CN105692544A - Forming method of MEMS device - Google Patents
Forming method of MEMS device Download PDFInfo
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- CN105692544A CN105692544A CN201410714490.1A CN201410714490A CN105692544A CN 105692544 A CN105692544 A CN 105692544A CN 201410714490 A CN201410714490 A CN 201410714490A CN 105692544 A CN105692544 A CN 105692544A
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Abstract
A forming method of an MEMS device comprises the steps: firstly, ion implantation is performed on a partial region of a surface layer of a silicon substrate to form a modified region, then a device layer is formed on the silicon substrate having the modified region, and grooves for exposing the modified region are formed in the device layer; the modified region and a part of the silicon substrate are removed by means of wet-process corrosion through the grooves to form a cavity; the nature of the modified region is different from that of the silicon substrate, so when the silicon substrate is corroded to form the cavity through selecting a corrosion liquid, the material of the modified region below the device layer suspending at the upper part of the cavity can be completely removed; due to complete removal of the modified region, no silicon material remains below a suspending movable member, and thus the sensitivity of the movable member is improved.
Description
Technical field
The present invention relates to technical field of semiconductors, particularly relate to the forming method of a kind of MEMS。
Background technology
In prior art, for improving device degree of integration, reduce device volume, reducing device cost, MEMS is increasingly becoming the main flow of semiconductor device。MEMS, for instance humidity sensor, has the movable member being suspended in cavity in it, find in actual fabrication process, and the movable member of above-mentioned making has some defects, for instance movable member easily lost efficacy, or sensing sensitivity is relatively low。
For the problems referred to above, the present invention provides the forming method of a kind of new MEMS, to improve yield and the sensitivity of movable member。
Summary of the invention
The problem that this invention address that be how to improve movable member in MEMS yield and sensitivity。
For solving the problems referred to above, the present invention provides the forming method of a kind of MEMS, including:
Silicon base is provided, carries out ion implanting in the subregion on described silicon base top layer and form modified zone；
The described silicon base with modified zone is formed device layer；
Device layer described in dry etching is with groove formed therein that, and described groove exposes described modified zone；
Removing described modified zone and part silicon base to form cavity by described groove wet method, the device layer being suspended in described cavity top forms movable member。
Alternatively, described wet method removes described modified zone and part silicon base adopts same solution, and the removal of described modified zone is isotropic etch by described solution, and the corrosion to described silicon base is that anisotropy is removed。
Alternatively, the ion that described silicon base top layer is injected is silicon ion, and the material of the modified zone of formation is unformed silicon。
Alternatively, the material of described device layer is silicon dioxide。
Alternatively, described movable member is single armed beam or the movable thin film of two ends support。
Alternatively, described movable member is the sensing element of the sensing element of pressure resistance type humidity sensor or capacitance type humidity sensor。
Alternatively, form unformed Si modification district to include:
Described silicon base is formed patterned hard mask layer；
For mask, described silicon base is carried out Si ion implantation with described patterned hard mask layer。
Alternatively, the material of described hard mask layer is at least one in silicon nitride, silicon oxynitride。
Alternatively, the depth bounds in described unformed Si modification district is 50nm～100nm。
Alternatively, described silicon dioxide device layer includes the first silicon oxide layer from bottom to top and the second silicon oxide layer。
Alternatively, wet method removes described unformed Si modification district and part silicon base employing alkaline solution。
Alternatively, described alkaline solution is TMAH aqueous solution。
Alternatively, the cavity formed is that opening is big, and little trapezoidal in bottom, the angular range between sidewall and the diapire of described cavity is 50 degree～60 degree。
Alternatively, the number of the groove formed in described device layer is two or more。
Compared with prior art, technical scheme has the advantage that 1) ion implanting formation modified zone is first carried out in the subregion on silicon base top layer, device layer is formed afterwards in the silicon base have modified zone, the groove exposing modified zone is formed in device layer, this modified zone and part silicon base is removed to form cavity by this groove wet etching, different in kind due to character and the silicon base of modified zone, thus selective etching solution can be passed through, when corroding silicon base and forming cavity, the modified zone material being suspended under the device layer on cavity top can be removed completely, removal completely due to modified zone, make to remain without silicon material under the movable member suspended, and then improve the sensitivity of movable member。
