JP6913493B2 - heater - Google Patents

Description

The present invention relates to a heater provided with a heat generating resistor on the surface of an aluminum nitride (hereinafter, AlN) substrate.

The aluminum nitride heater described in Patent Document 1 is known as a heater provided with a heat generating resistor on the surface of an AlN substrate. In the aluminum nitride heater described in Patent Document 1, a heat generating resistor having a glass component and a metal component is bonded to the surface of an AlN substrate.

Further, Patent Document 2 describes that when the aluminum nitride and the glass component are heated in close contact with each other, the aluminum nitride and the glass component react with each other and foaming occurs. .. Therefore, in the invention described in Patent Document 2, a protective film made _{of α-Al 2} O _{3 is provided between the aluminum nitride and the glass component.}

Japanese Unexamined Patent Publication No. 11-135234 Japanese Unexamined Patent Publication No. 6-340443

However, a protective film made of α-Al ₂ O ₃ in the AlN substrate provided in a heater where the heating resistors are joined with a glass component on the protective layer consisting of the α-Al ₂ O ₃ is under heat cycle In some cases, thermal stress due to the difference in thermal expansion between the AlN substrate and the protective film may occur. As a result, the heat generating resistor together with the protective film may be peeled off from the AlN substrate.

The heater of the present disclosure includes an AlN substrate having an Al—ON layer on its surface, and a heat generating resistor provided on the Al—ON layer and having a glass component and a metal component. The Al—ON layer is an amorphous glass that exists in the form of a film on the surface of the AlN substrate and whose glass component is SiO2.

According to the heater of the present disclosure, the possibility that the heat generating resistor is peeled off from the AlN substrate can be reduced.

It is sectional drawing which shows an example of a heater. It is a top view which shows an example of a heater.

As shown in FIG. 1, the heater 10 is provided on the AlN substrate 1 and the Al—ON layer 2 having the Al—ON layer 2 on the surface, and the heat generating resistor 3 having a glass component and a metal component. To be equipped with. The heater 10 can be used, for example, as a heater for heating a silicon wafer or a heater for heating a copying machine.

The AlN substrate 1 is a plate-shaped member. Examples of the plate shape include those having a rectangular shape on the main surface. The AlN substrate 1 is, for example, mostly an AlN sintered body. The AlN substrate 1 can be obtained, for example, by laminating green sheets produced by the doctor blade method or the calendar method to prepare a molded product, and degreasing and firing the molded product. The AlN sintered body constituting the substrate may contain an auxiliary component serving as a sintering aid. The sintering aid may be selected according to the purpose, and is not particularly limited in type and amount.

The AlN substrate 1 has an Al—ON layer 2 on its surface. The Al-O-N layer 2 mentioned here, AlN and, as AlON phase or _Al 2 _{O 3} oxygen is dissolved in the crystal lattice of AlN, is a layer but are unevenly mixed. Incidentally, both the AlON phase AlN and _Al 2 _{O 3} may be mixed.

The Al—ON layer 2 can be formed by the following method. _{First, since Al (OH) 3} generated by reacting with the moisture contained in the air is present on the surface of the AlN substrate 1, the AlN substrate 1 is immersed in dilute hydrochloric acid for a predetermined time of 1 to 3 minutes. Then, Al (OH) ₃ on the surface is removed. Further, in the stage of firing the AlN substrate 1, Al ₂ O ₃ generated by the dissociation reaction of water of crystallization is dissolved and removed by immersing it in a mixed acid of hydrofluoric acid and nitric acid for about several seconds to 1 minute.

Then, immediately washed with water acid, dew point -70 ° C. of (Tetens formula by saturated water vapor pressure = 2.4 × ¹⁰ -4 kPa) of less and _{O 2} is the substrate surface under the following high-purity _{N 2} gas 0.1ppm Blow off moisture. Thereafter, under atmospheric pressure environment, 100 to 200 ° C. with high purity _{N 2} gas stream of 0.5~10L / min at a gas flow type calcination furnace, the drying of 1～3Hr.

