JP2004154969A - Thermal head and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a thermal head in which variation of resistance is suppressed by controlling variation of resistance among a plurality of heating resistors without performing any trimming, and to provide its manufacturing process. <P>SOLUTION: The thermal head 1 comprises a plurality of heating resistors 4a deposited continuously on an alumina substrate 2 having a glaze heat insulation layer 2, and a conductor 5 leading to the opposite end parts in the longitudinal direction of the plurality of heating resistors 4a. An open part 7 for exposing the surface of the plurality of heating resistors 4a is made in the conductor 5 and an insulating inorganic oxide layer 10 of SiO<SB>2</SB>, for example, is provided in the open part 7. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermal head mounted on a photo printer, a thermal printer, and the like, and a method of manufacturing the same.
[0002]
[Prior art and its problems]
A thermal head mounted on a photo printer, a thermal printer, or the like includes a plurality of heating resistors, electrodes (conductors) for supplying power to the heating resistors, a protective layer, and the like, and is generally formed by the following steps. First, a resistance film and a conductor are continuously formed on a substrate, and the resistance value of the resistance film is stabilized by annealing. Next, unnecessary portions of the conductor and the resistive film are removed by photolithography to define the electrode shape, and then the conductor on the heat generating resistor of the resistive film is removed to expose the heat generating resistor. Then, a protective layer is formed on the exposed heating resistor and conductor. As described above, a conventional general thermal head (heat generating portion of the thermal head) is obtained.
[0003]
However, in the above manufacturing process, since the resist is removed in a state where the heating resistor is exposed during the step of removing the conductor on the heating resistor, the surface of the heating resistor is oxidized when removing the resist, There has been a problem that the resistance value varies among a plurality of heating resistors. In order to eliminate this variation, it is conceivable to remove the surface oxide layer of the heating resistor by reverse sputtering or ion beam etching. However, in reverse sputtering or ion beam etching, the surface oxide layer must be removed uniformly ( It is difficult to maintain the initial thickness of the heating resistors), and it is difficult to make the resistance values of the heating resistors uniform. When the protective layer is formed, reverse sputtering is performed to improve the adhesion between the protective layer, the conductor, and the resistive film. However, the resistance value of the plurality of heating resistors varies due to the etching variation of the reverse sputtering. It was gone. Such a variation in the resistance values of the plurality of heating resistors appears as deterioration in print quality (print density unevenness) when the thermal head is mounted on a printer. Therefore, especially for a thermal head used in a color printer or a photo printer, it is necessary to strictly suppress the variation in the resistance value among a plurality of heating resistors in the head.
[0004]
Therefore, conventionally, after forming a head, a trimming process for adjusting a resistance value by applying an appropriate voltage pulse to the heating resistor is performed, thereby making the resistance value of the heating resistor uniform. However, this trimming process must be performed for each head, and is very complicated. In addition, in the trimming process, the resistance value of the heating resistor is forcibly reduced by applying a voltage pulse, so that the life of the heating resistor and, consequently, the life of the head are shortened. Under such circumstances, there is a demand for suppressing the variation in the resistance value of the heating resistor without performing the trimming process.
[0005]
Furthermore, in recent years, there has been a demand for the development of a thermal head that has a small resistance value change even when the applied power increases, so that the thermal head can operate at high speed in response to an increase in data capacity and high-speed processing.
[0006]
[Patent Document]
JP-A-62-4301
JP-A-62-109668
JP-A-62-179956
JP-A-63-185644
[0007]
[Object of the invention]
SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a thermal head capable of suppressing variations in resistance between a plurality of heating resistors without performing a trimming process, and a method of manufacturing the same. Another object of the present invention is to provide a thermal head having a small change in resistance value and a method for manufacturing the same.
[0008]
Summary of the Invention
The present invention prevents the surface of the heating resistor from being oxidized by covering the surface of the heating resistor with an insulating inorganic oxide layer, and protects the heating resistor from etching damage during the manufacturing process, thereby reducing the resistance value of the heating resistor. , And the change in resistance of the heating resistor is reduced by suppressing the annealing effect (crystallization of elements constituting the heating resistor) due to the application of electric power.
[0009]
That is, the present invention relates to a thermal head comprising: a plurality of heating resistors formed continuously on a substrate; and conductors electrically connected to both ends in the resistance length direction of the plurality of heating resistors. An open portion for exposing the surfaces of the plurality of heating resistors is formed, and an insulating inorganic oxide layer made of an inorganic oxide having an insulating property is provided in the open portion.
[0010]
The insulating inorganic oxide layer is made of SiO ₂ , SiON, AlSiO, Al ₂ O ₃ Is preferably formed by any one of the above. With these insulating inorganic oxide materials, it is possible to prevent surface oxidation and etching damage of the heating resistor, and to suppress a change in the resistance value of the heating resistor when the applied power increases.
[0011]
On the insulating inorganic oxide layer and the conductor, a protective layer for protecting the insulating inorganic oxide layer and the conductor from friction during head operation can be formed. In this case, in general, before forming the protective layer, reverse sputtering is performed to improve the adhesion between the protective layer, the insulating inorganic oxide layer, and the conductor. The insulating inorganic oxide layer has a function of preventing surface oxidation of the heating resistor, a function of protecting the heating resistor from damage due to etching, and a function of suppressing a change in resistance value of the heating resistor. It is preferable that the film thickness after the reverse sputtering treatment is 200 ° or more and 2000 ° or less.
