CN1053764C - Beam caused electrographic technology - Google Patents

Abstract

The present invention relates to a beam caused electrographic technology for the surface of semiconductor chip silicon dioxides. The beam caused electrographic technology comprises the following steps: selective bombardment is carried out at the surface of silicon dioxides by one or two particle beams, such as ion beams, electron beams, etc. so that the etching characteristics of the surface of the silicon dioxides are obviously changed; the surface of the silicon dioxides, which is chosen to be bombed, is coated with a catalytic mixture layer; the catalytic mixture layer and the silicon dioxides are corroded in mixed gases of hydrogen fluoride solutions blistered by nitrogen at a certain temperature. The corrosion speed ration of two areas at the surface of the silicon dioxides is 1 to 100, and the surface is chosen to be bombed; electrographic resolution is in submicron order, positive patterns and negative patterns which can be changed are clear and complete, and reliability is high.

Description

Beam induced corrosion method

The invention relates to the field of semiconductor integrated circuit and device manufacture, in particular to SiO serving as a dielectric film in integrated circuit manufacture₂The beam-induced ablation method of the patterning technique of (1).

With the continuous development of microelectronic technology, semiconductor integrated circuits have entered the VLSI era, and due to the high performance and reliability of VLSI, it has become the foundation and core of the electronic industry, and the process technology has become the key to the development of large-scale integrated circuits, wherein the development of fine patterning technology directly leads to the miniaturization and high performance of devices, so that the chip area can be greatly reduced, and high integration level can be realized.

The rapid development in the integrated circuit manufacturing industry has brought circuit feature sizes into the submicron range, and the size limitations and inherent disadvantages of conventional lithography have forced the search for other effective lithographic approaches, known as ion beam exposure, electron beam exposure, and soft X-ray exposure. However, although these lithographic techniques have been satisfactory for the fabrication of submicron-sized patterns, they have not come out of the inherently cumbersome series of process patterns of exposure, development, hardening, etching, etc., and thus, the defects and deviations introduced by the respective steps are inevitable, and thus, their application is still limited. In the 80 s, it was reported that N was used⁺、He⁺、Ar⁺、H⁺SiO implantation₂After the thin layer surface, the SiO is etched (wet process) with 10% HF aqueous solution₂The corrosion increasing effect is obtained, the corrosion rate ratio of the implanted area (ion bombardment area) to the non-implanted area is 5 times, and the ion dose is 72 multiplied by 10¹⁶cm^-2Energy of 30KeV to 100KeV, line width resolution of 0.05 μm [ J.R.A.C.Leaver, P.J.Heard, A.F.Evason and H.Ahmed, appl.phys.Lett49/11(1986)](ii) a Also, the maximum corrosion rate ratio of the two regions has been made 8 times by the same method. Although the corrosion increasing effect is realized, the corrosion rate ratio cannot be obtained, so that the practicability is not high, and the inherent defects of wet corrosion cannot be overcome;it has also been reported that ion implantation is followed by SiO₂Surface etch resist [ T.Shiokawa, I.Migamoto, P.H.Kim, Y.Ochiai, A.Masuyama, K.Toyoda and S.Namba, Jph, J.appl.Pbys.24/11(1985)]They are in Si or SiO₂The metal ions are obtained by the upper injection, and the metal ions are difficult to obtain and still continue to be etched by a wet method, so that the metal ions are not put into practical use. In addition, on a chipMany of the lead holes have different forms of SiO when used therein₂Present, e.g. P-SiO₂、B-SiO₂Etc., which have widely different corrosion rates, thereby affecting the patterns to be made. Furthermore, it is impossible to recover the erosion by changing it in one direction only with one beam, i.e. it is unidirectional and not reversible. To overcome the above disadvantages, the inventors implanted ions with SiO₂Or the Si surface is researched and explored, the ion beam implantation corrosion resistance effect is discovered in 1982, the electron beam corrosion resistance technology is explored in 1985, the phase relation among the ion beam, the electron beam and the plasma beam is researched, and the invention is finally completed through years of experiments and practices.

