JP2002011873A - Liquid drop discharge head and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a diaphragm thickness from varying. SOLUTION: The diaphragm 10 is constituted of a boron diffusion layer, and a supersaturation region S is formed to part of the boron diffusion layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a droplet discharge head and a method of manufacturing the same.

[0002]

2. Description of the Related Art An ink jet head used in an image recording apparatus such as a printer, a facsimile, a copying apparatus, a plotter or the like which is used as an image forming apparatus includes a nozzle for discharging ink droplets and a liquid chamber communicating with the nozzle. (Pressurized liquid chamber, pressure chamber, discharge chamber,
Also referred to as an ink flow path. ) And pressure generating means for generating a pressure for pressurizing the ink in the liquid chamber, and the ink droplets are ejected from the nozzles by pressurizing the ink in the liquid chamber with the pressure generated by the pressure generating means.

A conventional ink jet head is of a piezo type which discharges ink droplets by deforming and displacing a diaphragm forming a wall surface of a liquid chamber by using a piezoelectric element, and a heating resistor disposed in the liquid chamber. Bubble type that generates bubbles by ink film boiling using a body and ejects ink droplets, and vibrates with electrostatic force using a vibrating plate (or an electrode integrated therewith) that forms the wall surface of the liquid chamber and electrodes There is an electrostatic type in which ink droplets are ejected by deforming and displacing a plate.

[0004]

However, as in the case of the piezo type or electrostatic type ink jet head described above, a vibration forming a part of the wall of the liquid chamber for controlling the pressure and / or the volume change of the liquid chamber. When a plate is used, a diaphragm (boron diaphragm) formed by stopping etching of a silicon substrate in which high-concentration boron is diffused with an alkaline solution is generally used.

As described above, when a high-concentration P-type impurity diffusion layer of high-concentration boron or the like is formed on a silicon substrate and an etching stop is performed on the impurity diffusion layer to form a diaphragm using the impurity diffusion layer, If the variation occurs, the droplet ejection characteristics such as the droplet ejection volume and the droplet ejection speed vary, and the recording quality deteriorates. Therefore, highly precise thickness control is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a droplet discharge head having a small variation in the thickness of the diaphragm, and a droplet capable of controlling the thickness of the diaphragm with high accuracy. An object of the present invention is to provide a method for manufacturing a discharge head.

[0007]

According to a first aspect of the present invention, there is provided a droplet discharge head having a structure in which a diaphragm is formed of a boron diffusion layer and a part of the boron diffusion layer includes a supersaturated region. It was done. The droplet discharge head according to claim 2 is
The configuration is such that a boron diffusion layer is formed only in a part of the diaphragm, specifically, only in a part that becomes a stop layer by alkali etching.

According to a third aspect of the present invention, there is provided a droplet discharge head, wherein the vibration plate is formed of a boron diffusion layer into which nitrogen is introduced. According to a fourth aspect of the present invention, there is provided a droplet discharge head having a configuration in which only a part of the vibration plate, specifically, only a part serving as a stop layer by alkali etching is formed of a boron diffusion layer into which nitrogen is introduced. .

According to a fifth aspect of the present invention, there is provided a method of manufacturing a droplet discharge head.
The structure is such that a boron diffusion layer that forms all or a part of the diaphragm is formed by ion implantation and heat treatment. According to a sixth aspect of the invention, there is provided a method of manufacturing a droplet discharge head, wherein a boron diffusion layer forming all or a part of a diaphragm is formed by an ion implantation method and a solid diffusion method. According to a seventh aspect of the invention, there is provided a method of manufacturing a droplet discharge head, wherein a boron diffusion layer forming all or a part of a diaphragm is formed by an ion implantation method and a coating diffusion method.

[0010] The method for manufacturing a droplet discharge head according to claim 8 is characterized in that:
The structure is such that a boron diffusion layer forming all or a part of the diaphragm is formed by an ion implantation method and an RTA method.
According to a ninth aspect of the present invention, there is provided a method of manufacturing a droplet discharge head, wherein a boron diffusion layer for forming all or a part of a vibration plate is formed on a silicon substrate into which nitrogen has been introduced by an ion implantation method and an RTA method. According to a tenth aspect of the present invention, there is provided a method of manufacturing a droplet discharge head, wherein a boron diffusion layer forming a part of a diaphragm is formed by a high energy ion implantation method of several hundred keV to several MeV.

According to a eleventh aspect of the present invention, in the method of manufacturing a droplet discharge head, a boron diffusion layer forming all or a part of a vibration plate is formed on a silicon substrate, and a boron diffusion source is removed. The structure is such that boron ions are implanted and then heat treatment is performed. According to a method of manufacturing a droplet discharge head according to claim 12, a boron diffusion layer forming all or a part of a vibration plate is formed on a silicon substrate, and after removing a boron diffusion source, nitrogen ions are applied to the surface on the diffusion surface side. Injection is performed and then heat treatment is performed.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an exploded perspective view of an electrostatic inkjet head to which the present invention is applied, FIG. 2 is a top view illustrating the head in a transparent state, and FIG. 3 is a schematic cross-sectional view of the same head along a liquid chamber long side direction. FIG. 4 is a schematic cross-sectional explanatory view along the liquid chamber short side direction of the head.