[0012]
When the insulating inorganic oxide layer is cut along the resistance length direction of the heat generating resistor, the cross-sectional shape thereof is substantially sharp at both ends in contact with the conductor and flat at the center portion sandwiched between the both ends. It has a concave shape. Such a substantially concave shape is obtained by forming an insulating inorganic oxide layer while leaving a resist for forming an opening for exposing the heating resistor, and then unnecessary portions (other than portions embedded in the opening). Is formed by the removal.
[0013]
In the aspect according to the manufacturing method of the present invention, a step of continuously forming a resistive film and a conductor on a substrate; forming a resist for the conductor that defines the resistance width and the conductor pattern of the heating resistor on the conductor; Removing the conductor and the resistive film that are not covered with the resist and removing the resist for the conductor; forming an open resist on the conductor that defines the resistance length of the heating resistor, and then covering the resist with the open resist. Forming an opening for exposing a plurality of heating resistors by removing conductors that are not present; leaving an insulating inorganic oxide layer made of an inorganic oxide having an insulating property while leaving the opening resist in place, And forming a film on the substrate surface including the plurality of exposed heating resistors; and removing the insulating inorganic oxide layer on the opening resist and the opening resist. There.
[0014]
According to this manufacturing method, since the insulating inorganic oxide layer is embedded in the open portion and covers the surfaces of the plurality of heating resistors, the surface oxidation of the plurality of heating resistors is prevented by the insulating inorganic oxide layer. At the same time, the plurality of heating resistors are protected from damage due to etching or sputtering. Therefore, it is possible to sufficiently suppress the variation in the resistance value between the plurality of heating resistors due to surface oxidation and etching damage. Further, according to the present manufacturing method, since the resistive film and the conductor are continuously formed, no oxide layer is interposed between the resistive film and the conductor, and the resistance of the heating resistor due to poor adhesion between the resistive film and the conductor is reduced. There is no variation in values. This eliminates the need for a conventional trimming process and the like, thereby simplifying the manufacturing process and eliminating the risk of shortening the life of the head. Further, according to the present manufacturing method, since the insulating inorganic oxide layer is formed after forming the opening for exposing the plurality of heating resistors, the insulating inorganic oxide layer and the plurality of heating resistors (of the heating resistor) are formed. Self-alignment of the resistance length L) can be achieved. Further, the conductor is not overlaid on each heat generating resistor via the insulating inorganic oxide layer, and heat loss when the conductor is overlaid can be eliminated.
[0015]
After the step of removing the opening portion resist and the insulating inorganic oxide layer on the opening portion resist, the surfaces of the conductor and the insulating inorganic oxide layer are shaved, and the cut conductor and the insulating inorganic oxide layer are removed. It is preferable to have a step of forming a protective layer on the substrate. This protective layer is a wear-resistant protective layer for protecting the conductor and the insulating inorganic oxide layer from friction generated during operation of the head. In the case of forming this protective layer, the insulating inorganic oxide layer is formed to a thickness of 400 ° to 2200 °, and before forming the protective layer, is cut by about 100 ° using reverse sputtering or the like, and finally, Is preferably in the range of 200 ° to 2000 °.
[0016]
The opening resist is preferably formed of a lift-off resist so that the opening resist and the insulating inorganic oxide layer on the opening resist are removed by lift-off. However, when the conductor is formed of Al, a normal resist layer having no cut in the corner of the base may be used. This is because side etching is likely to occur in the Al conductor, and a cut is made in the corner of the bottom by the side etching that occurs when the conductor is removed, so that even with a normal resist layer, an opening shape substantially equal to that of the lift-off resist is obtained. Can be
[0017]
The conductor is preferably formed of an Al conductor in order to reduce the resistance and the cost. This Al conductor is preferably removed by wet etching or reactive ion etching. Further, the resistive film is formed from a cermet material of a high melting point metal such as Ta-Si-O, TaSiONb, Ti-Si-O, Cr-Si-O, etc., which is likely to have a high resistance, and can be removed by reactive ion etching. preferable.
[0018]
By the way, according to the above-described manufacturing method, an unnecessary portion of the conductor and the resistive film is removed, and then an open portion resist for determining the resistance length of the heating resistor is formed. That is, the opening portion resist is formed on the uneven film surface. For this reason, the resist for the opening may not be uniform, and the accuracy of the resistance length of the heating resistor may be deteriorated. Therefore, in order to specify the resistance length of the heating resistor with high accuracy, it is preferable to use the following manufacturing method.
[0019]
That is, in a method of manufacturing a thermal head according to another aspect of the present invention, a step of continuously forming a resistive film and a conductor on a substrate; forming an opening resist that defines the resistance length of the heating resistor on the conductor; Removing the conductor not covered by the resist for the opening to form an opening for exposing a plurality of heating resistors; an insulating inorganic material made of an inorganic oxide having an insulating property while leaving the resist for the opening; Forming an oxide layer on the surface of the substrate including the opening resist and the plurality of exposed heating resistors; after removing the opening resist and the insulating inorganic oxide layer on the opening resist; Forming a resist for the conductor defining the resistance width of the heating resistor and the conductor pattern on the surface of the substrate; removing the conductor exposed from the resist for the conductor; It is characterized by having: a step of removing and the conductive resist; step for removing the resistive film exposed from the conductive resist; removing the inorganic oxide layer.
[0020]
According to this manufacturing method, the opening resist that determines the resistance length of the heating resistor is formed on the flat conductor. Therefore, the open portion exposing the plurality of heating resistors can be accurately formed, and the resistance length of the heating resistor can be defined with high accuracy.
