JPS60173832A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make the size of the bottom of a contact hole smaller than that of an opening in a resist film formed prior to anisotropic dry etching by shaping the opening, size thereof is reduced along the depth direction, to an insulating film through anisotropic dry etching. CONSTITUTION:A resist film 5 with an opening 6a in size conformed to the size (a) of the upper section of a contact hole is formed on an insulating film 4, and an opening 6a section in the insulating film 4 is anisotropic dry-etched as using the resist film 5 as a mask while controlling the temperature of the resist film 5. The temperature of the resist 5 is elevated to a temperature such as approximately 250 deg.C at the same time as etching is started, and the insulating film 4 is etched until the depth of the hole formed reaches to one terminal 2 in a transistor while the temperature is lowered in succession in parallel with the progress of etching so that the temperature reaches to approximately 150 deg.C when the depth of etching is brought to approximately half the thickness of the insulating film 4. A desired funnel shape in which the size of a bottom is represented by (c) is obtained in the form of the hole shaped through etching, and a desired contact hole 1b is acquired when removing the resist film 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and in particular to a method of forming a contact ball of a morning glory shape whose dimensions become smaller along the depth direction of an insulating film. about.

(b) Background of the Technology In a semiconductor device, an electrode of a transistor formed on the surface of a semiconductor substrate is usually formed on an insulating film on the transistor through a conductive region in a contact hole provided through the insulating film on the transistor. It has been derived.

The formation of the conductor region is performed by a surface deposition method such as a vapor deposition method or a sputtering method, using aluminum or the like, for example, together with the deposition of a conductor film for forming the electrode or wiring on the insulating film. There are many. Therefore, in order to ensure that the conductor adheres securely and to prevent disconnection accidents, the shape of the contact 1 to pole becomes an issue. What is desired is a shape with good coverage, which allows for a reasonable adhesion state during the process.

(C1 Prior art and problems Figure 1 is a diagram showing a desirable shape of a contact hole.
FIG. 2 is a diagram (a) to (dl) showing an example of a conventional method for forming a contact hole, in which 1.1a is a contact ball, 2 is one terminal of a transistor, 3 is a semiconductor substrate,
4 is an insulating film, 5 is a resist film, 6 is an opening, and 7.8 is an etched region.

In FIG. 1, a contact hole 1 is formed at a position where an insulating film 4 made of silicon dioxide, for example, is deposited on a semiconductor substrate 3 on which a terminal 2 of a transistor is formed, and is in contact with one terminal 2 of a transistor. There is. In order to improve the coverage, it is desirable that the shape of the contact ball l be a morning glory shape in which the distance from the surface of the insulating film 4 to the bottom of the inner surface of the contact hole 1 is smoothly narrowed, as shown in the figure. Although its size is on the order of μm, it is desired to make it even smaller in order to reduce the size of transistors as semiconductor integrated circuit devices become more highly integrated.

Generally, when making holes on the order of μm in a substrate, a method is used in which a film such as a resist having openings is formed on the substrate, and etching is performed using the film as a mask. This method is also used when forming contact holes, but when aiming for a morning glory-shaped shape, the method shown in FIG. 2 is used with some modification.

That is, as shown in FIG. 1A, a resist film 5 having an opening 6 of a size matching the size of the bottom of the contact pole is formed on the insulating film 4 in advance, and this is used as a mask. Etch the etch region 7 shown in FIG. 1b) by isotropic wet etching or isotropic dry etching. Since it is isotropic, the size of the portion of the etch region 7 in contact with the photoresist 5 is larger than that of the opening 6. Then, by anisotropic dry etching, the etched area 8 shown in Figure (C1) is etched.
A hole having the same size as the opening 6 and reaching one terminal 2 of the transistor is made by etching, and the photoresist film 5 is removed.
(1) The contact hole 1a shown in the figure is formed.

From a macroscopic perspective, this contact hole 1a corresponds to the insulating film 4.
Although the corner at the boundary with the surface is rounded and is similar to the contact ball 1 shown in FIG. 1, when viewed microscopically, due to the characteristics of the etching, there is still a corner at the boundary between the etched region 7 and the surface of the insulating film 4. However, there is a problem in that the coverage is not sufficient.

Furthermore, the size of the bottom portion is the same as the size of the aperture 6, and there is a limit to miniaturization due to technical constraints in forming the aperture 6.

(dl) Purpose of the Invention In view of the above-mentioned conventional problems, an object of the present invention is to form a smooth morning-glory shape between the inner surface of the contact ball and the surface of the insulating film when forming a contact hole in an insulating film, and to It is an object of the present invention to provide a method for manufacturing a semiconductor device in which the size of the bottom of a contact pole can be made smaller than the size of a resist film opening formed prior to etching.

(e) Structure of the Invention The above object is to form an insulating film on a semiconductor substrate, form a resist film having a flowering portion on the insulation crotch, and extend the insulating film exposed at the opening into the flowering portion. The resist film is characterized by forming openings in the insulating film whose dimensions become smaller along the depth direction of the insulating film by performing anisotropic dry etching while controlling the temperature of the resist film so that This is achieved by a method of manufacturing a semiconductor device.

The opening formed in the insulating film is formed into a morning glory shape with a smooth surface between the inner surface and the surface of the insulating film, resulting in a contact hole having a desired shape, and the size of the bottom of the contact ball is equal to that of the resist. The initial size of the membrane pores becomes smaller.

