JP2001015399A - Wafer heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a time required for heating up or cooling down a wafer to a prescribed processing temperature, by a method wherein the one primary surface of a uniform hot plate which is prescribed in thickness and formed of silicon carbide or boron carbide sintered body is made to serve as a mounting surface where a wafer is mounted, and a feeding section connected to a heating resistor is provided on the other primary surface of the uniform hot plate through the intermediary of an insulating layer. SOLUTION: The one primary surface of a uniform heating plate 2 which is formed of silicon carbide sintered body or boron carbide sintered body is made to serve as a mounting surface 3 where a semiconductor wafer W is mounted, and a heating resistor 5 is provided on the other primary surface of the uniform heating plate through the intermediary of an insulating layer 4 of glass or resin. A feeding section 6 which applies an electric power to the heating resistor 5 is electrically connected to the heating resistor 5. Moreover, the uniform heating plate 2 is as thick as 2 to 7 mm. When the insulating layer 4 is formed of glass, it is preferable that the insulating layer 4 ranges from 100 to 350 μm in thickness (s) and has a thermal expansion coefficient of 32 to 44×10-7/ deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a wafer heating apparatus used to heat a wafer to a temperature of 0 ° C. or lower. For example, a resist solution applied to a wafer such as a semiconductor wafer, a liquid crystal substrate, or a circuit board is dried and baked to form a resist film. It is suitable for.

[0002]

2. Description of the Related Art For example, a wafer heating apparatus is used to heat a semiconductor wafer in a film forming process, an etching process, a resist film attaching process, etc. in a semiconductor device manufacturing process.

When a resist film is applied on a semiconductor wafer, one main surface of a heat equalizing plate 22 made of a metal such as an aluminum alloy or stainless steel is placed on the semiconductor wafer W as shown in FIG. A wafer heating device 21 is used, which is a mounting surface 23 and a plurality of sheathed heaters 25 are in contact with the other main surface and are held by a pressing plate 24. Reference numeral 27 denotes a support frame for supporting the heat equalizing plate 22, and reference numeral 26 denotes a power supply unit electrically connected to the sheath heater 25.

The mounting surface 23 of the wafer heating device 21
After the semiconductor wafer W coated with the resist solution is placed thereon, the sheath heater 25 is heated to heat the semiconductor wafer W on the mounting surface 23 via the soaking plate 22,
The resist solution was dried and baked to attach a resist film on the semiconductor wafer W.

[0005]

However, the wafer heating apparatus 21 shown in FIG. 5 has a very large plate thickness of 15 mm or more from the viewpoint of suppressing thermal deformation of the heat equalizing plate 22, and has a large heat capacity. The time required to heat the product to a predetermined processing temperature and the time required to cool from the processing temperature to around room temperature were increased, resulting in poor productivity.

On the other hand, in the film forming process and the etching process, as shown in FIG. 6, a heating resistor 35 is buried in a disk 32 made of an insulating ceramic mainly composed of alumina, silicon nitride or aluminum nitride. One main surface of the disc-shaped body 32 is used as the mounting surface 33 of the semiconductor wafer W, and the other main surface is provided with a power supply portion 36 electrically connected to the heating resistor 35. A wafer heating device 31 is used.

However, insulating ceramics containing alumina or silicon nitride as a main component are not so good in heat conduction, so that the temperature variation of the mounting surface 33 is relatively large.
In addition, since the heating resistor 35 is embedded in the disk-shaped body 32, the resistance value cannot be adjusted by performing trimming, and the temperature variation of the mounting surface 33 cannot be controlled.

For this reason, a resist film is stuck on the semiconductor wafer W using the wafer heating device 31 shown in FIG. 6 in which the disc-shaped body 32 is made of an insulating ceramic containing alumina or silicon nitride as a main component. When heating is performed, the structure of the resist film to be dried and baked due to temperature unevenness becomes coarse, and the pattern shape becomes uneven due to poor photosensitivity of the resist film at the time of exposure processing. It has been difficult to form a simple wiring at a high density.