2) in alternative, modified zone is by carrying out Si ion implantation formation to silicon base, the modified zone material formed is unformed silicon, the material with the device layer formed in the silicon base of modified zone is silicon dioxide, movable member for silicon dioxide material, same alkaline solution is adopted to remove unformed Si modification district and silicon base, this is because the corrosion of unformed silicon is isotropic etch by alkaline solution, it is anisotropic etch to the silicon in silicon base, and alkaline solution does not corrode silicon dioxide, thus alkaline solution can form cavity simultaneously in silicon base, the bottom silicon dioxide movable member without silicon residual can also be formed。
3) in alternative, 2) alkaline solution in alternative is TMAH aqueous solution, select owing to the corrosion of silicon is had crystal orientation by TMAH aqueous solution, on<100>crystal orientation, corrosion is very fast,<111>crystal orientation is corroded slower,<100>crystal orientation is namely in downward direction,<111>crystal orientation and cavity sidewalls direction, so, the cavity formed is that open top is big, bottom is little trapezoidal, relative to the arc groove that isotropic etch solution corrosion silicon base is formed, big trapezoidal of open top, at the supporting zone of movable member, the removal amount of silicon base is less, it is avoided that movable member caves in, thus improve the yield of movable member。
Accompanying drawing explanation
Fig. 1 to Fig. 5 is the structural representation of different phase in forming process of the MEMS in one embodiment of the invention；
When Fig. 6 is to exist without modified zone, the structural representation of the semiconductor structure that employing isotropic etching silicon base is formed；
When Fig. 7 is to exist without modified zone, the structural representation of the semiconductor structure that employing TMAH aqueous corrosion silicon base is formed。
Detailed description of the invention
As described in the background art, the movable member sensitivity of existing MEMS is low。For the problems referred to above, present inventor has performed analysis, it has been found that Producing reason is: when forming cavity to discharge movable member in silicon base, according to isotropic etching, owing to the formed cavity sidewalls of isotropic etching is shaped as arc, then can cause movable member silicon residue arranged below；If carrying out anisotropic etch, during for example with TMAH aqueous solution, owing on<100>crystal orientation, corrosion is very fast,<111>crystal orientation is corroded slower,<100>crystal orientation is namely in downward direction,<111>crystal orientation and cavity sidewalls direction, then when predetermined cavity depth can be caused to reach, cavity sidewalls removal amount is less, causes movable member silicon residue arranged below；Above-mentioned residue is due to different from movable member material, thus can affect the sensitivity of movable member。Based on above-mentioned analysis, the present invention proposes: first carries out ion implanting in the subregion on silicon base top layer and forms modified zone, device layer is formed afterwards in the silicon base have modified zone, the groove exposing modified zone is formed in device layer, this modified zone and part silicon base is removed to form cavity by this groove wet etching, different in kind due to character and the silicon base of modified zone, thus selective etching solution can be passed through, when corroding silicon base and forming cavity, the modified zone material being suspended under the device layer on cavity top can be removed completely, removal completely due to modified zone, make to remain without silicon material under the movable member suspended, and then improve the sensitivity of movable member。
Understandable for enabling the above-mentioned purpose of the present invention, feature and advantage to become apparent from, below in conjunction with accompanying drawing, specific embodiments of the invention are described in detail。
Fig. 1 to Fig. 5 is MEMS structural representation of different phase in forming process that one embodiment of the invention provides。Below in conjunction with shown in Fig. 1 to Fig. 5, the forming method of the MEMS being discussed in detail。
First, with reference to shown in Fig. 1, it is provided that silicon base 10, carry out Si ion implantation in the subregion on silicon base 10 top layer and form modified zone 12。
Above-mentioned silicon base 10 can be bulk silicon substrate (Silicon Wafer), it is also possible to for silicon-on-insulator (SOI)。The silicon source of Si ion implantation is such as SiH4, in other embodiments, it would however also be possible to employ other silicon plasma source existing。
In concrete ion implantation process, it is possible to first form patterned hard mask layer 11 in silicon base 10, this patterned hard mask layer 11 has opening, and the size and location correspondence of this opening makes a reservation for be formed area size and the position of modified zone 12。
Then, for mask, silicon base 10 is carried out Si ion implantation with described patterned hard mask layer 11, after ion implanting, remove above-mentioned patterned hard mask layer 11。
The material of hard mask layer 11 is such as at least one in silicon nitride, silicon oxynitride, and the hot phosphoric acid of corresponding employing is removed。
After silicon base 10 carries out Si ion implantation, the material of the modified zone 12 of formation is unformed silicon, in some aspects, and the character of above-mentioned unformed silicon and the different in kind of silicon。
In one embodiment, the depth bounds in above-mentioned unformed Si modification district 12 is 50nm～100nm。
Then, with reference to, shown in Fig. 2, the silicon base 10 have modified zone 12 forming device layer 13。
