JPH04316347A - Method of measuring film thickness of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method of measuring film thickness for enabling a film thickness to be measured accurately without being affected by a forming material of each film-forming layer to be measured and a film-forming process as well as a film-forming state. CONSTITUTION:When laminating film-forming layers 15 and 19 on a high- concentration N-type diffusion region 13 of a semiconductor substrate 11, remaining patterns 14 and 18 are included on the high-concentration N-type diffusion region 13 and at an interface of the film-forming layers 15 and 19. After film formation ends, the film-forming layers 15 and 19 are eliminated in a section circular arc shape with a constant radius of curvature at a depth reaching the high-concentration N-type diffusion region 13 within the remaining patterns 14 and 18. After that, a position of elimination edge of the remaining patterns 14 and 18 is measured in reference to the elimination edge of the uppermost-layer film-forming layer 19. Then, a film thickness of the film-forming layers 15 and 19 is calculated according to geometrical consideration based on the measurement result and the above constant radius of curvature.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for measuring the film thickness of a semiconductor device, particularly a plurality of film layers formed in a stacked state (for example, a plurality of epitaxial layers stacked on a semiconductor substrate).
The present invention relates to a film thickness measurement method for measuring the film thickness of each of the above.

0002

2. Description of the Related Art Conventionally, as a method for measuring the film thickness of an epitaxial layer formed on a semiconductor substrate of a semiconductor device, for example, there is a method using, for example, an epitaxial film thickness meter. 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.

FIGS. 2(a) to 2(d) show an example of a conventional film thickness measurement method for semiconductor devices, and are process diagrams of a film thickness measurement process performed using an epitaxial film thickness meter that applies infrared rays. be.

A conventional method for measuring film thickness will be explained below with reference to FIG.

First, in the step shown in FIG. 2A, a liquid doped with N-type impurities, for example, is applied to the entire surface of a semiconductor substrate 1 made of, for example, P-type single crystal silicon, and antimony silica is added to form a buried layer. A film 2 is formed.

In the next step, as shown in FIG. 2(b),
A heat treatment is performed on the semiconductor substrate 1 including the antimony silica film 2 to diffuse the antimony silica film 2 into the semiconductor substrate 1 and form a high concentration N-type diffusion region 3 near the surface thereof.

In the step shown in FIG. 2(c), first, an N-type epitaxial layer 4 is grown on the heavily doped N-type diffusion region 3 formed in the previous step. Here, the concentration difference between the highly doped N-type diffusion region 3 and the N-type epitaxial layer 4 is usually, for example, 1×10
The difference in concentration is about 3 cm-2.

Next, although not shown, the N-type epitaxial layer 4 is measured using an epitaxial film thickness meter that uses infrared rays.
Measure the film thickness. The measurement principle of this film thickness meter is to measure the film thickness by detecting the phase difference between an incident wave and a reflected wave of infrared rays incident on the film thickness to be measured. For example, as shown in FIG. 2(c), when an input wave of infrared rays L1 enters the surface of the semiconductor substrate 1, since there is a concentration difference at the interface between the high concentration N type diffusion region 3 and the N type epitaxial layer 4, The input wave is reflected at the surface of the high concentration N type diffusion region 3 at the interface, that is, at the bottom of the N type epitaxial layer 4. Therefore, if the phase difference between the input wave of the infrared ray L1 and the reflected wave from the bottom of the N-type epitaxial layer 4 is detected, the film thickness d1 of the N-type epitaxial layer 4 can be determined.
can be measured.

Using a similar measurement method, as shown in FIG. 2(d), a P-type epitaxial layer 5 is formed on an N-type epitaxial layer 4, and then the thickness of the P-type epitaxial layer 5 is measured. can. First, an N-type epitaxial layer d
Suppose that 1 is obtained. Then, infrared rays L2 are incident on the semiconductor substrate 1 after the P-type epitaxial layer 5 has been formed. Then, the infrared ray L2 is transmitted to the high concentration N type diffusion region 3 and the N type epitaxial layer 4 in the same way as the infrared ray L1.
Since there is a concentration difference at the interface with the N-type epitaxial layer 4, it is reflected at the bottom of the N-type epitaxial layer 4. Therefore, the input wave of infrared ray L2 and N
By detecting the phase difference with the reflected wave from the bottom of the N-type epitaxial layer 4, the total film thickness d2 of the laminated N-type epitaxial layer 4 and P-type epitaxial layer 5 can be measured. Therefore, by subtracting the previously obtained thickness d2 of the N-type epitaxial layer 4 from the measurement result d2, the thickness d3 (=d2-d1) of the P-type epitaxial layer 5 can be determined.