Subsequently, a high-purity O ₂ gas having a dew point of −70 ° C. (saturated water vapor pressure according to the Tetens formula = 2.4 × 10 ^-4 kPa) or less is added to the high-purity N _{2 gas so that the partial pressure is 1 to 20 kPa.} The temperature is raised while mixing using a gas mixer and being introduced into the furnace, and the treatment is performed at a reached temperature of 700 to 1050 ° C. and 10 to 24 hours. By doing so, it becomes difficult for boehmite derived from _{Al (OH) 3 to} be formed on the outermost surface of the AlN substrate 1, and the _{formation of Al 2} O ₃ at a low temperature can be suppressed. As a result, oxygen is sequentially dissolved in AlN, and the Al—ON layer 2 becomes a layer in which AlN and AlON or α-Al ₂ O ₃ are mixed. Further, the firing condition and the gas condition may be selected according to the thickness of the target Al—ON layer 2, but when the thickness of the Al—ON layer 2 is approximately 0.1 to 3 μm, AlN It is possible to make it difficult to inhibit the thermal conductivity of the substrate 1.

The heater 10 has a heat generating resistor 3 on the surface of the Al—ON layer 2 provided on the AlN substrate 1. The heat generation resistor 3 is a member that generates heat by passing electricity. As shown in FIG. 2, the heat generation resistor 3 is formed, for example, in a band shape having a plurality of folded shapes. The heat generation resistor 3 has a glass component and a metal component. Metal and glass may be selected according to the purpose, and the type and amount are not particularly limited. As the glass, for example, SiO _2- ZNO-based glass or borosilicate-based glass can be used.

The heat generation resistor 3 can be produced by the following method. The metal-glass mixed paste to be the heat generation resistor 3 is formed into a predetermined shape by using a known method such as screen printing or inkjet printing, and then dried. Then, it can be obtained by firing at less than 1100 ° C., for example, 700 to 1000 ° C., 0.5 to 3 hours in an environment where the partial pressure of water vapor is dehydrated to 1 kPa or less with silica gel and calcium chloride. The surface of the heat generation resistor 3 may be Ni-plated.

The metal-glass mixed paste may be prepared by mixing a metal powder and a glass powder with a binder resin, a solvent, a plasticizer, and a dispersant in a predetermined ratio by a known method. As the metal powder, for example, silver, silver palladium, platinum or the like can be used. As the binder resin, acrylic resin, ethyl cellulose, polyvinyl butyral, polyvinyl alcohol, or the like can be used. As the solvent, water, α-terpineol, ethyl acetate or the like can be used. As the plasticizer, dibutyl phthalate, dioctyl phthalate, polyethylene glycol and the like can be used. As the dispersant, a phosphoric acid ester, a polycarboxylic acid, or the like can be used.

In the heater 10 of the present embodiment, a heat generating resistor 3 having an Al—ON layer 2 on the surface of the AlN substrate 1 and having a glass component and a metal component is provided on the Al—ON layer 2. There is. As a result, it is possible to reduce the possibility that the heat generating resistor 3 is peeled off while reducing the foaming caused by the reaction between the AlN substrate 1 and the glass component. The reason why the foaming can be reduced is that the reaction with oxygen is reduced because the Al—ON layer 2 is an oxide and / or an oxynitride. Further, it is considered that the reason why the possibility that the heat generating resistor 3 is peeled off can be reduced is that the coefficient of thermal expansion of the Al—ON layer 2 is close to that of the AlN substrate 1.

Further, the amount of N in the Al—ON layer 2 may be 8 mol% or less in terms of AlN. As a result, the heat generation resistor 3 can be prevented from peeling off from the AlN substrate 1. The technical significance of 8 mol% or less will be described later in Examples.

Further, the Al—ON layer 2 may have a _{SiO 2 containing region at the interface with the heat generating resistor 3.} Since the Al—ON layer 2 has SiO ₂ at the interface, the glass component of the Al—ON layer 2 and the heat generating resistor 3 _{can be connected by SiO 2} , so that the anchor effect can be obtained. Can be caused. As a result, the possibility that the heat generating resistor 3 is peeled off can be reduced.

