JPH06258815A - Production of phase phase shift mask - Google Patents

Abstract

PURPOSE:To make it possible to etch a transparent film for forming the phase shifters of the phase shift mask by a dry etching. CONSTITUTION:The oxygen content of transparent SiOx films 3 formed to coat Cr light shielding films 2 formed periodically on a glass substrate 1 is set slightly higher than that of a glass substrate 1. Free S (sulfur) is dissociated and formed from S2F2 if the transparent SiOx films 3 are etched by using S2F2. This S is burned and removed on the expose surfaces of the transparent SiOx films 3 from which a large quantity of O atoms are released by an ion sputtering effect and, therefore, the etching is not hindered. On the other hand, the S deposits on the resist mask 4 or light shielding Cr films 2 which hardly release the O atoms or on the exposed surface of a glass substrate 1 which release the O atoms in a smaller amt. A high selection ratio is thus assured. The deposited S is simultaneously removed at the time of ashing the resist mask 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a phase shift mask used as a photomask (reticle) for photolithography in the field of manufacturing semiconductor devices, and more particularly, to dry etching of a phase shifter on a transparent substrate. -Regarding a method that can be performed by etching.

[0002]

2. Description of the Related Art In the field of semiconductor integrated circuits, sub-micron level processing has already been realized in mass-production plants, and quarter-micron level processing will become essential in the future half-micron level and further in the 64-Mbit DRAM class.
Research on level processing is underway.

Photolithography is a key technology for the progress of such fine processing, and the conventional progress has been achieved mainly by improving the optical system of the stepper (reduction projection exposure apparatus). The limit resolution R of this optical system is represented by the following equation known as the Rayleigh equation. R = k ₁ × λ / NA where k ₁ is a proportional constant, λ is the exposure wavelength, and NA is the numerical aperture of the reduction projection lens. Conventionally, i of high pressure mercury lamp
Line (365 nm) or KrF excimer laser light (248 nm) and other far ultraviolet rays are used to shorten the exposure wavelength, and the stepper (reduction projection exposure device) reduction projection lens has a high numerical aperture (NA) Efforts have been put into. However, these improvements have practically reached the limit. In addition, shortening the wavelength and increasing the numerical aperture make the depth of focus DO
Since F (= k ₂ × λ / NA ² : k ₂ is a proportional constant) is reduced, there is a limit to the pursuit of the limit resolution R.

Under such circumstances, a so-called super-resolution technique has been attracting attention, in which the numerical aperture NA is suppressed to a certain level and a practical level of depth of focus is secured, and then the harmonic component of the exposure light is used to increase the resolution. There is. One of this super-resolution technology,
There is a phase shift method. This is a method for improving the resolution by giving a phase difference to the exposure light transmitted through the photomask and utilizing the mutual interference of the transmitted light. This phase difference is usually set to 180 °, that is, the inverted state.

The principle of resolution improvement by the phase shift method is roughly classified into spatial frequency modulation and edge enhancement, and various kinds of phase shift masks have been proposed by combining these principles and a mask structure. Typical examples thereof include a Levenson type phase shift mask, a phase shift mask with an auxiliary pattern, a self-aligned phase shift mask, and a transmission type phase shift mask.

In the phase shift method, in order to generate a phase difference, it is necessary to form a phase shifter in a specific pattern on a glass substrate which constitutes a reticle. This phase shifter is most commonly formed by patterning a transparent film such as SOG (spin on glass) having a refractive index different from that of the glass substrate. As another type of phase shifter, there is one in which a groove portion is formed by etching the glass substrate itself in a predetermined pattern. In this case, since only the depth of the groove is replaced with the air layer having a different refractive index from the glass substrate, a phase difference occurs between the light transmitted through the groove and the light transmitted around it. However, it is easier to control the film thickness of the transparent film than to control the etching depth of the groove.

[0007]

By the way, in the case of patterning a transparent film on a transparent substrate, a conventional general method is to perform etching by an electron beam resist material by direct writing and development processing by an electron beam writing apparatus.・
A mask was formed and wet etching was performed through this mask.

