JPS62290134A - Apparatus for removing photoresist - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION 3. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method and apparatus for stripping photoresist, and more particularly to a method and apparatus that provides rapid stripping times.

Photolithographic techniques are frequently used in the fabrication of integrated circuits. In practicing this technique, a semiconductor wafer is coated with a photoresist, which is then exposed to ultraviolet light through a mask, thus imaging the desired pattern onto the photoresist. This changes the solubility of the exposed areas of the photoresist and thus, after development in a suitable solvent, the desired pattern is fixed on the wafer'2 and the photoresist is then hard baked and subjected to subsequent processing. to withstand.

In such subsequent processing, components of the integrated circuit corresponding to the desired pattern are removed by plasma etching or ion implementation.
n).

After the integrated circuit components are formed, the photoresist is stripped (srtrip) from the wafer in step 9!
Indeed, the wafer has already served its useful purpose at this point, and whether the photoresist 211# is relatively easy or difficult to etch, certain plasma etching or ion implantation steps are required.
lantation) and the extent to which the photoresist is crosslinked. Thus, to a significant extent, hard baking and even to a large extent, plasma etching and ion-carrying methods incur physical and chemical changes in the photoresist! A# is known to be particularly difficult.

In the prior art, the most common techniques that have been used for 2rI polishing of photoresists are the use of wet solvent developers, such as sulfuric acid-hydrogen peroxide solutions, and plasma iodization techniques. However, these have not been shown to be entirely satisfactory because the work using solvent developers is difficult and dangerous;
and tended to cause surface contamination, while plasma iodization was characteristically excessive and sometimes caused electrical damage to the wafer.

Another technique for releasing photoresists consists of exposing the photoresist to an ozone-containing atmosphere and simultaneously heating the support having the photoresist layer disposed thereon. This method is disclosed in US Pat. No. 4,431,592, in which ozone is transported across the photoresist in a reaction chamber while the support is heated to a temperature not exceeding 260°C.

Related technology: “Ultraviolet-ozone (ultravio 1
et-ozone) J, in which
The photoresist, which is a hydrocarbon-containing material, is exposed to ozone and simultaneously irradiated with ultraviolet radiation containing spectral components below 300 nm. The combination of ultraviolet light and ozone causes oxidation of the photoresist, thereby converting the photoresist to volatile by-products, thereby 'AS'. Additionally, the support supporting the photoresist layer can be heated in combination with UV-ozone methods, although temperatures above 250-300° C. have not been utilized in the prior art.

of the ozone and UV-ozone photoresists mentioned above.
A-separation technology initially showed promise. That is, they are cleaner and more convenient to work with, and are less prone to problems related to surface contamination and electrical damage than prior art methods. However, these techniques have not gained significant commercial acceptance to date.

This is because, as currently practiced, they are too slow for most photoresists and may not even be able to separate highly ion-implanted photoresists by 2q.

It has been recognized in the prior art that 'A# can be advanced by heating the support and simultaneously exposing the surface of the photoresist to ozone or to ozone and UV. However, the prior art does not disclose the use of support temperatures above 300°C, typically above 260°C. The reason why higher temperatures have not been used in the past is that higher temperatures are used with times comparable to the prior art's hatching times.

It is believed that this can lead to device damage, eg, diffusion between layers of a built-in circuit.

According to Kiwasu 1, it was recognized that the substrate could be exposed to such high temperatures if heating significantly above 300° C. was carried out for only a short sowing period. To accomplish this, means are employed to form a narrow gap of less than 2 mm in thickness adjacent to the photoresist; producing flow velocities in the range of 2 to 600 cm/see within the sheath, gear, or tube. By supplying an oxidizing fluid into such a gap at a high flow rate and utilizing a support temperature of over 300°C, the photoresist can be formed in such a reasonably short time! A#;, will be done. Therefore, by practicing the present invention, very short stripping times are achieved and difficult to strip photoresists, such as ion-implanted photoresists, can be removed within a commercially acceptable time, i.e. It is exfoliated in less than a minute, more typically within 1 to 3 minutes.

In a preferred embodiment of the invention, the narrow gap is created by placing a quartz plate at a short distance above the photoresist. When using additional UV radiation, a thin layer of oxidizing corrugations bounded by a quartz plate minimizes the absorption of UV radiation, and a high irradiance layer that can be located at a certain distance from the photoresist The use of an ultraviolet source is 11 times.

