JP2002203663A - Ceramic heater for semiconductor indusry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater with small resistance variation, enabled to accurately and quickly control the temperature, by overcoming the strong effect of oxidation of a heating element due to its thin thickness. SOLUTION: For the ceramic heater having a heating element on the surface of a base board, the heating element is composed of a sintered metal film or a conductive ceramic film, and made to have the thickness of more than 50 μm-500 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater, which is mainly used in the semiconductor industry as an electrostatic chuck, a wafer prober or the like for drying or sputtering. The present invention proposes a ceramic heater which does not fluctuate in resistance value even when used for a long time and has excellent temperature control characteristics.

[0002]

2. Description of the Related Art Generally, a main semiconductor product is manufactured by forming an electronic circuit or the like by applying an etching resist on a photosensitive resin on a silicon wafer and etching the resin. In such a manufacturing method, the liquid photosensitive resin applied to the surface of the silicon wafer must be dried after being applied by a spin coater or the like. The drying is performed by heating the silicon wafer with the photosensitive resin using a heater. Conventionally, as such a heater, a heater in which a heating element is formed on the back surface of a metal substrate such as aluminum is used.

However, such a heater using a metal substrate has the following problems when used for drying semiconductor products. Since the substrate of the heater is made of metal, the thickness of the substrate must be increased to about 15 mm. This is because, in a thin metal plate, warpage or distortion occurs due to thermal expansion caused by heating. As a result, the wafer placed on the metal substrate and heated may be damaged or tilted by the influence. On the other hand, this problem can be solved by increasing the thickness of the substrate, but this increases the weight of the heater and makes it bulky. In addition, when the heating temperature of the heater is controlled by changing the voltage or the amount of current applied to the heating element attached to the substrate, when the metal substrate is thick, the substrate is not affected by changes in the voltage or the amount of current. There is a problem that the temperature does not fluctuate quickly and fluctuates, and it is difficult to control the temperature.
On the other hand, a ceramic heater using a nitride ceramic has been proposed to overcome the problem of the metal substrate (Japanese Patent Laid-Open No. 11-40330).

[0004]

However, even with the above-mentioned prior art, especially even when the substrate is made of ceramic, a serious problem remains if the characteristics are examined in detail by turning the eyes into a heating element. That is, since the heating element pattern formed on the surface of the ceramic substrate is generally formed using a sintered metal and has a small thickness, for example, a thickness variation due to oxidation of the heating element surface may occur early. there were. For this reason, there has been a problem that the resistance value of the heating element fluctuates greatly and accurate temperature control cannot be performed, and a non-uniform temperature distribution is generated on a heating surface of a semiconductor product such as a wafer to be heated. .

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems of the conventional ceramic heater, in particular, the drawback that the heating element is thin and is strongly affected by oxidation, so that the variation in resistance is small, accurate and quick. An object of the present invention is to provide a ceramic heater capable of performing accurate temperature control.

[0006]

As a result of research for realizing the above object, the present inventors have found that the thickness of a heating element formed on the surface of a ceramic heater is reduced to such a degree that the influence of oxidation is small. In addition, the heating element is not formed of a sintered body, but is formed of a non-sintered metal foil, for example, by rolling or plating (especially, electroplating).
It was found that the metal foil formed as described above has excellent quality (homogeneity) as a heating element and can overcome the above-mentioned problems of the sintering heating element. Further, even when a conductive ceramic is used as the heating element, if the thin film pattern is formed in advance and this conductive ceramic thin film is adhered and fixed to the substrate surface, the above-mentioned problem of the sintered heating element can be obtained. I found that the point could be overcome.

