TWI635261B - Method for monitoring temperature uniformity of susceptor - Google Patents

Abstract

The invention proposes a method for monitoring the uniformity of the temperature of the pedestal. Silicon dioxide is formed on the surface of the wafer, the wafer is placed on the pedestal for heating, and hydrogen is introduced at the same time. The reaction changes the optical characteristics of the silicon dioxide film. The higher the temperature, the faster the reduction reaction rate in the region, and the more the optical characteristics of the silicon dioxide film change. From this, the temperature uniformity is calculated. In addition, the Silicon oxide can be removed by wet etching, which solves the problem of wafer recycling without causing pollution to the reaction chamber.

Description

Method for monitoring temperature uniformity of pedestal

The invention relates to the field of semiconductor manufacturing, in particular to a method for monitoring temperature uniformity of a pedestal.

In the semiconductor manufacturing process, wafers usually need to be placed on the pedestal in the reaction chamber for corresponding thin film deposition, etching and other processes. Since the reaction needs to be performed at a certain temperature, the temperature is usually provided by the pedestal. The susceptor heats the wafer. As the size of the wafer becomes larger, the pedestal also becomes larger, but there will be a certain deviation in the temperature uniformity provided by the pedestal. Different temperatures lead to different reaction results and directly affect the yield of the wafer. Therefore, when the base is at high temperature (greater than 1000 degrees Celsius), it is usually necessary to monitor its temperature uniformity.

Please refer to FIG. 1, which is a schematic diagram of a system structure for monitoring the temperature in a reaction chamber in the prior art. The wafer 20 is placed on a susceptor 10, both of which are located in the reaction chamber 30. There are a plurality of infrared lamps 40 outside. The reaction chamber 30 is provided with a quartz window 31. A pyrometer 32 is provided at the quartz window 31 for monitoring the temperature in the reaction chamber 30. A temperature difference thermocouple 33 is also provided on one side of 30. However, the readings of the pyrometer 32 through the quartz window 31 are easily affected by the coating layer and cause inaccurate readings; different positions will also As a result, the readings of the thermocouple 33 are different, and in the above solution, only a single point temperature monitoring can be performed.

In addition, in the prior art, a 4-point probe test method is usually used to test temperature uniformity. The 4-point probe test method first implants donors or receptors on the surface of the wafer; then, the wafer is transferred to the reaction chamber and placed on the base; then, the temperature is raised to the temperature required for the process, and the implanted The donor or acceptor will be activated and diffused at high temperature, which will affect the resistivity of the wafer surface. Unload the wafer and use a 4-point probe to test the resistivity of the wafer surface to calculate the temperature uniformity.

However, first of all, the 4-point probe test method is a destructive method, which can cause destructive damage to the wafer, resulting in difficult wafer recovery. Second, additional implanted donors or receptors can affect the reaction chamber. Clean and pollute the reaction chamber. Therefore, a method that can monitor the temperature uniformity of the pedestal is needed to overcome the above problems.

The purpose of the present invention is to provide a method for monitoring the temperature uniformity of the pedestal, which can comprehensively monitor the temperature uniformity, and the wafers are easy to recover without causing pollution to the reaction chamber.

In order to achieve the above object, the present invention provides a method for monitoring temperature uniformity of a pedestal, including the steps of: providing a wafer, forming at least one layer of silicon dioxide on the wafer; and placing the wafer on a pedestal; Raise the internal temperature of a reaction chamber to the temperature required for a process, and pass hydrogen into the reaction chamber; unload the wafer, and test the change in optical characteristics of silicon dioxide on the surface of the wafer to obtain the temperature. Uniformity.

Further, changes in the optical characteristics of the silicon dioxide tested on the surface of the wafer include: Step: After the at least one layer of silicon dioxide is formed on the wafer surface, the optical characteristics of the silicon dioxide are measured for the first time; after the wafer is heated and reacted with hydrogen, the optical characteristics of the silicon dioxide are measured. A second measurement was performed, and the change in optical characteristics was obtained from the difference between the first measurement and the second measurement.

