JPH09306816A - Method and device for ashing of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the irregularity of resist temperature when ashing by a method wherein the resist is heated up by a heat radiating means provided opposing to a support stand which supports a substrate, and the quantity of heat applied to the resist is adjusted in such a manner that the temperature of the resist surface becomes higher than the substrate. SOLUTION: A wafer mount 32, which supports a wafer 40 on its upper surface, is provided in a reaction chamber 31, and opposing to the upper surface of the wafer mount 32, an infrared ray irradiation tube 42 his supported by a support part 43 above the wafer mount 32. The relative distance of the infrared ray irradiation tube 42 and the wafer mount 32 can be changed. The relative distance of the infrared ray irradiation tube 42 and the wafer mount 32 is adjusted using a distance adjusting device where the supporting part 43 of the infrared ray irradiation tube 42 is vertically moved. The wafer mount 32 may be vertically moved, or both of them may be combinedly used. By adjusting the relative distance between the infrared ray irradiation tube 42 and the wafer mount 32, the radiant heat quantity, to be applied to the resist 41, can be adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ashing method for a semiconductor device and an ashing device used for the same,
In particular, the present invention relates to a method for ashing a semiconductor device, in which a resist on a semiconductor substrate is directly heated by using a heat radiator, and an ashing device used for the method.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, fine processing is performed by forming a resist pattern, and using the resist pattern as a mask, implanting ion species and etching a semiconductor, an insulating film, a metal film and the like. It is necessary to remove the resist pattern used at this time, and this is generally called ashing. In ashing, the hydrocarbon contained in the novolak resin, which is the main component of the resist, reacts with the active oxygen generated by the oxygen plasma discharge or ozone decomposition reaction to decompose it into gases such as CO ₂ and H ₂ O, and then the wafer. Removed from the surface.

As this ashing device, there are two types, an oxygen plasma discharge type and an optical ozone decomposition type. In the oxygen plasma discharge type ashing apparatus, the active ion species or oxygen ion species generated by plasma discharge under low pressure and the resist of the wafer placed on the heating plate are heated to a high temperature to raise the resist surface temperature. As a result, ashing is performed by reacting with the activated resist molecules. Further, the photo-ozone decomposing type ashing device decomposes ozone under atmospheric pressure by ultraviolet irradiation to generate active oxygen, and heats the resist surface with a high-temperature heating plate to perform ashing.

FIG. 10 is a sectional view of a conventional ashing device. In FIG. 10, 1 is a reaction chamber, 2 is a wafer mounting table, 3 is a gas introduction tube, 4 is a mass flow controller, and 5
Is a gas exhaust pipe, 6 is a variable valve, 7 is a high temperature heater, 8 is a temperature sensor, 9 is an active oxygen generator, 10 is a wafer, 1
1 is a resist.

Next, the operation of the conventional ashing device will be described. In FIG. 10, the mass flow controller 4
And the variable valve 6 are adjusted to adjust the gas introduction pipe 3
From the above, oxygen containing ozone or a gas containing ozone in nitrogen, argon, neon or the like that does not react with ozone is supplied to the reaction chamber 1 via the active oxygen generator 9 provided in the gas introduction pipe 3. When passing through the active oxygen generator 9, active oxygen species and oxygen ion species are formed.

The wafer 10 supported on the wafer mounting table 2 is heated by the high-temperature heating body 7, the surface temperature of the resist 11 on the wafer 10 rises, and the temperature sensor 8 sets a predetermined temperature. Thereby, the resist 1 on the wafer 10
1 is activated, and the activated resist 11 reacts with the active oxygen in the reactive gas supplied to the reaction chamber 1,
Decomposes into gases such as CO ₂ and H ₂ O. The reactive gas after the reaction is appropriately discharged from the gas exhaust pipe 5 together with a gas such as CO ₂ or H ₂ O.

In order to perform the ashing as described above, it is necessary to heat the resist 11. This is because in order for a chemical reaction between the active oxygen species or oxygen ion species in the reactive gas and the resin in the resist 11 to proceed,
This is because there is a reaction temperature. That is, the temperature of the resin is 40
The reaction becomes slower below ℃. On the other hand, if the temperature of the resin is higher than a predetermined temperature, or if the temperature of the novolac resin is, for example, 200 ° C. or higher, the carbonization reaction of the resin may occur in addition to the gas generation reaction of CO ₂ , H ₂ O, etc., and the resist may be burnt on the wafer.

Therefore, in order to prevent the resist from becoming too hot and scorching, and in order to produce a gas such as CO ₂ or H ₂ O in a high yield, the resist is usually heated to 60 ° C. or higher and 150 ° C. or lower and heated. Will be required.