On the other hand, insulating ceramics containing aluminum nitride as a main component have a thermal conductivity of 80 W / m · K.
Due to the above excellent characteristics, the mounting surface 33 is easily heated to a uniform temperature, but aluminum nitride reacts with moisture in the atmosphere as shown in Chemical Formula 1 to generate ammonia gas, and this ammonia gas is used for the semiconductor wafer W. There is a problem that the structure of the resist film to be dried and baked thereon is adversely affected, and the exposure accuracy of the resist film during exposure processing is deteriorated.

[0010]

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[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention has been made in consideration of the above problems, and has one main surface of a heat equalizing plate made of a silicon carbide sintered body or a boron carbide sintered body having a thickness of 2 mm to 7 mm. Is a mounting surface on which a wafer is placed, and a heating element is provided on the other main surface via an insulating layer, and a power supply unit electrically connected to the heating resistor is provided to constitute a wafer heating apparatus. .

[0012] The present invention also provides the insulating layer, wherein the insulating layer is formed at 0 ° C to 2 ° C.
The coefficient of thermal expansion in the temperature range of 00 ° C. is 32 to 44 × 1
It is formed of glass of 0 ^-7 / ° C, and its thickness is 100
μm to 350 μm, or the insulating layer is formed of a polyimide resin and has a thickness of 30 to 150 μm.
m.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing an example of a wafer heating apparatus according to the present invention, in which one main surface of a heat equalizing plate 2 made of a silicon carbide sintered body or a boron carbide sintered body is used as a wafer, for example. In addition to the mounting surface 3 on which the semiconductor wafer W is mounted, a heating resistor 5 is formed on the other main surface via an insulating layer 4 such as glass or resin.

As shown in FIG. 2 or FIG. 3, the pattern shape of the heating resistor 5 is a substantially concentric circle composed of an arc-shaped electrode portion 5a and a linear electrode portion 5b, and is not shown. Any shape may be used as long as the mounting surface 3 can be uniformly heated, such as a spiral shape.

Reference numeral 7 denotes a support frame on which the wafer heating device 1 is installed.
Is installed so as to cover the opening. Reference numeral 6 denotes a power supply unit electrically connected to supply current to the heating resistor 5;
Numeral denotes lift pins which are installed in the support frame 7 so as to be able to move up and down, and which mount the semiconductor wafer W on the mounting surface 3 and lift it from the mounting surface 3.

In order to heat the semiconductor wafer W by the wafer heating apparatus 1, the semiconductor wafer W carried above the mounting surface 3 by a transfer arm (not shown) is supported by lift pins 8, and then lift pins The semiconductor wafer W is mounted on the mounting surface 3 by lowering 8. Next, power is supplied to the power supply unit 6 to cause the heat generating resistor 5 to generate heat, thereby heating the semiconductor wafer W on the mounting surface 3 via the insulating layer 4 and the heat equalizing plate 2. According to the present invention, Since the heat equalizing plate 2 is formed of a silicon carbide based sintered body or a boron carbide based sintered body, deformation is small even when heat is applied, and the plate thickness can be reduced, so that the plate is heated to a predetermined processing temperature. , And the cooling time from the predetermined processing temperature to cooling to around room temperature can be shortened, and the productivity can be increased.
Since it has a thermal conductivity of at least m · K, the Joule heat of the heating resistor 5 can be quickly transmitted even with a small thickness, and the temperature variation of the mounting surface 3 can be extremely reduced. Moreover, since it does not react with moisture in the atmosphere and generate gas, even if it is used for attaching the resist film on the semiconductor wafer W, it does not adversely affect the structure of the resist film and has a fine structure. Wiring can be formed at high density.