0010

[Problems to be Solved by the Invention] However, the conventional method for measuring film thickness of semiconductor devices has the following problems.

(A) In the conventional film thickness measurement method using infrared rays, measurement is performed by utilizing the reflection of infrared rays due to the difference in concentration between layers. For example, in FIG. 2, the high concentration N-type diffusion region 3 is used as its reflective surface. However, for example, N
If there is a concentration difference between the P-type epitaxial layer 4 and the P-type epitaxial layer 5, there is a possibility that, for example, the incident infrared ray L2 may be reflected at the interface between the epitaxial layers 4 and 5. In this case, it is not clear whether the infrared rays L2 are reflected at the high concentration N-type diffusion region 3 under the N-type epitaxial layer 4 or at the interface between the N-type epitaxial layer 4 and the P-type epitaxial layer 5. As a result, accurate film thickness measurements cannot be performed.

(B) For example, if the conventional film thickness measurement method is
If it is used to measure the thickness of a film formed specifically for measurement, it is possible to grow the N-type epitaxial layer 4 and the P-type epitaxial layer 5 on separate substrates and measure the thickness of each layer. Often, the problem described in (A) above does not occur. However, in this case, for example, two monitor boards are required. Furthermore, when measurements are performed on separate substrates, for example, when an N-type epitaxial layer 4 and a P-type epitaxial layer 5 are grown consecutively, it is possible to determine how much of the high-concentration N-type diffusion region 3 is in total N-type after the epitaxial growth of both layers. It is not possible to check whether the light has diffused upward into the epitaxial layer 4, and it is not possible to correct the value of the total film thickness d3 that is deviated due to the upward diffusion. Therefore,
It is not possible to accurately examine the thickness of the P-type epitaxial layer 5 during continuous growth. This problem also occurs when laminated epitaxial layers are successively grown on the same substrate.

(C) When there is a concentration difference between the N-type epitaxial layer 4 and the P-type epitaxial layer 5, the interface between the N-type epitaxial layer 4 and the P-type epitaxial layer 5 moves due to solid phase diffusion during epitaxial growth. However, it is not possible to accurately measure the thickness of each film. Furthermore,
When epitaxial layers of the same conductivity type are laminated with different concentrations, it is theoretically difficult to measure using the infrared method.

[0014] The present invention solves the problem that the prior art had, for example, when measuring the film thickness by utilizing the concentration difference at a specific interface, such as by using an infrared method. Accurate film thickness measurements cannot be performed if there are reflection factors such as concentration differences in The present invention provides a method for measuring film thickness of a semiconductor device that solves the problem that film thickness fluctuates and accurate film thickness measurement cannot be performed.

[0015]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a method for forming a plurality of film layers constituting a semiconductor device in a laminated state on a substrate of the semiconductor device. After depositing a measurement pattern arranged in a direction and having a predetermined shape and thickness on the substrate and between each of the film formation layers, and depositing the film formation layers in a stacked state, In each of the measurement patterns, each of the deposited layers is removed in an arc-shaped cross section with a constant curvature at a depth that reaches the substrate, and the removal end of the arc-shaped portion of the top deposited layer is referenced. Then, the position of the removal end of the arcuate portion is measured for each of the measurement patterns on the substrate and between each of the deposited layers, and the thickness of each deposited layer is determined based on the measurement result and the constant curvature. This is what I asked for.

