JP4372041B2 - Semiconductor device manufacturing method and annealing apparatus - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to heat treatment necessary for impurity diffusion and activation processes.

  In recent years, the performance improvement of LSI (Large Scale Integrated Circuit) has been achieved by increasing the degree of integration, that is, by miniaturizing elements constituting the LSI. However, with the miniaturization of elements, parasitic resistance and short channel effects are likely to occur. Therefore, it is important to form a shallow pn junction with low resistance in order to prevent the occurrence of these.

Shallow pn junction, that is, shallow impurity diffusion layer (source / drain region) in the well
As a method for forming the film, a method is generally used in which ion implantation is performed at a low acceleration energy, and the subsequent annealing treatment (heat treatment) is shortened to adjust the diffusion depth shallow. For example, as a short-time annealing treatment method, a short-time heat treatment (RTA: Rapid Thermal Anneal) using a halogen lamp is used.

  However, with the demand for miniaturization, the depth of the pn junction is required to be further shallow, and the formation of an extremely shallow junction of less than 20 nm has been required. At present, boron (B) is mainly used as the p-type impurity, and phosphorus (P) or arsenic (As) is mainly used as the n-type impurity. However, impurities such as B, P, or As in the silicon (Si) substrate are used. Since the diffusion coefficient is relatively large, it is difficult to form a very shallow pn junction having a depth of less than 20 nm even when RTA is used.

  When using a halogen lamp, it is difficult to adjust the light emission time to several hundred ms or less, and there is a limit to shortening the annealing process. On the other hand, if the annealing temperature, that is, the light emission energy intensity is lowered in order to suppress impurity diffusion, the activation rate of the impurity is greatly reduced, and the resistance of the impurity diffusion layer is increased. Accordingly, it is difficult to form a shallow impurity diffusion layer having a low resistance and a depth of 20 nm or less by RTA treatment using a halogen lamp.

  Recently, the present inventors have examined the adoption of a flash lamp annealing method using a xenon (Xe) flash lamp in place of the conventional RTA processing method using a halogen lamp. The Xe flash lamp is white light having an emission wavelength in a wide range from the visible range to the near infrared range, and is a light source capable of emitting light for a very short time of several hundreds μs to 10 ms. By adopting the flash lamp annealing method using this Xe flash lamp, instantaneous annealing at a high temperature becomes possible. As a result, the impurities can be activated without diffusion of the implanted impurities, and the shallow and A low-resistance pn junction can be formed.

  In general, in the manufacturing process of a MOS transistor using a polycrystalline silicon gate (poly-Si gate) electrode, in order to reduce the resistance of the gate electrode, when the impurity is ion-implanted into the semiconductor substrate, the impurity is also ionized into the gate electrode. Impurities implanted and activated in the semiconductor substrate in the annealing process are activated, and impurities in the gate electrode layer are diffused throughout the gate electrode and activated to reduce the resistance.

  In the annealing method using the Xe flash lamp, since the lamp emission time is extremely short, an annealing process can be performed for a very short time, and activation can be performed without diffusing impurities in the semiconductor substrate. A drain region can be formed. However, on the other hand, since the annealing time is extremely short, the impurity implanted into the gate electrode cannot be diffused throughout the gate electrode, and a region where impurity diffusion is insufficient remains in the gate electrode. This impurity-deficient region is depleted, causing a reduction in capacitance, resulting in a reduction in driving power of the transistor.

  As described above, the annealing method using the Xe flash lamp can form an impurity diffusion layer (source / drain region) having a low resistance and a shallow junction. However, since the depletion layer remains in the gate electrode, Even if a transistor is formed, high-performance transistor characteristics associated with miniaturization cannot be obtained.

  In view of the above-described conventional problems, an object of the present invention is to provide a method for manufacturing a semiconductor device capable of manufacturing an impurity diffusion layer having a low resistance and a shallow junction, and a transistor having a good driving force, and annealing used in the manufacturing method. Is to provide a device.

  The semiconductor device manufacturing method of the present invention is characterized by a step of forming a gate insulating film on a single crystal semiconductor substrate, a step of forming a gate electrode made of a polycrystalline conductive film on the gate insulating film, And a step of injecting impurities into the surface layer of the semiconductor substrate adjacent to or separated from the gate electrode, and the diffusion of the impurities injected into the surface layer of the semiconductor substrate while mainly diffusing the impurities injected into the gate electrode. A first heat treatment step for performing heat treatment at a temperature to be suppressed, and a second heat treatment step for performing heat treatment at a temperature higher than that of the first heat treatment at a temperature for activating the impurities implanted into the semiconductor substrate. .