Although the temperature distribution of the mounting surface 3 may vary depending on the use conditions and the like, according to the present invention, a three-layer structure of the heat equalizing plate 2, the insulating layer 4, and the heat generating resistor 5 is used. Since the resistor 5 is exposed, the resistance value can be adjusted by trimming the heating resistor 5 so that the temperature distribution on the mounting surface 3 becomes uniform according to the use conditions and the like. By the way, in order to satisfy such characteristics, the thickness of the heat equalizing plate 2 is preferably set to 2 mm to 7 mm. This is because if the plate thickness t is less than 2 mm, the plate thickness is too thin and the temperature variation is leveled out, and the effect as the heat equalizing plate 2 is small. This is because it is difficult to equalize the temperature of the mounting surface 3 because it appears as a temperature variation of 3. In contrast, when the thickness t exceeds 7 mm, the heat equalizing plate 2 has a high thermal conductivity. Even though it is made of a boron carbide sintered body, the heat capacity of the heat equalizing plate 2 becomes too large because the thermal conductivity is smaller than that of the metal, and the temperature rising time and the processing temperature until heating to the predetermined processing temperature. This is because the cooling time from cooling to near room temperature becomes longer, and the productivity cannot be improved.

The silicon carbide sintered body forming the heat equalizing plate 2 may be a sintered body containing boron (B) and carbon (C) as sintering aids with respect to silicon carbide as a main component. Alumina (Al) as a sintering aid for silicon carbide as the main component
_A sintered body containing ₂ O ₃ ) and yttria (Y ₂ O ₃ ) can be used, and the silicon carbide is either an α-type or a β-type. No problem.

As the boron carbide sintered body forming the heat equalizing plate 2, a sintered body containing boric acid (B ₂ O ₃ ) as a sintering aid with respect to boron carbide as a main component, A sintered body containing silicon carbide (SiC) as a sintering aid for the component boron carbide can be used.

Further, the main surface of the heat equalizing plate 2 opposite to the mounting surface 3 has a flatness of 20 μm or less and a surface roughness of the center line from the viewpoint of enhancing the adhesion to the insulating layer 4 made of glass or resin. It is preferable to polish to an average roughness (Ra) of 0.1 μm to 0.5 μm.

On the other hand, glass or resin can be used as the insulating layer 4 for maintaining insulation between the heat equalizing plate 2 and the heat generating resistor 5 having semi-conductivity. When the thickness is less than 100 μm, the withstand voltage is lower than 1.5 kV, and the insulation property cannot be maintained. On the other hand, when the thickness s exceeds 350 μm, the silicon carbide-based sintered body or the boron carbide-based sintered body forming the heat equalizing plate 2 is formed. Since the difference in thermal expansion between them becomes too large, cracks occur and the insulating layer 4 does not function. Therefore, when glass is used as the insulating layer 4, the thickness s of the insulating layer 4 is preferably formed in the range of 100 μm to 350 μm, and more preferably in the range of 200 μm to 350 μm.

The glass forming the insulating layer 4 may be either crystalline or amorphous, and has a heat resistance of 200 ° C. or higher and a thermal expansion coefficient of 32 ° C. in a temperature range of 0 ° C. to 200 ° C. It is preferable to appropriately select and use those in the range of up to 44 × 10 ⁻⁷ / ° C. That is, if glass having a thermal expansion coefficient outside the above-mentioned range is used, the difference in thermal expansion between the silicon carbide-based sintered body and the boron carbide-based sintered body forming the heat equalizing plate 2 becomes too large. This is because defects such as cracks and peeling are likely to occur during the subsequent cooling.

Next, when a resin is used for the insulating layer 4, if the thickness s is less than 30 μm, the withstand voltage falls below 1.5 kV, the insulation cannot be maintained, and the heating resistor 5 is trimmed by laser processing or the like. When the insulating layer 4 is damaged, the insulating layer 4 does not function as the insulating layer 4. On the other hand, when the thickness s exceeds 150 μm, the amount of evaporation of the solvent and moisture generated during baking of the resin increases, and A bubble-like peeling portion called a blister is formed between them, and the presence of this peeling portion deteriorates heat transfer, so that the soaking of the mounting surface 3 is hindered. Therefore, when a resin is used as the insulating layer 4, the thickness s of the insulating layer 4 is preferably formed in a range of 30 μm to 150 μm, and more preferably in a range of 60 μm to 150 μm.

