JPS6286725A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable an alignment precision to be inspected without developing an exposed resist film by a method wherein a photoresist film is irradiated via a photo mask with the first light with wavelength sensitizing a sensitive resin and then with the second light hardly sensitizing the sensitive resin to measure the reflected light intensity. CONSTITUTION:When a positive type photoresist film 3 made of sensitive resin is irradiated with light, the irradiated region 5 is subject to photofading due to photochemical reaction to increase the phototransmittance notably. Next this alignment region is irradiated with the light subject to no photochemical reaction with the positive type photoresist film 3 or the other light subject to extremely slow photochemical reaction if there is any reaction of this kind. The distribution of reflected light intensity can be represented as positional functions on the semiconductor substrate as shown in figure. In other words, the reflected light intensity (a) in the region subject to photochemical reaction is higher than that in the region not subject to the same due to the notably increased phototransmittance in the former region. Through such a distribution of reflected light intensity, a pattern can be discriminated if it has been correctly transferred to a specified position or not.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, in particular, a method for measuring the position of an exposed area in a mask alignment/exposure process included in a pattern transfer process to a photosensitive resin layer. The present invention relates to an alignment accuracy inspection method that can be performed non-destructively before developing a photosensitive resin layer.

[Prior Art] The manufacturing process of semiconductor devices includes a process of forming a photosensitive resin layer (photoresist film) having a predetermined pattern on a semiconductor substrate for ion implantation and circuit pattern formation. ing.

Such patterning of the photosensitive resin layer is performed as follows.

First, a photosensitive resin layer is formed all over the semiconductor substrate.

Next, a photomask having a pattern to be transferred is placed on this photosensitive resin layer. At this time, the photomask is aligned with respect to the semiconductor substrate so that the pattern is transferred to a desired position. Next, the photosensitive resin layer is exposed to light by irradiating it with light through this photomask. Finally, the exposed photosensitive resin layer is subjected to an etching process, so-called development, so that only necessary portions of the photosensitive resin layer remain, and the patterning of the photosensitive resin layer is completed.

In the above-described pattern transfer process, if the photosensitive resin layer pattern is not accurately formed at the desired position, the desired semiconductor device cannot be obtained and the yield of the product will decrease. Therefore, an alignment accuracy inspection step is essential to inspect whether the pattern of the photosensitive resin layer is formed at the desired position.

FIGS. 2A and 2B are diagrams for explaining a conventional inspection method. Hereinafter, a conventional inspection method will be explained with reference to FIGS. 2A and 2B.

FIG. 2A is a diagram showing the schematic structure of the semiconductor device after the photosensitive resin layer has been developed. In FIG. 2A, a base 1111 pattern (for example, a monitoring pattern for alignment) having a predetermined pattern is formed on the semiconductor substrate 1, and a resist pattern (photosensitive resin layer pattern) is further formed on the base ITl film pattern 2. 3 is formed.

Now, the case where the photosensitive b411111i used is a positive photoresist film will be explained as an example. In the positive photoresist film, the area irradiated with light is removed by a development process, so the photoresist 113 formed on the base thin film pattern 2 is a non-exposed photosensitive resin layer. A photoresist l is applied to the area including this base WIplA pattern 2 and the patterned photoresist pattern 3 thereon.
! When 3 is irradiated with light that causes almost no photochemical reaction and the reflected light intensity distribution is measured, the reflected light intensity distribution shown in FIG. 28, for example, is obtained. However, here, the intensity of reflected light from the base 1 film pattern 2 is
The case is shown in which the intensity of reflected light from the In the case of a positive photoresist film, the remaining photoresist film 3 is not exposed to light, so its light absorption rate is high, and in that region (between C and C in Figure 2B) the reflected light intensity is lower than the underlying thin film pattern. It is smaller than the intensity of the reflected light from 2.

By measuring the distance between each interval of reflected light intensity from the base thin film pattern 2 (between D-0 and D-c" in FIG. 2B), the distance between the base thin film pattern 2 and the photoresist II 3 thereon is determined. It is possible to determine whether the photoresist film 3 is left at the desired position or not, and it is possible to determine whether the photomask is correctly aligned during exposure of the photoresist film. Accuracy can be checked.

