WO2000017095A1

WO2000017095A1 - Control structure for producing hollow spaces and/or undercut zones in micromechanical and/or microelectronic components

Info

Publication number: WO2000017095A1
Application number: PCT/DE1999/003035
Authority: WO
Inventors: Dieter Maier-Schneider
Original assignee: Infineon Technologies Ag
Priority date: 1998-09-24
Filing date: 1999-09-22
Publication date: 2000-03-30

Abstract

The invention relates to a control structure (9) for producing hollow spaces (3) or undercut zones in micromechanical and/or microelectronic components by etching, which comprises one or more partial areas (11) situated in the area of the control structure. Said partial areas contain one or more individual structures (2, 3) and possibly legends (13) and/or markings assigned to the individual structures.he individual structures at least partly change their geometric shape during etching and the individual structures of a partial area are geometrically different from the individual structures of another partial area, so that on the basis of an evaluation of the individual structures by comparison of the partial areas after clearing of the hollow space or undercut zones, the extend of etching before and/or during the manufacture of the micromechanical component can be quantitatively determined or evaluated. The invention further relates to a coated wafer and a method for producing a micromechanical and/or microelectronic component.

Description

description

CONTROL STRUCTURE FOR THE PRODUCTION OF CAVITIES OR UNDERLYING AREAS IN MICROMECHANICAL AND / OR MICROELECTRONIC COMPONENTS

The invention relates to a control structure for producing cavities or undercut areas in micromechanical and / or microelectronic components by etching, a coated wafer comprising a plurality of interconnected chips 7 and one or more micromechanical and / or microelectronic components, the micromechanical and / or or microelectronic components have at least one cavity 3 or undercut area and a method for producing a micromechanical and / or microelectronic component comprising at least one cavity 3 or undercut area which is produced by one or more etching steps.

In the manufacture of micromechanical components, such as pressure sensors or acceleration sensors, structures are generally applied to a silicon wafer in known CMOS, BiCMOS or bipolar technology, which in some areas has movable elements such as e.g. Have membranes, tongues, steps or the like. These movable elements can be manufactured, for example, by first applying sacrificial layers made of e.g. Silicon dioxide on a doped wafer, subsequent application of a membrane layer made of e.g. Polysilicon above the sacrificial layer and selective etching of the material of the sacrificial layer in relation to silicon wafers and silicon membranes take place in a partial area. Cavities for pressure sensors are known to be manufactured in such a way that the supply of the etching solution and

The sacrificial material is removed through etching channels or etching holes arranged laterally or vertically to the wafer surface. A method for producing a pressure sensor, in which the cavity is exposed via etching holes arranged in the membrane, is described, for example, in EP-A-0 714 017. According to this method, a sacrificial layer, which is provided for producing the cavity required for the pressure sensor, is applied to a Si substrate. This auxiliary layer can also be formed by an upper layer portion of the substrate. A membrane layer of z. B. polysilicon applied. During the manufacture of the membrane layer, a mask is used to produce openings for etching out the cavity lying in the region of the membrane layer below the membrane layer. The number of openings required per cavity depends on the size of the cavity, the etching time and the thickness of the sacrificial layer. The sacrificial material is etched selectively, ie the substrate material and the membrane layer are not attacked by the etching solution.

The micromechanical structures produced must be checked to ensure that the volume of the exhaled cavities or undersized areas is true to size in order to maintain a certain quality after or already during the manufacture of the micromechanical structures. A direct determination or control of the etch dimension on the micromechanical component to be produced itself — without destroying the wafer — is generally not possible with sufficient accuracy. The etched edges cannot be reliably recognized in the micromechanical structures to be produced.

In a production line for conventional semiconductor components, such as for CMOS, BiCMOS or bipolar chips, control structures are used which are used to check the individual production steps. With the help of these control structures, which are common in semiconductor component production, the position can be similar to multi-color printing, for example of the individual masks are verified. For reasons of space, these control structures are usually arranged in the so-called sag frame of the wafer, that is to say in a strip-shaped area which is arranged between the individual chips and which is lost during the singulation. The control structures known in the manufacture of semiconductor components do not allow the dimensional accuracy of the volume of exhaled cavities or undercut areas in micromechanical components to be checked.

The object of the present invention is to provide a control structure for the production of cavities or undercut areas in micromechanical or also microelectronic components, which allows the quality of the etching process to be checked. Another object of the invention is to provide a control structure which allows a quantitative determination of the extent of the understatement.

