JPH02277234A - Dry etching - Google Patents

Abstract

PURPOSE:To obtain a pattern of a desired shape by a method wherein a mask material having an ionic bond is used and a temperature of a substrate is controlled to a value within a specific range. CONSTITUTION:A film 42 to be etched of Al or an Al alloy in which a mask pattern 43 has been formed on the rear is processed by using a plasma of a reactive gas containing SiCl4. In this method, a second electrode 2 is placed at an upper end of a vacuum container 1 and a first electrode 3 is attached so as to face the second electrode 2. A substrate 41 on which the mask pattern 43 and the film 42 to be etched have been installed is placed on the first electrode 3; electric power generated by a high-frequency power supply 5 is applied via a matching circuit 6. The mask pattern 43 is constituted of a material having an ionic bond; the substrate 41 on which the film to be etched 42 has been formed is kept at -13 deg.C or higher and 20 deg.C or lower. Thereby, an etching shape can be controlled more satisfactorily and can be processed with high accuracy; it is possible to form the pattern of a desired shape without a taper.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a dry etching method for manufacturing semiconductor devices, and particularly to a method for performing dry etching with good selectivity.

(Prior Art) In recent years, semiconductor integrated circuits have undergone rapid development, and now even LSIs having submicron-sized elements are being prototyped. In such L8I, a technique called etching, which is a technique for forming fine elements such as transistors and capacitors, and wiring patterns in a thin film, is important as a basic technique. In this etching process, as shown in FIG.
Etching is performed by leaving only the part below it and exhausting the other parts of the workpiece and etching material as a gas with high vapor pressure through a chemical reaction with a reactive gas. In this method, highly reactive atomic and molecular ions 44 are removed from plasma generated near the substrate in order to prevent etching (undercut) 43 below the mask.
By pulling out the mask and irradiating it directly onto the substrate Kfl, it is possible to process the mask with vertical sides and through the dimensions of the mask.

However, even mask materials that have an energy of about 2 ooav and are resistant to ions and reactive gases that irradiate the substrate undergo etching due to sputtering, and when the material to be etched is thick, opaque etching is often required. In such a case, as shown in FIG. 6, the mask edge 46 begins to retreat, and the etching shape may become tapered 47 or the pattern may disappear. Furthermore, decomposition products of one mask material, such as C, CH, and Co in the case of a photoresist, and its constituent elements, 81, and O in the case of a SiO hemorrhoid mask, are released and do not affect etching. In particular, when the pattern is coarse or dense, there is a problem in that the characteristics change between the coarse and dense parts, or the characteristics completely change depending on the level of resist coverage.

(Ha to be solved by the invention) As described above, in the conventional dry etching method, since the etching rate ratio (selectivity) of the material to be etched to the mask material is low, when etching is performed,
When the material to be etched has a tapered shape, the pattern is lost and the desired shape cannot be obtained.

An object of the present invention is to provide a dry etching method that solves these problems.

[Structure of the invention]

(Measures to Solve the Problems) The present invention has been made in view of the above circumstances, and is a method for forming a mask pattern on a surface using plasma of a reactive gas containing at least 5tcz. is a method for processing a film to be etched of M alloy, characterized in that the mask pattern is made of a material having an ionic bond, and the substrate on which the etching film is formed is maintained at a temperature of -13°C to 20°C. A dry etching method is provided.

(Function) As described above, the present invention uses a mask material having ionic bonds, uses a gas that generates molecules (deposition species) having ionic bonds and an unsaturated structure as an etching gas, and etches the substrate. This is a method of etching materials that do not have or have weak ionic bonds by controlling the temperature. Therefore, the adsorption probability of the deposited species generated from the etching gas is greater on the mask surface than on the material to be etched, and as a result, etching of the mask is suppressed and a high selectivity can be obtained.

The principle of the present invention will be explained in more detail as follows.

Only 8iCz was used as the etching gas, and the gas pressure was 0.
, 05 TOrrXRI F' power 0.5W/io Macneto I:1 discharge device was used. The substrates to be etched include S l , At, S iO,, AL, o,
, 5isN4, BaF', , vsis) (C-
0, one composed of a C-H bond) was used. 5r
CT gas, which is commonly used as an etching gas for these materials, forms a deposited film on a cooled substrate. FIG. 3 shows the results of investigating at what point a deposited film starts to be formed when the substrate temperature is lowered for these materials. The horizontal axis shows the difference in electronegativity of the elements constituting each material, that is, the value corresponding to the strength of ionic bonds, and the vertical axis shows the temperature at which deposition begins, that is, etching occurs at temperatures higher than this temperature, and etching occurs at lower temperatures. is the temperature at which deposits form. As a result, it was found that materials with strong ionic bonds form deposited films at extremely high temperatures. These are 8LCt and 5ect, which are considered to be deposited species.
This shows that materials that have strong ionic bonds and are electrically polarized are more likely to be adsorbed. That is, as schematically shown in FIG. 4, it is thought that the 5t-ct, which is thought to be electrically polarized, and the substrate to be etched are attracted to each other by Coulomb force, and as a result, the probability of adsorption increases. Therefore, the present invention is achieved by selectively adsorbing electrically polarized deposited species having ionic bonds onto the surface of the substrate to be etched, which is also polarized and has nine bonds. By selectively etching various materials such as semiconductors made of a single element such as St, metals such as M, or materials with relatively weak ionic bonds, the selectivity can be improved.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic diagram showing a dry etching apparatus according to an embodiment of the present invention. At the upper end of the vacuum vessel 1 there is a second electrode 2 . A first electrode 3 faces this second electrode 2.
is installed. A substrate 4.on which a mask pattern 4s and a film to be etched 43 are provided on the first electrode 3.
is mounted, and power generated by a high frequency power source 5 is applied via a matching circuit 6. 9. Below the first electrode 3 is a substrate 4. A round cooling pipe 7 for cooling is provided], and cooled nitrogen gas is circulated through this cooling pipe 71. Etching of the film to be etched 41 is carried out by introducing a certain amount of reactive gas containing halogen elements such as fluorine and chlorine from the gas introduction lower, and evacuating it with a vacuum pump connected to the exhaust port 8 to maintain a constant pressure. ing. A magnet 9 is arranged outside the second electrode 2 and forms a trap to provide a magnetic field orthogonal to the electric field induced by the high frequency power applied to the second electrode 2. In this way, magnetron discharge occurs near the second electrode 2 and high-density plasma is generated. Here, load lock chamber 10.
Reference numerals 11 denote spaces for loading and unloading wafers without exposing the inside of the vacuum container 1 to the atmosphere.

