TW502341B - Method for preventing nitrogen contamination in silicon ions implantation - Google Patents

Abstract

A method for preventing contamination of N2+ molecules during silicon ion implantation comprises at least: increasing the current of source magnet during silicon ion implantation to dissociate N2 into N+. As a preferable example, it is necessary for the ratio of N2+/N+ to be less than 1, and an energy analyzer is used to select silicon ions to perform silicon ion implantation.

Description

502341 V. Description of the invention α) Field of the invention: The present invention discloses an ion implantation related to silicon ions, and more particularly, a method for preventing nitrogen ion implantation from contaminating silicon ions. Background of the Invention: In the integrated circuit manufacturing process, most of the silicon substrates are silicon, and conductive impurities are appropriately doped to form p-type or n-type doped regions. If the diffusion area is replaced by a code or BF2 ^ and a complex crystal conductor layer is crossed across the diffusion area, a basic P-type transistor is formed. In contrast, if the diffusion region is doped with arsenic or phosphorus ions and a polycrystalline silicon conductor layer crosses the diffusion region, a basic Γ1 type transistor is formed. When the transistor channel length enters the deep sub-micron era, not only the gate oxide thickness becomes thinner, but the source / drain interface is only a few hundred angstroms. Therefore, if the source / drain contact forms titanium silicide in order to reduce the impedance, the first problem that needs to be faced is the titanium silicide reaction that consumes the silicon substrate and affects the source / drain interface. The ion mixing (i ο η-mi Xing) technology in the titanium metal layer is a common countermeasure to solve the above problems. In addition, another case where titanium silicide is formed after the source / drain is implanted is often used before the source / drain is implanted. The silicon ion bombardment is also used to pre-amorphize the semiconductor substrate. -amorous) to prevent channel effects, the main reason is that silicon ions will not affect η or ρ-type electrical properties.

502341 V. Description of the invention (2) The sub-quantity is 2 8. However, similar to the situation encountered in general ion implantation, silicon ion implantation also has a problem of contamination. Common pollution in ion implanters is mainly from the same element. Divalent and trivalent ions cannot be separated. Or due to the ionic group colliding with nitrogen in a vacuum to dissociate and form positively charged nitrogen molecules (N 2+). To solve the problem of N 2 pollution, generally, the path of the ion krypton (b e a m 1 i n e p a t h) is shortened to reduce the chance of collision. The other is to use an energy filter. The most disturbing problem for ion implantation engineers is the N 2 pollution of silicon ionization vegetation. In general, N 2 fishing pollution has an impact on the resistance of silicon ion implantation. For the titanium silicide layer, its resistance is related to the integrity of the titanium silicide. The higher the amount of Shixi ion implantation, the better the integrity of the titanium metal Shixi compounds, and the lower the resistance value. However, the degree of vacuum becomes worse when planting. The worse the quality of the titanium metal oxide layer, the above facts show that the pollution of N 2 does affect the quality of the titanium metal oxide layer. Unfortunately, the atomic weight of silicon atoms is 28 grams, which is the same as that of N2f, which is a positively charged nitrogen molecule. Nitrogen is the highest gas in the atmosphere. Even in a vacuum environment, nitrogen will still be dissociated by ion groups to N 2+. Using an analyzing magnet, it is difficult to separate Shi Xi ions from nitrogen. Therefore, as far as conventional ion implanters are concerned, N 2 ions are an unavoidable source of silicon ion implantation pollution. In addition, nitrogen is most commonly used to open vacuum valves (vent)

502341 V. Gas of invention description (3), and other gases that control ambient pressure. Of course, the use of argon ions (Ar +) instead of N as a control gas is a means to reduce the implantation of silicon ions contaminated by N 2. Another method is to perform a dummy run for 12 hours after vacuuming, that is, to replace the real test piece with a control piece. In essence, however, the silicon source has been mixed with nitrogen due to atmospheric conditions. In the ion implantation machine, it turns into N 2+ again. Therefore, the above two schemes still cannot completely solve the above-mentioned pollution problems. In view of this, the present invention will propose a method to improve the above pollution problem. Object and Summary of the Invention: The object of the present invention is to provide a simple and easy-to-use ion implantation machine angle correction tool to provide fast and accurate machine zero-degree angle adjustment. The invention discloses a method for preventing contamination by positively charged nitrogen molecules (N 2+) during stone ion implantation. The method at least comprises: increasing an ion source magnet (sourmagnet) current during silicon ion implantation so that N 2 dissociates into a positron-containing nitrogen atom (N +). In a preferred embodiment, the magnetic current of the ion source should be at least higher than 30 amperes, so that the N 2 VN + content ratio is less than 1. Finally, the silicon ion plasma is screened by an energy analyzer to perform silicon ion distribution. plant. Detailed description of the invention:

