Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified configuration
Reexamination Certificate
2001-02-15
2002-08-13
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified configuration
Reexamination Certificate
active
06433437
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing process for a semiconductor device by means of which improvements are achieved on accuracy and uniformity of a size of a transferred pattern in a pattern transfer step of the manufacturing process for a semiconductor device by suppressing optical distortion of an exposure apparatus, a photomask and a manufacturing apparatus for a semiconductor device.
2. Description of the Background Art
In an exposure apparatus used in manufacturing a semiconductor device, light radiated from a light source is transmitted through patterns on a photomask to be projected on a wafer surface to make an image. In
FIGS. 28 and 29
, shown are prior art photomasks formed by means of a prior art method. In
FIG. 28
, arranged are rectangular patterns
113
a
of the same shape having a side a in length in a uniform distribution on a photomask
103
. Furthermore, in
FIG. 29
, formed is a single pattern
113
b
having a constant width L along a bending shape in photomask
103
. A photoactive positive or negative photo resist is applied on a semiconductor wafer in advance. When apositive photoresist is employed, a part of the photoresist on which light through a photomask is irradiated is removed in a following developing step, while a non-irradiated part of the photoresist on which the light doesn't irradiate remains in the following developing step. With such a process adopted, a pattern on the photomask is transferred on the wafer as a pattern of photo resist. By using the pattern of the photoresist, etching and impurity implantation are performed to manufacture a semiconductor device.
A photomask is manufactured such that as shown in
FIG. 28
, patterns of the same size are arranged in a repeated arrangement (periodical arrangement) and the same patterns are distributed in a uniform manner with respect to a size in each of regions all over the surface of the mask regardless of locality of a region to increase uniformity in terms of size of devices. Moreover, there is also included a step in which a non-repeated pattern (non-periodical pattern) as shown in
FIG. 29
is transferred. The pattern with no repetition is also transferred by means of a transfer apparatus such that no variation in size occurs. Hence, each optical systems such as lenses of exposure apparatuses are designed and manufactured such that a pattern is transferred with uniformity.
Distortion in an optical system of an exposure apparatus is, however, difficult to be perfectly eliminated and in addition, characteristics of the distortion are different in each exposure apparatus. For this reason, a pattern on a photomask is not necessarily transferred in a faithful manner. As a result, a transferred resist pattern is affected by optical distortion specific to each exposure apparatus, resulting in a variation in performance of a semiconductor device.
In order to solve such a problem, a proposal has been made on a photomask to correct optical distortion in an exposure apparatus (see Japanese Patent Laying-Open No. 60-167328 and Japanese Patent Laying-Open No. 8-95229). By use of such a photomask corrected with respect to optical distortion, a variation in performance of a semiconductor device is alleviated. Correction methods for optical distortion disclosed in the above described publications are, however, to correct positional displacements of points on a photomask, wherein objects for the correction are a direction of a displacement and a distance thereof. Therefore, there has remained a problem in that the correction of optical distortion is complex and that no recognizable improvement can be achieved without the correction with very high accuracy. Since in a manufacturing process of a semiconductor device, a tremendous number of photomasks are employed, even only photomasks used in manufacturing steps which affect characteristics of the semiconductor device are difficult to be corrected in advance when depending on too complex a correction method. Hence, in company with progress in microfabrication of a semiconductor device, there has been built up a demand for a manufacturing process for a semiconductor device capable of obtaining an exposure-transferred pattern with high accuracy in a simple and convenient manner.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a manufacturing process for a semiconductor device capable of correcting optical distortion of an exposure apparatus in simple and convenient manner, a mask for use in the manufacturing process, and a manufacturing apparatus provided with the mask for a semiconductor device.
A manufacturing process for a semiconductor device of the present invention is a manufacturing process for a semiconductor device including a step of transferring a pattern on a photomask onto a semiconductor wafer by means of an exposure apparatus. The manufacturing process regards optical distortion of an exposure apparatus as a variation in reduction rate of a transferred pattern in each of regions of a photomask and includes: a first step of transferring a fundamental pattern formed on a reference photomask for measuring the optical distortion to measure a size of the transferred pattern in a corresponding one of regions; and a second step of, based on a result obtained in the first step, forming a corrected photomask having a pattern corrected in the corresponding one of regions with respect to the optical distortion.
According to such a constitution, an optical distortion can be obtained as a size of a pattern in each region on a photomask, or a rate of a size of a transferred pattern in a corresponding region and a size of a pattern on the photomask. The size and size rate can be obtained with ease, and furthermore, a corrected photomask can be fabricated based on the size or size rate in a simple and convenient manner. For this reason, a tremendous number of photomasks for use in manufacturing steps to affect characteristics of a semiconductor device can be replaced with respective corrected photomasks in a simple and convenient manner. Consequently, not only can a variation in a transferred pattern in each of exposure apparatuses can be restricted, but a dimensional variation in each of portions in a semiconductor device caused by optical distortion, which differs between exposure apparatuses, can be suppressed, such that sizes of portions in a semiconductor device formed through a different exposure apparatus can be all uniform. As a result, miniaturized semiconductor devices with high reliability can be provided with a high manufacturing yield. Note that optical distortion appears as a variation in a magnification rate or reduction rate in each region; therefore, the above described fundamental patterns are desirably provided across all regions of a reference photomask.
In the manufacturing process for a semiconductor device of the present invention, a fundamental pattern on the reference photomask is, for example, a plurality of unit patterns of the same shape arranged on the reference photomask.
By providing a reference photomask having unit patterns arranged thereon as described above, the area of a photomask is divided into regions including each unit pattern and a magnification rate or reduction rate can be obtained in each region. In a corrected photomask, a pattern size is corrected in each region based on a magnification rate or reduction rate for the region. This correction is performed such that a product of a magnification rate or reduction rate in each region and a pattern size in a corresponding region of a corrected photomask is the same as each other in any of all the regions regardless of particularity of a region. By use of the corrected photomask, when patterns of the same shape are intended to be disposed, for example, in a repeated arrangement (periodical arrangement) in a transferred pattern, the same patterns can be obtained in the respective regions as intended, in the transferred pattern.
In the manufacturing process of a semiconduct
Aoyama Satoshi
Hosono Kunihiro
Hoang Quoc
Nelms David
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