This ink jet head includes a flow path substrate 1 as a first substrate, an electrode substrate 3 as a second substrate provided below the flow path substrate 1, and a third substrate provided above the flow path substrate 1. A plurality of nozzles 5, a liquid chamber 6 serving as an ink flow path communicating with each nozzle 5, and a common ink chamber 8 communicating with the liquid chamber 6 via a fluid resistance portion 7. And so on.

On the flow path substrate 1, a liquid chamber 6, a vibration plate 10 forming a wall surface serving as a bottom of the liquid chamber 6, a recess forming a partition 11 separating each liquid chamber 6, and a common ink chamber 8 are formed. A recess or the like is formed. The flow path substrate 1 diffuses boron (B), which is a high-concentration P-type impurity, into a silicon substrate to a thickness (depth) serving as a diaphragm, and forms the boron diffusion layer with KOH.
The diaphragm 10 (boron diaphragm) having a desired thickness when forming a concave portion or the like that becomes the liquid chamber 6 is obtained by forming the film by etching and stopping with an alkaline liquid such as.

A recess 14 is formed in the electrode substrate 3, and an electrode 15 facing the diaphragm 10 is formed on the bottom surface of the recess 14 with a predetermined gap 16 therebetween. A microactuator that changes the internal volume of the liquid chamber 6 by displacing the diaphragm 10 is configured.

The diaphragm 1 is provided on the electrode 15 of the electrode substrate 3.
In order to prevent the electrode 15 from being damaged by contact with the insulating layer 17, for example, an insulating layer 17 made of SiO _{2 having a} thickness
Is preferably formed. The electrode 15 extends to near the end of the electrode substrate 3 to form an electrode pad portion 15a for connecting to an external drive circuit via a connection means.

The electrode substrate 3 has a concave portion 14 formed on a glass substrate or a Si substrate having a thermal oxide film 3a formed on the surface thereof by etching with an HF aqueous solution or the like.
4, an electrode material having high heat resistance, such as titanium nitride, is formed to a desired thickness by a film forming technique such as sputtering, CVD, or vapor deposition, and then a photoresist is formed and etched to form recesses 14. Only the electrode 15 is formed. The electrode substrate 3 and the flow path substrate 1 are joined by processes such as anodic joining and direct joining.

The nozzle plate 4 is made of stainless steel (SU).
S) and the like are used to form an ink supply port 19 for supplying ink from the outside to the nozzle 5, the liquid resistance section 7, and the common ink liquid chamber.

In the ink-jet head thus configured, the diaphragm 10 is used as a common electrode, the electrode 15 is used as an individual electrode, and a driving voltage is applied between the diaphragm 10 and the electrode 15 so that the diaphragm 10 The vibrating plate 10 is deformed and displaced toward the electrode 15 by an electrostatic force generated between the vibrating plate 10 and the electrode 15, and the electric charge between the vibrating plate 10 and the electrode 15 is discharged from this state, whereby the vibrating plate 10 is returned and deformed.
When the internal volume (volume) / pressure of the liquid chamber 6 changes, ink droplets are ejected from the nozzles 5.

That is, when a pulse voltage is applied to the electrode 15 serving as an individual electrode, a potential difference occurs between the electrode 10 and the diaphragm 10 serving as a common electrode, and an electrostatic force is generated between the individual electrode 15 and the diaphragm 10. As a result, the diaphragm 10 is displaced according to the magnitude of the applied voltage. After that, the applied pulse voltage falls, whereby the displacement of the diaphragm 10 is restored, and the restoring force increases the pressure in the liquid chamber 6 and the ink droplets are ejected from the nozzles 5.

Next, a manufacturing process of the ink jet head will be described with reference to FIG. First, FIG.
As shown in the figure, the crystal plane orientation (110)
The high-concentration boron is diffused into the silicon substrate 21 to form a high-concentration boron diffusion layer 22.

On the other hand, as shown in FIG. 1B, a silicon substrate is used as the electrode substrate 3, and a base oxide film 3a for minimizing the capacitive coupling between the electrodes is formed. A recess 14 is formed, and an electrode 15 and an insulating film 17 covering the electrode 15 are formed on the bottom surface of the recess 14.

Then, as shown in FIG. 1C, the silicon substrate 21 serving as the flow path substrate 1 and the electrode substrate 3 are joined by a process such as direct joining (Si-Direct-Bonding). As shown in ()), an etching mask layer (not shown) is formed, and the silicon substrate 21 is alkali-etched to form the recess 23 serving as the liquid chamber 6 using the boron diffusion layer 22 as an etching stop. The diaphragm 10 made of 22 is formed.

Finally, as shown in FIG.
The nozzle plate 4 on which is formed is adhered and bonded to the flow path substrate 1 as shown in FIG.

Therefore, a method of forming a diaphragm using a high-concentration boron diffusion layer as an etching stop will be described.
In general, it is known that in a silicon substrate, a portion having a high-concentration boron layer has a lower alkali etching rate than a portion having no high-concentration boron layer. here,
Assuming that the etching rate of the portion of the silicon substrate where the high-concentration boron layer is not present is Ra and the etching rate of the portion where the high-concentration boron layer is present is Rb, the etching rate selection ratio P is P
= Ra / Rb, the selection ratio P increases as the concentration of the high concentration B layer increases. However, at a certain concentration or higher, a saturation tendency is observed.

