JP2959109B2 - X-ray mask manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method of manufacturing a mask for X-ray exposure, which reduces fluctuations in pattern position accuracy caused by internal stress of an absorber and reduces the number of steps of an X-ray mask or the yield. It is an object of the present invention to provide a method for improving the quality of a semiconductor device. In forming a pattern of a heavy metal thin film, an X-ray shielding frame and a separation pattern for separating a semiconductor device pattern formation region from other regions are first drawn and formed. The semiconductor device pattern is formed by etching, and then the second drawing / etching is performed in the semiconductor device pattern formation region to form a semiconductor device pattern.

[Industrial applications]

 The present invention relates to an X-ray exposure mask and a manufacturing method.

As VLSIs become more highly integrated, ultra-fine processing is required. Therefore, an exposure method using short-wavelength X-rays has been keenly required in place of conventionally used ultraviolet rays or far ultraviolet rays.
However, in the X-ray exposure method, an X-ray absorber mainly composed of a heavy metal (usually gold, platinum, tungsten, tantalum, or the like is used) having a small X-ray transmittance is thickly deposited,
A thin membrane (usually a nitride film, nitrogen boride, silicon carbide, or the like is used) that supports the X-ray absorber and has a high X-ray transmittance is used.

FIG. 3 is a conceptual diagram showing a conventional X-ray exposure mask. In the figure, 1 is a reinforcing frame made of SiC, 2 is a Si substrate, 3 is S
A membrane 4 made of iC is an X-ray absorber made of Ta.

Although it is a subject that must be achieved at the same time to improve the alignment accuracy in the ultra-miniaturization of the VLSI, the combination of the thick X-ray absorber 4 and the thin membrane 3 increases the internal stress of the X-ray absorber 4 or Due to the change, the positional accuracy of the X-ray absorber often deteriorates. The present invention uses this X
An object is to improve the positional accuracy of a line mask.

[Conventional technology]

In manufacturing the X-ray mask, the X-ray absorber 4 is grown on the X-ray membrane 3 (see FIG. 3) (thickness = 1 to 6 μm) by sputtering or vapor deposition (thickness = 0.5 to 1).
μm), and thereafter, a resist is applied thereon, and a predetermined pattern for a semiconductor device is drawn by a resist mask 5 by an electron beam drawing method or the like, developed, post-baked,
It has been manufactured through etching of heavy metal thin films.

FIG. 5 is a plan view of a conventional X-ray exposure mask, in which a shielding frame 7 made of an X-ray absorber and an element pattern 9 in a semiconductor device pattern region 8 are formed at the same time. The shielding frame 7 is made of an X-ray absorber (Ta or the like) so that the X-ray does not leak out of the semiconductor element pattern region 8, and the X-ray transmitting film is exposed in the element pattern 9.

In the method as described above, in order to improve the final positional accuracy of the X-ray mask, the thickness of the X-ray absorber is made as thin as possible, and the internal stress of the X-ray absorber is controlled as small as possible. There is a demand for making the thickness of the SiC membrane as thick as possible, and for selecting a material having the largest possible Young's modulus of the SiC membrane.

The present inventors have found that i) the X-ray absorber film thickness for ensuring the mask contrast = 0.8 μm, ii) the control of the internal stress of the X-ray absorber (= 0 to 1 × 10 ⁸ dyn / cm ² ), iii) Membrane film thickness = 3 μm, iv) Material with high mass productivity and high yank rate: Silicon carbide (Young's modulus = 4.5 × 10 ¹² dyn / cm ² ) was selected, and an X-ray mask was exposed at an exposure area of 30 mm. A method of controlling the pattern position accuracy to 0.05 μm or less has been studied.

[Problems to be solved by the invention]

However, for example, in order to control the internal stress of the X-ray absorber to a value less than the above value, ion implantation of argon or the like is performed on the Ta thin film being deposited, and the tensile stress is reduced by implanting argon. Means such as selecting a sample whose internal stress satisfies the above numerical value by inspection are required, and the former has resulted in an increase in the number of steps, and the latter has resulted in a decrease in yield.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for reducing variation in pattern position accuracy caused by internal stress of an absorber and reducing the number of steps of an X-ray mask or improving the yield.

In general, the distortion of an object is Here, Δ = strain amount, ε = strain ratio, = initial length, σ = internal stress, E = Young's modulus.

Therefore, to reduce Δ, there is a reduction in internal stress: σ, a decrease in Young's modulus: E, and a decrease in initial length :.

Deterioration of the pattern position accuracy of the conventional X-ray absorber was caused by forming the absorber shielding frame and the pattern for the semiconductor device at once in the pattern formation of the X-ray absorber as described with reference to FIG. . Therefore, in the conventional method, the X-ray absorber frame length is large and the initial length is large, resulting in an increase in distortion.

[Means for solving the problem]

An object of the present invention is to reduce the initial length in a method for manufacturing an X-ray mask comprising a heavy metal thin film having a pattern for forming a semiconductor device and absorbing irradiated X-rays, and an X-ray membrane supporting the heavy metal thin film. Is the gist.

In the first aspect of the present invention, when forming a pattern of a heavy metal thin film, an X-ray shielding frame and a separation pattern for separating a semiconductor device pattern formation region from other regions are formed in advance by first drawing / etching, Thereafter, a second patterning / etching is performed in the semiconductor device pattern formation region to form a semiconductor device pattern.

A second aspect of the present invention is that, when forming a pattern of a heavy metal thin film, an X-ray shielding frame, a separation pattern for separating a semiconductor device pattern formation region from other regions in advance, and a chip in the semiconductor device pattern formation region And forming a separation pattern of a boundary to be classified as a first pattern by patterning and etching, and then performing a second patterning and etching in a pattern forming region for semiconductor device to form a pattern for semiconductor device. Features.

A third aspect of the present invention is that the second drawing and etching
Is characterized in that a positioning mark for drawing / etching is formed.

[Action]

In the invention according to claim 1, an X-ray shielding frame is provided in advance,
By forming a separation pattern for dividing the semiconductor device pattern formation region from other regions by the first drawing / etching, the strain inside the X-ray absorber is released in advance. After that, by performing the second drawing / etching of the semiconductor element formation region, the initial length of the second etching can be reduced, and the distortion can be reduced.

According to the second aspect of the present invention, when two or more chips (semiconductor devices) are formed, the distortion is further reduced by performing (second) drawing / etching for separating these chips.

According to the third aspect of the present invention, the alignment mark of the second drawing / etching is formed at the time of the first drawing / etching, thereby improving the accuracy of the second drawing / etching.

 Hereinafter, the present invention will be described with reference to examples.

〔Example〕

Example 1 (1) 1000 ° C. on a silicon substrate 2 (plate thickness = 525 μm)
Silicon carbide 3 (plate thickness = 3 μm) is grown by the reduced pressure vapor phase epitaxy.

(2) Tantalum 4 serving as an X-ray absorber is grown on the silicon carbide 3 by 0.8 μm by sputtering.

(3) The above-mentioned tantalum is added to the reinforcing frame 1 made of silicon carbide.
Silicon substrate 2 on which silicon carbide has been grown is attached with an adhesive.

(4) Etching of the silicon substrate is performed by using the reinforcing frame 1 as a mask for the surface of the surface on which tantalum has not been grown.

The surface on which tantalum is not grown is immersed in a solution of hydrofluoric acid and nitric acid to etch the silicon substrate 2 so that the reinforcing frame 1
Except for the silicon substrate from other places.

(5) A photosensitive material: a resist is applied to the surface on which tantalum has been grown, prebaked, and then a line having a width of 20 μm is drawn by an electron beam exposure method. This line separates the semiconductor device pattern section 8 from other areas.
One in which the X-ray absorber is drawn as a shielding frame 7 and one in which the inside of the semiconductor device pattern portion 4 is divided into four chips 1
0 "and 3" (the method of claim 2), which are shown in the same figure. After drawing these 10, 10 'and 10 ", development and post-baking are performed, and then the absorber ( tantalum)
(For example, reactive ion etching) to form grooves 10, 10 ′ and 10 ″. After etching, the resist is stripped.

(6) A photosensitive material: a resist is applied to the surface on which tantalum has been grown and prebaked, and then a predetermined semiconductor device pattern in the semiconductor device pattern portion 8 is drawn and developed by an electron beam exposure method.・ After post baking,
An absorber (tantalum) is etched (for example, a reactive ion etching method). After the etching, the resist is removed.

The etching of 10 ″ may be omitted (the method of claim 1). Second Embodiment (1) to (4) of the first embodiment are performed.

(1) A photosensitive material: a resist is applied to the surface on which tantalum has been grown, prebaked, and thereafter, drawing is performed by an electron beam exposure method. This drawing is performed in (a) an X-ray absorber shielding frame, (b) a boundary portion of the semiconductor device pattern portion, and (c) a region in the semiconductor device putter portion that can be divided as a chip.
20 μm wide line, and (d) alignment mark 12 (second
Figure). After drawing, development and post-baking are performed, and then absorber (tantalum) etching (for example, reactive ion etching) is performed. After the etching, the resist is removed.

(2) A photosensitive material: a resist is applied to the surface on which tantalum has been grown, pre-baked, and then an alignment mark 12 made of an X-ray absorber by an electron beam exposure method.
The semiconductor element formation region 8 in the mask is aligned (preventing displacement) by the reflected electrons and secondary electrons generated from the semiconductor device, and a predetermined semiconductor device pattern in the semiconductor device pattern portion 8 is drawn and developed / developed. After the post-baking, the absorber (tantalum) is etched (for example, a reactive ion etching method). After the etching, the resist is removed.

〔The invention's effect〕

As described above, the length of the X-ray absorber is reduced by cutting the primary rough X-ray absorber, and as a result, the positional distortion due to the internal stress of the X-ray absorber is reduced.

[Brief description of the drawings]

1 is a plan view and a cross-sectional view of an X-ray mask manufactured by the method of the present invention, FIG. 2 is a drawing similar to FIG. 1, FIG. 3 is a conceptual diagram of the X-ray mask, and FIG. FIG. 5 is a conceptual diagram of absorber patterning, and FIG. 5 is a plan view of an X-ray mask manufactured by a conventional method. 1. Reinforcement frame made of SiC, 2 .... Si substrate, 3 .... membrane, 4 .... X-ray absorber, 7 .... X-ray absorber shielding frame,
8 ... pattern formation region for semiconductor device, 10 ... line formed by first drawing / etching

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-159426 (JP, A) JP-A-62-176130 (JP, A) JP-A-2-170410 (JP, A) JP-A-2- 205009 (JP, A) JP-A-4-162414 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (3)

(57) [Claims] 1. A method for manufacturing an X-ray mask comprising a heavy metal thin film having a pattern for forming a semiconductor device and absorbing irradiated X-rays, and an X-ray membrane supporting the heavy metal thin film, comprising: At the time of formation, an X-ray shielding frame and a separation pattern for separating the semiconductor device pattern formation region from other regions are formed in advance by first drawing / etching, and then the second pattern in the semiconductor device pattern formation region is formed. Forming a pattern for a semiconductor device by performing pattern writing and etching. 2. A method for manufacturing an X-ray mask comprising a heavy metal thin film having a pattern for forming a semiconductor device and absorbing irradiated X-rays and an X-ray membrane supporting the heavy metal thin film, comprising: At the time of formation, an X-ray shielding frame, a separation pattern for separating the semiconductor device pattern formation region and other regions in advance, and a separation pattern for a boundary to be separated as a chip in the semiconductor device pattern formation region, 2. The X-ray mask according to claim 1, wherein the first pattern is formed by first drawing and etching, and then the second pattern is formed by performing second drawing and etching in the pattern forming region for the semiconductor device. Manufacturing method. 3. The method for manufacturing an X-ray mask according to claim 1, wherein an alignment mark for the second drawing / etching is formed at the time of the first drawing / etching.