JPH081885B2 - Method of measuring pattern shift during epitaxial growth - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring pattern shift during epitaxial growth on a semiconductor substrate, and more particularly to a method for non-destructive measurement.

(Prior Art) It has been conventionally known that pattern shift occurs during epitaxial growth on a semiconductor substrate, and a finished state of a diffusion process of a bipolar integrated circuit, that is, a buried layer formed in a lower layer portion of the epitaxial layer. In order to confirm the relative position between the diffusion layer formed on the surface of the epitaxial layer and the diffusion layer, the position of the diffusion layer was examined by observing the cross section of the semiconductor substrate. However, cutting the semiconductor substrate in accordance with the location of the diffusion layer is an extremely difficult work, and requires a skilled worker. The reason why such a difficulty is imposed is that the boundary line of the diffusion region in the lower layer of the epitaxial layer cannot be confirmed by observation from the surface, and it is due to the effect of the step generated when the diffusion region in the lower layer is formed. This is because the step appearing on the surface of the epitaxial layer causes a pattern shift, and therefore the accuracy of the measurement is aimed at.

The conventional pattern shift measuring method will be described below.

When an N-type buried layer is formed on a P-type substrate and N-type epitaxial growth is performed thereon, first, the substrate is cut into a size of about 5 mm square and the cut surface is angle-polished.

After that, by performing a stain etch with hydrofluoric acid,
Only the P-type layer on the polished surface appears black. Then, the pattern shift is measured by measuring the deviation between the position of the embedded layer appearing on the polished surface and the position of the pattern on the substrate surface.

(Problems to be Solved by the Invention) However, in the above-described conventional measurement method, the semiconductor substrate must be destroyed, and in particular, when the epitaxial layer is thick, a slight angle deviation during measurement causes a large measurement error. It had a problem that it was linked to an error.

The present invention solves the above conventional problems, and an object of the present invention is to provide a pattern shift measuring method during epitaxial growth, which can measure the pattern shift with high accuracy regardless of the thickness of the epitaxial layer without breaking the substrate. And

(Means for Solving the Problems) In order to achieve this object, the method of measuring the pattern shift during epitaxial growth of the present invention uses a mask having first and second mask patterns, The step of forming first and second step patterns corresponding to the first and second mask patterns, and the step of growing an epitaxial layer on the semiconductor substrate on which the first and second step patterns are formed, Of epitaxial growth on the second step pattern without performing epitaxial growth on the step pattern, and applying a resist on the semiconductor substrate on which the epitaxial layer has been grown, and using the mask to perform the first step The first mask pattern and the first mask pattern are matched, exposed and developed to form first and second resist patterns. And a step of measuring the deviation between the third resist pattern and the second resist pattern, which appear on the epitaxial layer due to the step of the second step pattern.

(Operation) The third step pattern on the epitaxial layer, which appears due to the step of the second step pattern, appears off the position right above the second step pattern due to the pattern shift during the epitaxial growth. On the other hand, a second resist pattern formed by aligning the first step pattern with the first mask pattern using a mask having a step pattern formed, and exposing and developing the layer is directly above the second step pattern. is there.
Therefore, the pattern shift can be measured by measuring the deviation between the third step pattern and the second resist pattern.

As a result, highly accurate measurement can be performed even when the epitaxial layer is thick without breaking the substrate.

(Example) Hereinafter, one example of the present invention will be described with reference to the drawings.

FIGS. 1 (a) and 1 (b) show a boundary between an epitaxially grown portion of a portion to be measured, an epitaxially grown portion of a silicon semiconductor substrate coated with a resist, exposed and developed, and a non-epitaxial portion.

1 (a) is a plan view, and FIG. 1 (b) is a sectional view taken along the alternate long and short dash line in FIG. 1 (a).

In FIG. 1, reference numeral 1 is a P-type silicon semiconductor substrate (hereinafter simply referred to as a silicon semiconductor substrate), 2 is an N ⁻ type epitaxial layer (hereinafter simply referred to as an epitaxial layer), and 3 and 3 ′ are first and second positive resists. Resist patterns 4, 4'are first and second step patterns 4 produced when the buried layer is diffused, and 5 are second step patterns 4 when epitaxially grown on the second step pattern 4 '. The third step appearing on the epitaxial layer 2 due to the step
It is a step pattern.

FIG. 2 shows a method of charging the silicon semiconductor substrate 1 to the susceptor 6 of the barrel type low pressure epitaxial device for performing partial epitaxial growth on the silicon semiconductor substrate 1.

