HK1076539B - Support with integrated deposit of gas absorbing material for manufacturing microelectronic, microoptoelectronic or micromechanical devices - Google Patents

Description

Carrier for the manufacture of microelectronic, microoptoelectronic or micromechanical devices with integrated deposition of gas-adsorbing material

Technical Field

The invention relates to a carrier for the manufacture of microelectronic, microoptoelectronic or micromechanical devices, having a comprehensive deposit of a gas-adsorbing material.

Background

Microelectronic devices (also called integrated electronic circuits, in the field denoted by the acronym ICs) are the basis of the entire integrated electronics industry. The micro-optoelectronic devices include, for example, a new generation of Infrared Radiation (IR) sensors that, unlike conventional IR sensors, do not require low operating temperatures. These IR sensors are formed from an array of deposits of semiconductor material, such as silicon, disposed within a vacuum chamber. Micromechanical devices (the more well-known definition in this field being "micromechanical" or its abbreviation MMs) are in the developing stage of application, such as small sensors or actuators: typical examples of micro-mechanics are micro-accelerometers, which are used as sensors for activating automotive airbags; a micro-motor having a gear and sprocket with a size of several micrometers (μm); or optical switches in which a mirror surface, with dimensions in the order of tens of micrometers (μm), moves between two different positions, directing the light beam in two different directions, one corresponding to an "on" condition and the other corresponding to an "off condition of the optical circuit, all of these devices also being referred to hereinafter by the commonly defined names, i.e. solid state devices.

ICs are manufactured by a technique that involves the deposition of layers of material having different electrical (or magnetic) functions on a planar carrier, which is then selectively removed. The same deposition and selective removal techniques are also applied to micro-optoelectronic or micromechanical device structures. They are usually contained on a housing (housing) formed in this way with the same technology. The most common carrier in these products is a silicon "wafer" (known in the art as a "wafer") having a thickness of about 1mm and a diameter of up to 30 cm. A very large number of devices are built on each wafer; then, at the end of the manufacturing process, the single devices in the case of micromachines or the portions containing arrays of tens of devices in the case of IR sensors are separated from these wafers by mechanical or laser cutting.

The Deposition step is carried out by techniques such as Chemical Vapor Deposition, commonly defined by "Chemical Vapor Deposition" as "CVD"; physical Vapor Deposition, or "PVD" as defined by "Physical Vapor Deposition," the latter also commonly referred to as "sputtering. The selective removal is typically performed by chemical or physical attack applying a suitable mask, as is well known in the art.

Integrated circuits and micromachines are then encapsulated in polymeric, metallic or ceramic materials, mainly for mechanical protection purposes, before being inserted into the final target device (computer, automobile, etc.). In contrast, IR radiation sensors are typically contained within a chamber, one wall of which is defined as a "window" that is transparent to IR radiation.

In some kinds of integrated circuits, it is important to be able to control the diffusion of gases in solid state devices: for example in the case of ferroelectric memories where hydrogen diffusing through the device layers is able to reach the ferroelectric material (typically a ceramic oxide such as lead titanate-zirconate, strontium-bismuth tantalate or titanate, or bismuth-lanthanum titanate) changing its correct behavior.

More important is the control and elimination of gases in IR sensors and micromachines. In the case of an IR sensor, the gas that may be present in the chamber either absorbs part of the radiation or transfers heat by convection from the window to the array of silicon deposits, thereby modifying the measurement. In micromachines, the mechanical friction between the gas molecules and the moving parts, due to the very small dimensions of the latter, can cause the device to deviate measurably from its ideal operation; furthermore, polar molecules such as water can cause adhesion phenomena between the moving parts and other parts, e.g. the carrier, resulting in device failure. It is therefore of primary importance in IR sensors or micromachines with arrays of silicon deposits to be able to ensure that the housing maintains a vacuum state throughout the lifetime of the device.

To minimize the amount of gas in these devices, their production is typically performed in a vacuum chamber and an evacuation step is performed prior to encapsulation. However, this problem cannot be completely solved by this method because the same material constituting the device releases gas or gas permeates from the outside during the lifetime of the device.