Further, the silicon dioxide is two layers.

Further, the silicon dioxide is formed by chemical vapor deposition.

Further, the thickness of the silicon dioxide ranges from 50 angstroms to 500 angstroms.

Further, the temperature required for this process is greater than or equal to 1000 degrees Celsius.

Further, the change in the optical characteristics of the silicon dioxide at several points on the wafer surface is tested to obtain the uniformity of the change in the optical characteristics of the silicon dioxide on the wafer surface.

Further, the optical characteristics of the silicon dioxide include a refractive index and an extinction coefficient.

Compared with the prior art, the beneficial effects of the present invention mainly include: forming a silicon dioxide film on the surface of the wafer, placing the wafer on a susceptor for heating, and simultaneously introducing hydrogen into the reaction chamber to reduce the effect of hydrogen The reaction with silicon dioxide changes the optical characteristics of the silicon dioxide film. The higher the temperature, the faster the reduction reaction rate, and the more the optical characteristics of the silicon dioxide film change. From this, the temperature uniformity is calculated. The silicon dioxide formed on the round surface can be removed by wet etching, which solves the problem of wafer recycling without causing pollution to the reaction chamber.

current technology:

10‧‧‧ base

20‧‧‧ wafer

30‧‧‧ reaction chamber

31‧‧‧Quartz window

32‧‧‧ Pyrometer

33‧‧‧Thermocouple

40‧‧‧ Infrared tube

this invention:

20‧‧‧ wafer

60‧‧‧ Silicon dioxide

FIG. 1 is a schematic structural diagram of a system for monitoring temperature in a reaction chamber in the prior art; FIG. 2 is a flowchart of a method for monitoring temperature uniformity of a pedestal according to an embodiment of the present invention; FIG. 3 is a schematic structural diagram of a wafer for testing temperature uniformity according to an embodiment of the present invention.

The method for monitoring the uniformity of the temperature of the pedestal according to the present invention will be described in more detail below with reference to the schematic diagram, which shows the preferred embodiment of the present invention. It should be understood that those skilled in the art can modify the invention described herein while still realizing the present invention. Advantageous effects of the invention. Therefore, the following description should be understood as widely known to those skilled in the art, and not as a limitation on the present invention.

In the interest of clarity, not all features of an actual embodiment are described. In the following description, well-known functions and structures are not described in detail because they may confuse the present invention with unnecessary details. It should be considered that in the development of any actual embodiment, a large number of implementation details must be made to achieve the developer's specific goals, such as changing from one embodiment to another in accordance with system- or business-related restrictions. In addition, it should be considered that such development work may be complicated and time-consuming, but it is only routine work for those skilled in the art.

The invention is described in more detail by way of example in the following paragraphs with reference to the drawings. The advantages and features of the invention will be apparent from the following description and claims. It should be noted that the drawings are in a very simplified form and all use inaccurate proportions, which are only used to facilitate and clearly assist the description of the embodiments of the present invention.

Please refer to FIG. 2. In this embodiment, a method for monitoring temperature uniformity of a pedestal is provided, including steps: S100: providing a wafer, and forming at least one layer of silicon dioxide on the wafer; S200: placing the crystal The circle is placed on a base; S300: heating up to the temperature required for a process, and introducing hydrogen into a reaction chamber; S400: unloading the wafer and testing the change in optical characteristics of silicon dioxide on the surface of the wafer to obtain temperature uniformity.

Specifically, referring to FIG. 3, at least one layer of silicon dioxide 60 is formed on the surface of the wafer 20. In this embodiment, two layers of silicon dioxide 60 are formed. The silicon dioxide 60 is formed by chemical vapor deposition (CVD). The thickness of the silicon dioxide 60 ranges from 50 angstroms to 500 angstroms, for example, 300 angstroms.

