JP2002016117A - Semiconductor wafer provided with processing temperature measuring method and temperature measuring method of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the intra-face distribution of a wafer temperature which hourly changes and is required to be accurately measured by an RTA process cannot precisely be measured in a conventional method. SOLUTION: The intra-face distribution of the wafer temperature which hourly changes a real time basis can be measured by providing a thin film-like temperature measuring element for a semiconductor wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process involving a heat treatment in a semiconductor manufacturing process. By measuring a process temperature, it is possible to check the uniformity in a wafer process temperature plane and to adjust the temperature uniformity in a heat treatment apparatus. The present invention relates to a semiconductor wafer used for a semiconductor device.

[0002]

2. Description of the Related Art A heat treatment step is one of the important steps in semiconductor manufacturing. In particular, in recent years, a single-wafer rapid heating (RTA) capable of raising and lowering the temperature in a short time has replaced the batch type heating (FA) that requires a long time for raising and lowering the temperature, which has been conventionally performed. ) Has come to be used. The change in the heating method is due to the emergence of a new manufacturing process, such as the need for thinner oxide films and the need for new material capacitance films (PZT, BST).

[0003] In the heat treatment process, the most important thing is accurate control of the wafer temperature. Therefore, FA, RTA
In both heating methods, the apparatus has been developed and improved so that a desired temperature profile can be obtained by accurately measuring the wafer temperature and controlling the heat source. Conventionally, thermocouples and radiation thermometers have been used as temperature monitors for device control. By the way, these temperature monitors can measure only the average value in the vicinity of the point where the thermocouple is in contact or in the area observed by the radiation thermometer. Further, since the thermocouple is often brought into contact with the back surface of the wafer due to the possibility of metal contamination, the time response to the temperature of the object to be measured is poor. Regarding the method of measuring the temperature inside the furnace, Bi / Japanese Patent Application Laid-Open No. 6-265414 describes whether the applicable temperature can be used for the oxidation and annealing processes.
A method of measuring a temperature from a thermoelectromotive force generated in an Sb superlattice, a method of obtaining a temperature from a desorption rate of an atom adsorbed on a dangling bond on a silicon substrate surface disclosed in JP-A-6-283589, Japanese Patent Application Laid-Open No. 7-27634 discloses a method of obtaining a temperature from the thermal expansion of a wafer supporting member. However, in these methods, steps that can be used may be limited due to problems such as contamination.

[0004] In terms of accurate control of the wafer temperature, in-plane uniformity of the wafer temperature is also important. In the FA process, since the temperature of the wafer and the wafer atmosphere change while maintaining a substantially thermal equilibrium state, it is considered that the in-plane distribution of the wafer temperature at the time of temperature rise / fall also conforms to the in-plane distribution at the steady state. Therefore, the temperature uniformity can be checked by making the in-plane temperature distribution in a steady state uniform, and it is sufficient to measure the change in the thickness of the oxide film formed by the heat treatment and the change in the sheet electric resistance of the silicide film. On the other hand, the RTA process can easily manage the thermal budget and is highly applicable to the above-described new process. However, since the wafer and the wafer atmosphere are heated in a thermally non-equilibrium state, an in-plane distribution of the wafer temperature easily occurs during the process. In addition, it shows completely different in-plane distributions during the temperature rise / fall and the steady state where the temperature changes rapidly. In the process using RTA, the success or failure of the process such as nucleation of crystal growth depends on whether the temperature rises or before and after switching to the steady state. In order to improve the yield, the uniformity of the in-plane temperature distribution during the temperature rise and steady state is important. Of particular importance. However, the conventional measurement method using the change in the oxide film thickness or the sheet electric resistance cannot obtain the in-plane distribution of the wafer temperature at the time of the temperature increase / decrease of the RTA process and the steady state. This is because what is obtained by these measurements is the result of going through steps of temperature rise, steady state, and temperature drop, and the in-plane temperature distribution changes with time in each step.

In order to measure the in-plane distribution of the wafer temperature during the RTA process, which changes every moment, a wafer having a thermocouple tip embedded in the surface of the wafer immediately before the heat treatment is used. As such a wafer, Sensarray of the United States of America deals with a dummy wafer in which a plurality of thermocouples are embedded. Therefore, we asked Sensarray to embed a thermocouple at each point in Fig. 1 on a wafer with a film structure just before heat treatment, and measure the in-plane distribution of the wafer temperature during the RTA process. I decided that. In order to improve the time response, the thermocouple is embedded directly in the film to be measured. FIG. 2 shows an example in which the in-plane distribution of the wafer temperature is measured using the wafer thus prepared. At the same time, the temperature differences at the other four points with respect to the center of the wafer are also shown. As a result of this measurement, it was confirmed that the in-plane distribution of the wafer temperature changed every moment during the process. In addition, this measurement confirmed that the in-plane distribution of the wafer temperature depends on the temperature rise / fall rate, the gas flow rate, and the gas type. Known examples considered on the assumption that the temperature distribution in the wafer surface is measured include:
Utilizing expansion of gas confined in a sealed space (JP-A-5-335284), and using a thermocouple as in some of the claims of the present invention (JP-A-6-3105)
No. 80) and one utilizing the fact that the reflectance of light varies depending on the temperature (Japanese Patent Application Laid-Open No. 8-313368). Of these, Japanese Patent Application Laid-Open No.
In the method described in JP-A-335284, a non-contact temperature measuring means such as a laser displacement meter must be provided in the heat treatment apparatus, and the method lacks versatility. Further, depending on the size and density of the space for sealing the gas, heat conduction in the wafer surface is hindered, and there is a concern that an error from an actual product may increase. JP-A-8-31336 using light reflectance
No. 8 also has the disadvantage that it must be provided with light irradiation-detection means. Another problem is that the temperature cannot be measured for an optically transparent substance. The method described in JP-A-6-310580 using a thermocouple is the same as the method using a thermocouple described in the present invention, but is inferior to the present invention in that a thermocouple is reliably formed.

