Heating rate planning method in rapid heat treatment process temperature control

Abstract

The invention discloses a temperature rise rate planning method in rapid heat treatment process temperature control, which belongs to the technical field of semiconductor process temperature control, and comprises the following steps: generating a temperature reference curve as a tracking target of the temperature rise rate planning method, the method comprises the steps that a polynomial trajectory planning function T (tau) is adopted, a primary derivation function of the polynomial trajectory planning function T (tau) on time tau is calculated, and then a temperature reference curve with trajectory planning is obtained in combination with a basic temperature reference curve function Tref [k]. The temperature reference curve is smoothened by adopting a polynomial method for trajectory planning in the field of motion control, so that the influence of sudden change generated when the target temperature is reached on temperature control is eliminated, and the adaptability of control algorithm parameters is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor process temperature control, and in particular relates to a heating rate planning method in rapid thermal treatment process temperature control. Background Art

[0002] Rapid Thermal Processing (RTP) is an advanced single-wafer heat treatment process. Compared with traditional batch heat treatment processes, RTP is more suitable for the miniaturization of integrated circuit feature sizes and is an indispensable process for advanced semiconductor manufacturing. RTP equipment has been listed as one of the key "bottleneck" equipment in the industry, and the temperature control of single wafers is the top priority of core technology.

[0003] In a typical RTP device, the heating system is the most important functional component of the device, which mainly includes a heating cavity, a magnetic levitation device, a halogen lamp and its reflector, etc. The measurement and control system mainly completes the closed-loop control of temperature, the control of cooling gas and the control functions of other auxiliary systems. In addition, it also has the function of communicating with the host computer, and also includes: halogen lamp control power amplifier unit, temperature control board, temperature sensor and its signal conditioning transmitter and other functional units.

[0004] In the prior art, such as Figure 2 As shown, the temperature reference curve generally starts from an initial temperature and increases to a target temperature at a set rate over time. The disadvantage of the prior art solution is that the temperature reference curve is not a smooth curve, that is, its derivative shows that a sudden change will occur when the target temperature is reached, which will affect temperature control. Summary of the invention

[0005] Based on the technical problems existing in the prior art, the present invention provides a method for planning the heating rate in the temperature control of a rapid heat treatment process, which solves the problem in the prior art that the sudden change generated when the temperature reference curve reaches the target temperature affects the temperature control, thereby improving the adaptability of the temperature control algorithm parameters.

[0006] According to the technical solution of the present invention, the present invention provides a method for planning the heating rate in the temperature control of a rapid heat treatment process, wherein the method includes generating a temperature reference curve as a tracking target of the heating rate planning method, wherein the temperature reference curve is a temperature reference curve with trajectory planning, which includes using a polynomial trajectory planning function, calculating a first derivative function of the polynomial trajectory planning function with respect to time, and then combining the basic temperature reference curve function to obtain a temperature reference curve with trajectory planning.

[0007] Furthermore, the heating rate planning method in the rapid thermal treatment process temperature control adopts the polynomial method of trajectory planning in the field of motion control to smooth the temperature reference curve, so as to eliminate the influence of the sudden change generated when reaching the target temperature on the temperature control, thereby improving the adaptability of the control algorithm parameters.

[0008] Furthermore, the method includes generating a temperature reference curve as a tracking target of the heating rate planning method, wherein the temperature reference curve is a temperature reference curve with trajectory planning. , which includes the following: Polynomial trajectory planning function T ( τ ) is expressed by the following function:

[0009] , Where τ is time, a 0 is a constant parameter, a 1 is the first function parameter, a 2 is the second function parameter, a 3 is the third function parameter, a 4 is the fourth function parameter, a 5 is the fifth function parameter, T 0 is the starting planning temperature, T 1 is the end planning temperature, R 0 is the initial planned temperature rate, R 1 is the end planning temperature rate, A 0 is the initial planned temperature acceleration rate, A 1 is the end of the planned temperature acceleration rate, t 0 is the starting planning time, t f Plan time for closure; Polynomial trajectory planning function T ( τ )The first derivative function of time τ is: , So we get: , in, k is a discrete time point; T ref [ k ] is the basic temperature reference curve function: , in, T init is the initial steady-state temperature, R* is the target heating rate, T * is the target temperature.

