JP2005005328A - Impurity introduction method, impurity introduction apparatus, and semiconductor device formed using the same - Google Patents

Abstract

An impurity introduction method and an impurity introduction apparatus capable of high-precision control in introducing impurities into a substrate are provided.
A substrate to be processed is placed on a holding base and rotated by a rotary drive shaft. After the vacuum pump 6 is operated, gas exhaust by the vacuum pump 6 is stopped, and a certain amount of plasma generating substance (gas substance) in the measuring chamber 7 is introduced into the vacuum chamber 1 through the nozzle 14. A number of micro nozzles 19 are provided in the nozzle 14, and a spatially non-uniform gas flow 15 is generated in the vacuum chamber 1 through the micro nozzles 19 in accordance with the excitation intensity of plasma. Then, the plasma generating unit 2 is driven by the power source 3 to excite plasma of the gas substance introduced non-uniformly into the vacuum chamber 1, and the surface of the substrate 5 to be processed is exposed to plasma for a predetermined time.
[Selection] Figure 7

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an impurity introduction method, an impurity introduction apparatus, and a semiconductor device formed using the impurity introduction method, and more particularly to control of an impurity introduction profile in plasma doping.
[0002]
[Prior art]
In recent years, with the miniaturization of semiconductor devices, a technique for forming a shallow junction is required. In the conventional semiconductor manufacturing technology, a method is widely used in which impurities of various conductivity types such as boron (B), phosphorus (P), and arsenic (As) are ion-implanted into a semiconductor substrate surface with low energy.
Although a shallow junction of a semiconductor device is formed by using this ion implantation method, a shallow junction can be formed, but there is a limit to the depth that can be formed by ion implantation. For example, boron impurities are shallow and difficult to introduce, and in ion implantation, the depth of the introduction region is limited to about 100 nm from the substrate surface.
Therefore, in recent years, various doping methods have been proposed as techniques for enabling shallower junctions, and plasma doping techniques have attracted attention as being suitable for practical use. This plasma doping is a technique in which a reaction gas containing impurities to be introduced is plasma-excited and the substrate surface is irradiated with plasma to introduce impurities. According to this technique, a shallow junction with a depth of 70 nm can be formed even with boron impurities (see, for example, Non-Patent Documents 1 and 2).
[0003]
[Non-Patent Document 1]
Plasma doping technology: Fumiji Mizuno (Vol. 70, No. 12, p. 1458-1462 (2001)
[Non-Patent Document 2]
Performance of sub-0.1 micron pMOSFET doped by low-bias plasma doping: Reliable and enhanced performes of sub-0.1 μm pMOSFETs doped by low biased Plasma Doping, Damien Lenble et al. , P. 110, 2000.
[0004]
[Problems to be solved by the invention]
At present, miniaturization of semiconductor devices is progressing rapidly, and the design dimension in mass production is about to be 100 nm or less. On the other hand, the diameter of silicon wafers (semiconductor substrates) is increasing from 200 mmφ to 300 mmφ. Under such circumstances, a highly accurate control technique is required as follows in introducing impurities into the surface of a semiconductor substrate.
The first is a technique for stably controlling the formation of a shallow junction in which the depth in the vicinity of the substrate surface where impurities are introduced is 100 nm or less. The second is a technique for controlling the uniformity of impurity distribution in the substrate surface having a large diameter as described above.
[0005]
However, in the above ion implantation method, B ions or BF are introduced particularly when boron is introduced. ₂ There is a problem that it is difficult to reduce the acceleration energy of ions to a low energy of several keV, and it becomes difficult to form a shallow junction in which the depth of a future impurity introduction region is 100 nm or less. On the other hand, in the conventional plasma doping method, it is easy to set the energy of plasma ions to 100 eV or less, and as described above, it is possible to control a shallow junction having a depth of 50 nm or less. There is a problem that it is not yet sufficient to control the uniformity of the impurity distribution in the substrate surface.
[0006]
In addition, the customization of semiconductor device products is progressing, and it is indispensable to deal with the high-mix low-volume production. Here, in order to improve the production efficiency of a wide variety of products, a technique capable of freely controlling the amount of impurities introduced into the substrate surface when introducing impurities into the semiconductor substrate surface is very effective.
[0007]
However, in any of the above-described ion implantation and conventional plasma doping methods, it is difficult to freely control the amount of impurities introduced within the large-diameter substrate surface as described above. The above-described problem in introducing impurities is not limited to a semiconductor substrate on which a semiconductor device is formed, but also applies to a matrix substrate serving as a liquid crystal display substrate for forming a liquid crystal display device.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to provide an impurity introduction method and an impurity introduction apparatus capable of highly accurate control in introducing impurities into a substrate.
It is another object of the present invention to control the amount of introduced impurities and realize the introduction of impurities at a very shallow depth with high accuracy.
Another object of the present invention is to reduce the variation in impurity introduction depth or concentration depending on the position, and to introduce impurities to a uniform depth on a large-area substrate.
[0009]
[Means for Solving the Problems]
The impurity introduction method according to the present invention is an impurity introduction method in which a substance containing an impurity is plasma-excited and the excited impurity is introduced into a substrate so that at least a part of the plasma distribution can be offset. The distribution of the substance in the vicinity of the surface of the substrate is adjusted. That is, the distribution of the substance in the vicinity of the surface of the substrate is adjusted according to the distribution of the plasma.
