JPH08213302A - Fine processing method and fine processing photomask used for said method - Google Patents

Abstract

PURPOSE: To provide a fine processing method not to deteriorate the alignment precision between an exposure mask and a work resultant from the step advancement. CONSTITUTION: A sufficient number of alignment marks MOK11 -MOK13 applicable for the latter steps are formed on a work 1 in the initial step so that different marks may be successively applied in every after steps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine processing method suitable for use in manufacturing a semiconductor integrated circuit or a liquid crystal display panel, for example.

[0002]

2. Description of the Related Art A conventional fine processing method will be described with reference to FIGS. In this example, a case where the object 1 to be processed is a semiconductor substrate and two electrodes 4 and 5 having different materials shown in FIG. 9E are formed on the object 1 to be processed will be described. As shown in FIG. 8A, an insulating layer 2 such as SiO ₂ is formed on one surface of the workpiece 1, and a photoresist layer F is formed on the upper surface of the insulating layer 2. A first photomask M1 is arranged so as to face the photoresist layer F formed on the workpiece 1, and the photoresist layer F is exposed through the first photomask M1.

After the exposure / development process, the insulating layer 2 is left in the states 2 and 2A shown in FIG. 8B by etching using the remaining photoresist layer F as a mask. The insulating layer 2A left in this step is used as a positioning mark MOK1 when a photomask is used in the subsequent step. It is assumed that the illustrated insulating layer 2 is formed in a frame shape, and the ion-implanted layer 3 is formed by implanting ions, for example, into the inner surface of the frame-shaped insulating layer 2.

FIG. 8B shows a state in which a metal layer 4A for forming an electrode 4 is formed on the surface of the workpiece 1 on which the insulating layers 2 and 2A are left in a predetermined pattern, by a method such as vapor deposition. . In order to form the electrode 4 from this metal layer 4A,
A photoresist layer F is again formed on the upper surface of the metal layer 4A as shown in FIG. 8C, and a second photoresist mask M2 is arranged to face the photoresist layer F as shown in FIG. 8D. , The photoresist layer F is exposed through the second photomask M2. When the second photomask M2 is arranged to face the photoresist layer F, the alignment mark MOK1 formed on the workpiece 1 and the second photomask M2.
The mark pattern MOK2 of No. 2 is aligned and arranged, and exposure / development processing is performed.

The exposure / development process shown in FIG. 8D leaves the photoresist layer F as shown in FIG. 8E. Etching is performed using the remaining photoresist layer F as a mask to form the electrode 4 shown in FIG. 8F. In this case, the alignment mark MOK1 is formed by depositing the metal layer 4A on the insulating layer 2A. Next, the step of forming the electrode 5 will be described with reference to FIG.

With the electrode 4 formed, a metal layer 5A for forming the electrode 5 is formed on the upper surface thereof as shown in FIG. 9A. The electrode 4 is made of, for example, tungsten silicide, and the electrode 5 is made of gold or the like. The metal layer 5A is covered with a photoresist layer F as shown in FIG.
As shown in C, the third photomask M3 is faced to expose the portion other than the formation position of the electrode 5 and the alignment mark MOK1. In this case, the mark pattern MOK2
Is aligned with the alignment mark MOK1 formed on the workpiece 1 side, and the formation position of the electrode 5 is determined.

By exposing using the third photomask M3, as shown in FIG. 9D, the photoresist F is left at the position where the electrode 5 is to be formed and the position facing the alignment mark MOK1. The metal layer 5A is etched by using the resist F to form the electrode 5. At this time, the metal layer 5A is left in the shape of the mark also on the alignment mark MOK1.

[0008]

As described with reference to FIGS. 8 and 9, in the prior art, the second photomask M is initially made using the alignment mark MOK1 formed on the workpiece 1.
2. Since the alignment of the third photomask M3 is performed, the shape of the alignment mark MOK1 is deformed as the process progresses, and the alignment accuracy gradually deteriorates.