Device layer 13 is for forming the movable member of MEMS。In specific implementation process, the material of device layer 13 carries out specifically chosen according to the sensing type of MEMS。In the present embodiment, MEMS is pressure resistance type humidity sensor or capacitance type humidity sensor, and device layer 13 is for forming the sensing element of humidity sensor, and the material of device layer 13 is silicon dioxide。For pressure resistance type humidity sensor, after silicon dioxide water suction, it may occur that deformation, thus silicon material (being subsequently formed) on which applies compressive stress or tension, cause this silicon material resistance variations, by detecting resistance change, water absorption namely the size of humidity can be reflected。For capacitance type humidity sensor, after silicon dioxide water suction, dielectric constant can change, and by detecting the electric capacity of the change in dielectric constant amount reflecting this silicon dioxide, can obtain water absorption namely the size of humidity。
In specific implementation process, as in figure 2 it is shown, for increasing deformation quantity or change in dielectric constant amount, above-mentioned silicon dioxide device layer 13 includes the first silicon oxide layer 131 and the second silicon oxide layer 132 from bottom to top。In other embodiments, the number of plies of device layer 13 can also be other number。
Afterwards, with reference to shown in Fig. 3, with groove 14 formed therein that, described groove 14 exposes described modified zone 12 to device layer 13 (with reference to shown in Fig. 2) described in dry etching。
Fig. 4 is the sectional view of A-A straight line along Fig. 3。With reference to shown in Fig. 3 and Fig. 4, in the present embodiment, the groove 14 of formation is two。Device layer 13 between two grooves 14 is subsequently used for forming movable member。It can be seen that the sensitive thin film that this device layer 13 supports for two ends。In other embodiments, it is also possible to increase another groove (not shown) of vertical two grooves 14, to form the movable member that only one end supports, i.e. single armed beam。
The etching of groove 14 can adopt existing photoetching, dry etching to be formed, namely on device layer 13, form photoresist, form the photoresist of patterning after adopting the mask plate exposure imaging of patterning, carry out dry etching to form groove 14 with the photoresist of this patterning for mask。
In other embodiments, it is also possible to the type according to sensor, only form a groove 14。
Then, with reference to, shown in Fig. 5, removing described modified zone 12 and part silicon base 10 to form cavity 15 by groove 14 wet method, the device layer 13 being suspended in described cavity 15 top forms movable member。
Device layer 13 between two grooves 14, by forming cavity 15, has been discharged so that it is become movable member by this step。In said process, owing to modified zone 12 is different from the material of silicon base 10, thus can pass through to select wet method to remove solution so that it is modified zone 12 is removed completely。Owing to modified zone 12 is completely removed, thus remain without silicon under the movable member discharged (device layer 13)。
In specific implementation process, removing completely and the removal of part silicon base 10 can be adopted same solution modified zone 12。In specific implementation process, owing to modified zone 12 is relatively thin, if thus the removal of described modified zone 12 is isotropic etch by the solution selected, be that anisotropy is removed to the corrosion of described silicon base 10, then can remove this modified zone 12 completely when corroding silicon base 10。In the present embodiment, it is alkaline solution that this same wet method removes solution, for instance KOH solution, NaOH solution, or TMAH aqueous solution。For TMAH aqueous solution in the present embodiment。Unformed silicon is that isotropism is removed by TMAH aqueous solution, is that anisotropy is removed to silicon。Specifically, for silicon, TMAH aqueous solution has preferably crystal orientation and selects, and on<100>crystal orientation, corrosion is very fast, corrodes relatively slow on<111>crystal orientation, and the former is about 35 times of the latter,<100>crystal orientation namely in downward direction,<111>crystal orientation and cavity 15 sidewall direction。Thus, the cavity that formed 15 is big in opening, little trapezoidal in bottom。In one embodiment, the TMAH aqueous solution adopting quality concentration of volume percent to be 2%～20%, it is 20 DEG C～60 DEG C in temperature and corrodes。
In one embodiment, due to separating of unformed Si modification district 12, thus, the degree of depth of cavity 15 is 5 microns～10 microns, namely the distance on cavity 15 diapire surface from silicon base 10 is 5 microns～10 microns, and the angular range between sidewall and the diapire of cavity 15 is 50 degree～60 degree。
When Fig. 6 is to exist without modified zone, the structural representation of the semiconductor structure that employing isotropic etching silicon base 10 is formed。With reference to shown in Fig. 6, it can be seen that owing to isotropic etching formed cavity 15 sidewall shape is arc, movable member silicon residue arranged below can be caused first, second at the supporting zone of movable member, the removal amount of silicon base 10 is bigger, it is possible to cause movable member to cave in。Above-mentioned isotropic etching gas is such as XeF2, it is also possible to the inwall causing cavity 15 is crude, and silicon removal amount is unequal。And with reference to shown in Fig. 5, due to the fact that and be provided with modified zone 12, and adopt TMAH aqueous solution that silicon base 10 is corroded, not only solve the problem below movable member with silicon residue, result is stably suitable to batch processing, and at the triangle for acute angle that the removal of silicon base 10 is formed by the supporting zone of movable member, thus the removal amount of silicon is less, it is avoided that movable member caves in。Additionally, the crystal orientation of TMAH aqueous solution selects preferably, the inner wall smooth of the cavity 15 formed。