[0009]

The conventional semiconductor device is constructed as described above, and the means for heating the resist 11 is to place the wafer 10 on the high temperature heating body 7 and heat the wafer 10. However, it is an indirect method of raising the resist temperature by conducting heat to the resist surface on the wafer 10. In such an indirect heating method of the wafer 10, the high temperature heating element 7 is caused by the difference in the mounting state of the wafer 10 on the high temperature heating element 7, for example, the difference in the contact state between the back surface of the wafer 10 and the front surface of the high temperature heating element. Variation in the ashing due to changes in the conditions of heat conduction and heat transfer from the wafer 10 to the wafer 10, and also changes in the conditions of heat conduction from the wafer 10 to the resist 11.

Further, in a high-frequency device such as a GaAs IC, an aerial wiring is used as a connection wiring or a crossover wiring of adjacent island-shaped electrode patterns. This aerial wiring reduces the parasitic capacitance of the inter-layer insulation film that electrically separates the metal wirings from each other when the metal wirings are aggregated in a pattern in order to reduce the chip size and the metal wirings are made in multiple layers. It was made into air to do. One of the methods for forming this aerial wiring structure is a selective plating method in which a photoresist is used as a mask material.

FIG. 11 is a cross-sectional view of a semiconductor device showing one step of a process of forming an aerial wiring by a selective plating method according to a conventional device. In FIG. 11, 15 is a lower layer resist, and 16
Is a gold-plated power feeding layer, 17 is an upper layer resist, 18 is metal wiring to be aerial wiring, and 19 is the direction of heat flow during heating.

The process of forming the aerial wiring by the selective plating method is roughly as follows. First, the lower layer resist 15 is patterned in order to form the pillars for floating the metal wiring. Then, the power feeding layer 16 is formed on the surface of the patterned lower layer resist 15 by gold plating. An upper layer resist 17 is applied on the power feeding layer 16 and is patterned so as to expose the power feeding layer 16 in the portion where the overhead wiring is formed. Then, the surface of the power feeding layer 16 whose surface is exposed is plated with gold to form the metal wiring 18. After that, the upper layer resist 17 is removed by ashing. In this step, since the upper layer resist 17 is heated via the wafer mounting table 2, the direction of heat flow is the direction of arrow 19. Therefore, the temperature of the wafer 10 and the lower layer resist 15 becomes higher than that of the upper layer resist 17, deformation of the lower layer resist 15 and expansion of vaporized substances contained in the lower layer resist 15, and in some cases, the power supply layer 16 deforms and bursts. Can cause fatal defects.

Further, the conventional heating method tends to overheat excessively. For example, when GaAs is exposed to the surface and is heated to a high temperature in the ashing process, the surface of the wafer 10 is covered with a resist. The resin scorches and reduces the reliability of the semiconductor device. FIG. 12 is a cross-sectional view of a semiconductor device showing a process step in which a defect has occurred due to the formation of aerial wiring by the selective plating method according to the conventional device. In this figure, 20 is a carbide and 21 is a vaporized substance.

The conventional semiconductor device manufacturing method relating to the ashing device has the above-mentioned problems. The present invention has been made to solve the above problems, and provides an ashing method for a semiconductor device which performs ashing while holding a wafer at a temperature lower than that of a resist to be ashed, and an ashing device used for the same. Is.

As a known document of the resist stripping method, there is JP-A-61-53723, in which a chromium thin film is formed on a quartz substrate and the resist formed on the chromium thin film is treated with oxygen plasma. When stripping by ashing, a resist stripping method is described in which a thermometer is installed in the reaction tube to measure the ambient temperature and control the high frequency output to the material to be treated. In this method, since the chromium thin film formed on the quartz substrate is heated by using high frequency heating, not by heating the resist surface, the temperature inside the resist becomes higher than that at the resist surface.

Further, Japanese Patent Laid-Open No. 3-52221 discloses that
An oxygen gas containing ozone or an inert gas containing ozone is used as the ashing gas, and a heater is provided at the ejection port of the ashing gas ejection nozzle to heat the ashing gas or to irradiate the periphery of the wafer. As described above, there is described a resist processing method for removing unnecessary resist around the wafer when the ashing gas is heated to generate oxygen atom radicals while heating the periphery of the wafer by providing an infrared irradiation light source and applying the resist to the wafer. ing.

[0017]

According to another aspect of the present invention, there is provided a method of ashing a semiconductor device, wherein a support table provided with a resist is supported on a support table provided in a reaction chamber that can be sealed from an external atmosphere. The first step, the second step of introducing a reactive gas that reacts with the resist into the reaction chamber, and the resist is heated by the heat radiating means arranged so as to face the support base, and the resist and the reactive gas A third step of reacting
And a fourth step of appropriately adjusting the amount of heat applied to the resist so that the temperature of the resist surface becomes higher than that of the substrate.

Furthermore, the fourth step is a distance adjusting step of changing the mutual distance between the heat radiating means and the substrate supported by the support, a heat radiating amount adjusting step of the heat radiating means, or a cooling step of cooling the substrate. Any one or a combination thereof is included.

