JPS61265819A - Method and apparatus for dry processing of substrate - 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 Field of the Invention This invention relates to a method and apparatus for dry assembly of devices from substrates. In particular, the substrate contains an effluent of a gaseous plasma having at least one reactive species but virtually free of charged particles.
nt) and simultaneously irradiated with ultraviolet light to increase the reaction rate in a controlled manner.

PRIOR ART AND ITS PROBLEMS The use of gas plasmas for the fabrication of solid state devices is known in the prior art. Plasmas are used to etch (hereinafter simply referred to as etch) semiconductor substrates, and they can also be used to strip or remove photoresist layers from substrates.

Plasma treatment is dry treatment or RIE (reactive treatment).
Ion etching (also known as reactive ion etching) has distinct advantages over many conventional processes known as chemical or wet processes. Wet processing typically uses toxic compositions to remove photoresist from a substrate or corrode layers of material. Certain chemical compositions must be used with caution.

May be dangerous to the operator and the environment. Waste dumping associated with wet corrosion processes can also be a problem.

Wet corrosion is isotropic in that corrosion progresses at virtually the same rate in all directions, thereby causing corrosion to extend laterally as well as downwardly in the desired direction. Isotropy reduces the distance between adjacent corrodes, creating an unnecessary undercutting effect.

often unacceptably small. The line width, i.e. the lateral distance between adjacent corrosions, is large (LSI or v
Wet corrosion may not be used if it must be held within extremely small tolerances, such as required by the small geometries of LSI devices.

In many of these devices, the line difference can often be compared to the thickness of the film being eroded, so anisotropy is essential.

Isotropic corrosion resulting from wet processing becomes increasingly unacceptable as the density of circuit elements placed on a single semiconductor substrate increases. As device density increases, linewidth decreases and monoisotropic corrosion becomes less acceptable. Therefore, compared to wet corrosion, which increases the need for anisotropic or straight wall corrosion, dry corrosion provides the ability of anisotropic corrosion to keep line widths within specified tolerances. In standard dry etch equipment, the semiconductor wafer or substrate being processed is placed directly into a plasma etch chamber within a plasma or glow discharge region where charged particles and a relatively strong electric field are present. The anisotropy of the corrosion process is achieved when there are charged particles in the strong electric field region.

This is because the electric field gives directionality to the charged corrosive species.

However, L
Semiconductor layers on SI or VLSI devices are relatively thin, perhaps on the order of a micron, and ion bombardment from charged particles accelerated into the layer by an electric field can cause electrical damage to the layer, commonly known as radiation damage. This may result in abnormality or unacceptable damage. As the thickness of the oxide layer increases, the number of defective chips per wafer and loss of chip yield due to radiation damage increases to unacceptable proportions.

Radiation damage is a problem with dry photoresist strippers as well, and is not limited to plasma corrosion. Also, static charges accumulate on the exposed surface of the dielectric layer.

For example, EFROM devices are always only 10 mm thick.
Incorporates a 0 angstrom dielectric oxide layer.

Electrostatic charging effects on the dielectric layer during dry stripping of photoresist can result in dielectric breakdown and consequent inoperability of the device.

Dry etch systems, or "downstream" etch systems, in which the substrate being eroded is separated from the plasma itself are known in the art. However, although the problem of radiation damage is reduced, standard downstream equipment suffers from the same inadequacies as wet corrosion equipment in that corrosion is unacceptable and isotropic; There is no electric field present to provide any directionality to the corroding species. Mr. Nishizawa's US Patent No. 4
．． No. 2118,109 discloses a plasma etching process using a plasma generator to ionize one reactor body into a plasma state. The generator is connected to the processing chamber by a nozzle and directs the plasma into the chamber containing the workpiece to be processed.