[0016]

[Operation] According to the present invention, since the method for measuring the film thickness of a semiconductor device is configured as described above, when a plurality of film layers constituting the semiconductor device are formed in a stacked state on the substrate of the semiconductor device, Then, one or more measurement patterns having a predetermined shape and thickness are interposed on the substrate and between each of the film formation layers, and the film formation layers are deposited in a stacked state. At this time, if each of the one or more measurement patterns interposed on the substrate and between each deposited layer is one measurement pattern,
In the case of a plurality of measurement patterns, each of the plurality of measurement patterns is arranged in the same lamination direction corresponding to each other on the substrate and between each of the film formation layers, that is, in substantially the same lamination area, and in the case of a plurality of measurement patterns, each of the plurality of measurement patterns is The same lamination method is used on the substrate and each of the film formation layers, that is, they are arranged in substantially the same lamination area. Here, the shape and position of each measurement pattern are determined so that the arc portion passes through each measurement pattern, taking into consideration later removal of the arc-shaped cross section. Further, for example, settings are made such that the size of the lower layer is made smaller depending on the measurement conditions and the like. The thickness of each measurement pattern may be the same or different. For example, consider the thickness of the deposited layer formed on each measurement pattern, or consider the material and type of deposition of each deposition layer on the measurement pattern and on the parts other than the measurement pattern. Process (e.g. growth rate in measurement of laminated epitaxial layers)
In order to ensure that the thickness of the measurement pattern does not cause an error in the thickness measurement of the deposited layer, that the measurement pattern is not damaged during deposition, and to confirm the removal edge afterward. Set the appropriate thickness so that it can be done accurately.

Next, within the measurement pattern on the substrate and between each of the film-formed layers, each of the film-formed layers is removed in an arcuate cross-sectional shape with a constant curvature to a depth that reaches the substrate. For example, when there is one measurement pattern, each measurement pattern arranged in the same stacking direction is removed so that each measurement pattern has an arcuate cross section inside. Further, when the number of measurement patterns is two, for example,
As a result of this removal, the corresponding two patterns of each measurement pattern arranged in the same stacking direction are removed on one side and the other side of the arc portion, respectively.

Thereafter, with reference to the removed end of the arcuate portion in the uppermost deposited layer, the removal end of the arcuate portion is determined for each of the measurement patterns on the substrate and between each of the deposited layers. The position is measured, and the thickness of each of the deposited layers is determined based on the measurement result and the constant curvature.

[0019] Therefore, the above problem can be solved.

[0020]

[Embodiment] FIG. 1 is a diagram for explaining a method for measuring film thickness of a semiconductor device according to a first embodiment of the present invention, and is a process diagram of a forming process of a film layer whose film thickness is to be measured and a measurement pattern. It is.

Hereinafter, with reference to FIG. 1, the formation of a plurality of film layers to be measured in this example, for example, the first layer is N-type single crystal silicon and the second layer is P-type single crystal silicon. The formation of the laminated epitaxial layer and the formation of a residual pattern made of an oxide film provided as a measurement pattern will be explained.

First, as shown in FIG. 1(a), for example, P
For forming a buried layer, a liquid added with, for example, an N-type impurity is applied to the entire surface of a semiconductor substrate 11 made of single-crystal silicon to form, for example, an antimony silica film 12.

Next, as shown in FIG. 1B, heat treatment is performed on the semiconductor substrate 11 including the antimony silica film 12, and a sheet resistance of, for example, 30 Ω/□ and a junction depth of about 4 μm is formed near the surface of the semiconductor substrate 11. A high concentration N-type diffusion region 13 is formed.

Thereafter, as shown in FIG. 1C, an oxide film of, for example, about 1000 Å is formed on the heavily doped N-type diffusion region 13 by a known thermal oxidation technique, and the oxide film is removed by a known photolithographic etching technique. The film is patterned to selectively form the remaining pattern 14. The remaining patterns 14 here are configured so that, for example, two patterns are set as one set to perform film thickness measurement at one location.When film thickness measurement is performed at multiple locations, multiple sets of patterns are used. prepare.

