JP3472397B2 - Dry etching method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a dry etching how in the manufacture of a semiconductor device.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, dry etching is a processing method mainly used for patterning an object to be processed. A typical patterning process is a photolithography process in which a resist film having a predetermined pattern consisting of a remaining portion and an opening is formed on the object to be processed, and the object below the opening in the resist film is removed. And a dry etching step.

Here, the patterning process of the gate electrode of the MOSFET will be described as an example. As shown in FIG. 12A, a silicon oxide film 7 to be a gate oxide film and a polysilicon film 4 to be a gate electrode are sequentially deposited on a silicon substrate 6, and then a resist is applied thereon to form a resist. The film 5 is formed. Then, a pattern including the remaining portion and the opening is formed on the resist film 5 by a photolithography process. Using the resist film 5 as an etching mask, the polysilicon film 4 is dry-etched.
In FIG. 1A, reference numeral 1 indicates active species, 2 indicates ions, and 3 indicates etching products.

At this time, a concave portion 9 is formed in the polysilicon film below the opening of the resist film 5, and a convex portion 8 is formed in the polysilicon film 4 below the remaining portion of the resist film 5. Also,
The convex portions 8 shown in FIG. 12A include isolated convex portions 8a having a large distance between adjacent convex portions (hereinafter referred to as isolated convex portions) and dense convex portions having a small distance between the convex portions. There is a portion 8b (hereinafter referred to as a dense convex portion), and similarly, each convex portion 8a, 8
There are isolated recesses 9a and dense recesses 9b on both sides of b. Then, by removing all of the polysilicon film 4 below the opening of the resist film 5, each of the protrusions 8a and 8b becomes a gate electrode, whereby the patterning of the gate electrode is completed. Dry etching using a reactive gas as an etchant causes etching products generated by the reaction between the workpiece and the etching gas, the decomposition of the etching gas, or the like on the sidewalls of the protrusions 8a and 8b formed by removing the workpiece. By adhering and blocking the progress of etching in the lateral direction, so-called anisotropic etching can be performed in which only the downward etching action is exerted. By such anisotropic etching, the protrusions 8a and 8b having substantially vertical sidewalls can be formed, and the lateral dimension of the protrusions 8a and 8b substantially matches the lateral dimension of the remaining portion of the resist film 5. Therefore, dry etching is now an indispensable technique in fine processing of semiconductors.

By the way, in recent years, as the miniaturization technology of semiconductor devices has progressed, in the patterning process including the photolithography process and the dry etching process, a dimensional conversion difference (CD gain (CD gain ( Critical Dimension
onGain) or CD loss (CriticalDim)
enionLoss)) is a problem. Since the resist film is a workpiece in the photolithography process, the dimension conversion difference is the dimension difference between the reticle pattern and the resist film pattern. The dimensional conversion difference in dry etching is the dimensional difference between the pattern of the resist film and the pattern of the workpiece after dry etching, and specifically, the remaining portion of the resist film and the convex portion formed on the workpiece. Is the lateral dimension difference from the lower end of the. The main factors that cause such a dimensional conversion difference are as follows: 1) Photolithography process: thermal expansion / expansion of the resist material for a pattern during post-baking, and resolution due to a focus shift during exposure. Difference 2) Dry etching process: Side etching progresses due to an increase in the size of the lower end of the convex portion caused by an excessive amount of deposits on the sidewall of the convex portion during etching, and an excessive amount of the adhered portion on the sidewall of the convex portion. There is a decrease in the size of the lower end of the convex portion caused by the above.

