JPH02206146A - Measurement of film thickness of semiconductor device - Google Patents

Abstract

PURPOSE:To measure a film thickness of an epitaxial growth layer highly accurately and easily by a method wherein a pattern for measurement use, a deposition layer and an opening part are formed according to a process and are utilized. CONSTITUTION:A dielectric layer other than a pattern 23 for measurement use is removed; after that, a deposition layer 25 composed of a single-crystal silicon layer to which n-type impurities have been added, i.e. an epitaxial growth layer, is formed on a semiconductor substrate 21; then, the deposition layer 25 on the pattern 23, for measurement use, composed of a silicon oxide film is transformed into a polycrystalline silicon layer 26. Then, the polycrystalline silicon layer 25 is dry-etched; an opening part 27 reaching the pattern 23 for measurement use is formed; in succession, the pattern 23, for measurement use, exposed inside the opening part 27 is etched by using a hydrofluoric-acid-based solution; the opening part 27 reaches the semiconductor substrate 21. After that, a difference in level on the surface is measured by using a contact-type surface difference-in-level meter while this meter is scanned on the deposition layer 25 including the opening part 27, e.g. in a direction of an arrow C. Thereby, a film thickness of the deposition layer can be measured by using a highly accurate and easy means.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring the thickness of a semiconductor device, and particularly to a method of measuring the thickness of an epitaxially grown layer.

(Prior Art) Conventionally, as a technology related to such a field, there is an epitaxial film thickness meter, for example. This film thickness meter uses infrared rays and is widely used because it can measure the thickness of an epitaxially grown layer with good reproducibility.

However, the film thickness meter has a problem in that it cannot measure high concentrations unless an epitaxially grown layer is formed on a high concentration silicon substrate. Furthermore, since this film thickness meter measures from the position upwardly diffused to the epitaxial growth layer side to the surface of the epitaxial growth layer, there was also a problem in that the interface between the original silicon substrate and the epitaxial growth layer could not be accurately measured.

As a film thickness measurement technology that solves the above problems,
There is a measuring method described in Japanese Patent No. 9-17536. This document describes a method for measuring the depth of a P-type diffusion region when a P-type diffusion region is formed in a single-crystal silicon substrate. is possible, and the measurement method will be explained below.

FIGS. 2(a) to 2(e) show a conventional method for measuring the thickness of an epitaxially grown layer using the method described in the above-mentioned document, and FIGS. 2(a) to 2(d) show the manufacturing process of a sample piece, and Same figure (
The method of measuring e) using the sample piece is shown respectively.

In FIGS. 2(a) to 2(d), the figures on the left side each show a front sectional view of the sample piece, and the corresponding figures on the right side are side sectional views showing the cross section taken along line A-A of the front sectional view. be. First, as shown in FIG. 2(a), a dielectric layer 2 made of a silicon oxide film having a thickness of approximately 1000 yen is formed on the entire surface of a semiconductor substrate 1 made of single crystal silicon. Subsequently, as shown in FIG. 2(b), a polycrystalline silicon layer 3 to which no impurities are added is grown on the surface of the dielectric layer 2 by vapor phase growth.

Next, as shown in FIG. 2(C), polycrystalline silicon layer 3 is dry etched to form a plurality of openings 4 in stripes reaching dielectric layer 2. Then, as shown in FIG.

Thereafter, the dielectric layer 2 exposed in the opening 4 is immersed in a diluted acid solution and removed by etching, allowing the opening 4 to reach the semiconductor substrate 1. Thereby, on the semiconductor substrate 1, the exposed surface 5 of the semiconductor substrate 1 and the exposed surface 6 of the polycrystalline silicon layer 3 are present in a stripe shape.

Next, as shown in FIG. 2(d), epitaxial growth is performed on the entire surface of the semiconductor substrate 1. As a result, an epitaxial growth layer 7 is formed on the exposed surface 5 of the semiconductor substrate 1, and a polycrystalline silicon layer 8 is formed on the exposed surface 6 of the polycrystalline silicon layer 3.

In this way, the sample piece 9 for film thickness measurement is manufactured.

Thereafter, the film thickness of the epitaxially grown layer 7 of the sample piece 9 is measured as shown in FIG. 2(e). Figure 2 (
e) shows a side sectional view and a plan view of the sample piece 9.