[0010] Furthermore, the rapid thermal processing equipment used therein includes a reaction chamber and a halogen tungsten lamp. A quartz bracket is arranged at the bottom of the reaction chamber through a magnetic suspension rotation system. A support ring is arranged on the quartz bracket. The support ring is used to place wafers. A plurality of temperature detection modules for measuring the temperature of the wafers are also arranged at the bottom of the reaction chamber. The halogen tungsten lamp is an array of halogen tungsten lamps arranged in concentric circles. The halogen tungsten lamp is installed in a reflective cover above the reaction chamber. The rapid thermal processing equipment also includes a temperature controller and an SCR module connected to the temperature detection module in sequence. The SCR module is connected to the halogen tungsten lamp. The heating rate planning method in the temperature control of the rapid thermal processing process runs in the temperature controller in the form of software code.

[0011] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. The present invention adopts the polynomial method of trajectory planning in the field of motion control to smooth the temperature reference curve to eliminate the influence of the sudden change generated when reaching the target temperature on the temperature control, thereby improving the adaptability of the control algorithm parameters.

[0012] 2. The fifth-order polynomial function used in the present invention can not only ensure that the temperature and temperature rate are continuous, but also ensure that the acceleration rate of the planning curve is continuous. The six boundary conditions fully utilize the physical meaning of the system and will not increase redundant parameters and degrees of freedom, and the applicability is optimal. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of a temperature reference curve with trajectory planning provided by the present invention.

[0014] Figure 2 It is a schematic diagram of a temperature reference curve in the prior art.

[0015] Figure 3 It is a structural schematic diagram of a typical rapid thermal processing equipment provided by the present invention.

[0016] Figure 4 It is a structural block diagram of the rapid thermal processing system provided by the present invention.

[0017] Figure 5 It is a schematic diagram of a typical wafer temperature curve, i.e., a temperature control curve, in a rapid thermal processing device. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0020] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0021] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0022] The present invention provides a method for planning the heating rate in the temperature control of a rapid thermal treatment process, belonging to the technical field of semiconductor process temperature control. The present invention includes generating a temperature reference curve as a tracking target of the heating rate planning method. The main further improvement of the present invention is that the temperature reference curve is a temperature reference curve with trajectory planning. , which includes using a polynomial trajectory planning function T ( τ ), calculate the polynomial trajectory planning function T ( τ ) is the first derivative of time τ, and then combined with the basic temperature reference curve function T ref [ k ] The temperature reference curve with trajectory planning of the present invention is obtained. The present invention adopts the polynomial method of trajectory planning in the field of motion control to smooth the temperature reference curve, so as to eliminate the influence of the sudden change generated when reaching the target temperature on the temperature control, thereby improving the adaptability of the control algorithm parameters. More specifically, it includes the following contents.

[0023] The function of the control algorithm (which includes the heating rate planning method) is to automatically adjust the system from one state to another, i.e. the target state, through mathematical formulas and internal parameters. In the RTP system, the wafer temperature is automatically adjusted to the target heating rate set by the user. R * and target temperature T* , from an initial steady-state temperature T init Adjust to another steady state. Conventional control algorithms are equipped with a temperature reference curve generator that is responsible for combining the setting information to generate a basic temperature reference curve. T ref As the tracking target of the control algorithm. The internal calculation of the existing temperature reference curve generator is expressed by the following calculation formula, and its output result is as follows Figure 2 shown.

[0024] , in, T ref [ k ] is the basic temperature reference curve function used in the prior art, k is a discrete time point, T init is the initial steady-state temperature.

[0025] Therefore, the disadvantage of this existing solution is that the temperature reference curve is not a smooth curve, that is, its derivative shows that a sudden change will occur when the target temperature is reached, and this sudden change will affect the temperature control.