The invention aims to: provides a semiconductor chip SiO₂A beam-induced corrosion method for processing surface patterns. Namely, a full dry beam induced etching method without a mask and a photoresist. The method can avoid the defects of photoetching and wet etching, and improve SiO₂The etching rate ratio of the surface particle beam bombardment area to the non-bombardment area is 100 times, so that the process is simplified, the yield of fine pattern processing on the surface of the semiconductor chip is improved, a large amount of chemical reagents are saved, the pollution is reduced, and the submicron fine pattern can be manufactured.

The purpose of the invention is realized as follows: the provided beam induced corrosion method comprises the following steps:

the first step is as follows: by one or two particle beams, e.g. ion, electron, plasma, on SiO₂Surface is selectively bombarded to make SiO₂The surface energy is obviously changed, so that the corrosion rate ratio of a bombardment area to a non-bombardment area after the subsequent corrosion in the mixed gas of bubbling HF solution by nitrogen is obviously increased, and the ion of the used ion beam is N⁺、H⁺、O⁺、Ar⁺The ion implantation dose is 5 × 10¹⁵cm^-2～1×10¹⁶cm^-2The energy is 1 OKeV-100 KeV, the voltage of two electrodes used in electron beam bombardment is 1800V-2000V, and the bombardment time is more than 5 minutes; the energy used for the bombardment of the plasma beam is 20W-40W, and the bombardment time is 20 seconds-90 seconds;

the second step is that: coating a layer of a catalyst composition having a thickness of 200A to 6000A on the surface selectively bombarded by the particle beam, the catalyst composition comprising:

… … … … … 100ml of mono-cyclohexanone

Michler's ketone … … … … … 1g

Cinnamic acid … … … … … 1g

… … 2g of polyvinyl alcohol cinnamate; or

… … … … … 100ml of di-cyclohexanone and … … … … … ml of cyclohexanone

2-hydroxy-5-nitroacenaphthylene … … 1.5.5 g

… … … … … 3g of polyester

Diaminodiphenyl ether … … … 0.5.5 g

The third step: on the sample coated with the catalyst composition film, under the room temperature to 190 ℃, the mixed gas of a nitrogen bubbling HF solution is used for corrosion, and the corrosion rate is more than 1000 a/min;

the fourth step: removing the catalyst to obtain the required pattern.

The invention has good effect and SiO₂The corrosion rate of the catalyst is changed with the difference of the catalyst dosage and the catalyst type, the range is wide, the corrosion rate can be changed from 1000A/min to zero, and the corrosion rate can be controlled; when the ion implantation dosage reaches 1 × 10¹⁶cm^-2When in use, the corrosion rate ratio (bombardment area and non-bombardment area) reaches 1: 100; the etching resolution is submicron; the positive and negative of the etched pattern can be changed, and the pattern is clear and complete; the process is simplified; the reliability is high.

The present invention will be described in detail below with reference to the accompanying drawings and examples.

FIG. 1 shows ion implantation dose vs. SiO₂The relationship of the corrosion rate;

FIG. 2 shows different ion implantations with a constant energy, ion implantation dose and SiO₂The relationship of the corrosion rate;

FIG. 3 shows the implant ion energy and SiO₂The relationship of the corrosion rate;

FIG. 4 shows the ion dose implanted and SiO for different catalysts₂Corrosion rate ratio;

FIG. 5 shows the bombardment time and SiO for different beams at a constant voltage and current₂The relationship of the corrosion rate;

FIG. 6 shows the voltage at the two poles and SiO when the current is constant and the bombardment time is constant₂The relationship of the corrosion rate;

FIG. 7 shows voltage vs. SiO₂Corrosion rate ratio;

FIG. 8 is a graph showing the relationship between bombardment time and the difference in etch rate between two zones;

FIG. 9 shows a reversible schematic of beam induced erosion;

FIG. 10 shows the relationship between the substrate temperature and the amount of HF adsorbed on the catalyst, for different catalysts;

FIG. 11 shows the relationship between the thickness of a catalyst adhesive film and the amount of HF adsorbed;

FIG. 12 shows a flow chart of an ion implantation resist fluorine process;

FIG. 13 shows a photomicrograph of a 5 μm line width pattern etched using a stencil mask ion implantation resist process;

FIG. 14 shows a photomicrograph of a 15 μm line width pattern etched using a stencil mask and electron beam bombardment etching process;

FIG. 15 is a flow chart showing an ion resist disappearance process;

fig. 16 shows a scanning electron micrograph of a sub-micron line width pattern etched using the resist-loss process flow.