_{The presence of SiO 2 in the} Al—ON layer 2 can be confirmed by the following method. Specifically, a sample of the Al—ON layer 2 directly below the heat generating resistor 3 in the cross section of the heater 10 is prepared by the Ar ion milling method, and while observing with TEM including dark field electron diffraction, EDS is performed. Elemental analysis and EELS spectra may be identified.

Further, the glass component in the heat generating resistor 3 may be amorphous glass having _{SiO 2.} Amorphous glass has high fluidity, and SiO _2, which is a glass component, easily diffuses into the Al—ON layer 2, so that the anchor effect generated between the Al—ON layer 2 and the heat generating resistor 3 is exerted. It can be made more likely to occur.

Further, the glass component may be SiO _2- ZNO-based glass. Since the glass component itself can diffuse from the junction interface between the heat generation resistor 3 and the Al—ON layer 2 toward the inside of the Al—ON layer 2, the heat generation resistance of the Al—ON layer 2 and the heat generation resistance It is possible to reduce the possibility of peeling from the body 3. It is considered that this is because ZnO functions as a flux component.

For the heater 10 having the structure shown in FIG. 2, a plurality of 10 types of samples (Sample Nos. 1 to 10) were prepared as follows. Specifically, the AlN substrate 1 was first prepared.

The AlN substrate 1 is made of an AlN sintered body having a length of 50 mm, a width of 25 mm, and a thickness of 3 mm. The method for producing the AlN substrate 1 is as follows. First, using AlN powder having a purity of 99.9% by mass and an average particle size D50 of 0.5 μm, 80 parts by mass of toluene and 0.5 parts by mass of a dispersant were added to 100 parts by mass of this powder to form a nylon lining. Wet pulverization and mixing were carried out for 48 hours together with a resin-coated ball having a diameter of 20 mm in the ball mill provided with the above.

Subsequently, a plasticizer and a binder were added to the wet pulverized mixed slurry. As the plasticizer, 2 parts by mass of dibutyl phthalate and 2 parts by mass of dioctyl phthalate were added to 100 parts by mass of AlN powder, and 12 parts by mass of polyvinyl butyral as a binder was added in terms of solid content, and wet mixing was performed for another 30 hours. Next, the mixed organic-inorganic mixed slurry was formed into a green sheet having a thickness of 300 μm by the doctor blade method. Next, the green sheets were laminated so as to have a predetermined thickness, and laminated at a temperature of 80 ° C. or higher while applying a pressure equal to or higher than the yield stress of the green sheet, specifically, a pressure of 5 MPa by a uniaxial pressing method.

Next, the obtained laminate was fired at 2000 ° C. for 3 hours in a reducing atmosphere to obtain an AlN sintered body. The obtained AlN sintered body is subjected to thickness processing by rotary grinding and dimensional processing by surface grinding, and the surface on which the heat generating resistor 3 is provided is finished with an arithmetic average roughness Ra of 1.6 μm or less by wrapping. AlN substrate 1 was obtained.

Subsequently, the AlN substrate 1 was immersed in 15% by mass of dilute hydrochloric acid for 2 minutes with respect to 9 types of samples (Sample No. 2 to Sample No. 10), and subsequently, 10% by mass of hydrofluoric acid was added. _{The coatings of Al (OH) 3} and Al ₂ O ₃ were dissolved and removed by immersing in a mixed acid containing pure water as a dilution medium so that the amount of nitric acid was 20% by mass for 10 to 30 seconds. Immediately after that, flows to washing the acid with pure water, the substrate dew point -77 ° C. (wherein due to the saturation vapor pressure of Tetens = 8.0 × ¹⁰ -5 kPa) and impurity _{O 2} is in the high-purity _{N 2} gas 0.09ppm Moisture on the surface was blown off. Subsequently, the sample was placed in an atmospheric pressure environment in a gas flow firing furnace at a flow rate of 1 L / min. 0.99 ° C. with high purity _{N 2} gas stream of, and 3Hr dried. After drying, the furnace continues to add high-purity O ₂ gas with a dew point of −70 ° C. (saturated water vapor pressure according to Tetens' formula = 2.4 × 10 ^-4 _{kPa) to high-purity N 2} gas at a partial pressure of 1 to 20 kPa. The temperature was raised while being introduced into the furnace by mixing using a gas mixer, and the treatment was performed at a reached temperature of 700 to 1050 ° C. and 10 to 24 hours. After completion of the treatment, the material was naturally cooled to room temperature to form an Al—ON layer 2 on the surface of the AlN substrate 1.

