CN1110067C - Method of making micro silicon component by utilizing liquid phase epitaxial technique - Google Patents

Abstract

The method of making micro-silicon components by using liquid phase epitaxy technology first oxidizes the substrate silicon wafer, then opens a window of the desired component shape on the oxide film to expose the silicon bottom layer, and immerses the silicon wafer in a metal melt saturated with silicon , using silicon liquid phase epitaxy to epitaxially grow silicon components on the window. Due to the difference in resistivity between the epitaxial component and the silicon substrate, the component is separated from the substrate by chemical etching, so that the micro-silicon component of the desired shape can be manufactured, and the substrate used can be reused, making the utilization of silicon material rate is greatly improved.

Description

Method for Fabricating Micro-Silicon Components Using Liquid Phase Epitaxy Technology

Technical field

The invention relates to a method for the manufacture of miniature semiconductor components.

Background technique

Micro-silicon component is a kind of micro-mechanical parts with application prospects, which can be applied to micro-sensors, micro-machines and so on. However, it is obviously inappropriate and inconvenient to use conventional cutting, grinding, and polishing processes to manufacture extremely small-scale components (such as mechanical components of microns or tens of microns).

Contents of Invention

The purpose of the present invention is to provide a method for making micro-silicon components by using liquid phase epitaxy technology, which can conveniently obtain micro-silicon components of desired shape.

In order to achieve the above object, the technical scheme adopted in the present invention is:

1) First oxidize the substrate silicon wafer, and then open a window similar to the shape of the component on the oxide film through the photolithography technology in the silicon integrated circuit process, exposing the substrate silicon, and retaining the rest of the silicon dioxide;

2) Immerse the silicon wafer in the metal melt saturated with silicon, lower the temperature of the melt, grow the silicon component by liquid phase epitaxy, and form a lateral epitaxial layer. By controlling the temperature change and the epitaxy time during growth, the required size;

3) Using the difference in resistivity between the epitaxial component and the silicon bottom layer, the epitaxially grown silicon component is separated from the silicon substrate by chemical etching.

Compared with the prior art, the present invention has the beneficial effect that traditional mechanical processing is difficult to process hard and brittle micro-components like silicon, and pure chemical corrosion processing micro-components is very time-consuming. Using liquid phase epitaxy technology can easily process mechanical components with different shapes and sizes as small as a few microns, and the substrate used can be reused, which greatly improves the utilization rate of silicon materials.

Description of drawings

Figure 1 is a diagram of epitaxial components on a heavily doped P-type substrate;

Figure 2 is a diagram of epitaxial components on a lightly doped substrate.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described further.

First oxidize the substrate silicon wafer, and then use photolithography to open windows similar to the shape (different size) of the components on the oxide film, such as strips, squares, discs, rings, and grids. etc. The substrate silicon is exposed, and the rest of the silicon dioxide is reserved, and then the silicon wafer is placed in a liquid phase epitaxy device (such as a crucible) for epitaxial growth. Since the epitaxial growth is only carried out at the window without the oxide layer at the beginning, and the place where the oxide film is left will not epitaxially silicon, so the beginning of the grown epitaxial layer is the same as the window. However, when the thickness of the epitaxial layer exceeds the thickness of the oxide film, according to the orientation of the silicon wafer used and the epitaxial conditions, a certain amount of lateral growth will occur, and its lateral size is related to the epitaxial conditions. In actual operation, the lateral growth rate can be controlled by changing the thickness of the oxide layer, the size of the window, and the epitaxy conditions to obtain the desired size.

Liquid phase epitaxial growth requires a suitable melt, and liquid tin, gallium, indium and other metals can be used as the melt. The metal is melted at high temperature (for tin, this temperature is about 960°C) and placed in a silicon wafer to saturate the silicon content of the metal melt. Lower the temperature of the melt, and the silicon in the melt is supersaturated. At this time, the oxidized silicon wafer is put into the melt, and the temperature of the melt is lowered according to a certain rule, and silicon will be continuously epitaxially grown in the place where the window is opened on the silicon wafer. After reaching the required thickness (several times the thickness of the oxide layer), the silicon wafer is lifted out of the melt and enters the etching process.