However, if the design rules of semiconductor devices are further miniaturized in the future, it can be said that the pattern size on the reticle is five times larger than that on the semiconductor wafer.
Significantly reduced than before. In such a case, in order to realize a sharp phase inversion at the edge portion of the phase shifter, it becomes necessary to control the cross-sectional shape of the phase shifter to a good anisotropic shape. From this point of view, dry etching that can achieve anisotropic processing by an ion assist mechanism is more advantageous than wet etching in which an isotropic etching reaction proceeds.

Further, when the pattern on the reticle becomes finer, when the transparent substrate is immersed in the etching solution in wet etching, the Cr light-shielding film and the transparent substrate are not sufficiently adhered to each other, resulting in the Cr light-shielding film. May peel off,
From this viewpoint as well, there is an increasing need to consider dry etching.

Further, as an essential problem in the etching of the phase shifter, since the transparent substrate and the phase shifter are often made of the same type of material, it is difficult to secure sufficient selectivity between them. Is mentioned. conventionally,
This problem has been solved by interposing an etching stopper layer between the transparent substrate and the transparent film. However, this method requires an extra step for forming the etching stopper layer, which also causes the cost of the phase shift mask, which tends to increase in cost, to further increase.

Therefore, the present invention ensures a sufficiently large selection ratio for a transparent substrate by dry etching,
An object of the present invention is to provide a method for manufacturing a phase shifter mask, which is capable of forming a phase shifter by etching a transparent film.

[0012]

The method of manufacturing a phase shift mask of the present invention is proposed to achieve the above-mentioned object, and a transparent film is etched on a transparent substrate to form a desired pattern. In forming the phase shifter having the above, an etching gas containing a sulfur-based compound capable of releasing free sulfur into plasma under discharge dissociation conditions is used, and the etching is performed while depositing the sulfur on at least a part of the substrate. It is characterized by performing.

The present invention also provides that the sulfur compound is S ₂
It is characterized in that it is at least one kind of sulfur fluoride selected from F ₂ , SF ₂ , SF ₄ , and S ₂ F ₁₀ .

The present invention is also characterized in that the sulfur compound has a thiocarbonyl group and a fluorine atom in the molecule.

The present invention is also characterized in that the etching gas contains a nitrogen compound.

The present invention also provides that the etching gas comprises:
It is characterized by containing at least one kind of fluorine radical consuming compound selected from H ₂ , H ₂ S and silane compounds.

In the present invention, the transparent substrate and the transparent film are both made of a silicon oxide (SiO _x ) type material,
The oxygen content of the transparent film is larger than that of the transparent substrate.

The present invention is further characterized in that the oxygen content of the transparent film is controlled to a desired value by controlling the amount of oxygen in the vapor phase growth atmosphere or by implanting oxygen ions.

[0019]

The present inventor assumes that the transparent film for obtaining the phase shifter is mainly formed of SiO _x type material as in the conventional case, and can release free sulfur (S) into plasma under discharge dissociation conditions. We considered etching this transparent film using a sulfur compound.

S is a sublimable substance which can be removed without leaving any contamination when heated to about 90 ° C. under a reduced pressure such that ordinary etching is carried out, but the temperature of the substrate is lower than this, preferably S. It is also a depositable substance that deposits on the surface and protects the surface if it is controlled at room temperature or lower. Here, the site where S can be deposited on the surface of the substrate is the site where vertical incidence of ions does not occur or a large amount of oxygen (O) atoms are not supplied due to etching. Considering the manufacturing process of the phase shift mask, these portions are the side wall surface of the pattern, the surface of the resist mask, the exposed surface of the Cr light shielding film, and the like. By depositing such S, the anisotropic shape of the phase shifter is achieved, and high selectivity is secured for the resist mask and the Cr light shielding film.

On the contrary, the site where S cannot be deposited is the vertical ion incident surface of the SiO _x -based material layer which releases a large amount of O atoms as it is etched. That is, at this site, S combines with sputtered out O atoms to produce SO _x , which is burned and removed. Therefore, the etching of the SiO _x material layer proceeds smoothly. After the etching is completed, S can be easily burned and removed in the ashing step for removing the resist mask. Therefore, S does not cause any particle contamination.