First, the dimensional conversion difference in dry etching will be described. For example, the conventional RIE (Reac
It is known that, in the etching of a polysilicon film by TIVE ION ETCHING, a dimensional conversion difference is likely to occur particularly when HBr gas is used. In particular, FIG.
Among the convex portions 8 shown in (a), the isolated convex portion 8a is a dense convex portion 8a.
The difference in dimensional conversion is larger than that in b. For example, gate length 0.5
At the time of patterning the polysilicon film corresponding to about μm, in the isolated convex portion 8a, as shown in FIG. 12B, the width W2 of the lower end portion of the convex portion 8a is increased relative to the width W1 of the remaining portion of the resist film. A large amount becomes about 0.05 μm, and the resist film 5 is formed on the dense convex portion 8b as shown in FIG.
The dimensional increase amount of the width W2 of the lower end portion of the convex portion 8b with respect to the width W1 of the remaining portion tends to be about 0.00 μm (that is, smaller than 0.005 μm). Generally, in one semiconductor device, a memory cell array having densely packed transistors and a peripheral circuit having isolated transistors are mixed. Therefore, the size conversion from a mask such as a gate is performed depending on the location of the transistor. The difference will vary. As a result, for example, the accuracy of the gate length of the MOSFET in the peripheral circuit is deteriorated, which causes a problem in the variation in the electrical characteristics of the device and the yield.

In order to prevent the occurrence of such a large dimensional conversion difference, a process not using HBr is also performed in the dry etching process. For example, a high vacuum etcher (ECR using electron cyclotron resonance, plasma source using helicon wave, etc.) has been introduced, and attempts have been made to reduce the size conversion difference.

On the other hand, in the photolithography technique, as one method of reducing the dimensional conversion difference, there is a shortening of the wavelength of the exposure light source and improvement of the mechanical accuracy of the optical system. At present, the mechanical accuracy has been improved to the extent that processing accuracy equivalent to the wavelength of the exposure light source can be obtained. For example 0.3
For a device with a 5 μm rule, the current standard processing accuracy is about ± 0.04 μm according to i-line exposure.

It is also known that the dimensional conversion difference in the photolithography process also varies depending on the type of pattern. Generally, the dimensional conversion difference in the isolated convex portion is larger than the dimensional conversion difference in the dense convex portion. For the dimension conversion difference that occurs in the photoresist process,
Up to now, the size conversion difference in the photolithography process has been taken into consideration in advance to reduce the size of the reticle pattern for photolithography, thereby eliminating the size conversion difference to some extent.

[0010]

However, the dry etching process and the photolithography process have the following problems.

In the dry etching process, even with a high vacuum etcher or the like, in reality, the dimensional change difference between the isolated convex portions becomes large, and the dimensional conversion difference between the isolated convex portions and the dense convex portions varies. With the current technology, it is difficult to eliminate such variation in dimensional conversion difference. With further miniaturization in the future, it is expected that the variation in the dimensional conversion difference will be one of the main causes of lowering the yield, but as described above, not only in the conventional RIE type etcher but also in the high vacuum etcher. It was very difficult to suppress the variation in dimensional conversion difference.

In order to obtain desired characteristics of the transistor, it is expected that it will be important in the future to freely control the cross-sectional shape of the convex portion formed by etching, such as the gate electrode, but it is formed by dry etching. It was extremely difficult to control the cross-sectional shape of the workpiece.

On the other hand, in the photolithography process, the shortening of the wavelength of the exposure light is approaching its limit, and the mechanical accuracy such as the accuracy of the lens and the positioning accuracy of the parts are approaching their limits. Therefore, it is currently difficult to significantly improve the processing accuracy. In addition, even if the dimensional conversion difference can be reduced by reducing the reticle pattern or the like as described above, the dimensional conversion difference varies among wafers even in the photolithography process. Although it is recognized that the variation in the dimensional conversion difference occurs, the variation in the dimensional conversion difference between the wafers in the photolithography technology is largely due to mechanical restrictions, and it is difficult to eliminate it fundamentally. Is. On the other hand, with the miniaturization of the device size, the variation in the dimensional conversion difference, which has not been a problem in the past, has become a problem.

The present invention has been made in view of the above points, and an object thereof is to elucidate a mechanism in which variations in dimensional conversion difference occur in the dry etching process as described above, and pay attention to the mechanism. and to provide a dry etching how capable of controlling the cross-sectional shape of the workpiece formed by the variations in the etching of the pattern shift in the dry etching process.

[0015]

[Means for Solving the Problems] (Clarification of Mechanism of Dimensional Change Difference) First, the mechanism of dimensional change difference generation clarified in the course of carrying out the invention will be described.