[0010]
In other words, the distribution of the plasma itself, that is, the distribution of the resulting plasma (the distribution of ions, radicals, neutral particles, etc.) is offset according to the distribution of the plasma itself. Actually, a substance distribution near the substrate surface is adjusted based on simulation or actual impurity introduction result. To cancel at least part of the plasma distribution means to give a material distribution that changes the original plasma distribution, and to mean a material distribution that generates a plasma distribution that does not depend on the original plasma distribution. It shall be. Therefore, it is assumed here that not only the original plasma distribution is canceled and made uniform, but also a part that further expands the original plasma distribution is partially canceled.
[0011]
Alternatively, the impurity introduction method of the present invention includes a step of supplying the substance into the chamber after adjusting the distribution of the substance in the vicinity of the substrate surface to have a distribution according to the plasma distribution, Generating a plasma of the substance after the substrate surface is in an equilibrium state.
[0012]
In a normal plasma generator, power for plasma excitation such as high frequency or microwave has a limit in spatial uniformity. Therefore, the impurity introduction method of the present invention proposes a method capable of obtaining an impurity distribution that does not depend on the degree of spatial uniformity by controlling the distribution of the plasma-excited substance.
For example, a material that is plasma-excited is supplied to offset this non-uniformity. This makes it possible to introduce impurities with very high uniformity in a very shallow region from the substrate surface. Even in the case of a substrate having a large diameter such as a semiconductor substrate or a liquid crystal display substrate, it becomes easy to control the uniformity of impurity distribution.
[0013]
The present invention makes it possible to control the profile with high accuracy in introducing impurities. Plasma generated as a result of plasma excitation after the substance is brought into an equilibrium state on the surface of the substrate, power distribution of plasma excitation, and the like. Adjusting the material on the surface of the substrate so as to offset the distribution of ions, radicals, and neutral particles, and adjusting the material on the surface of the substrate so that the plasma is distributed stepwise on the surface of the substrate, Alternatively, including these combinations, these methods enable plasma doping of a desired profile.
[0014]
Further, in the impurity introduction method of the present invention, in which the substance containing impurities is plasma-excited and the excited impurities are introduced into the substrate, the spatial distribution is arbitrary in the chamber in which the substrate is disposed. The substance is supplied, and the substance having this spatial distribution is plasma-excited to introduce impurities.
[0015]
In this way, regions having different impurity distributions can be freely formed in the substrate by one impurity introduction process. Accordingly, in the formation of the semiconductor integrated circuit, a mask alignment margin is not required, and further miniaturization and higher integration are possible. In addition, semiconductor devices having various different performances can be formed on one substrate. In addition, the response to the high-mix low-volume production of semiconductor device products becomes rapid, and the production efficiency of the high-mix products improves. Here, the impurity profile includes an impurity distribution in the depth direction in addition to the in-plane impurity distribution.
[0016]
In the present invention, plasma is generated in a state where supply of the substance is stopped. Plasma is generated in a state where supply and discharge of the substance are stopped. Plasma is generated after the substance supplied into the chamber in which the substrate is placed is in an equilibrium state on the surface of the substrate. Alternatively, after the flow rate of the substance becomes 100 meV or less in terms of conversion rate, a measure such as generating plasma is taken.
[0017]
Thereby, the flow of the substance to be supplied in the chamber can be stabilized quasi-statically. By exciting this stable substance with plasma, the impurity distribution on the substrate surface is further improved. In this way, the fluctuation component generated by the flow of the substance is reduced, and only the disturbance due to the plasma is suppressed. Setting the flow rate to 100 meV or less in terms of the conversion speed means that the flow rate is almost at room temperature, and the distribution before the plasma formation can be maintained without causing a large distribution fluctuation during the plasma formation.
[0018]
In the present invention, plasma is generated after a certain amount of the substance is supplied into the chamber. Here, a certain amount of the substance to be supplied is determined according to the amount of impurities introduced into the substrate.
[0019]
By doing so, it is possible to control the amount of impurities introduced into the substrate surface so as to be a desired set amount. In addition, extremely shallow introduction can be controlled with high accuracy, and extremely shallow junctions can be formed with high accuracy.
[0020]
In the present invention, the substance is supplied into the chamber in which the substrate is disposed through a micro nozzle. Here, the substance is a gas containing impurities. Alternatively, fine particles or fine droplets containing impurities may be used. A large number of micro nozzles having a fine opening diameter are arranged, and the flow rate can be changed by controlling each micro nozzle independently.
[0021]
Thereby, the spatial distribution of the substance in the chamber in which the substrate is arranged can be controlled with high accuracy, and the control of the impurity amount on the substrate surface and the free control of the spatial distribution are further promoted.
[0022]
The impurity introduction apparatus of the present invention is an impurity introduction apparatus for plasma-exciting a substance containing impurities, and introducing the impurities into the substrate from the excited substance, the chamber in which the substrate is disposed, The apparatus includes a means for supplying a certain amount of the substance into the chamber, a means for evacuating the inside of the chamber, and a plasma generating means for converting the certain amount of substance into plasma. The means for supplying a certain amount of the substance has a mechanism for measuring and storing the substance, and this mechanism controls the volume, pressure, and temperature of the storage container to hold the substance at a certain amount. ing. Furthermore, the storage container is configured to store an amount of a substance corresponding to the amount of impurities introduced into the substrate.
[0023]
With this configuration, single-wafer processing can be performed in a short time for introducing impurities into a substrate which is a large-diameter semiconductor substrate or liquid crystal display substrate. For this reason, the mass production capability of the semiconductor device or the liquid crystal display device is improved and the production cost can be reduced. The substance is gas, fine particles, or fine droplets.