The deposition of S is as described above, but in order to remove Si which is one of the constituent elements of the SiO _x transparent film, a high energy is generated between the halogen radicals, especially Si atoms. Conveniently, there is an F ^* present in the etching reaction system that can form a bond. The four types of sulfur fluorides of S ₂ F ₂ , SF ₂ , SF ₄ , and S ₂ F ₁₀ used in the present invention are compounds selected from such a viewpoint, and the applicant of the present invention has previously disclosed the method described in Japanese Patent Laid-Open No. -84427 gazette. F ^* produced from these sulfur fluorides volatilizes and removes Si atoms in SiO _x in the form of SiF _x .

The other of the sulfur compounds proposed in the present invention is a compound having a thiocarbonyl group (> C = S) and a fluorine atom in the molecule. In addition to the above-described S as a depositable substance, this compound can also generate a carbon-based polymer. This carbon-based polymer has much higher etching resistance than the fluorocarbon-based polymer that has played the role of protecting the side wall in the conventional dry etching.
This is larger than the C—F bond (536 kJ / mol) in the comparison of interatomic bond energies.
99 kJ / mol) is incorporated into the molecular structure,
Further, because thiocarbonyl having a dipole is incorporated into the molecular structure, the electrostatic adsorption force on the negatively charged substrate is increased during etching.

The present invention further proposes to add a nitrogen compound to the etching gas. This is intended to generate various sulfur nitride compounds by coexisting S and N in the etching reaction system to further enhance the surface protection effect. Various compounds are known as the above-mentioned sulfur nitride-based compound, as will be described later. Regarding the use of this compound for the surface protection of the substrate during etching, the applicant of the present application has previously filed Japanese Patent Application No. 3-155454.
It is as first proposed and detailed in the specification.

In the present invention, a typical sulfur nitride-based compound expected to have a side wall protecting effect is polythiazyl (S
N) _x . This polymer is S--N-- in the crystalline state.
It has a structure in which covalently bonded chains having a repeating structure of S-N -... are oriented in parallel, and shows higher resistance to attack of etching species than S of simple substance. In the present invention, since F ^* is present in the plasma, thiazyl fluoride having F atoms bonded to the S atoms of (SN) _x can also be generated. Also,
Thiazyl hydrogen may also be produced in systems in which H ^* is present.

Further, depending on the conditions, a cyclic sulfur nitride compound in which the number of S atoms and N atoms in the molecule is unbalanced, or an imide type compound in which an H atom is bonded to the N atom of these cyclic sulfur nitride compounds is also produced. It is possible.

Depending on the conditions, these sulfur nitride compounds can be deposited on the surface of the substrate as long as the substrate is maintained at a temperature lower than about 130.degree. However, like S, it cannot be deposited on the surface of a material that sputters out a large amount of O atoms, and is removed in the form of SO _x , NO _x, or the like. The surface protection effect on other portions, that is, the side wall surface of the pattern, the surface of the resist mask, the exposed surface of the Cr light-shielding film, and the like is the same as S. Moreover, since the sulfur nitride-based compound is easily removed by a mechanism such as sublimation, decomposition, and combustion in the usual ashing process performed after the etching is completed, it does not cause any particle contamination.

In the present invention, the etching gas may be any one selected from H ₂ , H ₂ S and silane compounds.
It is proposed to add a type of fluorine radical consuming compound to improve the production efficiency of S or sulfur nitride compounds. H ^* and / or Si ^* released from these fluorine radical consuming compounds are fluorine radicals F
^It plays the role of capturing ^* , converting it into a highly volatile compound and removing it from the etching reaction system. Therefore, the apparent S / F ratio (ratio of the number of S atoms and the number of F atoms) of the etching reaction system increases, and the surface protection effect can be enhanced.

Although it has been described above that the transparent film made of the SiO _x type material can be etched by using the sulfur type compound, there are important points to be further considered.
That is, when both the transparent substrate and the transparent film are made of a SiO _x material, how to secure the selection ratio between them. In order to achieve the object of the present invention, an etching reaction system is constructed so that the etching reaction preferentially proceeds on the transparent film and the deposition of S and / or sulfur nitride compound preferentially proceeds on the transparent substrate. It is necessary to.

