Method for producing a coupled wafer

Abstract

The invention relates to a method for producing (200) a coupled wafer (100), wherein the method comprises the following steps: a) providing (210) a first MEMS wafer (120) having structures (121, 122) for actuators (121') and / or sensors (122'); b) independently thereof, providing (220) a baseplate wafer (130); and c) connecting (240) a first side (120a) of the first MEMS wafer (120) to a first side (130a) of the baseplate wafer (130). Furthermore, the invention relates to the use of the method for producing a coupled wafer.

Description

[0001] Description

[0002] title

[0003] Technical area

[0004] The invention relates to a method for producing a coupled wafer, in particular a method for parallelizing the production of at least two wafer modules for MEMS components. Furthermore, the invention relates to the use of the method for producing a coupled wafer.

[0005] State of the art

[0006] DE 10 2020 209 934 A1 relates to a manufacturing method for a micromechanical component and a corresponding micromechanical component. The micromechanical component is formed from an ASIC component and a MEMS component. An ultra-thin MEMS component vertically integrated with an ASIC component and a corresponding manufacturing method are disclosed, wherein the thickness of an overall stack can be less than 300 μm. It is disclosed that the process steps can also be performed on a wafer basis, thus using a MEMS wafer and an ASIC wafer.

[0007] WO 2006 / 012255 A1 relates to a device comprising a first substrate, one or more microelectromechanical systems (MEMS) connected to the first substrate, a second substrate connected to the first substrate, and one or more passive components connected to the second substrate. It is disclosed that, in one embodiment, a MEMS wafer can be bonded to a passive component wafer. The advantage of such a wafer bond is that parallel production of the modules to be manufactured is possible. DE 10 2016 110 862 A1 discloses a module having a lower and an upper module component that are stacked one above the other and electrically contacted with one another.To produce a large number of such modules, it is proposed to use a lower wafer and an upper wafer with the corresponding module components. The wafers are connected to each other, for example, by eutectic bonding, an electrically conductive adhesive bond, sintering, or soldering, and then singulated. Components are embedded in the module components, which can be semiconductor chips, passive components, sensors, digital chips, or MEMS components.

[0008] KR 100 888 080 B1 refers to a production process for a micromirror array with comb drives and mirror plates.

[0009] Disclosure of the invention

[0010] According to the invention, a method for producing a coupled wafer is proposed, in which the following method steps are carried out: a) providing a first MEMS wafer with structures for actuators and / or sensors, b) providing a base plate wafer independently thereof and c) connecting a first side of the first MEMS wafer to a side of the base plate wafer.

[0011] This makes it possible to construct the MEMS wafer in a modular manner and ultimately combine the individual modules into an overall system.

[0012] In an advantageous development of the method proposed by the invention, a second MEMS wafer, in particular a mirror plate wafer, with structures for mirror plates is provided independently of the provision of the first MEMS wafer and the provision of the base plate wafer, and a second side of the first MEMS wafer, different from the first side, with structures for actuators and / or sensors, is connected to a side of the second MEMS wafer. Thus, depending on the modularization, i.e., depending on the process variants, the method proposed by the invention can provide either a wafer process flow for the modular base plate and the actuator or a process flow for the modular base plate, the actuator, and the mirror plate.

[0013] In an advantageous embodiment of the method proposed according to the invention, the first side of the first MEMS wafer is connected to the side of the base plate wafer before the second side of the first MEMS wafer is connected to the side of the second MEMS wafer, in particular configured as a mirror plate wafer.

[0014] In an advantageous development of the solution proposed according to the invention, before one of the wafers, ie the first MEMS wafer, in particular designed as an actuator wafer, base plate wafer and / or the second MEMS wafer, in particular designed as a mirror plate wafer, is provided, the respective wafer is manufactured, wherein the manufacture of at least two of these wafers takes place at least partially simultaneously, ie in temporal overlap

[0015] Advantageously, the method proposed according to the invention is designed such that by connecting a first side of the first MEMS wafer to a side of the base plate wafer, one or more connection points are formed which are suitable for transmitting electrical signals.

[0016] Furthermore, the invention relates to a method for producing MEMS chips with one or more MEMS components, wherein the following method steps are carried out: a) producing a coupled wafer comprising the first MEMS wafer and the base plate wafer by a method as described above and b) singulating the coupled wafer into a plurality of MEMS chips.

[0017] According to the invention, the coupled wafer is produced according to the above-mentioned method, wherein the coupled wafer further comprises the second MEMS wafer, in particular designed as a mirror plate wafer.

[0018] In an advantageous development of the above-mentioned method, after the coupled wafer has been produced and before the coupled wafer is separated, the structures for the actuators and / or the structures for the mirror plates are exposed.