In addition, the first step of supporting the semiconductor substrate on which the resist is provided on the support table provided in the reaction chamber that can be sealed from the external atmosphere, and the reactivity containing the active oxygen in the reaction chamber. A second step of introducing a gas, a third step of heating the resist by a heat radiator arranged so as to face the supporting base, and reacting the resist with active oxygen, and a resist surface rather than a semiconductor substrate. By cooling the semiconductor substrate so that the temperature rises and changing the mutual distance between the thermal radiator and the semiconductor substrate supported by the support, by adjusting the distance or adjusting the radiant heat of the thermal radiator or a combination of these. And a fourth step of appropriately adjusting the amount of heat applied to the resist.

In addition, a semiconductor substrate in which a first resist, a conductive thin film, and a second resist are sequentially arranged on the main surface is mounted on a support table arranged in a reaction chamber that can be sealed from the outside atmosphere. The first step of supporting, the second step of introducing a reactive gas containing active oxygen into the reaction chamber, and the second resist is heated by the heat radiator arranged so as to face the support base, Two
And a third step of reacting the active oxygen with the resist, and cooling the semiconductor substrate so that the temperature of the second resist surface is higher than that of the semiconductor substrate, and the semiconductor supported by the heat radiator and the support base. A fourth step of appropriately adjusting the amount of heat applied to the second resist by adjusting the distance for changing the mutual distance with the substrate, adjusting the amount of radiated heat of the thermal radiator, or a combination thereof. is there.

Further, the ashing device according to the present invention is
A reaction chamber that has an inlet and an outlet for a reaction gas and can be sealed from an external atmosphere, a support table that is provided in the reaction chamber and supports a substrate on which a resist is provided, and a support table that faces the support table. And heat radiating means arranged to adjust the amount of heat applied to the resist so that the temperature of the resist surface is higher than that of the substrate, and active species are formed in the reaction gas in the reaction part. And a reaction gas activating means for performing.

Further, the heat quantity adjusting means changes the distance between the heat radiating means and the substrate supported by the support, or the heat radiating quantity adjusting device of the heat radiating means or the cooling device for cooling the substrate. Any one or a combination thereof is included.

Further, a reaction chamber which has an inlet and an outlet for the reaction gas and which can be sealed from the external atmosphere, and a support table which is disposed in the reaction chamber and supports the semiconductor substrate on which the resist is disposed. A thermal radiator disposed to face the support, an active oxygen generator disposed in the introduction part for generating active oxygen in the reaction gas, and a cooling device for cooling the semiconductor substrate via the support. The distance adjusting device for adjusting the mutual distance between the semiconductor substrate and the heat radiator, the radiant heat amount adjusting device for the heat radiator, or a combination thereof.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is a sectional view of an ashing device for a semiconductor device according to one embodiment of the present invention.

In FIG. 1, 31 is a reaction chamber, 32 is a wafer mounting table as a support, 33 is a gas introduction pipe as an introduction part, 34 is a mass flow controller, 35 is a gas exhaust pipe as an exhaust part, and 36 is variable. A valve, 37 is a cooling device as one of heat quantity adjusting means, 38 is a temperature sensor, 39
Is an active oxygen generator as a reaction gas activating means, 40
Is a wafer as a substrate or a semiconductor substrate, 41 is a resist, 42 is an infrared irradiating tube as a heat radiating means or a heat radiating body, 43 is a supporting portion of the infrared irradiating tube 42, 44 is a reflecting plate, and 45 is a heat shielding plate. is there.

The reaction chamber 31 is provided with a gas introduction pipe 33 for ashing gas as a reactive gas and a gas exhaust pipe 35 for exhausting exhaust gas, and a mass flow controller 34 and a variable valve 36 are provided respectively. An ashing source gas supply device (not shown) as a reaction gas is provided on the upstream side of the mass flow controller 34, and the ashing source gas is supplied by the mass flow controller 34 at a predetermined flow rate. As the ashing source gas, oxygen gas or a mixed gas of oxygen gas and an inert gas such as nitrogen or hydrogen gas is used in the oxygen plasma discharge method, and ozone generated by an ozone generator (not shown) is used in the optical ozone method. Supplied.

An active oxygen generator 39 is provided on the downstream side of the mass flow controller 34, that is, between the mass flow controller 34 and the reaction chamber 31. The ashing raw material gas supplied through the mass flow controller 34 passes through this active oxygen generator 39,
In the case of reduced-pressure oxygen gas, active oxygen is generated by microwave discharge, and in normal-pressure ozone, active oxygen is generated by irradiation of ultraviolet rays, and becomes ashing gas as a reactive gas and supplied to the reaction chamber 31.