When Fig. 7 is to exist without modified zone, the structural representation of the semiconductor structure that employing TMAH aqueous corrosion silicon base 10 is formed。With reference to shown in Fig. 7, due to TMAH aqueous solution, on<100>crystal orientation, corrosion rate is much larger than the corrosion rate on<111>crystal orientation, thus when the degree of depth of the cavity 15 formed meets demand, the device layer between two grooves 14 there may also be silicon residual for 13 times。And with reference to, shown in Fig. 5, due to the fact that and be provided with modified zone 12, due to separating of modified zone 12, TMAH aqueous corrosion silicon base 10 is formed in cavity 15 process, and modified zone 12 is completely removed, it is also possible to avoid the silicon residue problem under movable member。
It is understandable that, the present embodiment illustrates for unformed silicon as the material of modified zone 12, in other embodiments, the modified zone 12 of other material can also be formed by the subregion of silicon base 10 being carried out other type of ion implanting, as long as this modified zone 12 is removed completely, the problem avoiding there is under movable member silicon residual just can be played。
Although present disclosure is as above, but the present invention is not limited to this。Any those skilled in the art, without departing from the spirit and scope of the present invention, all can make various changes or modifications, and therefore protection scope of the present invention should be as the criterion with claim limited range。
Claims (14)
1. the forming method of a MEMS, it is characterised in that including:
Silicon base is provided, carries out ion implanting in the subregion on described silicon base top layer and form modified zone；
The described silicon base with modified zone is formed device layer；
Device layer described in dry etching is with groove formed therein that, and described groove exposes described modified zone；
Removing described modified zone and part silicon base to form cavity by described groove wet method, the device layer being suspended in described cavity top forms movable member。
2. forming method according to claim 1, it is characterized in that, described wet method removes described modified zone and part silicon base adopts same solution, and the removal of described modified zone is isotropic etch by described solution, and the corrosion to described silicon base is that anisotropy is removed。
3. forming method according to claim 2, it is characterised in that the ion that described silicon base top layer is injected is silicon ion, and the material of the modified zone of formation is unformed silicon。
4. the forming method according to claim 1 or 2 or 3, it is characterised in that the material of described device layer is silicon dioxide。
5. forming method according to claim 1, it is characterised in that described movable member is single armed beam or the movable thin film of two ends support。
6. forming method according to claim 4, it is characterised in that described movable member is the sensing element of the sensing element of pressure resistance type humidity sensor or capacitance type humidity sensor。
7. forming method according to claim 3, it is characterised in that form unformed Si modification district and include:
Described silicon base is formed patterned hard mask layer；
For mask, described silicon base is carried out Si ion implantation with described patterned hard mask layer。
8. forming method according to claim 7, it is characterised in that the material of described hard mask layer is at least one in silicon nitride, silicon oxynitride。
9. forming method according to claim 3, it is characterised in that the depth bounds in described unformed Si modification district is 50nm～100nm。
10. forming method according to claim 4, it is characterised in that described silicon dioxide device layer includes the first silicon oxide layer from bottom to top and the second silicon oxide layer。
11. forming method according to claim 4, it is characterised in that wet method removes described unformed Si modification district and part silicon base adopts alkaline solution。
12. forming method according to claim 11, it is characterised in that described alkaline solution is TMAH aqueous solution。
13. forming method according to claim 11, it is characterised in that the cavity formed is that opening is big, little trapezoidal in bottom, the angular range between sidewall and the diapire of described cavity is 50 degree～60 degree。
14. forming method according to claim 1, it is characterised in that the number of the groove formed in described device layer is two or more。
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Cited By (1)
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| CN107265394A (en) * | 2017-07-10 | 2017-10-20 | 中国计量大学 | A kind of front release tech of free standing structure |
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| CN107265394B (en) * | 2017-07-10 | 2020-12-04 | 中国计量大学 | Front release technology of suspended microstructure |
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| CN105692544B (en) | 2017-08-29 |
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