Generally, in the course of dry etching, an etching product is generated due to a reaction between a gas turned into plasma and a decomposed product of an etched portion. And
By adhering the etching products to the side portions of the concave portions and appropriately preventing the etching of the side portions from proceeding, proper anisotropic etching is performed. However, in particular, in a portion where the respective convex portions of the etched portion are isolated from each other, the phenomenon that the lower end portion of the convex portion becomes wider than the width of the remaining portion of the etching mask is likely to occur. This is because the distance between each convex portion, that is, the width of the concave portion is large, so that the amount of etching products generated in the concave portions is large, and an excessively large amount of etching products adheres to the side wall, resulting in an excessively disturbing etching effect. Conceivable.
Regarding the mechanism of such variation in the dimensional conversion difference, the points elucidated in the process of the present invention are shown in FIG.
2 (a) to (c) will be described.

As shown in FIG. 12A, generally, in the recess 9, the active species 1 are attached to the polysilicon film 4 which is the portion to be etched, the ions 2 are incident, and the reaction is caused by the kinetic energy. Etching is promoted and progresses. However, the adhesion amount of the etching product 3 generated by etching to the side wall of the convex portion 8 is different between the isolated convex portion 8a and the dense convex portion 8b. That is, since the widths of the isolated concave portions 9a on both sides of the isolated convex portion 8a are large, the area of the region to be etched is also large, and the amount of the etching product 3 attached to the sidewall of the isolated convex portion 8a is large. As a result, the film thickness of the deposit that protects the side wall becomes large, and the effect of disturbing the lateral etching becomes large. Therefore, in the isolated convex portion 8a, as shown in FIG. 12B, the width W2 of the lower end portion of the isolated convex portion 8a is larger than the dimension of the remaining portion of the resist film 5, that is, the width W1 of the upper end portion of the isolated convex portion 8a. Also grows. On the other hand, since the width of the dense concave portions 9b between the dense convex portions 8b is narrow, the area of the region to be etched is small, and the amount of etching products attached to the side wall of each dense convex portion 8b is small. as a result,
The effect of disturbing the etching effect in the side wall direction is reduced. Therefore, as shown in FIG. 12C, the width W1 of the lower end portion of the dense convex portion 8b is hardly larger than the dimension W1 of the upper end portion. In this way, the isolated convex portion 8a
The dimensional conversion difference is larger than the dimensional conversion difference of the dense convex portions 8b.

It is presumed that due to the above mechanism, variations in dimensional conversion difference occur in devices such as transistors arranged in one chip.

(Means taken by each claim) Focusing on the mechanism of occurrence of the variation in the dimensional change difference, the present invention controls the sectional shape of the convex portion to reduce the dimensional conversion difference in the isolated convex portion. However, in order to eliminate the variation in the dimensional conversion difference between the convex portions, the measures described in claims 1 to 3 are taken.

According to the dry etching method of the present invention, as described in claim 1, a semiconductor wafer in which a portion to be etched is covered with an etching mask having a pattern of remaining portions and openings is placed in a reaction chamber. , A step of introducing a gas into the reaction chamber, and dry etching is performed using the gas, a convex portion is formed below the remaining portion of the etching mask in the etched portion, and a concave portion is formed below the opening portion of the etching mask. And a step of forming each. Then, by adjusting the pressure and flow rate of the gas in the reaction chamber, the discharge rate of the etching product generated by the dry etching to the outside of the concave portion and the adhesion rate to the side wall of the convex portion are controlled to control the convex portion. This is a method of controlling a dimension conversion difference which is a lateral dimension difference between the lower end of the portion and the remaining portion of the etching mask.

In this method, the portion to be etched is
Made of single crystal silicon or polysilicon, the above reaction
The pressure of the gas in the chamber is 100 mTorr or more,
The gas flow rate in the reaction chamber is 100 sccm or more.
Yes, the above gases are hydrogen bromide gas, hydrogen bromide gas and chlorine
Mixed gas with gas, and hydrogen bromide gas and hydrogen chloride gas
Any one of the mixed gas of
The difference is 0.04 μm or less.