The etching rate Ra and the etching rate Rb not only depend on the concentration of boron or other impurities contained in the silicon substrate, but also on the type of alkali solution, the mixing ratio of the alkali solution and the additive, It greatly varies depending on the concentration of the liquid, the temperature of the alkaline liquid, and also the crystal orientation of the silicon substrate. Crystal orientation plane (11
In the case of the silicon substrate of (0), two (111) planes having an extremely lower etching rate as compared with the other crystal orientation planes are present vertically, and the vertical plane can be processed. As described above, the diaphragm 10 is formed by performing alkali etching using a silicon substrate having a crystal plane orientation (110). In this case, as the alkaline solution, a KOH solution of about 10 to 40 wt% or this KOH solution
The processing temperature was set to 70 to 95 ° C. by using a liquid obtained by adding certain additives.

Further, by forming a low-pressure CVD nitride film as an etching mask layer on the silicon substrate and patterning it using a semiconductor photolithography technique, the processing accuracy of the surface width or the surface length is made 1 μm or less. . Furthermore, by controlling the depth, specifically, controlling the diaphragm thickness,
The variation in the thickness of the diaphragm can be set to an accuracy of 0.1 μm or less.

Here, in order to reduce the variation in the thickness of the diaphragm, a technique such as control of boron diffusion profile, stop control of alkali etching (etching selectivity), or control of surface properties of alkali etching is used. be able to.

That is, in controlling the boron diffusion profile, the depth of the diffusion layer, specifically, the depth of the boron stop concentration, not only affects the accuracy of the center value of the thickness of the diaphragm, but also the boron stop concentration. The sharpness of the profile (density gradient) in the vicinity also affects the variation in the diaphragm thickness.

In the stop control of the alkali etching, the etching selectivity directly affects the variation in the thickness of the diaphragm. This boron stop concentration is 3E18-3
It is a value appropriately determined depending on desired accuracy and etching time within a range of about E20 / cm ³ , but is 1E in view of cost, easiness of process, and resistance value of the diaphragm.
It is preferable to set in the range of about 19 to 2E20 / cm ³ .

Further, in the surface property control of the alkali etching, the surface property (irregularities on the surface) also directly affects the variation in the thickness of the diaphragm. It is possible to set a condition that is less affected than the thickness variation. Note that the etching rate, surface properties, and the like can be adjusted by the effects of the KOH concentration, temperature, and additives.

In the present invention, variations in the thickness of the diaphragm are reduced by controlling the boron diffusion profile, and the details thereof will be described below. The most common method of performing high concentration diffusion is the solid state diffusion method. When boron diffusion is performed by this solid diffusion method, B ₂
An O ₃ plate is used as a diffusion source. When a commercially available diffusion source is used, the dispersion accuracy of the sheet resistance value is often guaranteed at ± 3%, but when a diaphragm is formed with a boron diffusion layer, the boron diffusion profile is used instead of the sheet resistance value.
Since the shape of the (depth profile) itself is important, when the diffusion length is as long as several μm, the accuracy of the variation of the diaphragm thickness does not always match the guaranteed value of the sheet resistance.

For example, when boron solid diffusion is performed on a silicon crystal, it is considered that most of the diffused boron is activated (boron atoms are contained in the silicon crystal lattice). If activated, the sheet resistance depends only on the dose of boron (the amount introduced per unit area) and does not depend on the boron diffusion profile. Therefore, in this case, the sheet resistance value serves as a reference value as a monitor, but is insufficient for detailed management.

In the solid-state diffusion method, one of the factors that causes a variation in the boron diffusion profile is diffusion furnace stability. Specifically, the accuracy of the temperature monitor, the ramp rate (temperature rise / fall rate), the temperature distribution, and the stability such as the distance between the diffusion source and the silicon substrate. The stability is determined by conditions of the performance of the apparatus and its uniformity.

Another factor that causes variations in the boron diffusion profile is the state of the surface of the silicon substrate. An oxide film or the like is formed on the surface of the silicon substrate. This oxide film thickness varies depending on surface treatment such as cleaning, the standing time after the surface treatment, and the state of air entrapment when the temperature of the diffusion furnace is raised. Due to the variation of the thin oxide film thickness formed on the surface of the silicon substrate, the boron diffusion concentration (impurity diffusion concentration) on the substrate surface varies. When only the diffusion resistance is a problem, there is a case where the problem is not so serious. However, when forming a diaphragm, caution is required.

Therefore, a first embodiment of the present invention will be described with reference to FIG. FIG. 3 is an explanatory diagram illustrating an example of a boron diffusion profile (B depth profile) of the diaphragm according to the embodiment. In the first embodiment, a super-saturated region S is formed in a part of the boron diffusion layer region by forming a boron diffusion layer in a silicon substrate by ion implantation and heat treatment as shown in FIG.