The resin for forming the insulating layer 4 is as follows.
Considering the heat resistance of 200 ° C. or more and the adhesion to the heating resistor 5, a polyimide resin, a polyimide amide resin, a polyamide resin, or the like is preferable.

As a means for applying the insulating layer 4 made of glass or resin on the heat equalizing plate 2, an appropriate amount of the glass paste or the resin paste is dropped on the center of the heat equalizing plate 2 and spin coating is performed. After spreading and applying evenly, or evenly applying by screen printing, dipping, spray coating, etc., at a temperature of 600 ° C. for glass paste and 300 ° C. for resin paste What is necessary is just to bake at the above temperature. Also,
When glass is used as the insulating layer 4, the heat equalizing plate 2 made of a silicon carbide sintered body or a boron carbide
By heating to a temperature of about ° C. and oxidizing the surface on which the insulating layer 4 is to be adhered, the adhesion with the insulating layer 4 made of glass can be increased.

Further, as the heating resistor 5 to be deposited on the insulating layer 4, a simple metal such as gold (Au), silver (Ag), copper (Cu), palladium (Pd) is formed by a vapor deposition method or a plating method. Directly, or the above-mentioned metal simple substance, rhenium oxide (Re ₂ O ₃ ), lanthanum manganate (LaMnO ₂ )
₃ ) A resin paste or a glass paste containing an oxide such as an oxide as a conductive material is prepared, printed in a predetermined pattern shape by a screen printing method or the like, and then baked to bond the conductive material with a matrix made of resin or glass. good. When glass is used as a metric, either crystallized glass or amorphous glass may be used, but it is preferable to use crystallized glass in order to suppress a change in resistance value due to a heat cycle.

However, when silver or copper is used for the heating resistor 5, migration may occur. In such a case, the insulating layer 4 covers the heating resistor 5.
A protective film made of the same material as described above may be coated with a thickness of about 30 μm.

FIG. 1 shows an example in which the power supply section 6 is joined to the heating resistor 5 with a conductive adhesive. However, as shown in FIG. You may press it with 10.

[0030]

(Example 1) A plurality of disc-shaped soaking plates having a diameter of 230 mm and different thicknesses obtained by subjecting a silicon carbide sintered body having a thermal conductivity of 80 W / m · K to a grinding process and having different thicknesses. The glass paste produced by kneading ethyl cellulose as a binder and terpineol as an organic solvent with glass powder to produce an insulating layer on one main surface of each heat equalizing plate by screen printing. After laying, heating to 150 ° C. to dry the organic solvent, a degreasing treatment is performed at 550 ° C. for 30 minutes, and further baking is performed at a temperature of 700 to 900 ° C. to form an insulating layer made of glass having a thickness of 200 μm. Then, in order to apply a heating resistor on the insulating layer, a glass paste to which Au powder and Pd powder are added as a conductive material is printed in a pattern shape shown in FIG. 3 by a screen printing method. Thereafter, the organic solvent is dried by heating to 150 ° C., and further subjected to a degreasing treatment at 550 ° C. for 30 minutes, and then baked at a temperature of 700 to 900 ° C. to form a heating resistor having a thickness of 50 μm. Thereafter, the wafer heating device was manufactured by fixing the power supply portion to the heating resistor with a conductive adhesive.

Then, by energizing the power supply section of each wafer heating device to generate heat in the heating resistor, the center of the mounting surface is maintained at 150 ° C., and the temperature distribution at that time is measured by a thermoviewer (JTG made by JEOL Datum). -5200), the current was stopped, and the device was naturally cooled, and the time until the center of the mounting surface was cooled to 100 ° C. was measured. When measuring the temperature distribution on the mounting surface, PCD2
The temperature at any six points on the sample No. 00 was measured, and the difference between the maximum value and the minimum value was measured as the temperature variation.

