JPS607729A - Flattening method of selectively epitaxial grown layer - Google Patents

Abstract

PURPOSE:To enable to flatten a selectively epitaxial grown layer by a method wherein an etching method is used in which the etching speed is rather large when the incidence of an etching medium is inclined in relation to an etching surface. CONSTITUTION:An SiO2 film 2 is formed on the surface of an Si substrate 1. The desired openings are formed in succession, and epitaxial growth of Si is performed from the top surface thereof to form Si epitaxial grown layers 3a, 3b. At this time, protrusions 4 are generated at the peripheries of the opening parts, and moreover clusters 5 are formed on the film 2. Then high-frequency sputter etching is performed from the upper part of the layers 3a, 3b and the film 2. When high-frequency sputter etching is performed in such a way, the slanting surfaces are etched higher than the flat parts at first to remove the clusters 5 and the protrusions 4, etc. The etching speed at the horizontal is slow sgainst thereto. Accordingly, flattening of the selectively epitaxial growth layer can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for planarizing the surface of a semiconductor growth layer obtained by selective epitaxial growth used in the manufacture of semiconductor integrated circuit devices.

[Prior art]

In recent years, new element isolation methods have been developed for the purpose of achieving higher density integration and higher performance in integrated circuit devices. Among them, the selective epitaxial growth method has become possible to obtain an epitaxial growth layer with excellent crystallinity due to the introduction of low-pressure epitaxial growth technology, and compared to the conventional method of etching and selectively oxidizing a part of the flat taxial growth layer. Therefore, it is possible to obtain an extremely highly integrated device without lateral encroachment caused by bird's beak. However, this new technology has a problem in that the shape of the protrusion varies depending on the opening area of the insulating film and the shape of adjacent openings.

Hereinafter, the drawbacks of conventional selective epitaxial method using silicon (Sl) as a semiconductor substrate will be explained.

FIG. 1 is a cross-sectional view of the structure after selective epitaxial growth, and in the figure, 11) is an 81 substrate whose surface is oxidized to form a silicon oxide (S102) film (2).

Subsequently, desired openings are provided and 81 epitaxial growth is performed from the upper surfaces of these openings to form an 81-hole epitaxial growth layer ("a)+ (31)).

At this time, it is ideal to grow Sl only within the opening without growing it on the insulating film (2) by thermal decomposition of dichlorosilane (stu2cz2), but in reality, depending on the opening area, the area around the opening may grow. A protrusion (4) is formed on the opening, and polycrystalline instead of single crystal is formed on the insulating film (2) around the opening. Moreover, on the insulating film (2), a small Sl
Clusters (5) are formed in some places. The former protrusion (
4) has various heights depending on the opening area. For example, 1 μm
When epitaxial growth is performed to a thickness of 1.2 μm using an insulating film (2) with a thickness of grow up. The same applies to cluster (6). Due to this difference in height, pinholes may occur in a part of the thin resist film (not shown) that is formed during microfabrication, and the adhesion between the resist film and the underlying layer may be compromised, making it extremely difficult to manufacture devices. lead to unfavorable results. That is, unnecessary etching through pinholes, ion implantation, etc. may occur, and abnormal etching may occur due to peeling of the resist film near the protrusion (4) during etching.

Further, the wiring passing over the protrusion (4) becomes particularly thin, and migration of the metal wiring becomes more likely to occur rapidly, which is a problem due to miniaturization. Furthermore, when a pn junction is formed in the polycrystal S1 formed around the opening, the diffusion coefficient in the polycrystal is 5 to 1O times that of a single crystal, so lateral diffusion from the high concentration side , it is diffused to the position of the electrode formed in the region of the opposite conductivity type, causing an apparent junction short circuit, or an excessive junction due to the leakage current of a pn junction formed of polycrystal being larger than that of a single crystal. There was a problem with leaks.

[Narrowness of the invention]

This invention was made in view of the above points.
To provide a method for easily flattening the surface of a selective epitaxial growth layer by using an etching method in which the etching rate is higher when the incidence of the etching medium is oblique than perpendicular to the surface to be etched. It is.

