Patent Application
20240027488
The present invention relates to the technical field of semiconductors, and more particularly relates to an inertial sensor and a forming method thereof.
An inertial sensor manufactured based on a micro-electro-mechanical system (MEMS) has drawn extensive attention due to its advantages such as simple structure, good compatibility with a microelectronics manufacturing process, mass manufacturing, and small volume.
In the existing process, a forming method of the inertial sensor generally includes: first providing a first substrate and a second substrate which are mutually bonded; and then, etching the second substrate to form a movable comb tooth structure and suspending the movable comb tooth structure above the first substrate. However, the inertial sensor prepared based on the existing process usually has the problem that side walls of comb teeth of the movable comb tooth structure are damaged.
An objective of the present invention is to provide a forming method of an inertial sensor, so as to alleviate damage to side walls of comb teeth of a formed movable comb tooth structure.
To solve the above technical problem, the present invention provides a forming method of an inertial sensor, which includes:
Optionally, a thickness of the thin film layer is less than a depth of the trench.
Optionally, after bonding the second conducting material layer and the first conducting material layer, the forming method further includes: forming a plurality of electrodes on the second conducting material layer, where at least part of the plurality of electrodes are used for being electrically connected to the movable comb tooth structure.
Optionally, first openings are further formed in the first conducting material layer, and when etching the second conducting material layer, second openings are further formed in the second conducting material layer. The second openings communicate with the first openings to form separation openings, and the plurality of electrodes are electrically isolated from each other by the separation openings.
Optionally, the first substrate further includes a first base and a first insulating layer formed between the first base and the first conducting material layer.
Optionally, a first cavity is formed in the first conducting material layer, and after bonding the first conducting material layer and the second conducting material layer, the comb tooth region is suspended above the first cavity.
Optionally, the second conducting material layer is further provided with a cantilever region, a second cavity and a stopper are further formed in the first conducting material layer, and after bonding the first conducting material layer and the second conducting material layer, the second cavity and the stopper are both located directly under the cantilever region.
Optionally, the second substrate further includes a second base and a second insulating layer formed between the second base and the second conducting material layer. Before etching the second conducting material layer, the forming method further includes: grinding the second base to partially remove the second base, then etching the remaining second base by an etching process, stopping etching at the second insulating layer, and then removing the second insulating layer to expose the second conducting material layer.
Optionally, the method for etching the second conducting material layer to form the movable comb tooth structure includes: adopting a plasma etching process for etching the second conducting material layer.
Another objective of the present invention is to provide an inertial sensor, which includes:
Optionally, a first cavity is further formed in the first conducting material layer, and the movable comb tooth structure is suspended above the first cavity.
Optionally, the second conducting material layer is further provided with a cantilever region, a second cavity and a stopper are further formed in the first conducting material layer, and the second cavity and the stopper are both located directly under the cantilever region.
In the forming method of the inertial sensor provided by the present invention, the trench is formed in the comb tooth region of the second conducting material layer, so that the movable comb tooth structure formed in the comb tooth region can be spaced from the first conducting material layer; and the thin film layer is further arranged at the bottom of the trench, and the thin film layer can be used for realizing etching blocking while etching the second conducting material layer, so that etching on the second conducting material layer can be stopped at the thin film layer without damaging the first conducting material layer below. Moreover, when etching the second conducting material layer to form the movable comb tooth structure, the bottoms of the comb teeth of the movable comb tooth structure are all fixed to the thin film layer, thereby avoiding damage to the side walls of the comb teeth due to torsion of the comb teeth during etching. In addition, in the forming method provided by the present invention, the thin film layer with a small thickness can be arranged, and thus, only a small etching amount is required for removing the thin film layer, and at this time, other film layers cannot be largely eroded, which is conducive to guaranteeing stability of modules in a device.