  According to the above-described feature of the present invention, the impurity in the semiconductor substrate is first subjected to the first heat treatment step by utilizing the property that the impurity easily diffuses at a lower temperature in the polycrystalline gate electrode than in the single crystal semiconductor substrate. Since the diffusion is suppressed, the impurities in the gate electrode are selectively diffused, the impurities are diffused throughout the gate electrode, and depletion of the bottom of the gate electrode due to insufficient diffusion is prevented. Next, the impurities in the semiconductor substrate and the gate electrode are activated by the high-temperature short-time heat treatment in the second heat treatment step. Since the second heat treatment is performed in a short time at a high temperature, the second heat treatment can be activated with almost no impurities diffused. Therefore, the impurity diffusion layer formed in the semiconductor substrate can maintain a shallow junction depth even by this two-step heat treatment. A semiconductor device such as a transistor having a finer and shallower junction can be manufactured without the problem of depletion of the gate electrode.

  In the method of manufacturing a semiconductor device, the step of implanting impurities includes a first ion implantation step of forming a first impurity ion implantation region by performing ion implantation on the surface layer of the semiconductor substrate in a region adjacent to the gate electrode, There may be provided a second ion implantation step in which ion implantation is performed on the surface layer of the semiconductor substrate in a region separated from the electrode to form a second impurity ion implantation region deeper than the first impurity ion implantation region.

  In this case, a shallower impurity diffusion region, that is, an extension region can be formed in the surface layer of the semiconductor substrate adjacent to the gate electrode. Therefore, the short channel effect that occurs when a finer transistor is manufactured can be suppressed.

  Moreover, you may have a 3rd heat treatment process on the same conditions as the said 2nd heat treatment process after a 1st ion implantation process and before a 2nd ion implantation process.

  In this case, in the third heat treatment step performed after the first ion implantation step, as in the second heat treatment step, a high temperature short time heat treatment is performed, so that an extension region having a shallow junction can be obtained.

  An example of the polycrystalline conductive film is a polycrystalline Si film.

  The first heat treatment step is preferably performed under conditions where the annealing temperature is 600 ° C. or more and 950 ° C. or less and the annealing time is 1 hour to 5 seconds depending on the temperature condition.

  The first heat treatment step can be performed using an infrared lamp or a hot plate. Here, examples of the infrared lamp include a halogen lamp.

  In the second heat treatment step, the heat treatment time is desirably 100 ms or less.

The second heat treatment step can be performed using a light source that can be adjusted to an irradiation time of 100 ms or less. Moreover, as this light source, it is desirable to use a light source having an irradiation energy density of 10 to 60 J / cm ² . For example, the light source may be a Xe flash lamp. Further, the irradiation time of the Xe flash lamp is more desirably 10 ms or less. In addition to the Xe flash lamp, an excimer laser, a YAG laser, or the like can be used.

  The second heat treatment step is desirably performed in advance in a state where the semiconductor substrate is preheated at a temperature lower than the heat treatment temperature in the first heat treatment step.

  By performing the preheating, it is possible to prevent the substrate from being damaged due to a rapid substrate temperature rise due to the short time high temperature heat treatment.

  The preheating temperature is preferably 200 to 600 ° C. The preheating can be performed using an infrared lamp or a hot plate.

  The first heat treatment step and the second heat treatment step may be performed continuously in the same chamber using a single annealing apparatus.

  In this case, it is possible to save the time and labor of the substrate between the first heat treatment step and the second heat treatment step and the pretreatment, and the throughput is not sacrificed by the two-step heat treatment.

The annealing apparatus includes a chamber for hermetically storing the substrate, a first heating source provided in the chamber and having a light source with an irradiation time of 100 ms or less and an irradiation energy density of 10 to 60 J / cm ² , halogen A lamp having a second heating source composed of a lamp or a hot plate can be used. Note that the first heating source is desirably a Xe flash lamp.

The annealing apparatus according to the present invention is characterized by a chamber for hermetically storing a substrate, and a first heating source provided in the chamber having a light source with an irradiation time of 100 ms or less and an irradiation energy density of 10 to 60 J / cm ^2. And a second heating source comprising a halogen lamp or a hot plate. The first heating source is more preferably an Xe flash lamp.

  According to the annealing apparatus of the present invention, the two-stage heat treatment consisting of the first heat treatment step and the second heat treatment step in the semiconductor device manufacturing method of the present invention can be continuously performed in the same chamber. The method for manufacturing a semiconductor device of the present invention can be implemented without sacrificing.