[0024]
For example, B ₂ H ₆ , BF ₃ , AsH ₃ , PH ₃ One of these. As the fine particles or solid, any of B, As, P, Sb, In, and Al can be used. Here, the droplet means a solution or turbidity of these fine particles and gas. In addition, the surface may be covered so as to get wet.
[0025]
Further, the timing of generating plasma may be performed based on the simulation result of the impurity concentration profile in the vicinity of the substrate surface. In addition, instead of simulating the impurity concentration profile, at least one selected from the group of gas, fine particle or fine droplet flow velocity, number of gas molecules, and pressure was measured, and the standard deviation reached less than 2%. In this case, plasma may be generated.
[0026]
The present invention makes it possible to control the profile with high accuracy in introducing impurities. Plasma generated as a result of plasma excitation after the substance is brought into an equilibrium state on the surface of the substrate, power distribution of plasma excitation, and the like. Adjusting the material on the surface of the substrate so as to offset the distribution of ions, radicals, and neutral particles, and adjusting the material on the surface of the substrate so that the plasma is distributed stepwise on the surface of the substrate, Alternatively, including these combinations, these methods enable plasma doping of a desired profile.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. This impurity introduction apparatus is characterized in that the impurity introduction profile can be adjusted by adjusting the distribution of substances in the vicinity of the surface of the substrate. FIG. 1 is a cross-sectional view schematically showing an impurity introduction apparatus of the present invention, and FIG. 2 is a main part of the apparatus for explaining the impurity introduction method of the present invention.
[0028]
As shown in FIG. 1, this apparatus includes a vacuum chamber 1, a plasma generator 2 and a power supply 3 for supplying power thereto. A holding table 4 is provided in the vacuum chamber 1 and a substrate 5 to be processed is placed thereon. Is done. And the vacuum pump 6 which adjusts the vacuum degree of the vacuum chamber 1 is provided. In this way, the main body of the impurity introduction device is constructed. This device is a single wafer type and enables rapid processing so that the entire volume, particularly the volume of the vacuum chamber 1 is minimized. It is important to configure. Here, the plasma generation unit 2 is a helicon wave plasma source, an ECR (Electron Cyclotron Resonance) plasma source, or the like, and a plasma generation source with a high response speed is preferable. Such a plasma source plasma-excites a substance containing impurities to be introduced into the substrate 5 to be processed, here a gas.
[0029]
In the supply system of the gas substance containing impurities, metering chambers 7a and 7b are provided, and the gas substance is supplied from the nozzle 8 to the vacuum chamber 1 through the metering chamber 7a or 7b. Here, the measuring chambers 7a and 7b are configured to store a certain amount of gas substance. This storage amount is determined by the volume of the measuring chambers 7a and 7b, the gas temperature and the gas pressure, and is monitored by the thermometers T1 and T2 and the pressure gauges P1 and P2, respectively. Temperature and pressure are controlled stably. The measuring chamber will be further expanded as necessary.
[0030]
The gas supply to the measurement chamber is performed from the supply device 9 through the mass flow controller 10, and the amount of gas supplied to the measurement chambers 7 a and 7 b can be strictly defined by pressure control in the pressure regulator 10. Here, the gas is B ₂ H ₆ , BF ₃ , AsH ₃ , PH ₃ Alternatively, these are diluted with an inert gas.
[0031]
The impurity introduction apparatus of the present invention is a device that excites a substance containing an impurity into a plasma to dope the substrate with the impurity. However, the impurity introducing apparatus is a RIE (Reactive Ion Etching) that continuously generates a plasma by supplying a reaction gas to a reaction chamber. Unlike the dry etching or CVD (Chemical Vapor Deposition), the impurity introduction apparatus of the present invention can convert a certain amount of gas corresponding to the impurity introduction amount (dose amount) into the substrate with high accuracy. With this configuration, it is possible to introduce impurities at a very shallow depth, and to control the depth of impurity introduction with high accuracy.
[0032]
In addition, impurities can be introduced into the substrate, which is a large-diameter semiconductor substrate, by rapid processing, and single wafer processing can be performed in a short time. For this reason, it becomes possible to form a highly accurate and highly reliable semiconductor device with high productivity. Further, when used for a liquid crystal display substrate, the mass production capability of the liquid crystal display device is improved, and the production cost can be reduced.
[0033]
In the impurity introduction apparatus shown in FIG. 1, the holding table 4 may be made of a conductor, and a direct current (DC) power source or an RF power source as a high frequency power source may be attached to the holding table 4. Here, the RF power source is a high frequency power source having a frequency of 100 kHz to 10 MHz. A DC potential in the range of several eV to 1 keV can be formed between the plasma generated by these power supplies and the substrate 5 to be processed. Further, a mechanism capable of rotating the holding table 4 may be attached. By applying a rotation of about 10 rpm, for example, on the horizontal surface to the substrate 5 to be processed by this rotating mechanism, the uniformity of the impurity dose amount in the surface of the substrate to be processed 5 is further improved.
[0034]
In addition to substances that contain impurities at room temperature and pressure as described above, substances containing impurities include solids such as fine particles of B, As, P, Sb, In, Al, and Si, and the impurities described above. Or a liquid in which solid fine particles are surrounded by a liquid may be used. However, in this case, the supply system shown in FIG. 1 is slightly different, but it is necessary that a certain amount of a substance containing impurities can be supplied.
