JP2011178145A - Method for manufacturing silicon device, and method for manufacturing liquid jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a silicon device capable of suppressing generation of a fragmentation or a crack of a silicon wafer during a manufacture process and generation of a foreign substance, and to provide a method for manufacturing a liquid jet head. <P>SOLUTION: The method includes: forming a pressure generating element on the first wafer 110; forming a recess 131 deep enough for the first substrate 10 to be accommodated on the second wafer 130; forming a joint body 200 by joining the first wafer 110 in the recess 131 of the second wafer 130; forming a protective film 150 composed of an etching resistant material on at least the outer circumference of the surface of the second wafer 130 to which the first wafer 110 is joined, and covering the surface of the second wafer 110 with the protective film 150; working the surface of the joint body 200 on the side of the first wafer 110 until the surfaces of the first wafer 110 and the second wafer 130 form the same plane; and then dividing the joint body 200 into a plurality of chips each having a predetermined size. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method of manufacturing a silicon device having elements on a silicon substrate, and in particular,
The present invention is suitable for application to a manufacturing method of a liquid ejecting head in which droplets are ejected from a nozzle by a pressure generating element.

As a structure of an ink jet recording head which is a typical example of a liquid ejecting head, for example, a flow path forming substrate formed of a silicon substrate in which a pressure generation chamber communicating with a nozzle is formed, and one surface of the flow path forming substrate And a sealing substrate (protective substrate) having a piezoelectric element holding portion that is bonded to the surface of the flow path forming substrate on the piezoelectric element side and seals the piezoelectric element (for example, , See Patent Document 1).

In addition, the ink jet recording head having such a structure is manufactured as follows, for example. First, a piezoelectric element is formed on one side of a silicon wafer on which a plurality of flow path forming substrates are integrally formed via a diaphragm. Then, a sealing substrate forming material to be a sealing substrate is bonded to the silicon wafer, and a pressure generating chamber or the like is formed by wet etching the silicon wafer with an alkaline solution in a state where the sealing substrate forming material is bonded. Thereafter, the ink jet recording head is manufactured by dividing the silicon wafer into a predetermined chip size.

Here, as described in Patent Document 1, a peripheral surface of a silicon wafer on which a plurality of flow path forming substrates are integrally formed is generally chamfered to prevent chipping or cracking. (
In many cases, a chamfered portion is formed.

Further, with the recent miniaturization of the head, a relatively thin silicon substrate has been used as the flow path forming substrate. As a method of manufacturing an ink jet recording head having a relatively thin channel forming substrate, for example, a protective substrate wafer is bonded to a channel forming substrate wafer (silicon wafer), and then the channel forming substrate is used. There is a method of forming a pressure generation chamber or the like by etching after processing a wafer for use in a predetermined thickness (see, for example, Patent Document 2).

JP 2003-266394 A JP 2004-82722 A

As described above, when trying to process a silicon wafer (wafer for flow path forming substrate) having a chamfered portion at the peripheral portion relatively thinly, the thickness of the silicon wafer at the peripheral portion becomes extremely thin. There is a problem that cracks and chips are likely to occur.

Such a problem exists not only in a manufacturing method of a liquid jet head such as an ink jet recording head but also in a manufacturing method of various silicon devices represented by the liquid jet head.

The present invention has been made in view of such circumstances, and a silicon device manufacturing method and a liquid jet head capable of suppressing the occurrence of chipping and cracking of a silicon wafer in the manufacturing process and suppressing the generation of foreign matter. It aims at providing the manufacturing method of.

The present invention for solving the above-described problems includes a first substrate on which a pressure generation chamber communicating with a nozzle for ejecting liquid is formed, and a pressure applied to the pressure generation chamber provided on one surface side of the first substrate. A method of manufacturing a liquid jet head, comprising: a pressure generating element to be generated; and a second substrate bonded to the one surface side of the first substrate, wherein a plurality of the first substrates are integrally formed. The first to be
The pressure generating element is formed on a first wafer that is thicker than the first substrate, and a second wafer having a larger diameter than the first wafer in which a plurality of the second substrates are integrally formed. Forming a recess having a depth sufficient to accommodate the first substrate, bonding the first wafer into the recess of the second wafer, and forming a bonded body, and the second wafer. The first of
Forming a protective film made of a material having etching resistance on at least the outer peripheral portion of the surface to which the wafer is bonded, covering the surface of the second wafer with the protective film, and the first of the bonded body Processing the wafer side surface until the surface of the first wafer and the surface of the second wafer are flush, and dividing the joined body into a plurality of chips of a predetermined size. It is in the manufacturing method of the liquid jet head characterized by providing.
In the method for manufacturing a liquid jet head according to the present invention, the outer peripheral portion of the first wafer is reliably protected by the second wafer and the protective film. Therefore, it is possible to effectively suppress the occurrence of chipping or cracking in the outer peripheral portion of the first wafer during the manufacturing process.