[0007] The present invention developed based on such knowledge,
On the surface opposite to the heating surface of the ceramic substrate, a thickness of 50
This is a ceramic heater provided with a heating element of more than μm to 500 μm. In the present invention, it is preferable that the heating element is formed of a non-sintered metal foil or a conductive ceramic thin film, and is adhered and fixed to a substrate surface via an insulating material layer or a heat-resistant resin layer, and Further, in the present invention, it is preferable that the heating element composed of the non-sintered metal foil or the conductive ceramic thin film is covered and fixed together with the substrate with the insulating material.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A feature of the ceramic heater according to the present invention is that the heating element formed on the surface of the ceramic substrate is made thicker than the conventional one, and therefore, a non-sintered metal foil, that is, It is most preferable to use a rolled material formed by rolling (including forging) after melting and refining, or a dense metal foil over a plated material such as electroplated. This is because such a metal foil can be formed to have a uniform thickness even if it is thick, and it is dense, and therefore exhibits a characteristic that the variation in resistance value is small. In addition, even when a conductive ceramic is used as such a heating element, it is thinned in advance and then patterned on the substrate surface, or the metal foil or the thin film is shielded from the atmosphere by a heat-resistant resin layer. Depending on the material)
By forming it below the surface of the ceramic substrate, the thickness can be made uniform and the above-mentioned problems can be overcome. The non-sintered metal foil has the same meaning as the non-sintered metal foil.

As the conductive ceramic, it is desirable to use at least one selected from silicon carbide, tungsten carbide, titanium carbide and carbon. The conductive ceramic thin film may be formed as a heating element pattern by etching or punching after forming the conductive ceramic thin film, or may be formed by sintering after forming the heating element pattern.

The thickness of the non-sintered metal foil or the conductive ceramic thin film is more than 50 μm to 500 μm, preferably 100 to 40 μm.
Desirably, it is 0 μm. This is because if the heater has a thickness of 50 μm or less, the heater is heated to 200 to 300 ° C., and if the heater is used for a long time, the oxide film gradually grows due to oxidation and becomes thicker to increase the resistance. That is, the influence of the oxidation reaction is relatively reduced, and the trouble due to the formation of the oxide film is reduced. On the other hand, if it exceeds 500 μm, the resistance value becomes small and the amount of heat generated does not satisfy the demand, and the function as a heater is insufficient. The metal used is preferably at least one selected from metals and alloys such as nickel, stainless steel, nichrome (Ni-Cr alloy), and kanthal (Fe-Cr-Al alloy). Use plating foil.

The above-mentioned metal foil or conductive ceramic thin film is bonded to the surface of the ceramic substrate by first applying an insulating material to the entire surface of the ceramic substrate and bonding the thick metal foil under the insulating material. After curing (Fig. 2), or by printing a heat-resistant resin on the surface of the ceramic substrate in advance so as to match the heating element pattern, and bonding a metal foil or conductive ceramic thin film on the heat-resistant resin layer. The form of the curing treatment (FIG. 3) is advantageously adapted.

Another method is to place a metal foil or a conductive ceramic thin film on the surface of a ceramic substrate, cover the metal foil or the conductive ceramic thin film with a B-stage insulating material film, and heat-press the same. Alternatively, the cover may be fixed (FIG. 4). Further, as shown in FIG. 5, first, an insulating material layer 3a is formed on the surface of the ceramic substrate.
Then, the pattern (metal foil, conductive ceramic thin film) of the heating element 2 is fixed thereon, and the heat-resistant resin film 3b is further coated and fixed thereon.

As the insulating material, a heat-resistant resin or an inorganic binder can be used. As the inorganic binder, an inorganic sol, a glass paste, or the like can be used.
The inorganic sol becomes an inorganic gel upon curing and functions as an inorganic adhesive. As an example of the heat-resistant resin used for bonding the heating element, a thermosetting resin is desirable, and a polyimide resin,
One or more resins selected from an epoxy resin, a phenolic resin and a silicone resin are preferred. In addition, as the inorganic sol, at least one selected from silica sol, alumina sol, and a hydrolyzed polymer of an alkoxide can be used. An inorganic binder such as an inorganic sol (an inorganic gel after curing) or a glass paste is excellent in heat resistance and does not deteriorate due to heat, and thus is suitable because the heating element does not peel off.

