FR2579059A1 - PLASMA REACTOR AND METHOD FOR REMOVING PHOTOGRAPHIC RESERVE MATERIAL - Google Patents

Abstract

THE INVENTION RELATES TO PLASMA REACTORS USED IN THE SEMICONDUCTOR INDUSTRY. A PLASMA REACTOR 12 INCLUDES IN PARTICULAR AN ACTIVE CHAMBER 14 EQUIPPED WITH AN INLET ORIFICE ALLOWING THE INTRODUCTION OF AN ACTIVE GAS. THE CHAMBER CONTAINS AT LEAST ONE PAIR OF 28E ELECTRODES ADJACENT TO THE INPUT PORT AND CONNECTED TO AN ELECTRIC GENERATOR. THE ELECTRODES CREATE AN ELECTRIC FIELD ADJACENT TO THE INPUT PORT WHICH CONVERTS ACTIVE GAS INTO ACTIVE PLASMA INTENDED TO INTERACT WITH A MATERIAL OF AN ARTICLE TO BE PROCESSED WHICH IS LOCATED IN A REGION OF THE BEDROOM IN WHICH IT DOES NOT EXIST NO ELECTRICAL FIELD. APPLICATION TO THE MANUFACTURING OF INTEGRATED CIRCUITS.

Description

i

  The present invention relates to plasma reactors

  ma, and it focuses on cy-

  plasma shields for removing photoresist material present on semiconductor wafers, or for etching thin layers of materials such as aluminum, silicon dioxide or polycrystalline silicon,

  on silicon wafers on which one has formed a

  photographic reserve material for the purpose of

attack.

  The use of a gas in the plasma state for treating

  Semiconductor wafers are a common technique.

  By way of example, J. Hollahan and A. Bell describe various

  techniques of this type in Techniques and Applica-

  tions of Plasma Chemistry, Ch.9 (1974).

  Semiconductor components are manufactured on a wafer or semiconductor substrate. The wafer material is usually silicon. In the manufacture of

  semiconductor devices, a photosensitive polymer is used.

  sible, which is called a photographic reserve material.

  After selective exposure to optical radiation, follow

  life of a chemical development, the photoresist

  graphically hardens where it has not been removed.

  and protects the underlying slice against the action of other chemicals. The use of a plasma gas is a method that can be used to remove photographic resist material from slices.

  after this material has fulfilled its protective function.

  The gas in the plasma state used to remove

  A photographic reserve material is usually oxygen. More precisely, diatomic oxygen is first exposed to an electric field that transforms a portion of the diatomic oxygen into an oxygen plasma that contains monoatomic oxygen, so-called

  general atomic oxygen. Atomic oxygen is

  to react with the photoresist material by breaking its polymer chains, so that the

  photographic reserve is removed from the semicon-

  conductor by the combined action of atomic oxygen and

  molecular oxygen. The resulting by-products include

  gases such as H20, CO and CO2. Prior art plasma reactors for the removal of photographic resist material, an example of which is shown in FIG. 2A, consist of a cylindrical quartz reactor. A number of semiconductor wafers are placed inside the reactor, and

  each of them has a layer of photoresist

  graphic on its surfaces. Metal electrodes are placed

  around the reactor, and one of these is connected to a radio frequency (RF) generator operating at 13.56 MHz or a harmonic of that frequency while the other is

  connected to the ground. The quartz reactor also includes

  a gas inlet manifold and an evacuation collector.

  tion. Other prior art plasma reactors, not shown, consist of a single chamber reactor which has an electrode inside the chamber, and the

  US Pat. No. 4,230,515 shows a good example of this type of reaction.

  tor. In addition, prior art reactors consist of

  in a two-chamber reactor in which the plasma is

  in a chamber and the work such as the removal of the photographic resist material is performed in a second chamber. Plasma can be transferred between the two chambers-either through a narrow conduit or through tubes

  narrow. The main drawback of the two-chamber reactor

  is the probability of degeneration of the plasma before it can effect the removal of the photoresist, that is, atomic oxygen tends to recombine into diatomic oxygen on the walls of the plasma.

leads or tubes.

