Method of producing acceleration sensors

Details Method of producing acceleration sensors Method of producing acceleration sensors

1997-10-27

1999-08-10

Bowers, Charles

Semiconductor device manufacturing: process

Making device or circuit responsive to nonelectrical signal

Physical stress responsive

438 52, 438 53, G01L 2310, G01P 1509

Patent

active

059372753

DESCRIPTION:

BRIEF SUMMARY
PRIOR ART

The invention is based on a method as generically defined by the preamble to the main claim.
From German Patent Disclosure DE 43 18 466, a method for producing a micromechanical sensor is already known in which a substrate with a sacrificial layer is used. In an epitaxial application system, a silicon layer is deposited on this substrate. Above the sacrificial layer, this silicon layer grows in the form of a polysilicon layer. As the substrate, a monocrystalline silicon wafer is used, so that the silicon material, in the regions where it has immediate content with the substrate, grows in the form of monocrystalline silicon.


ADVANTAGES OF THE INVENTION

The method according to the invention having the characteristics of the independent claim has the advantage over the prior art that smoothing of the polysilicon layer is attained. As a result of the smoothing, the structures for the sensors can be made in the polysilicon layer with especially high precision. High-quality sensor structures can thus be produced with great precision.
By the provisions recited in the dependent claims, advantageous further features of and improvements to the method disclosed in the independent claim are possible. Especially precisely, the structuring of the polysilicon layer is done by a plasma etching process. To improve the quality of the polysilicon layer from the very outset, a polysilicon starter layer may be provided on the sacrificial layer. By using a sacrificial layer, which covers the entire surface of the substrate, an especially simple method for producing sensors is disclosed. When a structured sacrificial layer is used, the sensor structures can be anchored especially well to the surface of the substrate. By using monocrystalline silicon as a wafer, anchored regions are created that comprise monocrystalline silicon. This method has especially good properties. By leveling the polycrystalline layer until it forms a single plane with the monocrystalline layer, an especially high-quality surface is created that is especially highly suitable for further processing. In particular, electronic circuits can then be made in the monocrystalline silicon layer and can be connected to the sensor structures with surface-mounted or buried conductor tracks.


DRAWINGS

Exemplary embodiments of the invention are shown in the drawings and described in further detail in the ensuing description.
FIGS. 1-3 show the production method known from the prior art (DE 43 18 466);
FIGS. 4 and 5 show the etching step according to the invention;
FIGS. 6 and 7 show the leveling of the polysilicon layer and monocrystalline silicon layer, and
FIG. 8 shows the method with a full-surface sacrificial layer on the substrate.


DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In FIG. 1, a substrate 1 is shown on which a sacrificial layer 2 is applied. Over the sacrificial layer, a polysilicon starter layer 3 is applied. It will be assumed hereinafter that the substrate 1 is a monocrystalline silicon substrate. However, other types of substrates of ceramic materials, glass or metal are usable in principle as well. The sacrificial layer shown here is provided only in individual regions of the top side of the substrate 1. However, it is equally possible for the sacrificial layer 2 to cover the entire surface of the substrate 1. The polysilicon starter layer 3 is applied to the sacrificial layer 2 in order to improve the quality of the ensuing deposition of silicon. However, the method can also be performed without this polysilicon starter layer.
Any materials that can be etched selectively to silicon are conceivable as material for the sacrificial layer 2, especially silicon oxide, silicon nitride, glass or metals. The polysilicon starter layer 3 is preferably deposited in an LPCVD (low-pressure chemical vapor deposition) reactor, since such deposits can be made on arbitrary surfaces at low temperatures.
The substrate of FIG. 1 is introduced into an epitaxial application system, in which a silicon layer 4 is then deposited. Such epitaxial application s

REFERENCES:
patent: 5792675 (1998-08-01), Offenberg
patent: 5804457 (1998-09-01), Benz et al.
patent: 5827756 (1998-10-01), Sugino et al.
patent: 5840597 (1998-11-01), Hartauer

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