[0035]
Next, the impurity introduction method of the present invention will be described with reference to FIGS. Here, the same parts as those shown in FIG. FIGS. 3A to 3C are timing charts showing driving states of the vacuum pump 6, the gas supply nozzle 8, and the plasma excitation power source 3, respectively. As shown in FIG. 2, for example, a silicon wafer having a diameter of 300 mmφ is placed on the holding table 4 as the substrate to be processed 5 and fixed by electrostatic adsorption. Then, the vacuum pump 6 is operated to set the degree of vacuum in the vacuum chamber 1 to 10 ^-3 After setting the pressure to about Pa, gas exhaust by the vacuum pump 6 is stopped.
[0036]
After such a state, the above-mentioned fixed amount of gas substance in the measuring chambers 7 a and 7 b is supplied into the vacuum chamber 1 through the nozzle 8. Here, since the vacuum pump 6 is in a stopped state, the flow rate of the gas substance flowing into the vacuum chamber 1 decreases with time. Then, when the flow of the gas substance in the vicinity of the surface of the substrate 5 to be processed or in the vacuum chamber 1 is in an equilibrium state and is stabilized in a quasi-static state, the plasma generator 2 is driven by the power source 3 to drive the vacuum chamber. The gas substance filling 1 is plasma-excited (section P: see FIG. 3). Here, when the flow rate of the gas substance becomes a predetermined value (converted value: 100 meV) or less by actual measurement or simulation, the plasma substance 2 is driven to fill the vacuum chamber 1. Is excited by plasma.
[0037]
In this way, the plasma 12 having a uniform spatial distribution is generated, and the surface of the substrate to be processed 5 is exposed to the plasma 12 for a predetermined time (for example, 1 minute). Here, the plasma 12 is a thermal non-equilibrium plasma in which the electron temperature and the ion temperature are extremely different. Usually, the ion temperature is several tens of degrees and the thermal kinetic energy is small.
[0038]
A substance containing impurities to be introduced is introduced into the surface of the substrate to be processed 5 or inside thereof in the form of adsorption or low energy (a few eV to 1 keV as described above) by plasma irradiation onto the substrate to be processed 5 described above. The Here, in the adsorption form, the substance is physically adsorbed on the surface of the substrate 5 to be treated, and active species such as neutral radicals of the substance generated by the plasma excitation are mainly chemically adsorbed.
[0039]
In the ion implantation mode, the ionized impurity material in the substance is partially implanted into the surface by thermal motion (however, as described above, the thermal kinetic energy is small and the amount is small). ) And the plasma 12 and an ion sheath generated on the surface of the substrate 5 to be processed or a DC voltage such as a so-called self-bias is accelerated and implanted.
[0040]
Thereafter, although not shown in FIG. 1, RTA (rapid heat treatment) is performed in another chamber having a multi-chamber configuration. Thus, in the impurity introduction method of the present invention, uniform and shallow impurity introduction can be performed near the surface of the substrate 5 to be processed. In addition, in order to supply a certain amount of gas substance into the vacuum chamber 1, it is possible to control the amount of impurities introduced into the substrate surface to be a desired set amount.
[0041]
(Second Embodiment)
In the first embodiment, as shown in the timing chart of FIG. 3, plasma excitation is performed while supplying a substance that becomes an impurity. However, in this embodiment, the timing of plasma excitation is changed, and FIG. As shown in the timing chart, plasma excitation is performed after the supply of impurities is stopped.
[0042]
FIG. 4A shows a timing chart of the vacuum pump. That is, as described above, the degree of vacuum in the vacuum chamber 1 is 10 ^-3 After the pressure reaches about Pa, gas exhaust is stopped (FIG. 4B). Then, after supplying a predetermined amount of the gas substance in the measuring chambers 7a and 7b through the nozzle 8 into the vacuum chamber 1, the supply is stopped by an electromagnetic valve (not shown).
[0043]
Thereafter, the plasma generator 2 is driven to generate the plasma 12 (FIG. 4C). Thereafter, impurities are introduced into the surface portion of the substrate 5 to be processed during the section P in the same manner as described above. In such a method, the measuring chambers 7a and 7b are not necessarily required. This is because even if the gas substance is directly introduced into the vacuum chamber 1 from the supply device 9 shown in FIG. 1, the amount of the gas substance can be strictly defined by the mass flow controller 10.
Also in this case, as described above, the gas substance is plasma-excited when the flow of the gas substance in the vacuum chamber 1 is in an equilibrium state and stabilized in a quasi-static state.
[0044]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.
This embodiment differs from the first and second embodiments in that the impurity-containing gas introduced into the vacuum chamber 1 is intentionally given a predetermined spatial distribution, and the impurity dose amount to the substrate 5 to be processed is reduced. It is characterized by improving uniformity. FIG. 5 is a schematic cross-sectional view of the main body of the impurity introduction apparatus of the present invention. Here, the same parts as those in the first embodiment are denoted by the same reference numerals.
[0045]
This apparatus is characterized in that a nozzle 14 having a large number of jet outlets is connected to a metering chamber and adjusted so as to have a distribution in the amount of ejection of gas containing impurities from the nozzle 14.
[0046]
In FIG. 5, as described in the first embodiment, a vacuum chamber 1, a plasma generator 2 and a power supply 3 for supplying power are provided, and a holding table 4 is provided in the vacuum chamber 1. A substrate 5 to be processed is placed. Here, a rotation drive shaft 13 is attached to the holding base 4 so as to rotate in the direction of the arrow.