Next, as shown in FIG. 1D, a first deposited layer 15 is formed on the heavily doped N-type diffusion region 13 including the remaining pattern 14 by epitaxial growth. Here, the first film formation layer 15 is formed of an N-type epitaxial layer 16 having a thickness of, for example, 2Ω·cm and a thickness of about 5 μm on the high concentration N-type diffusion region 13 other than on the remaining pattern 14.
On the remaining pattern 14, a polycrystalline silicon layer 17 is formed which is grown at approximately the same rate as the N-type epitaxial layer 16, taking into account the thickness of the remaining pattern 14.

At this time, the thickness of the epitaxial layer 16 is
As in the conventional example, it is possible to measure using, for example, an epitaxial film thickness meter that uses infrared rays (not shown).

In FIG. 1E, an oxide film of about 500 Å is formed on the previously formed first film layer 15 using a known oxidation technique, and the oxide film is patterned using a known photolithography etching technique. Then, a remaining pattern 18 is formed. The remaining pattern 18 here is to combine two patterns into one.
They are configured as a set, and each pattern of each set is arranged on the same laminated area corresponding to the pattern of each set of remaining patterns 14. In this embodiment, each pattern of the remaining patterns 18 corresponds to the corresponding remaining pattern 1.
4, that is, the polycrystalline silicon layer 17 on the pattern, and a portion thereof remains on the N-type epitaxial layer 16.

In FIG. 1F, a second film formation layer 19 is formed on the N-type epitaxial layer 16 and the remaining pattern 18 by, for example, a known CVD technique. At this time, the second
The film formation layer 19 is formed of a P-type epitaxial layer 20 on the N-type epitaxial layer 16 other than on the remaining pattern 18, and a P-type epitaxial layer 20 is formed on the remaining pattern 18, taking into consideration the film thickness of the remaining pattern 18. It is formed of a polycrystalline silicon layer 21 grown at approximately the same growth rate as 20.

In the manner described above, the first deposited layer 15, the second deposited layer 19, and the remaining patterns 14 and 18 are formed.

Next, for example, two identical lamination regions (directions)
Remaining pattern 1 with a set of two patterns arranged in
4, 18, for example, the rotary polishing method (grooving method)
The process of measuring the thickness of each of the deposited layers 15 and 19, that is, the N-type epitaxial layer 16 and the P-type epitaxial layer 20, will be described with reference to FIGS. 3, 4, and 5.

Note that FIG. 3 is a cross-sectional view showing a partial structure of the semiconductor device shown in FIG. 1(f), and shows the remaining patterns 14 and 18 used for measuring the film thickness at one location. In FIG. 3, the rotary polishing surface is indicated by a chain line. Figure 4 shows
4 is a cross-sectional view showing a state in which a part of a semiconductor device is polished to the rotary polishing surface in FIG. 3 by a rotary polishing device having a disc-shaped rotary polishing body. FIG. FIG. 5 is a cross-sectional view showing the polishing state of the semiconductor device after polishing by the rotary polishing apparatus of FIG.

First, in the semiconductor device shown in FIG. 3 formed by the process shown in FIG. 1, the portion indicated by the dashed line is polished by a disk-shaped rotary polishing body having a radius R of the rotary polishing device 22 shown in FIG. That is, in the semiconductor device of FIG. 3, in each of the remaining patterns 14 and 18, the first film formation layer 15 and the second film formation layer 19 are formed on the surface of the semiconductor substrate 1, that is, on the high concentration N-type diffusion region 13. At the depth reached, it is removed in an arcuate cross-section with radius R. As a result of this removal process, the semiconductor device has a cross-sectional shape as shown in FIG.

Next, as shown in FIG. 5 or 4, each remaining pattern 14 is removed in the shape of an arc in the figure, for example, with reference to the removal end S of the second deposited layer 19 as the uppermost layer. ,18
Distance L to the removal end Pa, Pb, Pc, Pd on the bottom side of
a, Lb, Lc, and Ld are actually measured using, for example, a predetermined length measuring device.

After that, the measurement results La, Lb, Lc, Ld
and the radius R, the thickness of the first film-forming layer 15, that is, the thickness of the N-type epitaxial layer 16, can be calculated from geometric considerations.
1 and the film thickness of the second deposited layer 19, that is, the film thickness D2 of the P-type epitaxial layer 20, can be calculated.