For comparison, one type of sample (Sample No. 1) was not subjected to the above treatment, and had a flow rate of 1 L / min in a gas flow type firing furnace under an atmospheric pressure environment. The temperature was raised while introducing the compressed atmosphere of No. 1 into the furnace, and the temperature reached 1200 ° C. for 10 hours. As a result, _{an AlN substrate 1 having an α-Al 2} O ₃ layer on the surface was obtained. This compression atmosphere, just before the furnace inlet, silica gel and dried over calcium chloride, further dew point 25 ° C. (saturated vapor pressure by equation Tetens = 3.2kPa, therefore _{O 2} partial pressure of the compressed air = 20.5KPa ), And then introduced into the furnace.

The 10 kinds of samples were analyzed by the following method.

Sample No. The analysis / analysis method of the Al—ON layer 2 for 2 to 10 will be described. X-ray photoelectron spectroscopy (hereinafter referred to as XPS) was performed on the Al—ON layer 2. First, the Al—ON layer 2 was irradiated with X-rays in a measurement region of φ100 μm, and the elemental composition (atomic%) and the chemical bond state of the sample were analyzed. Also, in the depth direction, Ar ion sputtering was performed in increments of 5 nm, and the elemental composition and chemical bond state at each depth were analyzed. Thereby, the depth until the composition of the AlN substrate 1 is detected is measured, and this depth is defined as the thickness of the Al—ON layer 2. At this time, the value converted to the _{thermal oxide SiO 2 film thickness is adopted as the sputtering depth.}

In addition, the elemental composition, chemical bond state, and crystal state of the Al—ON layer 2 will be analyzed in more microscopic detail. In the cross section of the heater 10, the Al—ON layer 2 was sampled by the Ar ion milling method in the vicinity of the creepage surface of the heat generating resistor 3, and observed with a transmission electron microscope (hereinafter referred to as TEM). At the same time, elemental analysis and electron energy loss spectroscopy (hereinafter referred to as EELS) were performed with EDS. In particular, in order to identify the detected EELS spectrum, the EELS spectrum was also analyzed for related compounds such as _{α-Al 2} O ₃ , Al (OH) _{3, AlON and AlN for reference purposes.}

As a result, the Al—ON layer 2 is composed of Al, O, and N, and based on the dark field electron diffraction and EELS spectrum of the TEM, these are layers in which _{AlN, AlON, and α-Al 2} O _{3 are mixed.} It was confirmed.

Therefore, the amount of N was determined from the XPS spectrum as follows. First, using the element species and the element counts for each depth detected by XPS, the sum of each of the Al2p, O1s, and N1s element counts was calculated in the entire section of the Al—ON layer 2. Next, assuming that the total number of N1s counts is AlN, and the total number of Al counts excluding the total number of N1s counts is Al ₂ O ₃ , the following equation is used. Was defined.

Total number of Al2p counts: a
Total number of N1s counts: b
Total number of O1s counts: c
b = number of AlN molecules ... (1)
(Ab) / 2 = Al ₂ O ₃ number of molecules ... (2)
Equation (2) was set to be true when equation (3) was satisfied.

a ≧ b and (ab) / 2 ≧ 0
c-{(ab) / 2} × 3 ≧ 0 ・ ・ ・ (3)
At this time,
{Number of AlN molecules / (Number of AlN molecules + Number of Al ₂ O ₃ molecules)} x 100
= {2b / (a + b)} × 100 [mol%] ・ ・ ・ (4)
As a formula (4), the amount of N detected by XPS was determined as the AlN-converted value of the amount of N in the Al—ON layer 2 when converted to AlN.