This object is achieved according to the invention by a control structure 9 for producing cavities 3 or undercut areas in micromechanical and / or microelectronic components by etching. According to the invention, the control structure 9 comprises one or more partial areas 11 arranged in the area of the control structure, the partial areas one or more individual structures 2, 3 and possibly the one

Individual structures associated with labels 13 and / or markings. According to the invention, the individual structures at least partially change their geometric shape during the etching. According to the invention, the individual structures of a subarea are geometrically modified in comparison to the individual structures of another subarea, so that the extent of the etching after and / or during the manufacture of the micromechanical and / or microelectronic component can be read or evaluated quantitatively. If it is expedient, two sub-areas may have identical individual structures. However, the partial areas are preferably all geometrically modified from one another. In particular, a partial area is geometrically modified with respect to an adjacent partial area. The geometric modification can consist, for example, in that the spacing of the partial structures is changed in a partial area.

After the completion of an etching step, the control structure according to the invention is evaluated. If the desired degree of undercut has not yet been reached, a further etching step can be carried out and a new check can be carried out. In this way, an accurate setting of the etching time with subsequent checking of the result can be carried out in a simple manner under fluctuating ambient conditions in practice. The control structure is therefore preferably evaluated immediately after an etching step has been carried out, in particular this takes place before further processing steps of the component. The evaluation of the

Control structure can preferably be optically, e.g. with a microscope, but also on broken surfaces if necessary.

According to the invention, micromechanical components are understood to mean structures with movable parts that are produced in general in semiconductor technology, such as e.g. Membrane arrangements, such as sensors, in particular pressure sensors or microphone sensors, or structures with tongues, such as, for example, acceleration sensors or force sensors, or very generally micromechanical structures which have moving parts, such as bridges, beams, wheels or the like.

Microelectronic components according to the invention are components which are known per se and which are produced by semiconductor production steps which are known per se, the microelectronic components according to the invention having at least one undercut region or cavity. You differentiate which differ from the micromechanical components in that they do not have to have any movable functions. An example of a suitable microelectronic component is an infrared sensor.

The term “cavity” according to the invention is to be understood in its broadest conceivable form. This includes, for example, cavities with closed volumes, which can have any shape. The cavities are preferably etched areas in the form of spheres, ellipses, round or oval disks homogeneous materials are the cavities of symmetrical shape. Corresponding cavities occur, for example, in pressure sensors. The cavities according to the invention can also have openings, such as in the case of a differential pressure sensor.

“Undercut areas” according to the invention are, for example, open undercut areas, such as are required for the production of webs, tongues, bridges or steps. Undercut areas are required, for example, for the production of acceleration sensors or force sensors.

The pawing can be carried out by executing one or more etching steps, whereby according to the invention it is possible to check the extent of the previous etching steps between each individual step with the aid of the control structure according to the invention. The pawing is preferably carried out selectively, i.e. H. that an etchant used for etching essentially only at least partially removes the type of material which is specified for defining the cavity volume in the form of a sacrificial material or a sacrificial layer 4. The material types delimiting the cavity, such as the material of the wafer 1 or the membrane layer 5, are essentially not removed during the etching.

The control structure according to the invention preferably contains in a partial area 11 at least two partial structures 2, 3, each partial structure having an upper layer 5, a lower layer 1, a sacrificial layer 4 and an etching opening 2 introduced in the upper layer, the sacrificial layer 4 being removed during the etching by removal of material Cavity 3 arranged between the upper and lower layers is formed and the spacing of the substructures, preferably the spacing of the etching openings, is selected in a partial region such that a connection of at least two cavities 3 occurs within a partial region when the desired etching dimension is reached.

Accordingly, the cavities can be etched, for example, either through the etching opening in the membrane from the top, or from the side via etching channels which, for example, run parallel to the surface of the wafer below the membrane layer and come to the side of the membrane. The method by which the cavity is etched expediently corresponds to the method by which the cavity is produced in the micromechanical component to be produced, because in e.g. With identical etching channels or etching holes, the etching times in the control structure can also be compared with those in the micromechanical component.

An etching opening according to the invention is expediently a hole 2 in the upper layer 1 with a round or, which is easier to manufacture in terms of layout, with a square shape, the square shape being partially rounded during the lithography.

The distance between the partial structures 2, 3 within a partial area 11 can be used to determine the extent of the etching, in particular to determine the etching volume. The distance between the partial structures 2, 3 within a partial area 11 preferably increases or decreases stepwise with respect to the partial structure distance in an adjacent partial area. It can then be read in a simple manner in which sub-area, for example, a touch of the etching fronts progressing during the etching. ..