For example, boron (B) is implanted at an energy of 1
A silicon wafer (silicon substrate) ion-implanted at 00 keV and at a dose of 3E16 / cm ² at 1050 ° C.-1
When heat treatment is performed for 00 min, a supersaturated region S (or U) is formed on a part of the substrate surface side as shown by the profile α. Further, boron (B) is implanted at an energy of 100 k.
eV, a silicon wafer (silicon substrate) ion-implanted at a dose of 3E16 / cm ² at 1050 ° C.-500 m
When the heat treatment is performed in, a supersaturated region S (or U ′) is formed in a part of the substrate surface side as shown by the profile β.

As described above, since the supersaturated region S exists in a part of the boron diffusion layer, the controllability of the B diffusion profile becomes extremely high. That is, when the boron diffusion layer does not have the supersaturated region S, as shown in FIG. 7, when the position of the B-stop concentration is set to the line T, the profile when the surface concentration is the concentration a is the same profile. In α and the profile α ′ at the density a ′, the B stop point (intersection of the profile and the line T) is different as shown by points Tα and Tα ′, and the diffusion depth is also different from Hα and Hα ′. This variation in the diffusion depth becomes the variation in the thickness of the diaphragm as it is. The variation in the diaphragm thickness due to the variation in the B stop point increases as the diffusion depth (diffusion length) increases, as shown by profiles β and β ′ having a diffusion length longer than the profile α.

On the other hand, when the boron diffusion layer has a supersaturated region S in advance, as shown in FIG. 8, B diffusion is performed starting from point L in FIG. The diffusion depth Hα is obtained using the point Tα as the boron stop point, and the diffusion depth Hβ is obtained using the point Tβ as the B stop point when the profile β has a longer diffusion length than the profile α.

That is, when the supersaturated region S exists in the silicon crystal in advance, since the starting point of boron diffusion is fixed, the controllability of the boron diffusion profile becomes extremely high. This point L is, as shown in FIG. It is the same whether the maximum concentration of the supersaturated region S is at the point U or at the point U ′, and it has been confirmed that the point L depends only on the silicon substrate temperature. On the other hand, when the supersaturated region S disappears, the profile collapses (the starting point L of the diffusion profile shifts from a 'to a') as shown in FIG. ) Is necessary to maintain the supersaturated region S until the saturation concentration L (atom
s / cm ³ ) and a desired boron stop depth H (cm), it is necessary to introduce a dose of at least about L * H (atoms / cm ² ).

Since the supersaturated region (supersaturated state) is maintained in a part of the boron diffusion layer, the boron diffusion profile can be controlled starting from the supersaturation point, and the dispersion of boron diffusion is reduced. In addition, precise control of the boron diffusion layer becomes possible. Thereby, the thickness of the diaphragm can be formed with high precision, the variation of the driving voltage is reduced, and the droplet discharge characteristics such as the droplet volume Mj and the discharge speed Vj are stabilized. Furthermore, when this boron diffusion layer is formed by ion implantation and heat treatment, the depth of the supersaturated region can be accurately controlled by controlling the ion energy, and particularly, a thin diaphragm is formed with high precision. can do.

Next, another example of the first embodiment will be described with reference to FIG. In the same figure, as shown in FIG. 6, the profile α is obtained by changing a silicon wafer (silicon substrate) obtained by ion-implanting boron (B) with an implantation energy of 100 keV and a dose of 3E16 / cm ² to 105
It is a B diffusion profile at the time of performing heat processing at 0 degreeC-100min. The profile γ is such that boron (B) is implanted at an energy of 100 keV and a dose of 1.5E16 /
7 is a B diffusion profile when a silicon wafer (silicon substrate) ion-implanted at cm ² is heat-treated at 1050 ° C. for 100 minutes.

As can be seen from this example, the supersaturation point L matches the profile α and the profile γ,
In addition, the diffusion depths Hα and Hγ almost completely match. That is, when boron diffusion is performed by ion implantation and heat treatment, substantially the same profile can be obtained even if the dose is different.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. Note that both figures are explanatory diagrams for explaining the effect of the second embodiment in comparison with the first embodiment. In FIG. 10, the profile γ
A silicon wafer (silicon substrate) ion-implanted with boron (B) at an implantation energy of 100 keV and a dose of 1.5E16 / cm ² in the same
It is a B diffusion profile at the time of performing heat processing at -100 minutes. The profile δ is such that boron (B) is implanted at an energy of 100 keV and a dose of 0.5E16 / c.
ion-implanted silicon wafer in m ² (silicon substrate)
Shows a B-diffusion profile when each was heat-treated at 1050 ° C. for 100 minutes. Since the supersaturated region S disappeared during the heat treatment, the boron diffusion profile has changed significantly, and the required diaphragm thickness has also changed greatly (it has become thinner).

FIG. 11 shows changes γ ′ and γ ″ in the profile γ when the silicon wafer ion-implanted with boron at an implantation energy of 100 keV and a dose of 1.5E16 / cm ² is processed by changing the diffusion time. Is shown. The supersaturated region S (or U) disappears as the diffusion time increases,
It can be seen that the density of the starting point L decreases.