Here, in the step of forming the protective film, it is preferable that a gap between the concave portions is filled with the protective film. Thereby, the outer peripheral part of a 1st wafer can be protected still more favorably.

In the step of forming the protective film, it is preferable that the surface of the first wafer is covered together with the surface of the second wafer by the protective film. By covering a relatively wide area with the protective film, the outer peripheral portion of the first wafer can be more reliably protected.

The step of processing the joined body preferably includes at least a step of grinding the first wafer. As a result, the first wafer can be processed to a predetermined thickness relatively easily and satisfactorily.

It is preferable that the method further includes a step of forming a chamfered portion only on the outer peripheral portion on the other surface side of the first substrate. As a result, the rigidity of the outer peripheral portion of the first wafer is increased, and the occurrence of chipping or cracking can be more reliably suppressed.

Further, the present invention provides a silicon device having a first substrate made of a silicon substrate having an element formed on one side and a second substrate bonded to the element side surface of the first substrate. In the method, the element is formed on a first wafer that is thicker than the first substrate on which the plurality of first substrates are integrally formed, while the plurality of second substrates are integrally formed. Forming a recess having a depth that allows the first substrate to be accommodated in a second wafer having a diameter larger than that of the first wafer, and forming the first wafer in the recess of the second wafer. A step of bonding the wafers to form a bonded body, and forming a protective film made of a material having etching resistance on at least an outer peripheral portion of the surface of the second wafer to which the first wafer is bonded, Covering the surface of the second wafer with a protective film , The first wafer side surface of the bonded body, the first
Processing until the surface of the wafer and the surface of the second wafer are flush with each other;
Dividing the joined body into a plurality of chips of a predetermined size, and a method for producing a silicon device.
In the silicon device manufacturing method of the present invention, the outer periphery of the first wafer is reliably protected by the second wafer and the protective film. Therefore, it is possible to effectively suppress the occurrence of chipping or cracking in the outer peripheral portion of the first wafer during the manufacturing process.

As described above, in the present invention, the first wafer is bonded in the recess formed in the second wafer, and the outer peripheral portion thereof is protected by the protective film. Thereby, generation | occurrence | production of the chip | tip and crack in the outer peripheral part of a 1st wafer can be suppressed effectively, and it can also suppress that the adhesive agent for joining both wafers peels. Therefore, it is possible to suppress the occurrence of nozzle clogging or the like due to foreign matters generated in the manufacturing process, and to significantly improve the yield.

FIG. 2 is an exploded perspective view illustrating a schematic configuration of a recording head according to an embodiment. 2A and 2B are a plan view and a cross-sectional view of a recording head according to an embodiment. FIG. 5 is a cross-sectional view illustrating an outline of a recording head manufacturing method according to an embodiment. FIG. 5 is a cross-sectional view illustrating an outline of a recording head manufacturing method according to an embodiment. FIG. 5 is a cross-sectional view illustrating an outline of a recording head manufacturing method according to an embodiment. FIG. 10 is a cross-sectional view illustrating a modification of the method for manufacturing a recording head according to an embodiment.

Hereinafter, the present invention will be described in detail based on embodiments.
FIG. 1 is an exploded perspective view showing a schematic configuration of an ink jet recording head which is an example of a liquid jet head according to an embodiment of the present invention. FIG. 2 is a plan view of FIG. FIG.

As shown in the drawing, a flow path forming substrate 10 which is a first substrate made of a silicon substrate has an elastic film 50 made of silicon oxide (SiO ₂ ) formed on one surface thereof. Flow path forming substrate 1
In 0, a plurality of pressure generating chambers 12 partitioned by a partition wall 11 are arranged in the width direction. An ink supply path 13 and a communication path 14 that are partitioned by a partition wall 11 and communicate with each pressure generation chamber 12 are provided on one end side in the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10. Furthermore, a communication portion 15 that communicates with each communication path 14 is provided outside the communication path 14. The communication portion 15 communicates with a reservoir portion 32 of a protective substrate 30 that is a second substrate described later,
A reservoir 100 serving as an ink chamber (liquid chamber) common to the pressure generation chambers 12 is configured.