Further, by controlling the gas flow rate by the mass flow controller 34 and the gas mixing ratio upstream of the mass flow controller 34, the reactive species in the reaction chamber can be increased or decreased to adjust the ashing rate. The reaction chamber 31 is further provided with a wafer supply unit (not shown) for supplying and taking out wafers. And reaction chamber 3
1 is configured so that it can be sealed from the external atmosphere.

A wafer mounting table 32 for supporting the wafer 40 on the upper surface thereof is provided inside the reaction chamber 31, and an infrared irradiation tube 42 is supported on the upper surface of the wafer mounting table 32 so as to face the upper surface of the wafer mounting table 32. It is supported by 43. The relative distance between the infrared irradiation tube 42 and the wafer mounting table 32 can be changed. This is because if the material of the wafer is Si or GaAs and the thermal conductivity and the specific heat are different, the temperature rise of the resist is different. This is because it can be changed easily. Further, it is possible to cope with a change in the amount of heat generated by the infrared irradiation tube 42 over time and a time lag of heat generation of the infrared irradiation tube 42.

The relative distance between the infrared irradiation tube 42 and the wafer mounting table 32 is adjusted by a distance adjusting device (not shown) as one of the heat quantity adjusting means. In the first embodiment, the infrared irradiation tube 42 is adjusted. It is adjusted by using a distance adjusting device in which the support portion 43 moves up and down. For this, the wafer mounting table 32 may be moved up and down, or both may be combined. The amount of radiant heat applied to the resist 41 can be adjusted by adjusting the relative distance between the infrared irradiation tube 42 and the wafer mounting table 32. The radiant heat amount is adjusted by a heat radiant amount adjusting device (not shown) as one of the heat amount adjusting means.
Alternatively, a method of controlling the amount of power input to the infrared irradiation tube 42 may be used.

Although not carried out in this embodiment, the wafer 40 and the infrared irradiation tube 42 may be rotated relative to each other as necessary so that the entire surface of the wafer 40 is uniformly exposed to the heat rays. Wafer 40 and infrared irradiation tube 4
One method of relative rotation with respect to 2 is to provide a mounting portion (not shown) for mounting the wafer 40 on the wafer mounting table 32, and to mount this mounting portion around the surface direction axis of the upper surface of the wafer mounting table 32. There is a way to rotate.

The relative rotation may be performed by rotating the infrared irradiation tube 42 around the surface direction axis of the upper surface of the wafer mounting table 32, or rotating the wafer mounting table 32 itself or the mounting portion.
In the reaction chamber 31, a reflection plate 44 having a mirror finish is provided so that infrared rays can be effectively emitted to the wafer 40. The material may be aluminum as a base material. The temperature sensor 38 is installed near the wafer 40, monitors the temperature near the wafer 40, controls the distance between the infrared irradiation tube 42 and the wafer mounting table 32, and
The amount of heat input to the infrared irradiation tube 42 is controlled to control the amount of heat radiated to the resist 41 so that the ashing is performed uniformly.

A vacuum suction device (not shown) is provided downstream of the gas exhaust pipe 35. Depending on the degree of opening and closing of the variable valve 36, the oxygen plasma discharge system can control the degree of vacuum in the reaction chamber. In the ozone method, the ashing gas supply rate can be controlled and the ashing rate can be controlled. The wafer mounting table 37 is provided with a cooling device 37. The cooling device 37 cools the upper surface of the wafer mounting table 37, and the wafer 40 mounted on the upper surface is cooled.
Of the resist 41 in contact with the wafer 40 is cooled. On the other hand, since the surface of the resist 41 is heated by the infrared irradiation tube 42, the temperature of the resist 41 on the surface facing the infrared irradiation tube 42 is high and the wafer 4
The surface in contact with 0 has a temperature gradient such that the temperature becomes low.

The cooling method is such that the cooling medium is circulated between the cooler body (not shown) and the wafer mounting table 32 so that the wafer mounting table 3 can be cooled.
2 is to be cooled. A heat shield plate 45 is disposed between the wafer mounting table 37 and the infrared irradiation tube 42. The heat shield plate 45 is made of a material having a low thermal conductivity such as ceramics, and is used when the wafer mounting table 3 is not ashed.
7 is to prevent heat from being radiated or transferred to the wafer 7. It is drawn out of the reaction chamber 31 at the time of ashing, covers the wafer 40 at the same time when the ashing is completed, and then the wafer 40 is taken out from the wafer supply section. The wafer 40 to be processed is supplied, mounted on the wafer mounting table 37, and then withdrawn from the reaction chamber 31 again.

By using this heat shield plate 45, it is possible to prevent excess heat from being transmitted to the cooling device 37 via the wafer mounting table 37, and to prevent the temperature drop inside the infrared irradiation tube 42 and the reaction chamber 31. The ashing can be performed after the rise time of the next ashing of the wafer 40 is shortened and the heat radiation is sufficiently saturated. FIG. 2 is a sectional view showing a state of the ashing device of FIG. 1 when the ashing is stopped. In FIG. 2, the infrared irradiating tube 42 is supported by a distance adjusting device (not shown) to a supporting portion 43.
Is lifted to the top, and the portion where the wafer mounting table 32 is disposed is shielded by the heat shield plate 45.