Next, as the pattern of the heating element formed on the surface of the ceramic substrate, for example, as shown in FIG. 1, it is desirable to adopt a pattern divided into at least two or more circuits. This is because, by dividing the circuit, the power supplied to each circuit is controlled to change the amount of heat generated, and the temperature of the heating surface can be easily adjusted. As the pattern of the heating element, a spiral, a concentric circle, an eccentric circle, a bent line, or the like can be adopted. As another method of forming the heating element pattern according to the present invention, for example, a rolled metal foil or a plated metal foil adhered to the surface of a ceramic substrate, a conductive ceramic thin film is etched via an etching resist, or a predetermined predetermined A method in which a punched circuit is bonded to a substrate via an adhesive (resin) can be used.

The ceramic substrate used in the present invention has a size of 0.5 to 25 mm, particularly 0.5 to 5 mm, preferably 0.5 to 25 mm.
A thickness of about 1 to 3 mm is preferable. If it is thinner than 0.5 mm, it is easily broken, while if it is 25 mm or more, the heat capacity becomes too large and the temperature followability is reduced. Further, when the thickness is more than 5 mm, there is no significant difference from the metal substrate. As a material of the ceramic substrate, an oxide ceramic, a nitride ceramic, a carbide ceramic, or the like can be used, and a nitride ceramic and a carbide ceramic are particularly desirable. As the nitride ceramic,
Metal nitride ceramics, for example, at least one or more selected from aluminum nitride, silicon nitride, boron nitride, titanium nitride, and, as the carbide ceramic, metal carbide ceramics, for example, silicon carbide, zirconium carbide, At least one selected from titanium carbide, tantalum carbide, and tungsten carbide is desirable.
Of these ceramics, aluminum nitride is most preferred. Aluminum nitride has a thermal conductivity of 180.
This is because it is the highest, W / m · K, and has excellent temperature followability.

In the present invention, the ceramic substrate is
If necessary, it is preferable to attach a temperature measuring means such as a thermocouple for temperature control. This is because the temperature of the substrate can be controlled by measuring the temperature of the substrate with the thermocouple and changing the voltage and the amount of current applied to the heating element based on the data.

Further, in the ceramic heater according to the present invention, as shown in FIG. 2, a plurality of through-holes 4 are provided in a ceramic substrate, support pins 7 are inserted into the through-holes 4, and the semiconductor wafer and other parts are connected to the pins. It can be used in such a form that it is placed on the top and supported face-to-face with the heating surface of the heater. The support pins can be moved up and down, thereby transferring the semiconductor wafer to a carrier (not shown),
This is effective when receiving a semiconductor wafer from a carrier. In the ceramic heater according to the present invention, the heating surface of the semiconductor wafer is opposite to the surface on which the heating element of the substrate is formed. This is because the heat diffusion effect is increased and the wafer can be uniformly heated.

Next, an example of manufacturing a ceramic heater according to the present invention will be described. (1) A binder or a solvent is added to a powder of an insulating nitride ceramic or an insulating carbide ceramic and mixed well, and then molded. A step of forming a shape (ceramic substrate). In this step, if necessary, a sintering aid such as yttria or a binder is added to powder such as aluminum nitride or silicon carbide, and granulated by a method such as spray drying, and the granules are placed in a mold or the like. This is a step of producing a formed body by pressurizing and forming into a plate shape. In addition, if necessary, support pins 7 used to support the semiconductor wafer on the heated surface of the substrate may be provided on the formed form.
And a bottomed hole 5 in which a temperature measuring element 6 such as a thermocouple is embedded.

Next, the formed product is heated and fired and sintered to produce a ceramic plate (ceramic substrate). At the time of heating and firing in this step, a ceramic substrate without pores can be manufactured by pressurizing the formed body. The heating and sintering may be performed at a sintering temperature or higher, but in the case of a nitride ceramic or a carbide ceramic, 1000 to 2500 ° C.
It is about.