  In single-chamber reactors of the prior art having external electrodes, the electrodes surround all sides of the cylindrical reactor, so that the electric field fills the entire volume of the reactor. However, because of the electrical skin effect of the RF discharge, the generated electric current tends to circulate substantially along the reactor wall. This effect is analogous to the phenomenon that a high frequency current flows near the surface or skin

  a metallic conductor. Thus, most of the oxy-

  Atomic gene is produced near the walls of the reactor and is pumped out of the reactor without passing near the slices. The

  the only atomic oxygen involved in the process of

  is the one that diffuses towards the center of the reactor where

  find the slices and then diffuse between the

ches.

  In view of these defects of the prior art, a main object of the invention is to produce a reactor with

  plasma that is able to maximize the use of

  plasma in the performance of chemical reactions.

  desired. In the case of the removal of a photoresist material, it is a question of maximizing the reaction of

  atomic oxygen with photographic resist material.

  To achieve the above purpose as well as others, the invention provides a plasma reactor that has a working chamber or active chamber with at least one inlet port that is adapted to admit an active gas into the reactor. active room. In addition, the active chamber is designed to receive at least one article. An electric power generator is used. At least one pair of electrodes are

  placed adjacent to the inlet of the chamber.

  active breed. The electrodes, which are connected to the generator, create a field adjacent to the inlet

  which converts the active gas into an active plasma of

  designed to interact with a material of the article. The position of the electric field, adjacent to the inlet port, leaves

  a region virtually free of electric fields in the

  cylindrical, in the vicinity of the article.

  In addition, the plasma reactor of the invention

  takes a plasma flow guide that is placed inside the

  in the active room. The flow of gas can only be through the guide, which enhances the interaction of the gas with the material of the article. More specifically, the guide

  comprises at least one opening which is provided in such a way as to

  see the article and allow the passage of gas.

  It should be noted that if the material being treated is placed in the center of the electric field used to create the

  plasma species, the chemical species of interest are

  neat and circulate around the sides of the material that is treated, without reacting with it in an appreciable way. By generating the plasma upstream of the material being treated, one can easily force the interesting chemical species to flow into positions adjacent to the material that is

  treated. We must do this without passing the flow-

  through narrow restrictions that destroy

interesting chemical species.

  In the preferred embodiment of the invention, the material of the article that is removed by the active plasma is a photographic resist material. In addition, the article is a semiconductor wafer. Finally, active plasma

consists of oxygen.

  The invention will be better understood on reading the

  detailed description which follows of an embodiment

  preferred, and with reference to the accompanying drawings in which: Figure 1 is a perspective view of the cylindrical plasma reactor of the invention; FIG. 2 is a schematic representation,

  partially in section, of a plasma reactor of the prior art.

  laughing; Figure 3 is a schematic representation, partially in section, of the cylindrical plasma reactor of Figure 1; and

  FIG. 4 is a diagrammatic representation,

  partially in section, of the plasma flow guide of the reaction

  cylindrical plasma reactor of Figures 1 and 3.

  Referring to Figure 1, there is shown a cylindrical plasma reactor generally designated 12. The reactor 12 comprises an active or working chamber 14 which is cylindrical and generally barrel-shaped. The cylindrical chamber 14 may have a diameter of 15 to 30 cm; in the preferred embodiment, the diameter of the chamber

  14 is 30 cm. The axial length of the chamber 14 is

  viron 53 cm. The chamber 14 includes a set of inlet ports 16 for receiving an active gas, and a set of discharge ports 18 for discharging various gases and by-products from the chamber 14. In the preferred embodiment there are four inlet openings 16 and five discharge openings 18. In addition, as shown in FIG.

  better, the inlet ports 16 are placed in positions.

  diametrically opposed to the discharge ports 18. In the preferred embodiment, the chamber 14 is made from a conventional inert material such as quartz.