  According to the characteristics of the method for manufacturing a semiconductor device of the present invention, a low-resistance and shallow impurity diffusion layer can be formed, the impurity region of the gate electrode can be sufficiently activated, and depletion of the gate electrode is suppressed. The impurity profile can be controlled with high accuracy. Therefore, a high performance MOS transistor having a shallow junction corresponding to miniaturization can be manufactured.

  Further, according to the feature of the annealing apparatus of the present invention, the two-step annealing process in the semiconductor device manufacturing method of the present invention can be continuously performed in the same chamber, so that the cost can be reduced easily without reducing the throughput. In addition, a high-performance MOS transistor corresponding to miniaturization can be manufactured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment)
FIG. 1A to FIG. 1F are process diagrams showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. Here, a manufacturing process of a fine p-type MOS transistor formed in a LOGIC circuit or a memory region will be described as an example.

  The main feature of the manufacturing method in the present embodiment is that the annealing after the ion implantation process, which has been performed for forming the source / drain regions, is performed by a pre-annealing process (first heat treatment process) and a flash lamp annealing process (second process). The heat treatment step) is performed in two stages. Hereinafter, this manufacturing method will be specifically described with reference to the drawings.

First, as shown in FIG. 1 (a), an n-type single crystal or a surface region of a p-type single crystal is doped with an n-type impurity in order to define an activation region in accordance with a normal method for manufacturing a p-type MOS transistor. An element isolation region 2 is formed on a silicon (Si) substrate 1. The element isolation region 2 is preferably STI (Shallow Trench Isolation) as shown in the figure. The STI structure is obtained by forming a groove in the silicon substrate 1, filling the groove with an insulating film such as a SiO ₂ film, and flattening the surface. Thereafter, a thin insulating film having a thickness of less than about 3 nm, for example, a SiO ₂ film is formed as the gate insulating film 3, and a polycrystalline Si film having a thickness of about 175 nm is further formed on the gate insulating film 3, and selective etching is performed. Thus, the gate electrode 4 made of a polycrystalline Si film is formed.

Next, as shown in FIG. 1B, boron (B +) is ion-implanted into the surface layer of the Si substrate 1 using the gate electrode 4 as an ion implantation mask in order to form source / drain extension regions. . The ion implantation conditions are, for example, an acceleration energy of 0.2 keV and a dose of 1 × 10 ¹⁵ cm ⁻² . By this ion implantation, a shallow impurity ion implantation region 5 is formed in the surface layer of the Si substrate 1 adjacent to the gate electrode 4.

  Next, annealing is performed to activate the impurity ions in the impurity ion implantation region 5. This annealing process may be an RTA process using a conventional halogen lamp, but a high-temperature flash lamp annealing process using a xenon (Xe) flash lamp is preferably performed. The flash lamp annealing process is performed under the same conditions as the second heat treatment process conditions for forming the source / drain regions described later.

FIG. 2 is a graph showing the flash lamp annealing conditions. As shown in the figure, in the flash lamp annealing process, the Si substrate 1 is heated in advance to a temperature of about 400 ° C. using a hot plate or other heater, and then the Xe flash lamp is irradiated for a very short time, for example, The entire surface of the Si substrate 1 is irradiated for about 1 ms. At this time, the irradiation energy density of the Xe flash lamp is, for example, about 35 J / cm ² . The surface of the Si substrate 1 reaches a temperature at which the ion-implanted impurity element is sufficiently activated, for example, 1100 ° C. or more, by this short-time Xe flash lamp irradiation.

  In the flash lamp annealing process using the Xe flash lamp, the annealing process is performed in an extremely short time even shorter than the RTA using the conventional halogen lamp, so that the crystal defects in the impurity ion implantation region can be recovered and activated, and the implantation is performed. The impurity ions thus diffuse hardly diffuse in the depth direction. As a result, as shown in FIG. 1C, an extremely shallow and low-resistance extension region 6 having a depth of about 10 nm is formed.

  Note that when RTA using a halogen lamp is performed instead of the flash lamp annealing treatment, the substrate temperature is desirably 800 ° C. or lower and the heating time is approximately 10 seconds. Also by this RTA, the impurity element is activated without diffusing deeply into the substrate, crystal defects in the impurity ion implantation region 5 can be recovered, and the source / drain extension regions 6 can be formed. .