First, a disk-shaped grindstone 10 with a radius R is arranged so that its rotation axis is perpendicular to the stripes of the epitaxial growth layer 7 and the polycrystalline silicon layer 8, and rotational polishing is performed to form the grooves 1.
form 1. As a result, polished end portions 12a, 12b are formed on the surface of epitaxial growth layer 7, and polished end portions 13a, 13b are formed on the surface of polycrystalline silicon layer 8. Further, each layer is exposed in the groove 11, and the interfaces 14a and 14b between the semiconductor substrate 1 and the epitaxial growth layer 7 and the interfaces 15a and 15b between the semiconductor substrate 1 and the dielectric layer 2 are also exposed.

Here, the polished ends 12a, 12b, 13a, and 13b can be observed, but the interfaces 14a and 14b are not observable because they are interfaces between single crystal silicon. On the other hand, interface 1
5a and 15b, the silicon oxide film forming the dielectric layer 2 has an interference color and can be observed optically. Therefore,
Between the polished end 12a and the interface 15a or between the polished end 12b
and the distance 1 between the interface 15b and the interface 15a and the interface 15b.
Measure the distance m between. The film thickness d of the epitaxial growth layer 7 can be calculated by substituting these distances ρm and the radius R of the grindstone 10 into the following formula %.

Such a measurement method can relatively easily and accurately measure the area from the interfaces 14a and 14b between the semiconductor substrate 1 and the epitaxial growth layer 7 to the surface of the epitaxial growth layer 7.
It is widely used to this day.

(Problem to be Solved by the Invention) However, in the method for measuring the film thickness of a semiconductor device having the above configuration, in the epitaxial growth process of a wafer (hereinafter referred to as the main wafer) that forms an actual device, a sample piece separate from the main wafer is 9 is formed by simultaneous processing. That is,
Since polycrystalline silicon N3 is formed on the dielectric layer 2 of the semiconductor substrate ↑, the sample piece 9 is prepared, and the film thickness is measured after polishing, the following problems occur, which are difficult to solve. Met.

(1) Since the areas on which the epitaxial growth layer 7 is grown are different between this wafer and the sample piece, a so-called loading effect occurs, resulting in a difference in the film thickness of the epitaxial growth layer 7 on both sides. Therefore, there is a possibility that the film thickness measured on the sample piece 9 does not necessarily match the film thickness of the wooden wafer.

(2) When forming the sample piece 9 using a wafer in order to prevent the loading effect, a problem arises in terms of the throughput of the apparatus. That is, since the capacity that can be epitaxially grown at one time is determined by the equipment, the throughput of the wafer is reduced.

(3) Even if the sample piece 9 is not formed on the actual wafer together with the actual device, the sample piece 9 must be cut out from the actual wafer due to polishing etc. when measuring its film thickness, and the actual wafer may become unusable. It will be wasted. Therefore, it is necessary to separately prepare the sample piece 9, and it is also necessary to perform the formation and polishing operations of the striped polycrystalline silicon layer 3, so that a large number of man-hours must be spent on measuring the film thickness.

The present invention addresses the problems that the prior art had, such as the fact that the film thickness measured on a sample piece does not necessarily match the actual film thickness, problems that arise in the performance of processing equipment, and the fact that film thickness measurement requires a great deal of effort. The present invention provides a method for measuring film thickness of a semiconductor device that solves the problem of requiring a lot of man-hours.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a step of forming a dielectric layer of a predetermined pattern including a dielectric pattern for measurement on the surface of a semiconductor substrate, and removing the remaining dielectric layer, growing a deposited layer on exposed surfaces of the semiconductor substrate and the measurement dielectric pattern, and etching the deposited layer on the measurement dielectric pattern. forming an opening that reaches the measurement dielectric pattern and has an opening area smaller than the surface area of the measurement dielectric pattern; etching the measurement dielectric pattern exposed within the opening; A film of a semiconductor device is formed by making the opening reach the semiconductor substrate, measuring the depth of the opening with respect to the surface of the deposited layer using a surface level difference meter, and detecting the thickness of the deposited layer. It is designed to measure thickness.