In the practice of the present invention, the combination of ozone used as the oxidizing fluid and a high velocity of ozone through a narrow gap at a support temperature above j00° C. results in a faster A# generates time. Further improvements can be obtained in which the photoresist is additionally irradiated with ultraviolet radiation having a significant spectral content below 300 nm. Furthermore, the combination of heating the support above 300° C. and simultaneous irradiation with ultraviolet radiation at an irradiance above about 800 mW/cm 2 improves the exfoliation rate even in the absence of the aforementioned narrow gap. .

Thus, it is an object of the present invention to rapidly convert photoresist to 2I
An object of the present invention is to provide a method and apparatus for Ig&.

Another object of the present invention is to provide a method and apparatus that is particularly effective in stripping photoresists that are difficult to strip, such as ion-implanted photoresists.

Yet another object of the present invention is to provide a more rapid stripping technique using an oxidizing fluid, but with its attendant advantages, than that provided by the prior art.

Yet another object of the invention uses a high irradiance focused UV source that must be spaced from the photoresist! It is to use A-techniques.

The invention will be further described with reference to the accompanying drawings.

Referring to FIG. 1, the photoresist 6 to be stripped is
It is coated onto a support, for example a silicon wafer, which is then placed on the chuck 2.

In this embodiment, ozone is used as the oxidizing fluid and pure oxygen is supplied to the ozone generator 18 to generate ozone. This ozone generator 1
8 can be of the silent discharge type.
in Techniques Corp.)
A 0.5C ozone generator is suitable.

Ozone is supplied from conduit 10 to the IK area directly above photoresist 6 through an opening in gap space element 20 . A gap space element 20 is used to create a narrow gap above the photoresist through which ozone is flowed in a thin layer. In the preferred implementation IE,
Element 20 is a slab of quartz. This plate must be constructed from a material that does not degrade upon exposure to ozone and does not cause ozone to decompose too quickly. It would be reasonable to use materials other than quartz, as long as they have the same properties.

Plate 20 is spaced no more than 2 mm from the photoresist, with the preferred spacing for many photoresists being about 0.0 mm.
It is 5mm. The plate is mounted in the correct distance from the photoresist by means of a transparent mounting L stage, e.g. by suitable spacers, and preferably the plate and chuck are in the form of a circular disc, with semiconductor plates spaced 2q apart. Match the shape of the wafer.

According to the present invention, ozone is supplied to the narrow gap between the photoresist and the plate at a flow rate sufficient to produce a flow rate in the gap that falls within the range of 2 to 600 cm/SeC. A narrow gap facilitates achieving such high speeds. In the embodiment of FIG. 1, a gap space element with a single central fluid opening is used, with a rate of 2 to 5 standard cubic feet per hour (SCFH).
c/) flow velocity yields a velocity of 2-6000 m/sec. The speed is approximately 20c outside the photoresist being stripped.
m/see. Ozone on the outside not only flows, but is also more polluted than near the center +1, and when using other embodiments, such as the embodiment of FIG. and where the ozone can be fed at a slow rate. In a preferred embodiment, ozone is used at a concentration of 4% in oxygen.

The oxidizing fluid is withdrawn from the area above the photoresist by exhaust supply conduits 32 and 34, which conduits are directed to a neutralization device or alternatively.

For example, it is emitted into the atmosphere by chimneys.

The chuck 2 is hollow and constructed of a good thermal conductor, for example aluminum. An electrically resistive heater 24 is located inside the chuck and is arranged to preheat the wafer before exposure to ozone.
It is heated to a temperature above 0° C. to achieve rapid exfoliation.

The high velocity flow through the narrow gap continuously exposes the photoresist to fresh ozone, thus recombining the ozone! Minimize jeg.

In a preferred embodiment, ozone is used as the oxidizing fluid; other known oxidizing fluids can be used. With more active oxidizing fluids, it is believed that temperatures above 300°C will provide suitable results, and heating may be omitted. Also, at an ozone concentration of 4% or more, heating can be reduced.

Excessive flow rates in narrow gaps can cool the photoresist, which inhibits the 2IIs, with the northern limit of flow rate depending on the photoresist used as well as other process variables.