On the other surface side of the flow path forming substrate 10, a nozzle plate 20 in which a nozzle 21 communicating with each pressure generating chamber 12 is formed is interposed via an insulating film 51 used as a mask when the pressure generating chamber 12 is formed. Are joined. The nozzle plate 20 is made of, for example, glass ceramics, a silicon single crystal substrate, or stainless steel. The insulating film 51 may be removed and the nozzle plate 20 may be directly bonded to the flow path forming substrate 10.

As described above, the elastic film 50 is formed on one surface side of the flow path forming substrate 10, and the insulator film 55 made of a material different from the elastic film 50 is formed on the elastic film 50. . Further, a piezoelectric element 300 as a pressure generating element that generates pressure in the pressure generating chamber 12 is formed on the insulator film 55. In the present embodiment, the piezoelectric element 300 includes the insulator film 5.
5, a lower electrode film 60 that is a common electrode formed on 5, a piezoelectric layer 70 that is formed on the lower electrode film 60, and an upper electrode film 80 that is an individual electrode formed on the piezoelectric layer 70. It is configured.
In addition, each upper electrode film 80 of the piezoelectric element 300 is connected to a lead electrode 90,
Each upper electrode film 80 and a drive IC described later are connected through the lead electrode 90.

On the surface of the flow path forming substrate 10 on the side of the piezoelectric element 300, specifically, on the lower electrode film 60, the elastic film 50, and the lead electrode 90, there is a second having a piezoelectric element holding portion 31 for protecting the piezoelectric element 300. The protective substrate 30 that is the substrate is bonded by, for example, an adhesive 35. A reservoir portion 32 is provided on the protective substrate 30 together with the piezoelectric element holding portion 31. The reservoir section 32 communicates with the communication section 15 formed on the flow path forming substrate 10 as described above to configure the reservoir 100.

The material of the protective substrate 30 is not particularly limited, but it is preferable to use substantially the same material as the thermal expansion coefficient of the flow path forming substrate 10, for example, a glass material, a ceramic material, etc. In this embodiment, the flow path forming substrate is used. A silicon substrate which is the same material as 10 is used.

Further, the protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction, and the vicinity of the end portion of the lead electrode 90 drawn from each piezoelectric element 300 is exposed in the through hole 33. Has been. A driving IC 200 for driving the piezoelectric elements 300 arranged side by side is fixed on the protective substrate 30. The driving IC 200 and the lead electrode 90 are electrically connected by a connection wiring 210 made of a conductive wire such as a bonding wire extending in the through hole 33.

On the protective substrate 30, a compliance substrate 40 comprising a sealing film 41 and a fixing plate 42.
Are joined. Here, the sealing film 41 is made of a material having low rigidity and flexibility. One surface of the reservoir portion 32 is sealed with the sealing film 41. The fixing plate 42 is formed of a hard material such as metal. A region of the fixing plate 42 facing the reservoir 100 is an opening 43 that is completely removed in the thickness direction, and one surface of the reservoir 100 is sealed only with a flexible sealing film 41. ing.

In such an ink jet recording head of this embodiment, ink is taken in from an external ink supply means (not shown), filled with ink from the reservoir 100 to the nozzle 21, and then generates pressure according to a recording signal from the drive IC 200. By applying a voltage to each piezoelectric element 300 corresponding to the chamber 12 to bend and deform, the pressure in each pressure generating chamber 12 is increased and ink droplets are ejected from the nozzles 21.

Hereinafter, a method for manufacturing such an ink jet recording head will be described with reference to FIGS.

First, as shown in FIG. 3A, an elastic film 50 and an insulating film are formed on one side of a flow path forming substrate wafer (first wafer) 110 on which a plurality of flow path forming substrates 10 are integrally formed. Body membrane 55
Then, the piezoelectric element 300 and the lead electrode 90 are sequentially formed. In addition, the manufacturing method of each of these layers is
Since it is a well-known technique, detailed description is abbreviate | omitted.

Further, as shown in FIG. 3B, a flow path forming substrate wafer 110 of a protective substrate wafer (second wafer) 130 in which a plurality of protective substrates 30 having piezoelectric element holding portions 31 and the like are integrally formed. A recess 131 having a size capable of accommodating the flow path forming substrate wafer 110 is formed on the joint surface side. That is, the recess 131 is formed by removing the central portion of the protective substrate wafer 130 having a diameter larger than that of the flow path forming substrate wafer 110 while leaving the thickness of the protective substrate 30. The depth of the recess 131 is not particularly limited, but is preferably slightly deeper than the thickness of the flow path forming substrate 10 (in this embodiment, about several tens of μm). Recess 131
The formation method is not particularly limited, but may be formed by dry etching, for example.