As an example, each measurement value La, Lb, Lc,
By using Ld, the film thicknesses D1 and D2 can be calculated using the following formula (1
) and (2). D1={(La・Lb)/2R}
-D2...(1)
D2=(Lc・Ld)/2R
…(2
) This embodiment has the following advantages.

(a) In the film thickness measurement method of this example,
Leaving patterns 14 and 18 on each epitaxial layer 16 and 2
The first and second film formation layers 15 are interposed at the bottom of each layer at the time of forming 0, and in the patterns 14 and 18 left behind, the first and second film formation layers 15 are formed at a depth reaching at least the high concentration N-type diffusion region 13.
, 19 is removed, and the position of the removed end of each remaining pattern 14, 18 is measured.
The film thickness of No. 9 is calculated based on geometric considerations.

Therefore, the N type epitaxial layer 16 and the P
Even if the interface moves due to the concentration difference in the N-type epitaxial layer 20, the original interface can be maintained due to the remaining patterns 14 and 18. Therefore, the thickness of not only the N-type epitaxial layer 16 but also the P-type epitaxial layer 20 can be changed. Can be measured accurately.

(b) According to the measurement method of this example,
For example, the amount of upward diffusion or the amount of solid phase diffusion during each epitaxial growth can be determined by using a conventional infrared method for measuring film thickness.

(c) Also, remaining patterns 14 and 18
When removing the inside of the film, the arcuate cross section was made into a perfect circle with radius R, so it was possible to perform highly accurate removal using, for example, a rotary polishing device, and as a result, highly accurate film thickness measurement was possible. Become.

(d) For example, even when measuring the thickness of a film formed specifically for measurement, the N-type epitaxial layer 1
6 and P-type epitaxial layer 20 can be measured accurately without growing them on separate substrates, the number of substrates (wafers) to be monitored can be, for example, one, and the wafers can be effectively can be used.

(e) During the removal process of this embodiment, for example, by removing to a depth exceeding the bottom of the high concentration N type diffusion region 13, the position of the removal end at the bottom of the high concentration N type diffusion region 13 is measured. Then, the diffusion depth of the high concentration N type diffusion region 13 of the N type epitaxial layer 16 and the P type epitaxial layer 20 can also be determined by stainless steel etching.

FIG. 6 is a cross-sectional view showing a partial structure of a semiconductor device, for explaining a method for measuring film thickness of a semiconductor device according to a second embodiment of the present invention.

This semiconductor device has almost the same configuration as the semiconductor device of the first embodiment, but instead of the remaining patterns 14 and 18 each consisting of two patterns, only one pattern each is used. Remaining pattern 3 consisting of
1,32 are provided. In addition, the first and second film formation layers 1
5 and 19 are formed by a selective epitaxial growth method that also includes lateral growth.

In this embodiment as well, substantially the same operation and effect as in the first embodiment can be obtained by performing the removal process having an arcuate cross section as shown by the two-dot chain line in FIG. 6, for example.

Note that the present invention is not limited to the illustrated embodiment, and various modifications are possible. Examples of such modifications include the following.

(I) In the above embodiment, the case of laminated epitaxial layers of N type and P type was explained, but this may be laminated epitaxial layers of the same conductivity type, or two
The thickness measurement of not only a layer but also a plurality of layers of three or more layers can be performed in the same manner.

In addition, when measuring the thickness of a laminated epitaxial layer, instead of growing a polysilicon layer on each measurement pattern, the epitaxial growth layer can be grown laterally by appropriately selecting the material of the measurement pattern. When replacing it with a polysilicon layer, consider the growth rate in the horizontal direction and the growth rate in the vertical direction (depth direction), and set the number, shape, arrangement, etc. of each measurement pattern appropriately to avoid measurement errors. do.

(II) In the above embodiment, the object of film thickness measurement was a plurality of deposited layers consisting only of an epitaxial layer, but this also applies to a plurality of deposited layers consisting of an epitaxial layer and other layers including an insulating film, etc. It may be a layer, or it may be a plurality of deposited layers including other layers not including an epitaxial layer.

