Ion source special for multivalent ion implantation and use method thereof

Abstract

The invention relates to the technical field of wafer manufacturing equipment, and particularly discloses a special ion source for multivalent ion implantation and a use method thereof.The special ion source comprises a first gas supply source, a second gas supply source, an ion generator with a first-stage reaction arc chamber and a second-stage reaction arc chamber, generating an ion beam containing monovalent ions of the source gas supplied by the first gas supply source; and a secondary reaction arc chamber for generating multivalent ions of the source gas supplied by the first gas supply source by means of charge exchange generated by collision between an ion beam containing the monovalent ions of the source gas supplied by the first gas supply source and the source gas supplied by the second gas supply source. The method has the advantages that the size of the multivalent ion beam can be effectively increased, the beam adjustment time and the machine operation time are optimized, and the machine productivity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer manufacturing equipment, and in particular to an ion source dedicated for multivalent ion implantation and a method for using the same. Background Art

[0002] Under certain process conditions in wafer manufacturing, a medium-beam ion implanter is required to perform higher-energy ion implantation. This requires the equipment to screen out multivalent ions for implantation into the wafer substrate. However, the number of multivalent ions excited by current ion sources is very small, and the corresponding ion beam current is too small, resulting in the equipment's WPH being unable to meet production requirements.

[0003] In the ion implantation process of wafer manufacturing, the ions that need to be doped into the wafer substrate are generated by the ion source. The specific principle is that the electrons generated by the ion source filament collide with the gas particles introduced into the arc chamber, causing the electrons in the outer layer of the particles to break away from their original orbits and become free electrons. The corresponding particles lose an electron and become positively charged ions. Taking BF3 gas as an example of the introduced dopant, if the B atom loses an outer electron due to collision, it becomes a B+ ion (with a positive charge). If another collision occurs and another outer electron is lost, it becomes a B++ ion (with two positive charges) (see Figure 1 ).

[0004] The range is an important parameter in the ion implantation process. It refers to the distance that the ions travel from the surface to the stop after entering the wafer during implantation. The higher the energy of the incident ions, the longer the range. The energy KE of ion implantation is generally expressed as the product of the electron charge and the potential difference, that is, electron volts (eV): KE = nV; where KE is energy, the unit is electron volts (eV); n is the charge state of the ion, such as an ion with one positive charge, n is equal to 1, and an ion with two positive charges, n is equal to 2; V is the potential difference, the unit is volt.

[0005] For example: medium beam ion implanter AMAT VIISta 900XP (its working principle is shown in Figure 2 The maximum potential difference the equipment hardware can provide is 300kV. Therefore, for processes requiring energies of 300keV or less, B+ (monovalent) ions are used. For processes requiring energies between 300keV and 600keV, B++ (divalent) ions are used. For processes requiring energies between 600keV and 900keV, B+++ (trivalent) ions are used. After passing through the extraction assembly, all plasmas enter the analyzer magnet. Plasmas of different charge-to-mass ratios have different turning radii: Where, M is the mass of the ion; V is the energy of the ion; q is the charge of the ion, which is 1 for monovalent ions, 2 for divalent ions, and 3 for trivalent ions; k is a setting parameter, which is related to the set size of the magnetic field. Setting the corresponding magnetic field strength can make the divalent ion beam pass through the exit of the screening magnetic field, while the remaining monovalent or trivalent ions hit the graphite substrate of the screening component and cannot pass through. Since the second ionization energy of B (2427.1kJ·mol-1) is much higher than the first ionization energy (800.6kJ·mol-1), the probability of secondary collisions in the ion source arc chamber to produce B++ is very low, and the ion beam size corresponding to each valence ion can well reflect this phenomenon (see Figure 3 ).

[0006] Dose is another important parameter in the ion implantation process. It indicates the number of ions implanted per unit area of ​​the target surface, and the unit is atoms or ions per square centimeter. The dose formula is: Q = It / enA; where Q is the dose, and the unit is ions or atoms / cm 2 I is the beam current in amperes (coulombs per second); t is the injection time in seconds; e is the electron charge, 1.6×10^-19C; n is the number of charges, such as the charge of a B+ ion is 1; A is the injection area in cm 2 Through the analysis of the ion beam current spectrum of BF3 doping gas, the B++ ion beam current is only about 3% of the B+ ion beam current. Under the condition of the same doping dose, if divalent ion implantation is used, the implantation time needs to be greatly increased, which in turn affects the number of wafers output per hour of the equipment. Summary of the Invention