By controlling the gas pressure and the gas flow rate as in the first aspect, the dimensional conversion difference of the etched portion can be controlled. Although this mechanism has not been clarified, it is presumed to be due to the following actions.

When the gas pressure is increased, FIG. 1 (a)
The mean free path λ of the active species 1 and the etching product 3 shown in (where λ is mainly determined by the etching pressure p).
Is sufficiently smaller than the reaction chamber dimension d (or wafer size) (for example, P = 100 mTorr, d =
20 cm), the flow of gas becomes a region called viscous flow. At this time, the neutral gas acts as a resistance when the etching product tries to adhere to the side wall of the convex portion.
Further, when the gas pressure and the gas flow rate increase, the recess 9
A strong turbulence is generated in the side wall, and the effect of preventing the etching products from adhering to the side wall becomes stronger. When the gas pressure and flow rate increase due to the above two actions, the rate of adhesion of etching products to the sidewalls of the protrusions decreases.

Further, as the gas pressure increases, the weight of the gas per unit volume increases (viscosity increases), so that the transport efficiency of the etching products increases and the action of discharging the etching products to the upper space is achieved. growing.
That is, the three particles of the etching product, which contribute to the protection of the sidewall of the convex portion, are drawn into the bulk gas flow rate and discharged. In addition, in the reaction chamber, a negative pressure is generated in the space above the bottom of the recess where there is almost no flow and in the static pressure state, and near the side wall, but negative pressure and positive pressure occur when the gas flow rate increases. Since the pressure difference between the two becomes large, discharge of etching products is promoted. That is, when the pressure or flow rate of the gas increases, the discharge ratio of the etching product 3 to the upper space increases due to the above-described effects and the effects due to the generation of strong turbulence.

Further, as a reverse action of the above, the etching product 3 is reduced by reducing the gas pressure or flow rate.
The adhesion ratio of the to the side wall of the convex portion increases.

Therefore, by controlling the pressure and flow rate of the gas, any one of the above-mentioned actions becomes the main and the actions are related to each other, and the discharge ratio of the etching product to the upper space and to the side wall. It becomes possible to control the adhesion ratio. Therefore, the cross-sectional shape of the convex portion is easily controlled, and the dimensional conversion difference of the isolated convex portion is also reduced.

According to a second aspect of the present invention, in the dry etching method according to the first aspect, at least one of the protrusions in the etched portion has a lower end having a lateral dimension of 0.4 μm or less, It is possible to form an isolated convex portion in which the lateral dimension of the concave portions on both sides is 1 μm or more.

By this method, the shape of the isolated convex portion having a large dimensional conversion difference is improved.

According to a third aspect of the present invention, in the dry etching method according to the first aspect, at least one of the protrusions in the etched portion has a lateral dimension of 1 μm or more on both sides. As the isolated convex portion, the other pluralities of the convex portions in the etched portion can be dense convex portions in which the lateral dimension of the concave portions between the convex portions is 1 μm or less.

By this method, the following effects are obtained, and the variation in the dimensional change difference between the isolated convex portions and the dense convex portions in the etched portion is suppressed. That is, when the gas flow velocity is gradually increased, as shown in FIG.
The discharge rate of the etching product 3 shown in 1 also increases, and the residence time of the etching product 3 on the etching surface is shortened. However, the effect of shortening the residence time depends on the etching pattern. In the isolated recesses 9a, the etching products 3 are easily influenced by the flow of gas, and the effect of shortening the stay time is large, whereas in the dense recesses 9b, the recesses 9b have a narrow and recessed shape. In addition, the residence time of the etching product 3 is not easily influenced by the gas flow. For the above reason, the dimension conversion difference of the dense convex portions due to the side wall protection effect of the etching product 3 hardly changes, whereas the isolated convex portions decrease the dimension conversion difference as the gas flow increases. Become. Therefore, variations in dimensional conversion difference are reduced.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) Next, a first embodiment of the present invention will be described. Figure 2
FIG. 3 is a cross-sectional view schematically showing the configuration of a medium vacuum region magnetron RIE device according to the first embodiment of the present invention.
In FIG. 2, the relationship between the reference numerals and the member names is as follows. 21 is a reaction chamber, 22 is an electromagnetic coil,
10 is a sample such as a semiconductor wafer for LSI, 11 is a high frequency power source (for example, 13.56 MHz industrial power source), 12 is a coupling capacitor, 13 is a cathode electrode, 14 is an anode electrode, 15 is a turbo molecular pump, 16 is a rotary pump. , 17 are mass flow controllers, and 20 is a plasma generation region. The anode electrode 14 is grounded, and the gas in the chamber 1 is exhausted from the exhaust port by the turbo molecular pump 15 and the rotary pump 16. In addition, the mass flow controller 17 controls the chamber 21
It is designed to adjust the flow rate of the gas that flows in.