[0047]
A vacuum pump 6 that adjusts the degree of vacuum in the vacuum chamber 1 is provided. As shown in FIG. 5, the measuring chamber 7 described above is connected to a nozzle 14 having a large number of jets, and the nozzle 14 is inserted into the vacuum chamber 1. Here, the nozzle 14 may be tubular or may have a planar spread. Here, the jet outlet may be formed of an assembly of micro nozzles having a diameter of the order of μm. In introducing gas from the measuring chamber 7, a spatially non-uniform gas flow 15 can be generated as shown by the distribution of arrows in FIG.
By controlling the gas supply amount from the nozzles in this way, it is possible to cancel the plasma variations caused by various conditions such as the position and form a uniform distribution.
[0048]
(Fourth embodiment)
Next, an impurity introduction apparatus according to a fourth embodiment of the present invention will be described. As shown in FIG. 6, this impurity introducing apparatus is different from helicon wave plasma and ECR plasma generation, and generates plasma by applying a high frequency of 13.56 MHz to parallel plate electrodes. In FIG. 5, as described in the first embodiment, a holding table 4 is provided in the vacuum chamber 1 and a substrate 5 to be processed is placed thereon. Here, a high-frequency power source 16 is attached to the holding base 4 made of a conductor to form one electrode of parallel plate electrodes. A counter electrode 17 and a vacuum pump 6 for adjusting the degree of vacuum of the vacuum chamber 1 are provided.
[0049]
The counter electrode 17 described above is provided with a large number of jets and is connected to the measuring chamber 7 through the gas introduction pipe 18. Here, the jet outlet is composed of an assembly of micro nozzles having a diameter of the order of 10 μm. Then, in introducing the gas substance from the measuring chamber 7 to the vacuum chamber 1, a spatially non-uniform gas flow 15 can be generated as shown in FIG. In this example, since the electric field is weaker in the vicinity of the peripheral portion of the holding table 4 and the counter electrode 17 constituting the electrode than in the central portion, the plasma distribution is adjusted by adjusting the gas flow 15 at the peripheral portion to have a higher concentration. Becomes uniform in the substrate plane.
[0050]
Note that a magnetic field parallel to the parallel plate electrodes may be applied by a permanent magnet or the like. Even in this case, high-density plasma can be easily generated. The magnetic field shown in FIG. 6 represents this, and also shows the electric field by a high frequency.
[0051]
(Fifth embodiment)
Next, a fifth embodiment will be described with reference to FIGS. Even in this case, the method described in the first embodiment is basically used, but this embodiment is characterized in that the introduction of the gas substance has a spatial distribution as described above. Usually, the electromagnetic energy density of high frequency or microwave used for plasma excitation has a spatial distribution and is not necessarily uniform, so that the generated plasma has a spatial distribution.
[0052]
Therefore, in this embodiment, the supply of the gas substance is given a spatial distribution so as to cancel out the plasma spatial distribution (hereinafter referred to as a plasma distribution) caused by the above reason. Here, the plasma distribution can be measured by a known plasma emission spectroscopic measurement, a Faraday cup, a Langmuir probe, or the like.
[0053]
As shown in FIG. 7, for example, the substrate 5 to be processed is placed on the holding table 4, fixed by electrostatic attraction, and rotated by the rotation drive shaft 13. For example, it is rotated horizontally at 20 rpm. Then, the vacuum pump 6 is operated, and the degree of vacuum in the vacuum chamber 1 is 10 ^-3 After setting the pressure to about Pa, gas exhaust by the vacuum pump 6 is stopped. After such a state, the above-described constant amount of plasma generating substance in the measuring chamber 7 is introduced into the vacuum chamber 1 through the nozzle 14. Here, a number of micro nozzles 19 are provided in the nozzle 14, and a spatially non-uniform gas flow 15 is generated in the vacuum chamber 1 through the micro nozzles 19. Then, when the flow of the substance for generating plasma in the vicinity of the surface of the substrate 5 to be processed or in the vacuum chamber 1 is in an equilibrium state and stabilized in a quasi-static state, the plasma generator 2 is driven by the power source 3. The plasma generating substance (gas substance) filling the vacuum chamber 1 is plasma-excited.
[0054]
For example, when the flow rate of the gas substance becomes a predetermined value (converted value: 100 meV) or less, the plasma generation unit is driven to plasma-excite the gas substance introduced nonuniformly into the vacuum chamber 1. By the plasma excitation, the gas flow 15 is adjusted so that a large amount of gas substance exists in a space having a low electromagnetic energy density and a small amount of gas substance exists in a space having a high electromagnetic energy density. Then, the surface of the substrate 5 to be processed is exposed to plasma for a predetermined time (for example, 1 minute). After that, the same processing as described in the first embodiment is performed.
[0055]
This result will be described with reference to FIG. 8. As shown in FIG. 8A, the plasma distribution is generated from the spatial distribution of the electromagnetic energy density of the high frequency or microwave used for plasma excitation. That is, the plasma distribution is normally a concentric distribution shape when viewed from the rotating substrate 5 to be processed. Therefore, a plasma generating substance (gas substance) shown in FIG. 8B is provided so as to cancel out the resulting plasma distribution (ion, radical, and neutral particle distribution) due to the power distribution of plasma excitation. The spatial distribution of
[0056]
Here, the spatial distribution may be in the vicinity of the surface of the substrate 5 to be processed, or in the vacuum chamber 1. The spatial distribution of such a gas substance is obtained from a simulation or trial experiment of a gas flow that takes into account so-called thermal motion. Here, also in this case, the spatial distribution of the gas substance viewed from the rotating substrate 5 to be processed is shown. When the gas substance having such a spatial distribution is plasma-excited, as shown in FIG. 8C, a plasma having a uniform spatial distribution is generated when viewed from the substrate 5 to be processed. Will be exposed to various plasmas. In this way, it is possible to introduce impurities uniformly within the surface of the substrate 5 to be processed. Further, the supply of the gas substance through the micro nozzle as described above can control the spatial distribution of the substance in the chamber in which the substrate is arranged with high accuracy.