[0007] In order to overcome the above-mentioned shortcomings of the prior art, in which the number of divalent ions produced by the ion source is insufficient, the injection time needs to be greatly increased, and the number of wafers produced per hour of the equipment is affected, the present invention provides an ion source dedicated to polyvalent ion injection, which has the advantages of effectively increasing the size of the polyvalent ion beam, optimizing the beam adjustment time and the machine operation time, and improving the machine production capacity.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] An ion source dedicated to polyvalent ion implantation comprises: a first gas supply source and a second gas supply source for supplying source gas of ion species; an ion generator having a primary reaction arc chamber, which utilizes the source gas supplied by the first gas supply source to generate an ion beam containing monovalent ions of the source gas supplied by the first gas supply source; and a secondary reaction arc chamber, which utilizes the ion beam containing monovalent ions of the source gas supplied by the first gas supply source to collide with the source gas supplied by the second gas supply source to generate charge exchange, thereby generating polyvalent ions of the source gas supplied by the first gas supply source.

[0010] Optionally, the source gas for supplying ion species includes a gas containing boron, phosphorus, or arsenic.

[0011] Optionally, the gas containing boron elements in the source gas for supplying ion species includes BF3, or the gas containing phosphorus elements in the source gas for supplying ion species includes PH3, or the gas containing arsenic elements in the source gas for supplying ion species includes AsH3.

[0012] Optionally, the source gas of the second gas supply source includes helium.

[0013] Optionally, the polyvalent boron ions include both divalent boron ions and trivalent boron ions, or the polyvalent phosphorus ions include both divalent phosphorus ions and trivalent phosphorus ions, or the polyvalent arsenic ions include both divalent arsenic ions and trivalent arsenic ions.

[0014] Optionally, the primary reaction arc chamber and the secondary reaction arc chamber are fixedly connected via a connector.

[0015] Optionally, a grounding electrode plate is further provided on the outer side of the output end of the secondary reaction arc chamber.

[0016] Optionally, the first gas supply source is connected to the primary reaction arc chamber through a primary reaction arc chamber gas supply pipe.

[0017] Optionally, the gas outlet of the gas pipe of the first-level reaction arc chamber, the gas outlet of the first-level reaction arc chamber and the gas outlet of the second-level reaction arc chamber are located on the same longitudinal axis.

[0018] Optionally, the ion generator includes a reflector installed on one side of the primary reaction arc chamber, and a cathode is provided on the other side opposite to the reflector, a filament is installed in the cathode, the filament is connected to the ion source filament clamp, the cathode is connected to the ion source cathode clamp, the reflector is connected to the ion source reflector clamp, and the ion source cathode clamp and the ion source reflector clamp are connected by an equipotential connecting strip.

[0019] Optionally, the dedicated ion source for multivalent ion implantation of the present invention further comprises a base, and the ends of the ion source filament clamp, the ion source cathode clamp and the ion source reflector clamp are all connected to the base.

[0020] Optionally, the second gas supply source is connected to the secondary reaction arc chamber through a secondary reaction arc chamber gas pipe.

[0021] The present invention also discloses a method for using a dedicated ion source for polyvalent ion implantation, which is used to prepare an ion beam of polyvalent ions of a source gas supplied by a first gas supply source, comprising the following steps: a. utilizing a source gas supplied by a first gas supply source to generate an ion beam comprising monovalent ions of the source gas supplied by the first gas supply source; b. An ion beam containing monovalent ions of the source gas supplied by the first gas supply source, generated by the ion generator, collides with the source gas supplied by the second gas supply source to exchange charges, thereby generating polyvalent ions of the source gas supplied by the first gas supply source.

[0022] The beneficial effects of the present invention include at least: (1) the present invention can effectively increase the size of the multivalent ion beam, optimize the beam adjustment time and the machine operation time, and improve the machine production capacity; (2) the present invention can help medium-beam ion implanters break through the limitations of high-energy process conditions, and compared with more expensive high-energy ion implanters, it can save a certain amount of equipment procurement expenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the principle diagram of BF3 gas ion excitation; Figure 2 This is the schematic diagram of the medium beam ion preparation principle; Figure 3 It is the ion beam current spectrum of BF3 doping gas; Figure 4 The multivalent ion excitation principle of the present invention Figure 1 ; Figure 5 The multivalent ion excitation principle of the present invention Figure 2 ; Figure 6 3D structural diagram of the dedicated ion source for multivalent ion implantation according to embodiment 1 of the present invention; Figure 7 It is a cross-sectional structural diagram of the ion source dedicated for multivalent ion implantation according to embodiment 1 of the present invention.