[0026] The present invention adds trajectory planning processing on the basis of the conventional temperature reference curve to eliminate the difficulty in reaching the target temperature. T * The sudden change problem occurs when the temperature reference curve T ref After generation, the curve is processed by polynomial trajectory planning and a new temperature reference curve is obtained. . Polynomial trajectory planning function T ( τ ) is expressed by the following function: , Among them, τ is time (the time of planning), a 0 to a 5 is the function parameter, a 0 is a constant parameter, a 1 is the first function parameter, a 2 is the second function parameter, a 3 is the third function parameter, a 4 is the fourth function parameter, a 5 is the fifth function parameter, , in, T 0 is the starting planning temperature, T 1 is the end planning temperature, R0 is the initial planned temperature rate, R 1 is the end planning temperature rate, A 0 is the initial planned temperature acceleration rate, A 1 is the end of the planned temperature acceleration rate, t 0 is the starting planning time, t f Plan time for the end.

[0027] The fifth-order polynomial function used in the present invention can not only ensure that the temperature and temperature rate are continuous, but also ensure that the acceleration rate of the planning curve is continuous. The six boundary conditions fully utilize the physical meaning of the system and will not increase redundant parameters and degrees of freedom, and the applicability is optimal.

[0028] In addition, the above function is expressed in temperature form, and the present invention uses this polynomial trajectory planning function T ( τ ) is the first derivative function of time τ, that is: , in, Planning function for polynomial trajectories T ( τ ) is the first derivative of time τ; Therefore, the following application formula is obtained: , where the starting planning time is applied t 0 is set to 0.

[0029] That is, the temperature reference curve with trajectory planning of the present invention can be obtained by combining the original basic temperature reference curve function and the polynomial trajectory planning function. ,in, T ref [ k ] is the basic temperature reference curve function, It is the temperature reference curve function with trajectory planning.

[0030] Temperature reference curve with trajectory planning like Figure 1 As shown by the dotted line in Figure 1 The solid line in the middle is the basic temperature reference curve. It can be seen that the sudden change problem caused by the temperature reference curve of the present invention when reaching the target temperature has been eliminated.

[0031] As a more specific supplementary explanation, rapid thermal processing is an advanced single-chip wafer heat treatment process. The typical RTP heating system mainly includes a heating chamber, a magnetic levitation device, a halogen tungsten lamp and its reflector, etc. The measurement and control system mainly completes the closed-loop control of temperature, the control of cooling gas and the control functions of other auxiliary systems. In addition, it also has the function of communicating with the host computer, and also includes: halogen tungsten lamp control power amplifier unit, temperature control board, temperature sensor and its signal conditioning transmitter and other functional units.

[0032] In RTP applications, some processes require that the wafers are not contaminated by impurity gases during the heating process, so a higher vacuum degree is required. The vacuum system is usually implemented with a single-stage or two-stage vacuum pump according to the specific vacuum degree requirements.

[0033] Some processes require gas protection, or high-temperature nitriding, oxidation, etc. Therefore, the system must provide multiple atmosphere sources at the same time, such as argon, nitrogen, and oxygen. Each gas is controlled by a switch valve, and a pressure regulating valve is installed on a single pipeline near the entrance of the reaction chamber to control the pressure of the atmosphere. Generally, when switching different gases, it is necessary to exhaust the residual gas in the original closed chamber. Therefore, before switching the input gas, it is necessary to evacuate the chamber first, and then introduce the set gas. This requires software design to achieve this.

[0034] In order to ensure that the wafer is not contaminated when it is taken and placed, a two-degree-of-freedom robot is used to perform the operation of taking and placing the wafer.

[0035] In the application of the system, most processes have strict requirements on the temperature curve of the wafer, so not only fast heating but also fast cooling is required. The method of introducing low-temperature gas or normal temperature gas can be used to simply and effectively achieve cooling, and the type of gas introduced may be different according to the specific process requirements. In addition, for safety reasons, the heating chamber wall is cooled by cooling water circulation.