Next, as shown in FIG. 1D, a sidewall spacer having a multilayer structure is formed on the sidewall of the gate electrode 4. By sequentially depositing a silicon nitride film (SiN film) 7 and a silicon oxide film (SiO ₂ film) 8 using a CVD method, and subsequently performing anisotropic etching by a RIE (Reactive Ion Etching) method, The SiN film 7 and the SiO ₂ film 8 are selectively left only on the side wall of the gate electrode 4 to obtain a multi-layer side wall spacer as shown in FIG.

As shown in FIG. 1E, B ⁺ that is a p-type impurity is ion-implanted again using a sidewall spacer including the gate electrode 4, the SiN film 7, and the SiO ₂ film 8 as an ion implantation mask. The ion implantation conditions are, for example, an acceleration energy of 5 keV and a dose amount of 3 × 10 ¹⁵ cm ⁻² . By this ion implantation, a deep impurity ion implantation region 9 is formed in the surface layer of the Si substrate 1 separated from the end of the gate electrode 4. At this time, a considerable amount of impurity ions B ⁺ is also implanted into the gate electrode 4 made of polycrystalline Si.

  Next, an annealing process is performed to activate the impurity ion implantation region 9 and to diffuse ions implanted into the gate electrode. Here, in the present embodiment, the annealing process is performed in two stages, a first heat treatment process and a second heat treatment process, unlike the conventional case.

  First, a first heat treatment (pre-annealing) is performed by RTA using a halogen lamp. FIG. 3 shows pre-annealing conditions. As shown in the figure, as pre-annealing conditions, for example, the substrate temperature is 900 ° C. and the annealing time is 20 seconds.

  In general, when impurities implanted into a polycrystalline material are compared with impurities implanted into a single crystal material, the impurities implanted into the polycrystalline material are more likely to diffuse at a lower temperature. This is because the polycrystalline material has crystal grain boundaries where impurities are likely to diffuse. Based on the characteristics of this impurity diffusion, a temperature condition is set such that the impurity in the polycrystalline gate electrode diffuses but the impurity diffusion in the single crystal semiconductor substrate is suppressed as in the pre-anneal temperature condition. B implanted into the gate electrode 4 made of polycrystalline Si diffuses in the depth direction according to the concentration gradient and spreads over the entire layer of the gate electrode 4 having a thickness of about 175 nm, but is implanted into the Si substrate 1 which is a single crystal. B remains in the ion implantation region 9 with little diffusion. In this way, only the diffusion of B in the gate electrode 4 is promoted, and the shallow junction depth can be maintained without diffusion for the impurity B in the extension region 6 already formed.

Subsequently, a second heat treatment is performed using a Xe flash lamp. The second heat treatment, that is, the flash lamp annealing condition for activating the impurity diffusion region can be substantially the same as the flash lamp annealing condition previously performed for forming the extension region 6. As shown in FIG. 2, the entire surface of the substrate is irradiated with light from a Xe flash lamp while the substrate is heated to a temperature of about 400 ° C. in advance. The irradiation time and irradiation energy density are, for example, about 1 ms and 35 J / cm ^2, and the temperature of the substrate surface layer is instantaneously raised to recover crystal defects in the region where the impurity ions are implanted, and the implanted ions are activated. To do. The substrate arrival temperature at this time is 1100 ° C. or higher.

  As shown in FIG. 1F, the flash lamp annealing activates the ion-implanted impurities, recovers the crystal defects in the impurity ion-implanted region 9, and deepens them away from the end of the gate electrode 4. A source / drain region 10 is obtained. Further, since the annealing process is extremely short, diffusion of impurities in the extension region 6 is suppressed, and the junction depth can be kept shallow.

Although the subsequent steps are not shown, an SiO ₂ film is formed as an interlayer insulating film on the entire surface at a film forming temperature of 400 ° C., for example, by an atmospheric pressure CVD method according to a general MOS transistor manufacturing method. Thereafter, contact holes are opened in the interlayer insulating film, and necessary lead wirings are formed in the source / drain regions 10 and the gate electrode 4 respectively.

  As described above, in the method of manufacturing a semiconductor device according to the present embodiment, the annealing process used for forming the source / drain regions suppresses the diffusion of the impurity implanted into the single crystal Si substrate 1 and A pre-annealing step (first heat treatment step) under a temperature condition that can promote diffusion of impurities implanted into the gate electrode 4 made of crystalline Si, and a condition under which the impurities implanted into the single-crystal Si substrate 1 can be activated. In addition, since it has a process of performing a flash lamp annealing for a very short time (second heat treatment process), it is possible to achieve both improvement of transistor characteristics and formation of an extremely shallow junction of 20 nm or less.