For example, R-shaped chamfered portions 132 are provided in advance on the outer peripheral edge portions of both surfaces of such a protective substrate wafer 130. As a result, the occurrence of chipping or cracking in the outer peripheral portion of the protective substrate wafer 130 is suppressed. On the other hand, the chamfered portion 111 is also provided on the outer peripheral edge portion of the flow path forming substrate wafer 110, and the occurrence of chipping, cracking, and the like in the outer peripheral portion is suppressed similarly to the protective substrate wafer 130. However, in this embodiment, the chamfered portion 111 is provided only on the surface of the flow path forming substrate wafer 110 opposite to the piezoelectric element 300. The chamfered portions 111 may be provided on both surfaces of the flow path forming substrate wafer 110, but in the manufacturing method of the present invention, the chamfered portions are provided only on the surface opposite to the piezoelectric element 300 of the flow path forming substrate wafer 110. By providing 111, it can suppress more reliably that a chip | tip and a crack generate | occur | produce in the outer peripheral part of the wafer 110 for flow path formation substrates.

Next, as shown in FIG. 4A, the wafer-bonded body 200 is formed by bonding the flow path-forming substrate wafer 110 with the adhesive 35 in the recess 131 of the protective substrate wafer 130. Thus, the flow path forming substrate wafer 110 is placed in the recess 131 of the protective substrate wafer 130.
By bonding, the flow path forming substrate wafer 110 and the protective substrate wafer 130 can be positioned relatively easily with high accuracy. Further, since the movement of the flow path forming substrate wafer 110 is limited to the inside of the recess 131, the occurrence of positional displacement after bonding is small. Further, the outer peripheral portion of the bonding surface side of the flow path forming substrate wafer 110 and the protective substrate wafer 130 is, as a result,
It will be covered by the protective substrate wafer 130.

For this reason, in the subsequent head manufacturing process, the load is hardly applied to the outer peripheral portion of the flow path forming substrate wafer 110 on the bonding surface side with the protective substrate wafer 130, and the occurrence of chipping, cracking, etc. is effectively achieved. Can be suppressed. Since the outer peripheral edge of the surface of the flow path forming substrate wafer 110 on the protective substrate wafer 130 side is protected by the protective substrate wafer 130 as described above, the chamfered portion 111 and the protective substrate wafer 130 are connected to each other as described above. Is preferably provided only on the opposite surface. Since the chamfered portion 111 is not provided on the bonding surface between the flow path forming substrate wafer 110 and the protective substrate wafer, the flow path forming substrate wafer 11 is provided.
The rigidity at the outer periphery of 0 is increased, and the bonding strength between the flow path forming substrate wafer 110 and the protective substrate wafer 130 is also improved. Therefore, generation | occurrence | production of the chip | tip, a crack, etc. in the outer peripheral part of the wafer 110 for flow path formation board | substrates can be suppressed more reliably.

Next, as shown in FIG. 4B, at least the exposed portion 133 exposed at the outer peripheral portion is covered on the surface of the protective substrate wafer 130 on the bonding surface side with the flow path forming substrate wafer 110. A protective film 150 is formed. In the present embodiment, the exposed portion 13 of the protective substrate wafer 130.
The protective film 150 is formed on the entire surface of one side of the wafer bonded body 200 including the surface 3 and the surface of the flow path forming substrate wafer 110. In this embodiment, since the chamfered portion 111 is not formed on the bonding surface side of the flow path forming substrate wafer 110 and the protective substrate wafer 130, the protective film 150 is satisfactorily provided on the outer peripheral portion of the flow path forming substrate wafer 110. Can be adhered to.

At this time, it is preferable that the gap in the recess 131 of the protective substrate wafer 130 is filled with the protective film 150. As a result, the outer peripheral portion of the flow path forming substrate wafer 110 can be better protected. Further, since the adhesive 35 for bonding the wafers is also reliably covered with the protective film 150, it is possible to reliably prevent the adhesive 35 from being peeled off in the subsequent steps. The other surface of the wafer bonded body 200 (protective substrate wafer 130) is preferably protected by applying a protective tape 160, for example.

