Method for producing a micromechanical device having inclined optical windows, and corresponding micromechanical device

Abstract

A method for producing a micromechanical device having inclined optical windows, and a corresponding micromechanical device are described. The production method includes: providing a first substrate having a front side and a rear side; forming a plurality of spaced-apart through holes in the first substrate which are arranged along a plurality of spaced-apart rows in the first substrate; forming a respective continuous beveled groove along each of the rows, the grooves defining a seat for the inclined optical windows; and inserting the optical windows into the grooves above the through holes.

Claims

1. A method for producing a micromechanical device having inclined optical windows, comprising the following steps: providing a first substrate having a front side and a rear side; forming a plurality of spaced-apart through holes in the first substrate which are arranged along a plurality of spaced-apart rows in the first substrate; forming a respective continuous beveled groove along each of the rows, the grooves defining a seat for the inclined optical windows; inserting the optical windows into the grooves above the through holes, wherein adjacent one of the grooves are beveled in opposite directions, and after the forming of the grooves, bonding a second substrate to the front side; wherein insertion openings for inserting the optical windows are formed in the second substrate, wherein the grooves and the second substrate are structured such that the optical windows are completely countersunk in the second substrate and at least a portion of the optical windows adjoin the second substrate.

2. The production method as recited in claim 1, wherein the optical windows are joined in a hermetically sealed manner along an entire periphery of the optical windows.

3. The production method as recited in claim 1, wherein the grooves are formed in a mechanical grinding process.

4. The production method as recited in claim 1, wherein the insertion openings are configured as lateral guides for the optical windows.

5. The production method as recited in claim 1, wherein the optical windows are provided with glass solder peripherally at an edge for joining, the optical windows then being inserted into the grooves using a pick-and-place process, the optical windows being joined in a hermetically sealed manner in an inserted state thermally by softening the glass solder.

6. The production method as recited in claim 1, wherein the first substrate is a wafer substrate, the wafer substrate being a glass wafer substrate, or a silicon wafer substrate, or a ceramic wafer substrate, or a metal wafer substrate, or a plastic wafer substrate.

7. The production method as recited in claim 1, wherein the second substrate is a wafer substrate, the wafer substrate being a glass wafer substrate, or a silicon wafer substrate, or a ceramic wafer substrate, or a metal wafer substrate, or a plastic wafer substrate.

8. A micromechanical device having inclined optical windows, comprising: a first substrate having a front side and a rear side; a plurality of spaced-apart through holes in the first substrate which are arranged along a plurality of spaced-apart rows in the first substrate; a respective continuous beveled groove along each of the rows, the grooves defining a seat for the inclined optical windows; and a plurality of optical windows which are inserted into the grooves in a hermetically sealed manner above the through holes, wherein adjacent ones of the grooves are beveled in opposite directions, and wherein a second substrate is bonded to the front side and wherein insertion openings for inserting the optical windows are formed in the second substrate, wherein the grooves and the second substrate are structured such that the optical windows are completely countersunk in the second substrate and at least a portion of the optical windows adjoin the second substrate.

9. The micromechanical device as recited in claim 8, wherein the optical windows are joined in a hermetically sealed manner along an entire periphery of the optical windows.

10. The micromechanical device as recited in claim 8, wherein the insertion openings are lateral guides for the optical windows.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the present invention are explained below with the aid of specific embodiments and with reference to the figures.

(2) FIG. 1a)-e) show schematic cross-sectional representations for explaining a method for producing a micromechanical device having inclined optical windows and a corresponding micromechanical device according to a first specific example embodiment of the present invention.

(3) FIG. 2 shows a schematic top view of the micromechanical device according to the first specific example embodiment of the present invention.

(4) FIG. 3a)-d) show schematic cross-sectional representations for explaining a method for producing a micromechanical device having inclined optical windows and a corresponding micromechanical device according to a second specific example embodiment of the present invention.

(5) FIG. 4 show a schematic top view of the micromechanical device according to the second specific embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(6) In the figures, identical reference signs indicate the same or functionally identical elements.

(7) FIGS. 1a)-1e) are schematic cross-sectional representations to explain a method for producing a micromechanical device having inclined optical windows and a corresponding micromechanical device according to a first specific example embodiment of the present invention, and FIG. 2 is a schematic top view of the micromechanical device according to the first specific example embodiment of the present invention.

(8) The micromechanical device having inclined optical windows according to the first specific embodiment may be used as a protection wafer device for a micromechanical micro-mirror scanning device, for example.

(9) The production of the micromechanical device is described at the level of the wafer even though it is not limited to this level, it being applicable to other substrate levels as well. To simplify the representation, only the production of two inclined optical windows is shown even though a large plurality of inclined optical windows can of course be produced.

(10) In FIG. 1a), reference sign S1 identifies a first wafer substrate, for example a silicon wafer substrate or glass wafer substrate or plastic substrate or metal wafer substrate or ceramic wafer substrate, etc., FIG. 1a) corresponds to section A-A′ in FIG. 2.

(11) The first wafer substrate S1, which has a front side VS and a rear side RS, is processed in a first production step.