In the evaluation, a sample in which the temperature variation of the mounting surface was within 10 ° C. and the cooling time was within 4 minutes was judged as good.

The results are as shown in Table 1.

[0034]

[Table 1]

As a result, first, it can be seen that as the thickness of the soaking plate increases, the temperature variation on the mounting surface decreases, while the cooling time increases. In other words, it can be seen that the temperature variation of the mounting surface and the cooling time have opposite characteristics. By setting the thickness of the heat equalizing plate to 2 mm to 7 mm, the temperature variation of the mounting surface is within 10 ° C., and the cooling time is 4 minutes.
You can see that it can be done within minutes.

Therefore, it is understood that the thickness of the heat equalizing plate is preferably set to 2 mm to 7 mm, and more preferably, to 2.5 mm to 4 mm.

Example 2 Next, the thickness of the soaking plate was set to 4 mm.
An experiment was conducted in which a wafer heating device was prototyped under the same conditions as in Example 1 except that the thickness of the insulating layer was changed and glass having a different coefficient of thermal expansion was used for the insulating layer, and the withstand voltage of the insulating layer was examined. Was.

In each wafer heating device, the temperature distribution on the mounting surface is measured with a thermoviewer after the trial production, and a conductive sheet made of Au is attached to the heating resistor at a location where the temperature is high, and the temperature variation on the mounting surface is reduced. Trimming was adjusted to be within 1 ° C.

The withstand voltage was evaluated by measuring the amount of leakage current of the insulating layer when increasing the voltage supplied to the power supply unit from 0.5 kV for 10 seconds while maintaining the voltage value. (TOS5051 manufactured by Kogyo Co., Ltd.). When the leakage current exceeded 20 mA, it was judged as dielectric breakdown, and the voltage value at that time was regarded as withstand voltage. Those having a withstand voltage of 1.5 kV or more were judged to be good.

The results are as shown in Table 2.

[0041]

[Table 2]

As a result, the temperature of the glass forming the insulating layer was reduced to 0 ° C.
The coefficient of thermal expansion in the temperature range of ~ 200 ° C is 32 × 10 ^-7
When the voltage was lower than / ° C or higher than 44 × 10 ^-7 / ° C, a crack occurred in the insulating layer when a voltage of 0.5 kV was applied to the power supply section.

Further, the glass for forming the insulating layer is 0 ° C.
The coefficient of thermal expansion in the temperature range of ~ 200 ° C is 32-44x
Even if the thickness is 10 ⁻⁷ / ° C., if the thickness is less than 100 μm, the withstand voltage of 1.5 kV or more cannot be satisfied,
Conversely, if the thickness exceeded 600 μm, cracks occurred during cooling of the insulating layer during the manufacturing process.

On the other hand, if the coefficient of thermal expansion in the temperature range of 0 ° C. to 200 ° C. is in the range of 32 to 44 × 10 ⁻⁷ / ° C. and the thickness is 100 μm to 350 μm, cracks and the like will not occur. , 1.5 kV or more, and a sufficient insulating property could be secured.

Therefore, when the insulating layer is formed of glass, the coefficient of thermal expansion in the temperature range of 0 ° C. to 200 ° C. is 32.
It can be seen that it is sufficient to use glass in the range of up to 44 × 10 ⁻⁷ / ° C. and to set the thickness to 100 μm to 350 μm.

Example 3 Next, the thermal conductivity was 80 W / m.
Grinding the silicon carbide sintered body of K, outer diameter 230
mm, a plurality of disk-shaped soaking plates with a plate thickness of 4 mm,
In order to apply an insulating layer to one main surface of each heat equalizing plate, polyimide varnish (U varnish S: U varnish S) is applied by changing the thickness with a spin coater, and then dried at a temperature of 70 ° C. Further, baking is performed at a temperature of 400 ° C. to 450 ° C. to form an insulating layer made of a polyimide resin, and then Au powder and Pd powder are added as conductive materials to form a heating resistor on the insulating layer. The printed PbO-based glass paste is printed in a pattern shape shown in FIG. 3 by a screen printing method, and then baked at a temperature of 400 to 450 ° C. to form a heating resistor having a thickness of 50 μm. A wafer heating device was manufactured by fixing the power supply portion to the heating resistor with a conductive adhesive.

