Method for monitoring stability of rapid thermal annealing equipment

Abstract

The invention relates to a method for monitoring the stability of rapid thermal annealing equipment, and belongs to the technical field of rapid thermal annealing equipment monitoring. The method for monitoring the stability of the rapid thermal annealing equipment comprises the following steps: S1, obtaining a temperature rule through analog calculation under different parameter conditions; s2, actual production experiments are carried out according to the parameters obtained through simulation calculation; s3, comparing a production result with a fitting result, and judging the temperature state of the machine according to the temperature inflection point and the reaction rate slope; and S4, predicting diffusion results of different parameters in actual production according to a fitting result to determine the stability of the machine. According to the method, the stability of the RTP machine table can be monitored, the thickness of TiSix in the Schottky diode production process can be predicted, the situation that the production is affected due to the fact that the machine table is contaminated in the actual production process is avoided, and meanwhile it is guaranteed that the purposes of reducing cost and improving efficiency in the machine table are achieved as much as possible.

Description

Technical Field

[0001] The invention relates to the technical field of rapid thermal annealing equipment monitoring, and in particular to a method for monitoring the stability of rapid thermal annealing equipment. Background Art

[0002] RTP (Rapid Thermal Processing) is widely used in the fields of ImplantAnneal and Titanium Salicide. Its purpose is to obtain the minimum process thermal budget by shortening the heat treatment time and temperature or only shortening the heat treatment time. Therefore, the control requirements for the cavity temperature of the rapid thermal annealing equipment are extremely strict. In Schottky diodes, TiSix generated by RTP reaction plays a more important role.

[0003] Currently, Fabrication verifies the temperature of RTP machines or monitors the temperature of RTP machines in two ways:

[0004] 1. Use Test Control wafer (TC wafer), see Figure 1 The temperature calibration principle is to place the TC wafer in the process chamber, close the chamber door, run the temperature curve of the entire process window, and the final temperature will be displayed on the temperature detection table. However, the TC wafer utilization rate of this method is high, the contact point failure rate is high, and frequent replacement of TC wafers will also lead to increased costs. The heat loss through the lead wire will cause the silicon wafer to be partially cooled and cause uneven process. It is difficult to ensure the consistency of multiple measurements. When the TC is damaged, there may be no spare, which will lead to the problem of being unable to calibrate and add TC offset.

[0005] 2. Use the pyrometer in the machine to monitor the temperature. The problem is the temperature difference caused by contamination and contact thermal resistance. Summary of the invention

[0006] The technical problem to be solved by the present invention is to better monitor the reliability of the machine, avoid failures caused by high-frequency use of TC wafers as much as possible, reduce costs, avoid contamination of the machine during each PM, and improve time efficiency, thereby providing a method for monitoring the stability of rapid thermal annealing equipment.

[0007] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0008] A method for monitoring the stability of a rapid thermal annealing device comprises the following steps:

[0009] S1. Through simulation calculation under different parameter conditions, the temperature law is obtained;

[0010] S2. Conduct actual production experiments according to the parameters of the simulation calculation;

[0011] S3. Compare the production result of step S2 with the fitting result of step S1, and determine the temperature state of the machine according to the temperature inflection point and the slope of the reaction rate;

[0012] S4. Determine the machine stability by predicting the diffusion results of different parameters during actual production based on the fitting results.

[0013] In the above technical solution, in step S1, the reaction rate and temperature are used as variables and the simulation calculation is performed based on the Arrhenius equation.

[0014] In the above technical solution, in step S1, the growth mode of the simulated wafer is to grow a layer of 950 Å metal Ti on a silicon substrate, and then extract the barrier thickness at 500-950°C with an interval of 10°C.

[0015] In the above technical solution, further, the simulation process is as follows:

[0016] Step 1, sputtering 950A metal Ti on a silicon substrate;

[0017] Step 2: Generate TiSi at different temperatures through RTP annealing x potential barrier;

[0018] Step 3: Record the TiSi generated at the corresponding temperature x thickness and remaining Ti thickness.

