JPH04199656A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable the upper recess of a groove to be flattened by a method wherein a low melting point glass film is formed on an insulating film provided onto the surface of semiconductor substrate where a dielectric is buried in a groove, and then the substrate is thermally treated. CONSTITUTION:An insulating film 2 of silicon oxide is formed on the side wall of a groove provided onto a silicon semiconductor substrate 1, a dielectric 3 of polycrystalline silicon is filled into the groove where the insulating film 2 is formed, the insulating film 2 and the dielectric 3 formed outside the groove are removed by an etchback method, and the insulating film 2 of silicon oxide is formed on the surface of the silicon semiconductor substrate through a thermal oxidation method. Then, a PSG film 4 is formed on the surface of the insulating film 2 on the semiconductor substrate 1, and the substrate 1 is subjected to a reflow treatment in an atmosphere of nitrogen. By this setup, the PSG film 4 formed on the insulating film 2 is laid in the upper recess of the dielectric 3 buried in the groove, so that a recess formed on the top of the dielectric 3 clan be flattened.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device in which grooves are formed in a semiconductor substrate, for example, to electrically isolate elements.

[Conventional technology]

In recent years, in the manufacture of semiconductor devices such as integrated circuits, the process of forming relatively deep grooves in semiconductor substrates has become important. This groove is used, for example, to electrically isolate elements included in a semiconductor device. FIG. 2 shows an example of a conventional semiconductor device in which a groove as described above is formed. Referring to FIG. 2, a silicon oxide film (5i
02) is formed, and a dielectric material 3 made of polycrystalline silicon is embedded in the groove in which the insulating film 2 is formed by chemical vapor deposition (CVD), and the insulating film 2 and other parts of the insulating film 2 other than inside the groove are buried. The dielectric 3 is removed by an etch-back method, and finally, an insulating film 2 made of a silicon oxide film (5I02) is formed on the surface of the semiconductor substrate 1 by a thermal oxidation method.
Element isolation is completed.

[Problem to be solved by the invention]

In the conventional semiconductor device described above, as shown in FIG. 2, a depression is formed in the upper part of the groove. This is caused by over-etching of the material in the trench during the etch-back process, and although it is possible to reduce it to some extent by controlling the etching, it is difficult to eliminate it completely. Further, such depressions cause various restrictions and obstacles in the subsequent film formation process and patterning process (for example, wiring process) for forming elements. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device in which a groove is formed in which a recess above the groove can be flattened.

[Means to solve the problem]

In order to achieve the above object, the present invention forms a low melting point glass film on an insulating film formed on the surface of a semiconductor substrate in which a dielectric is embedded in a groove, and then heat-treats the film.

[Effect]

In the method for manufacturing a semiconductor device described above, the low melting point glass film on the insulating film or the depression above the dielectric buried in the groove is filled, and the surface of the low melting point glass film is flattened;
The surface of the semiconductor substrate becomes flat.

【Example】

FIG. 1 shows an embodiment of the method for manufacturing a semiconductor device of the present invention. In this method, first, as shown in FIG. 1(a), an insulating film 2 made of a silicon oxide film (5i02) is formed on the side wall of a trench formed in a silicon semiconductor substrate 1.
A dielectric material 3 made of polycrystalline silicon is buried in the groove in which the insulating film 2 is formed by low-pressure CVD, and the insulating film 2 and dielectric material 3 other than inside the trench are removed by an etch-back method, and the surface of the silicon semiconductor substrate 1 is etched. An insulating film 2 made of a silicon oxide film (Si20, ie, silicon dioxide) is formed to a thickness of, for example, 500 by a thermal oxidation method. Next, as shown in FIG. 1(b), for example, P is applied to the surface of the insulating film 2 on the semiconductor substrate 1 by low pressure CVD.
2O5, PSGSiO2 with a concentration of 8io1%, for example IJl
Form to a thickness of s. Next, as described above, PSGSiO2 is placed on the surface of the insulating film 2.
The semiconductor substrate 1 thus formed is placed in a diffusion furnace, and subjected to a reflow (ref' low) treatment for 30 minutes at a furnace temperature of 1000° C., for example, in a nitrogen N2 atmosphere. As a result, as shown in FIG. 1(e), the PSGSi on the insulating film 2
The recess at the top of the dielectric 3 embedded in the O2 groove was filled, the PSGSiO2 surface became flat, and the surface of the semiconductor substrate 1 became flat. In the above embodiment, a silicon semiconductor substrate is used as the semiconductor substrate 1, but a semiconductor other than silicon, such as germanium, may be used. Further, in the above embodiment, a silicon oxide film is used as the insulating film 2, but other insulating films can also be used, and the insulating film may have a multilayer structure. Further, in the above embodiment, polycrystalline silicon is used as the isolation dielectric 3, but other dielectrics can also be used. Further, in the above embodiments, a PSG film was used as the low melting point glass, but other low melting point glasses can also be used. Further, in the above embodiments, reflow treatment was used as the heat treatment, but other heat treatment may also be used. In short, any low melting point glass and heat treatment may be used as long as it can fill the recesses and provide a flat surface. Effects of the Invention 1 As is clear from the above description, according to the present invention, it is possible to flatten a depression formed on a dielectric buried in a groove of a semiconductor device. Therefore, there are no restrictions or obstacles in the subsequent film formation process, patterning process, etc. for element formation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing each step of an embodiment of a method for manufacturing a semiconductor device according to the present invention, and FIG. 2 is a sectional view showing an example of a conventional semiconductor device. 1; Silicon semiconductor substrate 2; Insulating film (silicon oxide film) 3: Dielectric (polycrystalline silicon) 4: Low melting point glass (PSG film) Agent: Masami Sato, patent attorney Figure 1

Claims (1)

[Scope of Claims] A step of forming a groove in a semiconductor substrate, a step of embedding a dielectric in the groove, a step of forming an insulating film on the surface of the semiconductor substrate in which the dielectric is embedded in the groove, and the insulating layer. A method for manufacturing a semiconductor device, comprising: forming a low melting point glass film on the film; and heat treating the semiconductor substrate on which the low melting point glass film is formed on the insulating film.