That is, since the mark pattern MOK2 formed on the photomasks M1, M2 and M3 is also formed in the same shape as the alignment mark MOK1 formed on the side of the workpiece 1, the metal layers 4A and 5A, for example. If the position where the mark is formed is slightly shifted, the shape of the alignment mark MOK1 is deformed and the position of the alignment mark MOK1 is displaced. FIG. 10 shows the state. As shown in FIG. 10, the position of the insulating layer 2A and the metal layer 4 formed thereon
Mark position by A and metal layer 5 further formed thereon
If the formation position of A is slightly shifted, the shape of the alignment mark MOK1 is deformed, which causes a problem that mask alignment of a fine pattern in the subsequent steps becomes difficult.

For this reason, for example, when manufacturing a high-speed response type FET or the like, it is necessary to position the gate electrode and the source / drain electrode with a narrow and accurate position, but to determine the position of the mask. Since the shape of the alignment mark MOK1 is deformed as the process goes through, it becomes impossible to perform accurate positioning, which is an obstacle in manufacturing a high-speed response type semiconductor element.

An object of the present invention is to provide a fine processing method in which the shape of the alignment mark formed on the object to be processed does not change even if the steps are advanced, and a photomask used in this fine processing method.

[0012]

According to the present invention, a plurality of alignment marks corresponding to the number of processes using a photomask in the initial process are formed on a workpiece and prepared. It proposes a method of aligning with a photomask by sequentially using. That is, when exposure is performed using the first photomask, mark patterns corresponding to the number of photomasks to be used thereafter are formed on the first photomask, and the workpiece is processed using the mark patterns. In advance, a plurality of alignment marks are formed.

A light-shielding mark pattern is formed on the second photomask at a position corresponding to the first alignment mark formed on the workpiece, and the mark pattern and the first alignment mark are used to form a first pattern. 2 Align the photomask with the work piece. At this time, the other alignment marks are exposed to light so that the photoresist layer is not left at the positions of the alignment marks not used for alignment.

Therefore, in the etching process using the photoresist layer as a mask, a metal layer is left in the shape of the mark on the mark used as the alignment mark, but it is not used as another alignment mark. The metal layer is removed from the alignment mark. As described above, when the metal layer formed on the upper surface of the alignment mark is removed by etching, the etching liquid used at that time uses an etching liquid having a property of etching only the metal, and thus is formed of an insulating layer. Even if the alignment mark is exposed and comes into contact with the etching solution, the shape of the alignment mark does not change.

Therefore, according to the present invention, even if the number of steps using the photomask is large, the position of the positioning mark gradually shifts because the positioning mark prepared for each step using each photomask is used. There is no. Therefore, there is an advantage that fine processing can be performed with high precision.

[0016]

1 to 6 show an embodiment of a fine processing method according to the present invention. FIG. 1 is the first used at the beginning of the present invention.
An example of the photomask M1 is shown. The first photomask used for the microfabrication of the present invention has, in addition to the main pattern PAO formed on the object to be processed, an alignment mark pattern MOK2 of a number sufficient for the number of photomasks used in the subsequent steps.
_The structure is characterized by having ₁ , MOK2 ₂ , and MOK2 ₃ .

FIG. 2 shows the first photomask M1 shown in FIG.
It shows the state in which the insulating layer 2 was etched by exposure using. The frame-shaped insulating layer 2 is, for example, an insulating layer that surrounds a region for forming a high-speed field effect transistor. Ions are already implanted into the region surrounded by the insulating layer 2 to form the ion-implanted layer 3. Although shown alignment marks MOK1 _1, MOK1 _2, MOK1 ₃ only one pair in the figure, the workpiece alignment marks MOK1 ₁ to each other away in 1, MOK1 _2, MOK1 ₃ multiple In some cases, a set is formed.