(Examination 1)
In order to investigate the characteristics of the gate electrode obtained using the manufacturing method of the present embodiment, a MOS capacitor having the structure shown in FIG. Hereinafter, it was referred to as a capacitor of the example), and the CV characteristics were measured. As a first comparative example, pre-annealing (first heat treatment step) is not performed, only flash lamp annealing (second heat treatment step) is performed, and other conditions are the same as those in the manufacturing method according to the embodiment. A similar MOS capacitor (hereinafter referred to as the capacitor of Comparative Example 1) was produced. As a second comparative example, only RTA is performed under the conditions of 1015 ° C. and 10 seconds, which is the conventional method, and the other conditions are MOS capacitors (hereinafter referred to as the capacitor of Comparative Example 2) under the same conditions as in the example. Produced. The CV characteristic of each MOS capacitor was measured, and the result is shown in FIG.

In the MOS capacitor of the example, a gate capacitance of about 6 × 10 ⁻⁷ F / cm ² was obtained at a gate voltage of 2.5 V and a frequency of 100 kHz. This value is equal to the gate capacitance value of the MOS capacitor obtained by the comparative example 2 (conventional example) in which only the RTA process using the halogen lamp is performed, and the CV characteristics are almost the same. On the other hand, in the case of Comparative Example 1 where only flash lamp annealing was performed, the gate capacitance of the MOS capacitor was about 2.6 × 10 ⁻⁷ F / cm ² under the same gate voltage and the same frequency conditions.

  In the MOS capacitor of Comparative Example 1 in which only the flash lamp annealing was performed, the gate capacitance was reduced, and the result was the same as when the insulating film under the gate electrode was apparently formed thick. That is, with only Xe flash lamp annealing, the annealing process time is extremely short, so that B, which is an impurity in the gate electrode, does not diffuse deeply into the gate electrode, leaving a region with an insufficient impurity concentration at the bottom of the gate electrode. This is thought to be due to the formation of The thickness of the depletion layer calculated from the gate capacitance value reached about 23 nm when the total thickness of the gate electrode was 175 nm.

  From this result, it is confirmed that the diffusion of impurities in the gate electrode proceeds and the generation of the depletion layer can be prevented by the pre-annealing process (first heat treatment process) performed for forming the source / drain regions according to this embodiment. did it.

  If the depletion layer remains at the bottom of the gate electrode, not only does the driving force of the transistor decrease, but the function as a transistor may not be exhibited in the first place. As a method for preventing depletion of the gate electrode, there is a method of increasing acceleration energy in order to implant impurity ions deeper in an ion implantation step performed before annealing. In this case, the surface layer of the Si substrate 1 is simultaneously used. Since the diffusion of impurities implanted in the depth direction and the lateral direction proceeds, there is a high possibility of inducing a short channel effect. Further, when the impurity enters the gate insulating film, the threshold voltage of the transistor is changed. In that respect, if the two-step annealing method consisting of pre-annealing (first heat treatment) and Xe flash lamp annealing (second heat treatment) described in the present embodiment is adopted, the first heat treatment mainly uses the polycrystalline gate electrode. Only the impurity diffusion is promoted, and in the second heat treatment, each impurity can be activated with little influence on the depth of the source / drain region and the extension region, so that the occurrence of the short channel effect can be suppressed.

(Examination 2)
Next, in order to investigate the relationship between the annealing conditions and the diffusion state of the impurity B in the gate electrode, the MOS transistor of the example manufactured under the manufacturing conditions of the above-described embodiment and the manufacturing conditions changed only in the annealing conditions The concentration distribution in the depth direction of the impurity (B) in the gate electrode in each of the MOS transistors of the comparative example was measured. The manufacturing method of the MOS transistor of this comparative example was performed by performing only the flash lamp annealing (second heat treatment step) without performing pre-annealing (first heat treatment step), and the other conditions were manufactured by the manufacturing method according to the embodiment. The same conditions as in the MOS transistor of the example are used.

FIG. 5 is a graph showing the results of measuring the concentration distribution in the depth direction of the impurity (B) in the gate electrode in each transistor of the example and the comparative example. As shown in the graph, in the gate electrode of the transistor of the example, B is distributed almost uniformly in the depth direction over the entire gate electrode, and a high impurity concentration of about 1020 cm ⁻³ is obtained. It could be confirmed. On the other hand, the gate electrode of the transistor of the comparative example shows a high impurity concentration in the shallow region, but the B concentration decreases as the depth increases, and the diffusion of B into the deep region becomes insufficient. Depletion is expected to occur in the region below ¹⁹ cm ⁻³ .