The dose amount is limited to about 1 to 2E16 / cm ^{2 in} terms of cost / throughput. Therefore, when a supersaturated region is formed by ion implantation and heat treatment, it is advantageous when a thin diaphragm having a thickness of the diaphragm (depth of the boron diffusion layer) of about 1 μm or less is formed. When a diaphragm having a thickness of about 2 μm or more is formed, the dose becomes too large, and the throughput and manufacturing cost become severe.

Therefore, in the second embodiment, boron diffusion is performed by using both the ion implantation method and the solid diffusion method, or using both the ion implantation method and the coating diffusion method. Accordingly, even when a relatively thick diaphragm is formed, the throughput is increased while controlling the ion energy to accurately control the depth of the supersaturated region S.
Cost can be reduced.

In the solid diffusion method, a B ₂ O ₃ plate with stoichiometry is used as a diffusion source, whereas in the coating diffusion method, boron glass (diffusion source) having a lower concentration than the solid source is spin-coated. It is said that the solid diffusion method is superior in diffusion control because it is used as it is, but in recent years, with the progress of coating materials, it has become possible to obtain the same level of uniformity as the solid diffusion method .

However, in the case of performing high-concentration boron diffusion, there are many disadvantages such as the necessity of a high-temperature diffusion furnace using SiC because the coating diffusion method has a small absolute concentration. However, when used together with the ion implantation method as in the present invention, the same results are obtained by the solid diffusion method and the coating diffusion method, and the coating diffusion method is more advantageous in terms of cost and ease of management. become.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In FIG.
Is a profile when boron is diffused into a silicon substrate into which nitrogen (N) is not introduced, and a profile ni (i
= 1, 2) are profiles when boron diffusion is performed on a silicon substrate into which nitrogen (N) has been introduced, and both are compared by heat treatment in the same batch. Profile n
Numeral 1 indicates the case where the diffusion time is the same as that of the profile a, and profile n2 indicates the case where the diffusion time is increased and the boron stop point is aligned with the boron stop point Ta of the profile a.

As shown in the figure, the profile n1 in which N is introduced
Indicates that the diffusion is suppressed (the diffusion coefficient is lowered) as compared with the profile a in which N is not introduced. Further, as can be seen by comparing the profile n2 with the profile a, the profile n2 when N is introduced becomes sharper (the gradient of the concentration distribution in the depth direction is high), and boron is introduced by introducing nitrogen. Stop control can be performed precisely. However, the throughput is slightly reduced in the profile n2 because the diffusion time is longer, but is advantageous in controllability and reproducibility.

By forming a boron diffusion layer on a silicon substrate into which nitrogen (N) has been introduced, a diaphragm having a relatively small thickness can be formed with high precision.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
3 will be described. In FIG.
Is a depth profile in which boron ions are implanted into a silicon substrate and boron is diffused by a normal diffusion furnace. In the profile ni (i = 1, 2), boron is similarly ion-implanted into a silicon substrate, and RTA (Rapid Thermal Anneal) is performed.
= A method in which heat treatment is performed instantaneously (several seconds) to perform boron diffusion and activation, and both are compared by heat treatment using RTA under the same conditions. Here, profile n2 shows a case where the diffusion time (annealing time) is longer than normal (heat treatment sufficient for activation) and aligned with the boron stop point of profile a. The profile n1 is a case where a silicon substrate into which N is introduced is used, and shows a case where ion implantation and RTA processing are performed under the same conditions as those of n2.

By performing the heat treatment by RTA as described above, diffusion (drive) of ion-implanted boron is suppressed and activation is relatively promoted. Therefore, the controllability of the diffusion layer depth is good, and Since the diffusion profile becomes sharp (the concentration gradient is high), the controllability of the etching stop also increases. The diffusion profile obtained by the RTA process has a slightly different shape from a normal diffusion profile (for example, the profile shown in FIG. 12).

It can be seen from the figure that the diffusion of the profile n1 in which N is introduced is suppressed more than the profile n2 in which N is not introduced (the diffusion coefficient is lowered). Further, as can be seen by comparing the profiles n1 and n2, the profile n1 when N is introduced becomes sharper (the gradient of the concentration distribution in the depth direction is high), and boron is introduced by introducing nitrogen. Stop control can be performed precisely.

As described above, the ion-implanted boron is changed to R
By forming a boron diffusion layer on a silicon substrate by performing heat treatment by a TA method, a diaphragm having a relatively small thickness can be formed with high precision. Further, as described above, the boron ion-implanted into the silicon substrate into which nitrogen (N) has been introduced is subjected to RT.
By forming a boron diffusion layer by heat treatment in Method A,
Further, the controllability of the depth of the diffusion layer is improved, and the etching stop property is improved.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, a boron diffusion layer is formed only in a region where boron is stopped to form a diaphragm. In the figure, a profile a is a depth profile when the entire region of the diaphragm is a boron diffusion layer, and a boron diffusion layer of a profile b having the same boron stop point Ta is added to a portion to be a part of the diaphragm. By forming the diaphragm, a diaphragm having the same thickness can be formed. Profile b 'is a case where the profile is sharper than profile b.