The use of photons to influence the operation of plasma reactors is also known. U.S. Pat. No. 4,188,780 to McKenna J et al.
etching), in which a plasma reactor emits selected wavelengths of vacuum ultraviolet radiation and directs this radiation into a plasma, preferably adjacent to a substrate, to control plasma processing in particular the substrate. Contains a device that directs the plasma. Cole (k.

U.S. Pat. No. 4,404,072 to BL) and U.S. Pat. No. 4,478,677 to Cheno et al. disclose the use of light in corrosion methods.

However, these statements alone or in combination may
No downstream plasma reactor method or apparatus is shown that combines the directional ability of active species with the reduction or avoidance of radiation damage desirable for the fabrication of LSI or VLSI devices.

Means for Solving Problem L] The present invention provides a method and apparatus for treating the surface of a substrate. The method includes exposing the substrate to a gas containing at least one reactive species or substantially free of charged particles while simultaneously irradiating the substrate with ultraviolet radiation. The substrate is also heated by irradiation with infrared radiation. may be done.

OBJECTS AND EFFECTS OF THE INVENTION In a preferred embodiment of the invention, a substrate is exposed to effluent from a gaseous plasma, in which charged particles cause the plasma to be generated remotely from the substrate and into a reaction chamber. Plasma is made monokinetic by recombining or removing charged particles before introduction.

Mostly removed.

A preferred embodiment of carrying out the method of the invention comprises at least one
a means for generating a two-body plasma having two reactors; and a chamber operatively connected to the plasma generator for receiving the gaseous plasma effluent, accommodating the substrate to be processed, and exposing the substrate to the plasma effluent. and the like, the housing means being sufficiently separated from the plasma generator,
It includes means such as the chamber by which any charged particles in the plasma are dissipated before the plasma effluent reaches the substrate, and means for irradiating the substrate with ultraviolet radiation. Also,
Also included is a device that irradiates the substrate with infrared light to heat the substrate.

The present invention allows unique control over the type of reactive species in plasma effluent, UV stimulation, and temperature to optimize photoresist stripping or erosion processing. In common prior art plasma systems, these eight parameters are complexly combined and cannot be independently controlled or optimized.

The process of the present invention is essentially a chemical process performed in the substantial absence of ions and relatively low particle energies, so that it can be applied to substrates that are to be eroded very slowly to minimize substrate damage. Chemical selectivity to achieve high corrosion rates of materials can be much better controlled than with typical prior art plasma systems. The unique chemical selectivity, which can also be temperature dependent, provides a means for additional processing control.

One object of this invention is to provide a dry corrosion method and apparatus in which the deleterious effects of radiation damage are minimized.

Another object of this invention is to provide a dry corrosion method and apparatus in which anisotropic corrosion can be achieved using downstream equipment.

Another object of the invention is to provide a method and apparatus for effectively dry stripping photoresist from semiconductor wafers with minimal destructive corrosion and radiation damage.

Further advantages of the apparatus and method of the present invention will become apparent from the following two-part brief description and detailed description of the preferred embodiment.

[Example] FIG. 1 shows an apparatus 10 for processing a substrate. This process may be the erosion of a semiconductor or other substrate such as silicon or polysilicon, the stripping or removal of an organic photoresist layer from the substrate, or other similar treatment of the surface of the substrate.

Apparatus 10 includes a reaction chamber 12 having at least one substrate 86 therein to be processed. Chamber 12 can be any suitable device with a substrate, typically about 0.01 rrmHg.
The first chamber is a sealed chamber that can maintain a vacuum down to
Pump P, shown as 15 in the figure, together with valve V, shown as 16, controls the evacuation of chamber 12 to maintain the vacuum. The exhaust of the device is controlled independent of the gas input, which will be explained in more detail below, thereby allowing control of the flow rate regardless of the chamber pressure and gas presence time. Pressure monitor 18 provides an indication of the pressure or vacuum maintained inside chamber 12.