[0024] In the figure: 1. Primary reaction arc chamber, 2. Secondary reaction arc chamber, 3. Connector, 4. Gas pipe for primary reaction arc chamber, 5. Reflector, 6. Cathode, 7. Filament, 8. Ion source filament clamp, 9. Ion source cathode clamp, 10. Ion source reflector clamp, 11. Equipotential connecting strip, 12. Base, 13. Support foot, 14. Gas pipe for secondary reaction arc chamber, 15. Ion source magnetic field. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] Example 1: Figure 4 and Figure 5 As shown, a dedicated ion source for polyvalent ion implantation comprises: a first gas supply source for supplying source gas for ion species, a second gas supply source, an ion generator having a primary reaction arc chamber 1, and a secondary reaction arc chamber 2. The source gas for supplying ion species comprises a gas containing the element boron. The ion generator having the primary reaction arc chamber generates an ion beam containing monovalent boron ions using the source gas supplied by the first gas supply source. The secondary reaction arc chamber generates polyvalent boron ions by colliding the ion beam containing monovalent boron ions generated by the ion generator with the source gas supplied by the second gas supply source to generate charge exchange. The polyvalent boron ions include both divalent and trivalent boron ions.

[0028] like Figure 6 As shown, the primary and secondary reaction arc chambers are fixedly connected via a connector 3. A ground electrode plate is also provided on the outer side of the output end of the secondary reaction arc chamber. A first gas supply source is connected to the primary reaction arc chamber via a primary reaction arc chamber gas supply pipe 4. The gas outlet of the primary reaction arc chamber gas supply pipe, the gas outlet of the primary reaction arc chamber, and the gas outlet of the secondary reaction arc chamber are located on the same longitudinal axis. This allows the source gas supplied by the first gas source output from the primary reaction arc chamber gas supply pipe to be accelerated and ionized by the ion source magnetic field to generate an ion beam at a higher speed, and during this process, the resistance to entering the primary and secondary reaction arc chambers in sequence is reduced.

[0029] like Figure 7As shown, the ion generator includes a reflector 5 installed on one side of the primary reaction arc chamber, and a cathode 6 is provided on the other side opposite to the reflector. A filament 7 is installed in the cathode, and the filament is connected to an ion source filament clamp 8. The cathode is connected to an ion source cathode clamp 9. The reflector is connected to an ion source reflector clamp 10. The ion source cathode clamp and the ion source reflector clamp are connected by an equipotential bonding tape 11.

[0030] In this embodiment, the filament is connected to a DC power supply, which heats the filament to a preset temperature to generate free electrons. The free electrons are accelerated and gain energy through the ion source magnetic field between the cathode and the filament. The energized electrons bombard the inner surface of the cathode, causing the cathode to be heated and generate free electrons. The reflector is arranged opposite the cathode and is at the same potential as the cathode. The reflector reflects the moving free electrons, reflecting the free electrons moving toward the reflector back into the arc chamber space, continuing to generate impact ionization and improving ionization efficiency. Within the primary reaction arc chamber, the free electrons ionize the boron-containing gas to form boron ions to meet the element injection requirements. The ion source filament clamp, ion source cathode clamp, and ion source reflector clamp are all made of long strips of molybdenum alloy, which have characteristics such as high temperature resistance, low thermal expansion coefficient, and resistance to electron bombardment.

[0031] In this embodiment, the equipotential bonding strip may be made of copper cable, copper strip or galvanized steel, which must meet the conductivity and corrosion resistance requirements. It is used to eliminate the potential difference between different conductors and prevent electric shock, sparks or equipment damage caused by the potential difference.

[0032] The ion source for multivalent ion implantation of the present invention further comprises a base 12, to which the ends of the ion source filament clamp, the ion source cathode clamp and the ion source reflector clamp are all connected. A plurality of supporting legs 13 are further provided below the base.

[0033] In this embodiment, the ion source filament clamp, the ion source cathode clamp, and the ion source repeller clamp are all inserted into the base.

[0034] The second gas supply source is connected to the secondary reaction arc chamber through the secondary reaction arc chamber gas pipe 14 .