[0021]
Preferably, after the step of removing the conductor resist, a step of shaving the surface of the conductor and the insulating inorganic oxide layer and forming a protective layer on the shaved conductor and the insulating inorganic oxide layer is preferable. In the case of forming this protective layer, the insulating inorganic oxide layer is formed to a thickness of 400 ° to 2200 °, and before forming the protective layer, is cut by about 100 ° using reverse sputtering or the like, and finally, Is preferably in the range of 200 ° to 2000 °.
[0022]
The opening resist is preferably formed of a lift-off resist so that the opening resist and the insulating inorganic oxide layer on the opening resist are removed by lift-off. However, when the conductor is formed of Al, a normal resist layer having no cut in the corner of the base may be used. This is because side etching is likely to occur in the Al conductor, and a cut is made in the corner of the bottom by the side etching that occurs when the conductor is removed, so that even with a normal resist layer, an opening shape substantially equal to that of the lift-off resist is obtained. Can be
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a sectional view showing the thermal head 1 according to the first embodiment of the present invention, and FIG. 2 is a plan view showing the thermal head 1 (excluding the protective layer 8). The thermal head 1 includes a plurality of heating resistors 4 a, which are continuously formed on an alumina substrate 3 having a glaze insulating layer (glass) 2, and a conductor (electrode) 5 for energizing the plurality of heating resistors 4 a. It has.
[0024]
The plurality of heating resistors 4a are formed on the glaze insulation layer 2 by a cermet material, and a gap for regulating the resistance width W of the heating resistor 4a is provided between adjacent heating resistors 4a as shown in FIG. An area 6 is provided. The gap region 6 is a hole formed to extend in a direction parallel to the resistance length direction (the left-right direction in FIGS. 1 and 2) of the heating resistor 4a. 2, the glaze heat insulating layer 2 is exposed from the gap region 6.
[0025]
The conductor 5 has an opening 7 having an inverted trapezoidal cross section for exposing the plurality of heating resistors 4a. The open portion 7 divides the conductor 5 into one common electrode 5a conducting to all the heating resistors 4a and a plurality of individual electrodes 5b conducting independently to each heating resistor 4a. Are conducted to both ends in the resistance length direction. The electrode width of each individual electrode 5 b is regulated by the gap region 6, and the resistance length L of the heating resistor 4 a is regulated by the opening 7. The conductor 5 is preferably formed of, for example, an Al conductor.
[0026]
An insulating inorganic oxide layer 10 is embedded in the open portion 7 of the conductor 5. The insulating inorganic oxide layer 10 covers the surfaces of the plurality of heating resistors 4a, prevents surface oxidation of the heating resistors 4a, and protects the heating resistors 4a from damage due to etching during the manufacturing process. It is. The insulating inorganic oxide layer 10 is preferably formed of an inorganic oxide having an insulating property. ₂ , SiON, AlSiO, Al ₂ O ₃ Thus, the film is formed to have a thickness of about 200 ° or more and 2000 ° or less. The cross-sectional shape of the insulating inorganic oxide layer 10 is such that when the insulating inorganic oxide layer 10 is cut along the resistance length direction of the heating resistor 4a, the end (inclined surface) of the conductor 5 on the side in contact with the heating resistor 4a. , And has a substantially concave shape including both sharp end portions and a flat central portion sandwiched between the both end portions.
[0027]
On the insulating inorganic oxide layer 10 and the conductor 5, for example, SiAlON or Ta ₂ O ₅ A protective layer 8 made of an abrasion-resistant material such as the above is formed. The protective layer 8 protects the insulating inorganic oxide layer 10 and the conductor 5 from friction generated during operation of the head. Although not shown, the thermal head 1 is further provided with a drive IC, a PCB (Print Circuit Board), and the like for controlling the energization of the heating resistor 4a. The thermal head 1 is mounted on a photo printer, a thermal printer, or the like, and performs printing by applying heat generated by the heating resistor 4a to a thermal paper or an ink ribbon.
[0028]
In the thermal head 1 having the overall structure as described above, the insulating inorganic oxide layer 10 has a function of preventing surface oxidation of the heating resistor 4a, a function of protecting the heating resistor 4a from etching damage, and a function of applying applied power. It has a function of suppressing a change in the resistance value of the heating resistor 4a.
[0029]
Hereinafter, a function of the insulating inorganic oxide layer 10 for suppressing a change in the resistance value of the heating resistor 4a due to the applied power will be described.
[0030]
FIG. 3 shows that a thermal head 1 (FIG. 1) having an insulating inorganic oxide layer 10 and a conventional thermal head 1 '(FIG. 20) having no insulating inorganic oxide layer are applied to a heating resistor 4a. 4 shows a result of a step stress test (SST) in which the resistance value of the heating resistor 4a is measured by changing the magnitude of the power to be applied. Each of the thermal heads 1 and 1 'has been subjected to an annealing treatment (500 ° C.) before the test (immediately after the formation of the resistive film 4 and the conductor 5). The thickness of the protective layer provided in each of the thermal heads 1 and 1 ′ is 4.0 μm, and the insulating inorganic oxide layer 10 provided in the thermal head 1 is made of SiO 2. ₂ This is a film (thickness: 600 °).
[0031]
The step stress test was performed under the following conditions.
[SST condition]
Applied pulse width = 4.3 ms
Applied pulse period = 22.8 ms
Number of applied pulses = 700 pulses
[0032]
In FIG. 3, the vertical axis represents the resistance change rate (%), and the horizontal axis represents the applied power (W). Referring to FIG. 3, the resistance value of the thermal head 1 ′ having no insulating inorganic oxide layer is constant around 0 to 0.05 W, and starts decreasing when the applied power exceeds 0.05 W. It is lowest when the applied power is 0.15 W. When the resistance value reaches this minimum value, the resistance change rate is about -30%. When the applied power exceeds 0.15 W, the resistance value rapidly increases. On the other hand, the resistance value of the thermal head 1 having the insulating inorganic oxide layer 10 is constant from about 0 to 0.12 W, and when the applied power exceeds 0.12 W, the resistance starts to decrease. .19W. When the resistance value reaches this minimum value, the resistance change rate is about -10%. When the applied power exceeds 0.19 W, the resistance value sharply increases.