Next, the operation of the ashing device according to the present invention will be described. In FIGS. 1 and 2, first, a wafer 40 to be subjected to an ashing process is supplied to a wafer supply unit (not shown).
Supplied to the reaction chamber 31 and placed on the wafer mounting table 32,
After sealing the reaction chamber 31, the heat shield plate 45 is pulled out from the reaction chamber 31, and the infrared irradiation tube 42 is made to face the wafer 40. Then, the mass flow controller 34 and the variable valve 36 are adjusted so that the ashing gas in which the active oxygen is generated is allowed to flow into the reaction chamber 31 via the active oxygen generation device 39 to bring the reaction chamber 31 into a predetermined processing atmosphere.

On the other hand, the infrared irradiation tube 42, which has been pulled up to the uppermost part of the reaction chamber 31, is attached to the supporting portion 43 on the wafer mounting table 3.
Use the distance adjusting device with 2 to move up and down. Next, the infrared irradiation tube 42 is turned on to radiate heat to the resist 41 on the surface of the wafer 40, and while the temperature sensor 38 measures the temperature in the vicinity of the resist, the infrared irradiation tube 42 is moved up and down using a distance adjusting device to move the resist. A resist 41 containing, for example, a novolac resin as a main component is heated to a predetermined temperature from the surface of the resist 41.
Then, the resist 41 is heated to 60 ° C. or higher and 150 ° C. or lower, and preferably 60 ° C. or higher and 100 ° C. or lower.

The amount of heat applied to the resist is appropriately adjusted by preliminary adjustment before the reaction or adjustment during the reaction. At the same time, the cooling device 37 provided on the wafer mounting table 37 is operated to cool the back surface of the wafer 40 mounted on the upper surface of the wafer mounting table 37. Resist 41 heated to a predetermined temperature
Since the back surface of the wafer 40 is cooled, the surface thereof has the highest temperature and the surface thereof is in contact with the ashing gas. Therefore, the surface of the resist 41 reacts with the active oxygen of the ashing gas, and CO ₂ Decomposes into gases such as H ₂ O and H ₂ O. The gas after the reaction is sequentially exhausted from the reaction chamber 31 through the gas exhaust pipe 35 by adjusting the variable valve 36.

When the ashing is completed, the infrared irradiation tube 4
2 is turned off, the support part 43 pulls it up to the uppermost part of the reaction chamber 31, the mass flow controller 34 and the variable valve 36 are closed, the supply of ashing gas is stopped, the heat shield plate 45 is drawn into the reaction chamber 31, and the reaction is performed again. A portion of the chamber 31 where the infrared irradiation tube 42 is provided and a portion where the wafer mounting table 32 is provided are cut off from each other, and a wafer supply unit (not shown) is provided.
The wafer for which the ashing process has been completed is taken out from.

Next, an ashing method using this ashing device will be described. This ashing method is, for example, an aerial wiring by a selective plating method using a photoresist as a mask material when forming a connecting wiring of adjacent island-shaped electrode patterns or aerial wiring of a crossover wiring in a high frequency device such as a GaAs IC. The forming process will be described. Figure 3,
4, 5, 6, 7, 8 and 9 are sectional views of a wafer showing respective steps of an ashing method using the ashing apparatus according to the present invention.

First, a lower layer resist 51 as a first resist is applied on the main surface of the wafer 50. The resist used here has, for example, a novolac resin as a main component. Then, the lower layer resist 51 is patterned so as to remove the lower layer resist 51 of this portion in order to form a portion which becomes a pillar when the metal wiring is floated in the air to form an aerial wiring. FIG. 3 is a sectional view of the wafer at this stage of the process. Next, a metal thin film of gold or titanium to be the power supply layer 52 as a conductive thin film is formed on the entire surface of the wafer by vapor deposition or sputtering to a thickness of about 500Å. FIG. 4 is a sectional view of the wafer at this stage of the process.

Next, an upper layer resist 53 as a second resist is applied on the power feeding layer 52, and is patterned so as to expose the power feeding layer 52 in the portion where the aerial wiring is formed.
FIG. 5 is a sectional view of the wafer at this stage of the process. After that, utilizing the fact that the plating layer selectively grows on the exposed portion of the power supply layer 52 having no resist, the upper metal wiring 54 having a thickness of about 3 μm is formed on the exposed portion of the power supply layer 52 by the selective plating method. To form.

In electrolytic plating used for forming aerial wiring of GaAs IC, an external electric field is applied to a metal salt solution to electrolyze the solution and reduce and deposit a predetermined metal on the surface of an object used as a cathode. It is a film forming method. After this, ashing processing is performed, and the arrow in FIG. 6 indicates the direction of heat radiation from the infrared irradiation tube 42.

