirror surfaces, it is difficult to distinguish between the front and back surfaces.

(b) In a manufacturing apparatus that vacuum-chucks the back side, a wafer that has been vacuum-suctioned to a certain degree may not separate from the stellar (chuck) even after the vacuum is turned off.

(C) Various jigs and tools are used during the manufacturing process, and the back surface becomes conspicuously contaminated due to contact with them.

(d) In an exposure device such as a stepper, minute particles adhering to the back surface of the wafer cause the back surface of the wafer to become locally convex, causing pattern defects and reducing yield.

(Problems to be Solved by the Invention) As mentioned above, the double-sided polishing method has good surface flatness, but has many problems, so it is not used, and the currently used single-sided polishing method is shown in Figure 3 (a). As shown in the figure, the flatness is poor. As you can see in the figure, the future 16M”
The TTV value of MAX 2 μm or less required for DRAM etc. has not been achieved. This TTV is large because the taper component of the wafer surface is large.

The present invention aims to solve both of these drawbacks, and provides a method for achieving good flatness (and a non-mirror surface on the back surface).

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a mirror-finished wafer with good flatness by polishing both sides of the wafer, and then etching it in an etching gas atmosphere ( It is made to have a non-mirror surface in HF-based gas).

(Function) As described above, in the present invention, the wafer is first polished to a mirror surface on both sides, and then only the back surface is made into a non-mirror surface, so the flatness is extremely good, and the back surface has the mirror surface as described above. The drawbacks caused by this can be resolved.

(Example) FIG. 1 shows a process sectional view of an example of the present invention, and the explanation will be given below.

First, as shown in Figure (a), a double-sided mirror-finished wafer l with good flatness is fabricated by the well-known double-sided lapping and polishing method described in the prior art section.

Next, as shown in (b), an etching protective film 4 is applied to the surface 2.
Add. This is to protect the front surface 2 from chemicals or gas that will make the back surface 3 of the wafer l a non-mirror surface in the next step. In this embodiment, since HF gas was used for non-specular etching, the protective film 4 was formed with a resist used in a photolithography process. Of course this protective film 4
This is suitable for the method of making a non-mirror surface, and is not limited to the above-mentioned resist.

Next, as shown in FIG.
exposed to air containing pp. If left in this state for one to several tens of hours, the silicon surface, mainly the part not protected by the resist 4, that is, the back surface 3, will be finished in a non-mirror surface, which is usually called "(mori)". This is due to the following reaction.

(1) HF reacts with the natural oxide film (SiO21) on the silicon surface to form H25iFa +Hz O.

(2) This H2SiF6 and NH3 react, and (NH4
)2SiF6.

(3) (NH4)2SiFe retains H2O until it is completely crystallized, so HF in the atmosphere penetrates into the SiO2 at a high concentration and etches the SiO2.

(4) In the process of etching SiO2, minute etch bits are generated, resulting in a non-mirror surface state 6.

A natural oxide film may be used to obtain a non-specular surface 6 through this reaction, but
It is more effective to grow 5in2 of 50 to 100 people in advance.

Finally, the wafer 1 is removed from the atmosphere, cleaned, and the protective film 4 is removed. As shown in FIG. .

In this example, a gas atmosphere was used to make the back surface a non-mirror surface, but the method is not limited to the one used in this example, and any known method such as laser scanning or particle spraying may be used.

(Effects of the Invention) As explained above, according to the present invention, it is possible to provide a wafer having an extremely flat surface using a double-sided polishing method, and since the back surface is made non-mirrored, it is possible to reduce the yield in subsequent steps. The problems with the double-sided polishing method described in the prior art section can be solved.

Therefore, it will greatly contribute to improving the yield of submicron VLSI manufacturing, which will develop in the future.

[Brief explanation of the drawing]

Fig. 1 is a process cross-sectional view of an embodiment of the present invention, Fig. 2 is a configuration diagram of a lapping device, and Fig. 3 is a TT of a polished wafer.
This is an example of V measurement. l...-...Wafer, 2-......
Front side, 3... Back side, 4...
...Protective film, 5... Etching gas atmosphere, 6... Back surface (non-mirror surface). Figure 1 Pressure Man○ (0) Crucian carp face Uzo〔'unk゛(b) Both sides same place rappisig'

Claims (3)

[Claims] (1) A method for manufacturing a semiconductor wafer, which comprises polishing both the front and back sides of the semiconductor wafer to make it a mirror surface with good flatness, and then making the back surface a non-mirror surface. (2) Claim 1 characterized in that the means for making the mirror surface non-mirror includes exposing it to a gas atmosphere in which the mirror surface is etched.
A method of manufacturing the semiconductor wafer described above. (3) The method for manufacturing a semiconductor wafer according to claim 2, wherein a mixed gas of HF and NH_3 is used as the gas atmosphere.