In order to check the withstand voltage of the insulating layer made of the polyimide resin and the presence or absence of blisters, first, in measuring the withstand voltage, the voltage value applied to the power supply unit was set to 0.5 kV.
The amount of leakage current of the insulating layer when the voltage was sequentially increased for 10 seconds from V was measured using a withstand voltage meter (manufactured by Kikusui Electronics Corporation:
TOS5051), the leakage current amount was 20 m
When the voltage exceeded A, it was judged as dielectric breakdown, the voltage value at that time was regarded as the withstand voltage, and in the measurement of blisters, it was visually confirmed whether blisters were present between the heat equalizing plate and the insulating layer. .

There is no blister and the withstand voltage is 1.5k.
Those with V or more were judged as good.

The results are as shown in Table 3.

[0050]

[Table 3]

As a result, when the insulating layer is formed of a polyimide resin, if the thickness is 30 μm to 150 μm, no blistering occurs and a withstand voltage of 1.5 kV or more can be obtained. Insulation was able to be secured.

[0052]

As described above, according to the present invention, one main surface of a soaking plate made of a silicon carbide sintered body or a boron carbide sintered body having a plate thickness of 2 mm to 7 mm is attached to a wafer. Since the wafer heating device is provided with a mounting surface on which the heat is generated and a power supply section electrically connected to the heat generating resistor via the insulating layer on the other main surface, the heat equalizing plate is provided. Since the heat capacity at the time of heating can be reduced, the time required for heating to the predetermined processing temperature and the time required for cooling from the predetermined processing temperature to around room temperature can be shortened, and the productivity can be increased. In addition, since the substrate has excellent thermal conductivity and can be subjected to trimming for adjusting the resistance value of the heating resistor after manufacturing the wafer heating apparatus, temperature unevenness on the mounting surface can be extremely reduced. Moreover,
Since it does not react with moisture in the atmosphere, when the wafer heating apparatus of the present invention is used for attaching a resist film on a wafer, it does not adversely affect the structure of the resist film, and is excellent during exposure processing. Sensitivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a wafer heating apparatus according to the present invention.

FIG. 2 is a plan view showing a pattern shape of a heating resistor provided in the wafer heating device of the present invention.

FIG. 3 is a plan view showing another pattern shape of the heating resistor provided in the wafer heating apparatus of the present invention.

FIG. 4 is a partial cross-sectional view showing another power supply structure provided in the wafer heating apparatus of the present invention.

FIG. 5 is a sectional view showing a conventional wafer heating apparatus.

FIG. 6 is a sectional view showing another conventional wafer heating apparatus.

[Explanation of symbols]

1: Wafer heating device 2: Heat equalizing plate 3: Placement surface 4: Insulation layer 5: Heating resistor 6: Power supply unit 7: Support frame 8: Lift pin W: Semiconductor wafer

Claims (3)

[Claims] 1. A heat equalizing plate made of a silicon carbide sintered body or a boron carbide sintered body having a thickness of 2 to 7 mm is used as a mounting surface on which a wafer is mounted and the other main surface. A wafer heating apparatus comprising: a heating resistor on a surface thereof; and a power supply unit electrically connected to the heating resistor via an insulating layer. 2. The insulating layer is made of glass having a coefficient of thermal expansion of 32 to 44 × 10 ⁻⁷ / ° C. in a temperature range of 0 ° C. to 200 ° C., and has a thickness of 100 μm to 350 μm. A wafer heating apparatus as described in the above. 3. The insulating layer is made of a polyimide resin.
2. The wafer heating device according to claim 1, wherein the thickness is 30 to 150 [mu] m.