JPS59227127A - Chemical polishing method - Google Patents

Abstract

PURPOSE:To enable the attainment of the uniform flatness of a sample, by fixing a polishing cloth, by disposing the sample in a vessel filled up with an etching solution, and by rotating the sample so that it can be in contact with the polishing cloth. CONSTITUTION:A pallet 12 with a polishing cloth 13 stuck thereon is fixed on the bottom surface of a vessel 11, while a holder 14 which moves vertically and has a rotation mechanism is made to hold a semiconductor wafer 15. Then, the holder 14 is lowered and dipped in an etching solution 16 filled up in the vessel 11 so that the surface of the semiconductor wafer 15 can be in contact with the polishing cloth 13 under a prescribed pressure. Next the holder is rotated, and thereby the wafer 15 is polished. According to this method, the solution 16 is supplied constantly onto the polished surface of the wafer 15, and thus the flatness of the polished surface can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of the Invention The present invention relates to an etching process applied to a sample such as an integrated circuit board, and particularly relates to a copper plating chemical polishing method effective for obtaining uniform flatness of a processed surface. .

(1)) Background of the technology One of the wet carborizing methods applied to semiconductor wafers.
There is a steel plating polishing method using a mixed solution of NH, F) or its hydrogen salt (NH, FHF). The feature of this is that the silicon of the substrate is dissolved in NH and F, and when the silicon is dissolved in the solution as a silicate, the silicon surface is plated with copper. This copper plating layer is removed by a rotating polishing cloth, and the electrochemical reaction proceeds continuously to polish the silicon. This polishing method can easily give a silicon surface a so-called mirror finish with a smoothness of 1 μm or less, and can be processed at high speed. In general, silicon has strong chemical properties, and its etching solution mainly consists of a strong oxidizing agent and an acid that dissolves the oxidizing substance.

(C) Prior Art and Problems FIGS. 1 and 2 are schematic diagrams showing a conventional chemical polishing apparatus. FIG. 1 is a fllj ffi diagram, and FIG. 2 is a plan view.

In the figure, a rotary table 3 to which a soft polishing cloth 4 is fixed is provided in a clean booth 2 maintained in a clean atmosphere. A chemical polishing apparatus 1 is provided with a wafer holder 5 which moves up and down and holds a semiconductor wafer 6, and an etching liquid supply conduit 7 which supplies an etching solution. The etching liquid supplied from the etching liquid supply conduit 7 is diffused onto the polishing cloth 4 and etches the surface of the semiconductor wafer 6 in contact with the polishing cloth 4 under a predetermined pressure. The etching solution used is copper nitrate: Cu (NOa)! A mixed solution of ammonium fluoride and NH4F is used, and its chemical reaction formula is expressed as %4NH,↑+2Cu+4HNOs. Silicon is hexafluorosilicate: (N)1. )
t Dissolved in solution as SiF6, ammonium: 4
Immediately, vaporized copper:2CLl and nitrogen:4HNOs are obtained. From this step K, the surface of the semiconductor wafer 6 is once copper plated, but the plated copper (2Cu) is removed by the rotating polishing cloth 4. this? l? Boring treatment is performed by repeating the chemical reaction. In addition, the etching solution contains hydrogen fluoride (HF) as a reaction accelerator and water (H!) as a reaction inhibitor. O, and silicon carbide SiC may be used as the polishing medium.

However, such a busy chemical polishing equipment f! At tl, the etching solution is not uniformly supplied to the six surfaces of the semiconductor wafer, resulting in poor polishing cloth smoothness. A specific example is shown in figure v3.

The amount of etching at the periphery of the polished surface 6a of the semiconductor wafer 6 is larger than that at the center, resulting in a convex shape, which is not preferable for obtaining semiconductor elements.

(d+ OBJECTS OF THE INVENTION The present invention aims at providing a chemical polishing method capable of obtaining uniform flatness in wet chemical polishing for spinning semicircular wafers.

(e) The object of the present invention is to fix a polishing cloth, place a sample in a container filled with an etching solution, give the sample a busy rotation, and apply a constant pressure to the polishing cloth. This is achieved by polishing the main surface of the sample by bringing it into contact with the etching solution and electrochemical reaction of the etching solution.

(f) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 4 is a block diagram showing a chemical polishing method according to an embodiment of the present invention. A pedestal 12 on which a soft polishing cloth 13 is attached is fixed to the bottom of a container 11 made of a chloride-based acid-resistant synthetic resin such as vinyl chloride. The semiconductor wafer 15 is held in a holder 14 having a rotating mechanism and a flexible head, and the holder 14 is lowered and immersed in a container 1 filled with an etching solution 16, and the semiconductor wafer 15 is moved downward. The surface of the polishing pad 15 is brought into contact with the polishing cloth 13 with a constant pressure. Then holder 1
The structure is such that the etching solution 16 is used for etching and polishing by applying low speed rotation to the wafer.
Milc is constantly supplied, and etching is not uneven due to variations in the supply temperature as in the past, and the etching is smooth.

In this example, in order to remove 50μ of a single crystal silicon substrate, the contact pressure s O ~ 1001r/ is rotated by 3Or, p, m.
It took about 10 m1n to obtain a good etched surface.

Although there is an HF copper plating layer in the boring process of the wafer 15, it is easily removed by the balance cleaning process. A shower with nitric acid may be used before the water purification process.

In this example, we have explained Borisingken FNK, a single crystal silicon solution in a silicon substrate. , when forming an epitaxial layer with a rate of [7
Of course, this method is effective for etching to finish the wafer surface to a fine surface. For condensation of this general etching solution, an etching solution containing nitric acid (NHO, hydrogen fluoride (HF)) in a volume ratio of 5:1 is used.

(g) Effects of the Invention As mentioned above, by using the chemical polishing method of the present invention, the number of surfaces to be polished is divided into four. Moreover, since the etching liquid is constantly supplied, high-speed processing can be expected, and it is particularly effective for back polishing of semicircular wafers on which elements have been formed.

[Brief explanation of the drawing]

Figure tP1 and Figure 2 are drawings showing the conventional chemical polishing method, Figure 1 is a side view, Figure 2 is a plan view, Figure 3 is a sectional view showing a conventional example of the shape of a semiconductor wafer after polishing, W
Figure 4 shows a chemical polishing method according to an embodiment of the present invention.
◇ In the diagram, 11...container, 12... pedestal, 1
3... Polishing cloth, 14... Holder, 1
5... Semiconductor wafer, 16... Etching acid.

Claims (1)

[Claims] A polishing cloth is fixed, a sample is placed in a container filled with an etching solution, the sample is rotated, and the polishing cloth is made to cut at a constant pressure. A chemical polishing method characterized by polishing the surface.