Therefore, in the present invention, the oxygen content of the transparent film is set higher than that of the transparent substrate. According to this setting, by optimizing the etching conditions, during the etching of the transparent film, a large amount of O atoms released from the transparent film promotes the decomposition and removal of S and sulfur nitride-based compounds, so that the exposed surface of the transparent substrate Then, it becomes possible to reduce the released O atoms and promote the deposition of S and sulfur nitride compounds.

Further, in order to increase the oxygen content of the transparent film, it is considered as a practical method to control the oxygen amount in the vapor phase growth atmosphere or to implant oxygen into the transparent film before the etching. To be It is known that SiO _x materials exhibit a change in refractive index n with a change in oxygen content. For example, "CVD Handbook"
(Chemical Engineering Association, published by Asakura Shoten) p. 223 shows that when a SiO _x film is formed by low pressure CVD using SiH ₄ —N ₂ O mixed gas having various mole fractions, the refractive index n decreases as the oxygen content increases. It is shown.

In the phase shift mask, the phase is set to 18
The film thickness d of the phase shifter required to invert 0 ° is d =
Since it is represented by λ / 2 (n-1) (1 is the refractive index of air), it is important to determine the film thickness of the transparent film according to the oxygen content.

[0033]

EXAMPLES Specific examples of the present invention will be described below based on experimental results.

Example 1 In this example, a SiO _x transparent film on a glass substrate was subjected to S ₂ F _{2 in the} process of manufacturing a Levenson-type phase shift mask.
This is an example of etching using. This process will be described with reference to FIG. The mask substrate used as an etching sample in this example is shown in FIG.
Shown in. The mask substrate has a Cr light-shielding film 2 formed in a predetermined pattern on the glass substrate 1, SiO _x transparent film 3 is deposited further formed on the entire surface, the SiO _x on the
A resist mask 4 is formed in a predetermined pattern as an etching mask for the transparent film 3.

Here, the oxygen content of the glass substrate 1
Is the general formula SiO_xAt about x = 2.0. the above
SiO_xThe transparent film 3 is, for example, ECR-
It is formed by performing CVD. SiH_FourFlow rate 10 SCCM O₂Flow rate 20 SCCM Ar Flow rate 10 SCCM Gas pressure 0.1 Pa Microwave power 800 W (2.45 GHz) Substrate temperature 300 ° C. SiO formed in this way_xOxygen content of transparent film 3
The amount is the general formula SiO_xAt about x = 2.2,
It is higher than that of the glass substrate 1. Also, this
Obtained in the case of_xHas a refractive index n of about 1.45.
I know that In this example, the phase to be produced
Mount the shift mask on the i-line stepper (λ = 365 nm)
Assuming that it is listed, above the equation d = λ / 2 (n-1),
Note SiO _xThe film thickness d of the transparent film 3 was set to 405 nm.

The resist mask 4 is a Cr light shielding film 2
Are formed so as to cover every other opening pattern. This is to achieve the purpose of the Levenson-type mask of inverting the phase of transmitted light by 180 ° between fine adjacent patterns in a periodic pattern such as line-and-space.

Next, the above mask substrate was set in an RF bias application type magnetic field microwave plasma etching apparatus, and as an example, the SiO _x transparent film 3 was etched under the following conditions. S ₂ F ₂ flow rate 30 SCCM Gas pressure 1 Pa Microwave power 800 W (2.45 GHz) RF bias power 30 W (2 MHz) Substrate temperature −10 ° C. (using ethanol-based coolant) Under these etching conditions, the SiO _x transparent film 3 is etched. Although it is allowed to proceed, it is optimized so that etching is stopped on the glass substrate 1 below it.

In this process, the SiO _x transparent film 3 is selectively removed in the form of SiF _x , SO _x or the like by ion mode etching due to the contribution of ions such as SF _x ⁺ generated by dissociation from S ₂ F _2. Was done. Further, S was also released from S ₂ F ₂ . This S exhibits various behaviors depending on the cooled portion on the mask substrate.

FIG. 1B shows a state in the middle of etching. S was deposited on the pattern side wall surface where vertical incidence of ions did not occur in principle, and the side wall protective film 5 was formed. As a result, the etching of the SiO _x transparent film 3 proceeded anisotropically. On the other hand, the situation is slightly different on the vertical incidence plane of the ions. That is, on the surface of the resist mask 4, the process of depositing S on the cooled surface and the process of removing the spatter thereof by the incident ions compete with each other to protect the surface. Sex is secured. In FIG. 1B, the area where the surface protection is performed is indicated by a broken line as the surface protection area 6.