(Examination 3)
FIG. 6 shows a concentration distribution of B which is an impurity in the source / drain extension region 6 obtained by the manufacturing method according to the embodiment. The depth at which the concentration was 10 ¹⁸ cm ⁻³ , that is, the substantial junction depth was about 14 nm, and the diffusion layer resistance was 770Ω / □. It was confirmed that a shallow and low resistance impurity diffusion layer was formed. From this result, it was confirmed that the junction depth of the extension region 6 can be maintained at 20 nm or less by the two-step annealing method according to the present embodiment.

  In order to suppress the depletion of the gate electrode only by RTA using a halogen lamp without using flash lamp annealing and to make the impurity diffusion layer have a desired resistance value, an annealing temperature of 1000 ° C. or more is used for 10 seconds. The above heating temperature is required. Under this annealing condition, the impurity in the extension region and the source / drain region diffuses to the periphery and cannot maintain a shallow junction, thereby causing a short channel effect and losing the function as a transistor.

(Other embodiments)
In the embodiment described above, an example in which a polycrystalline Si electrode is used as the gate electrode has been described. However, in order to reduce the contact resistance between the gate electrode and the wiring, a structure in which the surface layer portion of the gate electrode is silicided is employed. In addition, the above-described two-step annealing method can be employed for forming the source / drain regions.

Usually, such a silicide layer is formed by sputtering the surface layer of the gate electrode and the surface layer of the source / drain region with cobalt (Co), titanium (Ti), nickel (Ni), etc. Co silicide, Ti salicide, Ni salicide structure and the like are formed by silicidation in a consistent manner. The thickness of the silicide layer is desirably about 30 nm. When the silicide layer is thickened or the thickness of the substantially polycrystalline Si gate electrode is thinned, the 3d transition metal atoms such as cobalt that could not be silicided have a large diffusion coefficient in Si or SiO _2. In addition, the diffusion from the gate electrode to the gate insulating film increases the leakage current from the gate electrode to the Si substrate. However, if the thickness of the silicide layer is set to be smaller than 30 nm in order to suppress the above phenomenon, the contact resistance is increased and the driving force of the transistor is decreased. Therefore, the gate electrode needs to be at least 100 nm thick. A thickness of 150 nm or more is desirable.

  Further, in the present embodiment, the case where the polycrystalline Si gate electrode is manufactured has been described. However, the two-step annealing is not limited to the polycrystalline Si, but the semiconductor substrate is made of a single crystal and the gate electrode is made of polycrystalline. The law can be applied effectively.

In the above embodiment, the pre-annealing (first heat treatment) condition in the two-stage annealing process is set to 900 ° C. and 20 seconds, but the pre-annealing condition is not limited to this. FIG. 7 shows an example of pre-annealing conditions. In the case where the thickness of the polycrystalline Si gate electrode is about 175 nm and the conditions of the ion implantation process before pre-annealing are ion implantation of B as an impurity with an acceleration energy of 0.2 keV and a dose of 1 × 10 ¹⁵ cm ^−2. As shown in the figure, the condition indicated by the shaded area can suppress depletion in the polycrystalline Si gate electrode and can maintain the junction depth of the extension region of the source / drain already formed at 20 nm or less. That's fine.

  In order to suppress the junction depth of the impurity (B) in the extension region in the Si substrate to be less than 20 nm, the temperature is preferably 950 ° C. or less. The required pre-annealing time depends on the annealing temperature condition. For example, 12 minutes when the annealing temperature is 800 ° C., 3 minutes when the annealing temperature is 850 ° C., and if the annealing temperature is 900 ° C., 40 seconds or less, even if heating is continued, the impurity (B) in the extension region in the Si substrate is bonded The depth can be suppressed to 20 nm or less, and the impurity implanted into the polycrystalline Si gate electrode diffuses to the bottom of the gate electrode and can suppress depletion.

  Although the thickness of the polycrystalline Si gate electrode is 175 nm, it may be about 100 nm to 200 nm, and the pre-annealing time is preferably variable according to the film thickness. When the gate electrode layer is thinner, the pre-annealing time is It is desirable to shorten the length.