[0019] In the above technical solution, further, the temperature law obtained by simulation calculation is as follows:

[0020] y=32071.111e -7847.90x Within 600℃, growth thermodynamic factors play a major role (excluding 600℃);

[0021] y=-31.2832197791982+0.09097184728037*x Above 600℃, growth kinetics factors play a major role (including 600℃).

[0022] In the above technical solution, in the method:

[0023] When the reaction thermodynamics dominates, the transition state Ti 5 Si 4 The formation temperature determines whether the reaction temperature of the machine is accurate;

[0024] When the reaction kinetics dominates, the stable TiSi 2The stability of the machine can be judged by the generation rate.

[0025] The beneficial effects of the present invention are:

[0026] The method for monitoring the stability of rapid thermal annealing equipment of the present invention has the following advantages:

[0027] ① The present invention can monitor the stability of the RTP machine.

[0028] ② The present invention can roughly predict the production of TiSi in Schottky diodes x Thickness.

[0029] ③ The present invention can prevent the machine from being contaminated in the actual production process, thereby affecting the WPH of production, and at the same time ensure that the purpose of reducing costs and increasing efficiency is achieved as much as possible in the machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the existing TC wafer temperature calibration principle.

[0031] Figure 2 TiSi at different temperatures x Phase change diagram.

[0032] Figure 3 Generate phase and temperature change diagrams for the Ti-Si reaction.

[0033] Figure 4 Schematic diagram of the Ti-Si simulation reaction process.

[0034] Figure 5 Schematic diagram of Ti-Si simulation reaction results.

[0035] Figure 6 Schematic diagram of the x content and fitting curve.

[0036] Figure 7 This is the overall reaction rate curve of TiSi+Ti.

[0037] Figure 8 This is a diagram showing the result of simulating the actual process under the same conditions when the transition phase is generated.

[0038] Fig. 9 This is a diagram showing the results of simulating the actual process under the same conditions when the stable phase is generated.

[0039] Fig.10 The figure is a flow chart of the method of the present invention.

[0040] Fig.11 This is a curve diagram of the relationship between Si / Ti and temperature.

[0041] Fig.12This is a graph showing the relationship between reaction rate and temperature.

[0042] Fig.13 Schematic diagram of simulation results at different temperatures. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0044] Combination Fig.10 A method for monitoring the stability of a rapid thermal annealing device according to the present invention is described, comprising the following steps:

[0045] S1. Through simulation calculation under different parameter conditions, the temperature law is obtained;

[0046] The reaction rate and temperature were used as variables, and the simulation calculation was based on the Arrhenius formula. The growth mode of the simulated wafer was to grow a layer of 950 A metal Ti on a silicon substrate, and then the barrier thickness was extracted at 500-930℃ with an interval of 10℃;

[0047] Ti-Si reaction mechanism:

[0048] 1. When annealing below 600℃, other stable phases such as TiSi, Ti 3 At this temperature, silicon atoms can be separated from the substrate. At this time, silicon atoms quickly diffuse through the titanium / silicon interface into the titanium and the titanium grain boundaries to interact with each other, forming a layer of silicide at the titanium / silicon interface and on the surface of titanium grains. However, there are fewer free silicon atoms, which indirectly indicates that the supply of silicon atoms is relatively slow. At this time, the energy provided by the temperature rise promotes the Ti-Si reaction.

[0049] 2. Annealing at 600℃, crossing the transition energy barrier and starting to form the steady-state phase TiSi 2 , in Ti / TiSi 2 In the / Si interface region, Ti seems to diffuse into Si.