(12) Through holes F1 and F2 are made in first wafer substrate S1, for example by KOH etching or sand blasting or using some other material removal method (including mechanical drilling, grinding, erosion or laser processing). Through holes F1, F2 and other through holes which are not shown are formed in parallel rows R1, R2 in a matrix on first wafer substrate S1.

(13) FIG. 1b) corresponds to section B-B′ in FIG. 2. As shown in FIG. 1b), in a subsequent process step following the formation of through holes F1, F2 etc, continuous beveled grooves N1, N2 are formed along rows R1, R2 on the front side VS, the grooves defining a seating or sealing surface for the optical windows to be inserted later. These grooves N1, N2 can be formed by grinding using a matching profile, for example. In the present example, the bevel angle—relative to the normal of the first wafer substrate S1—is 60°, but in principle any angle may be selected depending on the application. Here, each groove N1, N2 runs along a respective row of through holes F1, F2. Adjacent grooves N1, N2 are preferred to be beveled in opposite directions as shown in FIG. 1b).

(14) FIG. 1c) corresponds to section A-A′ in FIG. 2 and shows grooves N1, N2 together with through holes F1, F2. FIG. 1d) corresponds to section A-A′ in FIG. 2.

(15) As shown in FIG. 1d), optical windows G1, G2, which had previously been provided with glass solder along their entire periphery, are inserted and joined in a hermetically sealed fashion using a pick-and-place placement method (chip-to-wafer fabrication). After inserting optical windows G1, G2, the first wafer substrate, which is completely equipped with optical windows G1, G2, is heated on a hot plate (not shown) and upon reaching the softening temperature of the glass solder, optical windows G1, G2 are pressed into their respective seats by way of a pressure difference between the front side VS and the rear side RS. This causes the glass solder located between optical windows G1, G2 and the first wafer substrate S1 to soften and flow. After subsequent cooling, a hermetic bond is established between optical windows G1, G2 and the first wafer substrate.

(16) FIG. 1e) corresponds to section B-B′ in FIG. 2.

(17) The production of the protection wafer is concluded in the latter process step. To form a hermetic composite comprising an actuator or sensor wafer, glass solder is also applied to the rear side RS of the first wafer substrate S1 (not shown), for example.

(18) The production of such a wafer composite comprising a MEMS wafer is carried out using common wafer composite processes and wafer composite facilities. Here, a vacuum or overpressure relative to ambient may be established in the cavities between the first wafer substrate and the actuator or sensor wafer (not shown). Also, the final separation of the chips is done using a standard process such as sawing.

(19) FIG. 3a)-d) are schematic cross-sectional representations for explaining a method for producing a micromechanical device having inclined optical windows and a corresponding micromechanical device according to a second specific example embodiment of the present invention, and FIG. 4 is a schematic top view of the micromechanical device according to the second specific example embodiment of the present invention.

(20) FIGS. 3a), 3b), 3c) correspond to section C-C′ in FIG. 4. FIG. 3c) corresponds to section D-D′ in FIG. 4.

(21) The process state according to FIG. 3a) follows upon the process state according to FIG. 1c). A second wafer substrate S2 is bonded to the front side VS of the first wafer substrate S1. Second wafer substrate S2 may already have been thinned to its final target thickness at this time and may also have insertion openings D1, D2 for optical windows G1, G2. The thinning and the forming of insertion openings D1, D2 for glass windows G1, G2 can be performed, based on the process setup, for example using KOH etching, sand blasting, mechanical grinding, trench etching, etc., or by combinations of these structuring methods.

(22) However, in the present exemplary embodiment, second wafer substrate S2 is first bonded to first wafer substrate S1 and then thinned to its final target thickness, whereupon insertion openings D1, D2 are made for inserting optical windows G1, G2.

(23) The depth of grooves N1, N2 and the thickness of second wafer substrate S2 are preferably selected such that optical windows G1, G2 are completely countersunk relative to the exposed surface of second wafer substrate S2. This makes it possible to ensure that optical windows G1, G2 are not damaged after they are inserted, i.e., that for example scratches due to mechanical effects are avoided. Preferably, insertion openings D1, D2 are designed as lateral guides for optical windows G1, G2. Such lateral guiding prevents optical windows G1, G2 from slipping out of place inside insertion openings D1, D2 as shown in FIG. 3d).

(24) As described above in connection with FIG. 1d), optical windows G1, G2, which had been previously provided peripherally with glass solder, are inserted using a pick-and-place placement method, followed by the glass softening temperature step.

(25) The use of second wafer substrate S2 facilitates a structure-free edge of first wafer substrate S1 and also provides a peripheral joint surface on the chips. Grooves N1, N2 can thus extend across the entire wafer diameter up to the edge, which is very advantageous from a manufacturing perspective since grinding wheels with a large diameter can be used, for example. This is very advantageous for the removal rate and for the precision of the profile of grooves N1, N2. As described above, adjacent grooves N1, N2 are preferably beveled in opposite directions.

(26) Further processing of the protection wafer thus produced may proceed as described above in connection with the first specific embodiment.

(27) Although the present invention is described herein using preferred exemplary embodiments, it is not limited thereto. In particular, the materials and topologies mentioned are only exemplary and are not limited to the examples explained.

(28) In particular, other inclination directions, angles, geometries, etc., may be selected.

(29) If only one substrate S1 is used, the optical windows may also be placed into the groove and joined as continuous strips.