FIG. 3 is a sectional view of a portion to be etched of a semiconductor wafer, in which a polysilicon film 4 which is the portion to be etched is deposited on a silicon substrate 6 with a gate oxide film 7 interposed therebetween. The convex portion 8 which is the gate electrode is formed from the silicon film. At that time, the isolated convex portion 8a and the dense convex portion 8b are formed depending on the location of the transistor.

When performing dry etching, as shown in FIG. 2, the chamber radius is about 20.
The gas is filled in the chamber 21 in a viscous region where the pressure is 100 cm and the gas pressure is 100 mTorr. Thereafter, the electric power (215 W) output from the high frequency power supply 11 is transmitted to the cathode electrode 13 via the coupling capacitor 12. Due to the transmitted electric power and the magnetic field generated by the electromagnetic coil 22, the HBr gas, C introduced into the chamber 21
The etching gas composed of 12 gas is ionized to form the plasma region 20. Then, the Br radicals, which are active species dissociated from the HBr gas, and the Cl radicals dissociated from Cl2, etch polysilicon under the ion assist. SiB produced by etching
rx (x = 1, 2, 3, 4) adheres to the etching sidewall and prevents side etching.

According to the method of this embodiment, as the total flow rate of the HBr gas and the Cl2 gas increases, the isolated convex portion 8a increases.
The difference in the adhesion amount of the etching product to the side wall between the dense convex portion 8b and the dense convex portion 8b decreases. FIG. 4A shows a gas pressure of 100 mT.
The change of the dimension conversion difference with respect to the total gas flow rate under orr is shown. Under a gas pressure of 100 mTorr,
If the total gas flow rate is 100 sccm or more, the variation in dimensional conversion difference can be reduced to 0.04 μm on average. As a result, compared to the conventional method in which the gas flow rate is about 50 sccm, the variation in dimensional conversion difference can be reduced by half, and the device yield can be improved. In addition, FIG.
Shows the change in dimensional conversion difference with respect to the total gas flow rate under a gas pressure of 50 mTorr. Gas pressure is 50
Even under mTorr, it is possible to reduce the variation in the dimensional conversion difference as shown in FIG.

Further, it should be noted that the dimensional conversion difference of the isolated pattern is in a relationship almost inversely proportional to the total gas flow rate. That is, by controlling the gas flow rate, it is possible to control only the dimension conversion difference of the isolated convex portion. If the size of the remaining portion becomes large during patterning of the photoresist film, it is possible to control the gas flow rate and keep the finished size within the standard.

Further, during etching, the cross-sectional shape of each of the protrusions 8a and 8b can be freely controlled by changing the gas flow rate with time to change the amount of adhesion to the side wall.

In this embodiment, as shown in FIG. 3, only the isolated convex portion 8a has a trapezoidal shape. In this case, the gas flow rate is 75 sccm to 150 sccm during etching.
It has been increased to cm.

(Second Embodiment) Next, a second embodiment will be described.