(Function) According to the present invention, since the method for measuring the film thickness of a semiconductor device is configured as described above, after forming a dielectric pattern for measuring the thickness of a semiconductor substrate, a deposited layer is grown on the dielectric pattern. Forming a film thickness measurement part by forming an opening in a dielectric pattern for measurement and measuring the film thickness measurement part with a surface step meter is a method that can be used to form a striped polycrystalline silicon layer in the conventional measurement method. This eliminates the need for polishing work and makes it possible to form a film thickness measuring section on a wafer for manufacturing semiconductor devices according to the manufacturing process.

Therefore, since the film thickness measurement section can be formed on the wafer under the same conditions as the semiconductor device, highly accurate film thickness measurement is possible.

Further, the film thickness measurement section enables formation on the wafer at a location other than the element formation area, and does not adversely affect the element formation area. Therefore, there is no need to waste the wafer or reduce the throughput of the wafer. Furthermore, it serves to eliminate the need to manufacture a separate sample piece, thereby simplifying film thickness measurement.

Therefore, the above problem can be solved.

(Example) FIGS. 1(a) to 1(f) are process diagrams showing a method for measuring film thickness of a semiconductor device in an example of the present invention.

The case of a bipolar semiconductor device will be described below in accordance with the order of the figures.

First, in FIG. 1(a), a dielectric layer 22 made of a silicon oxide film is formed on the entire surface of a semiconductor substrate 21- made of P-type single crystal silicon. Here, the semiconductor substrate 21 is a main wafer for forming a bipolar type semiconductor device, and for example, the area indicated by B in the figure is a bipolar element forming area. Furthermore, the region indicated by G in the figure is a grid line region outside the bipolar element forming region.

Next, as shown in FIG. 1(b), the dielectric layer 22 is patterned to form a predetermined element formation pattern in the bipolar element formation region B. Then, as shown in FIG. A pattern for film thickness measurement is formed on the mask used at that time, and at the same time as the element formation pattern is formed, a dielectric pattern for measurement (hereinafter simply referred to as a measurement pattern) 23 is placed in the grid line area G.
form.

Subsequently, as shown in FIG. 1C, a liquid doped with n-type impurities is applied onto the exposed surface of the semiconductor substrate 21 to form a buried layer, such as an antimony silica film. Thereafter, this semiconductor substrate 2] is subjected to heat treatment to form an n-type diffusion region 24.

Next, as shown in FIG. 1(d), after removing the dielectric layer 22 other than the measurement pattern 23, a deposited layer 25 made of a single crystal silicon layer doped with n-type impurities, that is, an epitaxially grown layer, is formed on the semiconductor substrate 21. Form. At this time, the deposited layer 25 on the measurement pattern 2B made of a silicon oxide film becomes a polycrystalline silicon layer 26. At this time, irregularities occur near the surface of the polycrystalline silicon layer 26.

Thereafter, as shown in FIG. 1(e), a resist pattern is formed on the polycrystalline silicon layer 26 using a known photolithography technique, and the polycrystalline silicon M26 is dry-etched using the resist as a mask. As a result, an opening 27 reaching the measurement pattern 23 is formed. At this time, the opening area of the opening 27 is set to be smaller than the surface area of the measurement pattern 23, so that the opening 27 falls within the surface area of the measurement pattern 23. continue,
The measurement pattern 23 exposed in the opening 27 is etched using a fluoric acid solution, and the opening 27 is made to reach the semiconductor substrate 21 . Thereafter, the deposited layer 2 including the opening 27 is
5 is scanned, for example, in the direction shown by arrow C, and the surface level difference is measured. As a result, the thickness of the deposited layer 25, that is, the epitaxially grown layer, is measured as described later.

Thereafter, as shown in FIG. 1(f>), necessary processing is performed in accordance with the manufacturing process of a normal bipolar semiconductor device.

At this time, since the opening 27, the measurement pattern 23, etc. are provided in the grid line region G, there is no adverse effect on the manufacturing process of the bipolar semiconductor device.

Next, a method for measuring the thickness of an epitaxially grown layer using the above-mentioned surface step meter will be described in detail with reference to FIG.

FIG. 3 is an output data diagram showing an example of data output from the surface level difference meter.

As mentioned above, for example, the surface level difference meter can be
When scanning in this direction, output data as shown in FIG. 3 is obtained from the surface level difference meter. That is, when the surface of the polycrystalline silicon layer 26 around the opening 27 is scanned, the output data also has irregularities corresponding to the irregularities, but when the surface of the deposited layer 25 of the single crystal silicon layer is scanned, gives flat output data. Therefore, by measuring the depth Hl from the top of the unevenness to the inner bottom surface of the opening 27 and the height H2 from the surface of the deposited layer 25 to the top of the unevenness, it is possible to determine the depth of the deposited layer 25, that is, the epitaxially grown layer, as shown in FIG. Film thickness T
is measured.