The beam-induced degradation method adopts particle beams (ion beams, electron beams and plasma beams) to treat SiO₂The surface is bombarded, causing corrosion inhibition (IBEE, IonBeam Enhanced Et)chip) opposite etch resistance (IBRE), SiO on semiconductor Si substrate₂The etching rate of the implanted or bombarded region of the film is greatly reduced, even not etched at all, so that a negative pattern can be etched. E.g. ion implantation, on oxidised silicon wafers, i.e. SiO₂N for membranes⁺、Ar⁺、O⁺、H⁺Plasma is selectively injected, then a catalyst layer of 200-6000 is coated, the wafer is put into a dry etching system, the mixed gas of HF solution carried by nitrogen is etched for a plurality of minutes at the temperature of 80-100 ℃, and the catalyst is removed after etching to obtain the following results:

(1) as shown in FIG. 1, SiO when the implanted ion dose is low₂The etching rate is reduced with the increase of the ion dose, when the ion dose reaches 1X 10¹⁶cm^-2When is SiO₂The corrosion rate is not changed and tends to be zero, namely the critical dosage is reached, and the purpose of corrosion resistance is achieved;

(2) as shown in fig. 2, the corrosion resistance increases as the atomic weight of the implanted ions increases. In FIG. 2, the curve a is the implant H⁺(ii) a Curve B is injection B⁺(ii) a c curve is injecting N⁺D curve is implant P⁺The ion energy was 60 KeV.

(3) As shown in fig. 3, the implanted ion energyis coupled to SiO₂The effect of the corrosion rate is insignificant. N is a radical of⁺Is 10¹⁵cm^-2。

(4) As shown in fig. 4, the catalyst coating has an influence on the corrosion rate and the selective corrosion, and in fig. 4, there are two catalysts (a is the first catalyst and B is the second catalyst, as will be described later), it can be seen that the types of the catalysts have certain influences on the corrosion rate and the selective corrosion, the selective corrosion ratio has a very close relationship with the dose of implanted ions, when the dose reaches a certain value, the selective corrosion ratio is higher, and when the dose is increased, the selective corrosion ratio is not changed. When the same ratio is reached, the required dosage values are different, and the required dosage of the catalyst II is low.

With N⁺、H⁺、O⁺、Ar⁺The implantation energy of the ions directly affects the pattern quality, and the higher energy may not affect the selective etching ratioBut the lateral erosion is greatly reduced, so the energy used is 10KeV to 100KeV, and the dose is 5X 10¹⁵cm^-2～1×10¹⁶cm^-2The thickness of the catalyst coating is 200-2000A.

For another example, electron beam bombardment is performed by placing a sample on a plate with two electrodes of a high voltage power supply which are positively charged, and has the following results:

(1) as shown in FIG. 5, when the voltage and current are constant, the longer the bombardment time is, the SiO₂The smaller the erosion rate, the curves of electron beam bombardment and ion implantation at 0.2A current and 2000V are shown in the figure, which shows that the SiO gas is formed by the electron beam and ion beam bombardment for a certain time₂The corrosion rate is reduced and tends to be zero, thus achieving the purpose of corrosion resistance;

(2) as shown in FIG. 6, when the current is constant and the bombardment time of the electron beam is constant, the SiO changes with the voltage of the two poles₂The erosion rate decreases and the ion beam, the electron beam and the plasma beam are shown simultaneously in fig. 6. Wherein, the corrosion resistance tendency of the ion beam and the electron beam is the same, when the bipolar voltage reaches 2000V-3000V, SiO₂The corrosion rate is close to zero.