As described above, when the desired high-concentration boron diffusion layer is formed only in the region where boron is stopped, the internal resistance of the diaphragm becomes small instead of the large specific resistance of the diaphragm, so that the vibration durability is high. Become. In addition, since diffusion is not required (however, activation is required), as can be seen from the figure, the profile is sharp, boron stop control is extremely easy, and precise diaphragm thickness control is possible. .

Furthermore, the micro-roughness is large on a normal high-concentration boron diffusion surface, and it is necessary to reduce the micro-roughness by polishing the surface of the silicon substrate when bonding the boron diffusion surface to another silicon substrate. However, by forming a diffusion layer only in the boron stop region in this way, there is no boron diffusion layer on the silicon surface, so there is no micro-roughness, and direct bonding can be easily performed without polishing the silicon substrate. It can be carried out.

Here, in order to form a high-concentration boron diffusion layer only in the region where boron is to be stopped, for example, high-energy ion implantation (MeV ion implantation) is used. By using the MeV implantation method, an extremely high-precision and sharp diffusion profile can be formed directly at the depth at which etching is to be stopped within the range where MeV implantation is possible, so that the controllability of the diffusion layer depth becomes extremely high. The controllability of the etching stop also becomes extremely high. In general, MeV implantation can be performed to a depth of about several μm.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, nitrogen (N) is introduced into the region where boron is stopped. As described above, by introducing nitrogen (N), boron diffusion can be suppressed, and the diffusion coefficient can be reduced only in a region having a desired depth in the silicon substrate. That is, in the same figure, by introducing nitrogen N into the region where boron is stopped as indicated by profile n, a sharp profile b having the same boron stop point Ta as profile a can be obtained.

As described above, by introducing nitrogen (N) into the region where boron is stopped, a diaphragm having low specific resistance can be formed with good controllability.

Next, a seventh embodiment of the present invention will be described with reference to FIG.
6 and FIG. In this embodiment,
After forming a boron diffusion layer and removing a diffusion source (for example, a deposit from a boron diffusion plate or a coating material for coating diffusion), before performing an additional or subsequent heat treatment (such as a heat treatment in direct bonding), Boron is implanted into the surface on the diffusion surface side.

That is, as shown in FIG. 16, when a high-temperature heat treatment is applied without boron implantation after removing the diffusion source, the profile a before the heat treatment is changed to the profile a 'after the heat treatment. Change (decrease in concentration)
And the boron stop point changes from Ta to Ta ′.

On the other hand, as shown in FIG. 17, when boron is implanted from the diffusion side surface as shown by the profile b after the removal of the diffusion source, and a high-temperature heat treatment is applied,
Profile a before heat treatment and profile a after heat treatment
′, The change in the profile (density decrease) is reduced, and the change in the boron stop points Ta and Ta ′ is also reduced.

As described above, after the boron is diffused into the silicon substrate to remove the diffusion source, boron is implanted into the surface on the diffusion side, and then heat treatment is performed to suppress a change in the profile (a decrease in boron concentration). And reprofile control becomes easy.

In this case, by changing the diffusion coefficient in the region having the highest concentration near the surface of the diffusion layer by performing nitrogen ion implantation instead of boron implantation before performing the heat treatment, the profile change can be achieved. (Decrease in boron concentration) can be suppressed. In this case, the effect is lower than that of boron implantation, but the cost is low and the process is easy.

In each of the above embodiments, an example is described in which the droplet discharge head is an electrostatic ink jet head, but the present invention can also be applied to a piezo ink jet head using a piezoelectric element.

The head manufacturing process when applied to a piezo type ink jet head will be briefly described with reference to FIG. First, as shown in FIG. 1A, a silicon substrate 31 having a crystal plane orientation (110) serving as a flow path substrate is used.
To form a high-concentration boron diffusion layer 32.

On the other hand, as shown in FIG. 2B, a silicon substrate is used as the electrode substrate 33, a thermal oxide film 33a is formed on the silicon substrate, and a concave portion 34 is formed in the thermal oxide film 33a. A laminated piezoelectric body 35 is provided on the bottom surface of the recess 34.

Then, as shown in FIG. 7C, the silicon substrate 31 serving as the flow path substrate and the electrode substrate 33 are joined by a process such as direct joining (Si-Direct-Bonding), and then, as shown in FIG. As shown in FIG. 5, an etching mask layer (not shown) is formed, and the silicon substrate 31 is alkali-etched to form a recess 36 serving as a liquid chamber using the boron diffusion layer 32 as an etching stop. Flow path substrate 3 on which a vibrating plate 37 is formed
Get 8.

Finally, as shown in FIG.
The nozzle plate 40 formed with 9 is adhesively bonded to the flow path substrate 38 as shown in FIG.

In the piezo type ink jet head, the piezoelectric element is not limited to the above-described laminated type piezoelectric element, but a surface bending type piezoelectric element can also be used.

In each of the above embodiments, an example has been described in which the present invention is applied to an ink jet head as a droplet discharging head. However, the present invention is similarly applied to a droplet discharging head for discharging other droplets, for example, a resist droplet. Can be. Further, a microactuator composed of a diaphragm and an electrode or a diaphragm and an electromechanical transducer such as a piezoelectric element,
The present invention can be applied not only to the droplet discharge head but also to an actuator such as a micromotor or a micropump, so that the present invention can be applied to these microactuators.