In order to be able to remove gases that enter the solid state device during its lifetime at the same time, it has been proposed to use materials that are able to adsorb gases. These materials are composed of what are commonly referred to as "getters", typically metals such as zirconium, titanium, vanadium, niobium or tantalum, or their alloys with other transition elements, rare earths or aluminum, and desiccants, which have a strong chemical affinity for gases such as hydrogen, oxygen, water, carbon oxides and in some cases nitrogen; desiccant materials are used in particular for moisture adsorption, where predominantly oxides of alkali metals or alkaline earth metals are used. The use of gas-adsorbing materials in IC, in particular for hydrogen, is described, for example, in patent US-A-5,760,433 and published Japanese patent applications JP-11-040761 and JP-2000-40799; its use in IR sensors is illustrated, for example, in patent US 5,921,461; finally, the use of gas-adsorbing materials in micromachines is described, for example, in the document "Vacuum packaging for microsensors by glass-silicon anodic bonding" (H.Henmi et al, Vacuum packaging for microsensors by glass-silicon-inorganic bonding. technical journal Sensors and Actuators A, Vol.431994, pages 243 to 248.)

In the solid state device production step, a localized deposition of the gas adsorbing material can be obtained by CVD or sputtering. However, this process is not appreciated by the producers of these devices, since the deposition of the gas sorption material in the production of the devices implies the need to add a step of localized deposition of these materials throughout the process, which is carried out generally by depositing the resin, locally sensitizing the resin by radiation (generally UV), selectively removing the photosensitive resin, depositing the gas sorption material and subsequently removing the resin and the sorption material deposited thereon, leaving the gas sorption material deposited on the areas where the photosensitive resin has been removed. Moreover, the deposition of the gaseous absorbing material in the production line has the drawback of increasing the number of different treatment steps and the materials used therein, as well as the risk of "cross-contamination" between the different chambers used for carrying out the different steps, with a consequent possible increase in the number of rejects due to contamination.

Disclosure of Invention

The present invention aims to overcome the above-mentioned problems of the prior art and in particular to simplify the manufacturing process of solid state devices.

According to the invention, this object is achieved by a carrier for the manufacture of microelectronic, microoptoelectronic or micromechanical devices, which carrier has a comprehensive deposit of a gas-adsorbing material, consisting of a substrate with a mechanical support, on the surface of which substrate the gas-adsorbing material is deposited continuously or discontinuously, and a layer made of a material that is compatible with the production of microelectronic, microoptoelectronic or micromechanical devices or parts thereof, completely covers the deposit of the gas-adsorbing material.

The support of the present invention is in fact similar to the silicon wafers commonly used in the industry, but is "buried" below the surface, in the form of a continuous layer or discontinuous deposit, of a gas adsorbing material, on which microelectronic or microphotoelectronic devices are formed by the solid material deposition and removal techniques described above.

Drawings

The invention is described below with reference to the accompanying drawings, in which:

figure 1 shows a partially cut-away perspective view of a first possible carrier according to the invention;

figure 2 shows a partially cut-away perspective view of a second possible carrier according to the invention;

FIGS. 3-11 illustrate some methods of using the vectors of the present invention.

For the sake of clarity, in the figures of the support according to the invention, the invention is represented by a height-to-diameter ratio which is much greater than the actual size. Also in the drawings the carrier has been represented by a wafer geometry, which is a shallow disc of material, as this is the geometry commonly used in the manufacture of solid state devices, but which may also be different, for example square or rectangular.

Detailed Description

Fig. 1 shows a partial cut-away view of the simplest embodiment of the carrier of the invention. The carrier 10 comprises a substrate 11 which has only the function of mechanically supporting the carrier and forming devices thereon, the thickness of the carrier 10 (of the order of one millimeter) being almost entirely given by the thickness of the substrate. The substrate 11 has on one surface 12 a continuous layer 13 of gas adsorbing material 14, the upper surface of which is covered with another layer 15 of material 16, which is made of a material compatible with the IC or MM production process, and ICs or MMs are manufactured on the upper surface 17 of the layer 15.