After the epitaxial growth is finished, the silicon dioxide film can be etched away by chemical etching method (such as hydrofluoric acid, HF:HNO ₃ :CH ₃ COOH=1:3:8), and the component is separated from the substrate. Due to the lateral growth, the size of the epitaxial silicon layer on the silicon dioxide near the window can be much larger than the window width (several times to tens of times), plus the thickness of the epitaxial layer grown laterally on the oxide layer is larger than the thickness of the window epitaxial layer Much larger, so the epitaxial layer inside the window is the first to be etched, so that the component is separated from the substrate. In order to make the separation easier, the substrate 4 can be heavily doped P-type silicon (eg, the resistivity is less than 0.01Ωcm), while the epitaxial layer 2 is not doped or lightly doped, see FIG. 1 . Since the corrosion rate of heavily doped P-type silicon is much higher than that of lightly doped or undoped silicon, the substrate can be separated from the epitaxially grown components by chemical methods. If the substrate is not heavily doped P-type, but lightly doped silicon substrate 5 is used, a layer of heavily doped P-type epitaxial layer 6 can be grown in the window 1 in advance, and then lightly doped or undoped components can be grown, see figure 2. This makes it easier to separate the components from the silicon substrate by selective chemical etching. In Fig. 1 and Fig. 2, 1 is a window, 2 is an epitaxial layer, and 3 is an oxide layer.

Example:

A trial production of strip-shaped micro-silicon components was carried out on heavily doped P-type (100) silicon substrates (resistivity 0.01Ωcm). The silicon wafer was oxidized by dry oxygen at 1050°C for 10 hours, the thickness of the oxide layer was 0.35 microns, the width of the window after photolithography was 5 microns, and the length was 1 mm. The epitaxial growth is carried out in a tin melt saturated with silicon, the epitaxial growth start temperature is 960° C., and the cooling rate is 0.25° C. per minute. The epitaxial growth time was 1 hour, and the total thickness was 50 μm. After the growth, the silicon wafer was removed from the melt, and the silicon dioxide was removed with hydrofluoric acid, and then etched in an etching solution (HF:HNO ₃ :CH ₃ COOH=1:3:8) to obtain a 1 mm long wafer. A thin strip-shaped member with a width of 40 μm.

Claims (4)

1. Utilize liquid phase epitaxy to make the method for miniature silicon member, it is characterized in that: 1) First oxidize the substrate silicon wafer, and then open a window similar to the shape of the component on the oxide film through the photolithography technology in the silicon integrated circuit process, exposing the substrate silicon, and retaining the rest of the silicon dioxide; 2) Immerse the silicon wafer in the metal melt saturated with silicon, lower the temperature of the melt, grow the silicon component by liquid phase epitaxy, and form a laterally grown epitaxial layer. By controlling the temperature change and the epitaxy time during growth, the desired required size; 3) Using the difference in resistivity between the epitaxial component and the silicon bottom layer, the epitaxially grown silicon component is separated from the silicon substrate by chemical etching. 2. The method for making micro-silicon components by liquid phase epitaxy according to claim 1, characterized in that: the substrate [4] is heavily doped P-type silicon, and the epitaxial layer [2] is not doped or lightly doping. 3. The method of utilizing liquid phase epitaxy to make micro-silicon components according to claim 1, characterized in that: the substrate [5] is lightly doped with silicon, and a layer of heavily doped P is grown in the window [1] in advance. type epitaxial layer [6]. 4. The method for manufacturing micro-silicon components by liquid phase epitaxy according to claim 1, characterized in that: said metal melt is liquid tin, gallium, and indium.

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