(fl Embodiments of the Invention Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals indicate the same objects throughout the drawings.

FIG. 3 is a diagram (a) to tel showing an example of the method for forming a contact hole according to the present invention, FIG. 4 is a diagram showing the dimensional change of the resist film opening at that time, and FIG. In this figure, ib is a contact ball, 6a is an opening, ) (8, fl b is an etching region, 10 is a wafer, 11 is a chamber, 12 is a two-part electrode, 13 is a lower electrode, 14 is a power source, 15 is a heat exchanger, 16 is a controller, and a, b, and c indicate dimensions, respectively.

The contact hole forming method shown in FIG.
1. As shown in the figure, 1. Form a resist film 5 on the insulating film 4 with an opening 6a having a size matching the size a) of the upper part of the contact ball, and use this as a mask to open the insulating film 4. Although the hole 6a portion is anisotropically dry etched, the feature is that the temperature of the resist film 5 is controlled at the same time.

That is, at the start of etching, the temperature of the resist 5 is raised to, for example, about 250°C, and thereafter, when the etching depth is about 1/2 of the thickness of the insulating film 4, the temperature is raised to, for example, about 150°C. The insulating film 4 is etched while gradually lowering the temperature in parallel with the progress of etching until the depth of the hole to be formed reaches one terminal 2 of the transistor.

As a result, initially the size of the etched region 8a is a, which is the size of the opening 6a, as shown in FIG.
The size of the opening 6a decreases over time as it sag inside the hole 6a, so during etching,
As shown in C1, the size of the etched region 8b is smaller than a. On the other hand, the rate of sagging of the resist film 5 slows down as the temperature decreases, and reaches approximately zero at about 150°C, so the openings 6 in the etching process described above decrease.
The size of a changes as shown in Fig. 4, and becomes the dimension C.
The change stops at . Therefore, the hole shape formed by etching becomes the desired morning glory shape with the bottom size C as shown in FIG. 3(d), and if the resist film 5 is removed, the desired contact hole 1
b is obtained.

Specifically, by using the above method, for example, by setting the dimension a of the resist film 5 having a thickness of approximately 1 μm to approximately 1.2 μmφ, the insulating film 4 having a thickness of approximately 1 μm is formed into the shape shown in FIG. It is possible to form a contact hole with a dimension C of about 0.6 μmφ in the near future. By the way, in order to make the dimension C about 0.6 μmφ by the method shown in FIG. 2, the size of the opening 6 in the resist film 5 needs to be about 0.6 μmφ, which requires advanced technology. Therefore, the method of the present invention greatly contributes to miniaturization of transistors and, by extension, to higher integration of semiconductor integrated circuit devices.

Note that the temperature value of 250° C. to 150° C. is selected so that the behavior of the resist film 5 is as described above, and when the resist is changed, it may be appropriately determined according to its characteristics.

Further, in order to carry out the above-mentioned etching, a parallel plate type dry etching apparatus, the configuration of which is shown in FIG. 5, may be used, for example. As usual, anisotropic dry etching is performed by applying high frequency from the power source 14 to the upper electrode 12 and the lower electrode 3 provided in the chamber 11.
3 is equipped with a heat exchanger, and the temperature of the lower electrode 13 can be controlled by a temperature controller 16. The above-mentioned temperature control of the resist film 5 of the wafer 1o (FIG. 3) placed on the lower electrode 13 (FIG. 3 (al) state) is possible by controlling the temperature of the lower electrode 13 via the wafer 10 body.

(g) Effects of the Invention As explained above, according to the structure of the present invention, when forming a contact hole provided in an insulating film, a smooth morning-glory shape is formed between the inner surface of the contact hole and the surface of the insulating film. Provided is a method for manufacturing a semiconductor device in which the size of the bottom of the contact hole can be made smaller than the size of an opening in a resist film formed prior to etching, and a contact hole with good coverage can be provided. At the same time, it has the effect of making it possible to reduce the size of transistors and, by extension, to increase the degree of integration of semiconductor integrated circuit devices.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the desirable shape of the contact hole.
FIG. 2 is a diagram (a) to (d) showing an example of a conventional method for forming a contact ball, and FIG. 3 is a diagram (a) showing an example of a method for forming a contact hole according to the present invention. ~
(81, Fig. 4 is a diagram showing the dimensional change of the resist film opening at that time, and Fig. 5 is a diagram showing one configuration of the etching apparatus used at that time. In the drawings, 1.1a, 1b is a contact hole, 2
is one terminal of a transistor, 3 is a semiconductor substrate, 4 is an insulating film, 5 is a resist film, 6.6a is an opening, 7.8.8a,
8b is an etching region, 10 is a wafer, 11 is a chamber, 2 is an upper electrode, 13 is a lower electrode, 14 is a power source, 15 is a heat exchanger, 16 is a controller, and a, b, and c indicate dimensions, respectively. □吋Ili″I 手S Tsui

Claims (1)

[Claims] An insulating film is formed on a semiconductor substrate, a resist film having an opening is formed on the insulating film, and the insulating film exposed at the opening is formed in the resist film so that a droop is formed in the opening. A method for manufacturing a semiconductor device, the main feature of which is to form openings in the insulating film whose dimensions become smaller along the depth direction of the insulating film by anisotropic dry etching while controlling the temperature. .