Reference numerals are as follows: 100—first substrate; 110—first base; 120—first insulating layer; 130—first conducting material layer; 130a—first cavity; 130b—second cavity; 130c—first opening; 131—stopper; 200—second substrate; 210—second base; 220—second insulating layer; 230—second conducting material layer; 231—movable comb tooth structure; 230a—trench; 240—thin film layer; 400—electrode; 510—separation opening; 600—seal-capping base plate; 610—seal-capping cavity; and 700—bonding sealing ring.
As mentioned in the background, side walls of comb teeth of a movable comb tooth structure of an inertial sensor prepared by the existing forming method of the inertial sensor are likely to be damaged. Thus, the inventors of the present invention carried out researches and found that one important reason why the side walls of the comb teeth of the movable comb tooth structure are likely to be damaged is that in the process of etching a second substrate to form the movable comb tooth structure, a torsion space of the movable comb tooth structure is released along with constant etching, causing the movable comb tooth structure to easily twist during etching, and at this time, the side walls of the comb teeth are likely to suffer from etching damage.
Therefore, the present invention provides an inertial sensor and a forming method thereof. The forming method includes the following steps.
Step S100: A first substrate with a first conducting material layer and a second substrate with a second conducting material layer are provided, a trench is formed in a surface of a comb tooth region of the second conducting material layer, and a thin film layer is further formed at a bottom of the trench.
Step S200: The second conducting material layer and the first conducting material layer are mutually bonded.
Step S300: At least the comb tooth region of the second conducting material layer is etched, etching is stopped at the thin film layer to form a movable comb tooth structure, and bottoms of comb teeth in the movable comb tooth structure are all fixed to the thin film layer.
Step S400: The thin film layer is removed.
The inertial sensor and the forming method thereof provided by the present invention are further described in detail below in combination with the drawings and specific embodiments. The advantages and features of the present invention will be more clear according to the following description. It should be noted that the drawings all adopt a very simplified form and use an inaccurate scale, which are only intended to conveniently and clearly assist in describing the purposes of the embodiments of the present invention. In addition, relative terms shown in the drawings such as “above”, “below”, “top”, “bottom”, “over” and “under” can be used for describing relationships among modules, and these relative terms are intended to cover different orientations among elements besides the orientations depicted in the drawings. For example, if a device is inverted relative to a view in the drawings, it is described that an element above the other element is located below the other element now.
In this embodiment, the forming method of the inertial sensor may include the following step S100 to step S400. The detailed description is made below in combination with
In step S100, referring to
A trench 230a is formed in a surface of a comb tooth region A of the second conducting material layer 230, and a thin film layer 240 is formed at a bottom of the trench 230a. A material of the thin film layer 240, for example, includes silicon oxide, and the comb tooth region A of the second conducting material layer 230 is used for preparing the movable comb tooth structure. In this embodiment, the thin film layer 240 is only located in the trench 230a, and a thickness of the thin film layer 240 is less than a depth of the trench 230a, so that a top surface of the thin film layer 240 is not higher than that of the second conducting material layer 230. For example, the thickness of the thin film layer 240 may be only a half of the depth of the trench 230a, and the depth of the trench 230a is, for example, 0.5 μm-1.5 μm.
Further, the second conducting material layer 230 is further provided with a cantilever region B, the comb tooth region A is located beside the cantilever region B, and a part of the cantilever region B can constitute a mass block of the inertial sensor.
Further, a first cavity 130a is further formed in the first conducting material layer 130. The first cavity 130a corresponds to the comb tooth region A of the second conducting material layer 230 (i.e., after subsequent bonding of the first substrate 100 and the second substrate 200, the first cavity 130a is aligned with the comb tooth region A). In addition, a second cavity 130b is further formed in the first conducting material layer 130. The second cavity 130b corresponds to the cantilever region B of the second conducting material layer 230 (i.e., after subsequent bonding of the first substrate 100 and the second substrate 200, the second cavity 130b is aligned with the cantilever region B), thereby providing a vibration space for the cantilever region B.