The examples shown in FIGS. 1 and 2 show the case where three alignment marks MOK1 ₁ , MOK1 ₂ and MOK1 ₃ are formed. In the state shown in FIG. 2, each of the alignment marks MOK1 ₁ , MOK1 ₂ and MOK1 ₃ is formed of the insulating layer 2A. A metal layer 4A is deposited on the entire surface in the state of FIG. 2 by a method such as vapor deposition as described in FIG. 8B, and a photoresist layer F is further deposited on the upper surface thereof as described in FIG. 8C. . For this photoresist layer F,
Exposure is performed using the second photomask M2 shown in FIG.
The second photomask M2 has an electrode forming pattern PA ₁ for forming the electrode 4 shown in FIG. 9E and an alignment mark M.
Mark pattern M for alignment with OK1 ₁
OK2 ₁ is formed. In this embodiment, a positive type photoresist is used as the resist forming the photoresist layer F. Therefore, these electrode forming patterns PA
_The mark ₁ and the mark MOK2 ₁ are formed of a light-shielding member, and the electrode forming portion and the alignment mark MO are formed on the photoresist layer F.
Shield the K1 ₁ part and irradiate the part to be removed with light,
The photoresist layer F in the light-irradiated portion is easily dissolved in the developing solution, and the photoresist layer F in the light-irradiated portion is
Is removed.

Therefore, the second photomask M2 shown in FIG.
Exposure is performed to leave the photoresist layer F in a light-shielded portion, and etching is performed using the remaining photoresist layer F as a mask. As shown in FIG. 4 is formed. Further, the metal layer 4A is left in the shape of the mark on the upper surface of the alignment mark MOK1 ₁ . In this state, other alignment marks MOK1 ₂ ,
The initial insulating layer 2A is exposed on the upper surface of MOK1 ₃ . Since the alignment marks MOK1 ₂ and MOK1 ₃ formed by the insulating layer 2A have durability against the etching solution for etching the metal layer 4A, their shapes do not change.

Next, in the step for forming the electrode 5 shown in FIG. 9E, the third photomask M3 shown in FIG. 5 is used.
The electrode forming pattern PA ₂ is formed on the third photomask M3.
And a mark pattern MOK2 ₂ for alignment with the alignment mark MOK1 ₂ . Third
When the photomask M3 is aligned with the workpiece 1, the alignment mark MOK1 ₂ which is maintained in the initially formed state is used.
Since K1 ₂ is not deformed as the process progresses, the alignment can be performed accurately.

As a result, when the third photomask M3 is used for exposure and etching, as shown in FIG.
Can be formed. In this state, the metal layer 5A is left on the upper surface of the alignment mark MOK1 ₂ , and the unused mark MOK1 ₃ is maintained as the insulating layer 2A. FIG. 7 shows a modified embodiment of the present invention. In this embodiment, alignment marks MOK1 ₁ , MO formed on the workpiece 1 are used.
The case where numbers and symbols corresponding to the process number or the mask number to be used are attached in the vicinity of K1 ₂ and MOK1 ₃ , respectively. The example of FIG. 7 shows the case where the mask number NO to be used is added.

As described above, the alignment marks MOK1 ₁ to
By assigning a mask number NO used for alignment of each mark to each of MOK1 ₃
There is an advantage that it is possible to prevent an accident in which the masks used are mixed up. Further, in the above-mentioned embodiments, the object 1 is explained as a semiconductor substrate, but the present invention can be applied to other fine processing, for example, for manufacturing a liquid crystal display panel or a thin film magnetic head. Also,
In the above-described embodiments, the photoresist having the property that the portion not exposed to the light remains is used as the photoresist layer F, but the resist having the opposite property may be used. In this case, the light-shielding portion of the photomask described with reference to FIGS. 1, 3, and 5 may be reversed to have a negative or positive relationship.