On the other hand, on the exposed surface of the SiO _x transparent film 3, since O atoms are released from this film due to the sputtering action of incident ions, the S adsorbed to this portion immediately becomes S.
It is changed to O _x and burned off. Therefore, S does not deposit on this exposed surface, and etching proceeds smoothly.

As the etching progresses further, FIG.
As shown in (c), the Cr light-shielding film 2 and the glass substrate 1 were sequentially exposed. Since O atoms were not sputtered out from the Cr light-shielding film 2, the S deposition process and the sputter-removal process competed on the exposed surface, and a high selectivity for the Cr light-shielding film 2 was secured. Further, although the glass substrate 1 contains oxygen as a constituent element, since the etching conditions are set in accordance with the SiO _x transparent film 3 having a high oxygen content, the etching does not proceed on the surface thereof, and the deposition of S has priority. It happened. Therefore, the exposed surfaces of the Cr light shielding film 2 and the glass substrate 1 became the surface protection region 6. Since the side wall protection continues during this time, the phase shifter 3a having an anisotropic shape was formed.

After that, the mask substrate was transferred to an ashing device and ordinary O ₂ plasma ashing was performed. As a result, as shown in FIG. 1D, the resist mask 4
Was removed. At the same time, S adhering to the side wall protective film 5 and the surface protective region 6 was also sublimated or burned and removed without causing any particle contamination. When the phase shift mask thus formed is mounted on an i-line stepper and an i-line (hν) is incident thereon, the Cr light-shielding film 2 is formed.
The phases of the transmitted light are mutually inverted between the adjacent openings that are opened, and the light intensity at the boundary becomes 0, and a fine pattern can be separated based on the principle of spatial frequency modulation.

Example 2 In this example, an etching gas in which H ₂ was added as a fluorine radical consuming compound to S ₂ F ₂ used in Example 1 was used to enhance the deposition efficiency of S and improve the selectivity. This is an example of the above. The mask substrate used in this example is the same as in Example 1. This mask substrate was set in a magnetic field microwave plasma etching apparatus, and as an example, the SiO _x transparent film 3 was etched under the following conditions.

S ₂ F ₂ flow rate 25 SCCM H ₂ flow rate 10 SCCM Gas pressure 1 Pa Microwave power 800 W (2.45 GHz) RF bias power 25 W (2 MHz) Substrate temperature −10 ° C. (ethanol-based refrigerant used) In the above gas system, Part of F ^* generated from S ₂ F ₂ is trapped by H ^* generated from H ₂ to generate HF (hydrogen fluoride).
, The apparent S / F ratio of the etching reaction system increased. As a result, the deposition or adsorption of S on the mask substrate was promoted, and the selectivity was further improved as compared with Example 1.

Example 3 In this example, SiO_xWith the etching gas for the transparent film 3
Then CSF₂Example using (thiocarbonyl fluoride)
It An example of etching conditions is shown below. CSF₂Flow rate 30SCCM Gas pressure 1Pa Microwave power 800W (2.45GHz) RF bias power 25W (2MHz) Substrate temperature -10 ° C (ethanol-based refrigerant
Use) In this etching process, SiO_xOn the exposed surface of the transparent film 3
At CSF₂Dissociated from F^*By deer
Le reaction is also CSF₂CF generated from_x ⁺, CS
⁺, SF_x ⁺Is assisted by the incident energy of ions such as
Etching progressed by the mechanism. At this time, CSF₂
At the same time, carbon-based polymer and S were also produced. these
The depositable material forms the side wall protective film 5 on the side wall surface of the pattern.
Resist mask 4, Cr light-shielding film 2, glass substrate
The surface protection effect was exhibited on the exposed surface of No. 1. Note that Si
O_xIn the process of burning and removing S on the exposed surface of the transparent film 3,
This is as described above in Example 1, but in this part
Is also a carbon-based polymer_xBurned away in the form of
The etching proceeded smoothly.