[0050] 3. When annealing at a higher temperature, the film structure is TiSi 2 / Si Considering the presence of titanium nitride on the surface. When the energy is sufficient, the kinetic process dominates and the final energy change will be TiSi 2 The formation of TiSi x See the phase change diagram for Figure 2 . See the diagram of Ti-Si reaction phase formation and temperature change for details. Figure 3 As can be seen from the figure: Ti-Si reaction generates phase TiSi 2 ,TiSi,Ti 5 Si 4 , Ti 5 Si 3 , Ti3 Si (when doping amount and temperature change):

[0051] TiSi 2 resistance:13-20μμΩ·cm; TiSi resistance:37μΩ·cm; Ti 5 Si 3 resistance:50-120μΩ·cm; TiN resistance:25-100μΩ·cm.

[0052] Ti-Si reaction mechanism and basis: Ti and Si have different diffusion rates, and their interface moves after diffusion. The diffusion principle follows Fick's second law and Kirkendall effect. The atomic radius of Ti is larger than that of Si, so the diffusion flux of Ti is larger than the diffusion flux of Si.

[0053] Therefore, the stability of the machine can be judged by the stable phase-unstable phase-stable phase reaction form: when the reaction thermodynamics plays a dominant role, the transition state Ti 5 Si 4 The formation temperature determines whether the reaction temperature of the machine is accurate. When the reaction kinetics plays a dominant role, the stable TiSi 2 The stability of the machine can be judged by the generation rate.

[0054] TiSi in RTP x The reaction is only TiSi x The relationship between thickness and temperature, that is, the relationship between the chemical reaction rate and temperature, follows the reaction thermodynamics formula Arrhenius formula, which is as follows:

[0055] k=Ae -Ea / RT ;

[0056] k--reaction rate;

[0057] A--pre-exponential factor, also known as Arrhenius constant;

[0058] Ea--reaction activation energy;

[0059] T--absolute temperature, unit K;

[0060] R--molar gas constant, unit J·mol -1 ·K -1 ;

[0061] e--the base of natural logarithm;

[0062] The variables involved in the present invention are reaction rate and temperature, and thus simulation calculations are performed based on the Arrhenius equation.

[0063] The following is a detailed introduction to the Ti-Si simulation reaction process:

[0064] The present invention simulates the use of wafers with a crystal orientation of <100> , substrate type is N / N + , the EPI Thinkness of the wafer is 4.9±5%μm, and RES is 0.4±5%ohm·cm; the substrate Thinkness is 725±15μm, and RES is 0.0013-0.0014ohm·cm. The above is calculated based on the actual production wafer using the wafer substrate doping concentration. The formula is as follows:

[0065] N=6.242*10 18 / ρ*10 Z ;

[0066] Z=(A 0 +A 1 x+A 2 x 2 +A 3 x 3 ) / (1+B 1 x+B 2 x 2 +B 3 x 3 );

[0067] x = logρ;

[0068] A 0 =-3.1083 B 1 =1.0265;

[0069] A 1 =-3.2626 B 2 =0.38755;

[0070] A 2 =-1.2196 B 3 =0.041833;

[0071] A 3 =-0.13923;

[0072] According to the National Standard of the People's Republic of China - Conversion Procedure for Resistivity and Dopant Concentration of Boron-doped and Phosphorus-doped Silicon Single Crystal, the wafer substrate concentration is 6.21614E19 (cm -3 ), the EPI concentration is 3.4788E16 (cm -3 ).

[0073] Ti-Si simulation reaction process:

[0074] The growth mode of the simulated wafer is to grow a 950 A metal Ti layer on a silicon substrate, and then extract the barrier thickness at 500-950℃, 45s with a 10℃ interval (the gas is N 2 , flow rate is 30 slm). The specific simulation process is as follows:

[0075] Step 1. Sputter 950A of Ti metal, see Figure 4 a.

[0076] Step 2. Generate TiSi at different temperatures by RTP annealing x Barrier, see Figure 4 b.

[0077] Step 3. Record the TiSi generated at the corresponding temperature x Thickness and remaining Ti thickness, the results are shown in Figure 5 and Fig.13 .