  The chamber 14 is designed to receive an

  20. As shown, items 20 are semiconductor wafers, and each of them carries a layer of photographic resist material when

  slices are placed in room 14.

  The reactor 12 further comprises a collector of

  gas stream 22 which is placed adjacent to the chamber

  14. The gas inlet manifold 22 is a tube,

  made of quartz, which comprises a set of orifices 24, and

  each of them is in communication with one of the orifices of

  16 of the cylindrical chamber. In the embodiment

  preferred, the gas inlet manifold 22 has four ori-

  24. The gas inlet manifold 22 is capable of

  the active gas to the cylindrical chamber 14.

  The reactor comprises an electric energy generator

  than radio frequency (RF), not shown. In the embodiment of

  In the preferred embodiment, the frequency of the RF energy is 13.56 MHz.

  The reactor 12 furthermore comprises a pair of electrodes

  28 ° and 30 ° inlet ports, which are placed in position

  adjacent to the inlet ports 16 of the cylindrical chamber

  that, as Figure 3 shows it best. Each of the electro-

  28 and 30, which is made from a conductive metal

  such as copper, has a slightly curved configuration so as to follow the curvature of the chamber 14.

  28th and 30th electrodes are able to create an electric field

  in the cylindrical chamber 14, adjacent to the inlet ports 16. This electric field of inlet ports Ee then converts the active gas into an active plasma. In addition, the position of the electric field of entry orifices Ee delimits in the chamber 14 a region FR practically free of field

  adjacent to Articles 20.

  There is also a pair of neck electrodes

  28m and 30m, which are placed in a position adjacent to the

  gas inlet manifold 22. Each of the

  28m and 30m drive is a plate extending generally in the vertical direction, which is placed on one side or the other of the collector 22, as Figure 3 shows it best. The electrodes 28m and 30m are also manufactured from a

  conductive metal such as copper. Collecting electrodes

  28m and 30m are able to create an electric field in

  the collector 22. The collector electric field Em converts

  Part of the active plasma active gas before the active gas enters the chamber 14. The combined action of the collector electric field E and the inlet electric field m E effectively converts the active gas to give the e

desired active plasma.

  Although the electrodes 28e and 28m and the electrodes 30e and 30m are described and claimed as separate and discrete electrodes, the electrodes 28e and 28m could be manufactured as a single electrode, and

  the electrodes 30e and 30m in the form of a single electrode.

  - In addition, the collector electrodes 28m and 30m are not mandatory in all cases. Although the electric field

  of collector Em that generate the electrodes 28m and 30m con-

  effectively reduces the effective conversion of active gas to active plasma, the removal of this field does not affect the overall conversion of active gas to active plasma by the field

  electric inlet openings Ee alone.

  The reactor 12 also includes a listening guide

  Plasma 40 is placed inside the cylindrical chamber 14. The guide 40 is a flat,

  planchette, which comprises a set of openings 42. The

  vertices 42 perform two functions and the first of them is to receive slices 20. First place slices 20 in a conventional slice receptacle 44,

  which is generally called a slider carrier.

  Each slice carrier 44 is capable of receiving several

  slices, as Figure 4 shows best. The

  slices placed in the basket 44 are sufficiently spaced

  in relation to each other so that the oxygen ato-

  It can flow between them and react with the photographic reserve material on the slices. We

  then places in the opening 42 the basket 44, which is

  bricked from an inert material such as quartz.

  The second, most important function of the board

  is to restrict the flow of the active gas and the

  The active gas ceases to be a plasma when it leaves the electric field. In a reactor of the prior art such as that shown in FIG. 2, a significant quantity of the active gas, or in this case plasma, can never come into contact with the slices 120. This is because it exists in the chamber 114 sufficient space to allow a drift

  free plasma. On the contrary, the plate 40 has a configuration

  to divide room 14 into two areas, to the extent that

  see an active region 46 and an evacuation region 48. The openings 42 constitute the only communication between these two regions. This structure forces the active gas to pass

  only through openings 42, which are immediately

  Accordingly, all of the plasma flows between the slices 20 and reacts with the photoresist material. The tray 40, which has approximate dimensions of 53 cm x 23 cm x 0.3 cm, is made from a non-reactive material, such as hard anodized aluminum. We can also make the

40 plateau in quartz.