Chamber 12 has a thick, vacuum rated, transparent fused crystal window 20 located on a first side of chamber 12, shown as the top side in FIG. UV source 22, as detailed below.
Ultraviolet (UV) radiation from can be directed to the substrate 861ζ being processed inside chamber 12 through window 20. Window 20 may include any suitable material other than quartz that is transparent to ultraviolet light, such as fused silica. room 12
further comprises a quartz crystal and has a window 24 for monitoring the chemiluminescent radiation by an optical sensor 26. Room 1
2 further includes a window 28 made of calcium fluoride, zinc selenide, or other material that transmits infrared rays and allows substrate temperature to be monitored by an infrared detector 80f.

Reaction chamber 12 includes an inlet 32 that receives gaseous plasma effluent 88 from a plasma generator, indicated generally at 84. Chamber 12 also has one eg "pill box"
Means is provided to direct the plasma stream, such as gaseous Brenium 85, through a plurality of apertures 87 and onto a substrate 86. This brenium-36 and other means pass ultraviolet light, but
The gas plasma flow and the distribution of reactive species on the substrate surface can be controlled.

Plasma generator 84 is described in more detail below.

Chamber 12 contains therein a substrate to be processed, shown as 86 in FIG. The substrate 86 is made of silicon, for example.

It can be any semiconductor, such as germanium, or even gallium arsenide, or a semiconductor on which a layer of oxide, such as silicon dioxide, has been grown. The apparatus shown in FIG. 1f is also suitable for processing other substrates, such as chrome or methane masks, with slight modifications obvious to those skilled in the art.

As seen in detail in FIG. 2, wafer 86 is shown as having a patterned layer of photoresist 38 deposited thereon, the pattern being on some exposed portions 4o of wafer 36 and on other covered portions. A certain portion 42 remains. FIG. 2 also shows a wafer 86 with corrosion 4o created therein. The corrosion 4o has a floor 64 and side walls 62.

Of course, these floors or side walls do not necessarily have to be flat as shown in FIG.

In the preferred embodiment of FIG. 1, substrate or silicon wafer 86 includes a first surface 89 and a second surface 41. In the preferred embodiment of FIG. The wafer 86 is supported by a set of elongated pointed quartz pin members 44 to have a minimum contact area with the wafer 86, and the first surface 39 is supported by a set of elongated pointed crystal pin members 44 such that the first surface 39 is irradiated by the ultraviolet light source 22. It has been placed. Although this set of pins 44 is desirable in that such a support device uniformly heats the substrate from below, any suitable device for holding the substrate 86 may be used as well.

An infrared source 46 is located inside the chamber 12 and below the substrate.

This infrared source 46 irradiates the second surface 41 with Cζ
Therefore, infrared rays with a wavelength of about 1 to 10 trons are supplied to heat the wafer. In the case of a silicon substrate, silicon is substantially transparent to infrared radiation, and films such as the layer of photoresist 88 can be heated from below by infrared source 46 without substantially heating the silicon substrate. Thus, the film of photoresist 88 is heated virtually independently of the ultraviolet radiation.

A gas plasma 48 is created by a plasma generator 84 that provides at least one reactive species to erode the substrate or strip photoresist from the substrate. A gas or mixture of gases appropriate for the particular substrate 86 to be processed and the photoresist to be removed is introduced through the inlet 48 and into the conduit 50.
It flows into the plasma chamber 52 through the. Examples of such gases include Freon-14 or oxygen. A microwave exciter 54, not shown since gas input and mass flow control devices are well known in the art, activates the gas in the plasma chamber 52 into a plasma 48. Microwave exciter 54 is driven by a microwave generator including a magnetron with a frequency of about 2450 MHz and a power output of less than about 500 watts. The microwaves are directed into chamber 52 where a plasma or glow discharge region is created.

It goes without saying that the scope of the invention is not limited to the microwave plasma generators described herein, but applies equally to any means of generating gaseous plasma, such as, for example, radio frequency generators.

Gas plasma created by microwave energy 4
B is typically an ion, a free electron, or an atom.