The material of the substrate 11 may be metal, ceramic, glass or semiconductor, preferably silicon.

The material 14 can be any known material chosen from the materials commonly referred to as getters, which are able to adsorb various gas molecules, and desiccants, which are used in particular for moisture adsorption.

In the case of getter materials, it can be, for example, metals such as Zr, Ti, Nb, Ta, V; alloys between these metals or between these metals and one or more elements selected from Cr, Mn, Fe, Co, Ni, Al, Y, La and rare earths, such as the binary alloys Ti-V, Zr-V, Zr-Fe and Zr-Ni, the ternary alloys such as Zr-Mn-Fe or Zr-V-Fe, or alloys with more components. Preferred getter materials in this application are titanium, zirconium; alloy with a composition by weight of Zr 84% -Al 16%, manufactured and sold by the applicant under the name St 101^_(ii) a Alloy having a composition in weight% Zr 70% -V24.6% -Fe 5.4%, manufactured and sold by the applicant under the designation St707^_(ii) a An alloy having a weight percent composition of Zr 80.8% -Co 14.2% -TR 5% (where TR is the rare earth yttrium, lanthanum or mixtures thereof) made and sold by the applicant under the designation St 787; the getter material layer 13 can be obtained by different techniques, such as evaporation, deposition of metal-organic precursors, or by techniques known in the art as "laser ablation" and "electron beam deposition"; preferably the layer is obtained by sputtering.

In the case of desiccant materials, it is preferably chosen from alkali or alkaline earth metal oxides; more preferably, calcium oxide, CaO, is used which does not create safety or environmental concerns when manufacturing, using or handling the device containing it. The oxide layer 13 can be obtained, for example, by the so-called "reactive sputtering" technique, which deposits the alkali or alkaline-earth metal of interest in a rare gas atmosphere (generally argon) containing a low amount of oxygen, so as to convert the metal into an oxide during the deposition.

The thickness of layer 13 may be in the range between about 0, 1 and 5 μm: a lower thickness value than the indicated example results in a very large decrease in the gas adsorption capacity of the layer 13, whereas a double thickness value results in a longer deposition time without actually promoting the adsorption performance.

Material 16 is a material commonly used as a substrate in the production of solid state devices; which may be a so-called III-V material (e.g. GaAs or InP) or preferably silicon. Layer 16 can be obtained by sputtering, epitaxial (epitaxiy), CVD, or other techniques known in the art. The thickness of layer 16 is typically less than 50 μm, preferably in the range of about 1-20 μm. This layer performs two functions: the gas-adsorbing material is prevented from coming into contact with the gas prior to exposure (by partial or localized removal of the layer 16) and is used to anchor the layer subsequently deposited thereon for building up the IC, the micro-optoelectronic device or the MM, or it can itself be the layer forming these devices (for example a micromechanical moving part can be obtained within this layer by removing a part thereof). The upper surface of layer 16 can also be treated to modify its chemical composition, for example to form an oxide or nitride, depending on the subsequent operation of device production.

Fig. 2 shows a second possible embodiment according to the present invention; also in this case, the support is represented in a partially cut view, and moreover, for the sake of clarity, the transverse dimensions of the various deposits based on gas-adsorbing material have been exaggerated in this example. The carrier 20 comprises a substrate 21. In a region 22, 22 'of the substrate surface 23, a discontinuous deposition 24, 24' of a gas adsorbing material 25 is obtained; they are then covered with a layer 26 of material 27. The substrate 21 is of the same type and dimensions as the substrate 11 of the carrier 10; similar materials 25 and 27 are the same materials as materials 14 and 16, respectively, described with reference to device 10.

The deposits 24, 24'. are the same as the thickness of the layer 13 of the carrier 10. These deposits are discontinuous, however, with lateral dimensions typically below 500 μm, and with a width range that varies according to the final target device: for example if used in ICs, the lateral dimensions are in the range of a few microns or less, whereas in the case of MMs, these dimensions may be tens and hundreds of microns.

