Etching a substrate: processes – Etching of semiconductor material to produce an article...
Patent
1994-09-28
1996-09-03
Ryan, Patrick
Etching a substrate: processes
Etching of semiconductor material to produce an article...
73721, 73727, 73706, 73708, 216 51, 216 99, H01L 21306
Patent
active
055520154
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for manufacturing a sensor to detect a difference between two pressures having a measuring diaphragm of silicon which is clamped between two disk-shaped bearing parts of glass, with the formation in each case of an inner chamber, the one inner chamber being acted on by one of the pressures via a passage opening in the one bearing part and the other inner chamber being acted on by the other pressure of the pressure difference to be measured.
Such a process can be noted from EP 0 007 596 B1. In this known process, the measuring diaphragm which consists of silicon is produced in the manner that a silicon disk is first doped with boron on both of its sides. Layers of oxide present on the outside are partially removed by photo-etching with the formation of a mask. Thereupon, the doped regions are removed from both sides of the silicon disk by, for instance, acid etching, and the mask is thereupon also removed. The finished measuring diaphragm is then connected at its edge by bonding to, in each case, one glass disk as a bearing part; each glass disk bears a vapor-deposited layer of metal as an electrode on its inner side.
SUMMARY OF THE INVENTION
The present invention improves the known manufacturing process in such a manner to produce a pressure-difference sensor which is protected against overload solely by a suitable development of the bearing part.
To achieve this object, in a process of the aforementioned type at least the further bearing part which limits the other inner chamber is, in accordance with the present invention, provided, prior to the clamping of the silicon measuring diaphragm, with a recess having oblique sides of very slight slope, in the manner that a thin layer which can be removed by an isotropically acting etching liquid is applied to surface regions of the disk-shaped bearing part corresponding to the oblique sides to be produced. Next, the thin layer is covered with an etching mask which is not attacked by the isotropically acting etching liquid. Finally, whereupon the isotropic etching is effected.
Federal Republic of Germany 32 15 411 A1, inter alia, discloses a process for producing an oblique-sided recess in a substrate in which a layer removable by an isotropically acting etching liquid is applied to surface regions of the substrate corresponding to the recess to be produced, the removable layer is covered by an etching mask which is not attacked by an isotropically acting etching liquid, and thereupon an isotropic etching is effected, but this process is used to avoid very sharp square edges of the opening. Metal contacting paths which are conducted over sharp edges for an opening can tear.
From EP 0 394 664 A2 there is furthermore known a process for the manufacture of a silicon measuring diaphragm for a pressure sensor in which a recess having an oblique side in a trapezoidal shape is first of all etched in a silicon substrate by anisotropic etching. To impart the silicon measuring diaphragm with substantial resistance to breakage, regardless of the direction in which the pressure acts, an isotropic etching is carried out after the anisotropic etching. This isotropic etching is effected with an etching liquid of isotropic action after surface regions of the silicon disk have been covered in a manner corresponding to the recess to be produced by an etching mask which is not attacked by the isotropically acting etching liquid, for instance a mask of silicon nitride. As a result of the isotropic etching, the recess is enlarged somewhat on all sides, with rounding of its corners, with the advantage that the pressure bearing ability of the diaphragm on both sides is approximately equal.
The pressure-difference sensor of the present invention has the great advantage that, due to the development of the recess in its further bearing part, it is protected against overload without additional measures, since the semiconductor measuring diaphragm can fit snugly into the recess in the event of an overload, without d
REFERENCES:
patent: 4222277 (1980-09-01), Kurtz et al.
patent: 4530244 (1985-07-01), Starr
patent: 4766666 (1988-08-01), Sugiyama et al.
patent: 4986127 (1991-01-01), Shimada et al.
patent: 5259248 (1993-11-01), Ugai et al.
Arndt Frank
Schlaak Helmut
Dixon Merrick
Ryan Patrick
Siemens Aktiengesellschaft
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