Includes molecules, free radicals, and other excited species such as electronically excited species. Free radicals have no net charge.

However, the component gas entering inlet 48 can be selected to contain at least one reactive species that is reactive with the substrate material from which the resulting free radicals are to be removed. This allows the substrate material to be corroded or the photoresist to be removed from the substrate. For example, if the component gas is oxygen (02)
7, the synthetic plasma will contain at least a free radical or reactive species O (atomic oxygen) that reacts with materials such as organic photoresists. It may also be desirable to inject other gases downstream of the plasma generator @ this plasma 4 in the glow discharge region of the plasma chamber 84.
8 also contains ions and free electrons, which would bombard and possibly damage the substrate 86 if it were adjacent to or entered the glow discharge region. However, the plasma generator 84 is located downstream of the reaction chamber 1.
placed in an area relatively far from 2. The reaction chamber 12 is connected to a plasma chamber 84 by a conduit 58 which collects most of the ions and free electrons in the plasma in the chamber 84 before the plasma 48 flows through the conduit 58 to the downstream chamber 12. It has a predetermined length that allows it to recombine or disappear.

Therefore, the plasma effluent 88 entering the reaction chamber is virtually free of ions and electrons. The surface of the substrate is thereby provided with at least one particle that reacts with the surface without the presence of charged particles.
It undergoes a drying process by being exposed to a gas containing two reactive species. A particularly preferred reactive species contains at least one free radical, such as an oxygen atom.

Based on lifetime times on the order of microseconds for ions and free electrons, and on the order of milliseconds to seconds for free radicals and reactive species, in the apparatus 10 described herein, the preferred length of conduit 58 is 100O5CC. /M plasma flow rate is approximately 4-12 inches. Preferably, the mass change rate within chamber 12 is greater than or equal to about 100 changes/minute, and most preferably about 800 changes/minute. Reactive species with significantly larger lifetimes compared to ions and free electrons reach the reaction chamber 12 to react with the substrate 86, which thereby receives a plasma stream 8a virtually free of charged particles.

Ultraviolet light source 22 is included to irradiate substrate 86 with ultraviolet light, thereby enhancing the reaction rate of at least one reactive species in the plasma effluent introduced into chamber 12 . The preferred UV source for use in the present invention is about 1000 to 30
It emits electromagnetic waves within a range of 00 angstroms, but
Other types of ultraviolet light can also be used, such as vacuum ultraviolet light.

The ultraviolet light source 22 is also. A standard arrangement of mirrors and lenses collimates the ultraviolet light so that it strikes the exposed substrate surface 40 bed 64 at an angle substantially perpendicular to the substrate surface and the bed 64 of corrosion. As seen more clearly in FIG. 2, the ultraviolet radiation generally indicated by arrow 60 is approximately 9
It is made to strike the substrate 86 at an angle of 0°. In fact, there is no ultraviolet light on the side wall 62 of the corrosion 40. Therefore, the corrosion rate is enhanced in the bed 64 of the corrosion 40 and is effectively slower in the sidewalls 62. Thus, using such constantly collimated UV radiation, anisotropic corrosion is achieved.

The above-described apparatus of FIG. 1 is implemented not only by creating a virtually straight-walled erosion 40 in the substrate 86, but also when it is necessary to remove a predetermined portion of a layer of material from the surface of the substrate 86. It can also be seen that it is used in the process of making solid-state devices.

For example, removing the developed organic photoresist 88 from the surface of a substrate 86, such as a silicon wafer, may include
This is achieved just as silicon can be removed by an etching process.

The first step in the method is to expose a predetermined portion of the material layer to be removed to plasma effluent 88 . Because the plasma 48 is created in an area relatively remote from the substrate 36, the substrate is not subject to the relatively strong electric fields or ion bombardment associated with the glow discharge region of the plasma. The portion to be removed can be predetermined by standard photolithographic methods.