The etching openings 2 in the upper layer 5 are expediently arranged directly above the sacrificial layer. In this way, cavities 3 can be formed during the etching, starting from the etching openings, which enclose the cavity in a ring. It is alternatively expedient if the etching openings 2 are connected to etching channels running underneath the upper layer, so that the cavities are etched from the side.

The distance D between the openings 2 can be chosen to be the same within a partial area. In this case, the distance D in the control structures can be selected such that a certain range for the value D is covered in steps of increasing or decreasing. For example, the range for D can be selected so that when etching disc-shaped cavities 3 it corresponds as closely as possible to the range of fluctuations in the radius of the cavity which results from production-related fluctuations during a specific etching time. The distance D between the openings 2 within a partial area depends on the requirements for the accuracy of the structures to be etched. D is preferably in a range from 0.1 to 1000 μm. The aforementioned

Steps are expediently of the same size, so that the distance D increases, for example, from one sub-area to the next by 0.2 μm.

The invention is not restricted to a special shape of a partial structure 2, 3. So are other substructures e.g. conceivable with more than two etching holes.

The area of the control structure is generally chosen so that it takes up as little space as possible. In a control structure there are preferably 4 to 100 subregions 11.

Within a sub-area, it is expedient if the number of individual structures is in the range from 2 to 5. It is particularly expedient if exactly two individual structures are arranged in each partial area.

The subareas are preferably arranged next to one another or in rows and columns.

The invention also relates to a coated wafer 1 comprising a multiplicity of interconnected chips 7 and one or more micromechanical components, the micromechanical components having at least one cavity (3) or undercut area, which is characterized in that on one side of the A control structure 9 according to the invention is present on the wafer, preferably on the same side on which the micromechanical components to be produced are located.

In the coated wafer 1 according to the invention, the control structure 9 is preferably arranged in the saw frame 8 of the wafer. When the wafer is separated, the connected chips are separated from one another. This is done, for example, by sawing the wafer along the saw frame. The area of the wafer on which the control structure according to the invention is located is then lost.

Another object of the invention is a method for producing a micromechanical component comprising at least one cavity 3 or undercut region, which is produced by one or more etching steps, which is characterized in that the extent of the etching steps is evaluated or read quantitatively, wherein the evaluation or reading is carried out by means of a control structure 9 previously applied to the coated wafer 1. The control structure can be applied in a manner known per se, for example by means of lithographic technology. The control structure is preferably produced using largely the same steps as the cavity regions of the micromechanical components contained in the chips.

The quantitative determination of the etch dimension is preferably carried out optically or electrically without destroying the wafer. The determination can be made optically, for example, by examining the wafer under a light microscope. The quantitative determination is expediently carried out either visually, that is to say manually, or automatically, for example with the aid of automatic image processing.

The invention is explained in more detail below with reference to an exemplary embodiment shown in FIGS. 1 to 3.

Show it:

1 shows a control structure according to the invention in a top view, FIG. 2 shows a section through a control structure according to FIG. 1 along the axis A-B, FIG. 3 shows an arrangement of the control structure according to the invention on the surface of a silicon wafer, in a schematic representation, not to scale, and

Figure 3a is an enlarged view of a partial section of Figure 3.

The control structure shown in FIG. 1 can be evaluated, for example, with the aid of an optical microscope. FIG. 1 is a schematic representation of the control structure visible in the microscope after performing an etching. steps with a certain duration. A thin cover layer 5 (FIG. 2) is applied to the wafer 1 as the top layer. Openings 2 are arranged in the cover layer 5 through which the etching solution penetrates into the layer structure. Here, during the etching with isotropic with respect to the wafer plane

Direction of propagation etched a cavity 3 around the opening. After the etching, in addition to the cavities 3, there are still remnants of sacrificial layer 12 between the wafer and membrane layer. Under the optical microscope, a contrast between the regions with removed sacrificial material and the regions with sacrificial layer remnants 12 can be seen due to the small overall layer thickness. The openings 2 are arranged in the control structure according to a certain scheme. In the embodiment shown in Figure 1, the distance from two openings to each other gradually decreases. It is particularly advantageous if the radius r _L , calculated according to the formula r _L = 0.5 * D, is printed directly next to a pair of openings with a specific distance D, the distance D designating the distance between the openings of a pair of openings. In this way, the radius of a cavity can be read particularly advantageously after the undercut. According to the invention, a pair of openings together with the inscription 13 for the radius arranged above the pair of holes is referred to as partial region 11. According to the invention, any meaningful parameters can be used as labeling. For example, the diameter of the cavity above the pair of holes can also be printed.