[0057]
As described in the first embodiment, impurities introduced by plasma irradiation to the substrate 5 to be processed are introduced in an adsorption form or a low energy ion implantation form. Here, in the adsorption form, active species such as neutral radicals are chemically adsorbed. In the ion implantation mode, the ionized substance is implanted by being accelerated by a DC voltage such as plasma and an ion sheath generated on the surface of the substrate 5 or so-called self-bias. The results shown in FIGS. 8A to 8C show that the introduction of impurities in the adsorption form can be adjusted by controlling the spatial distribution of the gas substance.
[0058]
(Sixth embodiment)
Next, an impurity introduction method according to the sixth embodiment will be described. In this embodiment, unlike the third embodiment, the gas substance introduced into the vacuum chamber 1 is intentionally given a predetermined spatial distribution, and the impurity dose to the substrate 5 to be processed is not uniform in the plane. It is a case where it controls to become. In this case, the impurity introduction apparatus may be the same as that described in the second embodiment.
[0059]
In the main body of the impurity introduction apparatus shown in FIG. 9, for example, the substrate 5 to be processed is placed on the holding table 4 in the vacuum chamber 1 and fixed by electrostatic adsorption. And the vacuum pump 6 provided in the position of the lower left part of the vacuum chamber 1 is actuated as shown in the figure. The gas substance to the vacuum chamber 1 is introduced from the measuring chamber 7 through the nozzle 8 installed at the upper right end of the vacuum chamber 1.
After the gas material flow from the upper right to the lower left is formed in the vacuum chamber 1 in this way, the plasma generator 2 is driven by the power source 3 to plasma-excite the gas material introduced non-uniformly into the vacuum chamber 1. .
[0060]
In this way, the deflection plasma 20 is generated in which the plasma density decreases from right to left as schematically shown by the oblique lines in FIG. Then, the surface of the substrate to be processed 5 is exposed to the deflected plasma 20 for a predetermined time (for example, 10 seconds). After that, the same processing as described in the first embodiment is performed.
[0061]
This result will be described with reference to FIG. FIG. 9 shows the impurity distribution in the silicon wafer surface after introducing boron impurities into a 300 mmφ silicon wafer (substrate 5 to be processed). A sheet resistance distribution is shown on the substrate 5 to be processed. The sheet resistance increases in the direction of the arrow in FIG. Here, the upper part of the substrate 5 to be processed shown in FIG. 10 corresponds to the right hand side in FIG. 9, and the lower part of the substrate to be processed 5 shown in FIG. 10 corresponds to the right hand side in FIG. Thus, by providing a spatial distribution of the gas substance in the vacuum chamber 1, it is possible to introduce impurities having a desired non-uniformity within the surface of the substrate 5 to be processed.
[0062]
FIG. 11 shows transistor characteristics after introducing impurities having nonuniformity as shown in FIG. 10 and performing channel doping for MOSFETs. The relationship between drain current and drain voltage when the gate voltage is constant is shown. Show. Here, X and Y in the figure correspond to the MOSFETs of the semiconductor chip at the X and Y positions shown in FIG. 10, respectively. As described above, it is possible to manufacture a large number of semiconductor chips having MOSFETs having different characteristics by introducing impurities into the substrate 5 to be processed once.
[0063]
(Seventh embodiment)
Next, another impurity introduction method according to the seventh embodiment will be described. The impurity introducing apparatus in this case is the same as that described in the third embodiment shown in FIG. However, in this case, there is no rotation drive shaft 13 and the substrate 5 to be processed is not rotated. In the main body of the impurity introduction apparatus shown in FIG. 11, for example, the substrate 5 to be processed is placed on the holding table 4 in the vacuum chamber 1 and fixed by electrostatic adsorption. Then, the vacuum pump 6 is operated to set the degree of vacuum in the vacuum chamber 1 to 10 ^-3 After setting the pressure to about Pa, gas exhaust by the vacuum pump 6 is stopped.
[0064]
Then, a substance for generating plasma (gas substance) in the measuring chamber 7 is introduced into the vacuum chamber 1 through the nozzle 14. Here, a number of micro nozzles 19 are provided in the nozzle 14, and a spatially non-uniform gas flow 15 is generated in the vacuum chamber 1 through the micro nozzles 19. Then, the plasma generator 2 is driven by the power source 3 to excite the plasma of the gas substance introduced non-uniformly into the vacuum chamber 1, and the surface of the substrate 5 to be processed is exposed to the plasma for a predetermined time (for example, 10 seconds). . After that, the same processing as described in the first embodiment is performed.
[0065]
As a result, as shown in FIG. 13, plasma having a step-shaped plasma density is generated in the vacuum chamber 1. That is, it is possible to generate plasma that decreases stepwise from the left side to the right side of the substrate 5 to be processed. In this case, the supply of the gas substance through the micro nozzle can control the spatial distribution of the substance in the chamber in which the substrate is arranged with high accuracy. In addition, the control of the amount of impurities on the substrate surface and the free control of its distribution are further promoted.