Next, a dry etching method using the present invention will be explained. At-81 (1%)-Cu as the film to be etched 4
(0.5%) The results of etching the film are shown. A mask pattern 41 was formed using an ordinary novolak photoresist as a mask material, and a mixed gas of Ct and No. 8iCA (50%) was used as an etching gas. This resist is C-H, C-0 containing ionic bonds.
Furthermore, 5sct4 gas has high electronegativity of Ct, has ionic bonds, and is decomposed in plasma to form polar molecules such as 81CLl and 8iCA@. Using the device shown in Figure 2, the gas pressure is 0,
Etching was carried out under the conditions of 0.5 Torr and RF power of 0.5 W/cd, and the selectivity of the film to be etched to the resist at the time of death was investigated with respect to the substrate temperature.
As shown in the figure. At a substrate temperature of 20.degree. C., the etching profile was slightly undercut, but a selectivity of 4 was obtained. At a substrate temperature of 5° C., the selectivity was 10, and the etching shape was almost vertical. If the substrate temperature is further lowered, -
At 13°C, the selectivity ratio became 4. Also, the substrate temperature is 113
If the temperature is lower than .degree. C., the etching rate of n will drop significantly.

In this way, a selectivity of 4 or more can be obtained when the substrate temperature is 113° C. or higher and 20° C. or lower. Further, when the substrate temperature was -8 DEG C. or higher and 5 DEG C. or lower, the etching selectivity was 10 or higher and the etching shape was almost vertical.

By improving the etching selectivity using the etching method described above, the controllability of the etching shape is increased and high-precision processing becomes possible. Furthermore, since almost no etching products are generated from the mask, it is possible to eliminate the phenomenon that the etching characteristics change greatly due to mask covering, etc., which is conventional. Furthermore, the height of the mask can be reduced, and when forming a pattern with a high aspect ratio, the mask itself does not further increase the aspect ratio and make etching difficult.

Note that the present invention is not limited to the above examples and can be applied in various ways. That is, in addition to photoresist, mask materials include insulators and compounds with a relatively high proportion of ionic bonds, such as C-H and C-0tttr compounds, 8 i0
@, 81BN4, A40s'k (!: Ka6
Ru. Furthermore, similar results can be obtained when only 8iC14 is used as the etching gas.

As an etching apparatus, an apparatus using magnetron discharge was shown in the example, but it is sufficient to decompose the etching gas and form polarized unsaturated deposited species, and an ordinary parallel plate type reactive ion etching apparatus or an electron cyclotron may be used. It can be carried out in almost all etching apparatuses such as apparatuses that utilize electric discharge.

〔Effect of the invention〕

As described above, according to the present invention, by selectively depositing K on the mask material, the selectivity between K and the etching material can be improved. As a result, the controllability of the etched shape is increased and highly accurate processing becomes possible. Further, it is possible to eliminate the phenomenon that the etching characteristics change greatly depending on the coverage of the rounded conventional mask in which almost no etching products are generated. Furthermore, the height of the mask can be formed low, and when forming a pattern with a high aspect ratio, the mask itself does not further increase the 7-sphere vector ratio and make etching difficult.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a diagram for explaining an apparatus for carrying out the present invention, FIG.
FIG. 4 is a diagram for detailed explanation of the present invention, FIG.
FIG. 6 is a diagram for explaining a conventional example. In the figure, 1...vacuum container, 2...second electrode, 3...first
electrode, 4...substrate, 4 snow...film to be etched, 4
3... Mask material, 5... High frequency power supply, 6... Matching circuit, 71... Cooling pipe, 7... Gas inlet, 8... Exhaust port, 9... Magnet, 10. 11... Load lock chamber, 40... Material to be etched, 41...
・Surface of material to be etched, 42...mask pattern,
43...undercut, 44...ion, 46...
・Mask edge, 47...Tapered shape. Agent Patent Attorney Noriyuki Ken Yudo Hikaru Matsuyama

Claims (1)

[Claims] In a method of processing an etched film of Al or Al alloy having a mask pattern formed on its surface using plasma of a reactive gas containing SiCl_4, the mask pattern is made of a material having an ionic bond and A dry etching method characterized by keeping a substrate on which an etching film is formed at a temperature of -13°C or higher and 20°C or lower.