Also in this embodiment, excellent high selective / anisotropic etching was realized.

Example 4 In this example, etching was performed by adding H ₂ as a fluorine radical consuming compound to the CSF ₂ used in Example 3.
This is an example in which a gas is used to increase the deposition efficiency of S and improve the selectivity. Using the mask substrate shown in FIG. 1A, the SiO _x transparent film 3 was etched under the following conditions as an example.

CSF ₂ flow rate 25 SCCM H ₂ flow rate 5 SCCM Gas pressure 1 Pa Microwave power 800 W (2.45 GHz) RF bias power 25 W (2 MHz) Substrate temperature −10 ° C. (using ethanol-based refrigerant) CSF _{2 in the} above gas system Part of F ^* generated from H is consumed by H ^* , and the apparent S of the etching reaction system is
By increasing the / F ratio, the selectivity was further improved as compared with Example 3.

Example 5 In this example, the SiO _x transparent film 3 was similarly etched using an etching gas in which N ₂ was added to S ₂ F ₂ as a nitrogen-based compound. An example of etching conditions is shown below. S ₂ F ₂ flow rate 30 SCCM N ₂ flow rate 10 SCCM Gas pressure 1 Pa Microwave power 800 W (2.45 GHz) RF bias power 20 W (2 MHz) Substrate temperature 10 ° C (using ethanol-based refrigerant)

In the above-mentioned gas system, the etching proceeds by a mechanism in which the radical reaction by F ^* generated from S ₂ F ₂ is assisted by the incident energy of ions such as SF _x and N _x ⁺ . Further, some of the S atoms released from S ₂ F ₂ reacted with the N atoms released from N ₂ to form a sulfur nitride compound mainly composed of polythiazyl (SN) _x . This sulfur nitride-based compound exhibits higher etching resistance as compared with S as a simple substance. S and a sulfur nitride-based compound form a side wall protective film 5 on the side wall surface of the pattern, resist mask 4, Cr light shielding film 2, glass substrate 1
The surface protection effect was exhibited on the exposed surface of. However, Si
On the exposed surface of the O _x transparent film 3, the sulfur nitride-based compound is removed in the form of SO _x , NO _x, etc., and does not hinder the progress of etching.

In this embodiment, the RF bias power is reduced as compared with the first embodiment, and even though the substrate temperature is brought close to the room temperature range, similarly good high selection / anisotropic processing is performed. The phase shifter 3a could be formed.

Example 6 In this example, SiO 2 was also used._xEtching of transparent film 3
The S₂F₂/ N₂/ H ₂It was performed using a mixed gas. D
An example of the etching conditions is as follows. S₂F₂Flow rate 25 SCCM N₂Flow rate 5 SCCM H₂Flow rate 10 SCCM Gas pressure 1 Pa Microwave power 800 W (2.45 GHz) RF bias power 20 W (2 MHz) Substrate temperature Room temperature (water cooling) In the above gas system, H₂Etching reaction system
Apparent S / F ratio increases, and sulfur nitride compound
Strong sidewall protection and surface protection due to the formation of
It was As a result, the substrate temperature was raised more than in Example 5.
Despite the above, good high selection and anisotropic processing
I was able to do it.

Example 7 In this example, oxygen ion implantation was performed in order to increase the oxygen content of the SiO _x transparent film 3 as compared with that of the glass substrate 1. The structure of the mask substrate used in this example is as shown in FIG. However,
The ECR-CV is used for the SiO _x transparent film 3 in this embodiment.
As an example, after the film formation by the D method and before forming the resist mask 4, the implantation energy is 50 keV and the dose is 1
O ₂ ion implantation was performed under the condition of 0 ¹⁷ / cm ² . The oxygen content of the SiO _x transparent film 3 thus obtained is
In the general formula SiO _x, it was about x = 2.5, which was higher than the oxygen content (x = 2.0) of the glass substrate 1. The refractive index n of the SiO _x transparent film 3 is 1.40, and the film thickness d is 456 nm assuming i-line exposure.

The SiO _x transparent film 3 is etched using S ₂ F ₂ under the same conditions as in Example 1 or using an S ₂ F ₂ / H ₂ mixed gas under the same conditions as in Example 2. In every case, good high selection and anisotropic processing could be performed.