In this embodiment, flash lamp annealing (second heat treatment) is performed by preheating the substrate to 400 ° C. in advance, and the irradiation energy density of the Xe flash lamp is set to 35 J / cm ² and the irradiation time is 1 ms. However, it is not limited to this condition. The irradiation time is practical if it is 100 ms or less, but is preferably as short as possible in order to suppress the diffusion of impurities, and is preferably 10 ms or less. When the irradiation time is 1 ms, the preheating temperature can be changed in the range of 200 to 600 ° C. and the irradiation energy density in the range of 10 to 60 J / cm ² .

When the irradiation energy density exceeds 60 J / cm ² , damage such as slips and cracks occurs in the Si substrate due to an increase in thermal stress accompanying excessive and rapid irradiation energy. The preheating has an effect of suppressing the necessary irradiation energy density of the flash lamp and suppressing the generation of thermal stress on the substrate accompanying a rapid temperature rise. Further, if the surface of the Si substrate is heated only by the flash lamp, the energy input to the lamp is increased, and the life of the lamp is shortened. Therefore, preheating has the effect of suppressing the necessary irradiation energy density of the lamp and extending the lamp life.

In order to reduce the irradiation energy of the lamp to 60 J / cm ² or less in order to activate the impurities at a high concentration, it is desirable to set the preheating temperature to 200 ° C. or more.

  On the other hand, if the preheating temperature is higher than 600 ° C., the total energy amount becomes excessive due to the flash lamp being turned on, and the Si substrate temperature is maintained at a high temperature due to the residual heat even after the flash lamp is turned off, and the diffusion of impurities continues. As a result, it becomes difficult to obtain a shallow junction state. Further, if the preheating temperature is too high, the substrate becomes brittle and susceptible to damage. Therefore, an appropriate temperature range is desirable for preventing damage to the substrate. Therefore, the preheating temperature is desirably 200 to 600 ° C.

  The preheating means may be any means that can heat the substrate to 200 to 600 ° C. In addition to lamp heating with a halogen lamp, heater heating with a hot plate or the like may be used.

  Further, although the Xe flash lamp is used as the light source for the flash lamp annealing according to the embodiment, the type of the lamp to be used is not limited to this. Any light source that can supply the necessary irradiation energy and can adjust the light emission time to an extremely short time may be used. It is desirable that the light emission time, that is, the irradiation time can be adjusted to 100 ms or less, more desirably 10 ms or less, and even more preferably several ms or less. For example, a laser such as an excimer laser or a YAG laser capable of pulse oscillation can be used. Since the Xe flash lamp has a light emission wavelength in the visible region to the near infrared region where the Si single crystal substrate has a high absorption rate, the substrate can be efficiently heated, but other light sources may be used. If a light source having a wavelength of less than 1100 nm at which the Si single crystal substrate exhibits a high absorptance is used, the utilization efficiency of irradiation energy can be increased.

  The above-described two-stage annealing method of the present embodiment uses a first annealing apparatus equipped with a halogen lamp and a second annealing apparatus equipped with a Xe flash lamp to perform pre-annealing (first heat treatment) and a flash lamp. Annealing (second heat treatment) can be performed independently, but if an annealing apparatus having both a pre-annealing heating source and a flash lamp annealing heating source in the same chamber is used, a single annealing apparatus can be used. Can be used to perform two-step annealing continuously.

  FIG. 8 is a graph showing an example of a temperature profile when pre-annealing and flash lamp annealing are continuously performed. As shown in the figure, for example, after pre-annealing (first heat treatment) is performed at a heating temperature of 900 ° C. and a heating time of 20 seconds, flash lamp annealing (second heat treatment) is continuously performed. That is, the substrate temperature is lowered to a preheating temperature, for example, 400 ° C., and when the temperature becomes constant, the Xe flash lamp is turned on for 1 ms.

  When performing two-step annealing continuously using a single annealing device, there is no need to lower the substrate temperature to room temperature in the middle of the process, and it is possible to increase the throughput because it eliminates the trouble of taking the substrate in and out of the chamber. , Equipment space and production facilities can be saved.

  FIG. 9 is a diagram illustrating a schematic configuration of an annealing apparatus including a pre-annealing heat source and a flash lamp annealing heat source. A Xe flash lamp 13 is provided above, a halogen lamp 14 is provided below, and a substrate table 11 on which the substrate 12 is placed is provided therebetween. Only the lower halogen lamp 14 is used for the pre-annealing (first heat treatment), and the halogen lamp 14 and the Xe flash lamp 13 are used for the flash lamp annealing (second heat treatment). Preheating is performed and flash lamp annealing is performed with a Xe flash lamp. When the halogen lamp 14 and the Xe flash lamp 13 are each composed of a plurality of rod-shaped lamp groups, the lamp arrangement direction of the halogen lamp 14 and the Xe flash lamp 13 may be arranged so as to intersect each other. preferable.