[0033]
By the way, in general, it is necessary to operate the thermal head within an applied power range where the resistance value is constant in order to prevent the destruction of the heating resistor. That is, as the change in the resistance value of the thermal head with respect to the applied power is smaller, the applied power range in which the resistance value is constant is expanded, so that the maximum power value that can be applied to the thermal head increases, and the thermal head operates at higher speed. be able to.
[0034]
Comparing the test results shown in FIG. 3 with no insulating inorganic oxide layer (thermal head 1 ′) and with insulating inorganic oxide layer 10 (thermal head 1), the initial resistance is almost It is apparent that the rate of change of resistance with respect to the applied power is smaller when the insulating inorganic oxide layer is provided than when the insulating inorganic oxide layer is not provided. Therefore, the applied power range in which the resistance value of the thermal head is constant is more when the insulating inorganic oxide layer is provided (0 to 0.12 W) than when the insulating head does not have the insulating inorganic oxide layer (0 to 0.05 W). It is wider, specifically, about twice (倍 0.12W / 0.05W).
[0035]
FIG. 4 shows the results of a step stress test performed by changing the thickness of the protective layer of a thermal head having an insulating inorganic oxide layer. FIG. 4 shows the results when the thickness of the protective layer is 2.0 μm, 4.0 μm, and 6.0 μm. Each of the thermal heads used in this step stress test was made of SiO 2 as an insulating inorganic oxide layer. ₂ A film (thickness: 600 °) is used, and an annealing process (500 ° C.) is performed before the test (immediately after the formation of the resistance film 4 and the conductor 5). The STT conditions are the same as those in the step stress test performed in FIG.
[0036]
In FIG. 4, the vertical axis represents the rate of resistance change (%), and the horizontal axis represents the applied power (W). Referring to FIG. 4, even when the thicknesses of the protective layers are different, the resistance change rates with respect to the applied power are almost equal. That is, it can be seen that the resistance change rate with respect to the applied power does not depend on the thickness of the protective layer.
[0037]
From the results shown in FIGS. 3 and 4 described above, the present inventors have found that the presence of the insulating inorganic oxide layer suppresses a change in the resistance value of the thermal head due to the applied power. How the insulating inorganic oxide layer contributes to the suppression of the change in the resistance value can be estimated as follows.
[0038]
When the power applied to the thermal head is increased, first, the temperature of the heating resistor rises due to the application of the power, and the heating resistor is in an annealed state due to the temperature rise. At this time, if the insulating inorganic oxide layer does not exist on the heating resistor, the crystallization of the elements constituting the heating resistor (resistive film) proceeds by the above-described annealing, and the elements are ordered. As shown by the solid line A, the resistance value of the thermal head decreases. However, if the insulating inorganic oxide layer is present on the heating resistor, the temperature rise should activate oxygen in the insulating inorganic oxide layer or diffuse the oxide simultaneously with annealing. . Then, as a result of the activated oxygen or the diffused oxide hindering the crystallization of the elements constituting the heating resistor and delaying the crystallization, as shown by the solid line B in FIG. It is considered that the decrease is suppressed (the resistance value can be maintained). Note that the reason why the resistance value of the thermal head starts to increase rapidly from a certain power value is considered to be due to the start of oxidation of the heating resistor (resistive film) and breaking of the crystal bond.
[0039]
Next, an embodiment of a method for manufacturing the thermal head shown in FIG. 1 will be described. 5 to 9 are (a) a sectional view and (b) a plan view showing a manufacturing process of the thermal head 1. In the present embodiment, an alumina substrate (glazed alumina substrate) 3 having a glaze insulating layer 2 is used as the substrate.
[0040]
First, as shown in FIGS. 5A and 5B, a resistive film 4 and a conductor 5 are continuously formed on the entire glaze insulating layer 2 in the same vacuum. Sputtering or vapor deposition can be used for film formation. The resistance film 4 is preferably formed of a cermet material of a high melting point metal such as Ta-Si-O, TaSiONb, Ti-Si-O, Cr-Si-O or the like, which is likely to have a high resistance, and the conductor 5 is formed of Al. Is preferred. Since the resistive film 4 and the conductor 5 are continuously formed in the same vacuum, there is no intervening oxide film between the resistive film 4 and the conductor 5, and the adhesion between the resistive film 4 and the conductor 5 is good.
[0041]
After the resistance film 4 and the conductor 5 are continuously formed, an annealing process is performed. This annealing process is an acceleration process in which a large thermal load is applied in advance to stabilize the resistance value of the resistance film 4 in order to reduce the change in resistance of the heating resistor 4a after the start of using the head.
[0042]
Subsequently, as shown in FIGS. 6A and 6B, a conductor resist (not shown) for defining the resistance width W of the heating resistor to be formed and the conductor pattern is formed on the conductor 5 by photolithography. The conductor 5 and the resistive film 4 which are formed and not covered with the conductor resist are removed, and the conductor resist is peeled off. The area from which the conductor 5 and the resistive film 4 have been removed in this step is the gap region 6, from which the glaze insulating layer 2 is exposed as shown in FIG. When the conductor 5 is removed, wet etching or RIE (reactive ion etching) can be used, and when the resistive film 4 is removed, RIE can be used.