(3) As shown in FIG. 7, the magnitude of the bipolar voltage is plotted against the SiO₂The corrosion rate ratio has an influence, and SiO is generated when the voltage reaches 2000V₂The corrosion rate ratio is close to 1: 100;

(4) as shown in fig. 8, the bombardment time has an effect on the difference in the two-zone corrosion rate, which is nearly constant when the electron beam bombardment reaches more than 5 minutes.

The voltage of two electrodes is 1800V-2000V when the electron beam bombards, and the bombarding time is more than 5 minutes. The plasma is a partially ionized gas containing electrons, ions and various neutral radicals, and is used for treating SiO with plasma beam₂Bombardment tests, results likewise being SiO₂The reaction speed with HF is slow, and the corrosion resistance effect is achieved, but the difference between the former two is that no one can be found for SiO in any way no matter how the bombardment is carried out₂The condition where the corrosion rate tends to zero, the curve is flat as shown in FIG. 6.

Until now all pairs of Si with particle beamsO₂The surface modification is one kind of beam, and the combination of the two kinds of beam is not seen yet. In the present invention, two beams canbe used to bombard SiO₂The surface, and thus the first beam induced etch resistance, may be lost, referred to herein as the etch resistance loss effect. The plasma beam has obvious effect in the corrosion resistance disappearance effect, and when the plasma beam or the electron beam is used for bombardment at the position where the corrosion resistance effect is obtained for the ion implantation for the first time, the reaction speed can be restored to the level before the bombardment; when the first time is electron beam bombardment, the second time is plasma beam bombardment, the anti-corrosion disappearance effect can be achieved, the ion beam bombardment can not achieve the recovery purpose, the change of the corrosion rate obtained after the second particle beam action is not only related to the type of the particle beam, but also related to the order of the particle beam action, because of the anti-corrosion disappearance effect, a submicron-order pattern can be conveniently manufactured, but when the plasma beam is used for secondary bombardment, the bombardment energy and the dose are important, the anti-corrosion disappearance effect can be obtained without random bombardment, and the bombardment condition is vacuum degree4×10^-2The bombardment time is 10-20 seconds, and the bombardment power is more than 10-25W. The reaction is represented as follows:

SiF₄↑+H₂O

the reversibility of beam induced erosion is shown in figure 9.

The invention relates to a dielectric film SiO in integrated circuit manufacture₂In the method for forming a pattern of (1), wherein the etching step is also SiO₂The rate of reaction of the membrane with the aqueous HF gas is important. So-called SiO₂The reaction rate with HF gas is the reactant SiO₂The amount of thinning, in angstroms per minute,varies with time. It is difficult to perform the above-mentioned gas-solid reaction system without participation of a catalyst. I.e. influence of SiO₂The corrosion rate has two main factors, one is catalyst participation, and the other is SiO₂The surface energy changes, the participation of the catalyst is first mentioned here. When SiO is present₂After the surface is covered with a layer of catalyst film, a contact electric field is produced at the interface of the two, when the hydrogen fluoride containing water is contacted with the catalyst film, firstly the hydrogen fluoride is adsorbed on the surface of the catalyst film, thenDiffusion of post-reaction gas through the catalyst film to SiO₂And hydrogen fluoride is ionized with the interface of the catalyst membrane under the action of an interface contact electric field, so that the reaction is accelerated. Reaction product (H)₂O、SiF₄) Quickly diffuse from the interface to the outside of the catalyst membrane, making the reaction in an equilibrium state. The speed of the reaction speed has a close relation with the strength of an interface electric field, and the strength of the electric field is in close relation with the strength of SiO₂The contact potential difference between the surface and the catalyst film. That is, the reaction speed is increased when the charges on both sides are large and opposite to each other, depending on the amount and kind of charges accumulated on both sides of the interface when equilibrium is reached; otherwise, it is slow. SiO with catalyst coated on surface₂The reaction rate on the surface varies depending on the kind of the catalyst and the temperature, but the curve shape is similar and can be used similarly $V\left(T\right)=K{e}^{{(T-a)}^2\mathrm{\δ}}+b$ Where V is the reaction rate, T is the reaction temperature, a is the highest point of the reaction rate, and b, K, and δ are constants.