(III) In the above embodiment, the removal process was carried out using a rotary polishing device having a disk-shaped rotary polishing body, but this is different from the case where a similar removal process was carried out using a rotary polishing device having a spherical rotary polishing body, for example. It is also possible to perform processing.

(IV) The remaining pattern in the above example was an oxide film, which satisfies conditions such as not being damaged during the formation of each film layer and not interfering with the edges to be removed later. The thickness, shape, etc. can be set as appropriate depending on the measurement conditions.

(V) In the above embodiment, the substrate of the semiconductor device is the semiconductor substrate 11, that is, the high concentration N-type diffusion region 13, but for example, another film layer formed on the semiconductor substrate is set as the substrate, The thickness of each film layer formed thereon may be measured.

[0052]

According to the present invention, since the method for measuring the film thickness of a semiconductor device is configured as described above, the position of each removal end of each measurement pattern is measured, and the position of each removal end of each measurement pattern is measured, and based on the measurement result and the constant curvature. , the thickness of each deposited layer can be determined. Therefore, the film thickness can be measured without being affected by the constituent components of each film-forming layer, the film-forming process, the film-forming state, etc. of each film-forming layer, and the desired film thickness can be measured with high accuracy.

Furthermore, in the measuring method of the present invention, since the film thickness is measured using each of the measurement patterns described above, even if the film thickness of other film layers changes due to the film forming process of a specific film layer, Even in such cases, it is possible to accurately measure the initial film thickness between the interfaces, and if other measuring means are used in combination, it is also possible to measure its fluctuation value.

Furthermore, in the measuring method of the present invention, since the curvature of the cross-sectional arc shape is constant when performing the removal, accurate removal processing can be performed using, for example, a rotary polishing method (grooving method), and the results can be improved. Therefore, the accuracy of film thickness measurement can be improved.

[Brief explanation of drawings]

FIG. 1 is for explaining a method for measuring film thickness of a semiconductor device according to a first embodiment of the present invention, and is a process diagram of a process for forming a film formation layer and a measurement pattern whose film thickness is to be measured.

FIG. 2 shows an example of a conventional film thickness measurement method for a semiconductor device, and is a process diagram of a film thickness measurement process performed using an epitaxial film thickness meter that applies infrared rays.

FIG. 3 is a cross-sectional view showing a partial configuration of the semiconductor device of FIG. 1(f).

4 is a cross-sectional view showing a state in which a part of a semiconductor device is polished to the rotary polishing surface in FIG. 3 by a rotary polishing apparatus having a disc-shaped rotary polishing body; FIG.

FIG. 5 is a cross-sectional view showing the polishing state of the semiconductor device after polishing by the rotary polishing apparatus of FIG. 4;

FIG. 6 is a cross-sectional view showing a partial configuration of a semiconductor device, for explaining a method for measuring film thickness of a semiconductor device according to a second embodiment of the present invention.

[Explanation of symbols]

11 Semiconductor substrate 13 High concentration N type diffusion region 14, 18 Remaining pattern 16, 20 Epitaxial layer 17, 21 Polysilicon layer S, Pa~Pd　Removed end

Claims (1)

[Claims] 1. When forming a plurality of film formation layers constituting the semiconductor device in a stacked state on a substrate of a semiconductor device, a measurement pattern having a predetermined shape and thickness arranged in the same stacking direction is placed on the substrate. After each of the film formation layers is deposited in a laminated state with the film formation layers interposed on the substrate and between the film formation layers, within the measurement pattern on the substrate and between the film formation layers, at a depth that reaches the substrate. , each of the deposited layers is removed in a cross-sectional arc shape with a constant curvature, and the measurement pattern is formed on the substrate and between each of the deposited layers, with the removed end of the arc-shaped portion of the uppermost deposited layer as a reference. A method for measuring film thickness of a semiconductor device, characterized in that the position of the removal end of the arcuate portion is measured for each of the above, and the thickness of each of the deposited layers is determined based on the measurement result and the constant curvature.