(2) Step of forming a heating element on the ceramic substrate: In this step, a non-sintered metal foil (rolled foil obtained by rolling a melt-refined material, which has been separately manufactured in advance, and electroplating The heating element pattern is formed by etching or punching the obtained plated foil or the conductive ceramic thin film with an acid, an alkali, or the like. This heating element pattern is applied to an uncured heat-resistant resin, an inorganic sol, a glass paste, etc. on the surface of a ceramic substrate or the surface of a non-sintered metal foil or a conductive ceramic thin film. The resin or the inorganic sol is cured, or the glass paste is baked and fixed.

(3) A terminal for connection to a power supply is attached to the end of the pattern of the heating element by soldering. The terminal of the pattern of the heating element can be caulked and fixed without using solder. In this regard, it is difficult to caulk and fix a sintered metal, but a non-sintered metal foil used in the present invention is possible. In addition, a temperature measuring element 6 such as a thermocouple is inserted into the bottomed hole 5 formed from the non-heating surface side of the ceramic substrate, and a heat-resistant resin such as polyimide or a vitreous sealing material is inserted into the hole. Fill and seal together.
In addition, the temperature measuring element 6 may be in a form in which the temperature measuring element 6 is pressed (contacted) on the surface of the substrate.

[0022]

EXAMPLES Example 1 (1) A composition comprising 100 parts by weight of aluminum nitride powder (average particle size 1.1 μm), 4 parts by weight of yttrium oxide (average particle size 0.4 μm), 12 parts by weight of an acrylic binder, and alcohol It was granulated by a spray drier method. (2) The above granular powder was placed in a mold and formed into a flat plate to obtain a formed product. Through holes 4 for inserting support pins 7 for supporting a semiconductor wafer and bottomed holes 5 for embedding thermocouples 6 were formed in predetermined positions of the formed body by drilling. (3) The green compact was hot-pressed at 1800 ° C. and a pressure of 200 kg / cm ² to obtain an aluminum nitride plate having a thickness of 3 mm. This plate was cut out into a circular shape with a diameter of 210 mm to obtain a plate-shaped ceramic substrate 1 made of ceramic. (4) Prepare a rolled metal foil in which a polyethylene terephthalate film is adhered to one side of a stainless steel plate having a thickness of 60 μm, further laminate a photosensitive dry film on the metal foil, and use a mask on which a heating element pattern is drawn. After being exposed to ultraviolet light, the resist was developed with a 0.1% aqueous sodium hydroxide solution to obtain an etching resist. Next, a heating element pattern (stainless steel foil) is formed on the polyethylene terephthalate film by immersing in a mixed solution of hydrofluoric acid and nitric acid to perform an etching treatment, and further developing with a 1N aqueous sodium hydroxide solution. did. (5) Uncured polyimide is applied to one side of the ceramic substrate 1 of (3), and a heating element pattern (foil-like body) is placed on the ceramic substrate 1 so that the metal surface adheres to the uncured polyimide.
The composition was cured by heating at ℃. Thereafter, the polyethylene terephthalate film was peeled off. (6) Use a screen printing method to apply Sn-Pb
The solder paste was printed to form a solder layer. Next, an external terminal connection pin made of Kovar was placed on the solder layer, and heated and reflowed at 360 ° C. to fix the terminal pin. (7) A thermocouple 6 for temperature control was inserted into the bottomed hole 5, and a polyimide resin was embedded therein and heated at 200 ° C. to obtain a ceramic heater.

Example 2 Same as Example 1, except that an acrylic pressure-sensitive adhesive was applied to a ceramic substrate, a 100 μm-thick stainless steel foil was placed thereon, and then the polyethylene terephthalate film was peeled off. Then, a polyimide was applied to a fluororesin sheet, dried and placed on a B-stage polyimide. The polyimide was heated and pressed at 200 kg / cm ² and 200 ° C. to be integrated. Was prepared.