゛As described above, in this example, the measurement pattern 23, the deposited layer 25, and the opening 27 are formed on the main wafer for forming the semiconductor device according to the semiconductor device manufacturing process, and these are used to perform epitaxial growth. The thickness T of the layer can be measured.

Therefore, the film thickness T of the epitaxial growth layer corresponding to the semiconductor device actually manufactured can be easily measured with high precision, and the wafer can be used as is for manufacturing the semiconductor device, so there is no waste. In addition, since it is not necessary to manufacture a measurement sample piece separately from the wafer,
The complicated labor involved in preparing sample pieces can be eliminated. Moreover, polishing work and the like as in the conventional method are not required, so that workability can be improved and the number of measurement steps can be significantly reduced.

Furthermore, by using this wafer as it is for film thickness measurement, there is an advantage that the throughput associated with the formation of the epitaxial growth layer is improved.

Note that the present invention is not limited to the illustrated embodiment, and can be modified in various ways, such as the following modifications.

i) Figure 1 shows a method for measuring film thickness in a bipolar semiconductor device;
It is also applicable to OS transistors and the like.

ii) Although the measuring section for film thickness measurement is provided in the grid line region G of the wafer, the present invention is not limited to this, and may be provided anywhere other than the semiconductor element formation region. Furthermore, it is of course possible to fabricate and measure a separate sample piece in a similar manner without intentionally providing it on the main wafer.

iii) Although the deposited layer 25 is an epitaxially grown layer, the measuring method of the present invention can be used to measure the thickness of a layer other than an epitaxially grown layer as long as it has a certain thickness.

iv) The materials of the semiconductor substrate 21, dielectric layer 22, deposited layer 25, etc. shown in the above embodiments are not limited to those illustrated, but the present invention can be applied to other materials as well.

(Effects of the Invention) As described above in detail, according to the present invention, after forming a dielectric pattern for measurement on a semiconductor substrate, a deposited layer is grown, and openings are formed in the deposited layer and the dielectric pattern for measurement. The thickness of the deposited layer is measured by measuring the depth of the opening with respect to the surface of the deposited layer using a surface step meter. It becomes possible to form the semiconductor device on the wafer for manufacturing the semiconductor device according to the manufacturing process.

Therefore, the thickness of the deposited layer corresponding to an actual semiconductor device can be measured with high precision and with easy means, and the wafer used for the measurement is not wasted. Furthermore, since there is no need to manufacture a measurement sample piece separate from the wafer, it is possible to reduce the number of man-hours involved in sample piece manufacture and improve work efficiency, and also to prevent a decline in processing capacity in semiconductor device manufacturing. Can be done. Therefore, reliability related to film thickness measurement,
This has the effect of significantly increasing work efficiency and yield.

[Brief explanation of the drawing]

FIGS. 1(a) to (f> are process diagrams showing a method for measuring film thickness of a semiconductor device in an embodiment of the present invention, and FIGS. 2(a) to (e)
) is a process diagram showing a conventional film thickness measuring method, and FIG. 3 is an output data diagram of a surface level difference meter showing the film thickness measuring method in FIG. 1(e). 21... Semiconductor substrate, 22... Dielectric layer, 23... Dielectric pattern for measurement, 25...
...Deposition layer, 27...Opening.

Claims (1)

[Scope of Claims] A step of forming a dielectric layer of a predetermined pattern including a dielectric pattern for measurement on the surface of a semiconductor substrate, and a step of removing the other dielectric layer while leaving the dielectric pattern for measurement. growing a deposited layer on the exposed surfaces of the semiconductor substrate and the measurement dielectric pattern; etching the deposited layer on the measurement dielectric pattern to reach the measurement dielectric pattern and the measurement dielectric pattern; forming an opening having an opening area smaller than the surface area of the dielectric pattern; etching the measurement dielectric pattern exposed within the opening to cause the opening to reach the semiconductor substrate; A method for measuring film thickness of a semiconductor device, comprising: measuring the depth of the opening with respect to the surface of the deposited layer using a surface step meter, and detecting the thickness of the deposited layer.