[0078] Depend on Figure 5 It can be seen that when other parameters are constant, increasing the temperature can increase the TiSi x The reaction rate and the consumption rate of Ti. x The overall reaction rate of +Ti is continuously increasing. The data shows that the reaction rate has an inflection point at 600℃. This is because not all Ti-Si reactant molecules can react due to collision. 600℃ provides enough activation energy for the new Ti-Si phase. Modern reaction rate theory describes that the two-molecule reaction passes through a transition state-activated complex, which has a higher potential energy than both the reactant molecules and the product molecules. The Ti-Si molecules that collide with each other reach a potential energy sufficient to overcome the reaction potential barrier and form a transition state to react. Continuing to increase the temperature reduces the potential energy.

[0079] By formula:

[0080]

[0081] x: ratio of Si to Ti;

[0082] The content of x can be obtained, as Figure 6 , we can see that there is a peak at 580-600℃, at which time a transition state is formed, and a new phase is formed at 600℃. Therefore, when we judge the machine status, we can use this inflection point to judge the actual temperature of the RTP machine. 2 and TiN during nitrogen annealing of magnetronsputtered Ti films) describes that at around 600°C, TiSi 2The phase formation further proves the existence of a non-stable transition phase.

[0083] According to the Arrhenius formula, the reaction equation for temperatures below 600°C is:

[0084] y=32071.111e -7847.90x (Ti-Si reaction rate)

[0085] The fitting results follow the Arrhenius equation, that is, the reaction rate is only related to temperature.

[0086] x: 1 / T.

[0087] Above 600℃ is a diffusion process. As the temperature increases, the diffusion rate increases linearly, so the formula is obtained:

[0088] y=-31.2832197791982+0.09097184728037*x(TiSi+Ti overall reaction rate)

[0089] The overall reaction rate of Ti+TiSix can be obtained by calculation. See the curve diagram for details. Figure 7 .

[0090] Therefore, the overall formula of the simulation results can be divided into two sections:

[0091] y=32071.111e -7847.90x (Within 600℃, growth thermodynamic factors play a major role);

[0092] y=-31.2832197791982+0.09097184728037*x(above 600℃, growth dynamics plays a major role);

[0093] The above formula is a theoretical simulation calculation value. In actual production, machine status, environmental factors, human factors, material factors, operating method factors, etc. may cause deviations from the simulation results. Therefore, the actual results only need to follow the relevant linearity.

[0094] S2. Conduct actual production experiments according to the parameters of the simulation calculation;

[0095] S3. Compare the production results with the fitting results, and determine the temperature status of the machine according to the temperature inflection point and the reaction rate slope;

[0096] S4. Determine the stability of the machine by predicting the diffusion results of different parameters in actual production based on the fitting results. The present invention determines the stability of the machine by the stable phase-unstable phase-stable phase reaction form: when the reaction thermodynamics plays a dominant role, the transition state Ti 5 Si 4The formation temperature determines whether the reaction temperature of the machine is accurate. When the reaction kinetics plays a dominant role, the stable TiSi 2 The stability of the machine can be judged by the generation rate.

[0097] The actual reaction results of Ti-Si are fitted with the simulation results:

[0098] 1. The generation of transition phase determines the temperature status of the machine

[0099] At this temperature, the growth thermodynamic factors play a major role. When the reaction temperature is 45s, the temperature is 560-580℃, which has enough energy to generate the transition state Ti 5 Si 4 According to the simulation results, it is known that Ti 5 Si 4 At 560℃, the slope of Si / Ti ratio begins to increase and reaches its peak at 580℃, which is the breakthrough energy barrier temperature. Figure 8 As a result, the Si / Ti ratio starts to increase at 560°C and reaches a peak at 580°C.

[0100] This method can also use this machine as the temperature anchor point to make other machines match this machine.

[0101] The actual reaction temperature is exponentially related to the reaction rate, and the relationship is as follows:

[0102] y=1207.71335620062e -3722.20317955589x

[0103] Following the Arrhenius formula, it is proved that growth thermodynamics plays a major role in this interval.