Since the ashing device according to the present invention is used for this ashing process, in FIG. 1, the infrared irradiation tube 42 is moved by the distance adjusting device while the temperature near the resist is measured by the temperature sensor 38. Since the upper layer resist 53 of FIG. 6 is finely adjusted up and down and heated from its surface to a predetermined appropriate reaction temperature, variations in the resist temperature during ashing can be reduced. Therefore, it is possible to prevent the wafer from being overheated and prevent the reliability of the semiconductor device from being deteriorated due to the scorching of the resin of the resist.

Further, as shown in FIG. 1, the cooling device 37 is simultaneously installed.
6 is operated to cool the back surface of the wafer 40 mounted on the upper surface of the wafer mounting table 37, the upper layer resist 53 in FIG. The surface of the upper resist layer 51 that has contact with the wafer 40 has a temperature gradient such that the temperature becomes low, and the surface of the upper resist layer 53 reacts most actively with the active oxygen of the ashing gas. Since the lower layer resist 51 does not increase in temperature so much while being decomposed into gas such as CO ₂ and H ₂ O,
Even if the lower layer resist 51 is entirely covered by the power feeding layer 52, the lower layer resist 51 may be deformed or the lower layer resist 5 may be covered.
No abnormal expansion of the vaporized material contained in No. 1 occurs, and the power feeding layer 52 does not deform or burst. 6 is a sectional view of the wafer at the stage of this step, and FIG. 7 is a sectional view of the wafer at the stage when the ashing process of the upper layer resist 53 is completed.

The upper layer resist 53 can be removed by a wet method using a solvent such as acetone, but in the wet method, the solvent enters the lower layer resist 51 due to cracks in the power feeding layer 52 or defects such as pinholes, and the lower layer resist 53 is removed. Expand the resist 51,
Since it may dissolve and cause troubles, the dry process by ashing is preferable to the process by the wet method. After that, the power supply layer 52 exposed by removing the upper resist 53 is removed by the ion milling method if the power supply layer 52 is gold, or by RIE or the like if it is Ti, to remove the unnecessary power supply layer 52. FIG. 8 is a sectional view of the wafer at this stage of the process.

Further, after removing the power feeding layer 52, the lower layer resist 51 is removed with a solvent such as acetone to obtain the power feeding layer 5.
2 and the upper metal wiring 54 are floated in the air, and the overhead wiring 55
And As described above, in the ashing device shown in this embodiment, since the relative distance between the infrared irradiation tube 42 and the wafer mounting table 32 can be changed, for example, the material of the wafer may be Si or GaAs. Therefore, even if the thermal conductivity and the specific heat are different, the amount of radiant heat applied to the resist to bring the temperature of the resist to a predetermined temperature can be easily and finely adjusted.

Since the upper surface of the wafer mounting table 32 is cooled by the cooling device 37, the back surface of the wafer 40 mounted on the upper surface is cooled and the resist 41 in contact with the wafer 40 is cooled. You can On the other hand, since the surface of the resist 41 is heated by the infrared irradiation tube 42, the temperature of the resist 41 is high on the surface facing the infrared irradiation tube 42 and low on the surface in contact with the wafer 40. Will have a gradient. Therefore, the surface of the resist 41 has the highest temperature and the surface is in contact with the ashing gas.
0 and the inside of the resist 41 are not thermally damaged, and the surface of the resist 41 actively reacts with the active oxygen of the ashing gas to efficiently decompose the resist 41.

Further, the wafer mounting table 37 and the infrared irradiation tube 42
Since the heat shield plate 45 is disposed between the heat shield plate 45 and the heat shield plate 45, it is possible to separate the cooled region on which the wafer mounting table 37 is arranged and the region on which the infrared irradiation tube 42 is arranged, when ashing is not performed. , Preventing excess heat from being transferred to the cooling device 37 via the wafer mounting table 37, preventing the temperature of the infrared irradiation tube 42 and the inside of the reaction chamber 31 from decreasing, and starting the next wafer 40 during ashing. It is possible to shorten the time and sufficiently saturate the heat radiation before performing the ashing.

Further, in the ashing method using the ashing apparatus shown in this embodiment, the surface of the resist 41 has the highest temperature and the surface is in contact with the ashing gas. The resist 41 can be efficiently decomposed without being thermally damaged, and deterioration of the electrical characteristics of the semiconductor device can be prevented.

For example, in the case of a GaAs IC, it is known that the Schottky junction between Au and GaAs deteriorates the Schottky characteristics due to thermal diffusion of Au and GaAs at a relatively low heat treatment temperature. Since the ashing method according to (1) can suppress the wafer temperature to a low level, it is possible to prevent the gate-drain breakdown voltage from being lowered due to the deterioration of the Schottky characteristics.