  The reactor 12 further comprises an evacuation manifold 50 which is placed adjacent to the

  14. The exhaust manifold 50 is a tube,

  quartz, which has a number of orifices 52.

  Each of these orifices is in communication with one of the discharge orifices 18 of the cylindrical chamber. In the preferred embodiment, the exhaust manifold 50 has five orifices 52. The exhaust manifold 50 is able to evacuate from the chamber 14 any remaining active plasma, as well as gaseous by-products of the reaction between the

  plasma and photographic resist material.

  In the course of use, first place

  in the apertures 42 of the tray 40 of the trolley nacelles

  44 each containing several slices.

  suite in room 14 a moderate vacuum, about 100 Pa.

  evacuated using a conventional pump, not representative of

  This is connected to the exhaust duct 50. Diatomic oxygen, which is the active gas, is introduced into the chamber 14 via the gas inlet manifold 22. A source

  of diatomic oxygen, not shown, is connected to the

gas inlet valve 22.

  The RF generator is then turned on, so that the electrodes 28e, 28m, 30e and 30m generate electric fields in both the gas inlet manifold 22 and the chamber 14. The electric fields produced,

  Ee and Em, decompose the diatomic oxygen into mono-oxygen

  atomic, which constitutes the active gas. The electric field in the collector 22 converts a small fraction of the active gas into plasma before the gas enters the orifices 16 of the chamber 14. The remaining portion of the active gas is converted.

  in plasma by the electric field which exists in the adjacent position

  at the inlet ports 16 of the chamber. The position of the electric field of inlet ports Ee forces all the active gas to pass through the field, which improves the conversion of the

plasma gas.

  The path taken by the active gas in circulation

  in the chamber 14 is imposed by the guide plate 40.

  Instead of meandering in the chamber 14, as is the case for the plasma in rooms of the prior art, it can only go out through the openings 42. Because the slices 20 are placed immediately above the openings 42, all the plasma must pass between the slices 20. Because this increases the number of interactions between the oxygen and the photoresist material, the duration

  necessary to fully accomplish the removal process.

  photographic resist material is shortened.

  It goes without saying that many modifications can

  may be made to the device described and shown without

depart from the scope of the invention.

Claims (21)