FIG. 5 is a sectional view schematically showing the structure of a medium vacuum RIE apparatus according to the second embodiment of the present invention.
In FIG. 5, the relationship between the reference numerals and the member names is as follows. 21 is a chamber; 22 is a semiconductor wafer for LSI;
1 is a high frequency power supply (for example, 13.56 MHz industrial power supply), 12 is a coupling capacitor, 13 is a cathode electrode, 14 is an anode electrode, 15 is a turbo molecular pump,
Reference numeral 16 is a rotary pump, 17 is a mass flow controller, and 20 is a plasma generation region. The anode electrode 14 is grounded, and the gas in the chamber 21 is exhausted from the exhaust port by the turbo molecular pump 15 and the rotary pump 16. Further, the mass flow controller 17 adjusts the flow rate of gas flowing into the chamber 21. Unlike the medium vacuum region magnetron RIE device according to the first embodiment, the RIE device according to the present embodiment has no electromagnetic coil attached to the side of the chamber 21.

When performing dry etching, as shown in FIG. 5, the chamber size (chamber radius) is about 18 cm,
In the viscous region where the gas pressure region is 180 mTorr,
The chamber 21 is filled with gas. After that, high frequency power 11
The electric power (200 W) output from is transmitted to the cathode electrode 13 via the coupling capacitor 12. Due to the transmitted power, the H introduced in the chamber 21
The etching gas composed of Br gas, HCl gas, and O 2 gas is ionized to form the plasma region 20. And H
The action of the Br radical, which is an active species dissociated from Br, and the Cl radical, which is dissociated from HCl, to etch polysilicon under the ion assist is basically the same as the action in the first embodiment.

FIG. 6 shows the relationship between the total gas flow rate and the dimensional conversion difference in this embodiment.
It is mTorr. In the present embodiment, as shown in FIG. 6, when the total gas flow rate is 100 sccm or more under a gas pressure of 180 mTorr, the variation in dimensional conversion difference can be reduced to 0.04 μm on average. As a result, it is possible to greatly reduce the variation in the dimensional conversion difference as compared with the conventional method in which the gas flow rate is about 45 sccm.
The device yield can be improved.

Further, as in the case of the first embodiment,
Also in the second embodiment, since the total gas flow rate and the size conversion difference of the isolated convex portion are in a nearly inversely proportional relationship,
By controlling the gas flow rate using this relationship, it is possible to control only the dimension conversion difference of the isolated convex portion.
In addition, the cross-sectional shape of the convex portion can be freely controlled by changing the gas flow rate during etching to change the amount of the etching product attached to the side wall.

(Summary of First and Second Embodiments and Data of Additional Experiments) Next, the results of experiments conducted to obtain data to be added to the data in the first and second embodiments, and A summary of the embodiments will be described. The experiment here was performed using the medium vacuum region magnetron RIE apparatus similar to that of the first embodiment.

7 (a) to 7 (c), the gas pressure is constant at 100 mTorr and the gas flow rate is 30, 75, 1.
3 is an SEM photograph showing the cross-sectional shape of an isolated convex portion when changed to 50 sccm. Moreover, FIG.
(C) is an SEM photograph showing the cross-sectional shape of the dense convex portions when the gas pressure is set to a constant value of 100 mTorr and the gas flow rate is set to 30, 75, and 150 sccm. Figure 7
As shown in FIGS. 7A to 7C, the gas flow rate is 50
When it is sccm, the size of the lower end portion of the isolated convex portion is larger than the size of the upper end portion, and the dimensional conversion difference is large. On the other hand, when the gas flow rate is 75 sccm, the dimensional conversion difference is considerably small, but it is not zero. And the gas flow rate is 1
At 50 sccm, the size of the lower end of the isolated protrusion is almost equal to the size of the upper end, and the size conversion difference is almost zero.
On the other hand, as shown in FIGS. 8 (a) to 8 (c), the size of the lower end of the dense convex portion is almost equal to the size of the upper end regardless of the gas pressure, and the size conversion difference Is almost 0 regardless of the change in gas flow rate.

9 (a) and 9 (b), the gas flow rate is set to a constant value of 75 sccm, and the gas pressure is set to 20,100.
It is a SEM photograph showing the cross-sectional shape of an isolated convex part when changing to mTorr. As shown in FIGS. 9A and 9B, when the gas pressure is 20 mTorr, the size of the lower end of the isolated convex portion is larger than the size of the upper end, and the size conversion difference is large. On the other hand, the gas pressure is 100 mT
At orrr, the dimensional conversion difference is considerably small.