[0043]
Subsequently, as shown in FIGS. 7A and 7B, an opening resist Rr that determines the resistance length L of the heat generating resistor to be formed is formed on the conductor 5, and is covered with the opening resist Rr. The unexposed conductor 5 is removed by wet etching or RIE to form an opening 7 having an inverted trapezoidal cross section. At this time, the end of the conductor 5 (the common electrode 5a and the plurality of individual electrodes 5b) on the open portion 7 side is an inclined surface. By the steps up to FIG. 7, the plurality of heating resistors 4a having the determined resistance length L and resistance width W are exposed, and the conductor 5 is divided into the common electrode 5a and the plurality of individual electrodes 5b. That is, the plurality of heating resistors 4a and the conductors 5 are completed as shown in FIGS. The opening portion resist Rr is preferably a lift-off resist. However, when the conductor 5 is formed of Al, side etching occurs in the conductor 5 at the time of wet etching or RIE even as a normal resist layer (a resist layer having no cut in the bottom corner), and FIG. Since an opening shape substantially equal to that of the lift-off resist as shown is obtained, a normal resist layer may be used.
[0044]
After exposing the plurality of heating resistors 4a, the insulating inorganic oxide layer 10 is entirely formed while leaving the opening resist Rr as shown in FIGS. 8A and 8B. Sputtering or ion beam sputtering is used for film formation. Thereafter, as shown in FIGS. 9A and 9B, the opening resist Rr and the insulating inorganic oxide layer 10 on the opening resist Rr are removed by lift-off. By this step, the insulating inorganic oxide layer 10 is buried in the open portion 7 of the conductor 5, and the surfaces of the exposed heating resistors 4a are covered with the insulating inorganic oxide layer 10. As shown in FIG. 9 (a), the cross-sectional shape of the insulating inorganic oxide layer 10 is such that both ends forming an acute point along the end (inclined surface) of the conductor 5 on the side in contact with the heating resistor 4a. And a flat central portion sandwiched between the two end portions.
[0045]
The insulating inorganic oxide layer 10 is preferably formed of an inorganic oxide having an insulating property. ₂ , SiON, AlSiO, Al ₂ O ₃ It may be formed by any of Further, it is preferable that the insulating inorganic oxide layer 10 be formed to have a thickness of about 400 ° to 2200 °.
[0046]
Subsequently, the insulating inorganic oxide layer 10 and the conductor 5 are removed by a predetermined thickness by reverse sputtering or the like in order to enhance the adhesion with a protective layer formed in a later step. Exposing a new film surface. In this reverse sputtering step, since the plurality of heating resistors 4a are covered with the insulating inorganic oxide layer 10, the plurality of heating resistors 4a are not damaged by etching, and the resistance value of the plurality of heating resistors 4a is reduced. Does not vary. In the present embodiment, the insulating inorganic oxide layer 10 and the conductor 5 are removed by about 100 ° in this step, and finally, the film thickness of the insulating inorganic oxide layer 10 is adjusted within the range of 200 ° to 2000 °. Within this range, the insulating inorganic oxide layer 10 has a function of preventing surface oxidation of the plurality of heating resistors 4a, a function of protecting the plurality of heating resistors 4a from etching damage, and an applied power after the head is completed. The function of suppressing the change in the resistance value of the heating resistor 4a due to the above can be sufficiently exhibited.
[0047]
Then, on the exposed new film surfaces of the insulating inorganic oxide layer 10 and the conductor 5, SiAlON or Ta ₂ O ₅ The protective layer 8 made of a wear-resistant material such as The protective layer 8 can be formed by a bias sputtering method. Thus, the thermal head 1 shown in FIG. 1 can be obtained.
[0048]
By the way, according to the above-described manufacturing method, after the resistance width W of the heating resistor and the conductor pattern are determined, the opening resist Rr that determines the resistance length of the heating resistor is formed. In this case, there is a gap region 6 where the glaze insulating layer 2 is exposed, and the opening portion resist Rr is formed on the uneven film surface. For this reason, it is somewhat difficult to uniformly form the opening portion resist Rr, and there may be a case where the opening portion shape varies as designed. That is, there is a possibility that the resistance length of the heating resistor cannot be defined with high accuracy. Therefore, in order to increase the precision of the resistance length of the heating resistor, it is preferable to use the manufacturing method according to the second embodiment described below.
[0049]
10 to 19 are (a) sectional view and (b) plan view showing the method for manufacturing a thermal head according to the second embodiment of the present invention. The manufacturing method according to the second embodiment is a method in which an opening resist Rr is formed on a flat film surface, and the resistance length L of the heating resistor is accurately defined using the opening resist Rr. 10 to 19, the same reference numerals as in FIGS. 1, 2, and 5 to 9 denote the same components as those in the first embodiment. Also in the second embodiment, an alumina substrate (glazed alumina substrate) 3 having a glaze insulating layer 2 is used as the substrate.
[0050]
First, similarly to the first embodiment (FIG. 5), after the resistive film 4 and the conductor 5 are continuously formed in the same vacuum on the entire surface of the glaze insulating layer 2, an annealing process is performed. Sputtering or vapor deposition can be used for film formation. The resistance film 4 is preferably formed of a cermet material of a high melting point metal such as Ta-Si-O, TaSiONb, Ti-Si-O, Cr-Si-O or the like, which is likely to have a high resistance, and the conductor 5 is formed of Al. Is preferred. Since the resistive film 4 and the conductor 5 are continuously formed in the same vacuum, no oxide film is interposed between the resistive film 4 and the conductor 5, and the adhesion between the resistive film 4 and the conductor 5 is good.
