JPS6024050A - Manufacture of thin film element - Google Patents

Abstract

PURPOSE:To obtain the titled element of high reliability with good yield by a method wherein only the side wall surface of a stepwise difference is provided with a film having a smaller specific resistance than that of said element, when the element is formed on a substrate having the stepwise difference and thus made as an IC. CONSTITUTION:An insulation layer 2 is adhered to the surface of the semiconductor substrate 1, an aperture 5 being bored, and a metallic layer 3 of Mo or the like being then adhered to its bottom, side wall, and the surface of the substrate 1 to the same thickness by a pressure reduction CVD method. Next, the layer 6 is etched in a vertical direction by reactive plasma etching using Cl2 gas, thereby making the layer remain only at the side wall of the aperture 5, and removing the other. Thereafter, an SiO thermet film 7 containing Cr the thin film element is evaporated over the entire surface including the aperture 5, and then the film 7 is formed into a required shape by a photo processing method. Next, an electrode 8 contacting the film 2 is mounted on one end of this film 7, and the latter film including the electrode is surrounded with a PSG film 4. In such a manner, the thin film element of uniform electric characteristics is obtained by reduction of the resistance component of the following part without providing the film 2 on the side surface of the aperture 5 with inclination.

Description

Detailed Description of the Invention (a1 Technical Field of the Invention) The present invention relates to a method for forming a circuit element made of a thin film on a substrate, and in particular to a method for forming a circuit element made of a thin film on a substrate, in particular a method for forming a circuit element made of a thin film on a substrate having steps, and in particular, a method for forming a circuit element made of a thin film on a substrate with stable and predetermined electrical characteristics. The present invention relates to a method of forming a thin film device having the following.

(Background of BL technology Typical examples of thin film elements in semiconductor integrated circuits include resistive elements for connecting a large number of semiconductor elements that make up the semiconductor integrated circuit with a predetermined resistance value, or some unnecessary elements. Examples include a fusion cutting element for electrically disconnecting.

(C1 Prior Art and Problems) An outline of the structure of the thin film element in a semiconductor integrated circuit is shown in FIG.
2) is formed. An opening (contact hole) is provided in a part of the insulating layer 2, and one end of the thin film element 3 is connected to a predetermined terminal of the semiconductor circuit element in the opening, and the other end is connected to a predetermined terminal of the semiconductor circuit element in the opening. For example, it extends to another opening (not shown) and is connected there to a predetermined terminal of another semiconductor element, or to an electrode for external extraction. After energization and formation of the thin film element 3, a protective film 4 is provided on the surfaces of the thin film element 3 and the insulation N2.

An overview of the conventional general manufacturing method for thin film elements will be explained using a thin film resistive element as an example, again using FIG. 1.

First, an insulating layer 2 made of silicon dioxide (SiO2), for example, formed on a semiconductor substrate 1 is processed into a predetermined pattern using a well-known photo processing technique.
For example, a silicon monoxide (SiO) film containing chromium (Cr) (commonly known as a cermet film) is deposited over the entire surface of the cermet film, and the cermet film is similarly processed using photoprocessing technology. Thin film resistive element 3 with a predetermined pattern
form.

Aluminum (
A1) etc. are deposited and processed into a predetermined shape by photo processing or the like to form electrodes (not shown).

Thereafter, a film of phosphosilicate glass (PSG) or the like is formed on the surface of the thin film resistance element 3 and the entire exposed surface of the insulating layer 2 by, for example, CVD (chemical vapor deposition) to complete the production of the thin film element. .

In the thin film element formed by the above manufacturing method, normal conduction is generally not achieved due to the low coverage (i.e., small film thickness) of the thin film at the stepped portion of the insulating layer 2 (the side wall of the opening). This causes problems such as being difficult to obtain or easily breaking when energized. In addition, in the case of a thin film resistive element, problems arise such that the resistance value becomes larger than a predetermined value and the variation thereof tends to increase. These problems cause not only a decrease in yield during the manufacture of semiconductor integrated circuits using thin film elements, but also a decrease in reliability after mounting on a device.

Conventional countermeasures to the above problems include (i>
When forming the opening in the insulating layer 2 using photo processing technology, the etching conditions are mainly controlled so that the insulating layer 2 is etched so that the side wall of the opening forms an inclined surface, and then a thin film is deposited. Alternatively, (ii) a thin film is deposited while rotating and revolving the deposition target to increase the coverage on the side wall.

However, as the degree of integration in semiconductor integrated circuits increases, the size of the opening becomes smaller, for example, the diameter is about 1 to 1.5 μm. On the other hand, the thickness of the insulating layer 2 is about 1 μm. For this reason, it has become difficult to obtain sufficient effects using the conventional methods described above.

In other words, in order to ensure reliable contact between the substrate semiconductor 1 and the thin film element 3 at the opening, it is necessary to secure a certain area or more at the bottom of the opening, and on top of that, the sidewalls must have a sufficient slope. When trying to provide a thin film element and other wiring on the surface of the insulating layer 2, the method (i) above increases the proportion of the opening. This further restricts the integration density of semiconductor elements formed on the substrate semiconductor 1. In other words, there is a limit to the angle of inclination that can be given to the side wall. In addition, in the method (ii) above, in the relationship between the film thickness of the insulating layer 2 and the opening diameter as described above, the incident angle of the vapor deposit with respect to the side wall (the angle formed between the side wall and the incident direction of the vapor deposit) is It cannot be made sufficiently large, and the effect of improving the coverage rate is difficult to be seen in the side wall portion near the bottom of the opening.

For the above-mentioned reasons, there has been a demand for the development of a method for manufacturing thin film elements that can cope with higher integration of semiconductor integrated circuits.