Although the present invention has been described based on the seven examples, the present invention is not limited to these examples. For example, sulfur fluoride is S ₂ F
_{Although 2} has been described as an example, basically the same result can be obtained by using other sulfur fluorides limited in the present invention. As the nitrogen-based compound, in addition to N ₂ described above, NF ₃ ,
NO _{x and the} like can also be used.

H ₂ is used as the fluorine radical consuming compound.
However, other H ₂ S limited by the present invention has been described.
Similar results can be obtained by using or a silane compound.
Since H ₂ S itself is also the source of S, it has a large effect of increasing the S / F ratio of the etching reaction system. Further, silane compounds, because in addition to H ^* Si ^* also contribute to the capture of F ^*, a large effect of increasing also S / F ratio.

In each of the above-described embodiments, the Levenson-type mask is manufactured based on the principle of spatial frequency modulation. However, other types of phase shifters to which the present invention can be applied.
As the mask, there are a transmission type phase shift mask which does not have a Cr light-shielding film and is based on the principle of spatial frequency modulation, a mask with an auxiliary pattern based on the principle of edge enhancement, and also a self-aligned mask.

Further, it goes without saying that the film forming conditions, film thickness, exposure wavelength, etching conditions and the like of the SiO _x transparent film can be changed as appropriate.

[0059]

As is apparent from the above description, by applying the present invention, the etching of the phase shifter, which was conventionally performed mainly by wet etching, can be performed by dry etching. Therefore, in response to the future reduction in design rules of semiconductor devices, it is possible to anisotropically process a phase shifter having a fine pattern while maintaining high selectivity with respect to a transparent substrate or a Cr light shielding film. It is possible to manufacture a highly reliable phase shift mask.

The present invention is extremely promising as a life prolonging measure for i-line lithography, and as a result, 0.35 to 0.4 μm
It becomes possible to manufacture a semiconductor device such as a 64 Mbit DRAM or a 16 Mbit SRAM whose main pattern rule is according to the above with high reliability.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a process in which the present invention is applied to manufacture of a Levenson-type phase shift mask in the order of steps, in which (a) shows a state where a resist mask is formed on a SiO _x transparent film. , (B) shows a state where the SiO _x transparent film has been partially etched, (c) shows a state where the Cr light-shielding film and the glass substrate are partially exposed, and (d) shows a resist mask by ashing. ,
The state where the side wall protective film and the like are removed is shown.

[Explanation of symbols]

1 ... Glass substrate 2 ... Cr light-shielding film 3 ... SiO _x transparent film 4 ... Resist mask 5 ... Side wall protection film 6 ... Surface protection region

Claims (7)

[Claims] 1. A method for manufacturing a phase shift mask, wherein a transparent film laminated on a transparent substrate is etched to form a phase shifter for shifting a phase of exposure light in a desired pattern, wherein the etching is performed. Manufacturing of a phase shift mask characterized by using an etching gas containing a sulfur-based compound capable of releasing free sulfur into plasma under discharge dissociation conditions and depositing this sulfur on at least a part of a substrate. Method. 2. The sulfur-based compound is S ₂ F ₂ , S
_{2. The} method for manufacturing a phase shift mask according to claim 1, wherein at least one kind of sulfur fluoride selected from F ₂ , SF ₄ , and S ₂ F ₁₀ is used. 3. The method of manufacturing a phase shift mask according to claim 1, wherein the sulfur compound has a thiocarbonyl group and a fluorine atom in the molecule. 4. The method of manufacturing a phase shift mask according to claim 1, wherein the etching gas contains a nitrogen compound. 5. The etching gas is H ₂ , H
_The method for manufacturing a phase shift mask according to claim 1, further comprising at least one fluorine radical consuming compound selected from ₂ S and silane compounds. 6. The transparent substrate and the transparent film are both made of a silicon oxide based material, and the oxygen content of the transparent film is larger than that of the transparent substrate. A method for manufacturing a phase shift mask according to claim 5. 7. The oxygen content of the transparent film is controlled to a desired value by controlling the amount of oxygen in a vapor phase growth atmosphere or by implanting oxygen ions. The method for manufacturing the phase shift mask according to any one of items.