[0051]
Next, as shown in FIGS. 10A and 10B, an opening resist Rr that determines the resistance length L of the heat generating resistor to be formed is formed on the conductor 5. At this time, since the surface of the conductor 5 is flat, the opening portion resist Rr can be accurately formed. Subsequently, as shown in FIGS. 11A and 11B, the conductor 5 not covered with the opening portion resist Rr is removed by wet etching or RIE to form an opening portion 7 having an inverted trapezoidal cross section. The heating resistor 4 a ′ having a predetermined resistance length L is exposed from the opening 7. The conductor 7 is separated from the common electrode side and the individual electrode side by the opening 7.
[0052]
The opening portion resist Rr is preferably formed of a lift-off resist. However, when the conductor 5 is formed of Al, side etching occurs in the conductor 5 at the time of wet etching or RIE even as a normal resist layer (resist layer having no cut in the bottom corner), and FIG. Since an opening shape substantially equal to that of the lift-off resist as shown is obtained, a normal resist layer may be used.
[0053]
After exposing the heating resistor 4a ', the insulating inorganic oxide layer 10 is entirely formed while leaving the opening resist Rr as shown in FIGS. 12 (a) and 12 (b). Sputtering or ion beam sputtering is used for film formation. Thereafter, as shown in FIGS. 13A and 13B, the opening resist Rr and the insulating inorganic oxide layer 10 on the opening resist Rr are removed by lift-off. 12 and 13, the insulating inorganic oxide layer 10 is embedded in the open portion 7 of the conductor 5, and the exposed surface of the heating resistor 4a 'is covered with the insulating inorganic oxide layer 10. Is As shown in FIG. 13A, the cross-sectional shape of the insulating inorganic oxide layer 10 is such that both ends are sharply shaped along the end (inclined surface) of the conductor 5 on the open side, and both ends are formed. It has a substantially concave shape consisting of a flat central portion sandwiched between the two.
[0054]
The insulating inorganic oxide layer 10 is preferably formed of an inorganic oxide having an insulating property, as in the first embodiment. ₂ , SiON, AlSiO, Al ₂ O ₃ It may be formed by any of Further, it is preferable that the insulating inorganic oxide layer 10 be formed to have a thickness of about 400 ° to 2200 °.
[0055]
Subsequently, as shown in FIGS. 14A and 14B, a conductor resist Re for defining the resistance width W and the conductor pattern of the heating resistor 4a 'is formed on the conductor 5 and the insulating inorganic oxide layer 10. After the conductor resist Re is formed, as shown in FIGS. 15A and 15B, the conductor 5 exposed from the conductor resist Re is removed by wet etching or RIE to expose the resistive film 4 from the removed portion. . Subsequently, as shown in FIGS. 16A and 16B, the insulating inorganic oxide layer 10 exposed from the conductor resist Re is removed by wet etching or RIE, and the resistive film 4 is exposed from the removed portion. . Then, as shown in FIGS. 17A and 17B, the resistive film 4 exposed from the conductor resist Re is removed by RIE. The area from which the resistive film 4, the conductor 5, and the insulating inorganic oxide layer 10 have been removed by the steps shown in FIGS. The glaze insulating layer 2 is exposed from the gap region 6, as shown in FIG. The heat generating resistor 4a 'is divided into a plurality of heat generating resistors 4a by the gap region 6, and the resistance width W of each heat generating low rear portion 4a is defined.
[0056]
After the formation of the gap region 6, the conductor resist Re is peeled off. As shown in FIGS. 18A and 18B, the insulating inorganic oxide layer 10 covering the common electrode 5a, the plurality of individual electrodes 5b, and the surface of each heating resistor 4a is exposed from the removed portion of the conductor resist Re. I do.
[0057]
After the conductor resist Re is removed, the insulating inorganic oxide layer 10 and the conductor 5 are removed by a predetermined thickness by reverse sputtering or the like as in the first embodiment, and a new one of the insulating inorganic oxide layer 10 and the conductor 5 is formed. Expose the film surface. In this reverse sputtering step, since the plurality of heating resistors 4a are covered with the insulating inorganic oxide layer 10, the plurality of heating resistors 4a are not damaged by etching, and the resistance value of the plurality of heating resistors 4a is reduced. Does not vary. In this step, the insulating inorganic oxide layer 10 and the conductor 5 are removed by about 100 °, and finally, the film thickness of the insulating inorganic oxide layer 10 is adjusted within a range from 200 ° to 2000 °.
[0058]
Then, as shown in FIGS. 19A and 19B, a new film surface of the exposed insulating inorganic oxide layer 10 and the conductor 5 is formed on the exposed surface of the insulating inorganic oxide layer 10 and the conductor 5. ₂ O ₅ The protective layer 8 made of a wear-resistant material such as For forming the protective layer 8, a bias sputtering method can be used. Thus, the thermal head 100 can be obtained. In the thermal head 100 according to the second embodiment, the insulating inorganic oxide layer 10 exists only on each heating resistor 4a.
[0059]
In each of the above embodiments, the opening portion 7 for exposing the plurality of heating resistors 4a is formed using the opening portion resist Rr, and the insulating inorganic oxide layer 10 is formed while the opening portion resist Rr is left. Therefore, the insulating inorganic oxide layer 10 is embedded in the opening 7. As a result, since the surfaces of the plurality of heating resistors 4a are covered with the insulating inorganic oxide layer 10, in the later manufacturing process, the surface oxidation of the plurality of heating resistors 4a is prevented by the insulating inorganic oxide layer 10. And the plurality of heating resistors 4a can be protected from damage due to etching or sputtering. That is, variation in the resistance values of the plurality of heating resistors 4a due to surface oxidation and etching damage can be sufficiently suppressed. Therefore, the conventional trimming process is unnecessary, and there is no possibility that the life of the head is shortened.