[0006]

By the way, in the construction of the RTA process in the above experiment, not only the temperature rise / fall rate, the gas flow rate, the gas type, the process time, but also the in-plane distribution of the amount of heat incident on the wafer. It turns out that you also need to be careful. Therefore, a normal RTA apparatus is provided with a means for adjusting the heat input distribution. However, the means for measuring the in-plane distribution of the wafer temperature is insufficiently developed. Since the in-plane distribution of the wafer temperature changes with time, the measurement method using the change in the oxide film thickness or sheet electric resistance, which has been conventionally used for the purpose of improving the in-plane uniformity of the FA process, is not suitable. As a method of obtaining the time change of the wafer temperature distribution in real time, it is conceivable to use a wafer in which the thermocouple used in the above experiment is embedded. However, also in this method, when the number of measurement points increases, a cable for extracting a signal hinders heat input (for example, in the case of lamp heating, a shadow is formed on a wafer), and the uniformity measurement is disturbed. Therefore, in order to improve the in-plane uniformity in the RTA process, it is necessary to perform a multi-point measurement of the wafer temperature that does not hinder heat input and heat conduction in the wafer surface. The number of measurement points varies depending on the wafer diameter and chip area, but at least 15 points are considered necessary. Further, it is desirable that the temperature measuring element be as small as possible in order to eliminate the delay of the time response due to heat conduction.

[0007]

As a means for solving the above-mentioned problems, a semiconductor wafer in which a temperature measuring element for measuring a temperature by a thermocouple, a change in electric resistance, or the like is formed into a thin film is considered. Thin film-shaped temperature measuring elements made by repeatedly using processes such as film formation, resist coating, exposure, and etching, like ordinary semiconductor devices, are small in size, so their time response is improved, and they can be used for multipoint measurement. Easy to correspond. Further, by providing a pad for taking out a signal line at the edge of the wafer and forming wiring up to that end in the wafer manufacturing process, a structure that does not hinder heat input and heat conduction in the wafer surface can be obtained.

[0008]

FIG. 3 shows a first embodiment of the present invention. Here, an example is shown in which a thermocouple is formed on the entire surface of the wafer so that it can be used for a TEG wafer for process construction or for a device QC. 31 is a thermocouple element made of a thin film. Reference numeral 32 denotes a pad for extracting a signal from the thermocouple. FIGS. 4A and 4B are enlarged plan views and cross-sectional views. 41 is a first metal film A and 42 is a second metal film B, which forms a thermocouple. The manufacturing process of this element is as shown in FIG. First, a metal film A (41) is formed on a base film such as an oxide film by sputtering, CVD, or the like. Resist (5
1) A metal film A and, if necessary, a fine wiring pattern made of the metal film A are formed by coating, exposing, and etching. Next, an interlayer insulating film (44) such as SiO2 is deposited, and a contact hole (52) for forming a pad for taking out a thermocouple and a signal line is formed by etching again. Further, a metal film B (42) is deposited, and a wiring pattern of the thermocouple and the metal film B is formed by etching.
The protective film (53) is formed as necessary, for example, when the temperature measurement target is a metal film. When the temperature measurement target is the metal film B, a thermocouple can be formed by a method as shown in FIG. In this case, a contact hole for forming a pad for taking out a signal line from the metal film A needs to be formed not only in the interlayer insulating film but also in the metal film B. With the structure as shown in FIGS. 4 and 6, the junction between the two metals can be made dense, and a thermocouple can be reliably formed. In addition, the ratio of the thermocouple / wiring to the wafer area can be minimized by forming the wiring layer for extracting signals from the thermocouple in a two-stage structure, and the heat conduction in the wafer surface by the wiring layer can be minimized. And heat input from the outside is hardly hindered. Here, an example is shown in which the pad portion is located at the edge of the wafer, but the pad portion may be located near the thermocouple.

Here, the thermocouple is formed on the entire surface of the wafer. However, as shown in FIG. 7, the effect is substantially the same even if a TEG portion using a thermocouple is provided in a part of a semiconductor wafer for product.

