JPS6056230B2 - Reactive sputter etching method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a reactive sputter etching method.

Conventional reactive sputter etching has used an apparatus as shown in FIG. That is, an upper electrode 2 and a lower electrode 8 are provided in the reaction tube 1, and the semiconductor substrate 4 to be etched is placed on the lower electrode connected to the high frequency signal source 5.

When a reactive gas such as aluminum (Al) is not etched, boron chloride (BCI0) is blown out from a single port of the gas introduction pipe 6 and exhausted from an exhaust pipe 7. When such an apparatus is used, the etching rate at the peripheral portion of the wafer is higher than that at the central portion, resulting in non-uniform etching.

Therefore, if the central portion of the wafer is completely etched to a predetermined value, the peripheral portion may be over-etched, resulting in undercuts or excessive etching of the underlying layer.

This non-uniform etching rate is thought to be due to the fact that more radical Cl generated by the reaction gas is supplied to the periphery of the wafer than to the center, and as shown in Figure 1, Instead of flowing the reaction gas from one direction, for example, a member having many small holes may be arranged on the wafer, and the reaction gas may be uniformly supplied to the wafer from the small holes. More Cl trees generated near the wafer are supplied to the periphery of the wafer, making it difficult to equalize the etching rate.

Conventionally, as a method for eliminating such non-uniformity, it has been proposed in Japanese Patent Application Laid-Open No. 52-137266 to dispose, for example, an aluminum ring around the wafer and not perform etching.

This is because etching is performed by treating the wafer as one wafer, including the aluminum ring provided around the wafer, so that even if the aluminum ring portion is excessively etched, the inner wafer is etched almost uniformly. It was aimed at However, in this method, since a ring must be provided on each of a plurality of wafers, the etching rate for both wafers decreases when handling becomes complicated. Furthermore, since there is an aluminum ring to be etched, even if the aluminum on the wafer is etched away, the ring-shaped aluminum remains, making it impossible to detect the end point of etching using plasma emission spectra or mass spectrometry. However, there are disadvantages such as aluminum and chlorine compounds tend to adhere to the inner wall of the reaction tube, making it difficult to observe from outside the reaction tube. The present invention is intended to solve these drawbacks, and it is an object of the present invention to easily and uniformly etch a wafer.

The feature of the present invention is that the aluminum layer is etched by blowing out a compound gas containing chlorine only to the center of the wafer on which the aluminum layer is formed.

FIG. 2 shows an embodiment in which the present invention is actually applied to an etching apparatus.

In FIG. 2, the same numbers as in FIG. 1 indicate the same things.

The difference between FIG. 2 and FIG. 1 is that the ends of the gas introduction tube 6 are branched to 6'' and 6'' so that the reaction gas is blown out toward the center of each wafer. In this way, when etching is performed using the conventional method as shown in Figure 1,
A comparison with etching by the method according to the present invention as shown in FIG. 2 will be shown below. The wafer to be etched has a diameter d of 3 inches and is coated with 1 micron of aluminum.

The distance h between the upper electrode and the wafer surface is determined by the Mdl reaction gas (B
Cl3) Inner diameter of outlet 4Tfr! n1 reaction gas flow rate is 2
0sccm/sheet, vacuum degree in the reaction tube 0.1T0rr',
High frequency power supply frequency 13.56MHz, power density 0.4
The distribution of the etching rate (A/Mln) in the wafer diameter direction when etching is performed under the W/Clt condition is shown in FIGS. 3A, b, and c.

3a shows the wafer, FIG. 3b shows the distribution of the etching rate R according to the method shown in FIG. 1, and FIG. 8c shows the distribution of the etching rate R according to the method shown in FIG.

As shown in FIG. 3b, in the conventional method, the etching rate was 1000 A/Min at the periphery of the wafer, and 500 A/Min at the center, but in the method of the present invention, as shown in FIG. Therefore, the current was approximately 1000 A/Min over the entire circumference of the wafer. Therefore, when looking at the central portion, the etching rate was doubled. As described above, according to the present invention, uniform etching can be achieved on a wafer and the etching rate can be increased. The contribution is enormous.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional etching device, FIG. 2 is a diagram showing an example of an etching device to which the present invention is applied, and FIG. 3 is a comparison of etching rates between the conventional etching method and the etching method of the present invention. It is a diagram. 1 is a reaction tube, 3 is a wafer, and 6, 6'', 6'' are reaction gas introduction tubes.

Claims (1)

[Claims] 1. A reactive sputter etching method characterized in that the aluminum layer is etched by blowing out a compound gas containing chlorine only to the center of the wafer on which the aluminum layer is formed.