(d1 Purpose of the Invention The present invention aims to make it possible to manufacture a highly reliable thin film element having predetermined characteristic values and with high yield substantially regardless of the dimensions of the insulating layer and the opening. .

(e) Structure of the Invention The present invention is characterized in that when a thin film element is formed on a substrate having a step, a film having a resistivity smaller than that of the thin film element is formed only on the side wall surface of the step.

(f) Embodiments of the Invention Below, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same parts as in FIG. 1 are designated by the same reference numerals.

FIG. 2 is a diagram showing an outline of the method for manufacturing a thin film element according to the present invention, and schematically shows the cross-sectional structure of the thin film element at the main process steps.

First, in the same manner as in the conventional method, an opening (contact hole) 5 is provided in a part of the insulation N2 formed on the substrate semiconductor 1, and then the insulation layer 2 and the opening 5 are formed.
A metal layer 6 of, for example, molybdenum (Mo) is formed over the entire surface (FIG. 2(A)).

In this case, a feature is that the metal layer 6 is formed using a method that provides a high coverage rate (a method that causes a large wrap-around phenomenon). As a result, the metal layer 6 on the side wall surface of the opening 5 has approximately the same thickness as that on the surface of the insulating N2 and the bottom surface of the opening 5.
will be covered. For example, a low pressure CVD (chemical vapor deposition) method is suitable as a film forming method that provides the above-mentioned high coverage.In order to form MoNPA as the metal layer 6, for example, a mixed gas of molybdenum hexachloride (MoC16) and hydrogen is used. Alternatively, a tungsten (W) film can be formed by using, for example, a mixed gas of tungsten hexafluoride (WF6) and hydrogen.

Selective etching is performed in a direction perpendicular to the entire surface of the metal N6 formed as described above. Suitable selective etching methods include, for example, reactive plasma gas etching or ion etching under an electric field applied in the vertical direction. In the former case, when the metal layer 6 is made of Mo or W, chlorine gas or fluorine gas may be used, and in the latter case, argon gas may be used. In the manner described above, selective etching is performed to exactly correspond to the film thickness of the metal layer 6 to obtain a structure in which the metal layer 6 remains only on the side wall of the opening 5.
Figure 2 (B)].

Next, a film for forming a thin film element, for example, a cermet film 7 made of silicon monoxide (SjO) containing chromium (Cr) is formed by vapor deposition over the exposed insulating layer 2 and the entire surface of the opening 5 (see FIG. 2). C)].

Thereafter, as in the conventional method, the cermet film 7 is processed into a predetermined pattern using a photo processing method [Fig. 2 (D)].
For example, after forming an electrode 8 made of an aluminum layer in a predetermined pattern on one end of the cermet film 7, the exposed surface of the insulating layer 2, the entire surface of the cermet film 7, and the electrode 8 are covered with, for example, PSG or the like. A protective film 4 is formed to complete the thin film resistive element [FIG. 2(E)].

The effects of the present invention will be explained with reference to FIG. This figure shows the relationship between the inclination angle of the side wall surface in the opening 5 and the variation in the resistance value of the thin film resistance element, and the variation is ((
Ra-Rd) /Rd) xlOO (%). However, Ra is the actual value, I? d is a design value.

In the thin film resistor element by the conventional method, the same figure (A)
The smaller the inclination angle θ shown in , the higher the coverage on the side wall surface, and the smaller the resistance component of this portion. On the other hand, as the inclination angle θ approaches 90 degrees (and the coverage rate on the side wall surface decreases, the resistance component of this part cannot be ignored, and the variation in the resistance value of this part becomes large. Therefore, l conventional In the case of the thin film resistive element produced by the method, as shown by the white circles in FIG. In the case of the thin film resistive element according to the invention, as shown by the black circles in FIG. Even if there is metal N6 on the surface
is formed, indicating that there is an effect of suppressing an increase in the resistance component on the side wall surface.

As described above, according to the manufacturing method of the present invention, the resistance component in the stepped portion of the insulating layer at the opening is reduced without giving an inclination, and the electrical characteristics of the thin film element are made uniform and stabilized. It becomes possible to convert into Therefore, in the case of a thin film resistance element, its resistance value can be controlled with high precision by the pattern shape and film thickness formed on the insulating N2, and it is also possible to control the resistance value with high precision by controlling the pattern shape and film thickness formed on the insulating N2. This eliminates the occurrence of such troubles, making it possible to guarantee long-term stable operation of integrated circuits using the thin film element. Furthermore, there is no restriction on the degree of integration of semiconductor elements due to the conditions for forming thin film elements, as in conventional methods.

In the above embodiments, the application of the present invention was mainly explained to thin film resistive elements, but it is also applicable to melt cutting elements or conductive wiring, and is applicable to semiconductor integrated circuits that require these elements. It is clear that this method is effective in uniformizing and stabilizing physical characteristics. It goes without saying that the present invention can also be applied to electric circuits or circuit elements having similar fine wiring structures other than semiconductor integrated circuits.

(g1 Effect of the invention According to the invention, in a highly integrated semiconductor integrated circuit,
This has the effect of making it possible to manufacture highly accurate thin film elements with high yield.

[Brief explanation of drawings]

FIG. 3 is a diagram for explaining an overview of the manufacturing process, and is a diagram showing an example of the relationship between manufacturing conditions and electrical characteristics of thin film resistive elements by a conventional method and a method according to the present invention. In the figure, ■ is the substrate semiconductor, 2 is the insulating layer, 3 is the thin film element, 4 is the protective film, 5 is the opening, 6 is the metal layer, 7 is thermestic odor, and 8 spoons are the electrodes.

Claims (1)

[Claims] A method for manufacturing a thin film element, which comprises forming a thin film element on a substrate having a step, and forming a film having a resistivity smaller than that of the thin film element only on the side wall surface of the step.