The catalyst used according to the invention requires HF and H₂The shape between O gas molecules and catalystUnstable chemical bonds are formed, which are associated with adsorbed hydrogen bonds, and the catalytic activity is higher only when the adsorption of the reactant molecules by the catalyst is of moderate strength, and in the moderate adsorption range, the weaker the adsorption strength, the more favorable the conversion to the product, the higher the catalytic activity. The catalyst functions to reduce the activation energy of the reaction, and also to increase the number of molecules activated by the reaction, thereby accelerating the reaction. The catalytic reaction can be summarized by the following reaction formulae, in which,the reaction of water is indispensable:

the effect with the catalyst can be written as:

(C represents a catalyst)

The catalyst used in the invention is a composite catalyst, namely an organic composition, and consists of a main catalyst, a catalyst framework and a carrier.

The catalyst composition used in the present invention is:

… … … … … 100ml of mono-cyclohexanone

Michler's ketone … … … … … 1g

Cinnamic acid … … … … … 1g

… 2g of polyvinyl alcohol cinnamate; or

… … … … … 100ml of di-cyclohexanone and … … … … … ml of cyclohexanone

2-hydroxy-5-nitroacenaphthylene … … 1.5.5 g

… … … … … 3g of polyester

Diaminodiphenyl ether … … … 0.5.5 g

Michler's ketone and cinnamic acid are both main catalysts for increasing SiO with the first catalyst composition₂The corrosion rate of (2). The cyclohexanone plays a role of fusing a main catalyst and a catalyst framework into a whole, and the polyvinyl alcohol cinnamate is the catalyst framework and has a good film forming effect; improve the corrosion uniformity and improve the activity of the main catalyst. In the second catalyst composition, 2-hydroxy-5-nitro acenaphthene and diaminodiphenyl ether are main catalysts, and polyester isA catalyst framework.

In the case of the first catalyst composition, Michler's ketone has the following structural formula:

michler's ketone has two basic groups and a carbonyl group which can form hydrogen bond with HF, and besides the hydrogen bond forms adsorption, the basic groups and HF react to form chemical bond, and the action energy (chemical bond) of the action is many times larger than that of the hydrogen bond, so that Michler's ketone has strong capability of adsorbing HF and plays a good role in catalytic corrosion.

The amount of HF adsorbed by different catalyst membranes is different along with the change of temperature, physical adsorption is carried out at room temperature, the adsorption amount of each catalyst is the same, and the chemical adsorption amount is increased along with the rise of temperature. Fig. 10 shows four catalysts, wherein e is polyvinyl alcohol cinnamate; f is 2-hydroxy-5-nitro acenaphthene, g is KPR glue, h is cyclized rubber, and it can be seen from FIG. 10 that the adsorption amount of 2-hydroxy-5-nitro acenaphthene as the main catalyst is larger than that of other catalysts on the solid surface at 100 ℃. As the temperature continues to rise, desorption occurs. The corrosion temperature adopted by the invention is between room temperature and 190 ℃.

The 2-hydroxy-5-nitro acenaphthene can generate four hydrogen bonds and has certain adsorption capacity to hydrogen fluoride.

The catalyst activity and the catalyst amount are closely related, and the thickness of the catalyst film means the difference of the catalyst amount, the thicker the film is, the more the main catalyst is, and fig. 11 shows the relationship of the adsorption amount of HF with the catalyst film thickness. In this figure, curve I represents michler's ketone, curve II represents polyvinyl alcohol cinnamate, curve III represents cyclohexanone, from which it can be seen that the activity is the strongest in curve I of the three catalysts. The catalyst film thickness of the present invention is from 200 to 2000a depending on the catalyst composition used.