  1. Plasma reactor, characterized in that it com-   takes: an active chamber (14) having at least one ori-   the input chamber (16) being designed to receive at least one article (20), and the inlet (16) being adapted to admit an active gas into the active chamber (14). ); an electric power generator; and   at least one pair of electrodes (28e, 30e) placed in position   adjacent to the inlet (16) of the active chamber   ve, these electrodes, which are connected to the generator, creating in the vicinity of the inlet (16) an electric field (Ee) which converts the active gas into an active plasma for   interact with a material of the article (20), and this confi-   guration creates downstream of the plasma generation region   an area free from an electric field in which the article cle (20) is placed.   2. Plasma reactor according to claim 1,   characterized in that the electric field-free region is shaped to guide the flow of the active plasma as it passes through the article (20) to be treated. 3. Cylindrical plasma reactor, characterized in that it comprises: an active chamber (14) of generally cylindrical shape, comprising at least one inlet orifice (16), this cylindrical chamber being designed to receive at least one article (20) and the inlet (16) of the cylindrical chamber being adapted to admit an active gas into the cylindrical chamber (14); an electric power generator; and at least one pair of electrodes (28e-30e) placed adjacent to the inlet port   (16) of the cylindrical chamber, these electrodes, which are   connected to the generator, creating in the vicinity of the   trea (16) an electric field (Ee) which converts the active gas into an active plasma for interacting with a material of the article (20), whereby the position of the electric field (Ee) in the vicinity of the orifice input (16) promotes a   efficient conversion of the active gas into active plasma.   4. Cylindrical plasma reactor, characterized in that it comprises: an active chamber (14) of generally cylindrical shape, comprising at least one inlet orifice (16), this cylindrical chamber being designed to receive at least one article ( 20); a gas inlet manifold (22) located adjacent the cylindrical chamber, said gas inlet manifold (22) including at least one port (24) which   communicates with the inlet (16) of the cylindrical chamber   (14), and this gas inlet manifold (22) being   designed to bring an active gas into the cylindrical chamber (14); an electric power generator; and at least one pair   electrodes (28th, 30th, 28m, 30m) placed   both at the inlet (16) of the cylinder chamber   and to the gas inlet manifold (22), these electrodes, which are connected to the generator, creating an electric field   which converts the active gas into an active plasma capable of   teragir with the material of the article (20).   5. Cylindrical plasma reactor, characterized in that it comprises: an active chamber (14) of cylindrical general shape comprising at least one inlet orifice (16), this active chamber (14) being designed to receive at least one least one article (20); a gas inlet manifold (22) located adjacent to the cylindrical canopy (14), which   gas inlet manifold (22) having at least one   which (24) communicates with the inlet (16) of the cylindrical chamber, and the gas inlet manifold (22) is adapted to deliver an active gas into the cylindrical chamber (14); an electric power generator; at least one pair of inlet port electrodes (28e-30e) positioned adjacent to the inlet (16) of the cylindrical chamber, which electrodes are connected to the generator, creating in the chamber cylindrical, in the vicinity   the input port (16), an electric field (E) which   12_ brightens the active gas into active plasma; and at least one pair   collector electrodes (28m-30m) placed in the adjacent position   at the gas inlet manifold (22), these electrodes of   collector (28m, 30m), which are also connected to the gen-   generator, creating in the collector (22) an electric field (Em) which converts a portion of the active gas into an active plasma, before this active gas enters the cylindrical chamber (14), whereby the electric field of manifold (Em) and the electric field of inlet ports (Ee) effectively convert the active gas into active plasma intended to interact   with a material of the article (20).   6. Plasma reactor, characterized in that it com-   takes: an active chamber (14) having at least one inlet (16) for admitting an active gas into the active chamber (14), and the active chamber being adapted to receive at least one article (20) ; an energy generator   electric; at least one pair of electrodes (28th, 30th)   formed around the active chamber (14), these electrodes, which are connected to the generator, creating an electric field (Ee) which converts the active gas into an active plasma; and a plasma flow guide (40) disposed within the active chamber (14) for restricting the flow of the active plasma, whereby the flow of the active plasma can be effected only through the guide, which reinforces the interaction between   active plasma and a material of the article (20).   Plasma reactor according to claim 6,   characterized in that the plasma flow guide (40) comprises   carries at least one opening (42) which is adapted to receive the article (20) and to allow the passage of the plasma active.   