FIG. 10 is a diagram showing the gas pressure dependence of the dimensional conversion difference of the isolated convex portion under the conditions of the gas flow rate of 75 sccm and the gas flow rate of 150 sccm. As shown in the figure, when the gas flow rate is 75 sccm, by extrapolating this data, the gas pressure is about 13
When it is 0 mTorr or more, the dimensional conversion difference can be suppressed to 0.04 μm or less. When the gas flow rate is 150 sccm, the dimensional conversion difference can be suppressed to 0.04 μm or less when the gas pressure is about 90 mTorr or more.

FIG. 11 is a map showing the relationship between the gas flow rate and the gas pressure in the dry etching method of the present invention and the conventional dry etching method.

The initial dry etching technique has been carried out under the condition of the region ReA shown in the figure, that is, under a relatively low vacuum (high pressure) and under a relatively small gas flow rate. On the other hand, recently, the condition has been shifted to a relatively small gas flow rate under the condition of the region ReB shown in the figure, that is, high vacuum (low pressure). For example, in an ECR type which is a high vacuum etcher, an attempt has been made to change the exhaust rate to control the amount of active species deposited on the etching sidewall (for example, Japanese Patent Laid-Open No. 5-2).
59119, 5-267227, 5-267249, 5
-275376). However, although it is considered that the gas flow is not in the viscous region, the size conversion difference in the isolated convex portion has not been eliminated yet, and it is difficult to reduce the variation in the size conversion difference.

On the other hand, according to the present invention, the condition of the region ReC shown in the figure, that is, a relatively low vacuum (high pressure) and a relatively large gas flow rate is used. By performing the dry etching under such a condition, it is possible to almost eliminate the dimensional conversion difference even in the isolated convex portion as described above.

From experience, the range of the gas pressure P for surely producing the effect of the present invention is 5 mTorr or more in a chamber having a diameter d of 30 cm. That is, the pressure P
It is preferable that the product P · d of the chamber diameter d and the chamber diameter d be in the following range.

P · d ≧ 5 (mTorr) × 30 (cm) = 1.5 × 10 −3 (Torr · m) = 1.5 × 10 −3 × 1.33 Pa · m = 1.5 × 10− 3 x 1.33 (Kg / m) sec2
M = 0.2 Kg / sec2 Further, the material of the etched portion which can be patterned by the present invention is Si, poly-Si (including doped and undoped), amorphous Si, GaAs, Ga.
N, AlGaAs, InGaAs, AlP, AlAs,
Semiconductor materials such as InP, InAs, InSb, Al, C
u, Cu alloy, Al alloy, W, T, Co, Ta, Mo,
Metallic materials such as Nb, WSix, TiSix, CoSix
Etc. are silicides.

Further, focusing on the gas flow rate dependence of the dimensional conversion difference shown in the data in each of the above-described embodiments, by controlling the gas flow rate, the side wall protection effect of the isolated convex portion is particularly controlled, and the isolated convex portion of the isolated convex portion is controlled. The cross-sectional shape can be controlled freely.

[0053]

According to the first aspect of the present invention, when dry etching is performed to form a pattern of protrusions and depressions on an etched portion of a semiconductor wafer, the depressions of etching products are adjusted by adjusting the gas pressure and flow rate. Since the dimensional conversion difference is controlled by controlling the discharge rate to the outside and the adhesion rate to the side wall of the convex portion, it is easy to control the sectional shape of the convex portion and reduce the dimensional conversion difference of the isolated convex portion. Can be achieved.

According to the second aspect , in the first aspect, at least one of the protrusions in the etched portion is an isolated protrusion, so that the shape of the isolated protrusion having a large dimensional conversion difference is improved. become.

According to a third aspect of the present invention, in the first aspect, at least one of the convex portions in the etched portion is an isolated convex portion, and the other plural portions are dense convex portions. Therefore, the isolated convex portion in the etched portion is formed. parts and Ru can be suppressed variations in the dimensional change differential between the dense protrusions.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a cross-sectional shape of a silicon substrate, an isolated convex portion, and a dense convex portion when performing etching by a dry etching method of the present invention.