Sample No. For No. 1, the α-Al ₂ O ₃ layer was analyzed by the same method as described above. As a result of the analysis, XPS was measured at a plurality of sites in various samples, but there was no particular difference in the analytical values for each site of the AlN substrate 1, and the sample No. With respect to 2 to 10, the Al—ON layer 2 was uniformly formed on the surface of the AlN substrate 1 with a film thickness of 0.1 μm or more. Sample No. Regarding No. 1, an α-Al ₂ O ₃ layer was formed on the surface of the AlN substrate 1.

Then cut the 10 different samples, Al-O-N layer 2 (Sample Nanba2～10) or _alpha-Al 2 _{O 3} layer in the cross direction a cross section pieces (sample No.1) can be analyzed Ar It was prepared by the ion milling method. This cross-section piece was subjected to elemental analysis and EELS spectrum analysis by EDS while observing by TEM, including dark-field electron diffraction. In order to identify the detected EELS spectrum, the EELS spectrum was also analyzed for related compounds such as _{α-Al 2} O ₃ , Al (OH) _{3, AlON and AlN for reference purposes.} The results of each measurement are shown in Table 1. In Tables 1 and 2, the sample No. Α-Al ₂ O ₃ layer and sample No. 1 in 1. The Al—ON layer 2 in 2 to 10 is described as a bonding base layer.

Sample No. 2-As is clear from the results of Sample No. 10, the Al—ON layer 2 is AlN.
, AlON, α-Al ₂ O ₃ were mixed in the layer. On the other hand, the sample No. which was calcined using the atmosphere in which water vapor was controlled as an atmosphere. An α-Al ₂ O ₃ layer was formed in 1.

In the above-mentioned Al—ON layer 2, the thickness of the Al—ON layer 2 increases as the atmospheric oxygen partial pressure at the time of firing and the firing temperature increase, and the amount of N expressed in terms of AlN conversion concentration decreases monotonically. There is a tendency. From this, it can be seen that in the Al—ON layer 2 in which the Al compound is mixed, α-Al ₂ O ₃ is monotonically increased, and the amounts of AlN and AlON are relatively monotonically decreased.

In addition, sample No. 1 α-Al ₂ O ₃ layer and sample No. 2-No. For the Al—ON layer 2 of 10, the sample was cut, the cross section was processed with an Ar ion beam with a cross section polisher, the structure of the cross section was observed in detail with a scanning electron microscope (hereinafter, SEM), and further. The outermost tissue was observed. Sample No. A plurality of fine cracks were observed in the α-Al ₂ O _{3 layer of No. 1.} On the other hand, no crack was observed in the Al—ON layer 2.

Subsequently, the exothermic resistor 3 was prepared for 10 kinds of samples by the following method.

First, a SiO having a metal ratio of Ag and Pd of Ag / Pd = 70/30% by mass, 70% by mass of Ag-Pd powder having an average particle size D50 of 0.5 μm, and an average particle size D50 of 5.0 μm. and 5 wt% to ₂ -ZnO-B ₂ O ₃ glass powder, a predetermined amount of ethyl cellulose and α- terpineol, dibutyl phthalate, premixed in a mortar with a dispersant, and crushing and kneaded in a three-roll mill , A metal-glass mixed paste serving as the heat generating resistor 3 was prepared.

Next, the metal-glass mixed paste was formed into a predetermined shape by screen printing, dried at 70 ° C., and then subjected to a flow rate of 1 L / min. The temperature was raised while introducing the compressed atmosphere of No. 1 into the furnace, and the temperature reached 850 ° C. for 3 hours. This compressed atmosphere was dehydrated with silica gel and calcium chloride immediately before the introduction port in the furnace, and the partial pressure of water vapor was 0.8 kPa. By the above operation, a heater 10 having the structure shown in FIG. 2 was obtained. Although not shown in FIG. 2, terminals for power supply are fixed with solder.

The evaluations performed on the obtained heaters 10 (Sample No. 1 to Sample No. 10) are as follows.