The gaseous plasma effluent 88 is selected to contain at least one reactive species, i.e. the charged particles are in fact substantially removed from the plasma effluent, so that the effluent is virtually free of ions and free electrons, thereby Damage to the substrate due to ion bombardment is minimized. This virtual removal of charged particles is accomplished by transferring the plasma into the reaction chamber 12 over a long distance such that any charged particles, such as ions or free electrons, are dissipated by recombination.

of the substrate layer as it is exposed to plasma outflow 88 .

The area where the reaction rate is to be enhanced, such as corrosion rate or photoresist strip rate, is irradiated with electromagnetic radiation including ultraviolet radiation 60. Also, in order to heat the substrate,
The substrate may be irradiated with electromagnetic radiation, preferably including infrared radiation, in the wavelength range of about 1 to 10 microns.

If anisotropic corrosion is to be achieved, the UV radiation must always be collimated to provide the appropriate directionality.
y) is given to the reactive species.

To elaborate further on the stripping operation.

The throughput rate, ie the rate at which the wafer is stripped, is an important parameter. However, if the strip reaction rate is too fast or a highly reactive corrosive gas is used to heat the substrate,
The underlying film may also be corroded along with the photoresist strip. However, ultraviolet excitation (extentio)
When n) is used, the reaction rate by using pure oxygen or other non-corrosive gas mixtures is enhanced to the point where practical strip rates are obtained.

Freon 1 creates a unique corrosive effect when combined with oxygen
There is no need to use 4. Thus, the method of the present invention reduces concerns regarding both dielectric breakdown and destructive corrosion.

Although the method and apparatus of the present invention are described for dry processing using effluent from a gaseous plasma, it will be appreciated that the present invention also describes the use of ultraviolet light to selectively enhance the reaction rate of certain portions of a substrate, such as by removing free radicals, e.g. Any dry process using chemically reactive species is contemplated. The use of effluent from a gaseous plasma that is virtually free of charged particles is desirable as a particularly effective method of practicing the present invention.

Of course, various changes and modifications to the preferred methods and implementations described above will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and are therefore intended to be covered by the following claims.

[Brief explanation of the drawing]

FIG. 1 is a sectional side view of an apparatus for carrying out the method of the invention. FIG. 2 is a cross-sectional view of a substrate as made by the method and apparatus of the present invention. Figure 1 Figure 2 Procedure Amendment (Method) 1. Indication of the incident Showa era... 6. ,,O,,1 year,,,,,,gg
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η, 7.應-夛2, Title of the invention 3, Person making the amendment-1-061,,! ! , field 101. −
1901011101. Applicant address: 06477.4, Connecticut, United States of America, Agent 5, Date of amendment order (shipment date) 7, Contents of amendment + 1) Power of attorney for orphans. (2) An engraving of the specification originally attached to the application as shown in the attached sheet (no change in content) 8. List of attached documents (1) Power of attorney and its translation 1 copy each (2
) At least 1 copy of written specification t

Claims (1)