[0075]

As described above, according to the first aspect of the present invention, the diaphragm is formed of a boron diffusion layer, and a part of the boron diffusion layer includes a supersaturated region. , The variation in the thickness of the diaphragm is reduced, and the variation in the droplet discharge characteristics is reduced.

According to the droplet discharge head of the second aspect, since a part of the vibration plate is formed of the boron diffusion layer, the concentration profile becomes sharp and the etching stop property is improved.
The variation in the thickness of the diaphragm is reduced, the variation in the droplet discharge characteristics is reduced, the durability of the diaphragm is improved, and the direct joining is facilitated.

According to the third aspect of the present invention, since the diaphragm is made of the boron diffusion layer into which nitrogen is introduced, the concentration profile becomes sharp, and the etching stop property is improved. The variation in the droplet discharge characteristics is reduced, and the variation in the droplet discharge characteristics is reduced.

According to the fourth aspect of the present invention, since a part of the vibration plate is formed of the boron diffusion layer into which nitrogen is introduced, the diffusion coefficient can be reduced only in a region having a desired depth. A diaphragm having a low resistance can be formed with good controllability, and a variation in the thickness of the diaphragm can be reduced, so that a variation in droplet discharge characteristics can be reduced.

According to the method of manufacturing a droplet discharge head according to the fifth aspect, since the boron diffusion layer is formed by the ion implantation method and the heat treatment, the supersaturated region can be accurately controlled. A thin diaphragm can be formed with high accuracy, and variations in droplet discharge characteristics can be reduced.

According to the method of manufacturing a droplet discharge head of claim 6, since the boron diffusion layer is formed by the ion implantation method and the solid diffusion method, the supersaturated region can be controlled accurately, and Thick diaphragms with little variation can be manufactured at high throughput at low cost.

According to the method of manufacturing a droplet discharge head according to claim 7, since the boron diffusion layer is formed by the ion implantation method and the coating diffusion method, the supersaturated region can be controlled accurately, and the thickness can be reduced. Thick diaphragms with little variation can be manufactured at high throughput at low cost.

According to the method of manufacturing a droplet discharge head of claim 8, since the boron diffusion layer is formed on the silicon substrate by the ion implantation method and the RTA method, the controllability of the diffusion layer depth is good.
The diffusion profile becomes sharp, and a thin diaphragm with small thickness variation can be formed.

According to the method of manufacturing a droplet discharge head of the ninth aspect, the boron diffusion layer is formed on the silicon substrate into which nitrogen has been introduced by the ion implantation method and the RTA method, so that the controllability of the diffusion layer depth is further improved. In addition, a thin diaphragm having a sharp diffusion profile and a small thickness variation can be formed with higher precision.

According to the method of manufacturing a droplet discharge head of claim 10, since the boron diffusion layer is formed by the high energy ion implantation method, the controllability of the diffusion layer depth and the etching stop can be extremely enhanced. Thus, a diaphragm having a small thickness variation can be formed.

According to the method of manufacturing a droplet discharge head according to the eleventh aspect, after boron is diffused into the silicon substrate to remove the diffusion source, boron ions are implanted into the surface on the diffusion side and then heat treatment is performed. The change in the diffusion profile due to the heat treatment can be reduced, the reprofile control can be easily performed, and a diaphragm with a small thickness variation can be formed with high accuracy.

According to the method of manufacturing a droplet discharge head according to the twelfth aspect, after boron is diffused into the silicon substrate to remove the diffusion source, nitrogen ions are implanted into the surface on the diffusion side, and then heat treatment is performed. The change in the diffusion profile due to the heat treatment can be reduced, the reprofile control is facilitated, and a diaphragm having a small thickness variation with high accuracy can be formed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an electrostatic inkjet head to which the present invention is applied.

FIG. 2 is an explanatory top view showing the transmission state of the head.

FIG. 3 is a schematic cross-sectional explanatory view along a long side direction of a liquid chamber of the head.

FIG. 4 is a schematic cross-sectional explanatory view of the head along a liquid chamber short side direction.

FIG. 5 is a schematic sectional explanatory view for explaining a manufacturing process of the head.

FIG. 6 is an explanatory diagram illustrating a boron diffusion profile used for describing the first embodiment of the present invention.

FIG. 7 is an explanatory diagram for explaining a boron diffusion profile having no supersaturation region for explaining the operation of the embodiment;

FIG. 8 is an explanatory diagram for explaining a boron diffusion profile having a supersaturated region for explaining the operation of the embodiment;

FIG. 9 is an explanatory diagram illustrating a boron diffusion profile of another example of the embodiment.

FIG. 10 is an explanatory diagram for explaining effects of the second embodiment of the present invention in comparison with the first embodiment;

FIG. 11 is an explanatory diagram for explaining effects of the same embodiment in comparison with the first embodiment;

FIG. 12 is an explanatory diagram illustrating a boron diffusion profile used for describing the operation of the third embodiment of the present invention.

FIG. 13 is an explanatory diagram illustrating a boron diffusion profile used for describing the operation of the fourth embodiment of the present invention.