After rapid heating from 0 ° C. to 150 ° C., a 300-cycle thermal cycle durability test was carried out, with one cycle being forced cooling from the opposite surface of the heat generating resistor 3 from the facing surface of the heat generating resistor 3 using a refrigerant. Before and after the durability test, the heater 10 was left in a constant temperature room at 23 ° C. for 24 hours, and the resistance value of the heat generating resistor 3 was measured. Regarding the resistance value after the durability test, the rate of change ΔR from the initial resistance value was calculated, but when the rate of change ΔR was 0.5% or less, it was judged that there was no deterioration in the characteristics of the heat generating resistor 3.

In addition, before and after the above durability test, each heater 10 was evaluated for flaw detection using a penetrant flaw detector (red check solution). The heater 10 (Sample No. 2 to Sample No. 10) of the present invention was good without cracks or peeling of the heat generating resistor 3. Sample No. for comparison In No. 1, no cracks or peeling were observed in the heat generating resistor 3 before the durability, but a slight coloration of the penetrant flaw detector was seen in _{the α-Al 2} O _{3 layer in the portion where the heat generating resistor 3 was not formed.} Was done. However, after the durability test, cracks were generated in the heat generating resistor 3, and peeling was confirmed along the pattern surface of the heat generating resistor 3.

Furthermore, these samples after the above durability evaluation and the sample No. before the durability evaluation. The bonding strength of the heat generating resistors 3 was examined by the following method for the small pieces provided with the heat generating resistors 3 of 1 to 10. First, Au plating was performed on the heat generating resistor 3 of the sample, masking was performed on the plated surface at arbitrary three places with a polyimide tape having a diameter of 3.5 mm, solder resist was applied, and then the sample was cured at 120 ° C. for 1 Hr. After the resist was cured, the masked polyimide tape was peeled off to form three φ3.5 mm strength measuring portions for each sample. Subsequently, a lead wire obtained by forming 6 stranded Cu wires having a wire diameter of φ0.17 mm was joined to the above-mentioned strength measuring section Au-plated surface using solder having a melting point of 217 ° C. Next, the end of the lead wire was pulled in the vertical direction with a push-pull gauge, and the peeling load of the heat generating resistor 3 was measured. The results of each measurement are shown in Table 2.

Sample No. 2. As is clear from the results of Sample No. 10, the heater 10 in which the Al—ON layer 2 which is the base layer of the heat generating resistor 3 is a layer in which AlN, AlON, and α—Al ₂ O ₃ are mixed is formed. Even after the cold cycle durability test of 300 cycles, the resistance value change rate ΔR of the heat generating resistor 3 was very stable at 0.5% or less. On the other hand, the sample No. of the comparison target. As described above, in No. 1, the heat generating resistor 3 was disconnected after the durability test.

Further, looking at the peel strength of the heat generating resistor 3, the sample No. 2-Sample No. As is clear from the result of No. 10, it was confirmed that the peeling load did not change before and after the durability, and that the peeling load of the heat generating resistor 3 was maintained very strongly at 6N or more even after the durability test. On the other hand, sample No. In No. 1, the peeling load was as small as 1.7 N even before the durability test, and further decreased after the durability test.

In particular, sample No. 6-Sample No. From the result of 10, the amount of N in the Al—ON layer 2 is AlN.
When the converted concentration was 8 mol% or less, it was confirmed that the change in the peeling load before and after the durability test was very small.

1: AlN substrate 2: Al—ON layer 3: Heat generation resistor 10: Heater

Claims (4)

It includes an AlN substrate having an Al—ON layer on its surface, and a heat generating resistor provided on the Al—ON layer and having a glass component and a metal component.
The Al—ON layer exists in the form of a film on the surface of the AlN substrate .
A heater characterized in that the glass component is amorphous glass having SiO2. The heater according to claim 1, wherein the amount of N in the Al—ON layer is 8 mol% or less in terms of AlN. The heater according to claim 1, wherein the Al—ON layer has a SiO2 containing region at an interface with the heat generating resistor. The heater according to claim 1 , wherein the glass component is SiO2-ZnO-based glass.

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