When evaluating the individual structures, the value for the radius printed above the pair of openings is considered to have been reached when the circular openings formed around the opening begin to touch.

A section along a connecting axis between a pair of openings in FIG. 1 within a partial region 11 along line AB is shown in FIG. On a wafer 1, for example made of monocrystalline silicon, a sacrificial layer 4 of silicon dioxide is deposited, for example, ^~. Above the Sacrificial layer is deposited, for example, a cover layer 5 of po ^¬ lykristallinem silicon, holes 2 are omitted with the aid of a mask. Through these openings, the penetration of an etching solution is made possible, so that, starting from the openings, material of the sacrificial layer with a diameter that increases over time is created. During the formation of the openings 3, similar cavities arise in other areas on the wafer, which are located in the micromechanical components to be manufactured. The formation of these cavities takes place in a similar way to the formation of the cavities in the control structure.

FIG. 3 shows a wafer 1 which has chips 7, which are arranged in a grid pattern on the top and which represent the end products. After the chips have been completed, they are separated, for example by sawing in the space between the individual chips. This intermediate space, which is usually referred to as a saw frame 8, can serve to accommodate the control structures required for chip production, in particular to accommodate the control structure 9 according to the invention. This is particularly advantageous since the area of the saw frame for the control structures is freely available without restricting the area share of the products. In addition to the control structure according to the invention, further control structures 10 required for the conventional manufacturing process can also be placed in the area of the saw frame.

The control structure according to the invention enables the etching time to be checked during the production of cavities in micromechanical components. In this way, for example in the manufacture of pressure sensors, floating away of the membrane cover in the case of etching times which are too long or the formation of cavities which are too small can be effectively prevented.

Another advantage of the method according to the invention is that it is integrated into the standard process sequence of a semiconductor can be integrated easily. The method according to the invention can therefore be used in particular in the production of micromechanical components with integrated evaluation or control electronics.

Claims

claims

1. Control structure (9) for producing cavities (3) or undercut areas in micromechanical or microelectronic components by etching comprising one or more partial areas (11) arranged in the area of the control structure, the partial areas one or more individual structures (2 , 3) and possibly the inscriptions (13) and / or markings associated with the individual structures, the individual structures at least partially change their geometric shape during the etching and the individual structures of one subarea are geometrically modified compared to the individual structures of another subarea, so that the extent of the etching after and / or during the manufacture of the micromechanical component can be read off or evaluated quantitatively on the basis of an evaluation of the individual structures by comparing the partial areas after the cavities or undercut areas have been etched free.

2. Control structure according to claim 1, characterized in that at least two partial structures (2, 3) are contained in a partial area (11), each partial structure having an upper layer (5), a lower layer (1), a sacrificial layer (4) and has an etching opening (2) made in the upper layer, a cavity (3) arranged between the upper and lower layers being formed by removal of material from the sacrificial layer (4) and the spacing of the substructures in a subarea being selected such that when the desired etching dimension is reached, a connection of at least two cavities (3) occurs within a partial area.

3. Control structure according to claim 1 or 2, characterized in that the distance between the partial structures (2, 3) within a partial area (11) increases or decreases gradually with respect to the partial structure distance in an adjacent partial area.

4. Control structure according to at least one of claims 1 to 3, characterized in that the etching openings (2) in the upper layer (5) are arranged directly above the sacrificial layer, so that cavities (3) are formed during the etching starting from the etching openings enclose the cavity in a ring, or the etching openings are connected to etching channels running below the upper layer, so that the etching of the cavities takes place from the side.

5. Control structure according to at least one of claims 1 to 4, and that a control structure has 4 to 100 partial areas (11) and 2 to 5 individual structures (2, 3) are arranged in a partial area.

6. Coated wafer (1) comprising a plurality of interconnected chips (7) and one or more micromechanical and / or microelectronic components, the micromechanical and / or microelectronic components having at least one cavity (3) or undercut area that a control structure (9) according to claim 1 is present on one side of the wafer.

7. Coated wafer according to claim 6, characterized in that the control structure (9) in the sag frame (8) of the wafer (1) is arranged.

8. A method for producing a micromechanical and / or microelectronic component comprising at least one cavity (3) or undercut region, which is produced by one or more etching steps, characterized in that the extent of the etching steps is evaluated or read quantitatively, the evaluation or reading by means of a control structure (9) previously applied to the coated wafer (1).

9. The method for producing a micromechanical and / or microelectronic component as claimed in claim 10, d a d u r c h g e k e n n z e i c h n e t that the quantitative determination of the etching dimension is carried out optically or electrically without destroying the wafer.