502341 V. Description of the invention (4) As stated in the background of the invention, the change in the degree of vacuum will affect the pre-amorphization of silicon, and then the quality of the titanium silicide shows that the pollution of N 2 cannot be ignored. The mass analysis magnet (a n a 1 y z i n g m a g n e t) of the traditional ion implanter cannot filter N 2+ from the source of Si. In order to solve the above problems, we must first understand the ion implantation machine, the source of ion implantation, and the accelerated generation process of ion plasma. Please refer to the sectional view of the ion implanter shown in Figure 1, which can be divided into several sections for description. The initial section is part 10 of the ion source (s0 u r c e), which uses the electrons emitted by the hot filament and increases its radius of gyration with the source magnet to increase the chance of impacting the source gas to generate a positively charged plasma. An ion extraction electrode plate is used to generate focused ions and attract them. The positively-charged focused ion plutonium reuse middle section 20 includes an analyzing magnet, which utilizes the difference in the radius of the magnetic field rotation radius to screen the ion plutonium to be implanted. The last is the first paragraph 30. The accelerating voltage or decelerating voltage includes a horizontal and vertical position calibrator, and the electric mass passing through the mass analysis magnet will pass the accelerating voltage or decelerating voltage, and then accurately calculate the implanted ions through the faradaycup. Dose, implant the ion plutonium into the target wafer. The inventors believe that it is not enough to rely solely on mass analysis to make ions pure, because N 2 and Si + have the same atomic weight of 2 8 and N 2+ should be blocked at the source of silicon ions. Therefore, the inventor came up with an important idea. Please refer to Figure 2. Figure 2 shows an arc chamber 35,

502341 V. Description of the invention (5)

Including a gas source injection port 4 2, an evaporator inlet 43, and a filament 4 arc reaction chamber 3 5 is an ion source magnet (s 0 u r c e m a g n e t) 40. The hot filament 4 2 is used to generate electrons, which then impinge on the gas source injection port 4 2 and the gas inlet or evaporator inlet 4 3 is injected with a solid source vapor to knock out the secondary electrons and continue to impinge until the arc reaction chamber 3 5 generates a large amount of electrons. The ion source magnet 40 is used to generate a magnetic field. When the ion source magnet 40 is set to an appropriate current value, the electrons will travel in a convolutional manner like path A to increase the path and increase the free efficiency. . When the current of the ion source magnet 40 is set higher, the radius of the electrons will be reduced, and the travel path such as path B will be further increased. At this time, the probability of electron impact will increase significantly. The positively-charged nitrogen molecule N 2 is further decomposed into N +. In the present invention, a high-intensity ion source magnet is used to increase the probability of electron impact, and the positively-charged nitrogen molecule N 2 is further decomposed into Ν +. The atomic weight of N is only 14 grams. Therefore, the magnet cannot be analyzed by mass analysis, and the problem of nitrogen 25 deficient in silicon ions is prevented. Figure 3 shows the relationship between the magnetic current of the ion source and the ratio of N 2V N. The figure shows that when the magnetic current of the ion source is 10 amps, the ratio of N 2 VN + is about 2.5, and 2 2+ can make N 2+ / N ratio is less than 1. And as the magnetic current of the ion source further increases, N 2+ / N prostitutes with a value smaller than 1 are smaller and tend to be stable. The inventors have discovered that different ion sources (s0 u r c e) require different ion source magnetic currents to produce a maximum ion current of 0 (bean current). In order to comply with different ion sources (sources), the ion source magnetic current can be adjusted to more than 30 amps (inclusive) to obtain a stable and minimally polluted ion current.

502341

Page ο 502341 Brief description of the drawings The preferred embodiment of the present invention will be described in more detail in the following explanatory text with the following figures: Figure 1 shows a schematic diagram of an ion implantation machine. Figure 2 shows the relationship between the magnetic current of the ion source and the generated plasma path. Figure 3 shows the relationship between the ion source magnetic current and the value of N 2 V N 牝. Figure number comparison table: Ion source (s 〇 r c e) part 10 Mass analysis magnet (analyzing magnet) 20 Ion implanter front section 30 Ion source magnet 40 Arc reaction chamber 35 Filament 41 Gas source injection port 42 Evaporator inlet 43

Page 11

Claims (1)

502341 VI. Application Patent Scope 1. A method for preventing contamination by positively charged nitrogen molecules (N 2+) during silicon ion implantation, the method at least comprises: adding an ion source magnet (s 〇) during stone ion implantation. urcemagnet) to dissociate N 2 into positron-containing nitrogen atoms (N +), so that the N 2 V N + content ratio is less than 1; and filter with an energy analyzer to perform ion implantation. 2. The method according to item 1 of the patent application, wherein the above-mentioned ion source magnetic current is at least 30 amps. 3. The method according to item 1 of the patent application range, wherein increasing the current of the ion source magnet (s0 u r c e m a g n e t) increases the probability of collision of nitrogen molecules and radicals. Page 12