Embodiment 3 This embodiment is basically the same as Embodiment 1, except that a stainless steel foil having a thickness of 400 μm is used.

Example 4 (1) 100 parts by weight of silicon carbide powder (average particle size 1.1 μm), B
₄ C ( ₄ μm average particle size 0.4 μm), acrylic binder 1
A composition comprising 2 parts by weight and alcohol was granulated by a spray drier method. (2) The above granular powder was placed in a mold and formed into a flat plate to obtain a formed product. Through holes 4 for inserting support pins 7 for supporting a semiconductor wafer and bottomed holes 5 for embedding thermocouples 6 were formed in predetermined positions of the formed body by drilling. (3) The formed product was hot-pressed at 1980 ° C. under a pressure of 200 kg / cm ² to obtain a SiC plate having a thickness of 3 mm. This plate was cut out into a circular shape with a diameter of 210 mm to obtain a plate-shaped ceramic substrate 1 made of ceramic. (4) Tungsten carbide having an average particle diameter of 1 μm (W
C) 100 parts by weight of particles, 3.0 parts by weight of acrylic binder, α
-A conductive paste is prepared by mixing 3.5 parts by weight of a terpione solvent and 0.3 parts by weight of a dispersant, and the conductive paste is formed on a vitreous sheet by a screen printing method to form a concentric heating element pattern. A thin film with a glass lining layer having a body pattern was prepared. The thickness of the WC heating element pattern thin film was 60 μm. (5) A glass paste (SHOEI CHEMICAL INDUSTRIES G-5117) is applied to the non-heating surface side of the substrate 1, the WC thin film obtained in the above (4) is placed, and the temperature is raised to 550 ° C. The WC thin film and the glass were laminated and integrated. (6) Use a screen printing method to apply Sn-Pb
The solder paste was printed to form a solder layer. Then, an external terminal connection pin made of Kovar was placed on the solder layer, and heated and reflowed at 360 ° C. to fix the terminal pin. (7) A thermocouple 6 for temperature control was fixed with a polyimide resin and heated at 200 ° C. to obtain a ceramic heater.

Example 5 The thickness of the WC + glass layer as a conductive ceramic thin film was
A ceramic heater having the same configuration as in Example 4 except that the thickness was set to 100 μm was manufactured.

Example 6 The thickness of the WC + glass layer as the conductive ceramic thin film was
A ceramic heater having the same configuration as in Example 4 except that the thickness was set to 400 μm was manufactured.

Comparative Example 1 (1) 100 parts by weight of aluminum nitride powder (average particle size 1.1 μm), 4 parts by weight of yttrium oxide (average particle size 0.4 μm),
A composition comprising 12 parts by weight of an acrylic binder and alcohol was granulated by a spray drier method. (2) The above granular powder was placed in a mold and formed into a flat plate to obtain a formed product. A through hole 4 for inserting a support pin 7 for supporting a semiconductor wafer and a bottomed hole 5 for embedding a thermocouple 6 at a predetermined position of the formed form.
Was formed by drilling. (3) The green compact was hot-pressed at 1800 ° C. and a pressure of 200 kg / cm ² to obtain an aluminum nitride plate having a thickness of 3 mm. This plate was cut out into a circular shape with a diameter of 210 mm to obtain a plate-shaped ceramic substrate 1 made of ceramic. (4) A rolled metal foil obtained by sticking a polyethylene terephthalate film on one side of a stainless steel plate having a thickness of 40 μm was prepared, and a photosensitive dry film was further laminated on the metal foil to draw a heating element pattern. After the mask was exposed to ultraviolet light with a mask, it was developed with a 0.1% aqueous sodium hydroxide solution to obtain an etching resist. Next, a heating element pattern (stainless steel foil) is formed on the polyethylene terephthalate film by immersing in a mixed solution of hydrofluoric acid and nitric acid to perform an etching treatment, and further developing with a 1N aqueous sodium hydroxide solution. did. (5) Uncured polyimide is applied to the surface of the ceramic substrate 1 opposite to the heated surface of (3), and the heating element pattern (stainless steel foil) is bonded to the uncured polyimide on the metal surface. And cured by heating at 200 ° C. to be integrated. Thereafter, the polyethylene terephthalate film was peeled off. (6) A silver-lead solder paste was printed by a screen printing method on a portion where an external terminal for securing connection to a power supply was to be formed, thereby forming a solder layer (made by Tanaka Kikinzoku). Next, a Kovar terminal pin was placed on the solder layer, and heated and reflowed at 360 ° C. to attach the terminal pin to the surface of the heating element. (7) A thermocouple for temperature control was inserted, and a polyimide resin was further embedded to obtain a heater 100.