[0019] In an advantageous further development of this method, the structures for the sensors are further exposed before the separation process of the coupled wafer.

[0020] Advantages of the invention

[0021] The solution proposed according to the invention provides a method by which the overall throughput time for producing an MMA wafer can be considerably reduced and the risk of low yields is decisively reduced. The MMA wafers are constructed in modules, and at the end of the process chain the individual modules are combined to form an overall system. For this purpose, the process flow required to produce an MMA wafer is divided into the individual process flows for the “base plate”, “actuator” and “mirror plate” modules. This allows these modules to be manufactured independently of one another using their own wafer process flows, with the wafer process flows being run independently of one another. The mechanical connection as well as electrical and thermal contacting of the module wafers is carried out using a wafer bonding process, for example using the layer systems Si-Si, Au-Au, Al-Al, Cu-Cu or Al-Ge.The process proposed by the invention can significantly shorten the overall throughput time and drastically reduce the risk of yield losses due to the increasingly complex wafer structure. Furthermore, it is worth emphasizing that individual process or design changes only affect one module and can therefore be reproduced more quickly.

[0022] The method proposed by the invention expands the manufacturing possibilities as well as the degrees of freedom in process control with regard to the individual, independently producible wafer modules. Since the various wafer modules are manufactured separately, processes can be applied to a first MEMS wafer that are not possible for the production of the second MEMS wafer, for example. For example, the second MEMS wafer could contain a metal layer, such as aluminum, that can withstand only moderate temperatures of approximately 450°C, while the first MEMS wafer requires high temperatures, such as 1100°C, during its production, for example, to carry out furnace processes and complete this module.By bonding the MEMS wafer chosen as an example and the second MEMS wafer, aluminum is finally added in a single process at a temperature of 1100 °C, which would not be possible with a single, non-modular wafer manufacturing process. The method proposed according to the invention can, for example, create MEMS structures that cannot be manufactured on a single wafer due to temperature limitations or etching gas resistance.

[0023] Short description of the drawings

[0024] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0025] They show:

[0026] Figure 1.1 shows a coupled wafer comprising a first MEMS wafer, a second MEMS wafer and a base plate wafer,

[0027] Figure 1.2 shows a released coupled wafer with the modules according to Figure 1 A and

[0028] Figure 2 shows a method for producing a coupled wafer.

[0029] Figure 3 shows a schematic structure of a kit for variants of a first MEMS wafer, a second MEMS wafer and a base plate wafer,

[0030] Figure 3.1 shows a first embodiment of a coupled wafer,

[0031] Figure 3.2 shows another embodiment of a coupled wafer and

[0032] Figure 3.3 shows a third embodiment of a coupled wafer. Embodiments of the invention

[0033] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0034] The illustration according to Figure 1 shows a coupled wafer 100 with, for example, a second MEMS wafer 110, a first MEMS wafer 120 and a base plate wafer 130, which has at least one wiring level, arranged one above the other.

[0035] MEMS micromirror arrays (MMAs) use samples with different configurations. Such samples do not represent a fully functional component, but merely a subcomponent of an overall unit. A sample, for example, for a mirror, primarily comprises the mirror part; all remaining components are dummy elements. Each of the samples used serves to evaluate partial aspects of functionality, technical feasibility, and overall risk. Each of the samples used therefore requires different functionalities, such as various wiring patterns running in at least one layer, line routing, and contacts.

[0036] The samples can be divided into various combinations of the three main modules, namely the base plate, actuators, and mirror plate. Within the three main modules, these are in turn divided into various variants, such as a base plate with integrated through-silicon vias (TSV), a base plate with additional internal rewiring for ASICs without through-silicon vias, or a base plate in various thicknesses, etc. According to the invention, it is proposed to significantly shorten the overall throughput time by parallel production of the three main modules, namely a first MEMS wafer 120, a second MEMS wafer 110, and the base plate wafer 130 with at least one wiring level during production 200. Each of the aforementioned main modules is shown in its design variants (cf. illustration according to Figures 3 to 3.3) manufactured separately and then connected, in particular bonded, to the other two main module variants depending on the sample and requirements. The connection is in particular designed as a bond connection. For example, different actuator design variants can be bonded to a base plate which wires the electrical signals to contact pads on the wafer surface in order to be able to electrically characterize the actuator variants more quickly and easily. To characterize the actuator in the target design, in which contact is made on the back of a wafer, one and the same actuator can be bonded to a base plate variant which relays the electrical signals through the base plate to contact pads on the back of the wafer. The connection can also be purely mechanical in individual applications, and can optionally also be electrically or thermally conductive.In certain applications, electrical contacts can in principle also be introduced after the entire MEMS wafer has been completed. Various combinations of main modules can thus be combined to flexibly create a wide variety of product variants. At the end of the process chain, the MEMS elements 105 are exposed 260, for example, in the form of micromirrors. Partial exposure 260 of the wafers 110, 120, 130 to be produced can also be performed during the manufacturing process.