Similarly, in the ohmic junction, the contact resistance is lowered if an appropriate heat treatment is carried out, for example, at 350 ° C. for several minutes, but if the heat treatment time is too long or the heat treatment temperature is too high, the contact resistance is lowered. Although the resistance rather increases, the ashing method according to the present invention can prevent an increase in ohmic resistance. As described above, in the ashing method according to the present invention, it is possible to eliminate the cause of the variation in the electrical characteristics of the semiconductor device due to the ashing.
A semiconductor device with high reliability and high yield can be manufactured.

[0053]

The ashing method for a semiconductor device and the ashing apparatus used for the same according to the present invention have the following steps or configurations, and therefore have the following effects.

In the ashing method for a semiconductor device according to the present invention, the resist is heated by the heat radiating means provided so as to face the support for supporting the substrate, and the resist is heated so that the temperature of the resist surface becomes higher than that of the substrate. Since the step of appropriately adjusting the amount of heat applied is provided, the resist can be heated from its surface to a predetermined appropriate reaction temperature, so that the variation in the resist temperature during ashing is reduced, and It is possible to prevent overheating, and it is possible to prevent deterioration of reliability of the semiconductor device due to scorching of resin in the resist.

Further, the step of appropriately adjusting the amount of heat includes a distance adjusting step of changing the mutual distance between the heat radiating means and the substrate supported by the support, a heat radiating amount adjusting step of the heat radiating means, or a cooling for cooling the substrate. Since any one of these steps or a combination of these steps is included, it is possible to finely adjust the temperature by a simple step, prevent overheating of the semiconductor device, and prevent deterioration of reliability of the semiconductor device due to scorching of resist resin. it can.

Further, the resist is heated by the heat radiating means provided so as to face the support base for supporting the semiconductor substrate, the semiconductor substrate is cooled, and the heat radiator and the semiconductor substrate supported by the support base are provided. Since the step of adjusting the amount of heat applied to the resist by adjusting the distance for changing the mutual distance or adjusting the radiant heat amount of the thermal radiator or a combination thereof, the resist is the surface facing the thermal radiator. Has a high temperature, and the surface of the resist that is in contact with the semiconductor substrate has a temperature gradient such that the temperature is low, and the surface of the resist actively reacts with the active oxygen of the ashing gas. The temperature does not rise, and the inside of the resist does not deform and the vaporized substance contained in the resist does not expand abnormally. Therefore, it is possible to efficiently decompose the resist and prevent the reliability of the semiconductor device from being lowered due to heating.

Further, a semiconductor substrate in which the first resist, the conductive thin film and the second resist are sequentially arranged on the main surface is supported by a supporting base, and the heat radiator is arranged so as to face the supporting base. Heats the second resist to cool the semiconductor substrate so that the temperature of the surface of the second resist is higher than that of the semiconductor substrate, and the mutual distance between the heat radiator and the semiconductor substrate supported by the support base is increased. Since the step of appropriately adjusting the amount of heat applied to the second resist by adjusting the distance for changing the temperature, adjusting the amount of radiated heat of the thermal radiator, or a combination thereof is used, The temperature is lower than that of the resist, and it is possible to prevent deformation inside the resist and abnormal expansion of vaporized substances contained in the resist. It can be stopped.

Further, the ashing apparatus according to the present invention provides the heat radiating means arranged so as to face the support table for supporting the substrate and the amount of heat applied to the resist so that the temperature of the resist surface becomes higher than that of the substrate. Since the heat quantity adjusting means for adjusting is provided, the resist can be heated from the resist surface to a predetermined appropriate reaction temperature, so that the variation in the resist temperature at the time of ashing is reduced, and the semiconductor device can be prevented from being overheated. Therefore, a highly reliable semiconductor device can be manufactured.

Further, the heat quantity adjusting means may be a distance adjusting device for changing the mutual distance between the heat radiating means and the substrate supported by the support or a heat radiating quantity adjusting device of the heat radiating means or a cooling device for cooling the substrate. Since any one or a combination thereof is included, an ashing device that can manufacture a highly reliable semiconductor device can be configured at low cost.

Further, the heat radiator arranged to face the support base for supporting the semiconductor substrate, the cooling device for cooling the semiconductor substrate via the support base, and the mutual distance between the semiconductor substrate and the heat radiator. Since it is provided with a distance adjusting device for adjusting the heat radiation amount or a radiation heat amount adjusting device for the heat radiator or a combination thereof, it is possible to heat the resist from the resist surface to a predetermined appropriate reaction temperature and cool the semiconductor substrate, Since it is possible to efficiently decompose the surface of the resist and prevent the inside of the resist from deforming and the vaporization contained in the resist to expand, the resist can be decomposed with high efficiency and a highly reliable semiconductor device can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an ashing device for a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing a state of the ashing device of FIG. 1 when ashing is stopped.