[0060]
In each of the above embodiments, since the insulating inorganic oxide layer 10 is formed after the opening 7 is formed, the insulating inorganic oxide layer 10 and the plurality of heating resistors 4a (the resistance length of the plurality of heating resistors 4a) are set. L) Self-alignment can be achieved. Furthermore, the conductor 5 is not overlaid on each heating resistor 4a via the insulating inorganic oxide layer 10, and the heat loss when the conductor 5 is overlaid can be eliminated. In the present embodiment, the self-alignment of the conductor width and the resistance width W is taken.
[0061]
Further, in each of the above embodiments, since the resistance film 4 and the conductor 5 are continuously formed in the same vacuum, no oxide layer is interposed between the resistance film 4 and the conductor 5 and the resistance film 4 and the conductor 5 are formed. Variations in the resistance value of the heating resistor 4a caused by poor adhesion of the conductor 5 can be eliminated.
[0062]
Furthermore, according to each of the above embodiments, the insulating inorganic oxide layer 10 is present on the plurality of heating resistors 4a with a thickness of about 200 ° to about 2000 °, so that when the applied power is increased, the annealing effect due to the applied power is obtained. (Crystallization of elements constituting the heating resistor 4a) is delayed. As a result, the change in the resistance value of the thermal head with respect to the applied power is smaller than that of the thermal head having no insulating inorganic oxide layer on the heating resistor. That is, even if a larger electric power is applied to the thermal head, the resistance value can be kept constant, and the thermal head can be operated at a higher speed.
[0063]
In the above embodiments, the entire glaze type thermal head 1 in which the glaze insulating layer 3 is formed on the entire surface of the alumina substrate 2 has been described. However, the present invention is applicable to partial glaze, real edge, double glaze, and DOS (Deposit On). It is applicable to other types such as Silicon. Further, the present invention is applicable to a serial head and a line head.
[0064]
In the above embodiments, the alumina substrate 2 is used as the head substrate. However, a silicon substrate can be used instead of the alumina substrate 2. In the case of using a silicon substrate, it is preferable to use a heat insulating layer made of an oxide deposited film or a sputtered film as the heat insulating layer.
[0065]
【The invention's effect】
According to the present invention, since the insulating inorganic oxide layer is buried in the opening for exposing the plurality of heating resistors, the surfaces of the plurality of heating resistors are covered with the insulating inorganic oxide layer, and the plurality of heating resistors are formed. Surface oxidation is prevented and the plurality of heating resistors are protected from damage due to etching. Thereby, the variation in the resistance value between the plurality of heating resistors can be suppressed, and the trimming process or the like becomes unnecessary. Further, according to the present invention, since the insulating inorganic oxide layer is present on the plurality of heating resistors, the annealing effect due to the application of power (crystallization of the elements constituting the heating resistors) is suppressed, and the heating resistance with respect to the applied power is reduced. The change in the resistance value of the body can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a thermal head according to a first embodiment of the present invention.
FIG. 2 is a plan view showing the thermal head of FIG. 1 (a state before a protective layer is formed).
FIG. 3 is a graph showing a result of measuring a change in resistance value with respect to applied power (pulse resistance characteristics) for a thermal head having or not having an insulating inorganic oxide layer.
FIG. 4 is a graph showing the results (pulse resistance characteristics) obtained by measuring the change in resistance value with respect to applied power while changing the thickness of a protective layer of a thermal head having an insulating inorganic oxide layer.
5A is a cross-sectional view and FIG. 5B is a plan view showing one step of a method for manufacturing the thermal head shown in FIG.
6A is a cross-sectional view and FIG. 6B is a plan view of a step performed after the step shown in FIG.
7A is a cross-sectional view and FIG. 7B is a plan view of a step performed after the step shown in FIG.
8A is a cross-sectional view and FIG. 8B is a plan view of a step performed after the step shown in FIG.
9A is a sectional view and FIG. 9B is a plan view of a step performed after the step shown in FIG.
FIGS. 10A and 10B are a sectional view and a plan view showing one step of a method for manufacturing a thermal head according to the second embodiment of the present invention. FIGS.
11A is a sectional view of a step performed after the step shown in FIG. 10, and FIG. 11B is a plan view thereof.
12A is a sectional view and FIG. 12B is a plan view of a step performed after the step shown in FIG.
13A is a cross-sectional view and FIG. 13B is a plan view of a step performed after the step shown in FIG.
14A is a cross-sectional view and FIG. 14B is a plan view of a step performed after the step shown in FIG.
15A is a cross-sectional view and FIG. 15B is a plan view of a step performed after the step shown in FIG.
16 (a) is a sectional view and FIG. 16 (b) is a plan view of a step performed after the step shown in FIG.
17 (a) is a cross-sectional view and FIG. 17 (b) is a plan view of one step performed after the step shown in FIG.
18A is a sectional view of a step performed after the step shown in FIG. 17, and FIG.
19A is a sectional view (a sectional view of a thermal head according to a second embodiment of the present invention) of a step performed after the step shown in FIG. 18, and FIG. 19B is a plan view.
FIG. 20 is a cross-sectional view showing a conventional thermal head having no insulating inorganic oxide layer.