Further, a stopper 131 may also be arranged in the first conducting material layer 130. The stopper 131 corresponds to the cantilever region B of the second conducting material layer 230, so as to limit a vibration range of the cantilever region B, and avoid the problems such as fracture due to excessive vibration of the cantilever region B. Specifically, after subsequent bonding of the first substrate 100 and the second substrate 200, the stopper 131 is located below the cantilever region B, and in this embodiment, the stopper 131 may be further arranged on an edge of the second cavity 130b, so as to perform stopping from the edge of the cantilever region B. Further, a top surface of the stopper 131 is not higher than that of the first conducting material layer 130.
Continuing referring to
In this embodiment, trenches and thin film layers are also formed in positions, corresponding to the first openings 130c, of the second conducting material layer 230.
Continuing referring to
In addition, before forming the first conducting material layer 130, a first insulating layer 120 may also be formed on the first base 110. After forming the first insulating layer 120, the first conducting material layer 130 is formed on the first insulating layer 120, and when etching the first conducting material layer 130 for patterning, the first insulating layer 120 may also be used as an etching stop layer. A material of the first insulating layer 120, for example, includes silicon oxide.
Continuing referring to
Further, before forming the second conducting material layer 230, a second insulating layer 220 is further formed on the second base 210, and after forming the second insulating layer 220, the second conducting material layer 230 is formed on the second insulating layer 220. A material of the second insulating layer 220, for example, includes silicon oxide.
In an optional solution, a material of the second conducting material layer 230 may be the same as that of the first conducting material layer 130. In this embodiment, the material of the second conducting material layer 230 is, for example, an ion-doped silicon material, and a resistance value of the second conducting material layer 230 is, for example, between 0.01Ω and 0.02Ω Compared with the low-resistance second conducting material layer 230, the second base 210 has a higher resistance value, for example, the resistance value of the second base 210 is between 8Ω and 12Ω.
In step S200, referring to
The specific process of bonding the second substrate 200 and the first substrate 100 is to mutually bond the first conducting material layer 130 in the first substrate 100 and the second conducting material layer 230 in the second substrate 200. In this embodiment, both the first conducting material layer 130 and the second conducting material layer 230 are made of the ion-doped silicon material, that is, the first substrate 100 and the second substrate 200 are in silicon-silicon direct bonding, and the bonding process is simple and has high bonding force.
The comb tooth region A of the second conducting material layer 230 corresponds to the first cavity 130a of the first conducting material layer 130, and thus, after bonding the first substrate 100 and the second substrate 200, the trench 230a is located above the first cavity 130a. In addition, the cantilever region B of the second conducting material layer 230 is located above the second cavity 130b.
In the subsequent process, the second conducting material layer 230 is patterned to form the movable comb tooth structure. In this embodiment, the second conducting material layer 230 further has the second insulating layer 220 and the second base 210, and thus, before patterning the second conducting material layer 230, the forming method further includes: the second base 210 and the second insulating layer 220 are removed.
Details are shown in combination with
Specifically, the second base 210 is partially removed by the grinding process, and part of the second base 210 is retained, which can effectively relief mechanical stress of the grinding process acting on the second conducting material layer 230, and avoid hide cracks in the second conducting material layer 230. Then, the remaining second base 210 is etched by the etching process, and when etching the remaining second base 210, the second insulating layer 220 can be utilized for constituting the etching stop layer, thereby avoiding losses of the second conducting material layer 230 below under the protection of the second insulating layer 220, and effectively guaranteeing accurate control over the thickness of the second conducting material layer 230. Further, the remaining second base 210 can be etched by a plasma etching process, so as to improve etching precision of the second base 210. Then, the second insulating layer 220 can be removed by a wet etching process. For example, the material of the second insulating layer 220 may include silicon oxide, and thus, an etching agent adopted in the wet etching process for removing the second insulating layer 220 is, for example, hydrofluoric acid solution.