Here, the protective film 150 includes the flow path forming substrate wafer 110 and the protective substrate wafer 130.
It is preferable to form the film at a temperature lower than the heating temperature for curing the adhesive 35 for bonding the two. The protective film 150 is preferably made of a material having etching resistance. The material having etching resistance refers to a material that is not substantially etched by an etching solution used for etching the flow path forming substrate wafer 110 in a process described later. For example, in this embodiment, since the flow path forming substrate wafer 110 is etched using an alkaline solution such as KOH, examples of the material having etching resistance include an inorganic oxide made of SOG. The protective film 150 may be formed by, for example, silicon oxide (SiO ₂ ), silicon nitride (SiN), or the like by a low temperature sputtering method, a low temperature film formation CVD method, or the like.

Next, as shown in FIG. 4C, the flow path forming substrate wafer 110 is processed by processing the surface of the flow path forming substrate wafer 110 opposite to the surface to which the protective substrate wafer 130 is bonded. Set to a predetermined thickness. Specifically, for example, a back surface polishing apparatus (back grinder)
For example, the flow path forming substrate wafer 110 is ground to a certain thickness. Thereafter, for example, the flow path forming substrate wafer 110 is wet-etched using an etchant made of hydrofluoric acid or the like to have a predetermined thickness. In particular, it is preferable that the flow path forming substrate wafer 110 is ground until it reaches the protective substrate wafer 130 and then the flow path forming substrate wafer 110 is made to have a desired thickness by wet etching.

In the manufacturing method of the present invention, the flow path forming substrate wafer 110 is bonded to the recess 131 formed in the protective substrate wafer 130 as described above, and the outer peripheral portion of the flow path forming substrate wafer 110 is protected. It is protected by the membrane 150. Therefore, even if the flow path forming substrate wafer 110 is processed by grinding or the like in this way, the flow path forming substrate wafer 110 is processed.
It is possible to effectively suppress the occurrence of chipping and cracking. Further, peeling of the adhesive 35 can be prevented. Therefore, the occurrence of initial failure such as nozzle clogging due to foreign matter can be suppressed, and the yield can be improved.

Furthermore, in this embodiment, since the chamfered portion 111 is not provided on the surface of the flow path forming substrate wafer 110 on the protective substrate wafer 130 side, the flow path forming substrate 110 is processed even after the flow path forming substrate wafer 110 is processed. The outer peripheral portion of the wafer 110 for use is secured to have the same thickness as other portions. Therefore, it can suppress more reliably that a chip | tip and a crack generate | occur | produce in the outer peripheral part of the wafer 110 for flow-path formation board | substrates. As shown in FIG. 6, the wafer 11 for flow path forming substrate is used.
Even when the chamfered portion 111 is formed on the zero protective substrate wafer 130 side, the outer periphery of the flow path forming substrate wafer 110 is protected by the protective substrate wafer 130 (the outer wall of the recess 131). At the same time, it is also protected by the protective film 150. Therefore, according to the manufacturing method of the present invention, even in the case of such a configuration, of course, the wafer 1 for flow path forming substrate is used.
It can suppress that a crack, a crack, etc. generate | occur | produce in the outer peripheral part of 10. FIG.

After the thinning process of the flow path forming substrate wafer 110 is completed in this way, the flow path such as the pressure generating chamber 12 is formed by etching the flow path forming substrate wafer 110. Specifically, after the protective tape 160 affixed to the other surface of the wafer bonded body 200 is peeled off, as shown in FIG. 5A, on the surface of the flow path forming substrate wafer 110, for example, silicon nitride (SiN) ) Is newly formed and patterned into a predetermined shape through a resist or the like (not shown). Next, the flow path forming substrate wafer 110 is wet-etched using, for example, an alkaline solution such as an aqueous potassium hydroxide (KOH) solution using the insulating film 51 as a mask. Thereby, as shown in FIG. 5B, the flow path forming substrate wafer 11 is formed.
A pressure generation chamber 12, an ink supply path 13, a communication path 14, and a communication part 15 are formed at zero. In addition, since the adhesive 35 that joins the wafers is covered with the protective film 150 in this step, the adhesive 35 can be prevented from being peeled off and becoming a foreign substance.

Thereafter, as shown in FIG. 5 (c), an unnecessary portion of the outer peripheral edge of the wafer bonded body 200 is removed.
For example, it is removed by cutting by dicing or the like. At this time, the protective film 150 remaining around the flow path forming substrate wafer 110 is also removed at the same time. The nozzle 2 is formed on the surface of the flow path forming substrate wafer 110 opposite to the protective substrate wafer 130.
1 is bonded to the protective substrate wafer 130, and the flow path forming substrate wafer 110 is divided into one chip size as shown in FIG. Thus, an ink jet recording head having the above-described structure is manufactured.