In addition, other methods for determining whether the resist pattern is formed at the desired position include the method of measuring the reflected light intensity described in (a) above, as well as the method of measuring the intensity of reflected light (e.g., above). A method of measuring scattered light from the edges of the resist film 2), a method of irradiating this uneven pattern with an electron beam to generate secondary electrons, and measuring the formed position of the resist film 3 from the secondary electron image. There is.

[Problems to be solved by the invention] In any case, in the conventional inspection method,
In order to measure the relative position of the base thin film pattern and the photoresist film pattern formed thereon, that is, the alignment accuracy, it was necessary to develop the exposed photoresist film to realize the uneven pattern.

Furthermore, this inspection can detect deviations in the relative position (alignment deviation) between the underlying thin film pattern (e.g. flymen l-monitoring pattern for precision inspection) and the photoresist film thereon.
If this is found, it may be necessary to remove all the formed resist pattern and repeat the resist pattern transfer process again.

Therefore, an object of the present invention is to provide a method capable of eliminating the above-mentioned drawbacks and inspecting alignment accuracy without developing an exposed resist film.

[Means for Solving the Problems] This invention provides at least 7 alignment areas (1 resist II) on a photosensitive resin layer formed over the entire surface of a semiconductor substrate.
A bale that is irradiated with a first light having a wavelength that sensitizes a photosensitive resin through a photomask on a head including a region in which a monitoring pattern is formed to measure the alignment t#1 degree. A second light to which the photosensitive resin is hardly exposed is irradiated over the area of the photosensitive resin layer exposed to the first light and the adjacent non-exposed area, and the intensity of the reflected light is measured. .

The first light beam is either exposure light, alignment light having the same wavelength as the exposure light, or alignment light having a wavelength different from the exposure light but having a wavelength that sensitizes the photosensitive resin layer.

The photosensitive resin is preferably a positive photoresist.

[Function] The photosensitive resin has different optical constants between the photosensitive area and the non-photosensitive area. For example, when the photosensitive resin is a positive photoresist, the photosensitive region undergoes photobleaching of the diazonium field, which is a photosensitive group, due to a photochemical reaction.
L/, its light transmittance increases significantly.

Therefore, the intensity of reflected light from the photosensitive area and the non-photosensitive area f*I4t differs greatly. By determining this reflected light intensity distribution as a function of the position on the semiconductor substrate, it becomes possible to measure the position GL of the exposed area without developing the photoresist WA (photosensitive resin layer).

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[A] Reason J3 and FIG. 1B are diagrams for explaining a method of inspecting the degree of alignment, which is an embodiment of the present invention. In FIG. 1A, a predetermined area (
For example, an underlying thin film pattern (for example, alignment area) having a predetermined pattern (for example, alignment area)
1ls 11 monitoring pattern) 2 is formed. Next, a positive type 2 first resist film 3 made of a photosensitive resin is applied so as to cover the semiconductor substrate 1 and the base thin film pattern 2. Next, an area including at least the alignment area is irradiated with exposure light or alignment light 6 through a photomask (not shown) placed on the positive type 2 first resist layer 3. Here, the alignment light is light with the same wavelength as the exposure light or light with a wavelength different from the exposure light but with a wavelength that is sensitive to the photosensitive resin. This is light that is irradiated only to areas (areas where monitoring patterns are formed to inspect whether or not the

Light shines onto a positive photoresist made of photosensitive resin.
When irradiated with light, the irradiated area 5 undergoes a photochemical reaction and photobleaching (phOtO-1),
The light) 1"i rate increases significantly. Next, this alignment region is exposed to light or a photochemical reaction that does not cause a photochemical reaction with the positive photoresist III (photosensitive resin layer) 3. Irradiates with extremely slow light,
When the reflected light intensity is determined as a function of the position on the semiconductor substrate, a reflected light intensity numerator +i (as shown in FIG. 1B as an example) is obtained.