[0104] 2. Diffusion of stable phase determines machine stability

[0105] At this temperature, growth dynamics plays a major role, so it can be roughly judged that the diffusion depth is proportional to the temperature. When the machine is stable, the slope of the reaction rate at each temperature can basically remain consistent. According to the simulation results, when it is above 600℃, the slope of the function of temperature and reaction rate is 0.09097184728037. By carrying out the actual process under the same conditions, the following is obtained: Fig. 9 The results show that temperature is directly proportional to the reaction rate.

[0106] The actual reaction temperature is directly proportional to the reaction rate, and the relationship is as follows:

[0107] y=-13.6167173893023+0.07417120169109*x.

[0108] Following the principle of simulated diffusion, it is proved that growth dynamics play a major role in this interval.

[0109] The simple schematic diagram of the inflection point method can be found in Fig.11 The Si / Ti and temperature relationship curve shows that Si / Ti reaches its peak at 580°C. The simple principle diagram of the slope method can be found in Fig.12 The red curve shows that the Ti / Si reaction rate is not proportional and unstable; the green curve shows that there is an inflection point, and after the inflection point, the machine reaction rate is basically proportional and stable.

[0110] The method for monitoring the stability of the rapid thermal annealing equipment of the present invention is compared with the existing TC Wafer and thermometer monitoring method. The comparison results are shown in Table 1.

[0111] Table 1 Comparison results between the method of the present invention and the existing measurement method

[0112]

[0113] In summary, the method for monitoring the stability of rapid thermal annealing equipment of the present invention can monitor the stability of the RTP machine and predict the stability of TiSi in the production of Schottky diodes. x The thickness is to prevent the machine from being contaminated and affecting the WPH of production during the actual production process, and at the same time ensure that the purpose of reducing costs and increasing efficiency is achieved as much as possible in the machine.

[0114] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for monitoring the stability of a rapid thermal annealing device, characterized in that: The following steps are involved: S1. Through simulation calculation under different parameter conditions, the temperature law is obtained; S2. Conduct actual production experiments according to the parameters of the simulation calculation; S3. Compare the production result of step S2 with the fitting result of step S1, and determine the temperature state of the machine according to the temperature inflection point and the slope of the reaction rate; S4. Determine the machine stability by predicting the diffusion results of different parameters during actual production based on the fitting results.

2. The method for monitoring the stability of rapid thermal annealing equipment according to claim 1, characterized in that: In step S1 , a simulation calculation is performed based on the Arrhenius equation with reaction rate and temperature as variables.

3. The method for monitoring the stability of rapid thermal annealing equipment according to claim 1, characterized in that: In step S1, the growth mode of the wafer used in the simulation is to grow a layer of 950A metal Ti on a silicon substrate, and then extract the barrier thickness at 500-950°C with an interval of 10°C.

4. The method for monitoring the stability of rapid thermal annealing equipment according to claim 3, characterized in that: The simulation process is as follows: Step 1, sputtering 950A metal Ti on a silicon substrate; Step 2: Generate TiSi at different temperatures through RTP annealing x potential barrier; Step 3: Record the TiSi generated at the corresponding temperature x thickness and remaining Ti thickness.

5. The method for monitoring the stability of rapid thermal annealing equipment according to claim 1, characterized in that: The temperature law obtained by simulation calculation is as follows: y=32071.111e -7847.90x Below 600°C, growth thermodynamic factors play a major role; y=-31.2832197791982+0.09097184728037*x Above 600℃, growth kinetics factors play a major role.

6. The method for monitoring the stability of rapid thermal annealing equipment according to claim 1, characterized in that: When the reaction thermodynamics plays a dominant role, the accuracy of the reaction temperature of the machine is determined by the formation temperature of the transition state Ti5Si4; When reaction kinetics plays a dominant role, the stability of the machine is judged by the generation rate of stable TiSi2.

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