[0035] In this embodiment, both the first and second gas supply sources are external gas cylinders, not shown in the accompanying drawings. These external gas cylinders are connected via gas pipelines to the primary and secondary arc chamber gas supply pipes, whose ends are fixed to the base. Electronic valves can be installed on both the primary and secondary arc chamber gas supply pipes to precisely control gas flow.

[0036] In the present invention, the primary arc chamber produces primarily monovalent ions (B+), which are accelerated by the pull voltage toward the secondary arc chamber. Helium is introduced into the secondary arc chamber, where the monovalent B+ ions collide with He molecules, generating secondary ionization. An ion source magnetic field 15 is installed outside the primary arc chamber.

[0037] In the present invention, B+ and He molecules collide in the secondary reaction arc chamber to cause charge exchange. Since the first ionization energy of He is close to the second ionization energy of B, the probability of B+ gaining an electron to become a neutral B atom or losing an electron to become a divalent ion B++ is similar. Even if only half of the B+ in the secondary reaction arc chamber lose electrons to become B++, their number is much greater than the number of B+ in the primary reaction arc chamber (only about 3% of B+), which can effectively increase the beam size of the divalent ions.

[0038] The boron gas in the source gas for supplying ion species is BF3.

[0039] The source gas of the second gas supply source is helium.

[0040] In another embodiment, the ion implanter further includes a central control device, which controls the overall operation of the ion implanter. The central control device is implemented in hardware by components such as a computer's CPU, memory, or mechanical devices, and in software by a computer program. The various functions provided by the central control device can be realized through the coordination of hardware and software.

[0041] Example 2: The present invention also discloses an ion source dedicated to polyvalent ion implantation, comprising: a first gas supply source for supplying source gas of ion species, a second gas supply source, an ion generator having a primary reaction arc chamber, and a secondary reaction arc chamber. The source gas for supplying ion species includes a gas containing phosphorus element. The ion generator having the primary reaction arc chamber generates an ion beam containing monovalent phosphorus ions using the source gas supplied by the first gas supply source; the secondary reaction arc chamber generates polyvalent phosphorus ions by colliding the ion beam containing monovalent phosphorus ions generated by the ion generator with the source gas supplied by the second gas supply source to generate charge exchange. In the primary reaction arc chamber, free electrons ionize the phosphorus-containing gas to form phosphorus ions. The polyvalent phosphorus ions include both divalent phosphorus ions and trivalent phosphorus ions.

[0042] The source gas for supplying ion species is PH3. In this embodiment, PH3 is selected as the doping gas. When charge exchange occurs in the secondary reaction arc chamber, P+ has a greater probability of losing an electron to obtain divalent ions P++, which helps to increase the divalent ion beam current.

[0043] Example 3: The present invention also discloses an ion source dedicated to polyvalent ion implantation, comprising: a first gas supply source for supplying source gas of ion species, a second gas supply source, an ion generator having a primary reaction arc chamber, and a secondary reaction arc chamber. The source gas supplying ion species includes a gas containing arsenic. The ion generator having the primary reaction arc chamber generates an ion beam containing monovalent arsenic ions using the source gas supplied by the first gas supply source; the secondary reaction arc chamber generates polyvalent arsenic ions by colliding the ion beam containing monovalent arsenic ions generated by the ion generator with the source gas supplied by the second gas supply source to generate charge exchange. The polyvalent arsenic ions include both divalent arsenic ions and trivalent arsenic ions. In the primary reaction arc chamber, free electrons ionize the arsenic-containing gas to form arsenic ions.

[0044] AsH3 is used as the source gas for supplying ion species. In this embodiment, AsH3 is selected as the doping gas. When charge exchange occurs in the secondary reaction arc chamber, As+ has a greater probability of losing an electron to form divalent ions As++, which helps to increase the divalent ion beam current.

[0045] Example 4: The present invention also discloses a method for using a dedicated ion source for multivalent ion implantation, which is used to prepare an ion beam of multivalent boron ions, comprising the following steps: a. utilizing a source gas supplied by a first gas supply source to generate an ion beam comprising monovalent ions of the source gas supplied by the first gas supply source; b. An ion beam containing monovalent ions of the source gas supplied by the first gas supply source, generated by the ion generator, collides with the source gas supplied by the second gas supply source to exchange charges, thereby generating polyvalent ions of the source gas supplied by the first gas supply source.