FIG. 14 is an explanatory diagram illustrating a boron diffusion profile used for describing the operation of the fifth embodiment of the present invention.

FIG. 15 is an explanatory diagram illustrating a boron diffusion profile used for describing the operation of the sixth embodiment of the present invention.

FIG. 16 is an explanatory diagram illustrating a boron diffusion profile used for describing the operation of the seventh embodiment of the present invention.

FIG. 17 is an explanatory view illustrating a boron diffusion profile used for explaining the operation of the seventh embodiment.

FIG. 18 is an explanatory diagram illustrating a head manufacturing process when the present invention is applied to a piezo-type inkjet head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flow path substrate, 3 ... Electrode substrate, 4 ... Nozzle plate, 5 ... Nozzle, 6 ... Liquid chamber, 10 ... Vibration plate, 15 ... Electrode, 21 ... Silicon substrate, 22 ... High concentration boron diffusion layer.

Claims (12)

[Claims] A nozzle for discharging a droplet, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
In a droplet discharge head that discharges droplets from the nozzle by displacing and deforming the vibration plate, the vibration plate is formed of a boron diffusion layer, and a part of the boron diffusion layer includes a supersaturated region. Droplet discharge head. 2. A nozzle for discharging droplets, a liquid chamber to which the nozzle communicates, a diaphragm forming a wall surface of the liquid chamber,
A droplet discharge head for discharging a droplet from the nozzle by displacing and deforming the diaphragm, wherein only a part of the diaphragm is formed of a boron diffusion layer. 3. A nozzle for discharging liquid droplets, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
A droplet discharge head for discharging droplets from the nozzle by displacing and deforming the diaphragm, wherein the diaphragm is formed of a boron diffusion layer into which nitrogen has been introduced. . 4. A nozzle for discharging droplets, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
In a droplet discharge head that discharges droplets from the nozzles by displacing and deforming the diaphragm, a part of the diaphragm is formed of a boron diffusion layer into which nitrogen is introduced. Drop ejection head. 5. A nozzle for discharging liquid droplets, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
In a method for manufacturing a droplet discharge head that discharges droplets from the nozzles by displacing and deforming the diaphragm, a boron diffusion layer that forms all or a part of the diaphragm is formed by ion implantation and heat treatment. A method for manufacturing a droplet discharge head. 6. A nozzle for discharging droplets, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
In a method of manufacturing a droplet discharge head that discharges droplets from the nozzles by displacing and deforming the diaphragm, a boron diffusion layer that forms all or a part of the diaphragm by an ion implantation method and a solid diffusion method. A method for manufacturing a droplet discharge head, comprising: 7. A nozzle for discharging droplets, a liquid chamber to which the nozzle communicates, a diaphragm forming a wall surface of the liquid chamber,
In a method of manufacturing a droplet discharge head that discharges droplets from the nozzles by displacing and deforming the diaphragm, a boron diffusion layer that forms all or a part of the diaphragm by an ion implantation method and a coating diffusion method. A method for manufacturing a droplet discharge head, comprising: 8. A nozzle for discharging droplets, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
In a method of manufacturing a droplet discharge head that discharges droplets from the nozzles by displacing and deforming the diaphragm, a boron diffusion layer forming all or a part of the diaphragm is formed by an ion implantation method and an RTA method. A method for manufacturing a droplet discharge head. 9. A nozzle for discharging droplets, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber,
In a method for manufacturing a droplet discharge head that discharges droplets from the nozzles by displacing and deforming the vibration plate, all or a part of the vibration plate is implanted into a silicon substrate introduced with nitrogen by an ion implantation method and an RTA method. A method for manufacturing a droplet discharge head, comprising forming a boron diffusion layer to be formed. 10. A nozzle for discharging droplets, a liquid chamber to which the nozzle communicates, a vibration plate forming a wall surface of the liquid chamber, and a liquid droplet from the nozzle by displacing and deforming the vibration plate. A method of manufacturing a droplet discharge head for discharging, wherein a boron diffusion layer forming a part of the diaphragm is formed by high energy ion implantation of several hundred keV to several MeV. . 11. A nozzle for discharging droplets, a liquid chamber to which the nozzle communicates, a vibration plate forming a wall surface of the liquid chamber, and a displacement of the vibration plate to cause droplets to be discharged from the nozzle. In the method of manufacturing a droplet discharge head for discharging, a diaphragm is formed by forming a boron diffusion layer on a silicon substrate, removing a boron diffusion source, implanting boron ions into a surface on the diffusion surface side, and then performing a heat treatment. Forming a boron diffusion layer that forms all or part of the droplet discharge head. 12. A nozzle for discharging a droplet, a liquid chamber communicating with the nozzle, a diaphragm forming a wall surface of the liquid chamber, and a droplet being displaced from the nozzle to displace the droplet from the nozzle. In the method of manufacturing a droplet discharge head for discharging, a boron diffusion layer is formed on a silicon substrate, and after removing a boron diffusion source, nitrogen ions are implanted into a diffusion surface side, and thereafter, a heat treatment is performed, so that the entire vibration plate is subjected to heat treatment. Alternatively, a method for manufacturing a droplet discharge head, wherein a boron diffusion layer forming a part thereof is formed.