For this reason, it becomes possible to introduce non-uniform impurities with higher accuracy than in the case shown in FIG. In addition to the channel dope of the MOSFET, the formation of the diffusion layer serving as the source / drain region and the formation of the well layer can be realized with high accuracy.
[0066]
In the seventh embodiment of the present invention, since it is easy to freely control the amount of impurities introduced in the substrate surface when introducing impurities into the semiconductor substrate surface, regions having different impurity distributions are formed in the same substrate. Can be freely formed by a single impurity introduction treatment. Accordingly, in the formation of the semiconductor integrated circuit, a mask alignment margin is not required, and further miniaturization and higher integration are possible. In addition, the response to semiconductor device products of high-mix low-volume production is quick. Further, in the trial manufacture of a semiconductor device, a semiconductor chip in which impurities are introduced into a single silicon wafer under a number of different conditions can be formed, so that the optimization of semiconductor device manufacturing is quickened. In addition, it is possible to speed up the response to customer needs in the manufacture of semiconductor devices.
[0067]
(Eighth embodiment)
In the above embodiment, the semiconductor substrate on which the semiconductor device is formed has been described as the substrate to be processed. However, the present invention can be applied in the same manner even when the substrate to be processed is a matrix substrate on which a liquid crystal display device is formed. This is realized by using the same impurity introduction apparatus as that used in the first embodiment. However, in the case of a large-area substrate, the plasma excitation power is easily distributed in the vacuum chamber. ) As shown in FIG. Therefore, in this case, as shown in FIG. 14 (b) as the eighth embodiment of the present invention, the gas supply amount is increased at the end, and as a result, as shown in FIG. 14 (c), A uniform plasma density can be realized. Therefore, a large area substrate can be formed.
[0068]
The present invention is not limited to the above-described embodiments, and the embodiments can be appropriately changed within the scope of the technical idea of the present invention. For example, in the third and seventh embodiments, a case is described in which a certain amount of plasma generating substance (gas substance) is introduced into the vacuum chamber 1 from the measuring chamber 7 and plasma excitation is performed. However, even if the gas substance is introduced from the supply device 9 through the mass flow controller 10 without passing through the measuring chamber 7, the same effect can be obtained. In this case, plasma excitation may be performed while operating the vacuum pump 6 and exhausting the gas substance. The impurity doping amount in this case can be controlled by the total introduction amount of the gas substance obtained by integration from the mass flow controller 10. The feature of the impurity introduction apparatus of the present invention is that rapid processing is possible. Therefore, the plasma generator 2 may generate high-density plasma such as ICP (Inductive Coupled Plasma). However, even in this case, it is necessary to enable a high-speed response as described above.
[0069]
In the above-described embodiment, the method of introducing impurities under reduced pressure has been described. However, it is also possible to introduce impurities under normal pressure.
[0070]
【The invention's effect】
As described above, the present invention is a method for introducing impurities into a substrate by exciting a substance containing impurities into the substrate and introducing the impurities into the substrate from the excited substance, and the spatial distribution of the substance in the chamber in which the substrate is disposed. Adjust according to the plasma distribution.
Alternatively, the impurity introduction method according to the present invention includes a step of supplying the substance into the chamber after adjusting the distribution of the substance in the vicinity of the substrate surface to have a distribution according to the plasma distribution, and the substance on the substrate surface. And generating a plasma after reaching an equilibrium state.
[0071]
For this reason, the present invention makes it possible to introduce a highly uniform impurity into a very shallow region from the substrate surface even if the spatial uniformity of power for plasma excitation such as high frequency or microwave is poor. Thus, it is possible to provide an impurity introduction method having the effect of.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an impurity introduction apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a main body portion of an impurity introduction apparatus for explaining an impurity introduction method according to a first embodiment of the present invention.
FIG. 3 is a diagram showing the drive timing of the impurity introduction apparatus in the first embodiment of the present invention.
FIG. 4 is a diagram showing drive timing of an impurity introduction device in a second embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view of a main body portion of an impurity introduction device according to a third embodiment of the present invention.
FIG. 6 is a schematic cross-sectional view of another impurity introduction apparatus according to the fourth embodiment of the present invention.
FIG. 7 is a schematic cross-sectional view of a main body portion of an impurity introduction apparatus for explaining an impurity introduction method according to a fifth embodiment of the present invention.
FIG. 8A is a diagram showing the plasma intensity in the fifth embodiment of the present invention.
(B) The figure which shows the substance (dopant) distribution supplied in the 5th Embodiment of this invention.
(C) The figure which shows the plasma distribution in the 5th Embodiment of this invention.
FIG. 9 is a schematic cross-sectional view of a main body portion of an impurity introduction apparatus for explaining an impurity introduction method according to a sixth embodiment of the present invention.
FIG. 10 is a plan view of a silicon wafer substrate showing an impurity distribution in a sixth embodiment of the present invention.
FIG. 11 is a graph showing characteristics of the MOSFET formed in the sixth embodiment of the present invention.
FIG. 12 is a schematic cross-sectional view of a main body portion of an impurity introduction apparatus for explaining an impurity introduction method according to a seventh embodiment of the present invention.
FIG. 13 is a graph showing an impurity distribution in the seventh embodiment of the present invention.
FIG. 14A is a diagram showing plasma intensity in the eighth embodiment of the present invention.