Comparative Example 2 As in Comparative Example 1, except that a thin film of tungsten carbide (WC) + glass having a thickness of 40 μm was used as a heating element.

With respect to the ceramic heaters of the example and the comparative example, the rate of change in the resistivity (%) of the heating element was examined. as a result,
The results shown in Table 1 below were obtained, and the variation was smaller in the heating element of the present invention. Further, it was left at 250 ° C. for 1000 hours, and the presence or absence of swelling of the heating element was examined.

[0031]

[Table 1]

[0032]

As described above, according to the ceramic heater of the present invention, variation in resistance is small, uniform heating can be realized for a long time, and the life of the heater is improved. Therefore, in drying the liquid resist on the wafer, accurate and quick temperature control can be performed, and it is also useful as a ceramic heater used together with an electrostatic chuck or a wafer prober.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a bottom surface (non-heating surface) of a ceramic heater.

FIG. 2 is a partial cross-sectional view showing one embodiment of the present invention.

FIG. 3 is a partial cross-sectional view showing another embodiment of the present invention.

FIG. 4 is a partial sectional view showing still another embodiment of the present invention.

FIG. 5 is a partial sectional view showing still another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 ceramic substrate 2 heating element 3, 3a, 3b heat-resistant resin layer 4 through hole 5 bottomed hole 6 thermocouple 7 support pin

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[Procedure amendment]

[Submission date] June 4, 2001 (2001.6.4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Ceramic heater for semiconductor industry

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater, which is mainly used in the semiconductor industry as an electrostatic chuck, a wafer prober or the like for drying or sputtering. The present invention proposes a ceramic heater for the semiconductor industry which does not change in resistance value even when used for a long time and has excellent temperature control characteristics.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

The present invention, which has been developed based on such knowledge, provides a semiconductor industry in which a heating element having a thickness of more than 50 μm to 500 μm is provided on a surface opposite to a heating surface of a ceramic substrate.
It is a use ceramic heater. In the present invention, it is preferable that the heating element is formed of a non-sintered metal foil or a conductive ceramic thin film, and is adhered and fixed to a substrate surface via an insulating material layer or a heat-resistant resin layer, and Further, in the present invention, it is preferable that the heating element composed of the non-sintered metal foil or the conductive ceramic thin film is covered and fixed together with the substrate with the insulating material.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 3/16 H05B 3/20 328 3/20 328 H01L 21/30 567 F term (Reference) 3K034 AA02 AA05 AA15 AA21 AA22 AA32. VV40 5F031 CA02 HA02 HA03 HA16 HA33 HA37 NA01 PA30 5F046 KA04

Claims (3)

[Claims] 1. A ceramic heater having a heating element having a thickness of more than 50 μm to 500 μm provided on a surface of a ceramic substrate opposite to a heating surface. 2. The heating element comprises a non-sintered metal foil or a conductive ceramic thin film, and is adhered and fixed to a substrate surface via an insulating material layer or a heat-resistant resin layer. The ceramic heater according to claim 1. 3. The ceramic heater according to claim 1, wherein a heating element made of a non-sintered metal foil or a conductive ceramic thin film is covered and fixed together with the substrate with an insulating material.