The layer 26 has a variable thickness, lower in the areas above the deposits 24, 24'. and higher in the areas to be removed from these deposits, and adheres to the surface 23 of these areas. The thickness of this layer in the region above the deposits has the same value as the layer 15 of the carrier 10, while in the regions remote from the deposits 24, 24', the thickness of these deposits is added to its thickness. To facilitate adhesion, layer 26 is preferably made of the same material as substrate 21; the preferred combination is silicon (single crystal or polycrystalline) for substrate 21 and silicon grown by epitaxy for layer 26.

Fig. 3 and 4 show possible applications of the carrier 10 in IC production. On the upper surface 17 of the carrier 10, for example, a silicon layer 15 is formed and, by means of well-known techniques, a solid microelectronic circuit is obtained, which is denoted as element 30, 30'. The carrier 10 is then cut along the dashed lines in fig. 3 to obtain a single IC device: one of which is illustrated in fig. 4, which shows an integrated circuit 40 obtained on a portion of the carrier 10, wherein the integrated circuit 40 has an integrated upper layer 13 formed with a gas-adsorbing material 14 "buried" below the surface 17. Layer 13 is capable of adsorbing gases, particularly hydrogen, because hydrogen can diffuse through the different layers of the device, thus preventing or reducing contamination of integrated circuit 40.

In the production case of MMs, structures are produced on the surface 17 of the carrier, which structures comprise micromechanical moving parts, as shown by the elements 50, 50'. When the manufacture of the structure 50, 50 '. multidot. (which comprises the leads for electrically connecting each single micromachine to the outside, but is not shown in the figures) is finished, the carrier is subjected to a localized removal operation of the layer 15, which is located in a region remote from the surface 17 of said structure, so as to form channels 51, 51'. multidot.. then a covering element 60 is placed on the carrier 10 thus treated (the assembly of which with the carrier 10 is shown in cross-section in fig. 6), which element is generally made of the same material as the substrate 11 and should be easily fixable on the surface 17 (preferably using silicon): this element 60 can have a cavity 61, 61 '. multidot.. (as shown in the figure), which corresponds to the region where the structure 50, 50'. multidot.. multidot.; in particular, when carrier 10 is fixed together with element 60, each cavity is able to obtain a space 62 containing a structure like 50, 50'. and a passage 51 allowing access to material 14, so as to bring material 14 into direct contact with space 62 and to be able to adsorb gases that may be present or released in this space over time. Finally, the assembly constituted by the carrier 10 and the element 60 is cut along the adhesion areas of them to obtain a single micromachine.

In the various micromechanical manufacturing processes outlined above, the local removal of the layer 15 is carried out before the step of manufacturing the structure 50, 50'.

In another form of the above process, the end result is a micromachine 70 as shown in fig. 7, and the carrier of the present invention is used as the element 60. In this case, the substrate on which the micromachine is formed is of a conventional type, without an integrated gas adsorption layer. The carrier 10 of the invention is subjected to a treatment of partial removal of the layer 15, so as to simultaneously form a cavity 71 constituting a space 72 for accommodating the mobile structure 73 and a passage allowing access to the material 14.

The use of a carrier of type 20 is only shown in relation to the use as a carrier for forming a micromachine on a surface (similar to the applications represented in fig. 5 and 6), but it is clear that this can also be used as a carrier for IC production (as explained with reference to fig. 3 and 4) or as a covering element in a micromachine (as explained with reference to fig. 7). The carrier 20 is treated in correspondence with the deposits 24, 24 '. to locally remove the layer 26, so as to obtain channels 80, 80'. to the carrier, as shown in the part of figure 8, in preparation for the production of the next step of the micromachine. The mobile structure of fig. 9 (represented by elements 90, 90') is then formed on this carrier; thereafter, the covering element 100 is fixed to the carrier 20, in a region that is kept spaced from the mobile structure 90, 90 'and from the channel 80, 80', so as to obtain an assembly 101 as partially shown in fig. 10; finally, the assembly 101 is cut along the lines (dashed lines in the figure) constituting the adhesion areas between the carrier 20 and the element 100, obtaining the micromachine 110 partially shown in fig. 11.