[0046] The source gas for supplying ion species includes a gas containing boron element, wherein the boron element gas in the source gas for supplying ion species includes BF3, and the multivalent boron ions include both divalent boron ions and trivalent boron ions.

[0047] In another embodiment, the source gas for supplying ion species uses a gas containing phosphorus instead of a gas containing boron. The phosphorus gas in the source gas for supplying ion species includes PH3, and the multivalent phosphorus ions include both divalent phosphorus ions and trivalent phosphorus ions.

[0048] In another embodiment, the source gas for supplying ion species uses a gas containing arsenic instead of a gas containing boron. The arsenic gas in the source gas for supplying ion species includes AsH3, and the multivalent arsenic ions include both divalent arsenic ions and trivalent arsenic ions.

[0049] The above description is only a preferred embodiment of the present invention and does not limit the scope of patent protection of the present invention. Any equivalent transformation made by using the contents of the description and drawings of the present invention, directly or indirectly applied in other related technical fields, is also included in the scope of protection of the present invention.

Claims

1. A dedicated ion source for multivalent ion implantation, characterized in that: include: a first gas supply source for supplying a source gas of an ion species; An ion generator having a primary reaction arc chamber generates an ion beam containing monovalent ions of the source gas supplied by the first gas supply source using the source gas supplied by the first gas supply source; a second gas supply source; The secondary reaction arc chamber generates multivalent ions of the source gas supplied by the first gas supply source by colliding an ion beam containing monovalent ions of the source gas supplied by the first gas supply source with the source gas supplied by the second gas supply source to generate charge exchange.

2. The ion source dedicated for multivalent ion implantation according to claim 1, wherein: The source gas for supplying ion species includes a gas containing boron, phosphorus, or arsenic.

3. The ion source dedicated for multivalent ion implantation according to claim 2, wherein: The gas containing boron elements in the source gas for supplying ion species includes BF3, or the gas containing phosphorus elements in the source gas for supplying ion species includes PH3, or the gas containing arsenic elements in the source gas for supplying ion species includes AsH3.

4. The ion source dedicated for multivalent ion implantation according to claim 1, wherein: The source gas of the second gas supply source includes helium.

5. The ion source dedicated for multivalent ion implantation according to claim 2 or 3, characterized in that: The polyvalent boron ions include both divalent boron ions and trivalent boron ions, or the polyvalent phosphorus ions include both divalent phosphorus ions and trivalent phosphorus ions, or the polyvalent arsenic ions include both divalent arsenic ions and trivalent arsenic ions.

6. The ion source dedicated for multivalent ion implantation according to claim 1, 2, 3 or 4, wherein: The first gas supply source is connected to the primary reaction arc chamber through the primary reaction arc chamber gas supply pipe.

7. The ion source dedicated for multivalent ion implantation according to claim 6, wherein: The gas outlet of the gas transmission pipe of the first-stage reaction arc chamber, the gas outlet of the first-stage reaction arc chamber and the gas outlet of the second-stage reaction arc chamber are located on the same longitudinal axis.

8. The ion source dedicated for multivalent ion implantation according to claim 1, 2, 3 or 4, characterized in that: The ion generator includes a reflector installed on one side of the primary reaction arc chamber, a cathode provided on the other side opposite to the reflector, a filament installed in the cathode, the filament connected to the ion source filament clamp, the cathode connected to the ion source cathode clamp, and the reflector connected to the ion source reflector clamp. The ion source cathode clamp and the ion source reflector clamp are connected by an equipotential connecting strip.

9. The ion source dedicated for multivalent ion implantation according to claim 1, 2, 3 or 4, characterized in that: The second gas supply source is connected to the secondary reaction arc chamber through the secondary reaction arc chamber gas supply pipe.

10. A method for using a dedicated ion source for multivalent ion implantation, for preparing an ion beam of multivalent ions of a source gas supplied by a first gas supply source, wherein the dedicated ion source for multivalent ion implantation is the dedicated ion source for multivalent ion implantation according to any one of claims 1 to 9, characterized in that: The following steps are involved: a. utilizing a source gas supplied by a first gas supply source to generate an ion beam comprising monovalent ions of the source gas supplied by the first gas supply source; b. An ion beam containing monovalent ions of the source gas supplied by the first gas supply source, generated by the ion generator, collides with the source gas supplied by the second gas supply source to exchange charges, thereby generating polyvalent ions of the source gas supplied by the first gas supply source.

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