In an optional solution, before grinding the second base 210, the forming method further includes: a trim process is performed on an edge of the second base 210, so as to remove an edge part of the second base 210, and accordingly, when subsequently performing the grinding process on the second base 210, the problem that the edge part of the thinned second base 210 is suspended and is likely to fracture can be avoided.
In step S300, referring to
Specifically, a pattern of the movable comb tooth structure can be defined by a second mask layer, and the second conducting material layer 230 is etched based on the second mask layer, so as to form the movable comb tooth structure 231, and the method, for example, includes the following steps.
It should be noted that by arranging the thin film layer 240, on the one hand, the function of etching blocking can be realized, and accurate control over the etching process of the second conducting material layer 230 is improved; and on the other hand, based on the blocking of the thin film layer 240, a film layer below the thin film layer 240 can be effectively protected against etching damage. In addition, it should be understood that the bottoms of the comb teeth in the formed movable comb tooth structure 231 are all fixed to the thin film layer 240, and thus, as the etching process continues, a torsion space of the movable comb tooth structure 231 is released, but because all the comb teeth are fixed to the thin film layer 240, the comb teeth cannot twist at random, thereby avoiding damage to the side walls of the comb teeth due to torsion of the comb teeth during etching. Particularly, to ensure that patterns of the comb teeth can be completely and accurately etched, a certain over etching amount can be generally increased, and the plasma etching process with higher precision can be adopted for etching. In this embodiment, the comb teeth can be stably fixed by the thin film layer 240, and thus, even under the large etching amount, damage to the side walls of the comb teeth from plasma can still be effectively relieved.
Further, before patterning the second conducting material layer 230, the forming method further includes: a plurality of electrodes 400 are formed on the second conducting material layer 230. At least part of the plurality of electrodes 400 are used for being electrically connected to the movable comb tooth structure 231. Specifically, the plurality of electrodes 400 include two first electrodes which are electrically isolated from each other, and the two first electrodes are respectively electrically connected to two sets of comb teeth in the movable comb tooth structure 231.
Further, the plurality of electrodes 400 further include a second electrode, and the second electrode is used for being electrically connected to the cantilever region B of the second conducting material layer 230.
In this embodiment, the plurality of electrodes 400 can be electrically isolated from each other by separation openings 510. Specifically, through the separation openings 510, the first electrodes and the second electrode in the plurality of electrodes cannot be mutually connected by the conducting material layers (including the first conducting material layer 130 and the second conducting material layer 230).
A forming method of the separation openings 510 may include: during patterning the second conducting material layer 230, second openings are further formed in the second conducting material layer 230, bottoms of the second openings are stopped at the thin film layer as well and located above the first openings 130c of the first conducting material layer 130, and thus, the first openings 130c and the second openings are in up-down mutual communication to form the separation openings 510, thereby utilizing the separation openings 510 for dividing the plurality of mutually separated electrodes.
It should be understood that based on layout limitations, the drawings only exemplarily illustrate two separation openings 510 and two electrodes 400, and it should be understood that the electrodes 400 for connecting different modules are electrically isolated by the separation openings 510. In addition, the first electrodes can be electrically connected to the movable comb tooth structure 231, and the second electrode can be electrically connected to the cantilever region B through other interconnection structures.
In step S400, referring to
As mentioned above, the thin film layer 240 is relatively thin, and thus, the thin film layer 240 can be depleted with a small etching amount. Specifically, the thin film layer 240 can be eroded by a gas phase corrosive agent. In this embodiment, the thin film layer 240 is removed by a vapor phase hydrogen fluoride (VHF) fumigation corrosion process. Compared with the wet etching process, the gas phase corrosive agent is utilized for eroding the thin film layer 240, which can effectively avoid the problems such as adhesion and torsion likely to occur between the adjacent comb teeth caused by corrosive liquid in the wet etching process.