Example 1

Oxidizing a layer of SiO in monocrystalline silicon by wet oxygen at 1050 deg.C or below₂With a thickness of 20-5 μm, an energy of 60KeV and a dose of 1 × 10 using conventional ion implantationequipment¹⁶cm^-2The selective injection is carried out, the catalyst film thickness is 800A by using the catalyst composition I of the invention, the temperature is 180 ℃, and the process is carried outAs shown in fig. 12. As a result, the etching rate ratio was 1: 102, and the resolution reached submicron, and an ion implantation micrograph (5 μm line width) after implantation using a stencil mask as shown in FIG. 13 was obtained.

Example 2

In a vacuum container with high-voltage power supply at both ends, the surface is SiO₂The silicon chip sample is put on the anode to be bombarded by electron beams, and the voltage of the two electrodes is 2 multiplied by 10³V, bombardment time is 5 minutes, the catalyst composition II of the invention is used, the thickness of the catalyst is 1000-degree, the temperature is 150 ℃, the process is the same as ion beam injection, the corrosion rate ratio is 1: 110, the resolution reaches submicron, and an etching graph photo using the hollow mask shown in figure 14 is obtained, and the line width is 15 mu m.

Example 3

To have SiO₂The silicon wafer on the surface of the film is subjected to plasma beam bombardment in a plasma chamber, and the process flow of the silicon wafer is the same as that of an ion beam and an electron beam, but the voltage of two electrodes is 1900V, the energy is 40W, and the time is 80 seconds.

Example 4

When the first time the SiO is caused to be present by means of an ion beam or electron beam₂The surface is given a resist effect and then bombarded with a plasma beam to restore it to its original state, even if its resist effect disappears. As shown in FIG. 15, the plasma beam power was 35W and the bombardment time was about 20 seconds. The submicron pattern wasproduced by this method and the etching result was shown in the scanning electron micrograph of FIG. 16.

Claims (3)

1. A beam induced erosion method, comprising the steps of:

the first step is as follows: ion beam, electron beam, plasma beam or two kinds of ion beam to SiO₂Surface is selectively bombarded to make SiO₂The surface energy is obviously changed, so that the corrosion rate ratio of a bombardment area to a non-bombardment area after corrosion in mixed gas of HF solution bubbling by nitrogen is obviously increased or recovered, and the ion of the used ion beam is N⁺、H⁺、O⁺、Ar⁺Ion implantationThe amount is 5X 10¹⁵cm^-2～1×10¹⁶cm^-2The energy is 10 KeV-100 KeV, the voltage of two electrodes used in electron beam bombardment is 1800V-2000V, and the bombardment time is more than 5 minutes; the energy used for the bombardment of the plasma beam is 20W-40W, and the bombardment time is 60 seconds-90 seconds;

the second step is that: coating a layer of a catalyst composition having a thickness of 200A to 2000A on the surface selectively bombarded by the particle beam, the catalyst composition comprising:

… … … … 100ml of mono-cyclohexanone

Michler's ketone … … … … 1g

Cinnamic acid … … … … 1g

… 2g of polyvinyl alcohol cinnamate; or

… … … … 100ml of di-cyclohexanone and … … … … ml of cyclohexanone

2-hydroxy-5-nitroacenaphthylene … 1.5.5 g

… … … … 3g of polyester

Diaminodiphenyl ether … … 0.5.5 g

The third step: on the sample coated with the catalyst composition film, under the room temperature to 190 ℃, the mixed gas of a nitrogen bubbling HF solution is used for corrosion, and the corrosion rate is more than 1000 a/min;

the fourth step: removing the catalyst to obtain the required pattern.

2. The beam-induced erosion method of claim 1, wherein: etching resistant SiO in first ion beam implantation₂On the surface, the second bombardment with electron beam or plasma beam is performed to make the corrosion resistance disappear.

3. The beam-induced erosion method of claim 1, wherein: SiO with corrosion resistance in the first bombardment with electron beam₂On the surface, the plasma beam is bombarded for the second time to make the corrosion resistance disappear.

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