Depending on the method used, type 20 supports must be manufactured with the end application known. In particular, in the case of micromechanics in particular, it is important to know the lateral dimensions of the moving structure (50, 50 '. multidot., 73 or 90, 90'. multidot. and the cavities (61, 61 '. multidot.. or 71) to be produced next, and the lateral dimensions of the deposits 24, 24'. multidot. and the corresponding distances; this ensures that the passages allowed to reach the gas adsorbing material do not interfere with the moving structure and that they are contained within the peripheral extent of the space 62 or 72 within which the micromachines are accommodated. A correct dimensioning can be achieved from the producer of the final circuit, the drawing, even pre-prepared by obtaining the devices to be manufactured on the carrier 20.

Claims (21)

1. A carrier (10; 20) for the manufacture of microelectronic, microoptoelectronic or micromechanical devices, provided with a comprehensive deposit of gas-adsorbing material, comprises a substrate (11; 21) having a mechanical support function; a continuous (13) or discontinuous (24, 24'. multidot..) deposit of gas adsorbing material (14; 25) located on the surface (12; 23) of the substrate; and a layer (15; 26) completely covering said gas-adsorbing material deposit, made of a material (16; 27) compatible with the manufacture of microelectronic, microoptoelectronic or micromechanical devices or parts thereof.

2. Carrier (10) according to claim 1, wherein said deposits (13) of gas adsorbing material are located continuously on the entire surface (12) of said substrate (11).

3. Carrier (20) according to claim 1, wherein the deposit of gas adsorbing material is in the form of a discontinuous deposit (24, 24'. ·).

4. Carrier according to claim 1, wherein the substrate (11; 21) is made of a material selected from metal, ceramic, glass or semiconductor.

5. A carrier according to claim 4, wherein said material is silicon.

6. The carrier according to claim 1, wherein said gas adsorbing material is a getter material.

7. Support according to claim 6, wherein said getter material is selected among: the metals Zr, Ti, Nb, Ta, V, alloys between these metals, or alloys of these metals with one or more elements selected from Cr, Mn, Fe, Co, Ni, Al, Y, La and rare earths.

8. Support according to claim 7, wherein said getter material is titanium.

9. Support according to claim 7, wherein said getter material is zirconium.

10. Support according to claim 7, wherein said getter material is an alloy with a weight percentage composition Zr 84% -Al 16%.

11. Support according to claim 7, wherein said getter material is an alloy having a weight percentage composition Zr 70% -V24.6% -Fe 5.4%.

12. Support according to claim 7, wherein said getter material is an alloy having a weight percentage composition Zr 80.8% -Co 14.2% -TR 5%, where TR denotes the rare earths yttrium, lanthanum or mixtures thereof.

13. The carrier according to claim 1, wherein said gas adsorbing material is a desiccant material.

14. The carrier according to claim 13, wherein said desiccant material is selected from oxides of alkali metals or alkaline earth metals.

15. A carrier according to claim 14, wherein the desiccant material is calcium oxide.

16. A carrier according to claim 1, wherein said continuous or discontinuous deposit of gas adsorbing material has a thickness in the range of 0.1-5 μm.

17. A carrier according to claim 1, wherein said material compatible with the manufacture of microelectronic, microoptoelectronic or micromechanical devices or parts thereof is a semiconductor material.

18. A carrier according to claim 17, wherein said material is silicon.

19. Carrier according to claim 1, wherein the thickness of said layer of a material compatible with the fabrication of microelectronic, microoptoelectronic or micromechanical devices or parts thereof is lower than 50 μm.

20. A carrier according to claim 19, wherein said thickness is in the range of 1-20 μm.

21. Use of the carrier of claim 1 as a covering element (60) in the production of micromechanical devices (70).