[Embodiments of the invention]

FIG. 2 is a cross-sectional view for explaining one embodiment of the present invention. As shown in FIG. 2A, selective epitaxial growth layers (3a), (3
b) and radio frequency (RF) sputter etching from the top of the insulating film (2) using argon (Ar) ions (indicated by arrows) to obtain the shape shown in FIG. 2B. The characteristics of RF sputter etching are G, K,
Wehner [, r, Appl, phys, 2
5 (1954) 270], it was found that on polycrystalline surfaces, when ions hit the surface from the opposite direction, the etching rate was faster, as shown in Figure 3B.
As shown in Figure A, if the angle between the incident direction of the ions and the incident surface of the target object (6) is θ, then there is a relationship between the incident angle θ and the etching rate as shown in Figure A. , Figure 2 ÷
When sputter etching is performed using argon ions as shown in the figure, the oblique surfaces are first etched faster than the flat areas, and clusters (5) and protrusions (4) are eliminated. On the other hand, the etching speed on the horizontal plane is slow. The conditions that we actually tried are explained below using photographs. FIG. 4 is a cross-sectional scanning electron microscope (EIBM) photograph immediately after the formation of a selective epitaxial growth layer. The thickness of the oxide film is 1.
It is 6 μm. The openings are anisotropically etched using dry etching of the oxide film to form vertical edges. Selective epitaxial growth was performed under low pressure to a thickness of 3.6 μm.
It was formed to a thickness of .

Next, the sample was placed in a high vacuum with a degree of vacuum of 2XIO Torr, and RF sputter etching was performed using IW/Cm2 in Ar gas at lom TOrr. The sputter etching was performed using RF because the sputter etching rate is low with direct current (DC) due to the presence of the insulating film. The cross section after etching for 3 hours is shown in the SEM photograph shown in FIG. This time, we have taken sufficiently thick epitaxial growth as an example, so the epitaxial growth layer is thicker than the insulating film, but if the initial epitaxial growth layer is formed to the same thickness as the insulating film, it will become flat as shown in Figure 2B. It will be seen that this method leaves a trapezoidal shape 81 and the boundary with the oxide film is smooth. Wiring for the trapezoidal shape was extremely easy and the problem of disconnection could be solved. Moreover, since there is no polysilicon part at all, the aforementioned problems caused by polysilicon can be solved. The etching rate at this time in the flat area is 0.08 μ for Sl.
m/hr, 0.18 μm/h for S io 2
5in2 is faster in r. However, the etching rate of Si in the diagonal direction is 0.5 μm/hr, and the etching rate in the diagonal direction is extremely high.

Note that although the above example was carried out using Ar, neon (Ne
) Similar results can be obtained by using an inert gas such as xenon (Xe) or krypton (Kr). Furthermore, a method of making the thickness of the insulating film thicker than the thickness of the selectively epitaxially grown layer is also possible by performing complete planarization. Furthermore, it is also possible to introduce other methods such as ion beam etching in place of RF sputter etching.

〔Effect of the invention〕

As explained above, the present invention uses an etching method in which the etching rate is higher when the incidence of the etching medium is oblique to the surface to be etched than when it is perpendicular to the surface to be etched. 0, making it possible to put selective epitaxial growth into practical use.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the state after selective epitaxial image formation, Fig. 2 is a cross-sectional view for explaining an embodiment of the present invention, and Fig. 3 is the dependence of the etching rate on the incident angle of the etching method used in the present invention. FIG. 4 is a cross-sectional 8118M photograph immediately after forming a selective epitaxial layer, and FIG. 5 is an EIEM photograph of a cross-section after planarization according to the present invention. In the figure, (1) is a semiconductor substrate, (2) is an insulating film, (
3a), (31)) are selective epitaxial growth layers, (
4) Gl semiconductor protrusion, (6) is an island (cluster). Note that the same reference numerals in the figures indicate the same or equivalent units. Agent Masuo Oiwa 1st t4 Figure 2 33['s1

Claims (1)

[Claims] +11 An insulating film is formed on the entire surface of a semiconductor substrate, an opening is provided in a part of the insulating film, and a semiconductor layer is selectively formed on the surface of the semiconductor substrate exposed to the opening. When removing the semiconductor protrusions and polycrystalline semiconductor layers that are generated at the periphery of the selective epitaxially grown layer and the islands of polycrystalline semiconductor that are generated on the insulating film when epitaxially grown, an etching medium is applied over the entire top surface on the main surface side. A method for planarizing a selectively epitaxially grown layer, the method comprising performing anisotropic etching such that the etching rate is higher when the incidence of the etching surface is oblique than perpendicular to the surface to be etched. (2) A method for planarizing a selective epitaxially grown layer according to claim 1, characterized in that high frequency sputter etching is used for etching. (3) A method for planarizing a selective epitaxial growth layer according to claim 1, characterized in that ion beam etching is used for etching.