[Explanation of symbols]
1 Thermal head
2 Glaze insulation layer
3 Alumina substrate
4 Resistive film
4a Heating resistor
5 conductor
5a Common electrode
5b Individual electrode
6 gap area (hole)
7 Open part (hole)
8 Protective layer
10 Insulating inorganic oxide layer

Claims (19)

A thermal head comprising: a plurality of heating resistors formed continuously on a substrate; and conductors electrically connected to both ends in the resistance length direction of the plurality of heating resistors.
A thermal head, wherein an opening is formed in the conductor to expose surfaces of the plurality of heating resistors, and an insulating inorganic oxide layer made of an inorganic oxide having an insulating property is provided in the opening. In the thermal head according to claim 1, the thermal head wherein the insulating inorganic oxide layer is formed by any of _{SiO 2, SiON, AlSiO, Al} 2 O 3. 3. The thermal head according to claim 1, further comprising a protective layer formed on the insulating inorganic oxide layer and the conductor, wherein the thickness of the insulating inorganic oxide layer is 200 to 2000 degrees. . 4. The thermal head according to claim 1, wherein when the insulating inorganic oxide layer is cut along a resistance length direction of the heating resistor, a cross-sectional shape of the opening is substantially inverted trapezoidal. 5. The thermal head has a cross-sectional shape of the insulating inorganic oxide layer in which both ends in contact with the conductor are sharp and the central portion sandwiched between the both ends has a substantially concave shape. The thermal head according to any one of claims 1 to 4, wherein the conductor is an Al conductor. Continuously forming a resistive film and a conductor on a substrate;
A step of forming a conductor resist that defines a resistance width and a conductor pattern of the heating resistor on the conductor, removing a conductor and a resistive film that are not covered with the conductor resist, and removing the conductor resist;
Forming a resist for an opening defining the resistance length of the heating resistor on the conductor, and removing an uncovered conductor from the resist for the opening to form an opening for exposing a plurality of heating resistors; ;
Forming an insulating inorganic oxide layer made of an inorganic oxide having an insulating property on a substrate surface including the opening resist and the plurality of exposed heating resistors while leaving the opening resist. And a step of removing the resist for the opening and the insulating inorganic oxide layer on the resist for the opening. 7. The method according to claim 6, wherein the insulating inorganic oxide layer is formed of any one of SiO ₂ , SiON, AlSiO, and Al ₂ O ₃ . 8. The method for manufacturing a thermal head according to claim 6, wherein after the step of removing the opening resist and the insulating inorganic oxide layer on the opening resist, surfaces of the conductor and the insulating inorganic oxide layer. And forming a protective layer on the shaved conductor and the insulating inorganic oxide layer. 9. The method for manufacturing a thermal head according to claim 8, wherein the insulating inorganic oxide layer is formed to a thickness of 400 to 2200.degree. A method of manufacturing a thermal head for cutting a film to a thickness of not less than 2000 mm. 10. The method for manufacturing a thermal head according to claim 6, wherein the opening resist is formed of a lift-off resist, and the opening resist and the insulating inorganic oxide layer on the opening resist are formed. Method for manufacturing a thermal head that removes by lift-off. The method for manufacturing a thermal head according to any one of claims 6 to 10, wherein the conductor is formed of an Al conductor and removed by wet etching or reactive ion etching. The method for manufacturing a thermal head according to any one of claims 6 to 11, wherein the resistive film is removed by reactive ion etching. Continuously forming a resistive film and a conductor on a substrate;
Forming an opening resist that defines the resistance length of the heating resistor on the conductor, removing a conductor that is not covered by the opening resist, and forming an opening that exposes the plurality of heating resistors;
An insulating inorganic oxide layer made of an inorganic oxide having an insulating property is formed on the surface of the substrate including the resist for the opening and the plurality of exposed heating resistors while leaving the resist for the opening. Process;
Removing the resist for the opening portion and the insulating inorganic oxide layer on the resist for the opening portion, and thereafter forming a conductor resist for defining a resistance width and a conductor pattern of the heating resistor on the substrate surface;
Removing the exposed conductor from the conductor resist;
Removing the insulating inorganic oxide layer exposed from the conductor resist;
A method for manufacturing a thermal head, comprising: a step of removing a resistive film exposed from the conductor resist; and a step of removing the conductor resist. In the manufacturing method for a thermal head according to claim 13, _wherein, SiO _{2, SiON, AlSiO,} manufacturing method for a thermal head for forming the insulating inorganic oxide layer by any of _Al 2 _{O 3.} 15. The method for manufacturing a thermal head according to claim 13, wherein after the step of removing the conductor resist, the surfaces of the conductor and the insulating inorganic oxide layer are shaved, and the shaved conductor and the insulating inorganic oxide layer are shaved. A method for manufacturing a thermal head, comprising a step of forming a protective layer thereon. 16. The method for manufacturing a thermal head according to claim 15, wherein the insulating inorganic oxide layer is formed to a thickness of 400 ° to 2200 °, and in forming the protective layer, the insulating inorganic oxide layer is formed to a thickness of 200 °. A method of manufacturing a thermal head for cutting a film to a thickness of not less than 2000 mm. 17. The method for manufacturing a thermal head according to claim 13, wherein the opening resist is formed of a lift-off resist, and the opening resist and an insulating inorganic oxide layer on the opening resist are formed. Method for manufacturing a thermal head that removes by lift-off. The method of manufacturing a thermal head according to any one of claims 13 to 17, wherein the conductor is formed of an Al conductor and removed by wet etching or reactive ion etching. The method of manufacturing a thermal head according to any one of claims 13 to 17, wherein the insulating inorganic oxide and the resistive film are removed by reactive ion etching.

Images