Although one embodiment of the present invention has been described above, of course, the present invention is not limited to such an embodiment. For example, in the embodiment described above, the pressure generating chamber 12 and the like are formed by etching the flow path forming substrate wafer 110 by wet etching using an alkaline solution. May be formed. In this case, it is necessary to select a material for the protective film 150 as appropriate.

In the above-described embodiment, the ink jet recording head has been described as an example of the liquid ejecting head. However, the present invention is widely intended for the entire liquid ejecting head, and ejects liquid other than ink. Of course, it can also be applied to the head. As other liquid ejecting heads, for example, various recording heads used in an image recording apparatus such as a printer,
Color material ejecting heads used for manufacturing color filters such as liquid crystal displays, organic EL displays, electrode material ejecting heads used for forming electrodes such as FEDs (field emission displays), bio-organic matter ejecting heads used for biochip manufacturing, etc. Can be mentioned.

Furthermore, the present invention is not limited to a method for manufacturing a liquid jet head, and can be widely applied as long as it is a method for manufacturing a silicon device having a silicon substrate.

DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate, 12 Pressure generation chamber, 20 Nozzle plate, 30 Protection board | substrate, 35 Adhesive agent, 40 Compliance board | substrate, 50 Elastic film, 55 Insulator film, 60 Lower electrode film, 70 Piezoelectric layer, 80 Upper electrode film 90 lead electrodes,
100 reservoir, 110 wafer for flow path forming substrate, 111 chamfered portion, 13
0 wafer for protective substrate, 131 recess, 132 chamfered portion, 133 exposed portion,
150 protective film, 200 wafer bonded body, 300 piezoelectric element

Claims (6)

A first substrate in which a pressure generating chamber communicating with a nozzle for injecting liquid is formed; a pressure generating element provided on one side of the first substrate for generating pressure in the pressure generating chamber; A liquid jet head manufacturing method comprising: a second substrate bonded to the one surface side of one substrate;
The pressure generating element is formed on a first wafer that is thicker than the first substrate on which the plurality of first substrates are integrally formed, and the plurality of second substrates are integrally formed. Forming a recess having a depth in which the first substrate can be accommodated in a second wafer having a diameter larger than that of the first wafer,
Bonding the first wafer in the recess of the second wafer to form a bonded body;
Forming a protective film made of a material having etching resistance on at least an outer peripheral portion of a surface of the second wafer to which the first wafer is bonded, and covering the surface of the second wafer with the protective film; ,
Processing the surface of the bonded body on the first wafer side until the surface of the first wafer and the surface of the second wafer are flush with each other;
Dividing the joined body into a plurality of chips of a predetermined size, and a method of manufacturing a liquid ejecting head. 2. The method of manufacturing a liquid jet head according to claim 1, wherein, in the step of forming the protective film, a gap between the recesses is filled with the protective film. 3. The liquid jet head according to claim 1, wherein in the step of forming the protective film, the surface of the first wafer is covered together with the surface of the second wafer by the protective film. Manufacturing method. The method of manufacturing a liquid jet head according to claim 1, wherein the step of processing the joined body includes at least a step of grinding the first wafer. 5. The method of manufacturing a liquid jet head according to claim 1, further comprising a step of forming a chamfered portion only on an outer peripheral portion on the other surface side of the first substrate. A method for manufacturing a silicon device, comprising: a first substrate made of a silicon substrate having an element formed on one surface side; and a second substrate bonded to the element-side surface of the first substrate,
The element is formed on a first wafer that is thicker than the first substrate on which a plurality of the first substrates are integrally formed, while a plurality of the second substrates are integrally formed on the first wafer. Forming a recess having a depth in which the first substrate can be accommodated in a second wafer having a diameter larger than that of the first wafer;
Bonding the first wafer in the recess of the second wafer to form a bonded body;
Forming a protective film made of a material having etching resistance on at least an outer peripheral portion of a surface of the second wafer to which the first wafer is bonded, and covering the surface of the second wafer with the protective film; ,
Processing the surface of the bonded body on the first wafer side until the surface of the first wafer and the surface of the second wafer are flush with each other;
Dividing the joined body into a plurality of chips of a predetermined size, and a method for manufacturing a silicon device.

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