Referring to FIG. 2, another embodiment of the invention is shown, in which like numerals indicate identical parts to that shown in FIG. The embodiment of FIG. 2 is identical to FIG. 1 except that the photoresist is irradiated with ultraviolet radiation having a significant spectral content as low as 300 nm and simultaneously exposed to ozone and heat. Exposure to UV can improve the stripping time, especially at wider gap widths reaching 2 mm.

In Figure 2, illumination is provided by source 30, and the irradiance provided by this source should be at least 800 watts/cm2.

The use of a thin ozone layer in accordance with the present invention minimizes UV absorption and necessitates the use of highly powered, focused, electrodeless sources that must be separated from the photoresist for mechanical reasons. , so that a photoresist can be placed in the focal plane of the source to obtain the desired irradiance. Typically, a microwave powered electrodeless light source will be used to obtain the necessary irradiance.

A light source that was found to have particularly good performance was the M150.
PC type Irradiator [Fusio system
n Systems C.

rp, )]. This source uses a spherical bulb and a segmented flefter and was published in 1985, 3 J.
- Utilizes the principles described in Co-pending Application No. 707.159 filed by JID to provide substantially uniform illumination on the wafer. Additionally, for the present invention, the mesh 30 is located below and 5° outward from vertical.
It has been discovered that a retaining ring of reflective material that is sloped at can still increase uniformity.

The preferred spectrum for the ultraviolet light source is shown in Figure 11, and it is observed that there is a significant spectral component below 300 nm. The exemplified spectrum has been found to work particularly well, although other specific spectra including short UV wavelengths below 300 nm also work advantageously.

In the implementation IE of Figures 1 and 2, after performing the stripping, the chuck is rapidly cooled to keep the wafer at high temperature for as short a time as possible to avoid damage to the wafer, and It is desirable to facilitate the wafer transfer operation. One way to achieve cooling is to pass a coolant, such as deionized wood, through a wave channel (not shown) within the chuck. This is a continuous wave path, and in FIG. 1 the cooling liquid is supplied via conduit 14 and discharged via conduit 16, since the cooling is by conduction and the chuck is constructed of a good conductor. , rapidly achieved.

In the practice of the present invention, the wafer is heated to a temperature of 300°C or higher.
If possible, heat to a temperature of 350°C or higher. In embodiments utilizing UV radiation, the UV irradiance of the source is increased to 800 milliwatts/cm2, significantly higher than 2 watts/cm2.
Increasing above cm 2 allows the stripping time to be reduced, thus allowing the use of higher substrate temperatures without damaging the device. The upper limit on support temperature is created by the chemical properties of ozone, which recombines at high temperatures.

Next, examples will explain how to implement the present invention. In the examples, the apparatus of FIGS. 1 and 2 was used.

Example ■ Ion-grafted and UV baked, 1.5 thick
Micron Shipley 1400 Series 7* resist was stripped.

The wafer was heated to 330°C and the wafer reached a peak temperature of 331°C during 'A separation. A gas mixture containing 4% ozone in oxygen was fed into a 0.5 mm wide narrow gap above the photoresist at a flow rate of 43 CFH.

The photoresist was 2qS at 98% in 3 minutes over a 4 inch diameter.

Example ■ Highly ion-grafted 1.5 micron thick Shipley 1400 series (S et
ie s) The photoresist was stripped.

The wafer was preheated to 320°C. 3 in oxygen
A gas mixture containing % to 4% ozone is applied from the photoresist to a narrow gap of 2 mm or less at -L for 3 to 4 S.
CFH flow rate and photoresist exposed to ultraviolet radiation (200-420 nm) approximately 1450 mW/
Exposure was made at 11 degrees between radiations of Cm2.

The photoresist was completely stripped in 2.5 minutes.

Example m A 1 micron thick piece of PMMA was hard baked.

The wafer was preheated to 320°C. 3% in oxygen
A gas mixture containing ~4% ozone is applied to a narrow gap of 2 mm or more F below the photoresist at -L 3-43
A flow rate of CFH was applied and the photoresist was exposed to ultraviolet radiation at an irradiance of approximately 1450 milliwatts/cm2.

The photoresist was completely cured in 30-45 seconds.

It should be recognized that in an actual process line the implementation of the present invention may be automated. In this way, 2
The wafer to be q#ed will be automatically transferred to a chuck where it will be heated to a predetermined temperature and exposed to an oxidizing fluid.

Furthermore, although the embodiment illustrated in FIG. 1 shows a quartz plate 20 having a centrally located width supply 1 or opening
Other arrangements are possible and may be more desirable.