The temperature is increased to the temperature required for the process, and hydrogen is introduced into a reaction chamber. Generally, the temperature required for the process is 1000 degrees Celsius or more. When the temperature is less than 1000 degrees Celsius, the uniformity of temperature will not affect the reaction. As a result of a large difference, the temperature uniformity is tested at a preferred temperature of 1000 ° C or higher. The introduced hydrogen gas will undergo a reduction reaction with silicon dioxide on the wafer surface at high temperature, which will change the optical characteristics of silicon dioxide. The higher the temperature, the faster the reduction reaction rate, and the more the optical characteristics of the silicon dioxide film change. Many, the temperature uniformity can be estimated from this.

Wherein, testing the change in the thickness of the silicon dioxide on the wafer surface includes the steps of: after forming at least one layer of silicon dioxide 60 on the surface of the wafer 20, measuring the optical characteristics of the silicon dioxide 60 for the first time; After increasing the temperature and reacting with hydrogen, the optical characteristics of the silicon dioxide 60 were measured a second time. The difference between the first measurement and the second measurement was used to obtain the change in the optical characteristics, and then the temperature uniformity was calculated. Specifically, it is also possible to test the change in optical characteristics of silicon dioxide at several points on the wafer surface, so as to obtain the change in optical characteristics of silicon dioxide on the wafer surface. Uniformity of temperature and temperature uniformity.

In this embodiment, the optical characteristics of the silicon dioxide may be an extinction coefficient or a refractive index, and the light characteristics may change as the silicon dioxide and hydrogen change.

In summary, in the method for monitoring the uniformity of the temperature of the pedestal provided by the embodiment of the present invention, silicon dioxide is formed on the surface of the wafer, the wafer is placed on the pedestal to heat up, and at the same time hydrogen is passed in, and the hydrogen is used for reduction It reacts with silicon dioxide to change the optical characteristics of the silicon dioxide film. The higher the temperature is, the faster the reduction reaction rate is, and the more the optical characteristics of the silicon dioxide film are changed. From this, the temperature uniformity is calculated. In addition, The silicon dioxide formed on the wafer surface can be removed by wet etching, which solves the problem of wafer recycling without causing pollution to the reaction chamber.

The above are only preferred embodiments of the present invention, and do not play any limiting role on the present invention. Any person skilled in the art, within the scope not departing from the technical solution of the present invention, make any equivalent replacement or modification to the technical solution and technical content disclosed in the present invention without departing from the technical solution of the present invention. The content still falls within the protection scope of the present invention.

Claims (6)

A method for monitoring the temperature uniformity of a pedestal includes the steps of: providing a wafer, forming at least one layer of silicon dioxide on the wafer; placing the wafer on a pedestal; heating up to a temperature required for a process, Hydrogen gas is introduced into a reaction chamber, and the temperature required for the process is 1000 degrees Celsius or higher; the wafer is unloaded, and the optical characteristics of silicon dioxide on the wafer surface are tested for changes in the optical characteristics of the reaction chamber The uniformity of temperature, wherein testing the change in the optical characteristics of silicon dioxide on the wafer surface includes the following steps: after forming at least one layer of silicon dioxide on the surface of the wafer, performing the first step on the optical characteristics of the at least one layer of silicon dioxide One measurement; after the wafer is heated up and reacted with hydrogen gas, the second measurement of the optical characteristics of the silicon dioxide is performed, and the dioxide is obtained from the difference between the first measurement and the second measurement. Changes in the optical properties of silicon. The method for monitoring temperature uniformity of a pedestal according to claim 1, wherein the silicon dioxide has two layers. The method for monitoring temperature uniformity of a pedestal according to claim 1, wherein the silicon dioxide is formed by chemical vapor deposition. The method for monitoring temperature uniformity of a pedestal according to claim 1, wherein the thickness of the silicon dioxide ranges from 50 angstroms to 500 angstroms. The method for monitoring temperature uniformity of a pedestal according to claim 1, wherein the change in the optical characteristics of the silicon dioxide at several points on the wafer surface is tested to obtain the change in the optical characteristics of the silicon dioxide on the wafer surface. Uniformity. The method for monitoring temperature uniformity of a pedestal according to claim 1, wherein the optical characteristics of the silicon dioxide include a refractive index and an extinction coefficient.