[0037] Since the individual main modules mentioned above are manufactured in parallel, this results in a significantly shortened overall process time; furthermore, the reduction in consecutive process steps also increases yield. Methods that establish electrical and thermal contact in addition to the mechanical connection are suitable for bonding. Such a bond connection can be achieved, for example, with the Al-Al, Au-Au, Cu-Cu, Al-Ge, or Si-Si systems using direct bonding.

[0038] The illustration in Figure 1.1 shows that a coupled wafer 100 is manufactured in parallel production. In the exemplary illustration in Figure 1.1, the coupled wafer 100 comprises three adjacently arranged within a frame 144 for MEMS chips 101: a second MEMS wafer 110, a first MEMS wafer 120, and a base plate wafer 130, which have at least one wiring level. Parallel production results in a three-stage production 200 of the coupled wafer 100. Essentially, the individual modules are arranged vertically one above the other, i.e., a second MEMS wafer 110, a first MEMS wafer 120, and the base plate wafer 130. Figure 1.1 shows that the second MEMS wafer 110 comprises a first side 110a and an opposite second side 110b. The first MEMS wafer 120 arranged underneath comprises a first side 120a and a second side 120b, while the base plate wafer 130 arranged underneath it comprises a first side 130a and a second side 130b. Between the individual modules formed by the superimposed second MEMS wafer 110, first MEMS wafer 120, and base plate wafer 130 are regions 142 which are filled during production within sacrificial regions 146 for subsequent silicon oxide sacrificial layer etching.

[0039] The second MEMS wafers 110 are provided on their upper side with structures 111, from which mirror plate surfaces 111' (see illustration in Figure 1.2) are produced. With respect to the first MEMS wafers 120, these are covered with structures 121 for actuators, from which actuators 121' are produced as the process progresses. The same applies to structures 122 for sensors, from which sensors 122' are produced as the process chain continues.

[0040] The base plate wafer 130 comprises a base plate 131 with at least one wiring level and metal contacts 140 provided on the second side 130b.

[0041] Figure 1.2 shows a free-standing, coupled wafer 100' with the three modules according to Figure 1.1.

[0042] A comparison of Figures 1.1 and 1.2 reveals that the sacrificial regions 146 for silicon oxide sacrificial layer etching, which are present in Figure 1.1, are missing in the illustration according to Figure 1.2. The step of connecting 240 a second side 120b of the first MEMS wafer 120 to a first side 130a of the base plate wafer 130 is performed.

[0043] In the event that, in addition to the first MEMS wafer 120 and the base plate wafer 130, a second MEMS wafer 110, in particular configured as a mirror plate wafer, with structures for mirror plates 111 is used, a bond connection is formed within the scope of a connection 250, for example, between a second side 120b of the first MEMS wafer 120, which is different from the first side 120a, and a second side 110b of the second MEMS wafer 110.

[0044] The illustration in Figure 2 schematically shows a method 200 for producing a coupled wafer 100 with its essential method steps. According to the method 200 for producing a coupled wafer 100, a first MEMS wafer 120, which is designed in particular as an actuator wafer, is first provided 210, and a base plate wafer 130 is then provided 220. Optionally, a second MEMS wafer 110, designed in particular as a mirror plate wafer, can also be provided 230.

[0045] A connection 240 is made, in particular the formation of a bond connection between one of the sides 120a, 120b of the first MEMS wafer 120 and one of the sides 130a, 130b of the base plate wafer 130.

[0046] Subsequently, the first MEMS wafer 120, in particular designed as an actuator wafer, is optionally connected to one of the sides 110a, 110b of the second MEMS wafer 110, in particular designed as a mirror plate wafer, by means of a connection 250.

[0047] Finally, as will be shown below, a separation 260 of the components MEMS chips 101 in the form of the micromirrors (MEMS element?) 105 takes place before a separation 270 of coupled wafers 100 takes place.

[0048] Figure 3 shows a schematic representation of a kit 150. Within this modular kit 150, several design variants are available for the configuration of each of the second MEMS wafers 110, the first wafer 120, and the base plate wafer 130. For example, with respect to the second MEMS wafer 110, a first variant 110.1 and a second variant 110.2 can be used.