[0036] More specifically, see Figure 3 In the rapid thermal processing equipment (RTP equipment for short) used in the present invention, the heating system is mainly composed of a reaction chamber 5 (heating chamber), a halogen tungsten lamp 1, a quartz bracket 2 (rotating quartz cylinder), and a magnetic suspension rotation system. The reaction chamber 5 is a closed chamber and provides installation positions for other components. The side of the reaction chamber 5 has a gas inlet / outlet. The bottom of the reaction chamber 5 is provided with a quartz bracket 2 through a magnetic suspension rotation system. A support ring 3 (silicon carbide support ring) is provided on the quartz bracket 2. The support ring 3 is used to place a wafer 6. The wafer 6 can rotate around its center in a horizontal plane to make the heating effect more uniform. A number of pyrometers 4 for measuring the temperature of the wafer, i.e., a temperature detection module, such as an optical fiber probe, are also provided at the bottom of the reaction chamber 5.

[0037] The halogen lamp is an array of halogen lamps arranged in concentric circles, such as a concentric hexagonal array of halogen lamps. The halogen lamps are installed in a reflective cover above the reaction chamber. Halogen lamps are used to heat wafers. Under normal operation, their temperature is in the range of 600-1650K, and the radiation energy is concentrated in the wavelength range of 1-5 microns, which belongs to infrared radiation. This high-density arrangement of heat sources can improve the uniformity of the temperature field to a high degree at the level of mechanical structure. The halogen lamp array is divided into several groups according to the radial distance. The number of lamp groups is generally consistent with the number of pyrometers, and the power of each group of lamps can be controlled separately.

[0038] In order to prevent the influence on the wafer temperature, a non-contact pyrometer is used for temperature measurement. Generally, multiple pyrometers are used to measure the temperature at different radial positions of the wafer at the same time to improve the temperature uniformity. Figure 5 This is a typical temperature control curve. In this example, there are seven pyrometers that measure the temperature at different locations on the wafer. In the figure, there are seven curves from T1 to T7. Since the temperature consistency at the seven locations is good, the seven curves appear to have a high degree of overlap.

[0039] The temperature control indicators of the rapid thermal treatment process generally include temperature and temperature difference. The temperature indicator refers to the overall need for multiple temperatures to meet the various requirements specified by the customer, such as heating rate, overshoot, and steady-state error. The temperature difference indicator refers to the numerical difference between each temperature. Generally, the difference between the highest temperature and the lowest temperature at the same time is used as the temperature difference indicator.

[0040] See also Figure 4 The structure of the rapid thermal processing system in the RTP device includes a temperature controller and an SCR (silicon controlled rectifier) ​​module which are sequentially connected to the temperature detection module; the temperature detection module (pyrometer 4 in the embodiment) is connected to the reaction chamber of the RTP device to collect the radiation signal of the wafer for temperature measurement; the SCR module is connected to the halogen tungsten lamp (heating component) of the reaction chamber of the RTP device to output voltage to the halogen tungsten lamp to control the heating power of the halogen tungsten lamp. The temperature controller is used for data processing and implementation of control algorithms, etc. It receives the temperature measured by the temperature detection module, and adjusts the signal output to the SCR module through the algorithm to achieve control of the heating power. The method of the present invention runs in the temperature controller in the form of software code.

[0041] The planning algorithm proposed in this invention is a key software module in the main body of the independently developed temperature control algorithm, which can be applied to different types of equipment. Currently, the main application equipment includes RTA, IDP and IDP Plus. The difficulties of the temperature control algorithm include: 1. Strong coupling relationship. Silicon wafers are large in size, and there is a strong coupling relationship between the multi-temperature zone controls, which makes it difficult to quickly and evenly control the temperature.

[0042] 2. High adaptability requirements. RTP equipment has a wide variety of processes and requires high algorithm adaptability. An algorithm is often required to perform well under a variety of temperatures, pressures, heating rates, and a variety of structural pieces.

[0043] 3. High control accuracy is required. Indicators such as temperature difference and overshoot often need to be less than 1.0°C, and the heating time needs to be customized, which brings difficulties to the selection of control schemes and parameter settings.

[0044] 4. Nonlinear control: In model-based design, the nonlinearity, time-varying, and delay of the temperature control system increase the difficulty of modeling.