A detailed description will be given below with reference to the above figures. First, as shown in FIG. 1, using a mask for forming a buried layer having first and second mask patterns, a first step pattern 4 and a second step pattern of the corresponding buried layer are used. 4'is formed on the silicon semiconductor substrate 1. Then the second
As shown in the figure, the silicon semiconductor substrate 1 is charged in the susceptor 6 of the barrel type low pressure epitaxial device. The dummy substrate 7 is charged in the region where the first step pattern 4 of the buried layer is further formed thereon.

As the dummy substrate 7, one obtained by cutting a silicon semiconductor substrate in half and then oxidizing it to have an oxide film with a thickness of 5000 Å was used.

After charging in this manner, SiCl ₂ H ₂ was used as a source gas and AsH ₃ was used as a dopant gas at 80 Torr and 1080 ° C.
When a 13 μm-thickness is epitaxially grown using, the portion of the silicon semiconductor substrate 1 covered by the dummy substrate 7 does not grow epitaxially. Therefore, as shown in FIG. You can

Next, a positive type resist is applied onto the silicon semiconductor substrate 1, and the first step pattern of the buried layer and the mask of the mask which are not epitaxially grown are formed by using the mask used for forming the N ⁺ type buried layer. The mask pattern of No. 1 is matched (positioned), and exposed and developed.

In the case of this example, since the negative type resist was used at the time of forming the N ⁺ type buried layer, when the same mask was used,
The first resist pattern 3 of the positive type resist remains on the first step pattern 4 of the N ⁺ type buried layer. At this time, the second resist pattern 3'of the positive type resist remains on the epitaxial layer 2 as well, and this is the second resist pattern 3'before the epitaxial growth.
Is formed on the surface of the epitaxial layer 2 directly above the step pattern 4 '. On the other hand, on the epitaxial layer 2, a second
The third step pattern 5 based on the step of the step pattern 4'is shown. Therefore, the positional relationship between the third step pattern 5 on the surface of the epitaxial layer 2 and the second resist pattern 3'is measured.

As described above, according to the present embodiment, the epitaxial layer 2 is grown on a part of the silicon semiconductor substrate 1, and the second resist pattern 3'formed immediately above the second step pattern on the epitaxial layer is formed. By measuring the deviation from the third step pattern 5 which appears due to the epitaxial growth, it is possible to accurately measure the pattern shift during the epitaxial growth without destroying the silicon semiconductor substrate 1.

In this embodiment, the barrel type epitaxial device is used, but the device may be of another type. Further, although the oxidized silicon substrate is used as the dummy substrate, any other one may be used as long as it can withstand the epitaxial reaction conditions and does not affect the reaction. The resist is not limited to the positive type and may be any type.

Although the N ⁺ type buried layer forming mask is used at the time of forming the resist pattern, this may also be a reference for the positional deviation, and thus another mask may be used.

(Effects of the Invention) As described above, according to the present invention, a pattern-shifted step pattern that appears on the surface of an epitaxial layer based on a step pattern such as a buried layer formed in a lower layer portion of the epitaxial layer, and an epitaxial layer By measuring the deviation from the resist pattern formed directly above the step pattern formed in the lower layer part, it is possible to measure the pattern shift with high accuracy without destroying the substrate, and further, the mask used in the next step. Is used for forming the resist pattern, the measured substrate can be advanced in the normal process.

[Brief description of drawings]

1 (a) and 1 (b) are a plan view and a cross-section of a boundary between an epitaxially grown portion of a P-type silicon semiconductor which is partially epitaxially grown and a positive resist pattern is applied in the present invention, and a non-epitaxial portion. FIG. 2 is a diagram showing a method of charging a susceptor of a barrel type reduced pressure epitaxial device when partially epitaxially growing in the present invention. 1 ... p-type silicon semiconductor substrate, 2 ... N ^- type epitaxial layer, 3, 3 '... first and second resist patterns,
4, 4 '... First and second step patterns of the buried layer, 5 ...
Third step pattern appearing on the epitaxial layer, 6
...... Susceptor of barrel type low pressure epitaxial device, 7 ...
… Dummy substrate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/66 Z 7514-4M 21/68 F

Claims (1)

[Claims] 1. A step of forming first and second step patterns corresponding to the first and second mask patterns on a semiconductor substrate using a mask having first and second mask patterns, When growing an epitaxial layer on a semiconductor substrate having first and second step patterns, the first
Of epitaxial growth on the second step pattern without epitaxial growth on the step pattern, and applying a resist on the semiconductor substrate on which the epitaxial layer is grown, and using the mask to form the first step A step of aligning a pattern with the first mask pattern, exposing and developing to form first and second resist patterns, and a third step that appears on the epitaxial layer due to a step of the second step pattern. And a step of measuring a shift between the step pattern and the second resist pattern. The method of measuring the pattern shift during epitaxial growth, comprising: