JPH03168747A - Photomask - Google Patents

Abstract

PURPOSE:To decrease the influence of a proximity effect and to decrease the memory capacity of an electronic computer as well as to attain the formation of fine patterns with high accuracy by incorporating carbon atoms into the light shielding patterns to be provided on a transparent substrate. CONSTITUTION:The C-contg. light shielding patterns 3 provided on the transparent substrate are the metallic film patterns laminated with three layers; a C- contg. CrOx film 31, a C-contg. Cr film 32 and a C-contg. CrOx film 33. The carbon atoms are incorporated at 3 to 10% into all of these three metallic film layers. The amt. of the secondary electrons is decreased at the time of exposing and nearly the same exposed regions are formed in the regions plotted by an electron beam when the carbon atoms are incorporated into the patterns in such a manner. Thus, the photomask having the faithful and fine patterns having the high accuracy is formed.

Description

[Detailed Description of the Invention] (Summary) With regard to photomasks such as reticles and masks on which patterns are drawn using electron beam exposure, the influence of the proximity effect can be reduced, the storage capacity of electronic computers can be reduced, and high precision can be achieved. The purpose of this method is to form a fine pattern, and a photomask is constructed in which carbon atoms are included in a light-shielding pattern provided on a transparent substrate.

[Industrial application field]

The present invention relates to a photomask, and more particularly to a photomask such as a reticle or mask on which a pattern is drawn using an electron beam exposure method.

Recently, semiconductor devices such as LSIs have become extremely finer, and accordingly, light-shielding patterns provided on photomasks have also become finer. However, it is desirable that such photomasks form patterns with as high precision as possible, as this has a significant impact on the performance and quality of semiconductor devices. [Prior Art] There are two types of photomasks used in photolithography technology in semiconductor device manufacturing methods: reticles and masks. A reticle is a photomask that has a pattern that is 5 to 10 times the size of the pattern to be transferred onto a semiconductor substrate, and this reticle is attached to a reduction projection exposure device (stepper) and is reduced and projected onto the semiconductor substrate. be.

Further, a mask is a mask that is provided with a pattern of the same size as the pattern to be transferred onto a semiconductor substrate, and is exposed in close contact with the semiconductor substrate using an alignment device.

In addition, these reticles and masks have a light-shielding pattern made of a metal film or the like formed on a transparent substrate, and a cross-sectional view of such a conventional photomask is shown in FIG. In the figure, symbol 1 is a quartz glass substrate (transparent substrate), 2 is a light-shielding pattern, and the light-shielding pattern 2 is made of, for example, a chromium oxide (Crux) film 21 (film thickness: 50 mm), chromium (Cr).
It is constructed of a metal film pattern in which three layers are laminated: a film 22 (film*600 layers) and a chromium oxide (Crux) film 23 (thickness 300 layers).

However, with the miniaturization of semiconductor devices, the light-shielding patterns provided on photomasks such as reticles and masks are required to have higher precision. is drawn. However, unlike the light exposure method, the electron beam exposure method allows electrons to be incident, so while it is possible to form fine patterns, it also produces a proximity effect, which is one of the main causes of pattern accuracy deterioration, and the proximity effect must be corrected. There is a need. Proximity effect is a phenomenon in which electron scattering within the resist during exposure and back scattering from the substrate after electron incidence are repeated, and charges are accumulated around the irradiated position, and a pattern is formed according to the accumulation of charges. This results in pattern distortion and deterioration in pattern accuracy. In other words, the periphery is also exposed to light due to the secondary electrons of the irradiated electrons and heat generation, reducing pattern accuracy, and this proximity effect also affects adjacent patterns.

FIG. 4 is a cross-sectional view showing a conventional exposure method for explaining this, in which a Crux film 21, C
A metal film 2 consisting of an r film 22 + a Crux film 23 is deposited by sputtering, and a resist film 5 (thickness: 500 mm) is further applied thereon.
FIG. 3 is a cross-sectional view of a process in which a coating material (0 persons) is applied and an electron beam EB is selectively irradiated from the top surface thereof.

Then, secondary electrons are reflected from the electrons incident on the metal film 2 (indicated by arrows), and the exposure area 52 expands due to the proximity effect due to heat generation due to human radiation of electrons, which is shown in FIG. is illustrated.

Conventionally, as a means for correcting such a proximity effect, the proximity effect of the pattern itself and adjacent patterns has been taken into account in advance, and a dimensional shift amount is added to the exposure data. For example, when exposing to a positive resist, the pattern is drawn smaller than the design pattern, and when exposing to the negative resist, the pattern is drawn larger than the design pattern, and also the adjacent patterns are taken into consideration. A correction amount was given.

[Problem to be solved by the invention]

However, writing while calculating and determining the correction amount for correcting such proximity effect in addition to the exposure data of the design pattern has the disadvantage that the storage capacity of the electronic computer attached to the electron beam exposure apparatus becomes large. Especially when drawing a 5 to 10 times larger pattern like a reticle,
It has the disadvantage that its storage capacity increases further.

The present invention reduces such drawbacks, reduces the influence of the proximity effect, reduces the storage capacity of electronic computers, and proposes a photomask that allows highly accurate fine patterns to be formed.

[Means to solve the problem]

This problem is solved by a photomask in which a light-shielding pattern provided on a transparent substrate contains carbon atoms.

[For production]

That is, in the past, secondary electrons and heat generation were generated due to the light-shielding film (metal film) from which electrons are relatively difficult to dissipate, but the present invention uses a light-shielding film that makes it easier for electrons to dissipate when they enter the light-shielding film. A quartz glass substrate with a light shielding film containing carbon atoms (C) is used, and a photomask is formed by drawing on the light shielding film using an electron beam exposure method.

In this way, electrons can easily escape from the light-shielding film, reducing the proximity effect, and reducing the storage capacity of electronic computers.
A photomask with a highly accurate fine pattern can be obtained.

〔Example〕

Examples will be described in detail below with reference to the drawings.

FIG. 1 shows a cross-sectional view of a photomask according to the present invention, and symbol 1 in the figure is a quartz glass substrate (2 to 3 mm thick).
), 3 is a C-containing light-shielding pattern (C-containing metal film pattern), and the C-containing light-shielding pattern 3 is C-containing Crux.
Film 31 (thickness 50), C-containing Cr film 32 (thickness 600)
human), C-containing Cry. This is a metal film pattern in which three layers of film 33 (thickness: 300 layers) are laminated, and all of these three metal films contain 3 to 10% of carbon atoms. If such carbon atoms are included, the amount of secondary electrons generated during exposure will be reduced, and the exposed area will be approximately the same as the area drawn with the electron beam, resulting in a high precision that is more faithful than before. A photomask with a fine pattern can be used.

To explain the method for incorporating carbon atoms, a sputtering method is used to deposit a Cr film or a Crow film, but argon (argon) is used as the sputtering gas during sputtering.
Carbon dioxide (C○2) gas is used together with Ar) gas. An example of spatter conditions is gas pressure 5mToor,
Ar gas 100cc/min, CO2 gas 15cc/min. Sputtering is performed at a sputtering voltage of 450 V and a sputtering current of about 4.5 A, and chromium or chromium oxide is used for the sputtering substrate.

FIG. 2 is a cross-sectional view showing the exposure method according to the present invention,
C containing carbon atoms on the quartz glass substrate 1
A C-containing metal film 3 consisting of a Crux film 31, a Cr film 32, and a Crux film 33 is deposited by sputtering under the above conditions, and then a resist IIU5 (It! thickness: 5000 mm) is applied from the top surface. Selectively irradiate with electron beam EB. Then, the electrons incident on the C-containing metal film 3 move through the film relatively easily and are dissipated, so the number of secondary electrons decreases, and the amount of heat generated decreases accordingly, reducing the proximity effect. However, a resist pattern that is more faithful to the exposed area 53 of the resist film 5 than before is drawn.

Therefore, the storage capacity of the electronic computer attached to the electron beam exposure apparatus can be made smaller than before, and a photomask having a more faithful and accurate pattern than before can be obtained. That is, as the amount of dimensional shift corrected by adding to the exposure data is reduced, the error is also reduced, and a pattern faithful to the design pattern can be produced with high accuracy.

The above embodiment uses CrO) as the light shielding pattern. Membrane, Cr
The explanation was given using a composite metal film pattern consisting of a film as an example.
It goes without saying that the present invention can also be applied to photomasks having light-shielding patterns made of other materials.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the storage capacity of the electronic computer attached to the electron beam exposure apparatus can be reduced, and a photomask such as a reticle with a more faithful and accurate pattern than before can be manufactured. can be shaped,
This contributes to improving the performance and quality of semiconductor devices such as LSI.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a photomask according to the present invention, FIG. 2 is a sectional view showing an exposure method according to the invention, FIG. 3 is a sectional view of a conventional photomask, and FIG. 4 is a sectional view of a conventional exposure method. FIG. In the figure, 1 is a quartz glass substrate, 2 is a light shielding pattern or a metal film, 21. 23 is Cry. 22 is a Cr film; 3 is a C-containing light-shielding pattern or a C-containing metal film; 31
．． 33 is a C-containing CryX film, 32 is a C-containing Cr film, 5 is a resist film, 52. Reference numeral 53 indicates an exposure area, and EB indicates an electron beam. Figure 4

Claims (1)

[Claims] A photomask characterized in that a light-shielding pattern provided on a transparent substrate contains carbon atoms.