Further, although explained how leaving no photoresist F on the upper surface of the unused alignment marks MOK1 _2, MOK1 ₃ in the above embodiment, the mark for alignment unused MOK1 _2, MOK1 ₃ 7 includes alignment marks MOK1 ₂ and MOK1 ₃ on the upper surface of FIG.
The photoresist layer is left as indicated by the dotted line in FIG. ₃ and the metal layer 4 is formed in the region including the alignment marks MOK1 ₂ and MOK1 _3.
Alternatively, 5 may be formed.

Thus, the alignment mark MOK
Even if the metal layer 4 or 5 is formed so as to remain in the region including 1 ₂ and MOK 1 ₃ , the alignment marks MOK 1 ₂ and MOK
1 ₃ bulges evenly by the thickness of the metal layer 4 or 5, and the position display does not change. Therefore, the initial position information can be maintained. Further, in the above-described embodiment, the alignment mark MOK1 ₁ , for each process using the photomask,
The case where MOK1 ₂ and MOK1 ₃ are sequentially used one by one has been described, but as another method, one alignment mask may be used twice. In this way, if the number of times the same alignment mask is used is limited, there is no possibility of causing a large alignment error even when compared with the conventional alignment method.

[0025]

As described above, according to the present invention, a plurality of flaps are used.
Exposure using a photomask
In the fine processing method to be performed,
Align the number of photomasks used at least
Mark MOK1₁, MOK1 ₂, MOK1₃Forming
And adopt the method of using these alignment marks one after another
Keep the initial shape every time the photomask is aligned
Alignment marks can be used.

As a result, even when the mask is used many times, the alignment accuracy does not deteriorate with the progress of the process, and there is an advantage that it is possible to perform fine processing with high accuracy.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a first photomask used for fine processing of the present invention.

FIG. 2 is a perspective view showing a part in section for explaining an embodiment of the present invention.

FIG. 3 is a plan view showing an example of a second photomask used in the present invention.

FIG. 4 is a perspective view showing a part in section for explaining a fine processing step of the present invention.

FIG. 5 is a plan view showing an example of a third photomask used in the present invention.

FIG. 6 is a perspective view showing a part in section for explaining a microfabrication process of the present invention, similar to FIG.

FIG. 7 is a perspective view similar to FIG. 1, showing a modified embodiment of the present invention.

FIG. 8 is a sectional view for explaining a conventional technique.

FIG. 9 is a cross-sectional view for explaining the conventional technique as in FIG.

FIG. 10 is an enlarged plan view for explaining the inconvenience of the conventional technique.

[Explanation of symbols]

1 Workpiece MOK1 _{1 to} MOK1 ₃ Alignment mark M1, M2, M3 Photomask MOK2 _{1 to} MOK2 ₃ Mark pattern

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical indication location H01L 29/43 H01L 21/30 570 21/302 J 29/46 T G

Claims (5)

[Claims] 1. A photoresist layer having a predetermined pattern is formed by arranging a photomask on which a predetermined pattern is drawn so as to face a surface of a workpiece on which the photoresist layer has been formed and exposed and developed. The number of photomasks used in subsequent steps in the microfabrication method in which the remaining photoresist layer is used as a mask and etching is performed to form the layer of the workpiece in a predetermined pattern. A mark pattern for forming a sufficient number of alignment marks on the workpiece, and the mark pattern is formed on the workpiece in a number corresponding to the number of photomasks to be used. Fine processing method. 2. The microfabrication method according to claim 1, wherein the alignment between the object to be processed and the photomask is performed by the different positioning marks for each step of using the photomask. Method. 3. The microfabrication method according to claim 1,
A fine processing method characterized in that a number or a code indicating the order of a photomask to be used is formed corresponding to each of a plurality of alignment marks. 4. A photomask for use in the microfabrication method according to claim 1, wherein the photomask for microfabrication comprises a number of mark patterns sufficient for the number of photomasks used during the process. 5. The photomask used in the microfabrication method according to claim 2, wherein mark patterns are formed at positions corresponding to the order of use assigned to each photomask. Photo mask.