[0010] However, thermocouples are generally alloys, and the application temperature range is often limited. In the case of an alloy, since the physical value of the thermoelectromotive force depends on the mixing ratio of the metal, it is difficult to form a thermocouple with stable characteristics by micromachining as shown in FIG. FIG. 8 shows a second embodiment of the present invention as an alternative in that case. Reference numeral 81 denotes a temperature measuring element for measuring a temperature from a change in electric resistance value due to a temperature change. In this method, the relationship between the temperature and the electric resistance value of the element material is measured in advance, and the temperature is measured from the electric resistance value. Platinum is known as a metal that can be used as a temperature measuring element from a low temperature to a high temperature. Platinum is one kind of metal, and a stable thin film can be formed by sputtering or the like. The forming process is almost the same as the forming process of the first metal film A in the first embodiment. However, unlike the case of a thermocouple, it is desirable to form a serpentine pattern in order to increase the element length with a small contact area with the wafer. If the operating temperature is below the endurance temperature of the material, metals other than platinum (nickel,
The same applies to the case where an insulator (such as diamond) or a semiconductor (such as silicon or germanium) is used. It is desirable to use the one used in the product wafer as much as possible in consideration of contamination and process compatibility.

[0011]

The following effects can be obtained by using the wafer in which the temperature measuring element of the present invention is embedded. RTA
By forming a thin-film temperature measuring element on the entire surface or a part of the TEG wafer for process construction, it is easy to confirm and improve the uniformity of the RTA process in the wafer temperature plane. By forming a thin-film temperature measuring element on the entire surface or a part of the wafer for the equipment QC, it is easy to confirm the deterioration of the in-plane uniformity due to the daily equipment state (deterioration of the lamp, fogging of the jig, etc.). Further, by forming a thin-film temperature measuring element on a part of the product wafer, a dummy for the device QC is specially prepared, and an increase in cost due to disposability can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a thermocouple embedding position.

FIG. 2 is a diagram showing a measurement example of a wafer temperature in-plane distribution (5 points) using a thermocouple embedded wafer manufactured by Sensarray.

FIG. 3 is an explanatory diagram of the first embodiment.

FIG. 4 is a sectional view and a plan view of a thermocouple used in the first embodiment.

FIG. 5 is a diagram for explaining a method of forming the thermocouple shown in the first embodiment.

FIG. 6 is a diagram showing an example in which one of the thermocouples is a metal film in the first embodiment.

FIG. 7 is a diagram showing an example in which a TEG unit incorporating a thermocouple is provided on a product wafer.

FIG. 8 is a plan view of a temperature measuring element used in the second embodiment.

[Explanation of symbols]

10 semiconductor wafer, 11 thermocouple for measuring a temperature profile at point L, 12 thermocouple for measuring a temperature profile at point T, 13 thermocouple for measuring a temperature profile at point C,
14 thermocouple for measuring the temperature profile at point B, 15 thermocouple for measuring the temperature profile at point R, 21 temperature profile at point L in FIG. 1, 22 temperature at point T in FIG. Profile, 23: Temperature profile at point C in FIG. 1, 24: Temperature profile at point B in FIG. 1, 2
5: temperature profile at point R in FIG. 1; 26: profile of temperature difference between point L and point C in FIG. 1; 27: profile of temperature difference between point T and point C in FIG. 1; 28: point B in FIG. Profile of temperature difference between point C and point C, 29: Profile of temperature difference between point R and point C in FIG. 1, 31 element of thermocouple, 32 pad part for extracting signal from thermocouple, 40 bottom Ground film, 41: metal film A, 42: metal film B, 43: interlayer insulating film, 44: interlayer insulating film between metal films A, B, 51: resist, 52: contact hole,
53: Protective film, 71: TEG part incorporating thermocouple, 7
2: Product device, 81: Thin film for measuring temperature from electric resistance value.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisayuki Kato 5-2-1, Josuihonmachi, Kodaira-shi, Tokyo F-term in Hitachi Semiconductor Group 2F056 WA01 4M106 AA01 AA07 AB12 AD01 BA14 CA70 DH15

Claims (6)

[Claims] 1. A semiconductor wafer comprising a thin film thermocouple and a signal extraction pad on a part or the entire surface of the semiconductor wafer. 2. A semiconductor wafer comprising a thin film-shaped temperature measuring element for measuring temperature by a change in electric resistance and a signal extraction pad on a part or the whole surface of the semiconductor wafer. 3. A semiconductor wafer comprising a thin-film thermocouple on a part or the entire surface of a semiconductor wafer, and a signal extraction pad at an end of the wafer. 4. A semiconductor wafer comprising: a thin film-shaped temperature measuring element for measuring a temperature by electric resistance change on a part or the whole surface of a semiconductor wafer; and a signal extraction pad at an end of the wafer. 5. The semiconductor wafer according to claim 1, wherein the semiconductor wafer is a device QC or a TEG wafer for product development. 6. A semiconductor wafer, wherein the semiconductor wafer is a wafer for manufacturing a product device, and a part of the device is replaced by the thin-film temperature measuring element according to claim 1.