[0049] Regarding the first MEMS wafer 120, three versions are available

[0050] 120.1, 120.2, and 120.3 are available. Regarding the base plate wafer 130, with at least one wiring level, various variants 130.1, 130.2, and 130.3 can be used.

[0051] The sequence of Figures 3.1, 3.2, and 3.3 illustrates various embodiments of coupled wafers 100. Figure 3.1, for example, shows a coupled wafer 100 whose second MEMS wafer 110 comprises the first variant 110.1. The underlying first MEMS wafer 120 is used in the form of its first variant 120.1; furthermore, the first variant 130.1 of the base plate wafer 130 is incorporated into the coupled wafer 100, as shown in Figure 3.1. Figure 3.2, in contrast, shows the exemplary structure of a coupled wafer 100, in which the second variant 110.2 is used as the second MEMS wafer 110, whereas the first variant 120.1 of the first MEMS wafer 120 is used as the first MEMS wafer 120, and the second variant 130.2 is used as the base plate wafer 130. In the third embodiment shown in Figure 3.3, the first variant 110.1 of the second MEMS wafer 110 is used in the plane in which the second MEMS wafer 110 is arranged.The second embodiment variant 120.2 is used as the first MEMS wafer 120, and the third embodiment variant 130.3 is used as the base plate wafer 130. All examples of the coupled wafer 100 according to Figures 3.1, 3.2, and 3.3 show a substantially vertical structure.

[0052] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

Claims

Claims 1 . A method for producing (200) a coupled wafer (100) comprising the following steps: a. providing (210) a first MEMS wafer (120) having structures (121, 122) for actuators (121') and / or sensors (122'); b. providing (220) a base plate wafer (130) independently thereof; and c. connecting (240) a second side (120b) of the first MEMS wafer (120) to a first side (130a) of the base plate wafer (130) such that a coupled wafer (100) is obtained.

2. The method according to claim 1, wherein the method comprises the following further steps: a. providing (230) a second MEMS wafer (110) with structures (111) for mirror plates (111') independently of the provision (210) of the first MEMS wafer (120) and the provision (220) of the base plate wafer (130), and b. connecting (250) a second side (120b) of the first MEMS wafer (120), which is different from the first side (120a), to a second side (110b) of the second MEMS wafer (110).

3. The method of claim 2, wherein the joining of the first side (120a) of the first MEMS wafer (120) to the first side (130a) of the base plate wafer (130) takes place before the joining (250) of the second side (120b) of the first MEMS wafer (120) to the second side (110b) of the second MEMS wafer (110).

4. The method according to any one of the preceding claims, wherein the provision (210, 220, 230) of one of the wafers (110, 120, 130) comprises a production of the respective wafer (110, 120, 130) and the production of at least two of the wafers (110, 120, 130) takes place in a temporally overlapping manner.

5. Method according to one of the preceding claims, wherein by connecting (240) a first side (120a) of the first ME MS wafer (120) to a first side (130a) of the base plate wafer (130), one or more connection points, in particular bond connections, are formed which are suitable for transmitting electrical signals.

6. Method according to one of the preceding claims, characterized in that the first MEMS wafer (120) is preferably formed as an actuator wafer and the second MEMS wafer (110) is preferably formed as a mirror plate wafer.

7. A method for manufacturing MEMS chips (101) with one or more MEMS components (105), comprising the following steps: a. manufacturing (200) a coupled wafer (100) comprising the first MEMS wafer (120) and the base plate wafer (130) by a method according to one of claims 1 to 6; and b. singulating (270) the coupled wafer (100, 100') into a plurality of MEMS chips (101).

8. The method of claim 7, wherein the manufacturing (200) of the coupled wafer (100) is carried out according to claim 2 and preferably one of claims 3 to 6 and the coupled wafer (100) further comprises the second MEMS wafer (110).

9. The method according to claim 8, wherein after the production (200) of the coupled wafer (100) and before the singulation (270) of the coupled wafer (100), a release (260) of the structures (121) for the actuators (121 ') and / or the structures (111) for the mirror plates (111 ') takes place.

10. The method according to claim 9, characterized in that the exposure (260) or the at least partial exposure (260) takes place during the manufacturing processes of the structures (111, 121) by means of silicon oxide or silicon oxide sacrificial layer etching.

11. Method according to claims 8 to 10, characterized in that a release (260) of the MEMS elements (105), in particular the micromirrors, takes place.

12. The method according to claims 6 and 9, wherein before or during the singulation (270) of the coupled wafer (100), a clearance (260) of the structures (122) for the sensors (122') is carried out.

13. Use of the method according to one of claims 1 to 12 for producing (200) a coupled wafer (100) comprising at least a first MEMS wafer (120) and a base plate wafer (130).

Images