In this regard, it is desirable to provide a layer of oxidizing fluid of uniform thickness, which has a uniform flow rate and is not contaminated with constituents produced by chemical reactions, such as carbon dioxide and water vapor.

Thus, in the implementation shown in Figure 2, the ozone layer tends to be dilute as it flows from the center of the quartz plate to the periphery, and the directional flow velocity becomes lower and the ozone becomes contaminated with carbon dioxide and water vapor. There is a tendency to

Referring to FIG. 3, an embodiment is shown in which the quartz plate 40 has a plurality of openings 42, 44, 46 and 48. This arrangement creates a more uniform thickness of the ozone layer. Flow rates form, and overall and local contamination of oxidizing fluids is low.

However, there may be a Hull area between the mouths, for example in the area indicated by reference numeral 50 in FIG.

These null areas can be compensated to a significant degree by rotating the photoresist. FIG. 4 shows an embodiment in which the chuck 56 is rotated by a motor 58. In such embodiments, a slip joint is provided to transport the fluid in a rotational manner;
A slip ring, on the other hand, will transport current.

A lip-fed embodiment is shown in FIG. 5, where the quartz plate 60 is rectangular and the oxidizing fluid is fed inside the baffle plate 70 by a conduit 68. It exists along the edge of the plate 60. A conduit 68 extends into the top surface of the paper and includes a longitudinal aperture along the conduit, into which the oxidizing fluid is supplied and through the aperture therein is connected to the quartz plate 60. The photoresist on the wafer 62 is applied to the gap between the photoresist and the photoresist.

Although the density and flow rate of the oxidizing fluid in the edge flow implementation 71% of FIG. 5 tends to be very uniform, the fluid tends to become contaminated due to the relatively large distance it traverses.

This can be compensated for by rotating the photoresist, and FIG. 6 shows a motor 72 rotating the chuck 64°.

In FIGS. 7 and 8, an implementation is shown that utilizes a modern quartz conduit to supply the oxidizing wave. Thus, fluid conduits 80 and 82 are connected to quartz plate 74.
The -direction fluid flow is indicated by arrows in FIG.

Another embodiment is shown in FIG. 9, in which alternating quartz conduits integrally formed with the quartz plates supply fluid, while conduits between the alternating conduits are formed with quartz plates and photoreceptors. Drain the fluid from the area between the resists. Evacuation of the fluid after it has traveled only a short distance results in relatively low contamination.

the possibility of nulls and shadows caused by quartz conduits (
In order to avoid shadowing),
It may be desirable to rotate the photoresist in the embodiments of FIGS.

It is recognized that similar results can be obtained by vibrating the chuck instead of rotating the chuck in the embodiment described above.

Referring to FIG. 1O, another embodiment is shown,
Here, the fluid restraint member 102 is tapered to reduce the incoming velocity and increase the outward velocity, thus counteracting fluid dilution and contamination.

Apparatus and method for achieving rapid stripping of photoresist
: was written.

Although U.S. Pat. "Fluids" include ozone, oxygen, chlorine,
It is to be understood to include substances including fluorine, iodine and hydrogen peroxide.

Also, as mentioned above, the articles "ultraviolet radiation" and "ultraviolet light" should be understood to mean radiation in the range 200-420 nm.

Although the invention has been described in connection with photoresist stripping, it can be used generally in the removal of organic materials.