[Claims] 1. A method of dry treating the surface of a substrate, comprising: (a) exposing the surface to a gas containing at least one reactive species and substantially free of charged electron particles so as to react with the surface; (b) simultaneously irradiating the surface with electromagnetic radiation including ultraviolet radiation. 2. A method according to claim 1, characterized in that the gas contains at least one free radical species. 3. The surface is exposed to an effluent from a gas plasma, said effluent includes at least one reactive species, and said effluent is substantially free of charged particles. Method described. 4. The gas comprises an effluent from a gas plasma, the effluent having substantially all of the charged particles to be removed therefrom, and the at least one reactive species containing at least one free radical to react with the photoresist. The method of claim 1 for removing photoresist from the surface of a semiconductor wafer, comprising seeds. 5. The method according to claim 4, wherein the free radical species includes atomic oxygen. 6. A method of making a solid state device by removing a predetermined portion of a material layer from a substrate surface, the method comprising: (a) containing at least one reactive species and containing charged particles to react with the portion to be removed; (b) simultaneously irradiating at least the portion of the layer to be removed with electromagnetic radiation, including ultraviolet radiation, thereby promoting reaction between the reactive species and said portion; and irradiating the method. 7. The method of claim 6, further comprising the step of irradiating the substrate with electromagnetic radiation comprising infrared radiation to heat portions of the layer. 8. A method for dry etching at least a portion of a substrate, comprising: (a) creating a gaseous plasma in a region relatively remote from the substrate to be corroded, the plasma containing at least one reactive species corroding the substrate; (b) substantially removing any charged particles from the plasma to create a plasma effluent; (c) exposing a substrate to the plasma effluent;
(d) concurrently with the exposure step, irradiating a portion of the substrate with collimated ultraviolet light, thereby inhibiting corrosion of the substrate by reactive species; said irradiation step being facilitated in a portion of the substrate being irradiated with ultraviolet light. 9. Virtual removal of charged particles is achieved by transferring the plasma from a relatively remote area to the substrate through a distance sufficient to dissipate any charged particles.
9. The method according to claim 8, characterized in that: 10. Claim 1 further comprising the step of irradiating the substrate with infrared radiation to heat the substrate.
The method described in section. 11. Claims further comprising the step of irradiating the surface with ultraviolet light collimated substantially perpendicular to the surface of the substrate, whereby corrosion is promoted in a direction perpendicular to the surface of the substrate. The method described in Section 8. 12. An apparatus for processing a substrate comprising: (a) an apparatus for generating a gaseous plasma having at least one reactive species; (b) operatively connected to the generator for producing a plasma effluent; (c) an apparatus for removing substantially all charged particles in the plasma; (c) operatively connected to the removal apparatus to receive the plasma effluent from which substantially all charged particles have been removed and to provide a substrate to be processed; (d) an apparatus for irradiating the substrate with electromagnetic radiation including collimated ultraviolet radiation; 13. The device of claim 12, wherein the removal device includes a predetermined length of conduit, said length being sufficient to dissipate any charged particles in the plasma. . 14. The apparatus of claim 12, further comprising a device for irradiating the substrate with electromagnetic radiation including infrared radiation. 15, the substrate includes a first and a second surface, and the containing device further includes a device for holding the substrate in position, where the first surface is positioned to be irradiated by the ultraviolet radiation device and Claims characterized in that the second surface is placed in a position to be irradiated by the infrared irradiation device, so that the substrate can be heated by the infrared irradiation device regardless of the irradiation by the ultraviolet irradiation device. Range 12th
Apparatus described in section. 16. The inclusion device is a sealed chamber capable of maintaining a vacuum, and the chamber has a window device on a first side thereof, alongside the holding device, for directing collimated ultraviolet light to the first surface of the substrate. The apparatus according to claim 15. 17. Claims characterized in that the holding device includes at least one set of elongated crystal members, the window device includes a crystal, and the containment device further includes a device for directing plasma effluent onto the substrate. 17. Apparatus according to clause 16. 18. The apparatus of claim 12, further comprising a plenum device operatively connected to the removal device to direct the plasma effluent onto the substrate to be treated. 19. The apparatus of claim 12, wherein the electromagnetic radiation comprises ultraviolet radiation in the range of about 1000 angstroms to about 3000 angstroms. 20. The apparatus of claim 14, wherein the electromagnetic radiation includes infrared radiation in the range of about 1 micron to about 10 microns. 21. A method of heating a film placed on a first surface of a silicon wafer having first and second surfaces, comprising: (a) placing the silicon wafer on the second surface for irradiation with infrared radiation. (b) irradiating the second surface with infrared radiation, whereby the infrared radiation substantially passes through the silicon and heats the film. 22. Claim 21, characterized in that the infrared radiation has a wavelength from about 1 micron to about 10 microns.
The method described in section.