FIG. 3 is a sectional view of a wafer showing a step of the ashing method according to the present invention.

FIG. 4 is a sectional view of a wafer showing one step of the ashing method according to the present invention.

FIG. 5 is a sectional view of a wafer showing a step of the ashing method according to the present invention.

FIG. 6 is a sectional view of a wafer showing a step of the ashing method according to the present invention.

FIG. 7 is a sectional view of a wafer showing a step of the ashing method according to the present invention.

FIG. 8 is a sectional view of a wafer showing one step of the ashing method according to the present invention.

FIG. 9 is a sectional view of a wafer showing a step of the ashing method according to the present invention.

FIG. 10 is a sectional view of a conventional ashing device.

FIG. 11 is a cross-sectional view of a semiconductor device showing a step in a process of forming an aerial wiring according to a conventional device.

FIG. 12 is a cross-sectional view of a semiconductor device showing a defect caused by formation of aerial wiring according to a conventional device.

[Explanation of symbols]

31 reaction chamber, 33 gas introduction pipe, 35 gas exhaust pipe, 32 wafer mounting table, 42 infrared irradiation pipe, 37 cooling device, 39 active oxygen generation device, 41 resist, 40 wafer, 51
Lower layer resist, 52 Feed layer, 53 Upper layer resist

Claims (7)

[Claims] 1. A first step of supporting a substrate provided with a resist on a support table provided in a reaction chamber capable of being sealed from an external atmosphere, and a reactive gas which reacts with the resist in the reaction chamber. Second to introduce
And the third step in which the resist is heated by the heat radiating means arranged so as to face the support, and the resist reacts with the reactive gas, so that the temperature on the resist surface becomes higher than that on the substrate. And a fourth step of properly adjusting the amount of heat applied to the resist. 2. A fourth step is a distance adjusting step of changing a mutual distance between the heat radiating means and the substrate supported by the support, a heat radiating amount adjusting step of the heat radiating means, or a cooling step of cooling the substrate. 2. The method for ashing a semiconductor device according to claim 1, wherein any one of them or a combination thereof is included. 3. A first step of supporting a semiconductor substrate on which a resist is arranged on a support table arranged in a reaction chamber capable of being sealed from an external atmosphere, and a reaction containing reactive oxygen in the reaction chamber. A second step of introducing a gas, a third step of heating the resist by a heat radiator disposed so as to face the supporting base, and reacting the resist with active oxygen, and a resist surface rather than a semiconductor substrate. The semiconductor substrate is cooled so that the temperature becomes higher, and the distance between the thermal radiator and the semiconductor substrate supported by the support is changed, or the distance is adjusted, or the radiant heat of the thermal radiator is adjusted, or a combination thereof. And a fourth step of appropriately adjusting the amount of heat applied to the resist by the method described above. 4. A semiconductor substrate in which a first resist, a conductive thin film, and a second resist are sequentially arranged on a main surface of a support table arranged in a reaction chamber capable of being sealed from an external atmosphere. The first step of supporting, the second step of introducing a reactive gas containing active oxygen into the reaction chamber, and the second resist is heated by the heat radiator disposed so as to face the support base, The third step of reacting the resist with the active oxygen of No. 2 and cooling of the semiconductor substrate so that the temperature of the second resist surface is higher than that of the semiconductor substrate, and the semiconductor substrate was supported by the heat radiator and the support base. A fourth step of appropriately adjusting the amount of heat applied to the second resist by adjusting the distance for changing the mutual distance with the semiconductor substrate, adjusting the amount of radiated heat of the thermal radiator, or a combination thereof. Equipment ashing method. 5. A reaction chamber which has an inlet and an outlet for a reaction gas and which can be sealed from an external atmosphere, and a support table disposed in the reaction chamber for supporting a substrate on which a resist is disposed, A heat radiating means arranged so as to face the support base, a heat quantity adjusting means for adjusting the quantity of heat applied to the resist so that the temperature of the resist surface is higher than that of the substrate, and a heat radiating means arranged in the introducing section. An ashing device comprising a reactive gas activating means for forming active species in the reactive gas. 6. A distance adjusting device for changing the mutual distance between the heat radiating means and the substrate supported by the support, a heat radiating amount adjusting device for the heat radiating means, or a cooling device for cooling the substrate. The ashing device according to claim 5, comprising any one or a combination thereof. 7. A reaction chamber having an inlet and an outlet for a reaction gas and capable of being sealed from an external atmosphere, and a support base disposed in the reaction chamber for supporting a semiconductor substrate on which a resist is disposed. A heat radiator disposed opposite to the support base, an active oxygen generator disposed in the introduction part for generating active oxygen in the reaction gas, and cooling the semiconductor substrate via the support base. An ashing device comprising: a cooling device for controlling the heat radiation device;