  Instead of the halogen lamp 14, a hot plate integrated with the substrate table may be used. In place of the Xe flash lamp, an excimer laser or a YAG laser capable of emitting pulses for a very short time may be used.

  As described above, according to the method of manufacturing a semiconductor device according to the present embodiment, a low-resistance and shallow impurity diffusion layer can be formed, and depletion of the gate electrode can be suppressed, and the impurity profile can be suppressed. Can be accurately controlled. Further, if the annealing apparatus shown in FIG. 8 is used, an increase in the number of steps does not occur, so that a high-performance MOS transistor that can easily be miniaturized can be manufactured at low cost without reducing the throughput.

  As described above, the present invention has been described along the present embodiment, but it is obvious to those skilled in the art that various modifications and alterations are possible. For example, although B is used as the p-type impurity in the present embodiment, other group III elements that can serve as acceptors can be used instead. In the above example, the p-type MOS transistor has been described. However, the above-described semiconductor manufacturing method can be similarly applied to an n-type MOS transistor whose conductivity type is reversed. In this case, phosphorus (P), arsenic (As), or the like that can be a donor may be ion-implanted as an impurity in order to form a source / drain region.

It is sectional drawing of the semiconductor device of each process which shows the semiconductor manufacturing method in embodiment of this invention. It is a figure which shows the temperature profile in the flash lamp annealing process in embodiment of this invention. It is a figure which shows the temperature profile in the pre-annealing process in embodiment of this invention. The MOS gate of the example produced using the two-step annealing method according to the embodiment of the present invention, the comparative example 1 using only the flash lamp annealing instead of the two-step annealing, and the comparative example 2 using the conventional annealing method It is a figure which shows the relationship between the gate capacitance of each MOS gate, and gate voltage. The gate electrode of the example manufactured using the two-step annealing method according to the embodiment of the present invention and the boron (B) of the gate electrode of the comparative example manufactured using only the flash lamp annealing method instead of the two-step annealing method It is the figure which showed density distribution. It is the figure which showed the density | concentration distribution of the boron (B) in the extension area | region of the source / drain obtained with the manufacturing method which concerns on embodiment of this invention. It is a figure which shows the pre-annealing conditions which concern on embodiment of this invention. It is a figure which shows the temperature profile in the case of performing pre-annealing (1st heat processing) and flash lamp annealing (2nd heat processing) continuously concerning other embodiment of this invention. It is a figure which shows schematic structure of the annealing apparatus provided with the Xe flash lamp and the halogen lamp in the same chamber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Element isolation region 3 Gate insulating film 4 Gate electrode 5, 9 Impurity ion implantation region 6 Extension region 7 Silicon nitride film 8 Silicon oxide film 10 Source / drain region

Claims (4)

Forming a gate insulating film on the surface of the single crystal semiconductor substrate;
Forming a gate electrode made of a polycrystalline conductive film on the gate insulating film;
Implanting impurities into the gate electrode and the surface layer of the semiconductor substrate using the gate electrode as a mask;
A first heat treatment is performed at a temperature that diffuses impurities implanted into the gate electrode and suppresses diffusion of impurities implanted into the surface layer of the semiconductor substrate by a plurality of rod-shaped halogen lamps from the back surface of the semiconductor substrate. A process of performing;
From the first heat treatment at a temperature for activating impurities implanted into the semiconductor substrate by a plurality of rod-shaped flash lamps arranged to intersect the arrangement direction of the plurality of rod-shaped halogen lamps from the surface of the semiconductor substrate. And a step of performing the second heat treatment at a high temperature for 100 ms or less. The step of implanting the impurities includes
Injecting a first impurity into a surface layer of a semiconductor substrate in a region adjacent to the gate electrode to form a first impurity ion implantation region;
And a step of implanting a second impurity into a surface layer of a semiconductor substrate in a region separated from the gate electrode to form a second impurity ion implantation region deeper than the first impurity ion implantation region. Item 14. A method for manufacturing a semiconductor device according to Item 1. Before the step of forming the second impurity ion implantation region,
3. The method of manufacturing a semiconductor device according to claim 2, wherein the first impurity is activated under the same conditions as the second heat treatment.   The method for manufacturing a semiconductor device according to claim 1, wherein the polycrystalline conductive film is a polycrystalline Si film.

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