In addition, in an optional solution, the material of the first insulating layer 120 may be the same as that of the thin film layer 240 (e.g., both including silicon oxide), and accordingly, when etching the thin film layer 240, a trace amount of the first insulating layer 120 will be consumed. However, as mentioned above, the etching amount of the thin film layer 240 is small, and thus, the first insulating layer 120 cannot be largely consumed, which is conducive to guaranteeing the stable supporting of the first insulating layer 120 to a film layer above the first insulating layer.
In a further solution, referring to
Continuing referring to
In a specific implementation solution, a material of one of the first bonding ring and the second bonding ring is aluminum, and a material of the other bonding ring is germanium, thereby realizing aluminum-germanium bonding between the first bonding ring and the second bonding ring. Alternatively, in another solution, the material of both the first bonding ring and the second bonding ring is gold, thereby realizing gold-gold bonding between the first bonding ring and the second bonding ring. Alternatively, the material of one of the first bonding ring and the second bonding ring is gold, and the material of the other bonding ring is silicon, thereby realizing gold-silicon bonding between the first bonding ring and the second bonding ring.
Based on the above forming method, this embodiment further provides an inertial sensor. Referring to
A first cavity 130a may also be formed in the first conducting material layer 130, and the movable comb tooth structure 231 is suspended above the first cavity 130a. Further, the second conducting material layer 230 is further provided with a cantilever region B, and a second cavity 130b and a stopper 131 are further formed in the first conducting material layer 130. The second cavity 130b and the stopper 131 are both located directly under the cantilever region B. In this embodiment, a top surface of the stopper 131 is lower than a bonding surface of the first conducting material layer 130.
In this embodiment, the first conducting material layer 130 and the second conducting material layer 230 are, for example, directly bonded based on a silicon-silicon bonding process, and the process is simple and has high bonding force.
Continuing referring to
Further, up-down communicating openings are further formed in both the first conducting material layer 130 and the second conducting material layer 230, so as to form separation openings 510, and the plurality of electrodes 400 are electrically isolated from each other by the separation openings 510, so as to be respectively and independently electrically connected to the corresponding movable comb tooth structure 231 and the corresponding cantilever region B, and the like.
It should be understood that the end portion of the movable comb tooth structure 231 is contracted inward through the trench in the second conducting material layer 230, and thus, the movable comb tooth structure 231 can be suspended. Compared with a conventional process in which a suspended movable comb tooth structure is realized through a spacer layer, this embodiment not only can guarantee that the movable comb tooth structure 231 is spaced from the second conducting material layer, but also can combine the thin film layer to further improve the quality of the formed comb tooth structure.
It should be noted that although the present invention has been disclosed by the preferred embodiments above, the above embodiments are not intended to limit the present invention. Any technical personnel familiar with the field can utilize the above disclosed technical contents for making many possible variations and modifications on the technical solutions of the present invention, or revise the technical solutions of the present invention into equivalently-changed equivalent embodiments without departing from the scope of the technical solutions of the present invention. Thus, any simple revise, equivalent variation and modification made on the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.
It should be further understood that unless particularly explained or indicated, descriptions of terms in the specification such as “first”, “second” and “third” are merely used for distinguishing various modules, elements, steps and the like in the specification, rather than representing a logical relationship or a sequence relationship, or the like among the modules, elements and steps.
In addition, it should be further understood that the terms described herein are only used for describing specific embodiments, rather than limiting the scope of the present invention. It needs to be noted that the singular form “a” and “an” used herein and in the attached claims includes a plural standard, unless the context clearly represents the contrary. For example, the quotation of “a step” or “an apparatus” means the quotation of one or more steps or apparatuses, and may include secondary steps and secondary apparatuses. All adopted conjunctions should be understood in the broadest sense. In addition, the word “or” should be understood to have the definition of the logic “or” instead of the definition of the logic “xor”, unless the context clearly represents the contrary. Moreover, implementation of the method and/or device in the embodiments of the present invention may include manual, automatic or combined execution of selected tasks.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202011413591.7 | Dec 2020 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/125443 | 10/21/2021 | WO |