[0045] The main contribution of the present invention is to solve the difficulty of algorithm adaptability so as to ensure the control accuracy. In terms of algorithm adaptability, the temperature controller can use a set of algorithm parameters to cover a certain wide range of process settings, i.e., target temperature, target heating rate and process pressure, without affecting the performance of the temperature curve. In practical applications, the problem encountered is that the algorithm parameters that are well debugged and have good temperature curve performance under the conditions of the basic working condition setting are affected by the user changing the setting (matching the requirements of the new process formula) and the temperature curve performance is mostly affected and exceeds the index, so it is necessary to debug again under the conditions of the new formula. In short, engineers need to debug an additional set of parameters with good performance to apply to the new formula setting. By analogy, several different process formula settings require several sets of algorithm parameters to meet the usage indicators, which requires engineers to debug frequently in a targeted manner. The essential reason is that the rate change of the reference curve is discontinuous. Due to physical limitations, the system delay formed by the limited number and limited dynamic halogen lamps cannot react and track the reference curve of the sudden speed change in time, resulting in the curve overshoot phenomenon affecting the temperature control performance. At the same time, the discontinuity of the rate change also leads to redundant control output.

[0046] In summary, the present invention adopts the polynomial method of trajectory planning in the field of motion control to smooth the temperature reference curve to eliminate the influence of the sudden change generated when reaching the target temperature on the temperature control, thereby improving the adaptability of the control algorithm parameters.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for planning the heating rate in temperature control of a rapid thermal treatment process, characterized in that: The heating rate planning method in the temperature control of the rapid thermal treatment process includes generating a temperature reference curve as a tracking target of the heating rate planning method. The temperature reference curve is a temperature reference curve with trajectory planning, which includes using a polynomial trajectory planning function, calculating the first derivative function of the polynomial trajectory planning function with respect to time, and then combining the basic temperature reference curve function to obtain the temperature reference curve with trajectory planning.

2. The method for planning the heating rate in the temperature control of the rapid thermal treatment process according to claim 1, characterized in that: The polynomial method of trajectory planning in the field of motion control is used to smooth the temperature reference curve to eliminate the influence of sudden changes when reaching the target temperature on the temperature control, thereby improving the adaptability of the control algorithm parameters.

3. The method for planning the heating rate in the temperature control of the rapid thermal treatment process according to claim 1, characterized in that: The temperature reference curve is the temperature reference curve with trajectory planning , which includes the following: Polynomial trajectory planning function T ( τ ) is expressed by the following function: ， Where τ is time, a 0 is a constant parameter, a 1 is the first function parameter, a 2 is the second function parameter, a 3 is the third function parameter, a 4 is the fourth function parameter, a 5 is the fifth function parameter, T 0 is the starting planning temperature, T 1 is the end planning temperature, R 0 is the initial planned temperature rate, R 1 is the end planning temperature rate, A 0 is the initial planned temperature acceleration rate, A 1 is the end of the planned temperature acceleration rate, t 0 is the starting planning time, t f Plan time for closure; Polynomial trajectory planning function T ( τ ) with respect to time τ is: ， So we get: ， in, k is a discrete time point; T ref [ k ] is the basic temperature reference curve function: ， in, T init is the initial steady-state temperature, R * is the target heating rate, T * is the target temperature.

4. The method for planning the heating rate in the temperature control of the rapid thermal treatment process according to claim 3, characterized in that: The rapid thermal processing equipment used in the invention comprises a reaction chamber and a halogen tungsten lamp. A quartz bracket is arranged at the bottom of the reaction chamber through a magnetic suspension rotation system. A support ring is arranged on the quartz bracket. The support ring is used to place wafers. A plurality of temperature detection modules for measuring the temperature of the wafers are also arranged at the bottom of the reaction chamber. The halogen tungsten lamp is a halogen tungsten lamp array arranged in concentric circles. The halogen tungsten lamp is installed in a reflective cover above the reaction chamber. The invention also comprises a temperature controller and an SCR module which are sequentially connected to the temperature detection module. The SCR module is connected to the halogen tungsten lamp. The heating rate planning method in the temperature control of the rapid thermal processing process runs in the temperature controller in the form of software code.

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