(B) The figure which shows the substance (dopant) distribution supplied in the 8th Embodiment of this invention.
(C) The figure which shows the plasma distribution in the 8th Embodiment of this invention.
[Explanation of symbols]
1 Vacuum chamber
2 Plasma generator
3 Power supply
4 Holding stand
5 Substrate
6 Vacuum pump
7a, 7b Weighing chamber
8,14 nozzles
9 Supply device
10 Mass flow controller
11 Pressure regulator
12 Plasma
13 Rotary drive shaft
15 Gas flow
16 High frequency power supply
17 Counter electrode
18 Gas introduction pipe
19 Micro nozzle
20 Deflection plasma
P1, P2 pressure gauge
T1, T2 thermometer

Claims (26)

An impurity introduction method for exciting a substance containing an impurity to be introduced into plasma and introducing a plasma of the impurity into the substrate from the excited substance,
An impurity introduction method characterized in that the distribution of the substance in the vicinity of the substrate surface is adjusted so that at least a part of the plasma distribution can be offset. The impurity introduction method according to claim 1,
Adjusting the distribution of the substance in the vicinity of the substrate surface so as to cancel at least a part of the plasma distribution, and supplying the substance into the chamber in which the substrate is disposed;
And a step of generating plasma after the substance is in an equilibrium state on the substrate surface. The impurity introduction method according to claim 2,
The step of supplying the substance is an impurity introduction method in which the impurities introduced into the substrate are adjusted to be uniform. The impurity introduction method according to claim 2,
The step of supplying the substance is an impurity introduction method in which the impurities introduced into the substrate are adjusted so as to have a predetermined distribution. An impurity introduction method according to any one of claims 1 to 4,
A method for introducing an impurity, wherein plasma is generated in a state where supply of the substance is stopped. An impurity introduction method according to any one of claims 1 to 4,
A method for introducing an impurity, wherein plasma is generated in a state where supply and discharge of the substance are stopped. An impurity introduction method for exciting a substance containing impurities by plasma and introducing the impurities into the substrate from the excited substance,
An impurity introducing method, wherein plasma is generated in a state where supply of the substance into a chamber in which the substrate is disposed is stopped. An impurity introduction method for exciting a substance containing impurities by plasma and introducing the impurities into the substrate from the excited substance,
A method of introducing an impurity, characterized in that plasma is generated in a state where supply and discharge of the substance into a chamber in which the substrate is disposed are stopped. An impurity introduction method for exciting a substance containing impurities by plasma and introducing the impurities into the substrate from the excited substance,
A method for introducing an impurity, characterized in that plasma is generated after the substance supplied into a chamber in which the substrate is arranged is in an equilibrium state on the surface of the substrate. An impurity introduction method according to any one of claims 1 to 9,
An impurity introduction method characterized in that plasma is generated after the flow rate of the substance becomes 100 meV or less in terms of conversion rate. An impurity introduction method according to any one of claims 1 to 10,
A method for introducing an impurity, comprising: generating plasma after supplying a certain amount of the substance into a chamber in which the substrate is disposed. The impurity introduction method according to claim 11,
An amount of the substance to be supplied is determined according to the amount of impurities introduced into the substrate. An impurity introduction method according to any one of claims 1 to 12,
The method for introducing an impurity according to claim 1, wherein the substance is supplied into the chamber in which the substrate is arranged while adjusting the distribution of the impurities through a micro nozzle. An impurity introduction method according to any one of claims 1 to 13,
The impurity introduction method, wherein the substance is a gas. The impurity introduction method according to claim 14,
The impurity introduction method, wherein the gas includes any of B ₂ H ₆ , BF ₃ , AsH ₃ , and PH ₃ . An impurity introduction method according to any one of claims 1 to 13,
The impurity introduction method, wherein the substance is fine particles. An impurity introduction method according to any one of claims 1 to 13,
The impurity introduction method, wherein the substance is a fine droplet. The impurity introduction method according to claim 16 or 17,
The method for introducing impurities, wherein the fine particles include any one of B, As, P, Sb, In, and Al. An impurity introducing apparatus for plasma-exciting a substance containing impurities and introducing the impurities into the substrate from the excited substance,
A chamber in which the substrate is disposed;
Means for supplying the substance into the chamber;
Means for evacuating the chamber;
An impurity introducing apparatus comprising: plasma generating means for converting the substance into plasma while maintaining the equilibrium state. The impurity introduction device according to claim 19, wherein
The means for supplying a substance has a mechanism for measuring and storing the substance, and an impurity introducing device. The impurity introduction device according to claim 20, wherein
The mechanism for measuring and storing the substance controls the volume, pressure, and temperature of the storage container and holds the substance at a constant amount. The impurity introduction apparatus according to claim 20 to 21, wherein
The container for measuring and storing the substance is capable of storing an amount of the substance corresponding to the amount of the impurity introduced into the substrate. The impurity introduction device according to any one of claims 19 to 22,
The impurity introduction apparatus, wherein the substance is gas, fine particles, or fine droplets. The impurity introduction method according to any one of claims 1 to 18,
Simulating the behavior of the substance,
An impurity introduction method in which the timing for generating the plasma is adjusted based on the simulation result. A semiconductor device formed using the impurity introduction method according to any one of claims 1 to 18 and 24 or the impurity introduction device according to any one of claims 15 to 23,
A semiconductor device having an element region formed by introducing the impurity. The semiconductor device according to claim 25, wherein
The element region includes an impurity introduction region having a plurality of different impurity profiles.

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