FIG. 2 is a cross-sectional view schematically showing the structure of the dry etching apparatus in the first embodiment.

FIG. 3 is a cross-sectional view of a portion to be etched in the first embodiment.

FIG. 4 is a diagram showing data of gas flow rate dependence of a dimensional conversion difference obtained according to the first embodiment.

FIG. 5 is a sectional view schematically showing the structure of a dry etching apparatus according to a second embodiment.

FIG. 6 is a diagram showing data of gas flow rate dependence of a dimensional conversion difference obtained according to the second embodiment.

FIG. 7: Gas pressure of 100 mTorr with additional experiments,
It is a SEM photograph figure which shows the cross-sectional shape of an isolated convex part at the time of gas flow of 30,75,150 sccm, respectively.

FIG. 8: Gas pressure of 100 mTorr with additional experiments,
It is a SEM photograph figure which shows the cross-sectional shape of a dense convex part, respectively when gas flow rates are 30, 75, and 150 sccm.

FIG. 9: Gas pressure of 20,100 mTo according to additional experiment
It is a SEM photograph figure which shows the cross-sectional shape of an isolated convex part at the time of rr and gas flow rate of 75 sccm, respectively.

FIG. 10 is a diagram showing data on the gas pressure dependence of the dimensional conversion difference obtained by an additional experiment.

FIG. 11 is a map diagram showing the difference in gas pressure and flow rate regions between the dry etching of the present invention and the conventional dry etching.

FIG. 12 is a cross-sectional view showing a cross-sectional shape of a silicon substrate, an isolated convex portion, and a dense convex portion when performing etching by a conventional dry etching method.

[Explanation of symbols]

1 active species 2 ion 3 Etching products 4 Polysilicon film 5 Resist film (etching mask) 6 Silicon substrate 7 Silicon oxide film 8 convex parts 8a isolated protrusion 8b dense convex part 9 recesses 9a isolated recess 9b Dense recess 10 samples 11 high frequency power supply 12 coupling capacitors 13 cathode electrode 14 anode electrodes 15 turbo molecular pump 16 rotary pump 17 mass flow controller 20 plasma regions 21 chambers (reaction chamber) 22 electromagnetic coil

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065

Claims (3)

(57) [Claims] 1. A step of installing a semiconductor wafer in which a portion to be etched is covered with an etching mask having a pattern of a remaining portion and an opening in a reaction chamber and introducing a gas into the reaction chamber, and using the gas. Dry etching is performed to form a convex portion below the remaining portion of the etching mask in the etched portion, and a concave portion below the opening portion of the etching mask. By adjusting the flow rate,
By controlling the discharge rate of the etching product generated by the dry etching to the outside of the concave portion and the adhesion rate to the side wall of the convex portion, between the lower end portion of the convex portion and the remaining portion of the etching mask. This is a dry etching method that keeps the lateral dimension difference within the specified range.
The etched portion is made of single crystal silicon or poly silicon.
Made down, the pressure of the gas in the reaction chamber is more than 100mTorr
In, and the flow rate of the gas in the reaction chamber 100sccm more
Yes, the above gases are hydrogen bromide gas, hydrogen bromide gas and chlorine gas.
Gas mixture of hydrogen and hydrogen bromide gas and hydrogen chloride gas
A dry etching method in which any one of the gases is used and the dimensional conversion difference is 0.04 μm or less . 2. The dry etching method according to claim 1, wherein at least one of the projections in the etched portion has a lateral dimension of 0.4 μm or less at a lower end and lateral dimensions of concave portions on both sides. The dry etching method is characterized in that each is an isolated convex portion having a size of 1 μm or more. 3. The dry etching method according to claim 1, wherein at least one of the convex portions in the etched portion is an isolated convex portion in which the lateral dimension of the concave portions on both sides is 1 μm or more. The dry etching method is characterized in that the other plurality of the protrusions in the etched portion are dense protrusions in which the lateral dimension of the recesses between the protrusions is 1 μm or less.