In other words, as can be seen from Figure 1B, the light transmittance increases significantly in the area where the photochemical reaction has occurred (section A-A- in Figure 18), so the intensity of reflected light from that area increases due to the photochemical reaction. It becomes stronger than the IIA region (the region excluding section AA- in FIG. 1B) where no reaction occurs. Normally, the photoresist film is a thin film of about 1 μm, and the intensity from the base 11M pattern 2 is superimposed on the reflected light intensity distribution. However, the reflected light intensity in the region of the base thin film pattern 2 covered by the non-photosensitive photoresist film 3 (sections B-A, A''-81 in FIG. 1B is smaller than that in the photosensitive region A-A'). From this reflected light intensity distribution, the length of section B-A is W+, section A −-8
-Length W2 is determined, and from the value of (W, -W2), the relative position between the photosensitive area 5 and the base 1 film pattern 2 can be determined, and it is possible to determine whether or not the pattern has been accurately transferred to the desired position. can be determined. That is, alignment accuracy can be checked without using the photoresist film.

In the above example, the case where a positive type photoresist film was used was explained, but the light transmittance of a negative photoresist film is also different between the photosensitive area and the non-photosensitive area. Similar effects can be obtained if they have different properties.

Furthermore, in the above embodiment, the alignment area provided for the photomask alignment inspection is used to perform the photomask alignment inspection.
A similar effect can be obtained by using other regions having specific base patterns.

[Effects of the Invention] As described above, according to the present invention, in the mask alignment/exposure process during resist pattern formation, the photosensitive area of the photoresist (photosensitive resin) film and the non-photosensitive area adjacent to this photosensitive area are separated. Since the alignment accuracy is measured by measuring the intensity distribution of the reflected light from the Can be inspected.

Furthermore, if the alignment accuracy is inspected by irradiating only the alignment region with exposure light or alignment light, the degree of alignment t-li can be inspected without exposing the circuit pattern portion on the semiconductor substrate.

[Brief explanation of drawings]

1A and 1B are diagrams for explaining an alignment accuracy inspection method that is an embodiment of the present invention, and FIG. 1A shows a photosensitive resin layer (photoresist film) eroded by exposure light or alignment light. FIG. 1B is a diagram showing the reflected light intensity distribution obtained from the photosensitive resin layer (photoresist film) of FIG. 1A. FIGS. 2A and 2B are diagrams for explaining a conventional alignment accuracy inspection method, and FIG. 2A shows a photosensitive resin layer (photoresist II).
FIG. 2B is a diagram showing the state of development erosion in I), and FIG.
FIG. 3 is a diagram showing an example of the reflected light intensity distribution obtained from the base i1 film pattern and the photosensitive resin layer (photoresist film) shown in the figure. In the figure, 1 is a semiconductor substrate, 2 is a base III film pattern, 3 is a non-photosensitive photosensitive resin layer (photoresist film),
5 is a photosensitive resin layer (photoresist film) exposed to light. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (5)

[Claims] (1) Forming a photosensitive resin layer over the entire surface of the semiconductor substrate including a base thin film pattern having a predetermined pattern, and applying at least the thin film pattern through a mask having a pattern to be transferred to the photosensitive resin layer. a step of irradiating a region containing light to cause a photochemical reaction in the light-irradiated portion of the photosensitive resin layer; A method for manufacturing a semiconductor device, comprising the steps of: emitting light and measuring the intensity distribution of the reflected light as a function of position on the semiconductor substrate. (2) The underlying thin film pattern is a monitoring pattern formed in an alignment area provided to determine whether the pattern to be transferred has been accurately transferred to a predetermined position. A method for manufacturing a semiconductor device according to item 1. (3) The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the light that causes the photochemical reaction in the photosensitive resin layer is irradiated only to the region where the base thin film pattern is formed. . (4) The mask has a pattern in which at least a part of the photosensitive resin layer on the base thin film pattern is irradiated with light, and the step of measuring the reflected light intensity as a function of the position includes the step of measuring the reflected light intensity as a function of the position of the base thin film pattern. A region where a photochemical reaction has occurred on the base thin film pattern and the base thin film pattern, based on a reflected light intensity distribution from the pattern and a reflected light intensity distribution from the photosensitive resin layer on the base thin film pattern where the photochemical reaction has occurred. Claim 1, which measures the relative position with respect to
3. A method for manufacturing a semiconductor device according to any one of items 1 to 3. (5) The method for manufacturing a semiconductor device according to any one of claims 1 to 4, wherein the photosensitive resin layer is a positive resist layer that undergoes photobleaching due to a photochemical reaction.