Additionally, pending IJI is an exemplary and egregious actual kfL
However, modifications within the scope of the invention will be apparent to those skilled in the art, and the unreleased patent 1 is patent +? 1
It should be understood that it is limited only by the range of unity and its quantum.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of one embodiment of the invention. FIG. 2 is a schematic illustration of another embodiment of the present invention; FIGS. Figures 6 and 6 illustrate implementation 7 of the present invention utilizing gap space elements supplied with oxidizing fluid from the edge of the plate.
Shows Mr. g. 7 and 8 illustrate an embodiment of the invention that utilizes a gap space element having a plurality of flexible conduits associated therewith with which oxidizing fluid is supplied. FIG. 9 shows an embodiment utilizing a gap space element having conduits associated therewith, where alternating conduits supply oxidizing fluid and conduits between alternating conduits discharge oxidizing fluid. do. FIG. 1O shows an embodiment of the invention that utilizes a tapered gap space element. FIG. 11 is a representation of a preferred ultraviolet spectrum that the light source can be used with. 2 Chuck 2' Chuck 6 Photoresist to J tube 10' Conduit 14 Conduit 14' Conduit 16 Conduit 16' Conduit 18 Ozone generator 18' Ozone generator 20 Gap space element, quartz plate 20° Gap space element, quartz plate 24 Heater 30 source 32 Exhaust supply conduit 32'' Exhaust supply conduit 34 Exhaust supply conduit 34° Exhaust supply conduit 40 Quartz plate 42 Opening 44 Opening 46 Opening 48 Opening 50 Null area 56 Chuck 58 Motor 60 Quartz plate 60゛ Quartz plate 62 Wafer 62° Wafer 64 Chuck 64° Chuck 68 Conduit 68° Conduit 70 Deflector 72 Motor 70° Deflector 74 Quartz plate 80 Conduit 82 Conduit 102 Fluid restriction member 4'?, iHI [Person Fusion Systems Corporation Representative Patent attorney Small In Shima Heikichi FIG, 3 FIo 7 FIG, 87′°
Meto/πm Procedural correction words and actions) % formula % 1. Indication of the case 1985 Patent Application No. 169G58 2. Name of the invention Photorenost peeling device 3. Relationship with the M-correction case Patent applicant name Name 7. Ban Systems Corporation 4, Agent 107-5, Date of amendment order None 6, Patent applicant column of the application subject to amendment, power of attorney and its translation, drawing 7, Contents of amendment (No change in content)

Claims (1)

[Scope of Claims] 1. An apparatus for rapidly stripping a photoresist layer from a support composed of different materials having a photoresist layer disposed thereon, the apparatus comprising: means for creating a narrow gap, no more than 2 mm wide, adjacent said photoresist layer bounded by a disposed surface; and means for supplying an oxidizing fluid to said narrow gap, thereby reducing said narrow gap. means for creating a flow of oxidizing fluid past the photoresist within the photoresist. 2. The apparatus of claim 1, wherein the photoresist is heated to a temperature above 300° C. for only a brief period of time necessary to effectuate stripping. 3. The apparatus of claim 2, wherein said oxidizing fluid obtains a flow velocity within said narrow gap within the range of 2 to 600 cm/sec. 4. The apparatus according to claim 3, wherein the flow rate is within a range of 20 to 500 cm/sec. 5. The apparatus according to claim 4, wherein the oxidizing fluid is a gaseous medium containing ozone. 6. Photoresist layer at least 800 mW/
5. The method of claim 5, further comprising means for exposing to ultraviolet radiation with an irradiance of cm^2, during said exposure said photoresist is heated and said oxidizing fluid is transferred over said photoresist layer. The device described. 7. The device of claim 1, wherein the narrow gap is less than 0.6 mm. 8. The apparatus of claim 2, wherein said means for creating a narrow gap is a plate adjacent to the photoresist and having a single central fluid supply opening. 9. The apparatus of claim 2, wherein said means for creating a narrow gap is a plate having a plurality of openings. 10. The means for creating a narrow gap includes a flat surface and has a straight edge, and the fluid is supplied along the edge to an area between the flat surface and the photoresist. An apparatus according to claim 2. 11. The apparatus of claim 2, wherein the flat surface is part of said means for creating a narrow gap, and said flat surface includes a plurality of parallel conduit means. 12. Each of said conduit means has an opening extending along the length of said conduit means, and alternating conduit means provide means for supplying said fluid to the space between said planar surface and said photoresist. 12. The apparatus of claim 11, wherein the conduit means arranged between said alternating conduit means constitute means for discharging fluid from said space. 13. Claim 2 in which the photoresist is rotated
Apparatus described in section. 14. The apparatus of claim 3, wherein said means for creating a narrow gap includes a tapered member, said member creating a wide gap near the center and a narrow gap near the outside. . 15. An apparatus for rapidly stripping a photoresist layer from a support composed of a different material having a photoresist layer disposed thereon, the means for heating said support to a temperature of 300° C. or higher; means for simultaneously exposing the resist layer to the oxidizing fluid and exposing it to ultraviolet radiation at an irradiance of at least about 800 milliwatts/cm^2;
C. or higher for only a relatively short period of time necessary for the combination of the relatively high temperature and the relatively high exposure intensity of ultraviolet radiation to strip the photoresist;
An apparatus characterized in that it comprises means for avoiding damage to said support due to excessive heating.