8. Cylindrical plasma reactor, characterized in that it comprises: an active chamber (14) of generally cylindrical shape, comprising at least one inlet orifice (16), this cylindrical chamber being designed to receive at least one article (20); a gas inlet manifold (22)   placed adjacent to the cylindrical chamber, this collar   gas inlet reader (22) having at least one orifice   (24) which communicates with the inlet (16) of the chamber   cylinder (14), and this gas inlet manifold (22) being adapted to bring an active fluid into the chamber   cylindrical; a radiofrequency electric energy generator   accordingly; at least one pair of inlet port electrodes (28e, 30e) positioned adjacent the inlet port   (16) of the cylindrical chamber, these electrodes, which are   connected to the generator, creating in the cylindrical chamber,   adjacent to the inlet (16), an electric field   trique (Ee) which converts the active gas into active plasma; e   at least one pair of collector electrodes (28m, 30m)   these collector electrodes (28m, 30m), which are also connected to the generator, create in the collector an electric field (Em) which converts a portion of the active gas into the collector. an active plasma, before the active gas enters the cylindrical chamber, whereby the collector electric field   (Em) and the electric field of inlet orifices (Ee) conver-   effectively weave the active gas into active plasma; and a plasma flow guide (40) disposed within the cylindrical chamber (14) for restricting the flow of the active plasma, the flow of the active plasma being able to be effected only through the guide (40). ), in order to reinforce the interaction   active plasma with a material of the article (20).   9. Cylindrical plasma reactor according to any one   of claims 3, 5 or 8, characterized in that the   position of the electric field (Ee) adjacent to the   trea (16) delimits in the cylindrical chamber (14) a region substantially free of electric field, in the vicinity of   the article (20) downstream of the plasma generation region.   10. Cylindrical plasma reactor according to the   cation 9 taken with claim 8, characterized in that the plasma flow guide (40) consists of a plateau   of a generally planar shape, similar to a board, which   carries at least one opening (42) provided to receive the   (20) and to allow the passage of the active plasma.   11. Cylindrical plasma reactor according to any one   conque of the preceding claims, characterized in that   said material of the article (20) is a photographic resist material.   12. Cylindrical plasma reactor according to the   cation 11, characterized in that the article (20) consists of a semiconductor wafer.   13. Cylindrical plasma reactor according to the   cation 12, characterized in that the active plasma consists of oxygen.   14. Cylindrical plasma reactor according to any one   one of claims 1 to 9, characterized in that   of the article (20) is a thin layer of aluminum, silicon dioxide or polycrystalline silicon on silicon wafers on which a photographic resist material pattern has been formed and which are ready for engraving operation.   15. A method for interacting an active plasma   with an article (20) which is placed inside a chamber   active class (14), characterized in that it comprises the   following: placing the article in an active position within the chamber (14); an active gas is introduced into the chamber (14) at a location remote from the active position; an electric field (Ee) is established to convert the active gas into active plasma for interaction with a material of the article (20); and we confined the electric field   in an area immediately adjacent to the location   the active gas is introduced into the active chamber (14), whereby the active plasma interacts with the material of the article (20) in the active position in which it   There is virtually no electric field.   16. A method for interacting an active plasma with an article (20) which is placed inside an active chamber (14), characterized in that it comprises the following operations: the article is placed ( 20) in an operative position within the chamber (14); an active gas is introduced into the chamber (14) at a location remote from the active position; an electric field (Ee) is established to convert the   active gas into an active plasma for interacting with a   section (20); and we restrict the flow of   active plasma in order to enhance the interaction of the plasma   tif with the material of the article (20).   17. A method for interacting an active plasma with an article (20) which is placed inside an active chamber (14), characterized in that it comprises the following operations: placing the article (20) in an active position inside the chamber (14); an active gas is introduced into the chamber (14) at a location remote from the active position; an electric field (Ee) is established to convert the active gas into active plasma for interaction with a material of the article (20); the electric field (Ee) is confined in a region immediately adjacent to the location where the active gas is introduced into the active chamber (14), whereby the active plasma interacts with the material of the article (20) at the active position in which there is   virtually no electric field; and we restrict the   active plasma in order to enhance the interaction of the   active plasma with material of the article (20).   18. A method for interacting an active plasma   with an article according to any one of claims 15,   16 or 17, characterized in that said material of the article   (20) is a photographic resist material.   19. A method of interacting an active plasma with an article according to claim 18, characterized in that   that the article (20) is a semiconductor wafer.   20. A method for interacting an active plasma with an article according to claim 19, characterized in that   that the active plasma consists of oxygen.   21. A method for interacting an active plasma   with an article according to any one of claims 15,   16 or 17, characterized in that the material of the article (20) is a thin layer of aluminum, silicon dioxide or   polycrystalline silicon formed on silicone slices   which has been defined as a reason for   are ready to undergo an engraving operation.